Home Abstracts - 1

Modificado em 06 de Julho de 2012

 

 

 

Too little water or too much: hyponatremia due to excess fluid intake

Hyponatremia associated with diarrhea is usually caused by dehydration, with salt loss accompanying the excessive loss of water. On the other hand, hyponatremia in this setting can occasionally be caused by excess ingestion or administration of hypotonic fluids (1, 2). In this report, we describe the differential diagnosis of hyponatremia in an infant.

Hydration Status of Arabic Adolescents and Young Men: Measurement, Evaluation, and a School-based Initiative to Improve Drinking Behaviour.

BACKGROUND. Despite the importance of hydration, limited research has been undertaken in Arabic populations. METHODS: Study 1: 88 adult military cadets and 32 school-based adolescents provided five sequential daily mid-morning urine samples. Hydration thresholds were produced using percentiles of estimated urine osmolality (Uosm) and urine color (Ucol). Study 2: 120 military cadets and 52 adolescents provided 1077 mid-morning urine samples and the Uosm:Ucol relationship was assessed using regression. Study 3: 21 adolescents participated in a four-week hydration campaign, providing urine samples pre (PreC), at the end of (EndC) and two weeks post (PostC) campaign. RESULTS: Study 1: Euhydration (41-60th percentile) was 881-970 mOsmol·kg-1 (adults) and 821-900 mOsmol·kg-1 (adolescents). Study 2: In both cohorts, Uosm and Ucol were associated (p<0.01): adults R2=0.33; adolescents R2=0.59. Study 3: Urine osmolality was significantly higher PreC compared to EndC and PostC. CONCLUSIONS: Urinary output of Arabic adolescents and military cadets was more concentrated than frequently recommended for euhydration. Further work in similar populations is required to determine if these values represent hypohydration or merely reflect dietary and cultural differences. In Arabic adolescents and adults, Ucol was an adequate indicator of hydration status. Favorable hydration changes were made following a school-based health campaign.

Influence of Beverage Temperature on Palatability and Fluid Ingestion During Endurance Exercise: a systematic review.

BACKGROUND. Beverage palatability is known to influence fluid consumption during exercise and may positively influence hydration status and help to prevent fatigue, heat illness and decreased performance. PURPOSE: The aims of this review were to evaluate the effect of beverage temperature on fluid intake during exercise and investigate the influence of beverage temperature on palatability. METHODS: Citations from multiple databases were searched from the earliest record to November 2010 using the terms 'beverage', 'fluid' or 'water' and 'palatability', 'preference', 'feeding' and 'drinking behaviour' and 'temperature'. Included studies (n=13) needed to use adult (≥18yr) human participants, have beverage temperatures ≤50°C and measure consumption during exercise and/or palatability. RESULTS: All studies (n=8) reporting palatability indicated cold (0- 10°C) or cool (10-22°C) beverages were preferred to warmer (control, ≥22°C). A meta-analysis on studies (n=5) reporting fluid consumption revealed that participants consumed ~50% (effect size=1.4, 0.75 to 2.04, 95% CI) more cold/cool beverages than control during exercise. Sub-analysis of studies assessing hydration status (n=4) when consuming cool/cold compared to warm beverages demonstrated that dehydration during exercise was reduced by 1.3% of body weight (1.6 to 0.9%, 95% CI) (p<0.001). CONCLUSION: Cool beverage temperatures (<22°C) significantly increased fluid palatability, consumption and hydration during exercise compared to control (≥22°C).

Physical signs of dehydration in the elderly.

Objective Dehydration is a common condition and frequent cause of hospitalization in older people, despite the caregiver's high attention in attempt to avoid its occurrence. In this study, various physical signs were examined as clinical signs of dehydration in elderly. Methods A prospective observational study was conducted in an acute care teaching hospital. Consecutive elderly patients who were admitted to the Department of Medicine were evaluated. Dehydration was defined as a calculated serum osmolality above 295 mOsm/L. The patients diagnosed as dehydrated or not dehydrated were observed for physical signs of dehydration. Data of blood and urine chemistry analysis were also compared between the two groups. Results A total of 27 elderly patients admitted with acute medical conditions were included in this study. For the physical signs, dry axilla had moderate sensitivity (44%) and excellent specificity (89%) to detect dehydration. Sunken eyes and delayed capillary refill time also showed relatively good specificity (83%). For laboratory data, the mean concentrations of serum sodium of the dehydrated group (146 mEq/L) was significantly higher (p<0.01) than those of the non-dehydrated group (134 mEq/L). Conclusion Physical signs of dehydration in elderly showed relatively good specificity but poor sensitivity. The evaluation of the axillary moisture could help assess dehydration as well as laboratory data analysis such as serum sodium concentration. FREE FULL TEXT AVAILABLE IN PUBMED

Effects of hydration and water deprivation on blood viscosity during a soccer game in sickle cell trait carriers.

The present study compared the changes in blood viscosity, hydration status, body temperature and heart rate between a group of sickle cell trait (SCT) carriers and a control (Cont) group before and after a soccer game performed in two conditions: one with water offered ad libitum (hydration condition; Hyd) and the other one without water (dehydration condition; Dehyd). Blood viscosity and haematocrit per blood viscosity ratio (HVR; an index of red blood cell oxygen transport effectiveness) were measured before and at the end of each game. Resting blood viscosity was greater in the SCT carriers than in the Cont group. The increase of blood viscosity over baseline at the end of the game in the Cont group was similar in the two conditions. In contrast, the change in blood viscosity occurring in SCT carriers during soccer games was dependant on the experimental condition: (1) in Dehyd condition, blood viscosity rose over baseline; (2) in Hyd condition, blood viscosity decreased below resting level reaching Cont values. The Cont group had higher HVR than SCT carriers at rest. HVR remained unchanged in the Cont group at the end of the games, whatever the experimental condition. Although HVR of SCT carriers decreased below baseline at the end of the game performed in Dehyd condition, it increased over resting level in Hyd condition reaching the values of the Cont group. Our study demonstrated that ad libitum hydration in exercising SCT carriers normalises the blood hyperviscosity.

Dysphagia, Nutrition, and Hydration in Ischemic Stroke Patients at Admission and Discharge from Acute Care.

Dysphagia may predispose stroke patients toward undernutrition and hydration. These comorbidities increase patient risks for reduced functional outcome and short-term mortality. Despite this impact, available information on relationships among dysphagia, nutrition, and hydration status in acute stroke is limited and conflicted. This study evaluated nutrition and hydration status in ischemic stroke patients with versus without clinically significant dysphagia at admission and at discharge from acute care. Sixty-seven patients admitted to the stroke unit in a tertiary-care hospital provided data for this study. On the day of hospital admission and upon discharge or at 7 days post admission, serum biochemical measures were obtained for nutrition (prealbumin) and hydration status (BUN/Cr). Clinical evaluation for dysphagia, nutrition status, and stroke severity were completed an average of 1.4 days following hospital admission. Dysphagia was identified in 37 % of the cohort. At admission 32 % of patients demonstrated malnutrition based on prealbumin levels and 53 % demonstrated evidence of dehydration based on BUN/Cr levels. No differences in nutrition status were attributed to dysphagia. Patients with dysphagia demonstrated significantly higher BUN/Cr levels (greater dehydration) than patients without dysphagia at admission and at discharge. Dehydration at both admission and discharge was associated with dysphagia, clinical nutrition status, and stroke severity. Results of this study support prior results indicating that dysphagia is not associated with poor nutrition status during the first week post stroke. Dehydration status is associated with dysphagia during this period. The results have implications for future confirmatory research and for clinical management of dysphagia in the acute stroke period.

French children start their school day with a hydration deficit.

Background and Aims: Fluid requirements of children vary as a function of gender and age. To our knowledge, there is very little literature on the hydration status of French children. We assessed the morning hydration status in a large sample of 529 French schoolchildren aged 9-11 years. Methods: Recruited children completed a questionnaire on fluid and food intake at breakfast and collected a urine sample the very same day after breakfast. Breakfast food and fluid nutritional composition was analyzed and urine osmolality was measured using a cryoscopic osmometer. Results: More than a third of the children had a urine osmolality between 801 and 1,000 mosm/kg while 22.7% had a urine osmolality over 1,000 mosm/kg. This was more frequent in boys than in girls (p < 0.001). A majority of children (73.5%) drank less than 400 ml at breakfast. Total water intake at breakfast was significantly and inversely correlated with high osmolality values. Conclusions: Almost two thirds of the children in this large cohort had evidence of a hydration deficit when they went to school in the morning, despite breakfast intake. Children's fluid intake at breakfast does not suffice to maintain an adequate hydration status for the whole morning.

Body weight changes in child and adolescent athletes during a triathlon competition.

We examined young athletes during a triathlon performed in a hot climate. Complete or partial data were available for 95 athletes competing in the National Triathlon Championship in Costa Rica. Mean ± SD for age and body weight (BW) were 13.1 ± 2.5 years and 46.3 ± 11.5 kg, respectively. Race requirements included: 500 m swimming, 15 km cycling, 3.5 km running for juniors (9-13 years); 800 m swimming, 30 km cycling, 8 km running for seniors (14-17 years). WBGT on race day was >31 °C. BW recorded pre- and post-race was available for 92 athletes and performance data were available for 83 of these. Information regarding symptoms experienced during the race was available for 95 athletes. Change in BW (%ΔBW) was calculated and ranged from +0.6 to -2.4 % for junior boys (-1.2 ± 0.9 %), +0.7 to -2.5 % for junior girls (-1.3 ± 0.9 %), 0 to -2.8 % for senior girls (-1.3 ± 0.9 %), and +0.6 to -4.5 % for senior boys (-1.7 ± 1.1 %). Eighteen participants reported no medical symptoms. Of 77 participants who reported symptoms, 42.9 % reported exhaustion/fatigue, 36.4 % reported side stitch/cramp, and 23.4 % reported dizziness. Participants reporting no medical symptoms achieved almost identical (P = 0.99) %ΔBW as those reporting at least one symptom. %ΔBW was more negative (P = 0.005) in participants who reported dizziness (-1.9 %ΔBW) compared with those who did not (-1.4 %ΔBW). %ΔBW was associated with performance in junior girls (r = 0.47, P = 0.02) and senior boys (r = 0.51, P = 0.01), with a trend in junior boys (r = 0.41, P = 0.053) but not in senior girls (r = 0.004, P = 0.99). Young athletes participating in a triathlon in a hot climate can tolerate mild to moderate levels of dehydration, without detrimental effects to self-assessed health.

Analysis of dehydration and strength in elite badminton players.

BACKGROUND. The negative effects of dehydration on aerobic activities are well established. However, it is unknown how dehydration affects intermittent sports performance. The purpose of this study was to identify the level of dehydration in elite badminton players and its relation to muscle strength and power production. METHODOLOGY: Seventy matches from the National Spanish badminton championship were analyzed (46 men's singles and 24 women's singles). Before and after each match, jump height and power production were determined during a countermovement jump on a force platform. Participants' body weight and a urine sample were also obtained before and after each match. The amount of liquid that the players drank during the match was also calculated by weighing their individual drinking bottles. RESULTS AND DISCUSSION: Sweat rate during the game was 1.14±0.46 l/h in men and 1.02±0.64 l/h in women. The players rehydrated at a rate of 1.10±0.55 l/h and 1.01±0.44 l/h in the male and female groups respectively. Thus, the dehydration attained during the game was only 0.37±0.50% in men and 0.32±0.83% in women. No differences were found in any of the parameters analyzed during the vertical jump (men: from 31.82±5.29 to 32.90±4.49 W/kg; p>0.05, women: from 26.36±4.73 to 27.25±4.44 W/kg; p>0.05). Post-exercise urine samples revealed proteinuria (60.9% of cases in men and 66.7% in women), leukocyturia (men = 43.5% and women = 50.0%) and erythrocyturia (men = 50.0% and women = 21.7%). CONCLUSIONS: Despite a moderate sweat rate, badminton players adequately hydrated during a game and thus the dehydration attained was low. The badminton match did not cause muscle fatigue but it significantly increased the prevalence of proteinuria, leukocyturia and erythrocyturia. FREE FULL TEXT IN PUBMED.

Bioelectrical impedance analysis in the assessment of hydration status in peritoneal dialysis patients.

Objective: Assessment of fluid status in chronic peritoneal dialysis (PD) patients is complex. Clinical evaluation based solely on body weight, blood pressure, volume of ultrafiltration (UF) and peripheral edema is insufficient. A non-invasive test, bioelectrical impedance analysis (BIA) might be of potential benefit. Aim: To test whether BIA correlates with other ancillary markers of extracellular fluid volume, namely B-type natriuretic peptide (BNP), residual renal function (RRF) and UF, and whether BIA provides complementary information in categorizing PD patients vis-à-vis hydration status. Methods: A cross-sectional study of 61 out-patients on chronic PD. Single-frequency BIA measurements of resistance/height were divided into tertiles (lowest: 253 Ω/m and 316 Ω/m). Results: Compared to patients in the highest tertile of BIA (least fluid), patients in the lowest tertile (most fluid) had highest BNP, RRF and UF (93.5 vs. 55.0 pg/ml, p = 0.029; 850 vs. 300 ml/day, p = 0.05; and 1.75 vs. 1.21 l/day, p = 0.023, respectively). Conclusions: BIA tertiles categorized PD patients who differed in BNP, RRF and UF in a stepwise pattern, suggesting BIA may better inform hydration status, and serve as an additional clinical tool in management of chronic PD patients.

Assessment of fluid status in peritoneal dialysis.

Fluid management is recognized as a basic component of management of patients on dialysis. Fluid overload is an important adverse factor in patient outcomes, and the negative effects of fluid depletion, including on residual renal function, are aIso increasingly being recognized. The complexities of fluid distribution in renal failure need to be understood to inform assessment of hydration. Clinical assessment of hydration is insensitive to abnormalities in hydration. BIA is the most promising technique for objective assessment of fluid status, but it is essential that the underlying principles and limitations are understood, and that results from BIA are utilized in conjunction with clinical assessment rather than in isolation.

Hydration Status, Fluid Intake and Electrolyte Losses in Youth Soccer Players

The purpose of the study was to determine the hydration status, fluid intake and electrolyte losses of 21 male professional youth soccer players (age 17.1 ± 0.7 yr) training in a cool environment. Pre- and post training measurements of body mass, urine (freezing point osmolality method) and sweat concentration (flame emission spectroscopy) were collected. Fourteen players were found to be hypohydrated prior to training. The amount of fluid lost due to exercise equated to a 1.7 % loss in body mass, which equated to a gross dehydration loss of 0.5 %. Overall, the soccer players replaced 46 ¬± 88% of sweat loss during training and only four remained hypohydrated after training. No significant correlations between sweat loss and sweat concentrations of Na+ (r = -0.11, P = 0.67), K+ (r = 0.14, P = 0.58) were found, but there was a significant correlation with Mg2+ (r = -0.58, P < 0.009). This study found large variability in pre-training hydrationstatus which the players were able to rehydrate during the training sessions.However, given the numbers starting training in a hypohydrated state, adequate hydration status prior to training should be considered by youth players, coaches and sports science support staff.

Symptoms of heat illness in surface mine workers.

OBJECTIVE: To assess the symptoms of heat illness experienced by surface mine workers. METHODS: Ninety-one surface mine workers across three mine sites in northern Australia completed a heat stress questionnaire evaluating their symptoms for heat illness. A cohort of 56 underground mine workers also participated for comparative purposes. Participants were allocated into asymptomatic, minor or moderate heat illness categories depending on the number of symptoms they reported. Participants also reported the frequency of symptom experience, as well as their hydration status (average urine colour). RESULTS: Heat illness symptoms were experienced by 87 and 79 % of surface and underground mine workers, respectively (p = 0.189), with 81-82 % of the symptoms reported being experienced by miners on more than one occasion. The majority (56 %) of surface workers were classified as experiencing minor heat illness symptoms, with a further 31 % classed as moderate; 13 % were asymptomatic. A similar distribution of heat illness classification was observed among underground miners (p = 0.420). Only 29 % of surface miners were considered well hydrated, with 61 % minimally dehydrated and 10 % significantly dehydrated, proportions that were similar among underground miners (p = 0.186). Heat illness category was significantly related to hydration status (p = 0.039) among surface mine workers, but only a trend was observed when data from surface and underground miners was pooled (p = 0.073). Compared to asymptomatic surface mine workers, the relative risk of experiencing minor and moderate symptoms of heat illness was 1.5 and 1.6, respectively, when minimally dehydrated. CONCLUSIONS: These findings show that surface mine workers routinely experience symptoms of heat illness and highlight that control measures are required to prevent symptoms progressing to medical cases of heat exhaustion or heat stroke.

Nurse-physician communication concerning artificial nutrition or hydration (ANH) in patients with dementia: a qualitative study.

Aims and objectives. To explore nurses' experiences with nurse-physician communication during artificial nutrition or hydration (ANH) decision-making in hospitalised patients with dementia. Background.  Artificial nutrition or hydration decision-making often occurs in patients with dementia. Effective communication between professionals is extremely challenging in this population, because these patients are unable to communicate their treatment wishes. Design.  Qualitative interview design. Methods.  Between April 2008 and June 2009, we conducted 21 interviews with nurses from nine different hospitals geographically spread throughout Flanders (Belgium). Interviews were audiotaped and later transcribed. Data processing involved (1) simultaneous and systematic data collection and analysis, (2) constant forwards-backwards wave, (3) continuous dialogue with the data and (4) interactive team processes. Results.  The interviews showed that communication with physicians is the central instrument the nurses used in their attempts to realise their perception of 'the best possible care'. From the nurses' perspective, we distinguished three mutually connected factors that affected the effectiveness of nurse-physician communication during artificial nutrition or hydration decision-making: the physicians' attitude towards the nurses, the nurses' attitude towards the physicians and the forms of communication used by the nurses. The complex interaction between these three factors resulted in a range of nurses' perceptions, varying from positive to negative. The direction of their perceptions depended on the extent to which they succeeded or failed to use nurse-physician communication as an instrument to realise the 'best care'. Conclusion.  Nurse-physician communication was the most important instrument determining whether nurses succeeded or failed to actively act as a patient's representative and whether nurses achieved the best possible care in co-operation with physicians. Relevance to clinical practice. To reach optimal care and nurse job satisfaction, nurse-physician communication during artificial nutrition or hydration decision-making should be an open dialogue characterised by mutual respect and understanding.

Hydration, sweat and thermoregulatory responses to professional football training in the heat.

This study examined the relationship between intensity of training and changes in hydration status, core temperature, sweat rate and composition and fluid balance in professional football players training in the heat. Thirteen professional football players completed three training sessions; "higher-intensity" (140 min; HI(140)), "lower-intensity" (120 min; LI(120)) and "game-simulation" (100 min; GS(100)). Movement demands were measured by Global Positioning System, sweat rate and concentration were determined from dermal patches and body mass change. Despite similar environmental conditions (26.9 ± 0.1°C and 65.0 ± 7.0% relative humidity [Rh]), higher relative speeds (m · min(-1)) and increased perceptions of effort and thermal strain were observed in HI(140) and GS(100) compared with LI(120) (P < 0.05). Significantly (P < 0.05) greater sweat rate (L · h(-1)) and electrolyte losses (g) were observed in HI(140) and GS(100) compared with LI(120). Rate of rise in core temperature was correlated with mean speed (r = 0.85), session rating of perceived exertion (sRPE) (r = 0.61), loss of potassium (K(+)) (r = 0.51) sweat rate (r = 0.49), and total sweat loss (r = 0.53), with mean speed the strongest predictor. Sodium (Na(+)) (r = 0.39) and K(+) (r = 0.50) losses were associated with total distance covered. In hot conditions, individualised rehydration practices should be adopted following football training to account for differences in sweat rate and electrolyte losses in response to intensity and overall activity within a session.

Hypertonic Saline and Acute Wheezing in Preschool Children.

BACKGROUND: Most acute wheezing episodes in preschool children are associated with rhinovirus. Rhinovirus decreases extracellular adenosine triphosphate levels, leading to airway surface liquid dehydration. This, along with submucosal edema, mucus plaques, and inflammation, causes failure of mucus clearance. These preschool children do not respond well to available treatments, even oral steroids. This calls for pro-mucus clearance and prohydration treatments such as hypertonic saline in wheezing preschool children. METHODS: Randomized, controlled, double-blind study. Forty-one children (mean age 31.9 ± 17.4 months, range 1-6 years) presented with wheezing to the emergency department were randomized after 1 albuterol inhalation to receive either 4 mL of hypertonic saline 5% (HS) (n = 16) or 4 mL of normal saline (NS) (n = 25), both with 0.5 mL albuterol, twice every 20 minutes in the emergency department and 4 times a day thereafter if hospitalized. The primary outcome measured was length of stay (LOS) and the secondary outcomes were admission rate (AR) and clinical severity score. RESULTS: The LOS was significantly shorter in the HS than in the NS group: median 2 days (range 0-6) versus 3 days (range 0-5) days (P = .027). The AR was significantly lower in the HS than the NS group: 62.2% versus 92%. Clinical severity score improved significantly in both groups but did not reach significance between them. CONCLUSIONS: Using HS inhalations significantly shortens LOS and lowers AR in preschool children presenting with an acute wheezing episode to the emergency department.

Body Mass Change and Ultraendurance Performance: A Decrease in Body Mass Is Associated With an Increased Running Speed in Male 100-km Ultramarathoners.

Body mass change and ultraendurance performance: a decrease in body mass is associated with an increased running speed in male 100-km ultramarathoners. J Strength Cond Res 26(6): 1505-1516, 2012-We investigated, in 50 recreational male ultrarunners, the changes in body mass, selected hematological and urine parameters, and fluid intake during a 100-km ultramarathon. The athletes lost (mean and SD) 2.6 (1.8) % in body mass (p < 0.0001). Running speed was significantly and negatively related to the change in body mass (p < 0.05). Serum sodium concentration ([Na]) and the concentration of aldosterone increased with increasing loss in body mass (p < 0.05). Urine-specific gravity increased (p 2% in body mass leads to dehydration and consequently impairs endurance performance must be questioned for ultraendurance athletes competing in the field. For practical applications, a loss in body mass during a 100-km ultramarathon was associated with a faster running speed.

Hydration and performance during Ramadan.

In the absence of any food or fluid intake during the hours of daylight during the month of Ramadan, a progressive loss of body water will occur over the course of each day, though these losses can be completely replaced each night. Large body water deficits will impair both physical and cognitive performance. The point at which water loss will begin to affect performance is not well defined, but it may be as little as 1-2% of body mass. For resting individuals in a temperate environment, the water loss that occurs during a day without food or fluid will typically amount to about 1% of body mass by the time of sunset. This small loss of body water is unlikely to have a major adverse effect on any aspect of physical or cognitive performance. Larger body water losses will occur, however, in hot weather or if exercise is undertaken. Performance in events lasting about 1 hour or longer may be impaired in the absence of fluid intake during the event. In weight-category sports, there may be difficulties due to the impossibility of restoring body water content between the weigh-in and competition, and athletes will require alternative strategies. Where more than one competition or training session takes place in a single day and where substantial fluid losses are incurred, recovery will be impaired by the absence of fluid intake.

Promoting and maintaining healthy hydration in patients.

Fluid is essential for life and health. Nurses have an important role in helping patients maintain optimal levels of hydration, particularly in hospital or residential settings where access to fluid is less likely to be under the patient's control. This article describes the benefits of healthy hydration, outlines guidelines on fluid requirements for different patient groups and discusses which beverages should be promoted. Myths about caffeine consumption and hydration will also be addressed using new clinical evidence.

Effects of rehydration fluid temperature and composition on body weight retention upon voluntary drinking following exercise-induced dehydration.

The purpose of this study was to determine the effects of beverage temperature and composition on weight retention and fluid balance upon voluntary drinking following exercise induced-dehydration. Eight men who were not acclimated to heat participated in four randomly ordered testing sessions. In each session, the subjects ran on a treadmill in a chamber maintained at 37℃ without being supplied fluids until 2% body weight reduction was reached. After termination of exercise, they recovered for 90 min under ambient air conditions and received one of the following four test beverages: 10℃ water (10W), 10℃ sports drink (10S), 26℃ water (26W), and 26℃ sports drink (26S). They consumed the beverages ad libitum. The volume of beverage consumed and body weight were measured at 30, 60, and 90 min post-recovery. Blood samples were taken before and immediately after exercise as well as at the end of recovery in order to measure plasma parameters and electrolyte concentrations. We found that mean body weight decreased by 1.8-2.0% following exercise. No differences in mean arterial pressure, plasma volume, plasma osmolality, and blood electrolytes were observed among the conditions. Total beverage volumes consumed were 1,164 ± 388, 1,505 ± 614, 948 ± 297, and 1,239 ± 401 ml for 10W, 10S, 26W, and 26S respectively (P > 0.05). Weight retention at the end of recovery from dehydration was highest in 10S (1.3 ± 0.7 kg) compared to 10W (0.4 ± 0.5 kg), 26W (0.4 ± 0.4 kg), and (0.6 ± 0.4 kg) (P < 0.005). Based on these results, carbohydrate/electrolyte-containing beverages at cool temperature were the most favorable for consumption and weight retention compared to plain water and moderate temperature beverages. FREE FULL-TEXT AVAILABLE IN PUBMED.

Water intake and post-exercise cognitive performance: an observational study of long-distance walkers and runners.

PURPOSE: The impact of diet on endurance performance and cognitive function has been extensively researched in controlled settings, but there are limited observational data in field situations. This study examines relationships between nutrient intake and cognitive function following endurance exercise amongst a group of 33 recreational runners and walkers. METHODS: All participants (mean age of 43.2 years) took part in a long-distance walking event and completed diet diaries to estimate nutrient intake across three-time periods (previous day, breakfast and during the event). Anthropometric measurements were recorded. Cognitive tests, covering word recall, ruler drop and trail making tests (TMT) A and B were conducted pre- and post-exercise. Participants rated their exercise level on a validated scale. Nutrient intake data were summarised using principal components analysis to identify a nutrient intake pattern loaded towards water intake across all time periods. Regression analysis was used to ascertain relationships between water intake component scores and post-exercise cognitive function, controlling for anthropometric measures and exercise metrics (distance, duration and pace). RESULTS: Participants rated their exercise as 'hard-heavy' (score 14.4, ±3.2). Scores on the water intake factor were associated with significantly faster TMT A (p = 0.001) and TMT B (p = 0.005) completion times, and a tendency for improved short-term memory (p = 0.090). Water intake scores were not associated with simple reaction time (assessed via the ruler drop test). CONCLUSION: These data are congruent with experimental research demonstrating a benefit of hydration on cognitive function. Further field research to confirm this relationship, supported with precise measures of body weight, is needed.

Body composition and hydration status changes in male and female open-water swimmers during an ultra-endurance event.

Body mass changes during ultra-endurance performances have been described for running, cycling and for swimming in a heated pool. The present field study of 20 male and 11 female open-water swimmers investigated the changes in body composition and hydration status during an ultra-endurance event. Body mass, both estimated fat mass and skeletal muscle mass, haematocrit, plasma sodium concentration ([Na(+)]) and urine specific gravity were determined. Energy intake, energy expenditure and fluid intake were estimated. Males experienced significant reductions in body mass (-0.5 %) and skeletal muscle mass (-1.1 %) (P 0.05). Changes in percent body fat, fat mass, and fat-free mass were heterogeneous and did not reach statistical significance (P > 0.05) between gender groups. Fluid intake relative to plasma volume was higher in females than in males during the ultra-endurance event. Compared to males, females' average increase in haematocrit was 3.3 percentage points (pp) higher, urine specific gravity decrease 0.1 pp smaller, and plasma [Na(+)] 1.3 pp higher. The observed patterns of fluid intake, changes in plasma volume, urine specific gravity, and plasma [Na(+)] suggest that, particularly in females, a combination of fluid shift from blood vessels to interstitial tissue, facilitated by skeletal muscle damage, as well as exercise-associated hyponatremia had occurred. To summarise, changes in body composition and hydration status are different in male compared to female open-water ultra-endurance swimmers.

The effects of dehydration during cycling on skeletal muscle metabolism in females.

INTRODUCTION: This study investigated the effects of progressive dehydration on the time course of changes to whole body substrate oxidation and skeletal muscle metabolism during 120 min of cycling in hydrated females. METHODS: Subjects (n=9) cycled for 120 min at ∼65% VO2peak on two occasions: with no fluid (DEH) and with fluid replacement to match sweat losses (HYD). Venous blood samples were taken at rest and every 20 min and muscle biopsies taken at 0, 60 and 120 min of exercise. RESULTS: DEH subjects lost 0.9% body mass (BM) from 0-60 min and 1.1% from 60-120 min (2.0% total). HR and Tc were significantly greater from 30-120 min, Pvol loss from 40-120 min, and RPE from 60-120 min in the DEH trial. There were no differences in VO2 or sweat loss between trials. RER (HYD 0.85 ± 0.01 vs. DEH 0.87 ± 0.01) and total carbohydrate (CHO) oxidation (175 ± 17 vs. 191 ± 17g) were higher in the DEH trial. Blood [La] was significantly higher in the DEH trial with no change in plasma free fatty acid and epinephrine concentrations. Muscle glycogenolysis was 31% greater in the DEH trial (252 ± 49 vs. 330 ± 33 mmol/kg dm) and muscle [La] was also higher at 60 min. CONCLUSION: Progressive dehydration significantly increased HR, Tc, RPE, Pvol loss, whole body CHO oxidation, and muscle glycogenolysis, and these changes were already apparent in the first hour of exercise when BM losses were ≤1%. The increased muscle glycogenolysis with DEH appeared to be due to increased core and muscle temperature, secondary to less efficient movement of heat from the core to the periphery.

Medical sports injuries in the youth athlete: emergency management.

As the number of youth sports participants continues to rise over the past decade, so too have sports related injuries and emergency department visits. With low levels of oversight and regulation observed in youth sports, the responsibility for safety education of coaches, parents, law makers, organizations and institutions falls largely on the sports medicine practitioner. The highly publicized catastrophic events of concussion, sudden cardiac death, and heat related illness have moved these topics to the forefront of sports medicine discussions. Updated guidelines for concussion in youth athletes call for a more conservative approach to management in both the acute and return to sport phases. Athletes younger than eighteen suspected of having a concussion are no longer allowed to return to play on the same day. Reducing the risk of sudden cardiac death in the young athlete is a multi-factorial process encompassing pre-participation screenings, proper use of safety equipment, proper rules and regulations, and immediate access to Automated External Defibrillators (AED) as corner stones. Susceptibility to heat related illness for youth athletes is no longer viewed as rooted in physiologic variations from adults, but instead, as the result of various situations and conditions in which participation takes place. Hydration before, during and after strenuous exercise in a high heat stress environment is of significant importance. Knowledge of identification, management and risk reduction in emergency medical conditions of the young athlete positions the sports physical therapist as an effective provider, advocate and resource for safety in youth sports participation. This manuscript provides the basis for management of 3 major youth emergency sports medicine conditions. FREE FULL-TEXT AVAILABLE IN PUBMED.

Evaluation of a clinical dehydration scale in children requiring intravenous rehydration.

OBJECTIVES: To evaluate the reliability and validity of a previously derived clinical dehydration scale (CDS) in a cohort of children with gastroenteritis and evidence of dehydration. METHODS: Participants were 226 children older than 3 months who presented to a tertiary care emergency department and required intravenous rehydration. Reliability was assessed at treatment initiation, by comparing the scores assigned independently by a trained research nurse and a physician. Validity was assessed by using parameters reflective of disease severity: weight gain, baseline laboratory results, willingness of the physician to discharge the patient, hospitalization, and length of stay. RESULTS: Interobserver reliability was moderate, with a weighted κ of 0.52 (95% confidence interval [CI] 0.41, 0.63). There was no correlation between CDS score and percent weight gain, a proxy measure of fluid deficit (Spearman correlation coefficient = -0.03; 95% CI -0.18, 0.12). There were, however, modest and statistically significant correlations between CDS score and several other parameters, including serum bicarbonate (Pearson correlation coefficient = -0.35; 95% CI -0.46, -0.22) and length of stay (Pearson correlation coefficient = 0.24; 95% CI 0.11, 0.36). The scale's discriminative ability was assessed for the outcome of hospitalization, yielding an area under the receiver operating characteristic curve of 0.65 (95% CI 0.57, 0.73). CONCLUSIONS: In children administered intravenous rehydration, the CDS was characterized by moderate interobserver reliability and weak associations with objective measures of disease severity. These data do not support its use as a tool to dictate the need for intravenous rehydration or to predict clinical course.

Pilot study: Effects of drinking hydrogen-rich water on muscle fatigue caused by acute exercise in elite athletes.

BACKGROUND: Muscle contraction during short intervals of intense exercise causes oxidative stress, which can play a role in the development of overtraining symptoms, including increased fatigue, resulting in muscle microinjury or inflammation. Recently it has been said that hydrogen can function as antioxidant, so we investigated the effect of hydrogen-rich water (HW) on oxidative stress and muscle fatigue in response to acute exercise. METHODS: Ten male soccer players aged 20.9 +/- 1.3 years old were subjected to exercise tests and blood sampling. Each subject was examined twice in a crossover double-blind manner; they were given either HW or placebo water (PW) for one week intervals. Subjects were requested to use a cycle ergometer at a 75 % maximal oxygen uptake (VO2) for 30 min, followed by measurement of peak torque and muscle activity throughout 100 repetitions of maximal isokinetic knee extension. Oxidative stress markers and creatine kinase in the peripheral blood were sequentially measured. RESULTS: Although acute exercise resulted in an increase in blood lactate levels in the subjects given PW, oral intake of HW prevented an elevation of blood lactate during heavy exercise. Peak torque of PW significantly decreased during maximal isokinetic knee extension, suggesting muscle fatigue, but peak torque of HW didn't decrease at early phase. There was no significant change in blood oxidative injury markers (d-ROMs and BAP) or creatine kinease after exercise. CONCLUSION: Adequate hydration with hydrogen-rich water pre-exercise reduced blood lactate levels and improved exercise-induced decline of muscle function. Although further studies to elucidate the exact mechanisms and the benefits are needed to be confirmed in larger series of studies, these preliminary results may suggest that HW may be suitable hydration for athletes. FREE FULL-TEXT IN PUBMED.

Older persons and heat-susceptibility: the role of health promotion in a changing climate.

ISSUE ADDRESSED: Many studies world wide have provided evidence that older persons are a sub-population at increased risk of heat-related morbidity and mortality. This article gives an overview of the current state of knowledge of risk factors and provides commentary on the role of health promotion in the prevention of a climate change-related increase in elderly heat casualties. METHODS: A search of peer-reviewed medical and epidemiological literature and community health websites was conducted in order to gain an in-depth understanding of heat-susceptibility in the elderly and preventive strategies. Key search words included: elderly, aged, older, heat, thermoregulation, heat wave, mortality, heat effects, dehydration, heat-related illness, adaptation, adaptive capacity. RESULTS: The reasons underlying reduced heat tolerance in this group are multi-faceted, comprising physiological, social and behavioural limitations, with comorbidities and polypharmacy being contributing factors. Additionally, some older persons may be unable or reluctant to undertake adaptations necessary to maintain thermal homeostasis due to diminished awareness of the heat, lowered thirst sensation, mobility or cognitive impairments, a lowered perception of risk, or economic concerns. CONCLUSION: With older persons in poor health being particularly vulnerable to heat, preventive messages need to promote protective behaviours and help build resilience as temperatures rise.

Influence of skin type, race, sex, and anatomic location on epidermal barrier function.

The intact skin represents a barrier to the uncontrolled loss of water, proteins, and plasma components from the organism. Owing to its complex structure, the epidermal barrier with its major layer, the stratum corneum, is the rate-limiting unit for the penetration of exogenous substances through the skin. The epidermal barrier is not a static structure. The status of different functions of the epidermis can be monitored by assessing specific biophysical parameters such as transepidermal water loss, stratum corneum hydration, and skin surface pH. Variables originating from the individual as well as exogenous factors have an important influence on the epidermal barrier parameters.

Medical sports injuries in the youth athlete: emergency management.

As the number of youth sports participants continues to rise over the past decade, so too have sports related injuries and emergency department visits. With low levels of oversight and regulation observed in youth sports, the responsibility for safety education of coaches, parents, law makers, organizations and institutions falls largely on the sports medicine practitioner. The highly publicized catastrophic events of concussion, sudden cardiac death, and heat related illness have moved these topics to the forefront of sports medicine discussions. Updated guidelines for concussion in youth athletes call for a more conservative approach to management in both the acute and return to sport phases. Athletes younger than eighteen suspected of having a concussion are no longer allowed to return to play on the same day. Reducing the risk of sudden cardiac death in the young athlete is a multi-factorial process encompassing pre-participation screenings, proper use of safety equipment, proper rules and regulations, and immediate access to Automated External Defibrillators (AED) as corner stones. Susceptibility to heat related illness for youth athletes is no longer viewed as rooted in physiologic variations from adults, but instead, as the result of various situations and conditions in which participation takes place. Hydration before, during and after strenuous exercise in a high heat stress environment is of significant importance. Knowledge of identification, management and risk reduction in emergency medical conditions of the young athlete positions the sports physical therapist as an effective provider, advocate and resource for safety in youth sports participation. This manuscript provides the basis for management of 3 major youth emergency sports medicine conditions.

"Pilot study: Effects of drinking hydrogen-rich water on muscle fatigue caused by acute exercise in elite athletes."

"BACKGROUND: Muscle contraction during short intervals of intense exercise causes oxidative stress, which can play a role in the development of overtraining symptoms, including increased fatigue, resulting in muscle microinjury or inflammation. Recently it has been said that hydrogen can function as antioxidant, so we investigated the effect of hydrogen-rich water (HW) on oxidative stress and muscle fatigue in response to acute exercise. METHODS: Ten male soccer players aged 20.9 +/- 1.3 years old were subjected to exercise tests and blood sampling. Each subject was examined twice in a crossover double-blind manner; they were given either HW or placebo water (PW) for one week intervals. Subjects were requested to use a cycle ergometer at a 75 % maximal oxygen uptake (VO2) for 30 min, followed by measurement of peak torque and muscle activity throughout 100 repetitions of maximal isokinetic knee extension. Oxidative stress markers and creatine kinase in the peripheral blood were sequentially measured. RESULTS:\nAlthough acute exercise resulted in an increase in blood lactate levels in the subjects given PW, oral intake of HW prevented an elevation of blood lactate during heavy exercise. Peak torque of PW significantly decreased during maximal isokinetic knee extension, suggesting muscle fatigue, but peak torque of HW didn't decrease at early phase. There was no significant change in blood oxidative injury markers (d-ROMs and BAP) or creatine kinease after exercise. CONCLUSION:\nAdequate hydration with hydrogen-rich water pre-exercise reduced blood lactate levels and improved exercise-induced decline of muscle function. Although further studies to elucidate the exact mechanisms and the benefits are needed to be confirmed in larger series of studies, these preliminary results may suggest that HW may be suitable hydration for athletes. FULL--TEXT AVAILABLE IN PUBMED."\n

"Skeletal Muscle Strength and Endurance are Maintained during Moderate Dehydration. "

This study investigated the effects of moderate dehydration (~2.5% body weight) on muscle strength and endurance using percutaneous electrical stimulation to quantify central and peripheral fatigue, and isolate the combined effects of exercise-heat stress and dehydration, vs. the effect of dehydration alone. Force production and voluntary activation were calculated in 10 males during 1 brief and 15 repeated maximal voluntary isometric contractions performed prior to (control) walking in the heat (35°C), immediately following exercise, and the next morning (dehydration). The protocol was also performed in a euhydrated state. During the brief contractions, force production and voluntary activation were maintained in all trials. In contrast, force production decreased throughout the repeated contractions, regardless of hydration status (P<0.001). The decline in force was greater immediately following exercise-heat stress dehydration compared with control and euhydration (P<0.001). When dehydration was isolated from acute post-exercise dehydration, force production was maintained similarly to control and euhydration. Despite the progressive decline in force production and the increased fatigability observed during the repeated contractions, voluntary activation remained elevated throughout each muscle function test. Therefore, moderate dehydration, isolated from acute exercise-heat stress, does not appear to influence strength during a single contraction or enhance fatigability.

Sports nutrition knowledge among collegiate athletes, coaches, athletic trainers, and strength and conditioning specialists.

CONTEXT: Coaches, athletic trainers (ATs), strength and conditioning specialists (SCSs), and registered dietitians are common nutrition resources for athletes, but coaches, ATs, and SCSs might offer only limited nutrition information. Little research exists about sports nutrition knowledge and current available resources for nutrition information for athletes, coaches, ATs, and SCSs. OBJECTIVE: To identify resources of nutrition information that athletes, coaches, ATs, and SCSs use; to examine nutrition knowledge among athletes, coaches, ATs, and SCSs; and to determine confidence levels in the correctness of nutrition knowledge questions within all groups. DESIGN: Cross-sectional study. SETTING: National Collegiate Athletic Association Division I, II, and III institutions across the United States. Patients and Other Participants: The 579 participants consisted of athletes (n = 185), coaches (n = 131), ATs (n = 192), and SCSs (n = 71). Main Outcome Measure(s): Participants answered questions about nutrition resources and domains regarding basic nutrition, supplements and performance, weight management, and hydration. Adequate sports nutrition knowledge was defined as an overall score of 75% in all domains (highest achievable score was 100%). RESULTS: Participants averaged 68.5% in all domains. The ATs (77.8%) and SCSs (81.6%) had the highest average scores. Adequate knowledge was found in 35.9% of coaches, 71.4% of ATs, 83.1% of SCSs, and only 9% of athletes. The most used nutrition resources for coaches, ATs, and SCSs were registered dietitians. CONCLUSIONS: Overall, we demonstrated that ATs and SCSs have adequate sports nutrition knowledge, whereas most coaches and athletes have inadequate knowledge. Athletes have frequent contact with ATs and SCSs; therefore, proper nutrition education among these staff members is critical. We suggest that proper nutrition programming should be provided for athletes, coaches, ATs, and SCSs. However, a separate nutrition program should be integrated for ATs and SCSs. This integrative approach is beneficial for the continuity of care, as both categories of professionals might be developing and integrating preventive or rehabilitative programs for athletes.

Travel-Associated Illness in Older Adults (>60 y).

Background. Older individuals represent a substantial proportion of international travelers. Because of physiological changes and the increased probability of underlying medical conditions, older travelers might be at higher risk for at least some travel-associated diseases. Methods. With the aim of describing the epidemiology of travel-associated diseases in older adults, medical data were prospectively collected on ill international travelers presenting to GeoSentinel sites from 1997 to 2009. Seven thousand thirty-four patients aged 60 years and over were identified as older travelers and were compared to 56,042 patients aged 18-45 years, who were used as the young adult reference population. Results. The proportionate morbidity of several etiological diagnoses was higher in older ill travelers compared to younger ill, including notably lower respiratory tract infections, high-altitude pulmonary edema, phlebitis and pulmonary embolism, arthropod bites, severe malaria, rickettsiosis, gastritis, peptic ulcers, esophagitis and gastroesophageal reflux disease, trauma and injuries, urinary tract infections, heart disease, and death. In contrast, acute diarrhea, upper respiratory tract infections, flu and flu-like illnesses, malaria, dengue, genital infections, sexually transmitted diseases, and schistosomiasis proportionate morbidities were lower among the older group. Conclusion. Older ill travelers are more likely to suffer from certain life-threatening diseases and would benefit from reinforcement of specific preventive measures including use of anti-thrombosis compression stockings and sufficient hydration and exercises during long-distance flights, hand hygiene, use of disposable handkerchiefs, consideration of face-masks in crowded conditions, influenza and pneumococcal vaccines, progressive acclimatization to altitude, consideration of acetazolamide, and use of repellents and mosquito nets. Antibiotics for the presumptive treatment of respiratory and urinary tract infections may be considered, as well as antacid medications. At-risk patients should be referred to a specialist for medical evaluation before departing, and optimal control of co-morbidities such as cardiovascular and chronic obstructive pulmonary diseases should be achieved, particularly for high-altitude travel.

"Older persons and heat-susceptibility: the role of health promotion in a changing climate. "

ISSUE ADDRESSED: Many studies worldwide have provided evidence that older persons are a sub-population at increased risk of heat-related morbidity and mortality. This article gives an overview of the current state of knowledge of risk factors and provides commentary on the role of health promotion in the prevention of a climate change-related increase in elderly heat casualties. METHODS: A search of peer-reviewed medical and epidemiological literature and community health websites was conducted in order to gain an in-depth understanding of heat-susceptibility in the elderly and preventive strategies. Key search words included: elderly, aged, older, heat, thermoregulation, heat wave, mortality, heat effects, dehydration, heat-related illness, adaptation, adaptive capacity. RESULTS: The reasons underlying reduced heat tolerance in this group are multi-faceted, comprising physiological, social and behavioural limitations, with comorbidities and polypharmacy being contributing factors. Additionally, some older persons may be unable or reluctant to undertake adaptations necessary to maintain thermal homeostasis due to diminished awareness of the heat, lowered thirst sensation, mobility or cognitive impairments, a lowered perception of risk, or economic concerns. CONCLUSION: With older persons in poor health being particularly vulnerable to heat, preventive messages need to promote protective behaviours and help build resilience as temperatures rise.

Evaluation of a Clinical Dehydration Scale in Children Requiring Intravenous Rehydration.

OBJECTIVES: To evaluate the reliability and validity of a previously derived clinical dehydration scale (CDS) in a cohort of children with gastroenteritis and evidence of dehydration. METHODS: Participants were 226 children older than 3 months who presented to a tertiary care emergency department and required intravenous rehydration. Reliability was assessed at treatment initiation, by comparing the scores assigned independently by a trained research nurse and a physician. Validity was assessed by using parameters reflective of disease severity: weight gain, baseline laboratory results, willingness of the physician to discharge the patient, hospitalization, and length of stay. RESULTS: Interobserver reliability was moderate, with a weighted κ of 0.52 (95% confidence interval [CI] 0.41, 0.63). There was no correlation between CDS score and percent weight gain, a proxy measure of fluid deficit (Spearman correlation coefficient = -0.03; 95% CI -0.18, 0.12). There were, however, modest and statistically significant correlations between CDS score and several other parameters, including serum bicarbonate (Pearson correlation coefficient = -0.35; 95% CI -0.46, -0.22) and length of stay (Pearson correlation coefficient = 0.24; 95% CI 0.11, 0.36). The scale's discriminative ability was assessed for the outcome of hospitalization, yielding an area under the receiver operating characteristic curve of 0.65 (95% CI 0.57, 0.73). CONCLUSIONS: In children administered intravenous rehydration, the CDS was characterized by moderate interobserver reliability and weak associations with objective measures of disease severity. These data do not support its use as a tool to dictate the need for intravenous rehydration or to predict clinical course.

"Dehydration treatment practices among pediatrics-trained and non-pediatrics trained emergency physicians. "

OBJECTIVES: We sought to survey emergency physicians in the United States regarding the management of pediatric dehydration secondary to acute gastroenteritis. We hypothesized that responses from physicians with dedicated pediatric training (PT), that is, board certification in pediatrics or pediatric emergency medicine, would differ from responses of physicians with no dedicated pediatric training (non-PT). METHODS: An anonymous survey was mailed to randomly selected members of the American College of Emergency Physicians and sent electronically to enrollees of Brown University pediatric emergency medicine listserv. The survey consisted of 17 multiple-choice questions based on a clinical scenario depicting a 2-year-old with acute gastroenteritis and moderate dehydration. Questions asked related to treatment preferences, practice setting, and training information. RESULTS: One thousand sixty-nine surveys were received: 997 surveys were used for data analysis, including 269 PT physicians and 721 non-PT physicians. Seventy-nine percent of PT physicians correctly classified the scenario patient as moderately dehydrated versus 71% of non-PT physicians (P = 0.063). Among those who correctly classified the patient, 121 PT physicians (58%) and 350 non-PT physicians (68%) would initially hydrate the patient with intravenous fluids. Pediatrics-trained physicians were more likely to initially choose oral or nasogastric hydration compared with non-PT physicians (P = 0.0127). Pediatrics-trained physicians were less likely to perform laboratory testing compared with the non-PT group (n = 92, 45%, vs n = 337, 66%; P < 0.0001). CONCLUSIONS: Contrary to established recommendations for the management of moderately dehydrated children, significantly more PT physicians, compared with non-PT physicians, follow established guidelines.

"Dehydration at admission increased the need for dialysis in hemolytic uremic syndrome children."

BACKGROUND: Oligoanuric forms of postdiarrheal hemolytic uremic syndrome (D+ HUS) usually have more severe acute stage and higher risk of chronic sequelae than nonoligoanuric forms. During the diarrheal phase, gastrointestinal losses could lead to dehydration with pre-renal injury enhancing the risk of oligoanuric D+ HUS. Furthermore, it had been shown that intravenous volume expansion during the prodromal phase could decrease the frequency of oligoanuric renal failure. Thus, we performed this retrospective study to determine whether dehydration on admission is associated with increased need for dialysis in D+ HUS patients. CASE-DIAGNOSIS/ TREATMENT: Data from 137 children was reviewed, which were divided into two groups according to their hydration status at admission: normohydrated (n = 86) and dehydrated (n = 51). Laboratory parameters of the dehydrated patients reflected expected deteriorations (higher urea, higher hematocrit and lower sodium, bicarbonate, and pH) than normohydrated ones. Likewise, the dehydrated group had a higher rate of vomiting and need for dialysis (70.6 versus 40.7 %, p = 0.0007). CONCLUSIONS: Our data suggests that dehydration at hospital admission might represent a concomitant factor aggravating the intrinsic renal disease in D+ HUS patients increasing the need for dialysis. Therefore, the early recognition of patients at risk of D+ HUS is encouraged to guarantee a well-hydrated status.

"The epidemiology of hypernatraemia in hospitalised children in Lothian: a 10-year study showing differences between dehydration, osmoregulatory dysfunction and salt poisoning. "

INTRODUCTION: The relative frequencies of the causes of hypernatraemia in children after the neonatal period are unknown. Salt poisoning and osmoregulatory dysfunction are extremely rare and potentially fatal. In this retrospective 10-year study, the incidence, causes and differential biochemistry of hypernatraemia in children is examined. METHODS: Children with hypernatraemia (sodium ≥150 mmol/litre) aged >2 weeks to 17 years were identified from laboratory data of two paediatric departments serving the Lothian region of Scotland. A review of patient notes established time of onset and cause. Denominator data were available from the Scottish Health Service. RESULTS: On admission to hospital, 1 in 2288 children (1:1535 admitted as an emergency) had hypernatraemia. This is 1 in 30 563 Lothian children <17 years. Overall 0.04% hospital stays had an episode of hypernatraemia. In 45 children admitted with 64 separate episodes (11 from a case of salt poisoning), the commonest cause was dehydration secondary to either gastroenteritis or systemic infection; 31% had an underlying chronic neurological disorder. A total of 177 further cases developed hypernatraemia after admission. The commonest causes were dehydration secondary to severe systemic infection and postoperative cardiac surgery. Urine sodium:creatinine ratio and fractional excretion of sodium were both much higher in the salt poisoning case than in a child with osmoregulatory dysfunction or children with simple dehydration. CONCLUSIONS: Hypernatraemia after 2 weeks of age is uncommon, and on admission is usually associated with dehydration. Salt poisoning and osmoregulatory dysfunction are rare but should be considered in cases of repeated hypernatraemia without obvious cause. Routine measurement of urea, creatinine and electrolytes on paired urine and plasma on admission will differentiate these rare causes.

"Effect of intermittent rehydration therapy as an oral and enteral rehydration solution, alone or in combination with intravenous administration on intravascular dehydration. "

Aim: The purpose of this study was to demonstrate the effectiveness of intermittent fluid infusion (intermittent rehydration therapy) to dehydrated elderly patients and the efficacy of Heisei Solution Water (HSW), an oral and enteral rehydration solution developed by our group. Methods: We enrolled 375 elderly patients with suspected dehydration from among 1,921 patients of our hospital and 13 affiliated hospitals. A total of 36 of 375 patients received intermittent rehydration therapy. These patients were then divided into 3 groups according to the method of administration: (1) oral and enteral administration (n=16), (2) intravenous administration only (n=10) and (3) combined oral, enteral and intravenous administration (n=10). We then compared blood urea nitrogen/creatinine (BUN/Cr) ratios among the 3 groups. Results: BUN/Cr ratios were improved in all groups, but there was no statistically significant difference in the degree of improvement of BUN/Cr ratios among the 3 groups. Conclusion: Intermittent rehydration therapy is a highly effective way to manage dehydration. The intermittent oral and enteral administration of HSW demonstrated the same effectiveness as other forms of administration. FULL-TEXT AVAILABLE IN PUBMED.

Does anticipatory sweating occur prior to fluid consumption?

The purpose of this study was to examine if anticipatory sweating occurs prior to fluid consumption in dehydrated subjects. It was hypothesized that there would first be an anticipatory response to the sight of water, and then with drinking, a second response caused by mechanical stimulation of oropharyngeal nerves. Dehydrated subjects (n=19) sat in a heat chamber for 30 minutes. At minute 15, a resistance hygrometer capsule was attached and sweat rate was measured every 3 seconds. At minute 35:00, a researcher entered the room with previously measured water (2 ml/kg euhydrated body weight). At minute 35:30, the subject was allowed to drink. Data collection continued for 5 minutes post consumption. As expected, 16 of the 19 subjects responded to oropharyngeal stimuli with increased sweat rate. However, the new finding was that a majority (12 of 19) also showed an anticipatory sweating response prior to fluid consumption. Subjects were divided into 4 groups based on the magnitude of the sweating response. Strong responders' (n=4) anticipatory response accounted for 50% or more of the total change in sweat rate. Moderate responders' (n=4) anticipatory response accounted for 20%-49%. Weak responders' (n=4) anticipatory response accounted for 6-20%. Finally, non-responders (n=7) showed no anticipatory response. Although previously noted anecdotally in the literature, the current study is the first to demonstrate that measurable anticipatory sweating occurs prior to fluid intake in dehydrated subjects in a significant percentage of the population. Such data suggests that cerebral input, like oropharyngeal stimulation, can temporarily remove the dehydration-induced inhibition of sweating. FULL-TEXT AVAILABLE IN PUBMED.

Hydration and cognitive performance.

A clinical link exists between severe dehydration and cognitive performance. Using rapid and severe water loss induced either by intense exercise and/or heat stress, initial studies suggested there were alterations in short-term memory and cognitive function related to vision, but more recent studies have not all confirmed these data. Some studies argue that water loss is not responsible for the observations made, and studies compensating water losses have failed to prevent the symptoms. Studies in children have suggested that drinking extra water helps cognitive performance, but these data rely on a small number of children. In older adults (mean age around 60) the data are not strong enough to support a relationship between mild dehydration and cognitive function. Data on frail elderly and demented people are lacking. Methodological heterogeneity in these studies are such that the relationship between mild dehydration and cognitive performance cannot be supported.

Hydration assessment using the cardiovascular response to standing.

The cardiovascular response to standing (sit-to-stand change in heart rate; SSΔHR) is commonly employed as a screening tool to detect hypohydration (body water deficit). No study has systematically evaluated SSΔHR cut points using different magnitudes or different types of controlled hypohydration. The objective of this study was to determine the diagnostic accuracy of the often proposed 20 b/min SSΔHR cut point using both hypertonic and isotonic models of hypohydration. Thirteen healthy young adults (8M, 5F) underwent three bouts of controlled hypohydration. The first bout used sweating to elicit large losses of body water (mass) (>3 % sweat). The second two bouts were matched to elicit 3 % body mass losses (3 % diuretic; 3 % sweat). A euhydration control trial (EUH) was paired with each hypohydration trial for a total of six trials. Heart rate was assessed after 3-min sitting and after 1-min standing during all trials. SSΔHR was compared among trials, and receiver operator characteristic curve analysis was used to determine diagnostic accuracy of the 20 b/min SSΔHR cut point. Volunteers lost 4.5 ± 1.1, 3.0 ± 0.6, and 3.2 ± 0.6 % body mass during >3 % sweat, 3 % diuretic, and 3 % sweat trials, respectively. SSΔHR (b/min) was 9 ± 8 (EUH), 20 ± 12 (>3 % sweat; P < 0.05 vs. EUH), 17 ± 7 (3 % diuretic; P < 0.05 vs. EUH), and 13 ± 11 (3 % sweat). The 20 beats/min cut point had high specificity (90 %) but low sensitivity (44 %) and overall diagnostic accuracy of 67 %. SSΔHR increased significantly in response to severe hypertonic hypohydration and moderate isotonic hypohydration, but not moderate hypertonic hypohydration. However, the 20 beats/min cut point afforded only marginal diagnostic accuracy.

"The Meaning of Parenteral Hydration to Family Caregivers and Patients With Advanced Cancer Receiving Hospice Care. "

CONTEXT: In the U.S., patients with advanced cancer who are dehydrated or have decreased oral intake almost always receive parenteral hydration in acute care facilities but rarely in the hospice setting. OBJECTIVES: To describe the meaning of hydration for terminally ill cancer patients in home hospice care and for their primary caregivers. METHODS: Phenomenological interviews were conducted at two time points with 85 patients and 84 caregivers enrolled in a randomized, double-blind, controlled trial examining the efficacy of parenteral hydration in patients with advanced cancer receiving hospice care in the southern U.S. Transcripts were analyzed hermeneutically by the interdisciplinary research team until consensus on the theme labels was reached. RESULTS: Patients and their family caregivers saw hydration as meaning hope and comfort. Hope was the view that hydration might prolong a life of dignity and enhance quality of life by reducing symptoms such as fatigue and increasing patients' alertness. Patients and caregivers also described hydration as improving patients' comfort by reducing pain; enhancing the effectiveness of pain medication; and nourishing the body, mind, and spirit. CONCLUSION: These findings differ from traditional hospice beliefs that dehydration enhances patient comfort, given that patients and their families in the study viewed fluids as enhancing comfort, dignity, and quality of life. Discussion with patients and families about their preferences for hydration may help tailor care plans to meet specific patient needs.

"Decreased lactate and potassium levels in natural moisturizing factor from the stratum corneum of mild atopic dermatitis patients are involved with the reduced hydration state "

BACKGROUND: Atopic dermatitis (AD) shows dry skin. Water-soluble, low molecular weight components, collectively known as natural moisturizing factor (NMF), play an important role in maintaining the stratum corneum (SC) hydration. Previous studies focused on reduced levels of free amino acids (FAAs) in NMF from AD skin. It remains unknown, however, whether other NMF components are also altered in AD. OBJECTIVE: To characterize the levels of various NMF components in the SC of healthy subjects and in mild AD adult patients. METHODS: NMF components were extracted from three sequential tape-stripped SC samples obtained from the volar forearm. NMF components which were decreased in AD skin were topically applied to examine their contribution to SC moisturization in AD skin. RESULTS: We found that although FAAs levels were not remarkably reduced, levels of pyrrolidone carboxylic acid (PCA), lactate, urea, sodium and potassium were significantly decreased in NMF from mild AD skin. Among those components, only the topical application of potassium lactate effectively increased skin surface hydration indicating that reductions of lactate and potassium influence dry skin in mild AD patients. Unlike the distribution of filaggrin-derived FAAs and PCA, lactate, urea, potassium and sodium were abundant in the surface layer of the SC compared with the inner layer of the SC. Such findings strongly suggest that those components are supplied from outside the SC, i.e. they originate from sweat. CONCLUSION: The reduced levels of sweat-derived NMF components in mild AD patients suggests that impaired sweat function might in part result in the SC dryness.

 

 

Dipstick measurements of urine specific gravity are unreliable.

AIM:To evaluate the reliability of dipstick measurements of urine specific gravity (U-SG). METHODS: Fresh urine specimens were tested for urine pH and osmolality (U-pH, U-Osm) by a pH meter and an osmometer, and for U-SG by three different methods (refractometry, automatic readout of a dipstick (Clinitek-50), and (visual) change of colour of the dipstick). RESULTS: The correlations between the visual U-SG dipstick measurements and U-SG determined by a refractometer and the comparison of Clinitek((R))-50 dipstick U-SG measurements with U-Osm were less than optimal, showing very wide scatter of values. Only the U-SG refractometer values and U-Osm had a good linear correlation. The tested dipstick wasunreliable for the bedside determination of U-SG, even after correction for U-pH, as recommended by the manufacturer. CONCLUSIONS: Among the bedside determinations, only refractometry gives reliable U-SG results. Dipstick U-SGmeasurements should be abandoned.

Assessing hydration status.

PURPOSE:Understanding the importance of euhydration in humans in order to ensure good health in various situations, the purpose of this review is to examine the available techniques in assessing hydration status. RECENT FINDINGS: During the past 20 years, many indices have been developed to assess hydration levels accurately in humans. Changes in body weight, haematological and urine parameters, bioelectrical impedance, skinfold thickness, heart rate and blood pressure changes are among these indices. Plasma osmolality, urine osmolality and urine specific gravity are the most widely used markers of hydration. However, urine colour has also been used with reasonable accuracy when laboratory analysis is not available or when a quick estimate of hydration is necessary. Some data indicate that urine colour is as good indicator of hydration as plasma or urine osmolality or urine specific gravity. SUMMARY: Although there is no 'gold standard' for assessment of hydration status, it appears that changes in body weight, along with urine osmolality, specific gravity, conductivity and colour are among the most widely used indices. Furthermore, they provide reasonable results, especially when the analysis is based on the first morning urine sample

The Influence of Personality and Health Beliefs on Maintaining Proper Hydration

The present study was designed to examine factors that could facilitate or impede adherence to proper hydration. Forty volunteers (20 male, 20 female) were randomly assigned to one of two groups: Informed Group (n = 20) and Uninformed Group (n = 20). Bioelectrical impedance was used to measure intracellular (ICW) and extracellular (ECW) body water at Time 1 and 2. Personality, health beliefs, and health behaviors inventories were administered at Time 1. A health information brochure on proper hydration and consequences of poor hydration was given to the Informed Group. All participants were given six 1-liter bottles of water and drank two bottles per day. Both ICW, F(1,38) = 4.79, p < .05, and ECW, F(1,38) = 10.12, p < .005, significantly increased for both groups, and females had significantly greater changes than males in ECW, F(1,38) = 4.43, p < .05, and ICW, F(1,38) = 4.48, p < .05. Health information had no significant effect on female adherence but was a significant predictor of male adherence,  = .266, p < .05. Agreeableness, r = .36, p < .05, and social desirability, r = .33, p < .05, were the only personality factors related to change in ECW for the group as a whole. Health beliefs were unrelated to adherence, but general health concern,  = –.–.053, p < .05, was a significant predictor of change in ECW for males, although it was an inverse relationship.

Human hydration indices: acute and longitudinal reference values.

It is difficult to describe hydration status and hydration extremes because fluid intakes and excretion patterns of free-living individuals are poorly documented and regulation of human water balance is complex and dynamic. This investigation provided reference values for euhydration (i.e.; body mass; daily fluid intake; serum osmolality; M +/- SD); it also compared urinary indices in initial morning samples and 24-hr collections. Five observations of 59 healthy; active men (age 22 +/- 3 yr; body mass 75.1 +/- 7.9 kg) occurred during a 12-d period. Participants maintained detailed records of daily food and fluid intake and exercise. Results indicated that the mean total fluid intake in beverages; pure water; and solid foods was >2.1 L/24 hr (range 1.382-3.261; 95% confidence interval 0.970-3.778 L/24 hr); mean urine volume was >1.3 L/24 hr (0.875-2.250 and 0.675-3.000 L/24 hr); mean urine specific gravity was >1.018 (1.011-1.027 and 1.009-1.030); and mean urine color was > or = 4 (4-6 and 2-7). However; these men rarely (0-2% of measurements) achieved a urine specific gravity below 1.010 or color of 1. The first morning urine sample was more concentrated than the 24-h urine collection; likely because fluids were not consumed overnight. Furthermore; urine specific gravity and osmolality were strongly correlated (r2 = .81-.91; p < .001) in both morning and 24-hr collections. These findings provide euhydration reference values and hydration extremes for 7 commonly used indices in free-living; healthy; active men who were not exercising in a hot environment or training strenuously.

Sex difference of urinary osmolality in German children.

BACKGROUND/AIMS: Origin of sex difference in urinary osmolality. METHODS: In 495 healthy children aged 4.0-14.9 years participating in the DONALD (Dortmund Nutritional and Anthropometric Longitudinally Designed) study (247 boys, 248 girls), the water intake recorded in 24-hour weighed dietary records along with urinary volume, osmolality and free water reserve in 24-hour urine samples from the same day as the dietary record were determined. RESULTS: Boys showed a significantly higher energy intake, total water intake, urinary osmolality and osmolar load than girls but no increase in urinary volume. When referred to energy intake, mean urinary volume and mean free water reserve were significantly higher in girls than boys. Girls could have a preference for food with a higher water density and lower non-renal water losses. CONCLUSION: German girls of the DONALD study displayed a lower urinary osmolality than German boys due to a relatively higher urinary volume. The sex difference could be caused by a higher water density of the ingested food (ml/kcal) and a lower insensible water loss (ml/kcal) in girls than boys.

Problem: thirst, drinking behavior, and involuntary dehydration.

The phenomenon of involuntary dehydration, the delay in full restoration of a body water deficit by drinking, has been described extensively but relatively little is known about its physiological mechanism. It occurs primarily in humans when they are exposed to various stresses including exercise, environmental heat and cold, altitude, water immersion, dehydration, and perhaps microgravity, singly and in various combinations. The level of involuntary dehydration is approximately proportional to the degree of total stress imposed on the body. Involuntary dehydration appears to be controlled by more than one factor including social customs that influence what is consumed, the capacity and rate of fluid absorption from the gastrointestinal system, the level of cellular hydration involving the osmotic-vasopressin interaction with sensitive cells or structures in the central nervous system, and, to a lesser extent, hypovolemic-angiotensin II stimuli. Since humans drink when there is no apparent physiological stimulus, the psychological component should always be considered when investigating the total mechanisms for drinking.

Effects of athletes' muscle mass on urinary markers of hydration status.

To determine if athletes' muscle mass affects the usefulness of urine specific gravity (U(sg)) as a hydration index. Nine rugby players and nine endurance runners differing in the amount of muscle mass (42 +/- 6 vs. 32 +/- 3 kg, respectively; P = 0.0002) were recruited. At waking during six consecutive days, urine was collected for U (sg) analysis, urine osmolality (U(osm)), electrolytes (U[Na+], U[K+] and U[Cl-]) and protein metabolites (U([Creatinine]), U([Urea]) and U([Uric acid])) concentrations. In addition, fasting blood serum osmolality (S(osm)) was measured on the sixth day. As averaged during 6 days, U(sg) (1.021 +/- 0.002 vs. 1.016 +/- 0.001), U(osm) (702 +/- 56 vs. 554 +/- 41 mOsmol kg(-1) H(2)O), U([Urea]) (405 +/- 36 vs. 302 +/- 23 mmol L(-1)) and U([Uric acid]) (2.7 +/- 0.3 vs. 1.7 +/- 0.2 mmol L(-1)) were higher in rugby players than runners (P 1.020) despite S (osm) being below 290 mOsmol kg(-1) H(2)O in all participants. A positive correlation was found between muscle mass and urine protein metabolites (r = 0.47; P = 0.04) and between urine protein metabolites and U(sg) (r = 0.92; P < 0.0001). In summary, U(sg) specificity to detect hypohydration was reduced in athletes with large muscle mass. Our data suggest that athletes with large muscle mass (i.e., rugby players) are prone to be incorrectly classified as hypohydrated based on U(sg).

Markers of hydration status.

This paper reviews the literature, describes and discusses methods by which whole body hydration status can be determined in humans. A method of determining whether or not an individual is hypohydrated is of particular significance in an exercise situation as even moderate levels of hypohydration have a negative impact on exercise performance. Inspection of the published literature indicates that a number of methods have been used to determine hydration status. Body mass changes, urinary indices (volume, colour, protein content, specific gravity and osmolality), blood borne indices (haemoglobin concentration, haematocrit, plasma osmolality and sodium concentration, plasma testosterone, adrenaline, noradrenaline, cortisol and atrial natiuretic peptide), bioelectrical impedance analysis, and pulse rate and systolic blood pressure response to postural change are discussed. The urinary measures of colour, specific gravity and osmolality are more sensitive at indicating moderate levels of hypohydration than are blood measurements of hematocrit and serum osmolality and sodium concentration. Currently no "gold standard" hydration status marker exists, particularly for the relatively moderate levels of hypohydration that frequently occur in an exercise situation. The choice of marker for any particular situation will be influenced by the sensitivity and accuracy with which hydration status needs to be established together with the technical and time requirements and expense involved.

Markers of hydration status.

Many indices have been investigated to establish their potential as markers of hydration status. Body mass changes, blood indices, urine indices and bioelectrical impedance analysis have been the most widely investigated. The current evidence and opinion tend to favour urine indices, and in particular urine osmolality, as the most promising marker available.

Biological variation and diagnostic accuracy of dehydration assessment markers.

BACKGROUND: Well-recognized markers for static (one time) or dynamic (monitoring over time) dehydration assessment have not been rigorously tested for their usefulness in clinical, military, and sports medicine communities. OBJECTIVE: This study evaluated the components of biological variation and the accuracy of potential markers in plasma, urine, saliva, and body mass (B(m)) for static and dynamic dehydration assessment. DESIGN: We studied 18 healthy volunteers (13 men and 5 women) while carefully controlling hydration and numerous preanalytic factors. Biological variation was determined over 3 consecutive days by using published methods. Atypical values based on statistical deviations from a homeostatic set point were examined. Measured deviations in body fluid were produced by using a separate, prospective dehydration experiment and evaluated by receiver operating characteristic (ROC) analysis to quantify diagnostic accuracy. RESULTS: All dehydration markers displayed substantial individuality and one-half of the dehydration markers displayed marked heterogeneity of intraindividual variation. Decision levels for all dehydration markers were within one SD of the ROC criterion values, and most levels were nearly identical to the prospective group means after volunteers were dehydrated by 1.8-7.0% of B(m). However, only plasma osmolality (P(osm)) showed statistical promise for use in the static dehydration assessment. A diagnostic decision level of 301 plus mn 5 mmol/kg was proposed. Reference change values of 9 mmol/kg (P(osm)), 0.010 [urine specific gravity (U(sg))], and 2.5% change in B(m) were also statistically valid for dynamic dehydration assessment at the 95% probability level. CONCLUSIONS: P(osm) is the only useful marker for static dehydration assessment. P(osm), U(sg), and B(m) are valid markers in the setting of dynamic dehydration assessment. FULL-TEXT AVAILABLE IN PUBMD

Comparison of 3 Methods to Assess Urine Specific Gravity in Collegiate Wrestlers.

OBJECTIVE: To investigate the reliability and validity of refractometry, hydrometry, and reagent strips in assessing urine specific gravity in collegiate wrestlers. DESIGN AND SETTING: We assessed the reliability of refractometry, hydrometry, and reagent strips between 2 trials and among 4 testers. The validity of hydrometry and reagent strips was assessed by comparison with refractometry, the criterion measure for urine specific gravity. SUBJECTS: Twenty-one National Collegiate Athletic Association Division III collegiate wrestlers provided fresh urine samples. MEASUREMENTS: Four testers measured the specific gravity of each urine sample 6 times: twice by refractometry, twice by hydrometry, and twice by reagent strips. RESULTS: Refractometer measurements were consistent between trials (R =.998) and among testers; hydrometer measurements were consistent between trials (R =.987) but not among testers; and reagent-strip measurements were not consistent between trials or among testers. Hydrometer (1.018 +/- 0.006) and reagent-strip (1.017 +/- 0.007) measurements were significantly higher than refractometer (1.015 +/- 0.006) measurements. Intraclass correlation coefficients were moderate between refractometry and hydrometry (R =.869) and low between refractometry and reagent strips (R =.573). The hydrometer produced 28% false positives and 2% false negatives, and reagent strips produced 15% false positives and 9% false negatives. CONCLUSIONS: Only the refractometer should be used to determine urine specific gravity in collegiate wrestlers during the weight-certification process.

 

Effect of preexercise electrolyte ingestion on fluid balance in men and women.

PURPOSE: This article aimed to study the effect of preexercise ingestion of an electrolyte-containing beverage and meal on fluid balance during exercise in men and women. METHODS: Twenty healthy, college-aged people (10 males, 10 females; mean +/- SD = 51.2 +/- 9.8 mL x kg x min(-1)) exercised at 58 +/- 4% V O 2 peak for 90 min, 45 min after ingesting 355 mL of chicken noodle soup (SOUP; 167 mmol x L(-1) Na +), carbohydrate-electrolyte beverage (CE; 16 mmol x L(-1) Na+), or water (WATER). After 90 min of exercise, participants completed a physical performance task (PPT) consisting of the calculated work that would be completed in 30 min at 60% V O 2 peak (n = 19). Water was allowed ad libitum throughout all trials. RESULTS: Fluid balance was improved in SOUP compared with WATER (-251 +/- 418 vs -657 +/- 593 g, respectively; P = 0.002) because of greater water intake and retention throughout the trial. Water intake was also greater in CE compared with WATER mostly because of an increase during the PPT. Plasma osmolality increased after ingestion of SOUP and remained elevated throughout exercise compared with both CE and WATER. Men and women had similar fluid balance results, with women having lower relative water intake and evaporative water losses compared with men. Physical performance was similar in all trials. CONCLUSIONS: SOUP ingested before exercise improves fluid balance because of increased ad libitum water intake and reduced proportional urinary water loss. The increase in water intake and, subsequently, the improved fluid balance may be because of a greater plasma osmolality before and throughout exercise.

Voluntary dehydration among elementary school children residing in a hot arid environment

BACKGROUND: Voluntary dehydration is a condition where humans do not drink appropriately in the presence of an adequate fluid supply. This may adversely affect their physical and intellectual performance. The present study aimed to describe the prevalence of voluntary dehydration among elementary school children of different ethnicities and countries of birth. METHODS: Four hundred and twenty-nine elementary school children; aged 8-10 years; from four subpopulations (Israeli-born Jewish and Bedouin-Arab children; and immigrant children who recently arrived to Israel from Eastern Europe and from Ethiopia) were studied. The level of dehydration was determined by noontime urine osmolality; from samples taken over 1 week in mid-summer. Urine osmolality <500 mOsmol kg(-1) H(2)O was considered to be an appropriate level of hydration. RESULTS: Mean urine osmolality was 862 +/- 211 mOsmol kg(-1) H(2)O. Osmolality above 800 mOsmol kg(-1) H(2)O was detected in 67.5% of the urine samples; among these; 25% were above 1000 mOsmol kg(-1) H(2)O. The most dehydrated group was that of Israeli-born Jewish children; whereas the Bedouin-Arab children were the least dehydrated. CONCLUSIONS: A high proportion of children who reside in a hot and arid environment were found to be in a state of moderate to severe dehydration. Bedouin ethnicity was associated with better hydration; whereas Israeli-born Jews were most severely dehydrated. Educational intervention programmes promoting water intake should start in early childhood and continue throughout life.

Effects of Ramadan upon fluid and food intake, fatigue, and physical, mental, andsocial activities: a comparison between the UK and Libya.

Two studies were performed during Ramadan, one in the UK (N=31) and the other in Libya (N=33). The aims were to assess some changes to lifestyle that are produced by fasting as well as effects due to culture. Subjects were studied on eight separate occasions: four control days (two before and two after Ramadan) and four days during the four weeks of Ramadan itself. A questionnaire was answered that asked about naps and fluid and food intake. The questions elicited if an individual had slept, drank, or eaten, plus the reasons for doing or not doing so. Also, subjects were asked to describe their physical, mental, and social activities, their fatigue, and their perceived abilities to perform physical or mental work. The questionnaire was answered five times per day: at sunrise, at 10:00 h, at 14:00 h, at sunset, and on retiring to sleep at night. Urine samples were collected at sunset and measured for osmolality. Differences between control and Ramadan days, as well as between subjects studied in UK and Libya, were assessed by analysis of variance. Correlations between fatigue and physical, mental, and social activities were also assessed, as were differences in urine osmolality. Fasting during Ramadan resulted in fewer activities and increased fatigue and frequency of napping during daytime. Changes in fluid and food intake indicated some degree of preparation for fasting before sunrise and a marked "recuperation" from fasting after sunset. The reasons given for napping in the daytime, for drinking or not drinking, and for eating or not eating, changed during Ramadan compared with control days; as a result, links between fatigue and activities, and fatigue and fluid and food intake, were all altered during Ramadan, particularly after sunset. Subjects become dehydrated during the daytime, but this was not reduced when females who were menstruating drank during this time. Several differences between the two studies were found. There was a greater frequency of napping during the daytime in the Libya study, and evidence for the conservation of energy during the daytime and reduced physical, mental, and social activities. Subjects' preparations for fasting and recovering from it--their fluid and food intakes and associated reasons for these--also differed. Possible explanations of these differences are discussed.

Influence of diuretic-induced dehydration on competitive running performance.

A diuretic drug (40 mg of furosemide) was utilized to study the effects of dehydration (D) on competitive running performance, without prior thermal or exercise stress. Eight men competed in randomized races of 1,500, 5,000, and 10,000 m, while normally hydrated (H) and with mean plasma volume reductions of 9.9, 12.3, and 9.9%, respectively. As a result of the reduced body water (change in body weight = -1.9, -1.6, and -2.1%), mean outdoor performance times on a running track increased 0.16 min, 1.31 min (P less than 0.05), and 2.62 min (P less than 0.05) in the 1,500-m, 5,000-m, and 10,000-m trials. Running performance decrements due to dehydration were more strongly correlated with changes in body weight (r = -0.79, -0.65, and -0.40) than with urine volume or plasma volume differences. In addition, subjects were studied during submaximal and maximal treadmill exercise while H and D (mean change in plasma volume = -7.1%). Neither submaximal nor maximal oxygen uptake was significantly altered (P greater than 0.05) as a consequence of D. Mean treadmill run time to volitional exhaustion was reduced by 41.4 s (P less than 0.05) during the D treadmill trial. Therefore, it appears that competitive performance in trials of long duration (5,000 and 10,000 m) was affected to a greater extent by D than the shorter 1,500-m event, even though submaximal and maximal oxygen uptake was not altered.

Influence of water drinking on resting energy expenditure in overweight children.

BACKGROUND: It was previously demonstrated that drinking water significantly elevates the resting energy expenditure(REE) in adults, and that low water intake is associated with obesity and lesser success in weight reduction. This study addressed the potential of water drinking to increase the REE in children, as an additional tool for weight management. OBJECTIVE: To examine the effect of drinking water on the REE of overweight children. DESIGN: A total of 21 overweight, otherwise-healthy children (age 9.9±1.4 years, 11 males) drank 10 ml kg(-1) cold water (4 °C). REE was measured before and after water ingestion, for 66 min. The main outcome measure was the change in mean REE from baseline values. RESULTS: Immediately after drinking water, there was a transient decrease in REE, from a baseline value of 3.32±1.15 kilojoule (kJ) per min to 2.56±0.66 kJ per min at minute 3 (P=0.005). A subsequent rise in REE was then observed, which was significantly higher than baseline after 24 min (3.89±0.78 kJ/min (P=0.021)), and at most time points thereafter. Maximal mean REE values were seen at 57 min after water drinking (4.16±1.43 kJ per min (P=0.004)), which were 25% higher than baseline. REE was significantly correlated with age, height, weight and fat-free mass; the correlations with maximal REE values after water drinking were stronger than with baseline REE values. CONCLUSIONS: This study demonstrated an increase of up to 25% in REE following the drinking of 10 ml kg(-1) of cold water in overweight children, lasting for over 40 min. Consuming the recommended daily amount of water for children could result in an energy expenditure equivalent to an additional weight loss of about 1.2 kg per year. These findings reinforce the concept of water-induced REE elevation shown in adults, suggesting that water drinking could assist overweight children in weight loss or maintenance, and may warrant emphasis in dietary guidelines against the obesity epidemic.

Drinking water with a meal: a simple method of coping with feelings of hunger,satiety and desire to eat.

This study examined whether drinking of water with breakfast affects the feelings of satiety and hunger, and how long after the meal this effect is maintained. Eight healthy, normal-weight women had three breakfasts with two extra glasses (4 dl) of water and three similar breakfasts without water. The breakfasts were served on three successive mornings during a 2 week period. The subjects filled in forms with visual analogue scales on feelings of hunger, satiety and desire to eat. The forms were filled just before the breakfast, in the middle of the breakfast before and after drinking of water, after finishing the meal, and thereafter every 30 min until 11.15 a.m. The results show that drinking two glasses of water affects subjective feelings of hunger and satiety during the meal, but this effect is not maintained after the meal. It is suggested that during a meal subjective feelings of hunger and satiety change independently of the food energy consumed. This study allows, however, no conclusions on the possible influence of drinking water on actual food intake during and after a meal.

Does the provision of cooled filtered water in secondary school cafeteriasincrease water drinking and decrease the purchase of soft drinks?

BACKGROUND: Secondary school students often do not drink sufficient quantities of water during the school day to prevent dehydration, promote learning and good health. The study aimed to measure the effect of health promotion and the free provision of cooled filtered water on the consumption of water and soft drinks. It also aimed to explore students' views of drinking water provision. METHODS: A study was conducted with three secondary schools in North Tyne side. Over a 3 month period one school was given cooled filtered water and active promotion (W + P), another had water only (W). The control school (C) took part in post-intervention focus group work. RESULTS: The average volume of water drunk by students, in school 'W + P' was greater (P = 0.05) than that drunk in school 'W' and control school 'C'. The volume of soft drinks purchased by students in all three schools before and during the intervention remained static. Focus group data revealed that students viewed their existing water provision as poor and wanted sufficient supplies of cooled filtered water in school. CONCLUSIONS: This pilot study indicates that active promotion of water drinking increased consumption of water by secondary school students. Further developments of the project are suggested.

Promotion and provision of drinking water in schools for overweight prevention:randomized, controlled cluster trial.

OBJECTIVE: The study tested whether a combined environmental and educational intervention solely promoting water consumption was effective in preventing overweight among children in elementary school. METHODS: The participants in this randomized, controlled cluster trial were second- and third-graders from 32 elementary schools in socially deprived areas of 2 German cities. Water fountains were installed and teachers presented 4 prepared classroom lessons in the intervention group schools (N = 17) to promote water consumption. Control group schools (N = 15) did not receive any intervention. The prevalence of overweight (defined according to the International Obesity Task Force criteria), BMI SD scores, and beverage consumption (in glasses per day; 1 glass was defined as 200 mL) self-reported in 24-hour recall questionnaires, were determined before (baseline) and after the intervention. In addition, the water flow of the fountains was measured during the intervention period of 1 school year (August 2006 to June 2007). RESULTS: Data on 2950 children (intervention group: N = 1641; control group: N = 1309; age, mean +/- SD: 8.3 +/- 0.7 years) were analyzed. After the intervention, the risk of overweight was reduced by 31% in the intervention group, compared with the control group, with adjustment for baseline prevalence of overweight and clustering according to school. Changes in BMI SD scores did not differ between the intervention group and the control group. Water consumption after the intervention was 1.1 glasses per day greater in the intervention group. No intervention effect on juice and soft drink consumption was found. Daily water flow of the fountains indicated lasting use during the entire intervention period, but to varying extent. CONCLUSION: Our environmental and educational, school-based intervention proved to be effective in the prevention of overweight among children in elementary school, even in a population from socially deprived areas. FULL TEXT AVAILABLE IN PUBMED

Hydration and disease.

Many diseases have multifactorial origins. There is increasing evidence that mild dehydration plays a role in the development of various morbidities. In this review, effects of hydration status on acute and chronic diseases are depicted (excluding the acute effects of mild dehydration on exercise performance, wellness, cognitive function, and mental performance) and categorized according to four categories of evidence (I-IV). Avoidance of a high fluid intake as a precautionary measure may be indicated in patients with cardiovascular disorders, pronounced chronic renal failure (III), hypoalbuminemia, endocrinopathies, or in tumor patients with cisplatin therapy (IIb) and menace of water intoxication. Acute systemic mild hypohydration or dehydration may be a pathogenic factor in oligohydramnios (IIa), prolonged labor (IIa), cystic fibrosis (III), hypertonic dehydration (III), and renal toxicity of xenobiotica (Ib). Maintaining good hydration status has been shown to positively affect urolithiasis (Ib) and may be beneficial in treating urinary tract infection (IIb), constipation (III), hypertension (III), venous thromboembolism (III), fatal coronary heart disease (III), stroke (III), dental disease (IV), hyperosmolar hyperglycemic diabetic ketoacidosis (IIb), gallstone disease (III), mitral valve prolapse (IIb), and glaucoma (III). Local mild hypohydration or dehydration may play a critical role in the pathogenesis of several broncho-pulmonary disorders like exercise asthma (IIb) or cystic fibrosis (Ib). In bladder and colon cancers, the evidence on hydration status' effects is inconsistent. FULL TEXT AVAILABLE IN PUBMED

Effect of aging on regional cerebral blood flow responses associated with osmoticthirst and its satiation by water drinking: a PET study.

Levels of thirst and ad libitum drinking decrease with advancing age, making older people vulnerable to dehydration. This study investigated age-related changes in brain responses to thirst and drinking in healthy men. Thirst was induced with hypertonic infusions (3.1 ml/kg 0.51M NaCl) in young (Y) and older (O) subjects. Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET). Thirst activations were identified by correlating rCBF with thirst ratings. Average rCBF was measured from regions of interest (ROI) corresponding to activation clusters in each group. The effects of drinking were examined by correlating volume of water drunk with changes in ROI rCBF from maximum thirst to post drinking. There were increases in blood osmolality (Y, 2.8 +/- 1.8%; O, 2.2 +/- 1.4%) and thirst ratings (Y, 3.1 +/- 2.1; O, 3.7 +/- 2.8) from baseline to the end of the hypertonic infusion. Older subjects drank less water (1.9 +/- 1.6 ml/kg) than younger subjects (3.9 +/- 1.9 ml/kg). Thirst-related activation was evident in S1/M1, prefrontal cortex, anterior midcingulate cortex (aMCC), premotor cortex, and superior temporal gyrus in both groups. Post drinking changes of rCBF in the aMCC correlated with drinking volumes in both groups. There was a greater reduction in aMCC rCBF relative to water drunk in the older group. Aging is associated with changes in satiation that militate against adequate hydration in response to hyperosmolarity, although it is unclear whether these alterations are due to changes in primary afferent inflow or higher cortical functioning.

Fluid restriction in heart failure patients: is it useful? The design of a prospective, randomised study.

Thirst is a common and troublesome symptom for patients with moderate to severe heart failure. The pharmacological and non-pharmacological treatment as well as the nature of the disease itself causes increased thirst. There is no evidence in the literature about the usefulness of fluid restriction for heart failure patients. Formerly, when very little pharmacological treatment was available, fluid restriction was one of the few interventional options but nowadays when the pharmacological treatment has improved, its importance may be questioned. This article describes the design of an on-going study with the aim to determine if an individualised and less restrictive fluid prescription can improve the quality of life, cardiac function and exercise capacity, and decrease in hospital admissions and thirst. This study will be performed as a two-group, 1:1 randomised cross-over study. In group 1, the patients are instructed to comply with a maximum fluid intake of 1.5 l. This is a standard treatment today. In group 2, the patients are recommended to intake a fluid, based on the physiological need of 30 ml/kg body weight/24 h, and are allowed to increase the fluid intake to a maximum of 35 ml/kg body weight/24 h. After 16 weeks, the patients will cross over to the other intervention strategy and continue for another 16 weeks.

Determinants of the sensation of thirst in terminally ill cancer patients.

While a sensation of thirst causes severe distress for a certain proportion of cancer patients in the terminal stage, the factors contributing to this symptom have not been established. To clarify the association between sensation of thirst and medical factors, especially dehydration, a cross-sectional observational study was performed on terminally ill cancer patients receiving inpatient hospice care. On admission to a palliative care unit, 88 consecutive patients underwent blood sampling and were requested to rate the intensity of thirst on a visual analogue scale (VAS). Physicians prospectively evaluated factors that might potentially be contributing to the symptom. The mean VAS score for thirst was 5.0+/-2.8, and 18% of the patients complained of severe thirst with a VAS score of > or = 8. No significant correlations were observed between the VAS score for thirst and the values of total protein, blood urea nitrogen (BUN), creatinine, sodium, osmolality, hematocrit, atrial natriuretic peptide (ANP), and biochemical dehydration defined by the levels of BUN, creatinine, sodium and osmolality. On the other hand, dehydration defined by ANP level ( or = 300 mosmol/kg), gastrointestinal cancer, survival, performance status, oral intake, vomiting, and stomatitis were significantly associated with the severity of thirst. In addition, mouth breathing and opioids were determined to be a potential clinical cause of severe thirst when a retrospective chart review was carried out. In conclusion, sensation of thirst is a frequent symptom in terminally ill cancer patients and is associated with dehydration, hyperosmolality, poor general conditions, stomatitis, oral breathing, and opioids. Careful assessments and treatment of underlying causes is important to alleviate patients' distress.

Thirst in the elderly with and without heart failure.

Elderly patients with heart failure (HF) may be troubled by thirst, despite the fact that elderly have an impaired ability to sense thirst. The present study was undertaken to compare the intensity of thirst in patients with and without HF and to evaluate how this symptom relates to the health-related quality of life and indices of the fluid balance. Forty-eight patients (mean age 80 years) admitted to hospital with worsening HF (n = 23) or with other acute illness (n = 25) graded their thirst and estimated their health-related quality of life (HRQoL). Serum sodium was measured and urine samples were assessed for color and electrolyte content. The HF patients reported significantly more intensive thirst (median = 75 mm) compared with those in the control group (median = 25 mm; p < 0.0001). There was no statistically significant relationship between thirst and HRQoL, which was low overall. Serum sodium and urine color did not differ significantly between the groups, but the urine of the HF patients had a lower sodium concentration and osmolality. We conclude

Fluid replacement and glucose infusion during exercise prevent cardiovasculardrift.

This study examined the influence of both hydration and blood glucose concentration on cardiovascular drift during exercise. We first determined if the prevention of dehydration during exercise by full fluid replacement prevents the decline in stroke volume (SV) and cardiac output (CO) during prolonged exercise. On two occasions, 10 endurance-trained subjects cycled an ergometer in a 22 degrees C room for 2 h, beginning at 70 +/- 1% maximal O2 uptake (VO2max) and in a euhydrated state. During one trial, no fluid (NF) replacement was provided and the subject's body weight declined 2.09 +/- 0.19 kg or 2.9%. During the fluid replacement trial (FR), water was ingested at a rate that prevented body weight from declining after 2 h of exercise (i.e., 2.34 +/- 0.17 1/2 h). SV declined 15% and CO declined 7% during the 20- to 120-min period of the NF trial while heart rate (HR) increased 10% and O2 uptake (VO2) increased 6% (all P less than 0.05). In contrast, SV was maintained during the 20- to 120-min period of FR while HR increased 5% and thus CO actually increased 7% (all P less than 0.05). Rectal temperature, SV, and HR were similar during the 1st h of exercise during NF and FR. However, after 2 h of exercise, rectal temperature was 0.6 degree C higher (P less than 0.05) and SV and CO were 11-16% lower (P less than 0.05) during NF compared with FR.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary reference intakes for water, sodium, potassium, chloride and sulphate.

This report is one in a series that presents a comprehensive set of reference values for nutrient intakes for healthy U.S. and Canadian individuals and populations. It is a product of the Food and Nutrition Board (FNB) of the Institute of Medicine, working in cooperation with Canadian scientists. The report establishes a set of reference values for dietary electrolytes and water to expand and replace previously published Recommended Dietary Allowances (RDAs) and Recommended Nutrient Intakes (RNIs) for the United States and Canada, respectively. Close attention was given to the evidence relating electrolyte intake to the risk of high blood pressure and hypertension, as well as other diseases, and the amounts of water from beverages and foods needed to maintain hydration. In addition, since requirements for sulphur can be met by inorganic sulfate in the diets of animals, a review of the role in inorganic sulfur in the form of sulfate is included. The group responsible for developing this report, the Panel on Dietary Reference Intakes for Electrolytes and Water, under the oversight and assistance of the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (the DRI Committee), has analyzed the evidence on risks and beneficial effects of nutrients included in this review.

Effect of beverage osmolality on intestinal fluid absorption during exercise.

To determine how osmolality of an orally ingested fluid-replacement beverage would alter intestinal fluid absorption from the duodenum and/or jejunum during 85 min of cycle exercise (63.3 +/- 0.9% peak O2 uptake) in a cool environment (22 degreesC), seven subjects (5 men, 2 women, peak O2 uptake = 54.5 +/- 3.8 ml . kg-1 . min-1) participated in four experiments separated by 1 wk in which they ingested a water placebo (WP) or one of three 6% carbohydrate (CHO) beverages formulated to give mean osmolalities of 197, 295, or 414 mosmol/kgH2O. CHO solutions also contained 17-18 meq Na+ and 3.2 meq K+. Nasogastric and multilumen tubes were fluoroscopically positioned in the gastric antrum and duodenojejunum, respectively. Subjects ingested a total of 23 ml/kg body mass of the test solution, 20% (370 +/- 9 ml) of this volume 5 min before exercise and 10% (185 +/- 4 ml) every 10 min thereafter. By using the rate of gastric emptying as the rate of intestinal perfusion (G. P. Lambert, R. T. Chang, D. Joensen, X. Shi, R. W. Summers, H. P. Schedl, and C. V. Gisolfi. Int. J. Sports Med. 17: 48-55, 1996), intestinal absorption was determined by segmental perfusion from the duodenum (0-25 cm) and jejunum (25-50 cm). There were no differences (P > 0.05) in gastric emptying (mean 18.1 +/- 1.3 ml/min) or total fluid absorption (802 +/- 109, 650 +/- 52, 674 +/- 62, and 633 +/- 74 ml . 50 cm-1 . h-1 for WP, hypo-, iso-, and hypertonic solutions, respectively) among beverages; but WP was absorbed faster (P < 0.05) from the duodenum than in the jejunum. Of the total volume of fluid ingested, 82 +/- 14, 74 +/- 6, 76 +/- 5, and 68 +/- 7% were absorbed for WP, hypo-, iso-, and hypertonic beverages, respectively. There were no differences in urine production or percent change in plasma volume among solutions. We conclude that total fluid absorption of 6% CHO-electrolyte beverages from the duodenojejunum during exercise, within the osmotic range studied, is not different from WP. FULL-TEXT AVAILABLE IN PUBMED

Effect of sodium in a rehydration beverage when consumed as a fluid or meal.

To investigate the impact of fluid composition on rehydration effectiveness, 30 subjects (15 men and 15 women) were studied during 2 h of rehydration after a 2.5% body weight loss. In a randomized crossover design, subjects rehydrated with water (H2O), chicken broth (CB: 109.5 mmol/l Na, 25.3 mmol/l K), a carbohydrate-electrolyte drink (CE: 16.0 mmol/l Na, 3.3 mmol/l K), and chicken noodle soup (Soup: 333.8 mmol/l Na, 13.7 mmol/l K). Subjects ingested 175 ml at the start of rehydration and 20 min later; H2O was given every 20 min thereafter for a total volume equal to body weight loss during dehydration. At the end of the rehydration period, plasma volume was not significantly different from predehydration values in the CB (-1.6 +/- 1.1%) and Soup (-1.4 +/- 0.9%) trials. In contrast, plasma volume remained significantly (P < 0.01) below predehydration values in the H2O (-5.6 +/- 1.1%) and CE (-4.2 +/- 1.0%) trials after the rehydration period. Urine volume was greater in the CE (310 +/- 30 ml) than in the CB (188 +/- 20 ml) trial. Urine osmolality was higher in the CB and Soup trials than in the CE trial. Urinary sodium concentration was higher in the Soup and CB trials than in the CE and H2O trials. These results provide evidence that the inclusion of sodium in rehydration beverages, as well as consumption of a sodium-containing liquid meal, increases fluid retention and improves plasma volume restoration. FULL-TEXT AVAILABLE IN PUBMED

Fluid and electrolyte balance in ultra-endurance sport.

It is well known that fluid and electrolyte balance are critical to optimal exercise performance and, moreover, health maintenance. Most research conducted on extreme sporting endeavour (>3 hours) is based on case studies and studies involving small numbers of individuals. Ultra-endurance sportsmen and women typically do not meet their fluid needs during exercise. However, successful athletes exercising over several consecutive days come close to meeting fluid needs. It is important to try to account for all factors influencing bodyweight changes, in addition to fluid loss, and all sources of water input. Increasing ambient temperature and humidity can increase the rate of sweating by up to approximately 1 L/h. Depending on individual variation, exercise type and particularly intensity, sweat rates can vary from extremely low values to more than 3 L/h. Over-hydration, although not frequently observed, can also present problems, as can inappropriate fluid composition. Over-hydrating or meeting fluid needs during very long-lasting exercise in the heat with low or negligible sodium intake can result in reduced performance and, not infrequently, hyponatraemia. Thus, with large rates of fluid ingestion, even measured just to meet fluid needs, sodium intake is vital and an increased beverage concentration [30 to 50 mmol/L (1.7 to 2.9 g NaCl/L) may be beneficial. If insufficient fluids are taken during exercise, sodium is necessary in the recovery period to reduce the urinary output and increase the rate of restoration of fluid balance. Carbohydrate inclusion in a beverage can affect the net rate of water assimilation and is also important to supplement endogenous reserves as a substrate for exercising muscles during ultra-endurance activity. To enhance water absorption, glucose and/or glucose-containing carbohydrates (e.g. sucrose, maltose) at concentrations of 3 to 5% weight/volume are recommended. Carbohydrate concentrations above this may be advantageous in terms of glucose oxidation and maintaining exercise intensity, but will be of no added advantage and, if hyperosmotic, will actually reduce the net rate of water absorption. The rate of fluid loss may exceed the capacity of the gastrointestinal tract to assimilate fluids. Gastric emptying, in particular, may be below the rate of fluid loss, and therefore, individual tolerance may dictate the maximum rate of fluid intake. There is large individual variation in gastric emptying rate and tolerance to larger volumes. Training to drink during exercise is recommended and may enhance tolerance.

Effects of solution osmolality on absorption of select fluid replacement solutionsin human duodenojejunum.

These experiments examined relationships between initial osmolality and carbohydrate (CHO) composition of an infused solution and osmolality and water and CHO absorption in a test segment. A triple-lumen tube with a 10-cm mixing segment and a 40-cm test segment was passed into the duodenojejunum. The infusion port was approximately 10 cm beyond the pyloric sphincter. Perfusion solutions were hypotonic (186 mosmol/kg; solution A), isotonic (283 mosmol/kg; solution B), and hypertonic (403 mosmol/kg; solution C). All solutions contained 18 meq Na+ and 3 meq K+. In the mixing segment, osmolality increased 83 mosmol/kg and decreased 90 mosmol/kg for solutions A and C, respectively. Corresponding changes in the test segment were an increase of 60 mosmol/kg and a decrease of 34 mosmol/kg. The osmolality of solutionB did not change. In the test segment, mean osmolality and water and total solute fluxes were not significantly different among solutions, but solution C produced 27% greater fluid absorption than did solution A. When net fluid movement from mixing and test segments was determined, solution A produced 17% greater fluid absorption than did solution C. The mean increases in plasma and urine volumes over the 80-min test period were not significantly different. In the test segment, water flux correlated with CHO and Na+ fluxes but not with osmolality. In conclusion, 1) significant differences in solution osmolality were eliminated within the proximal duodenum and 2) perfusing 6% CHO solutions with osmolalities ranging from 186 to 403 mosmol/kg did not produce significant differences in fluid homeostasis (plasma volume) at the end of an 80-min test period.

Volume repletion after exercise-induced volume depletion in humans:replacement of water and sodium losses.

Sodium and water loss during, and replacement after, exercise-induced volume depletion was investigated in six volunteers volume depleted by 1.89 +/- 0.17% (SD) of body mass by intermittent exercise in a warm, humid environment. Subjects exercised in a large, open plastic bag, allowing collection of all sweat secreted during exercise. For over 60 min beginning 40 min after the end of exercise, subjects ingested drinks containing 0, 25, 50, or 100 mmol/l sodium (trials 0, 25, 50, and 100) in a volume (ml) equivalent to 150% of the mass lost (g) by volume depletion. Body mass loss and sweat electrolyte (Na+, K+, and Cl-) loss were the same on each trial. The measured sweat sodium concentration was 49.2 +/- 18.5 mmol/l, and the total loss (63.9 +/- 38.7 mmol) was greater than that ingested on trials 0 and 25. Urine production over the 6-h recovery period was inversely related to the amount of sodium ingested. Subjects were in whole body negative sodium balance on trials 0 (-104 +/- 48 mmol) and 25 (-65 +/- 30 mmol) and essentially in balance on trial 50 (-13 +/- 29 mmol) but were in positive sodium balance on trial 100 (75 +/- 40 mmol). Only on trial 100 were subjects in positive fluid balance at the end of the study. There was a large urinary loss of potassium over the recovery period on trial 100, despite a negligible intake during volume repletion. These results confirm the importance of replacement of sodium as well as water for volume repletion after sweat loss. The sodium intake on trial 100 was appropriate for acute fluid balance restoration, but its consequences for potassium levels must be considered to be undesirable in terms of whole body electrolyte homeostasis for anything other than the short term. FULL-TEXT AVAILABLE IN PUBMED

Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat.

PURPOSE: This study was conducted to determine whether preexercise ingestion of a highly concentrated sodium beverage would increase plasma volume (PV) and reduce the physiological strain of moderately trained males running in the heat. METHODS: Eight endurance-trained (.VO2max: 58 mL.kg(-1).min(-1) (SD 5); 36 yr (SD 11)) runners completed this double-blind, crossover experiment. Runners ingested a high-sodium (High Na+: 164 mmol Na+.L(-1)) or low-sodium (Low Na+: 10 mmol Na+.L(-1)) beverage (10 mL.kg(-1)) before running to exhaustion at 70% .VO2max in warm conditions (32 degrees C, 50% RH, V(a) approximately equal to 1.5 m.s(-1)). Beverages (approximately 757 mL) were ingested in seven portions across 60 min beginning 105 min before exercise. Trials were separated by 1-3 wk. Heart rate and core and skin temperatures were measured throughout exercise. Urine and venous blood were sampled before and after drinking and exercise. RESULTS: High Na+ increased PV before exercise (4.5% (SD 3.7)), calculated from Hct and [Hb]), whereas Low Na+ did not (0.0% (SD 0.5); P = 0.04), and involved greater time to exercise termination in the six who stopped because of an ethical end point (core temperature 39.5 degrees C: 57.9 min (SD 6) vs 46.4 min (SD 4); P = 0.04) and those who were exhausted (96.1 min (SD 22) vs 75.3 min (SD 21); P = 0.03; High Na+ vs Low Na+, respectively). At equivalent times before exercise termination, High Na+ also resulted in lower core temperature (38.9 vs 39.3 degrees C; P = 0.00) and perceived exertion (P = 0.01) and a tendency for lower heart rate (164 vs 174 bpm; P = 0.08). CONCLUSIONS: Preexercise ingestion of a high-sodium beverage increased plasma volume before exercise and involved less thermoregulatory and perceived strain during exercise and increased exercise capacity in warm conditions.

Metabolic and thermodynamic responses to dehydration-induced reductions in muscle blood flow in exercising humans

1. The present study examined whether reductions in muscle blood flow with exercise-induced dehydration would reduce substrate delivery and metabolite and heat removal to and from active skeletal muscles during prolonged exercise in the heat. A second aim was to examine the effects of dehydration on fuel utilisation across the exercising leg and identify factors related to fatigue. 2. Seven cyclists performed two cycle ergometer exercise trials in the heat (35 C; 61 +/- 2 % of maximal oxygen consumption rate, VO2,max), separated by 1 week. During the first trial (dehydration, DE), they cycled until volitional exhaustion (135 +/- 4 min, mean +/- s.e.m.), while developing progressive DE and hyperthermia (3.9 +/- 0.3 % body weight loss and 39.7 +/- 0.2 C oesophageal temperature, Toes). On the second trial (control), they cycled for the same period of time maintaining euhydration by ingesting fluids and stabilising Toes at 38.2 +/- 0.1 degrees C. 3. After 20 min of exercise in both trials, leg blood flow (LBF) and leg exchange of lactate, glucose, free fatty acids (FFA) and glycerol were similar. During the 20 to 135 +/- 4 min period of exercise, LBF declined significantly in DE but tended to increase in control. Therefore, after 120 and 135 +/- 4 min of DE, LBF was 0.6 +/- 0.2 and 1.0 +/- 0.3 l min-1 lower (P < 0.05), respectively, compared with control. 4. The lower LBF after 2 h in DE did not alter glucose or FFA delivery compared with control. However, DE resulted in lower (P < 0.05) net FFA uptake and higher (P < 0.05) muscle glycogen utilisation (45 %), muscle lactate accumulation (4.6-fold) and net lactate release (52 %), without altering net glycerol release or net glucose uptake. 5. In both trials, the mean convective heat transfer from the exercising legs to the body core ranged from 6.3 +/- 1.7 to 7.2 +/- 1.3 kJ min-1, thereby accounting for 35-40 % of the estimated rate of heat production ( approximately 18 kJ min-1). 6. At exhaustion in DE, blood lactate values were low whereas blood glucose and muscle glycogen levels were still high. Exhaustion coincided with high body temperature ( approximately 40 C). 7. In conclusion, the present results demonstrate that reductions in exercising muscle blood flow with dehydration do not impair either the delivery of glucose and FFA or the removal of lactate during moderately intense prolonged exercise in the heat. However, dehydration during exercise in the heat elevates carbohydrate oxidation and lactate production. A major finding is that more than one-half of the metabolic heat liberated in the contracting leg muscles is dissipated directly to the surrounding environment. The present results indicate that hyperthermia, rather than altered metabolism, is the main factor underlying the early fatigue with dehydration during prolonged exercise in the heat.

Effect of fluid ingestion on muscle metabolism during prolonged exercise.

Five trained men were studied during 2 h of cycling exercise at 67% peak oxygen uptake at 20-22 degrees C to examine the effect of fluid ingestion on muscle metabolism. On one occasion, the subjects completed this exercise without fluid ingestion(NF) while on the other they ingested a volume of distilled deionized water that prevented loss of body mass (FR). No differences in oxygen uptake during exercise were observed between the two trials. Heart rate was lower (P < 0.01) throughout exercise when fluid was ingested, and rectal temperature after 2 h of exercise was lower (38.0 +/- 0.2 and 38.6 +/- 0.2 degrees C for FR and NF, respectively; P < 0.01), as was muscle (vastus lateralis) temperature (38.5 +/- 0.4 and 39.1 +/- 0.5 degrees C for FR and NF, respectively; P < 0.05). Resting muscle ATP, creatine phosphate, creatine, glycogen, and lactate levels were similar in the two trials, as were the post exercise ATP, creatine phosphate, and creatine levels. In contrast, muscle glycogen was higher (P < 0.05) and muscle lactate was lower (P < 0.05) after 2 h of exercise in FR compared with NF. Net muscle glycogen utilization during exercise was reduced by 16% when fluid was ingested (318 +/- 46 and 380 +/- 53 mmol/kg dry weight for FR and NF, respectively; P < 0.05). These results indicate that fluid ingestion reduces muscle glycogen use during prolonged exercise, which may account, in part, for the improved performance previously observed with fluid ingestion.

American College of Sports Medicine position stand. Exercise and fluidreplacement.

This Position Stand provides guidance on fluid replacement to sustain appropriate hydration of individuals performing physical activity. The goal of prehydrating is to start the activity euhydrated and with normal plasma electrolyte levels. Prehydrating with beverages, in addition to normal meals and fluid intake, should be initiated when needed at least several hours before the activity to enable fluid absorption and allow urine output to return to normal levels. The goal of drinking during exercise is to prevent excessive (>2% body weight loss from water deficit) dehydration and excessive changes in electrolyte balance to avert compromised performance. Because there is considerable variability in sweating rates and sweat electrolyte content between individuals, customized fluid replacement programs are recommended. Individual sweat rates can be estimated by measuring body weight before and after exercise. During exercise, consuming beverages containing electrolytes and carbohydrates can provide benefits over water alone under certain circumstances. After exercise, the goal is to replace any fluid electrolyte deficit. The speed with which rehydration is needed and the magnitude of fluid electrolyte deficits will determine if an aggressive replacement program is merited.

Hydration effects on thermoregulation and performance in the heat.

During exercise, sweat output often exceeds water intake, producing a water deficit or hypohydration. The water deficit lowers both intracellular and extracellular fluid volumes, and causes a hypotonic-hypovolemia of the blood. Aerobic exercise tasks are likely to be adversely effected by hypohydration (even in the absence of heat strain), with the potential affect being greater in hot environments. Hypohydration increases heat storage by reducing sweating rate and skin blood flow responses for a given core temperature. Hypertonicity and hypovolemia both contribute to reduced heat loss and increased heat storage. In addition, hypovolemia and the displacement of blood to the skin make it difficult to maintain central venous pressure and thus cardiac output to simultaneously support metabolism and thermoregulation. Hyperhydration provides no advantages over euhydration regarding thermoregulation and exercise performance in the heat.

Urine specific gravity in exercisers prior to physical training.

Urine specific gravity (USG) is used as an index of hydration status. Many studies have used USG to estimate pre-exercise hydration in athletes. However, very little is known about the pre-exercise hydration status of recreational exercisers. The purpose of the present study was to measure the pre-exercise USG in a large sample of recreational exercisers who attended 2 different fitness centers in the United States. In addition, we wanted to determine if factors such as time of day, geographic location, and gender influenced USG. We tested 166 subjects in Chicago and 163 subjects in Los Angeles. Subjects completed a survey on their typical training regimen and fluid-replacement habits, and thereafter voided and delivered a urine sample to the investigators prior to beginning exercise. Samples were measured on site for USG using a hand-held refractometer. The mean (SD) USG was 1.018 (+/- 0.007) for all subjects. Males had a higher average USG (1.020 +/- 0.007) when compared with females (1.017 +/- 0.008; p = 0.001). Despite differences in climate, no difference in mean USG occurred based on location or time of day. Based on standards used for athletes (USG > or = 1.020), 46% of the exercisers were likely to be dehydrated.

Effect of glycerol-induced hyperhydration on thermoregulation and metabolismduring exercise in heat.

This study examined the effect of glycerol ingestion on fluid homeostasis, thermoregulation, and metabolism during rest and exercise. Six endurance-trained men ingested either 1 g glycerol in 20 ml H2O x kg(-1) body weight (bw) (GLY) or 20 ml H2O x kg(-1) bw (CON) in a randomized double-blind fashion, 120 min prior to undertaking 90 min of steady state cycle exercise(SS) at 98% of lactate threshold in dry heat (35 degrees C, 30% RH), with ingestion of CHO-electrolyte beverage (6% CHO) at 15-min intervals. A 15-min cycle, where performance was quantified in kJ, followed (PC). Pre-exercise urine volume was lower in GLY than CON (1119 +/- 97 vs. 1503 +/- 146 ml x 120 min(-1); p < .05). Heart rate was lower (p < .05) throughout SS in GLY, while forearm blood flow was higher (17.1 +/- 1.5 vs. 13.7 +/- 3.0 ml x 100 g tissue x min(-1); p < .05) and rectal temperature lower (38.7 +/- 0.1 vs. 39.1 +/- 0.1 degrees C; p < .05) in GLY late in SS. Despite these changes, skin and muscle temperatures and circulating catecholamines were not different between trials. Accordingly, no differences were observed in muscle glycogenolysis, lactate accumulation, adenine nucleotide, and phosphocreatine degradation or inosine 5'-monophosphate accumulation when comparing GLY with CON. Of note, the work performed during PC was 5% greater in GLY (252 +/- 10 vs. 240 +/- 9 kJ; p < .05). These results demonstrate that glycerol, when ingested with a bolus of water 2 hours prior to exercise, results in fluid retention, which is capable of reducing cardiovascular strain and enhancing thermoregulation. Furthermore, this practice increases exercise performance in the heat by mechanisms other than alterations in muscle metabolism.

Influence of body temperature on the development of fatigue during prolongedexercise in the heat.

We investigated whether fatigue during prolonged exercise in uncompensable hot environments occurred at the same critical level of hyperthermia when the initial value and the rate of increase in body temperature are altered. To examine the effect of initial body temperature [esophageal temperature (Tes) = 35.9 +/- 0.2, 37.4 +/- 0. 1, or 38.2 +/- 0.1 (SE) degrees C induced by 30 min of water immersion], seven cyclists (maximal O2 uptake = 5.1 +/- 0.1 l/min) performed three randomly assigned bouts of cycle ergometer exercise (60% maximal O2 uptake) in the heat (40 degrees C) until volitional exhaustion. To determine the influence of rate of heat storage (0.10 vs. 0.05 degrees C/min induced by a water-perfused jacket), four cyclists performed two additional exercise bouts, starting with Tes of 37.0 degrees C. Despite different initial temperatures, all subjects fatigued at an identical level of hyperthermia (Tes = 40. 1-40.2 degrees C, muscle temperature = 40.7-40.9 degrees C, skin temperature = 37.0-37.2 degrees C) and cardiovascular strain (heart rate = 196-198 beats/min, cardiac output = 19.9-20.8 l/min). Time to exhaustion was inversely related to the initial body temperature: 63 +/- 3, 46 +/- 3, and 28 +/- 2 min with initial Tes of approximately 36, 37, and 38 degrees C, respectively (all P < 0.05). Similarly, with different rates of heat storage, all subjects reached exhaustion at similar Tes and muscle temperature (40.1-40.3 and 40. 7-40.9 degrees C, respectively), but with significantly different skin temperature (38.4 +/- 0.4 vs. 35.6 +/- 0.2 degrees C during high vs. low rate of heat storage, respectively, P < 0.05). Time to exhaustion was significantly shorter at the high than at the lower rate of heat storage (31 +/- 4 vs. 56 +/- 11 min, respectively, P < 0.05). Increases in heart rate and reductions in stroke volume paralleled the rise in core temperature (36-40 degrees C), with skin blood flow plateauing at Tes of approximately 38 degrees C. These results demonstrate that high internal body temperature per se causes fatigue in trained subjects during prolonged exercise in uncompensable hot environments. Furthermore, time to exhaustion in hot environments is inversely related to the initial temperature and directly related to the rate of heat storage. FULL-TEXT AVAILABLE IN PUBMED

Effect of glycerol- induced hyperhydration on thermoregulatory and cardiovascularfunctions and endurance performance during prolonged cycling in a 25 degrees Cenvironment.

We compared the effect of glycerol-induced hyperhydration (GIH) to that of water-induced hyperhydration (WIH) on cardiovascular and thermoregulatory functions and endurance performance (EP) during prolonged cycling in a temperate climate in subjects consuming fluid during exercise. At weekly intervals, 6 trained male subjects ingested, in a randomized, double-blind, counterbalanced fashion, either a glycerol (1.2 g glycerol/kg bodyweight (BW) with 26 mL/kg BW of water-aspartame-flavored fluid) or placebo solution (water-aspartame-flavored fluid only) over a 2 h period. Subjects then performed 2 h of cycling at 66% of the maximal oxygen consumption (VO(2) max) and 25 degrees C while drinking 500 mL/h of sports drink, which was followed by a step-incremented cycling test to exhaustion. Levels of hyperhydration did not differ significantly between treatments before exercise. During exercise, GIH significantly reduced urine production by 246 mL. GIH did not increase sweat rate nor did it decrease heart rate, rectal temperature, or perceived exertion during exercise as compared with WIH. EP was not significantly different between treatments. Neither treatment induced undesirable side effects. It is concluded that, compared with WIH, GIH decreases urine production, but does not improve cardiovascular orthermoregulatory functions, nor does it improve EP during 2 h of cycling in a 25 degrees C environment in trained athletes consuming 500 mL/h of fluid during exercise.

Circulatory regulation during exercise in different ambient temperatures.

Three relatively fit subjects performed duplicate 20- to 25-min cycle ergometer exercise bouts at moderate and heavy intensities (40% and 70% Vo2 max) in ambient temperatures of 20, 26, and 36 degrees C. They approached a steady state in internal body temperature (Tes) in all but the heavy exercise in the heat, where Tes rose consistently, averaging 38.84 degrees C at the termination of exercise. Cardiac output (Q), estimated by a rebreathing technique, was proportional to Vo2 and independent of the body temperatures, except during the lower exercise intensity in the heart, where Q averaged 1.31 . min -1 higher throughout. In any environment, forearm blood flow was linearly related to Tes above the Tes threshold for vasodilation, but during heavy exercise in the heat this relationship was severely attenuated above a Tes around 38.0 degrees C, when forearm blood flow exceeded 15 ml.min -1 .100 ml -1. Plasma volume decreases during exercise were primarily a function of the intensity of exercise. During heavy exercise in the heat the relative vasconstriction contributes to the maintenance of an adequate stroke volume preventing a fall in Q. In this case, circulatory regulation has precedence over temperature regulation.

Human circulatory and thermoregulatory adaptations with heat acclimation andexercise in a hot, dry environment.

1. Heat acclimation was induced in eight subjects by asking them to exercise until exhaustion at 60% of maximum oxygen consumption rate (VO2) for 9-12 consecutive days at an ambient temperature of 40 degrees C, with 10% relative humidity (RH). Five control subjects exercised similarly in a cool environment, 20 degrees C, for 90 min for 9-12 days; of these, three were exposed to exercise at 40 degrees C on the first and last day. 2. Acclimation had occurred as seen by the increased average endurance from 48 min to 80 min, the lower rate of rise in the heart rate (HR) and core temperature and the increased sweating. 3. Cardiac output increased significantly from the first to the final heat exposure from 19.6 to 21.4 l min-1; this was possibly due to an increased plasma volume and stroke volume. 4. The mechanism for the increased plasma volume may be an isosmotic volume expansion caused by influx of protein to the vascular compartment, and a sodium retention induced by a significant increase in aldosterone. 5. The exhaustion coincided with, or was elicited when, core temperature reached 39.7 +/- 0.15 degrees C; with progressing acclimation processes it took progressively longer to reach this level. However, at this point we found no reduction in cardiac output, muscle (leg) blood flow, no changes in substrate utilization or availability, and no recognized accumulated 'fatigue' substances. 6. It is concluded that the high core temperature per se, and not circulatory failure, is the critical factor for the exhaustion during exercise in heat stress.

Influence of sodium replacement on fluid ingestion following exercise-induceddehydration.

This study investigated the hypothesis that addition of Na+ to a rehydration beverage would stimulate drinking and augment restoration of body water in individuals dehydrated during 90 min of continuous treadmill exercise in the heat. Following a 3.0 +/- 0.2% decrease in body weight (BW), 6 subjects sat in a thermoneutral environment for 30 min to allow body fluid compartments to stabilize. Over the next 3 hr, subjects rehydrated ad libitum using either flavored/artificially sweetened water (H2O-R) or a flavored, 6% sucrose drink containing either 25 (LNa(+)-R) or 50 (HNa(+)-R) mmol/L NaCl. Results demonstrated that rapid removal of the osmotic stimulus, during H2O-R, and the volume-dependent dipsogenic stimuli, during HNa(+)-R, are important factors in limiting fluid intake during rehydration, compared to LNa(+)-R. It was also found that the pattern of fluid replacement and restoration of fluid balance following dehydration is influenced by the dehydration protocol used to induce the loss in total body water and the sodium content of the rehydration beverage.

Rosenbloom C.

Athletes who are properly fueled and hydrated before, during, and after exercise can improve training, increase performance, and decrease fatigue. Many commercial products are marketed to athletes and are designed to be consumed at specific periods: before, during, and after exercise. Are these products really necessary? This article reviews the research on nutrition support for the athlete surrounding exercise and discusses the different nutritional needs of the recreational athlete versus the elite athlete. Guidelines for macronutrient intake before, during, and after exercise are provided along with decision trees to help the practitioner guide the athlete to proper fueling strategies.

Role of osmolality and plasma volume during rehydration in humans.

To determine how the sodium content of ingested fluids affects drinking and the restoration of the body fluid compartments after dehydration, we studied six subjects during 4 h of recovery from 90-110 min of a heat [36 degrees C, less than 30% relative humidity (rh)] and exercise (40% maximal aerobic power) exposure, which caused body weight to decrease by 2.3%. During the 1st h, subjects rested seated without any fluids in a thermoneutral environment (28 degrees C, less than 30% rh) to allow the body fluid compartments to stabilize. Over the next 3 h, subjects rehydrated ad libitum using tap water and capsules containing either placebo (H2O-R) or 0.45 g NaCl (Na-R) per 100 ml water. During the 3-h rehydration period, subjects restored 68% of the lost water during H2O-R, whereas they restored 82% during Na-R (P less than 0.05). Urine volume was greater in H2O-R than in Na-R; thus only 51% of the lost water was retained during H2O-R, whereas 71% was retained during Na-R (P less than 0.05). Plasma osmolality was elevated throughout the rehydration period in Na-R, whereas it returned to the control level by 30 min in H2O-R (P less than 0.05). Changes in free water clearance followed changes in plasma osmolality. The restoration of plasma volume during Na-R was 174% of that lost. During H2O-R it was 78%, which seemed to be sufficient to diminish volume-dependent dipsogenic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Stroke volume during exercise: interaction of environment and hydration.

Euhydrated and dehydrated subjects exercised in a hot and a cold environment with our aim to identify factors that relate to reductions in stroke volume (SV). We hypothesized that reductions in SV with heat stress are related to the interaction of several factors rather than the effect of elevated skin blood flow. Eight male endurance-trained cyclists [maximal O(2) consumption (VO(2 max)) 4.5 +/- 0.1 l/min; means +/- SE] cycled for 30 min (72% VO(2 max)) in the heat (H; 35 degrees C) or the cold (C; 8 degrees C) when euhydrated or dehydrated by 1.5, 3.0, or 4.2% of their body weight. When euhydrated, SV and esophageal temperature (T(es) 38. 2-38.3 degrees C) were similar in H and C, whereas skin blood flow was much higher in H vs. C (365 +/- 64% higher; P < 0.05). With each 1% body weight loss, SV declined 6.4 +/- 1.3 ml (4.8%) in H and 3.4 +/- 0.4 ml (2.5%) in C, whereas T(es) increased 0.21 +/- 0.02 and 0. 10 +/- 0.02 degrees C in H and C, respectively (P < 0.05). However, reductions in SV were not associated with increases in skin blood flow. The reduced SV was highly associated with increased heart rate and reduced blood volume in both H (R = 0.96; P < 0.01) and C (R = 0. 85; P < 0.01). In conclusion, these results suggest that SV is maintained in trained subjects during exercise in euhydrated conditions despite large differences in skin blood flow. Furthermore, the lowering of SV with dehydration appears largely related to increases in heart rate and reductions in blood volume. FULL-TEXT AVAILABLE IN PUBMED

 

 

We studied the relationship between plasma osmolality, arginine vasopressin (AVP), and fluid input in patients during the acute phase of a first stroke. Fifteen consecutive patients were studied (median age 79) and their blood sampled on days 0, 1, 2, 3, 7 and 14. Plasma osmolality was related to fluid input over days 0-3 (p = 0.0013) and AVP over 14 days (p less than 0.001). Patients with a poor outcome had higher AVP concentrations (p = 0.02). Those on intravenous fluids received a higher volume (p less than 0.01) and had a lower plasma osmolality (p = 0.04). The results of this preliminary study indicate that a standard regime for fluid input is inappropriate.

Comparison of 3 methods to assess urine specific gravity in collegiate wrestlers.

OBJECTIVE: To investigate the reliability and validity of refractometry, hydrometry, and reagent strips in assessing urinespecific gravity in collegiate wrestlers. DESIGN AND SETTING: We assessed the reliability of refractometry, hydrometry, and reagent strips between 2 trials and among 4 testers. The validity of hydrometry and reagent strips was assessed by comparison with refractometry, the criterion measure for urine specific gravity. SUBJECTS: Twenty-one National Collegiate Athletic Association Division III collegiate wrestlers provided fresh urine samples. MEASUREMENTS: Four testers measured the specific gravity of each urine sample 6 times: twice by refractometry, twice by hydrometry, and twice by reagent strips. RESULTS: Refractometer measurements were consistent between trials (R =.998) and among testers; hydrometer measurements were consistent between trials (R =.987) but not among testers; and reagent-strip measurements were not consistent between trials or among testers. Hydrometer (1.018 +/- 0.006) and reagent-strip (1.017 +/- 0.007) measurements were significantly higher than refractometer (1.015 +/- 0.006) measurements. Intraclass correlation coefficients were moderate between refractometry and hydrometry (R =.869) and low between refractometry and reagent strips (R =.573). The hydrometer produced 28% false positives and 2% false negatives, and reagent strips produced 15% false positives and 9% false negatives. CONCLUSIONS: Only the refractometer should be used to determine urine specific gravity in collegiate wrestlers during the weight-certification process.

Urine test strips: how reproducible are readings?

In an experiment, multiple reagent test strips from 90 urine samples were examined twice: observed visually by one of two persons and analyzed by spectrophotometry. Interobserver and intra-observer agreement were calculated and expressed as Cohen's K. Interobserver and intra-observer agreement were moderate to good, but lower than one might expect. Enhancing discoloration of the test pads could improve reproducibility. FULL-TEXT AVAILABRLE IN PUBMED

Clinical and physical signs for identification of impending and current water-loss dehydration in older people

This is the protocol for a review and there is no abstract. The objectives are as follows: To determine the diagnostic accuracy of state, minimally invasive clinical and physical signs (or sets of signs) to be used as screening tests for detecting impending or current water-loss dehydration, or both, in older people by systematically reviewing studies that have measured a reference standard and at least one index test in people aged 65 years and over. 1. To assess the effect of different cut offs of index test results assessed using continuous data on sensitivity and specificity in diagnosis of impending or current water-loss dehydration. 2. To identify clinical and physical signs that may be used in screening for impending or current water-loss dehydration in older people. 3. To identify clinical and physical signs that are not useful in screening for impending or current water-loss dehydration in older people. 4. To directly compare promising index tests (sensitivity _ 0.60 and specificity _ 0.75) where two or more are measured in a single study (direct comparison). 5. To carry out an exploratory analysis to assess the value of combining the best three index tests where the three tests each have some predictive ability of their own, and individual studies include participants who had all three tests. We will explore sources of heterogeneity of diagnostic accuracy of individual clinical and physical signs that show some evidence of discrimination by the reference standard used, cut off value for tests providing continuous data, type of participants (community dwelling older people, those in residential care, and those in hospital), sex, and baseline prevalence of dehydration.

Hydration in acute stroke: where do we go from here?

Objectives: to examine current practice with regard to hydration in acute stroke (part 1) to identify problem areas, to develop, implement and evaluate an intervention package (part 2). Design: prospective, repeated measures, between subjects Setting: a district general hospital. Participants: consecutive admissions with an acute stroke. Part 1 involved 30 patients, 14 of whom were women whose median age was 73 (45–90), part 2 involved 48 patients, 27 of whom were women whose median age was 73 (47–91). Main outcome measures: amount of fluid prescribed, received and mode of delivery in the first 2 weeks plus standardized swallowing assessments on admission, days 3, 7 and 14. Results: in both parts 1 and 2 of the study patients were appropriately managed according to the results of the SSA. However, in part 1 it was found that patients were documented as, on average, receiving less than 21 (regardless of mode of delivery) and were being prescribed little more than 1.51 per day. In part 2 there was a 33% increase (P<0.005) in fluid prescribed, but no significant increase (P=0.76) in the amount of fluid documented as having been delivered. This was independent of admitting ward. Conclusions: the intervention package had little or no effect on practice. The reasons are discussed and recommendations made. Further interventions are to be explored, implemented and reaudited in the future

Influence of raised osmolarity on clinical outcome after acute stroke.

BACKGROUND AND PURPOSE: Abnormal physiological parameters after acute stroke may induce early neurological deterioration. Studies of the effect of dehydration on stroke outcome are limited. We examined the association of raisedplasma osmolality on stroke outcome at 3 months and the change of plasma osmolality with hydration during the first weekafter stroke. METHODS: Acute stroke patients had their plasma osmolality measured at admission and at days 1, 3, and 7. Maximum plasma osmolality and the area under curve (AUC) were also calculated during the first week. Patients were stratified according to how they were hydrated: orally, intravenously, or both. Outcome included survival at 3 months after stroke. Logistic regression was performed to examine the association between raised plasma osmolality (>296 mOsm/kg) and survival, adjusting for stroke severity. Linear regression was performed to examine the pattern of plasma osmolality across hydration groups. RESULTS: One hundred sixty-seven patients were included. Mean admission (300 mOsm/kg, SD 11.4), maximum (308.1 mOsm/kg, SD 17.1), and AUC (298.3 mOsm/kg, SD 11.7) plasma osmolality were significantly higher in those who died compared with survivors (293.1 mOsm/kg [SD 8.2], 297.7 mOsm/kg [SD 8. 7], and 291.7 mOsm/kg [SD 8.1], respectively; P:296 mOsm/kg was significantly associated with mortality (OR 2.4, 95% CI 1.0 to 5.9). In patients hydrated intravenously, there was no significant fall in plasma osmolality compared with patients hydrated orally (P:=0.68). CONCLUSIONS: Raised plasma osmolality on admission is associated with stroke mortality, after correcting for case mix. Correction of dehydration after stroke requires a more systematic approach. Trials are required to determine whether correcting dehydration after stroke improves outcome. FULL TEXT AVAILABLE IN PUBMED

Urine colour as an index of hydration in critically ill patients

In order to test the hypothesis that urine colour can be used as an index of hydration in critically ill patients, we selected 40 intensive care and high-dependency patients and correlated urine colour (scored on an eight-point scale) with various indices of hydration: urine:plasma sodium, osmolality and urea ratios, urine output and central venous pressure. In addition, we compared the colour-chart score with scores made by intensive care nurses (without the benefit of a colour chart) in order to test subjective assessment of urine colour. There were weak but statistically significant correlations between urine colour andurine output (Spearman's r = - 0.555) and between urine colour and urine:plasma sodium ratio (Spearman's r = - 0.459). Subjective assessment of urine colour appeared to be reliable. Thus, although urine colour does vary with hydration in thecritically ill, assessment of urine colour adds little to the overall assessment of hydration in this group of patients.

Dehydration in the elderly: a short review.

Dehydration is the most common fluid and electrolyte problem among the elderly. The usual causes of water loss are frequently absent in dehydrated elderly patients. Age-related changes in total body water, thirst perception, renal concentrating ability, and vasopressin effectiveness probably predispose to dehydration. Dehydration related to infection, high-protein tube feedings, cerebral vascular accidents, and medication-related hypodypsia are particularly relevant for elderlypatients. Appropriate treatment depends on accurately assessing the water deficit and slowly correcting that deficit. FULL-TEXT AVAILABLE IN PUBMED

Dehydration: biological considerations, age-related changes and risk factors in older adults

Maintenance of water balance is essential to normal physiologic function and vigorous aging. Older adults, however, frequently experience alterations in fluid homeostasis, which result in dehydration. This article describes the physiology of water balance, age-related changes that influence fluid regulation, and associated risk factors for dehydration in older adults. Fluid hygiene is an important health promotion activity for this age group, but when efforts to prevent imbalance are unsuccessful, early identification and intervention to correct problems should be done to minimize adverse consequences. Although much is known about fluid homeostasis, dehydration, and contributory factors in the aging process, water disorders remain prevalent in this group. A great deal of work is still needed to determine "best practices" and creative clinical interventions to support adequate fluid intake behaviors. Both quality management programs and research studies provide avenues for systematic evaluation.

Human hydration indices: acute and longitudinal reference values.

It is difficult to describe hydration status and hydration extremes because fluid intakes and excretion patterns of free-living individuals are poorly documented and regulation of human water balance is complex and dynamic. This investigation provided reference values for euhydration (i.e., body mass, daily fluid intake, serum osmolality; M +/- SD); it also compared urinary indices in initial morning samples and 24-hr collections. Five observations of 59 healthy, active men (age 22 +/- 3 yr, body mass 75.1 +/- 7.9 kg) occurred during a 12-d period. Participants maintained detailed records of daily food and fluid intake and exercise. Results indicated that the mean total fluid intake in beverages, pure water, and solid foods was >2.1 L/24 hr (range 1.382-3.261, 95% confidence interval 0.970-3.778 L/24 hr); mean urine volume was >1.3 L/24 hr (0.875-2.250 and 0.675-3.000 L/24 hr); mean urine specific gravity was >1.018 (1.011-1.027 and 1.009-1.030); and mean urine color was > or = 4 (4-6 and 2-7). However, these men rarely (0-2% of measurements) achieved a urine specific gravity below 1.010 or color of 1. The first morning urine sample was more concentrated than the 24-h urine collection, likely because fluids were not consumed overnight. Furthermore, urine specific gravity and osmolality were strongly correlated (r2 = .81-.91, p < .001) in both morning and 24-hr collections. These findings provide euhydration reference values and hydration extremes for 7 commonly used indices in free-living, healthy, active men who were not exercising in a hot environment or training strenuously.
A complete urinalysis includes physical, chemical, and microscopic examinations. Midstream clean collection is acceptable in most situations, but the specimen should be examined within two hours of collection. Cloudy urine often is a result of precipitated phosphate crystals in alkaline urine, but pyuria also can be the cause. A strong odor may be the result of a concentrated specimen rather than a urinary tract infection. Dipstick urinalysis is convenient, but false-positive and false-negative results can occur. Specific gravity provides a reliable assessment of the patient's hydration status. Microhematuria has a range of causes, from benign to life threatening. Glomerular, renal, and urologic causes of microhematuria often can be differentiated by other elements of the urinalysis. Although transient proteinuria typically is a benign condition, persistent proteinuria requires further work-up. Uncomplicated urinary tract infections diagnosed by positive leukocyte esterase and nitrite tests can be treated without culture. FULL-TEXT AVAILABLE IN PUBMED

Swallowing, nutrition, and hydration during acute stroke care.

Dysphagia occurs in up to half of patients after an acute stroke and may cause dehydration, undernutrition, and aspiration pneumonia. Current evidence suggests that a systematic program of diagnosis and treatment of dysphagia in an acute stroke management plan may yield dramatic reductions in aspiration pneumonia rates. There is also some evidence thatnutritional supplementation and proper hydration may reduce morbidity and mortality in acute stroke patients. This article focuses on the recent advances in the evaluation and management of dysphagia, undernutrition, and dehydration related toacute stroke. A summary of pertinent studies in the area of stroke dysphagia and nutrition is also included. FULL-TEXT AVAILABLE IN PUBMED

Dehydration and venous thromboembolism thromboembolism after acute stroke.

BACKGROUND:Although it is widely assumed that dehydration predisposes to venous thromboembolism (VTE), there are no clinical studies to support this. Aim: To evaluate the relationship between biochemical indices of dehydration and VTEafter acute ischaemic stroke (AIS). DESIGN: Prospective observational study. METHODS: Unselected AIS patients (n = 102) receiving standard thromboprophylaxis with aspirin and graded compression stockings, underwent serial measurements of serum urea, creatinine and osmolality, and were screened for VTE using magnetic resonance direct thrombus imaging. RESULTS: Serum osmolality of >297 mOsm/kg, urea >7.5 mmol/l and urea:creatinine ratio (mmol:mmol) >80 a few days post-AIS were associated with odds ratios for VTE of, respectively, 4.7, 2.8 and 3.4 (p = 0.02, 0.05, 0.02) on multivariable analysis. DISCUSSION: Dehydration after AIS is strongly independently associated with VTE, reinforcing the importance of maintaining adequate hydration in these patients. FULL-TEXT AVAILABLE IN PUBMED

Dehydration in hospital-admitted stroke patients: detection, frequency, andassociation.

BACKGROUND AND PURPOSE:We aimed to determine the frequency of dehydration, risk factors, and associations with outcomes at hospital discharge after stroke.METHODS:\nWe linked clinical data from stroke patients in 2 prospective hospital registers with routine blood urea and creatinine results. Dehydration was defined by a blood urea-to-creatinine ratio >80. RESULTS:\nOf 2591 patients registered, 1606 (62%) were dehydrated at some point during their admission. Independent risk factors for dehydration included older age, female gender, total anterior circulation syndrome, and prescribed diuretics (all P<0.001). Patients with dehydration were significantly more likely be dead or dependent at hospital discharge than those without (χ(2)=170.5; degrees of freedom=2; P<0.0001).CONCLUSIONS:\nDehydration is common and associated with poor outcomes. Further work is required to establish if these associations are causal and if preventing or treating dehydration improves outcomes.

Water: a neglected nutrient in the young child? A South African perspective

Water is considered an essential nutrient because the body cannot produce enough water itself, by metabolism of food, to fulfil its need. When the quantity or quality of water is inadequate, health problems result, most notably dehydration and diarrhoea. As a result of contaminated water and poor hygiene, related infections are still a serious problem. Indeed, in theSouth African setting water availability and sanitation are critical issues because of the prevalence of childhood diarrhoea and also the HIV/AIDS crisis. Though considerable efforts have been made to improve the water and sanitation problems in SouthAfrica - especially with regard to water supply infrastructure - there is still room for much improvement. Water is a healthy alternative to calorie-dense, non-nutritive beverages, such as artificial fruit drinks and soda. The latter should be avoided as they contribute little other than energy and may contribute to overweight and obesity. Also, they displace more nutritious foods from the child's diet. Consumption of fruit juice should also be limited. These issues highlight the need for a specific guideline relating to water intake in the paediatric food-based dietary guidelines.

Diarrhoea in the critically ill

PURPOSE OF REVIEW: The purpose of this review is to update the knowledge on diarrhoea, a common problem in critically ill patients. Epidemiological data will be discussed, with special emphasis on diarrhoea in tube-fed patients and during antibiotic therapy. The possible preventive and therapeutic measures will be presented. RECENT FINDINGS: The need for concise definitions of diarrhoea was recently re-emphasized. The use of pump-driven continuous instead of intermittent enteral feeding is less often associated with diarrhoea. The discontinuation of enteral feeding during diarrhoea is not justified. Clostridium difficile-associated diarrhoea is frequent during antibiotic therapy with quinolones and cephalosporins. Formulas enriched with water-soluble fibres are probably effective to prevent diarrhoea, and promising data on the modulation of gut microflora with probiotics and prebiotics were recently released. SUMMARY: Diarrhoea is common in critically ill patients, especially when sepsis and hypoalbuminaemia are present, and during enteral feeding and antibiotic therapy. The management of diarrhoea includes generous hydration, compensation for the loss of electrolytes, antidiarrheal oral medications, the continuation of enteral feeding, and metronidazole or glycopeptides in the case of moderate to severe C. difficile colitis. The place of enteral formulas enriched with water-soluble fibres, probiotics and prebiotics is not yet fully defined.

Comparison between normal saline and a polyelectrolyte solution for fluid resuscitation in severely dehydrated infants with acute diarrhoea

The optimal intravenous solution for rehydration of infants and children with severe dehydration is debated. AIM: The aim was to compare the efficacy of a polyelectrolyte solution (group PS) with sodium chloride 0.9% solution (group NS) in rapid parenteral rehydration of severely dehydrated infants with acute diarrhoea. METHODS: Primary outcomes were volume and time to hydration. Secondary outcomes were urea, creatinine, electrolytes, glucose, arterial pH and bicarbonate levels. Patients were assigned randomly and openly to one of the two treatment groups. Severe dehydration was defined as one or more of the following associated with any other sign of dehydration: depressed consciousness, a weak or absent pulse or capillary refill time > 10 sec. Peripheral blood samples for chemical pathology were collected before and after rapid fluid therapy. The mean age of the 36 enrolled infants was 9.1 mths. All had depressed consciousness or severe hypotension/shock. The fluid infusion rate was 50 ml/kg/hr until haemodynamic stability was restored (absence of severe hypotension and two urine emissions). Fluid volume, time to rehydration and weight before and after rehydration were recorded. RESULTS: All infants recovered full pulse within 1 hr; most had a better level of consciousness or capillary refill <3 sec. Group NS (15 infants) showed (before and after treatment, respectively) a decrease of plasma potassium (3.4 to 3.1 mmol/L, p=0.07), bicarbonate (13.3 to 12.2 mmol/L, p=0.01) and glucose (8.2 to 5.8 mmol/L, p<0.01). Group PS (21 infants) showed a decrease of potassium (4.4 to 3.2 mmol/L, p<0.01) but an increase in bicarbonate (11.6 to 13.3 mmol/L, p<0.01) and glucose (11.4 to 14.8 mmol/L, p=0.08). CONCLUSION: Polyelectrolyte solution was as effective as normal saline on volume expansion and better for correcting acidosis.

 

Hydration profile and influence of beverage contents on fluid intake by women during outdoor recreational walking.

This study examined hydration status, sweat losses, and the effects of flavoring and electrolytes on fluid intake for women (n = 27, age = 24 ± 4 years) walking at a self-selected pace for ~1 h on a 1 km outdoor path during summer mornings or evenings. Over five consecutive days, participants consumed ad libitum one non-caloric beverage containing: (1) water (W), (2) acidified water (AW), (3) acidified water with electrolytes (AWE), (4) acidified water with flavor (AWF), and (5) acidified water with flavor and electrolytes (AWFE) in a counter-balanced order during walks and a 1-h recovery period. Walk Wet bulb globe temperature (26.2 ± 1.8 °C) and pace (6.0 ± 0.5 km/h) did not differ among beverages (P > 0.05). Thirty-four percent of pre-walk urine specific gravity samples exceeded 1.020. Flavoring (AWF 700 ± 393 mL; AWFE 719 ± 405 mL) did not result in greater consumption (P > 0.05) over W (560 ± 315 mL), with all three beverages exceeding grand mean sweat losses (528 ± 208 mL). Addition of electrolytes did not influence (P > 0.05) the intake between AW versus AWE or AWF versus AWFE. The results of this study indicate that the majority of women will consume fluids in excess of their sweat losses within 1 h post-walk. Over half of consumption took place during walks, highlighting the importance of fluid availability during exercise. Great among-subjects variability in sweat losses and fluid intake support the need for promoting individualized hydration strategies based on the changes in body mass for athletic populations.

Intestinal Temperature, Heart Rate, and Hydration Status in Multiday Trail Runners

OBJECTIVE: To assess heart rate (HR), intestinal body temperature (Tintest), and hydration status changes and relationships in 12 participants in a 3-day trail run. DESIGN: Descriptive field study. SETTING: Three Cranes Challenge trail run, in Karkloof, KwaZulu-Natal, South Africa. PARTICIPANTS: Twelve (5 men and 7 women) amateur runners. INTERVENTIONS: Trail run of 95 km divided into 3 stages: elevation gains on the 3 days, 1020, 1226, and 680 m, respectively. MAIN OUTCOME MEASURES: Changes in HR, Tintest, serum osmolality, and body mass. RESULTS: Environmental conditions were consistently mild (ambient temperature range, 11.5-22.8°C; maximum relative humidity range, 95%-97%), average running speed varied from 9.00 to 5.14 minutes/km, and distance covered in the 3 stages ranged from 32 (stages 1 and 3) to 40 km (stage 2). Mean HR ranged from 134 to 171 beats per minute in the 12 athletes during the trail events and averaged at 150 beats per minute, whereas Tintest ranged between 36.1 and 40.2°C. The correlation between maximum Tintest and percent age-predicted maximum HR (n = 12) was significant (R = 0.58; P 0.05). CONCLUSIONS: This study provides evidence in support of the contention that maximum Tintest is more closely related to metabolic rate during trail running than percent dehydration. The findings do not support an increase in core body temperature with a change in serum osmolality or body mass.

Effect of ramadan fasting on body water status markers after a rugby sevens match.

PURPOSE: To evaluate the effect of Ramadan fasting on body water status markers of rugby players at basal condition and following a simulation of rugby sevens match. METHODS: TWELVE RECREATIONAL RUGBY SEVENS PLAYERS PLAYED THREE MATCHES: one day before Ramadan (before Ramadan), at the end of the first week of Ramadan (Beg-R) and at the end of Ramadan (End-R). Before and immediately after each match, body weight was determined and blood samples were taken for the measurement of body water status markers. Total body water was measured with an impedancemeter only before matches. RESULTS: At rest, an increase in hematocrit (+4.4%, P=0.03), hemoglobin (+3.4%, P=0.01) and plasma osmolarity (+2.8%, P<0.001) was noticed at End-R compared to before Ramadan. Total body water measured before Ramadan did not differ significantly from that of Ramadan. After the match, values of hematocrit and plasma osmolarity increased significantly at End-R (+1.4%, P=0.02; +3.1%, P<0.001 respectively) compared to before Ramadan. Although, hemoglobin measured after matches occurring during Ramadan did not differ from those of before Ramadan. In response to matches, the change of percentage of body water status markers did not differ during each period of the investigation. CONCLUSIONS: The present results show that Ramadan fasting induces dehydration at basal conditions. Also, rugby sevens match played during Ramadan did not exacerbate the magnitude of responses to matches of blood and body water status markers.

Effects of dehydration on immune functions after a judo practice session.

We investigated the effects of dehydration after a judo practice session on player muscle and immune functions. Subjects included 25 female university judoists. Investigations were performed before and after 2.5 h of regular judo practice. Body composition, serum enzymes (myogenic enzymes, immunoglobulins and complements), neutrophils counts, reactive oxygen species (ROS) production capability, and phagocytic activity (PA) were measured. Subjects were divided into two groups according to level of dehydration after practice (mild dehydration and severe dehydration groups) and results were compared. Creatine kinase was found to increase significantly after practice. In addition, neutrophil count also increased significantly after practice in both groups. The changing ratios of IgA, IgG and C3 observed in the mild dehydration group were significantly higher than those in the severe dehydration group. In the severe dehydration group, post-practice PA/neutrophil had decreased significantly. Significant positive correlations were found between severity of dehydration and changing ratios of IgA, IgG, IgM, C3, C4 and ROS production capabilities, whereas no significant association was seen with PA and/or serum SOD activity. These results suggest that dehydration resulted in immunosuppression, including decreased neutrophil function.

Fluid balance and cycling performance following dehydration and rehydration with a carbohydrate-electrolyte solution.

The effect of ingestion of a 7.6% carbohydrate (CHO)-electrolyte solution (CES) or placebo (P) on rehydration (R) after exercise-induced dehydration and on subsequent time trial (TT) cycling performance was investigated. On four occasions, well-trained participants exercised in the heat (27°C) until ~3% body weight (BW) loss. After exercise, participants sat in a thermo-controlled environment (22°C) and ingested CES or P in a volume equal to 120% of previous BW loss. Fluids were ingested in 3 bolus of 50%, 40% and 30% at 0, 30, 60 min, respectively, during 2 h R period. Then, participants performed a 1 h TT, in which they ingested either no further fluid (in both CES and P trials; n=13) or ingested 2 ml·kg¯1 BW of a 15.3% CHO solution (in CES trial) or P (in P trial) at the start and on achieving 25% and 50% of work (n=6). R with CES (70±3%) was significantly higher compared to P (60±5%; n=13; p<0.01). When no fluid was ingested during TT, no difference in performance between CES and P was observed. When CHO was ingested during TT, performance was significantly improved with CES compared to P (61.2±1.7 vs 65.7±2.5 min, respectively; p<0.05; n=6). It is concluded that CES was more effective than P for rehydration and additional CHO supply just before and during TT improved subsequent cycling performance.

 

 

Artificial nutrition and hydration in the last week of life in cancer patients. Asystematic literature review of practices and effects.

BACKGROUND: The benefits and burdens of artificial nutrition (AN) and artificial hydration (AH) in end-of-life care are unclear. We carried out a literature review on the use of AN and AH in the last days of life of cancer patients.MATERIALS AND METHODS:We systematically searched for papers in PubMed, CINAHL, PsycInfo and EMBASE. All English papers published between January 1998 and July 2009 that contained data on frequencies or effects of AN or AH incancer patients in the last days of life were included.RESULTS:Reported percentages of patients receiving AN or AH in the last week of life varied from 3% to 53% and from 12% to 88%, respectively. Five studies reported on the effects of AH: two found positive effects (less chronic nausea, less physical dehydration signs), two found negative effects (more ascites, more intestinal drainage) and four found also no effectson terminal delirium, thirst, chronic nausea and fluid overload. No study reported on the sole effect of AN.CONCLUSIONS:Providing AN or AH to cancer patients who are in the last week of life is a frequent practice. The effects on comfort, symptoms and length of survival seem limited. Further research will contribute to better understanding of this important topic in end-of-life care. FREE FULL-TEXT AVAILABLE IN PUBMED

Hydration in palliative care: when, how and why.

Background: a great majority of patients with end-stage disease experience a severily reduced oral intake before death, which is due to a variety of causes related to their cancer or its treatment. Reduced oral intake is perceived by patients and their families with distress because of implications related to eating and hydration. This perception and the fact that there is no evidence-based research to determine how it is best to proceed sourround this issue of much controversy even among palliative care professionals. Objective: to review the existing literature regarding the assessment of hydration in cancer patients, the process of decision making regarding hydration, and the methods and outcomes of artificial hydration. Material and method: we conducted a narrative review using the Pubmed database as well as references within the identified papers, chapters in textbooks of pallaitive medicine and oncology, and previous issues of Medicina Paliativa. The review was conducted both in English and Spanish. Results: terminal cancer patients need less fluid for adequate hydration; however, they are at increased risk for fluid deficiency, often precipitated by minor variations in fluid intake, infection, and other conditions. Conclusion: the main symptoms of dehydration are difficult to interpret due to the presence of multiple symptoms related to cancer and cancer therapy. A careful assessment is needed before a decision is made regarding fluid administration. In unclear cases a brief trial of parenteral hydration may be useful. The subcutaneous and rectal routes are useful alternatives to the intravenous route, particularly in the community setting. If hydration is not considered appropriate a progressive reduction of drugs likely to accumulate in the presence of dehydration – including opioids – is indicated.

Should we hydrate terminally ill patients?

Terminally ill patients frequently have difficulties with fluid and food intake. The indication of artificial hydration in thesepatients has been subject of intense debate in the past years and the clinical practice widely varies, mostly based on anecdotal data and not on clinical evidence about risks and benefits associated to artificial hydration in terminal patients. There are not only technical questions concerning benefits and risks associated to artificial hydration, but also questions related to the ethical principles and values involved. Several topics, such as the effect of artificial hydration alleviating symptoms or reversing neurological alterations as delirium, its life prolonging effect or if it promotes unnecessary suffering, are discussed. In this review we will analyze clinical benefits and risks associated to artificial hydration in terminal patients, making reference to some ethical principles involved. FREE FULL-TEXT AVAILABLE IN PUBMED

Nutrition and hydration for terminal cancer patients in Taiwan

Many medical professionals are still confused when facing the reduction of food or fluid intake in terminal cancer patients. The aim of this study was to assess the frequency and causes of the inability of eating or drinking in terminal cancer patientsand to investigate the use of artificial nutrition and hydration (ANH); the frequency, type, and the extent to which staff found ANH to be ethically justified. Three hundred forty-four consecutive patients with terminal cancer admitted to a palliative care unit in Taiwan were recruited. A structured data collection form was used daily to evaluate clinical conditions, which were analyzed at the time of admission, 1 week after admission and 48 h before death. One hundred thirty-three (38.7%) of the 344 patients were unable to take water or food orally on admission; the leading cause was GI tract disturbances (58.6%). This impaired ability to eat or drink had become worse 1 week after admission (39.1%, P<0.01) and again 48 h before death (60.1%, P<0.001). The total rate of ANH use declined significantly, from 57.0% to 46.9% 1 week after admission ( P<0.001), but rose again to the same level as at admission in the 48 h before death (53.1%, P=0.169). Parenteral hydratation could be reduced significantly 1 week after admission ( P<0.05), but no reduction was possible in the 48 h before death; nor was it possible to reduce the nutrition administered. Multiple Cox regression analysis shows that the administration of ANH, either at admission or 2 days before death, did not have any significant influence on the patients' survival (HR: 0.88, 95% CI: 0.58-1.07; HR: 1.03, 95% CI: 0.76-1.38). In conclusion, sensitive care and continuous communication will probably lessen the use of ANH in terminal cancer patients. We have found it easier to reduce artificial hydratation than artificial nutrition, which corresponds to local cultural practice. Whether or not ANH was used did not influence survival in this study. Thus, the goals of care for terminal cancer patients should be refocused on the promotion of quality of life and preparation for death, rather than in simply making every effort to improve the status of hydratation and nutrition.

Half-Marathon and Full-Marathon Runners' Hydration Practices and Perceptions

Context: The behaviors and beliefs of recreational runners with regard to hydration maintenance are not well elucidated. Objective: To examine which beverages runners choose to drink and why, negative performance and health experiences related to dehydration, and methods used to assess hydration status. Design: Cross-sectional study. Setting: Marathon registration site. Patients or Other Participants: Men (n = 146) and women (n = 130) (age = 38.3 ± 11.3 years) registered for the 2010 Little Rock Half-Marathon or Full Marathon. Intervention(s): A 23-item questionnaire was administered to runners when they picked up their race timing chips. Main Outcome Measure(s): Runners were separated into tertiles (Low, Mod, High) based on z scores derived from training volume, expected performance, and running experience. We used a 100-mm visual analog scale with anchors of 0 (never) and 100 (always). Total sample responses and comparisons between tertile groups for questionnaire items are presented. Results: The High group (58±31) reported greater consumption of sport beverages in exercise environments than the Low (42 ± 35 mm) and Mod (39 ± 32 mm) groups (P < .05) and perceived sport beverages to be superior to water in meeting hydration needs (P < .05) and improving performance during runs greater than 1 hour (P < .05). Seventy percent of runners experienced 1 or more incidents in which they believed dehydration resulted in a major performance decrement, and 45% perceived dehydration to have resulted in adverse health effects. Twenty percent of runners reported monitoring their hydration status. Urine color was the method most often reported (7%), whereas only 2% reported measuring changes in body weight. Conclusions: Greater attention should be paid to informing runners of valid techniques to monitor hydration status and developing an appropriate individualized hydration strategy. FULL-TEXT FREE AT http://www.ingentaconnect.com/content/nata/jat/2011/00000046/00000006/art00001

Inverse relationship between percentage body weight change and finishing time in 643 forty-two-kilometre marathon runners.

OBJECTIVE: The purpose of this study was to determine the relationship between athletic performance and the change in body weight (BW) during a 42 km marathon in a large cohort of runners. METHODS: The study took place during the 2009 Mont Saint-Michel Marathon (France). 643 marathon finishers (560 males and 83 females) were studied. The change in BW during the race was calculated from measurements of each runner's BW immediately before and after the race. RESULTS: BW loss was 2.3 ± 2.2% (mean±SEM) (p<0.01). BW loss was -3.1 ± 1.9% for runners finishing the marathon in less than 3 h; -2.5 ± 2.1% for runners finishing between 3 and 4 h; and -1.8 ± 2.4% for runners who required more than 4 h to complete the marathon. The degree of BW loss was linearly related to 42 km race finishing time (p3% in runners completing the race in less than 3 h. These data are not compatible with laboratory-derived data suggesting that BW loss greater than 2% during exercise impairs athletic performance. They match an extensive body of evidence showing that the most successful athletes in marathon and ultra-marathon running and triathlon events are frequently those who lose substantially more than 3-4% BW during competition.

hanges in body mass alone explain almost all of the variance in the serum sodium concentrations during prolonged exercise. Has commercial influence impeded scientific endeavour?

In 1991, we provided definitive evidence that exercise-associated hyponatraemia (EAH) is caused by abnormal fluid retention in those who overdrink during prolonged exercise, but this finding was ignored. Instead, in 1996, influential guidelines of the American College of Sports Medicine (ACSM) promoted the concept that athletes should drink 'as much as tolerable' duringexercise. What followed was an epidemic of cases of EAH and its associated encephalopathy (EAHE). A recent study funded by the sports drink industry confirms our 1991 finding by showing that 95% of the variance in the serum sodiumconcentration during exercise can be explained by changes in body mass alone. The possibility is that commercial influencedelayed the acceptance of our findings for two decades.

First reported cases of exercise-associated hyponatremia in Asia.

There are no reported cases of exercise-associated hyponatremia (EAH) in tropical Asia. This study aimed to investigate the incidence of EAH at the on-site medical tent and fluid balance in long distance foot races in a warm and humid environment. Body mass was taken before and after the races (42-km marathon; 84-km ultra-marathon). Blood sodium concentration was measured for symptomatic runners admitted to the medical tent. Mean (SD) dry bulb temperature was 29.0 (0.6)°C, relative humidity 89 (2)% and wind speed 0.3 (0.5) m/s. Three out of the 8 symptomatic runners admitted to the medical tent were diagnosed with hyponatremia, with blood sodium concentrations of 134 mmol/L in a 42-km runner, and 131 and 117 mmol/L in two 84-km runners. In the 42-km race, mean % ΔBM was -1.6 (1.2)%, ranging from -5.7 to 1.4%, and 22 runners (7%) gained weight. In the 84-km race, mean % ΔBM was -2.3 (1.7)%, ranging from -8.0 to 1.4%, and 9 runners (8%) gained weight. In addition to the 3 cases of symptomatic hyponatremia observed, 8% of the 84-km runners and 7% of the 42-km runners gained weight during the race. This indicates the need to disseminate advice for the prevention and treatment of EAH for races held in the tropics.

Exercise-associated hyponatremia during winter sports.

Exercise-associated hyponatremia (EAH) is hyponatremia that occurs

Low prevalence of exercise-associated hyponatremia in male 100 km ultra-marathon runners in Switzerland.

We investigated the prevalence of exercise-associated hyponatremia (EAH) in 145 male ultra-marathoners at the '100-km ultra-run' in Biel, Switzerland. Changes in body mass, urinary specific gravity, haemoglobin, haematocrit, plasma [Na(+)], and plasma volume were determined. Seven runners (4.8%) developed asymptomatic EAH. Body mass, haematocrit and haemoglobin decreased, plasma [Na(+)] remained unchanged and plasma volume increased. Δ body mass correlated with both post race plasma [Na(+)] and Δ plasma [Na(+)]. Δ plasma volume was associated with post race plasma [Na(+)]. The athletes consumed 0.65 (0.30) L/h; fluid intake correlated significantly and negatively (r = -0.50, p < 0.0001) to race time. Fluid intake was neither associated with post race plasma [Na(+)] nor with Δ plasma [Na(+)], but was related to Δ body mass. To conclude, the prevalence of EAH was low at ~5% in these male 100 km ultra-marathoners. EAH was asymptomatic and would not have been detected without the measurement of plasma [Na(+)].

Do male 100-km ultra-marathoners overdrink?

PURPOSE: Fluid overload is considered a main risk factor for exercise-associated hyponatremia (EAH). The aim of this study was to investigate the incidence of EAH in ultra-runners at the 100 km ultra-run in Biel, Switzerland. METHODS: Pre- and postrace, body mass, urinary specific gravity, hemoglobin, hematocrit, plasma [Na+], and plasma volume were determined. RESULTS: Of the 145 finishers, seven runners (4.8%) developed asymptomatic EAH. While running, the athletes consumed a total of (median and interquartile ranges) 6.9 (5.1-8.8) L over the 100 km distance, equal to 0.58 (0.41-0.79) L/h. Fluid intake correlated negatively and significantly with race time (r = -.50, P < .0001). Body mass decreased, plasma [Na+] remained unchanged, hematocrit and hemoglobin decreased, and urinary specific gravity increased. Plasma volume increased by 4.6 (-2.3 to 12.8) %. Change in body mass correlated with both postrace plasma [Na+] and Δ plasma [Na+]. Postrace plasma [Na+] correlated to Δ plasma [Na+]. Fluid intake was associated neither with postrace plasma [Na+] nor with Δ plasma [Na+]. Fluid intake was related to Δ body mass (r = .21, P = .012), but not to postrace body mass. Fluid intake showed no correlation to Δ plasma volume. Change in plasma volume was associated with postrace [Na+]. CONCLUSIONS: Incidences of EAH in 100 km ultra-marathoners were lower compared with reports on marathoners. Body mass decreased, plasma volume increased, and plasma [Na+] was maintained. Since fluid intake was related neither to Δ plasma volume nor to Δ plasma [Na+], we assume that factors other than fluid intake maintained body fluid homeostasis.

Physician nutrition and cognition during work hours: effect of a nutrition based intervention.

BACKGROUND: Physicians are often unable to eat and drink properly during their work day. Nutrition has been linked to cognition. We aimed to examine the effect of a nutrition based intervention that of scheduled nutrition breaks during the workday upon physician cognition, glucose, and hypoglycemic symptoms. METHODS: A volunteer sample of twenty staff physicians from a large urban teaching hospital were recruited from the doctors' lounge. During both the baseline and the intervention day, we measured subjects' cognitive function, capillary blood glucose, "hypoglycemic" nutrition-related symptoms, fluid and nutrient intake, level of physical activity, weight, and urinary output. RESULTS: Cognition scores as measured by a composite score of speed and accuracy (T put statistic) were superior on the intervention day on simple (220 vs. 209, p = 0.01) and complex (92 vs. 85, p < 0.001) reaction time tests. Group mean glucose was 0.3 mmol/L lower (p = 0.03) and less variable (coefficient of variation 12.2% vs. 18.0%) on the intervention day. Although not statistically significant, there was also a trend toward the reporting of fewer hypoglycemic type symptoms. There was higher nutrient intake on intervention versus baseline days as measured by mean caloric intake (1345 vs. 935 kilocalories, p = 0.008), and improved hydration as measured by mean change in body mass (+352 vs. -364 grams, p < 0.001). CONCLUSIONS: Our study provides evidence in support of adequate workplace nutrition as a contributor to improved physician cognition, adding to the body of research suggesting that physician wellness may ultimately benefit not only the physicians themselves but also their patients and the health care systems in which they work. FREE FULL-TEXT AVAILABLE IN PUBMED

Hydration Status of Expatriate Manual Workers During Summer in the Middle East.

BACKGROUND: Implicit in all indices used for risk assessment in the prevention of heat stress is the assumption that workers are healthy and well hydrated; studies in Australian mine workers have shown that this is not the case. Where workers are poorly hydrated, the level of protection offered by management strategies based primarily on environmental monitoring is compromised. OBJECTIVES: To investigate the hydration status of expatriate workers during summer in a range of work environments in the Middle East as large numbers of expatriate workers are employed as manual laborers in construction and other industries under extreme heat stress conditions where heat illness is a significant concern. The aim was to ascertain whether the generally inadequate hydration status, previously documented in Australian workers, is also an issue in these workers and make practical recommendations for control. METHODS: Studies were carried out at four sites to document the hydration status of exposed workers in different workplaces using urine specific gravity at three time points over two different work shifts. RESULTS: Although the workers were found in general to be better hydrated than their Australian counterparts, a high proportion were still found to be inadequately hydrated both on presentation for work and throughout the shift. Hydration status did not alter greatly over the course of the day at individual or group level. CONCLUSIONS: Interventions are required to ensure that workers in extreme heat stress conditions maintain adequate levels of hydration. Failure to do so reduces the protection afforded by heat stress indices based on environmental monitoring. FREE FULL-TEXT AVAILABLE IN PUBMED

Effect of bariatric surgery on normal and abnormal renal function.

BACKGROUND: Obesity has been associated with hypertension, diabetes mellitus, and metabolic syndrome, risk factors for chronic kidney disease. In addition, obesity has been found to have an independent, negative effect on renal function and the progression of renal insufficiency. METHODS: The serum creatinine (CR) in 813 patients who had undergone obesity surgery from 2003 to 2009 at a large academic medical center and had been followed up for ≥24 months was retrospectively monitored. Renal function, as measured by the CR level, was assessed at baseline and at 6, 12, and ≥24 months of follow-up. The groups were stratified by the baseline CR as follows: normal (CR 1.6 mg/dL). RESULTS:Of the 813 patients, 757 had a CR <1.3 mg/dL at baseline. Of those 757 patients, 97.6% had maintained a CR of 1.6 mg/dL (n = 757) at 6 months of follow-up. At 1 year of follow-up, 99% had maintained a CR of 1.3% (n = 509). At 2 years of follow-up, 100% had a CR value of 1.6 mg/dL) before weight loss surgery. Examination of the CR values at ≥2 years after weight loss surgery demonstrated that 76.7% had a normal CR level, 12.5% had mild impairment, and 10.7% had moderate impairment. CONCLUSION: Bariatric surgery does not have a negative effect on renal function as measured by the CR, whether CR at baseline is <1.3 or ≥1.3 mg/dL when monitored for ≥24 months. For those with impaired renal function and a CR ≥1.3 mg/dL, improvement in CR was seen in 76.7% at ≥2 years postoperatively, at a point at which the weight loss velocity, hydration, and nutritional status have stabilized. The weight loss associated with bariatric surgery could potentially have a positive effecton renal function at ≥24 months, such as was found in the present study by a stable or reduced CR level. The etiology for this might be a direct effect of weight loss on impaired renal function or an indirect effect by reducing the rates of co-morbidities, such as diabetes mellitus and hypertension, both risk factors for renal disease. Additional prospective studies, including weight-matched controls, are needed.

The effect of racial origin on total body water volume in peritoneal dialysis patients.

ACKGROUND AND OBJECTIVES: Peritoneal dialysis adequacy is typically assessed by urea clearance corrected for total body water (TBW) on the basis of anthropomorphic equations, which do not readily take into account changes in body composition, which may vary between ethnic groups. To determine whether ethnicity could affect estimates of peritoneal dialysis adequacy, we compared TBW estimated by anthropomorphic equations and that measured by multi-frequency bio-impedance spectroscopy. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We calculated TBW in 600 healthy adult peritoneal dialysis outpatient attending two tertiary university hospitals serving an inner-city multiethnic population who had TBW measured by multi-frequency bio-impedance spectroscopy performed. RESULTS: 600 adult peritoneal dialysis patients were studied: mean age, 56.7 ± 0.6 years; 54.2% men; 29.7% diabetic; mean body mass index, 26.1 ± 0.2; 47.3% Caucasian; 29.2% South Asian; 12.8% African/Afro-Caribbean. Total body water was calculated using several anthropomorphic equations and was higher than that calculated MEASURED BY MF-BIS for all ethnic groups, apart from African/Afro-Caribbeans, with the greatest difference between Watson calculated TBW and multi-frequency bioelectrical impedance spectroscopy 12.3 ± 0.6% for the South Asians, 9.0 ± 2.6% for Far Eastern Asians, 2.8 ± 0.6% Caucasians, and -0.2 ± 1.5% for African/Afro-Caribbeans. CONCLUSIONS: In this United Kingdom-based multiethnic population, body composition differed particularly for the South Asian patients compared with Caucasians and African/Afro-Caribbeans. Overestimation of TBW by anthropomorphic-based equations would lead to a lower calculation of Kt/V(urea), which may lead to changes in peritoneal dialysis prescription to achieve clinical standard targets and also affect studies examining the relationship between Kt/V and survival.

The pitfall "dehydration" and hyponatremia

Hyponatremia represents a very common disturbance in hospitalized eldery. It correlates with delirium, falls, and intrahospital mortality. Often hyponatremia is ignored or missclassified. The represented algorithm is based on only a few parameters: serum and urine osmolality, and sodium. Treatment of the underlying causes of hyponatremia, e.g., cessation of medications and polypharmacy, is essential. The syndrome of inadequate secretion of antidiuretic hormone (SIADH; hypotonic isovolemic hyponatremia) is also considered.

Management guidelines for acute infective diarrhoea / gastroenteritis in infants.

Background. Acute onset vomiting and diarrhoea is one of the most common illnesses of infancy, and is second only to respiratory illnesses as a cause of childhood deaths worldwide. Existing guidelines for management of diarrhoea are often ignored in public and private practice, possibly because of a perception that the guidelines are too simple, or because of expectations of the need to give 'real' drug therapy to stop diarrhoea. Objectives. This guideline provides a problem-based approach to the basics of present-day management of acute gastroenteritis, and discusses the evidence for the recommendations. Recommendations. Each episode of diarrhoea must be seen as an opportunity for caregiver education in the prevention of the illness, in the 'what' and 'how' of oral rehydration and re-feeding, and in the recognition of when to seek help. The vast majority of patients recover rapidly, but serious complications do occur, and must be recognised and managed correctly. Validation. The guidelines are endorsed by the Paediatric Management Group (PMG) in South Africa. Conclusion. The aim of management is to help the child to maintain or regain hydration, and to recover from diarrhoea, with careful attention to adequate oral rehydration and judicious re-feeding.

Replacing caloric beverages with water or diet beverages for weight loss in adults: main results of the Choose Healthy Options Consciously Everyday (CHOICE) randomized clinical trial.

BACKGROUND: Replacement of caloric beverages with noncaloric beverages may be a simple strategy for promoting modest weight reduction; however, the effectiveness of this strategy is not known. OBJECTIVE: We compared the replacement of caloric beverages with water or diet beverages (DBs) as a method of weight loss over 6 mo in adults and attention controls (ACs). DESIGN: Overweight and obese adults [n = 318; BMI (in kg/m(2)): 36.3 ± 5.9; 84% female; age (mean ± SD): 42 ± 10.7 y; 54% black] substituted noncaloric beverages (water or DBs) for caloric beverages (≥200 kcal/d) or made dietary changes of their choosing (AC) for 6 mo. RESULTS: In an intent-to-treat analysis, a significant reduction in weight and waist circumference and an improvement in systolic blood pressure were observed from 0 to 6 mo. Mean (±SEM) weight losses at 6 mo were -2.5 ± 0.45% in the DB group, -2.03 ± 0.40% in the Water group, and -1.76 ± 0.35% in the AC group; there were no significant differences between groups. The chance of achieving a 5% weight loss at 6 mo was greater in the DB group than in the AC group (OR: 2.29; 95% CI: 1.05, 5.01; P = 0.04). A significant reduction in fasting glucose at 6 mo (P = 0.019) and improved hydration at 3 (P = 0.0017) and 6 (P = 0.049) mo was observed in the Water group relative to the AC group. In a combined analysis, participants assigned to beverage replacement were 2 times as likely to have achieved a 5% weight loss (OR: 2.07; 95% CI: 1.02, 4.22; P = 0.04) than were the AC participants. CONCLUSIONS: Replacement of caloric beverages with noncaloric beverages as a weight-loss strategy resulted in average weight losses of 2% to 2.5%. This strategy could have public health significance and is a simple, straightforward message. This trial was registered at clinicaltrials.gov as NCT01017783. FREE FULL-TEXT IN PUBMED.

Maternal hydration therapy improves the quantity of amniotic fluid and the pregnancy outcome in third-trimester isolated oligohydramnios: a controlled randomized institutional trial.

Objectives- Amniotic fluid is important for the maintenance of fetal well-being; therefore, an amniotic fluid deficiency, ie, oligohydramnios, can have multiple impacts on the prognosis of the pregnancy. In some cases, there are no evident fetal or maternal causes, and the condition is called isolated oligohydramnios. The aim of our study was to validate maternal intravenous and oral hydration therapy as a means for improvement of isolated oligohydramnios in the third trimester of pregnancy. Methods- We conducted a prospective randomized controlled study on pregnancies complicated by idiopathic oligohydramnios (group A, 66 women) with a control group of women with normal pregnancies without oligohydramnios (group B, 71 women). Oligohydramnios was diagnosed using the amniotic fluid index (AFI; <5 cm). Sonographic examinations were performed with a convex 3.5-MHz probe. Group A underwent 6 days of intravenous infusion of 1500 mL of an isotonic solution per day. An AFI measurement, a nonstress test, and a fetal biophysical profile were performed at 0 and 7 days. Group A was randomized into subgroups A1 and A2. Subgroup A1 was prescribed home oral hydration therapy of 1500 mL/d and subgroup A2 2500 mL/d. We considered the AFI to compare the effectiveness of the therapy. Results- General features did not reveal any significant differences between the two groups. In group A, the mean AFI ± SD at recruitment was 39.68 ± 11.11 mm; in group B, it was 126.92 ± 10.59 mm (P <.001). In group A, the mean AFI at 7 days was 77.70 ± 15.03 mm; in group B, it was unchanged. In subgroup A1, the mean AFI at birth was 86.21 ± 16.89 mm; in subgroup A2, it was 112.45 ± 14.92 mm (P < .001). Conclusions- Our data show that in pregnancies complicated by isolated oligohydramnios, hydration therapy significantly improves the quantity of amniotic fluid.

What is the cell hydration status of healthy children in the USA? Preliminary data on urine osmolality and water intake.

OBJECTIVE: Hyperosmotic stress on cells limits many aspects of cell function, metabolism and health. International data suggest that schoolchildren may be at risk of hyperosmotic stress on cells because of suboptimal water intake. The present study explored the cell hydration status of two samples of children in the USA. DESIGN: Cross-sectional study describing the urine osmolality (an index of hyperosmotic cell shrinkage) and water intake of convenience samples from Los Angeles (LA) and New York City (NYC). SETTING: Each participant collected a urine sample at an outpatient clinic on the way to school on a weekday morning in spring 2009. Each was instructed to wake, eat, drink and do as usual before school, and complete a dietary record form describing the type and amounts of all foods and beverages consumed after waking, before giving the sample. SUBJECTS: The children (9-11 years) in LA (n 337) and NYC (n 211) considered themselves healthy enough to go to school on the day they gave the urine sample. RESULTS: Elevated urine osmolality (>800 mmol/kg) was observed in 63 % and 66 % of participants in LA and NYC, respectively. In multivariable-adjusted logistic regression models, elevated urine osmolality was associated with not reporting intake of drinking water in the morning (LA: OR = 2·1, 95 % CI 1·2, 3·5; NYC: OR = 1·8, 95 % CI 1·0, 3·5). Although over 90 % of both samples had breakfast before giving the urine sample, 75 % did not drink water. CONCLUSIONS: Research is warranted to confirm these results and pursue their potential health implications.

Oral motor performance in spastic cerebral palsy individuals: are hydration and nutritional status associated?

When we give advice on assessment and maintenance of hydration, we are usually mindful of the barriers to maintenance of good hydration status. However, it is easy to forget that some individuals face specific challenges. Some individuals with neurological or muscle damage, including those with cerebral palsy (CP), have a range of disorders that are may be accompanied by impaired coordination of movements, and this may affect oral motor performance of mastication and swallowing as well as of speech. Previous studies have shown that children with CP may have impaired hydration status. The authors of the present paper reasoned that this could be due either to a low amount of liquid offered to these individuals, or to compromised oral motor performance that may hamper the liquid diet intake. They further reasoned that if hypohydration status was due to insufficient fluid being offered by their caregivers, then poor nutritional status would also be likely. They recruited 43 CP individuals aged 11–19 y: 21 were classifies as subfunctional using the Oral Motor Assessment Scale, and the other 22 were classified as functional. Hydration status was assessed by salivary markers (flow rate and osmolality) and blood samples were collected to evaluate complete blood count, total protein, albumin⁄globulin ratio and transferrin levels as markers of nutritional status. The subfunctional CP group had a lower salivary flow rate (P < 0.01) and higher salivary osmolality (P < 0.001) than the functional group. Blood markers of nutritional status were all within the normal range. The authors concluded that cerebral palsy individuals appear to present impaired adequate hydration due to compromised oral motor performance. We should be mindful when assessing any group who may have difficulty in eating and drinking that one possible outcome may be an impaired hydration status. Assessment of markers of nutritional status may not give any indication of hydration status in some of these groups, and hydration status should be assessed separately.

Factors Influencing Fluid Intake Behavior Among Kidney Stone Formers.

PURPOSE: We determined factors influencing the behavior of patients with kidney stones in the prevention of recurrent stones. MATERIALS AND METHODS: Patients with stones from an academic and a community practice were recruited for key informant interviews and focus groups. Groups were guided based on the framework of the health belief model. Content analysis was done on transcriptions using qualitative data analysis software. RESULTS: Key informant interviews were completed with 16 patients and with a total of 29 subjects in 5 focus groups. Content analysis revealed that patients were highly motivated to prevent stones. The minimum level of perceived benefit for adopting the behavior change varied among patients and the behaviors proposed. An important strategy to increase fluid intake was insuring availability with containers. Patients were more consistently confident in the ability to increase fluid, in contrast to ingesting medicine or changing the diet. While barriers to increasing fluid were multifactorial among individuals, the barriers aligned into 3 progressive stages that were associated with distinct patient characteristics. Stage 1 barriers included not knowing the benefits of fluid or not remembering to drink. Stage 2 barriers included disliking the taste of water, lack of thirst and lack of availability. Stage 3 barriers included the need to void frequently and related workplace disruptions. CONCLUSIONS: Patients with kidney stones are highly motivated to prevent recurrence and were more amenable to fluid intake change than to another dietary or pharmaceutical intervention. Barriers preventing fluid intake success aligned into 3 progressive stages. Tailoring fluid intake counseling based on patient stage may improve fluid intake behavior.

 

Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men.

ABSTRACT: BACKGROUND: Sport drinks are ubiquitous within the recreational and competitive fitness and sporting world. Most are manufactured and artificially flavored carbohydrate-electrolyte beverages. Recently, attention has been given to coconut water, a natural alternative to manufactured sport drinks, with initial evidence indicating efficacy with regard to maintaining hydration. We compared coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men. Methods: Following a 60- minute bout of dehydrating treadmill exercise, 12 exercise-trained men(26.6+/-5.7 yrs) received bottled water (BW), pure coconut water (VitaCoco(R): CW), coconut water from concentrate (CWC), or a carbohydrate-electrolyte sport drink (SD) [a fluid amount based on body mass loss during the dehydrating exercise] on four occasions (separated by at least 5 days) in a random order, single blind (subject and not investigators), cross-over design. Hydration status (body mass, fluid retention, plasma osmolality, urine specific gravity) and performance (treadmill time to exhaustion; assessed after rehydration) were determined during the recovery period. Subjective measures of thirst, bloatedness, refreshed, stomach upset, and tiredness were also determined using 5-point visual analog scale. Results: Subjects lost approximately 1.7 kg (~2% of body mass) during the dehydrating exercise and regained this amount in a relatively similar manner following consumption of all conditions. No differences were noted between coconut water (CW or CWC) and SD for any measures of fluid retention (p>0.05). Regarding exercise performance, no significant difference (p>0.05) was noted between BW (11.9+/-5.9 min), CW (12.3+/-5.8 min), CWC (11.9+/-6.0 min), and SD (12.8+/-4.9 min). In general, subjects reported feeling more bloated and experienced greater stomach upset with the CW and CWC conditions. Conclusion: All beverages are capable of promoting rehydration. Little difference is noted 3 between the four tested conditions with regard to markers of hydration or exercise performance in a sample of young, healthy men. Additional study inclusive of a more demanding dehydration protocol, as well as a time trial test as the measure of exercise performance, may more specifically determine the efficacy of these beverages on enhancing hydration and performance following dehydrating exercise. FREE FULL-TEXT AVAILABLE IN PUBMED.

Dehydration influences mood and cognition: a plausible hypothesis?

The hypothesis was considered that a low fluid intake disrupts cognition and mood. Most research has been carried out on young fit adults, who typically have exercised, often in heat. The results of these studies are inconsistent, preventing any conclusion. Even if the findings had been consistent, confounding variables such as fatigue and increased temperature make it unwise to extrapolate these findings. Thus in young adults there is little evidence that under normal living conditions dehydration disrupts cognition, although this may simply reflect a lack of relevant evidence. There remains the possibility that particular populations are at high risk of dehydration. It is known that renal function declines in many older individuals and thirst mechanisms become less effective. Although there are a few reports that more dehydrated older adults perform cognitive tasks less well, the body of information is limited and there have been little attempt to improve functioning by increasing hydration status. Although children are another potentially vulnerable group that have also been subject to little study, they are the group that has produced the only consistent findings in this area. Four intervention studies have found improved performance in children aged 7 to 9 years. In these studies children, eating and drinking as normal, have been tested on occasions when they have and not have consumed a drink. After a drink both memory and attention have been found to be improved. FREE FULL-TEXT AVAILABLE IN PUBMED.

Importance of normohydration for the long-term survival of haemodialysis patients.

BACKGROUND: Fluid overload and hypertension are among the most important risk factors for haemodialysis (HD) patients. The aim of this study was to analyse the impact of fluid overload for the survival of HD patients by using a selected reference population from Tassin. METHODS: A positively selected HD population (n = 50) from Tassin (Lyon-France) was used as a reference for fluid status and all-cause mortality. This population was compared to one dialysis centre from Giessen (Germany) which was separated into a non-hyperhydrated (n = 123) and a hyperhydrated (n = 35) patient group. The hydration status (ΔHS) of all patients was objectively measured with whole-body bioimpedance spectroscopy in 2003. All-cause mortality was analysed after a 6.5-year follow-up.RESULTS: Most of the reference patients from Tassin were normohydrated (ΔHS = 0.25 ± 1.15 L) at the start of the HD session. The hydration status of the Tassin patients was not different to the non-hyperhydrated Giessen patients (ΔHS = 0.8 ± 1.1 L) but significantly lower than in the hyperhydrated Giessen group (ΔHS = 3.5 ± 1.2 L). Multivariate adjusted all-cause mortality was significantly increased in the hyperhydrated patient group (hazard ratio = 3.41)- no difference in mortality could be observed between the Tassin and the non-hyperhydrated group from Giessen-even considering the fact that Tassin patients presented a significantly lower blood pressure. CONCLUSIONS: Fluid overload has a very high predictive value for all-cause mortality and seems to be one of the major killers in the HD population. Patients might strongly benefit from active management of fluid overload.

Hydration Strategies of Runners in the London Marathon.

OBJECTIVE: To explore the hydration strategies of marathon runners, their sources of information and knowledge about fluid intake in the marathon, and their understanding of exercise-associated hyponatremia (EAH). DESIGN: Anonymized questionnaire. SETTING: London Marathon. PARTICIPANTS: Marathon race participants. MAIN OUTCOME MEASURES: Responses regarding planned fluid consumption, volume to be consumed, volume of water and sports drink bottles, and the number of stations from which planning to take a drink. In addition, sources of information about appropriate drinking and understanding of hyponatremia. RESULTS: In total, 93.1% of the runners had read or been told about drinking fluids on marathon day and 95.8% of competitors had a plan regarding fluid intake. However, 12% planned to drink a volume large enough to put them at higher risk of EAH. Only 21.7% knew the volumes of water and sports drink bottles available on the course; 20.7% were planning to take a drink from all 24 water stations. Only 25.3% planned to drink according to thirst. Although 68.0% of the runners had heard of hyponatremia or low sodium levels, only 35.5% had a basic understanding of its cause and effects. CONCLUSIONS: Marathon runners lack knowledge about appropriate fluid intake to prevent hyponatremia on race day. Twelve percent reported drinking strategies that put them at risk of EAH. Effective educational interventions are still necessary to prevent overdrinking during marathons.

Oral Rehydration of the Pediatric Patient with Mild to Moderate Dehydration.

Abstract not available

Dehydration in children with diabetic ketoacidosis: a prospective study.

Objectives: To investigate the association between the degree of patient dehydration on presentation with diabetic ketoacidosis (DKA) and clinical and laboratory parameters obtained on admission. Design Prospective descriptive study. Setting A tertiary care children's hospital. Patients Thirty-nine paediatric patients (1 month-16 years) presenting with 42 episodes of DKA. Intervention Clinical and biochemical variables were collected on admission. Dehydration was calculated by measuring acute changes in body weight during the period of illness. All patients were treated according to a previously established protocol. Main outcome measures Magnitude of dehydration, defined as % loss of body weight (LBW), was determined by the difference in body weight obtained at presentation and at discharge. The relationship between the magnitude of dehydration and the clinical assessment and biochemical parameters was examined. Results The median (25th-75th centiles) magnitude of dehydration at presentation was 5.7% (3.8-8.3%) (mean±SD 6.8±5%). Neither the initial clinical assessment nor the comprehensive biochemical profile at admission correlated with the magnitude of dehydration. Despite considerable variation in the degree of dehydration and biochemical disequilibrium, all patients recovered from DKA within 24 h with a standardised therapeutic approach. Furthermore, the rapidity of patient recovery did not correlate with the magnitude of dehydration on presentation or the amount of fluid administered (median (25th-75th centiles) 48.8 ml/kg (38.5-60.3)) in the first 12 h. Conclusion The magnitude of dehydration in DKA is not reflected by either clinical or biochemical parameters. These findings need confirmation in larger studies.

Effect of ramadan fasting on urinary risk factors for calculus formation.

Introduction. Even though dehydration could aggravate formation of urinary calculi, the effects of fluid and food restriction on calculus formation is not thoroughly defined. The purpose of this study is to evaluate the effects of fluid and food restriction in Ramadan fasting on urinary factors in kidney and urinary calculus formation. Materials and Methods. Fifty-seven men aged 30 to 55 years old, including 37 recurrent calcium calculus formers and 20 with no history of kidney calculi were evaluated for blood tests, ultrasonography investigations, urinalysis, urine culture, and also 24-hour urine collection test. Metabolites including calcium, oxalate, citrate, uric acid, magnesium, phosphate, potassium, sodium, and creatinine were measured before and during Ramadan fasting. The values of calculus-precipitating solutes as well as inhibitory factors were documented thoroughly. Results. Total excretion of calcium, phosphate, and magnesium in 24-hour urine and also urine volume during fasting were significantly lower than those in the nonfasting period. Urine concentration of calcium during fasting was significantly lower than nonfasting (P < .001). Urine concentrations of uric acid, citrate, phosphate, sodium, and potassium during fasting were significantly higher than nonfasting. Uric acid supersaturation was accentuated, and calcium phosphate supersaturation was decreased significantly during fasting. There was no significant increase in calcium oxalate supersaturation during the fasting period. Conclusions. Fasting during Ramadan has different effects on total excretion and concentrations of urinary precipitate and inhibitory factors contributing to calculus formation. We did not find enough evidence in favor of increased risks of calculus formation during Ramadan fasting. FREE FULL-TEXT AVAILABLE IN PUBMED

Heat stress and dehydration in kendo.

IM: This study aimed to analyze sweat rate, water percentage alteration, and temperature variation during kendo practice in order to relate the thermal stress induced by such sports and draw recommendations for its secure practice. METHODS: Participants were 12 male individuals. The studied variables were: age, weight, stature, body mass index, fat percentage, water loss percentage, tympanic temperature, and sweat rate. Measures were obtained in one day of 120 min practice (T: 24.1±2.5 °C; RH: 73±8.5%) using obligatory training equipment. RESULTS: The age of participants was on average 26±6.2 years, stature 1.8±0.03 m, weight 78±13.7 kg, BMI 24.12±4.03 kg/m² and fat percentage 15.7±5.1%. Weight and temperature final values were significantly different from the initial ones (P<0.01). Estimated sweat rate was 0.35 L.h-1 (95% CI = [0.299; 0.400]) and estimated percentage of water loss was 0.946% (95% CI = [0.694; 1.174]). CONCLUSION: Kendo practice using obligatory equipment significantly increases temperature, even when sweat rate and water loss percentage are low. The almost complete obstruction of the evaporative surface leads to heat accumulation, which may result in risks comparable to those of American football players. Thus, preventive measures must be established to minimize the risks of the combination among environment (tropical climate), equipment (bogu) and the high physiological demand of this sport in order to prevent greater damages to the health of practitioners.

Effect of acute mild dehydration cognitive-motor performance in golf.

Whether mild dehydration (-1-3% ΔBM) impairs neurophysiological function during sport-specific cognitive-motor performance has yet to be fully elucidated. To investigate this within a golfing context, seven low-handicap players (age: 21 ± 1.1 yrs; mass: 76.1 ± 11.8kg; stature: 1.77 ± 0.07m; handicap: 3.0 ± 1.2) completed a golf-specific motor and cognitive performance task in a euhydrated (EC) and dehydrated (DC) condition (randomised counter-balanced design; 7 day interval). Dehydration was controlled using a previously effective 12-hour fluid restriction, monitored through body mass change (ΔBM) and urine colour assessment (UCOL). Mild dehydration reduced mean body mass by 1.5 ± 0.5% (P = 0.01), with UCOL increasing from 2 (EC) to 4 (DC) (P = 0.02). Mild dehydration significantly impaired motor performance, expressed as shot distance (114.6 vs. 128.6m; P < 0.001) and off target accuracy (7.9 vs. 4.1m; P = 0.001). Cognitive performance, expressed as mean error in distance judgement to target increased from 4.1 ± 3.0m (EC) to 8.8 ± 4.7m (DC) (P < 0.001). Findings support previous research that indicates mild dehydration (-1-2% ΔBM) significantly impairs cognitive-motor task performance. This study is the first to show that mild dehydration can impair distance, accuracy and distance judgement during golf performance.

Effect of acute mild dehydration cognitive-motor performance in golf.

Whether mild dehydration (-1-3% ΔBM) impairs neurophysiological function during sport-specific cognitive-motor performance has yet to be fully elucidated. To investigate this within a golfing context, seven low-handicap players (age: 21 ± 1.1 yrs; mass: 76.1 ± 11.8kg; stature: 1.77 ± 0.07m; handicap: 3.0 ± 1.2) completed a golf-specific motor and cognitive performance task in a euhydrated (EC) and dehydrated (DC) condition (randomised counter-balanced design; 7 day interval). Dehydration was controlled using a previously effective 12-hour fluid restriction, monitored through body mass change (ΔBM) and urine colour assessment (UCOL). Mild dehydration reduced mean body mass by 1.5 ± 0.5% (P = 0.01), with UCOL increasing from 2 (EC) to 4 (DC) (P = 0.02). Mild dehydration significantly impaired motor performance, expressed as shot distance (114.6 vs. 128.6m; P < 0.001) and off target accuracy (7.9 vs. 4.1m; P = 0.001). Cognitive performance, expressed as mean error in distance judgement to target increased from 4.1 ± 3.0m (EC) to 8.8 ± 4.7m (DC) (P < 0.001). Findings support previous research that indicates mild dehydration (-1-2% ΔBM) significantly impairs cognitive-motor task performance. This study is the first to show that mild dehydration can impair distance, accuracy and distance judgement during golf performance.

 

 

High-sweat Na(+) in cystic fibrosis and healthy individuals does not diminish thirst during exercise in the heat

Brown, M. B., McCarty, N. A., Millard-Stafford, M. . Am J Physiol Regul Integr Comp Physiol. 2011;301(4):R1177-85

The factors that govern thirst in exercising individuals are not completely understood, but may be particularly important in the light of recommendations that active individuals should drink according to the dictates of thirst rather than using any drinking strategy based on known or predicted sweat losses. It is clear that both blood volume and plasma osmolality, which is determined to a large degree by the plasma sodium concentration, are important factors. These two parameters, however, may change independently of each other during exercise because of differences in the electrolyte content of sweat. Again, the primary electrolyte lost is sodium, but in contrast to the plasma sodium concentration which is normally closely controlled at about 140 mmol/l, the sodium concentration of sweat typically ranges from about 10-80 mmol/l in any population sample. A few healthy individuals may be found with even higher sweat sodium concentrations, but a very high sweat sodium concentration is normally an indication of cystic fibrosis (CF).

The normal response to sweating is a reduction in the plasma volume and an increase in the circulating sodium concentration. When sweat has a very high sodium content and when large sweat losses are incurred, it might be expected that the reduction in blood volume and the increase in sodium concentration would both be less than expected. Brown et al set out to investigate this and to assess the effects on the thirst response. They recruited groups of healthy subjects with high-sweat sodium concentration (91 +/- 17 mmol/l), whom they called salty sweaters  (SS), Controls with average sweat sodium concentration (44 +/- 10 mmol/l), and physically active CF patients with very high sweat sodium concentration (133 +/- 6 mmol/l) cycled in the heat without drinking until they had lost 3% of their starting body mass. The increase in serum osmolality was less (P < 0.05) in CF (6.1 +/- 4.3 mosmol/kg) and SS (8.4 +/- 3.0 mosmol/kg) than in Control (14.8 +/- 3.5 mosmol/kg). The relative reduction in plasma volume was greater (P < 0.05) in CF (19.3 +/- 4.5%) and SS (18.8 +/- 3.1%) than in the Control subjects (-14.3 +/- 2.3%).

Subjective ratings of thirst were measured during the exercise at different levels of dehydration, but were not different among the three groups. However, when subjects were allowed unrestricted access to drinks in the post-exercise period, the ad libitum fluid replacement was substantially less (by 40%) in the CF subjects than in SS and Control. It seems from these results that thirst is appropriately maintained during exercise in the heat as a linear function of the amount of water lost in sweat, with relative contributions from hyperosmotic and hypovolemic stimuli dependent upon the magnitude of salt lost in sweat. The authors concluded that individuals with CF exhibit lower ad libitum fluid restoration following dehydration, which may reflect physiological cues directed at preservation of salt balance over volume restoration.

 

Hydration and nutrition at the end of life: a systematic review of emotional impact, perceptions, and decision-making among patients, family, and health care staff.

BACKGROUND: Decrease in oral intake, weight loss, and muscular weakness in the last phases of a terminal illness, particularly in the context of the cachexia-anorexia syndrome, can be an important source of anxiety for the triad of patient, family, and health staff. METHODS: The present literature review examines the emotional impact of reduced oral intake as well as perceptions and attitudes toward assisted nutrition and hydration for terminally ill patients at the end of life, among patients, family, and health care staff. We have identified the ways in which emotional and cultural factors influence decision-making about assisted nutrition and hydration. RESULTS: Lack of information and misperceptions of medically assisted nutrition and hydration can play a predominant role in the decision to begin or suspend nutritional or hydration support. CONCLUSIONS: Our literature review reveals that these social, emotional, and clinical misperception elements should be considered in the decision-making processes to help the triad develop functional forms of care at this final stage of life.

Treatment and prevention of kidney stones: an update.

Kidney stones are associated with chronic kidney disease. Preventing recurrence is largely specific to the type of stone (e.g., calcium oxalate, calcium phosphate, cystine, struvite [magnesium ammonium phosphate]), and uric acid stones); however, even when the stone cannot be retrieved, urine pH and 24-hour urine assessment provide information about stone-forming factors that can guide prevention. Medications, such as protease inhibitors, antibiotics, and some diuretics, increase the risk of some types of kidney stones, and patients should be counseled about the risks of using these medications. Managing diet, medication use, and nutrient intake can help prevent the formation of kidney stones. Obesity increases the risk of kidney stones. However, weight loss could undermine prevention of kidney stones if associated with a high animal protein intake, laxative abuse, rapid loss of lean tissue, or poor hydration. For prevention of calcium oxalate, cystine, and uric acid stones, urine should be alkalinized by eating a diet high in fruits and vegetables, taking supplemental or prescription citrate, or drinking alkaline mineral waters. For prevention of calcium phosphate and struvite stones, urine should be acidified; cranberry juice or betaine can lower urine pH. Antispasmodic medications, ureteroscopy, and metabolic testing are increasingly being used to augment fluid and pain medications in the acute management of kidney stones.

Water in summer heat, but how much?

Insufficient drinking during summer heat may lead to dehydration, but excessive drinking, on the other hand, may also be dangerous. In dehydration, the kidneys decrease urinary secretion by maximally concentrating the urine. When this first-line defense for dehydration has been utilized, thirst will slowly appear and the dehydration will eventually be compensated by drinking. In summer heat, decreased urine volumes are thus the first sign of dehydration and need of drinking. There is thus no use of waiting for the feeling of thirst in summer heat, as rehydration is then already long overdue.

High-sweat Na+ in cystic fibrosis and healthy individuals does not diminish thirst during exercise in the heat.

Sweat Na(+) concentration ([Na(+)]) varies greatly among individuals and is particularly high in cystic fibrosis (CF). The purpose of this study was to determine whether excess sweat [Na(+)] differentially impacts thirst drive and other physiological responses during progressive dehydration via exercise in the heat. Healthy subjects with high-sweat [Na(+)] (SS) (91.0 ± 17.3 mmol/l), Controls with average sweat [Na(+)] (43.7 ± 9.9 mmol/l), and physically active CF patients with very high sweat [Na(+)] (132.6 ± 6.4 mmol/l) cycled in the heat without drinking until 3% dehydration. Serum osmolality increased less (P < 0.05) in CF (6.1 ± 4.3 mosmol/kgH(2)O) and SS (8.4 ± 3.0 mosmol/kgH(2)O) compared with Control (14.8 ± 3.5 mosmol/kgH(2)O). Relative change in plasma volume was greater (P < 0.05) in CF (-19.3 ± 4.5%) and SS (-18.8 ± 3.1%) compared with Control (-14.3 ± 2.3%). Thirst during exercise and changes in plasma levels of vasopressin, angiotensin II, and aldosterone relative to percent dehydration were not different among groups. However, ad libitum fluid replacement was 40% less, and serum NaCl concentration was lower for CF compared with SS and Control during recovery. Despite large variability in sweat electrolyte loss, thirst appears to be appropriately maintained during exercise in the heat as a linear function of dehydration, with relative contributions from hyperosmotic and hypovolemic stimuli dependent upon the magnitude of salt lost in sweat. CF exhibit lower ad libitum fluid restoration following dehydration, which may reflect physiological cues directed at preservation of salt balance over volume restoration.

Increased insensible water loss contributes to aging related dehydration.

Dehydration with aging is attributed to decreased urine concentrating ability and thirst. We further investigated by comparing urine concentration and water balance in 3, 18 and 27 month old mice, consuming equal amounts of water. During water restriction, 3 month old mice concentrate their urine sufficiently to maintain water balance (stable weight). 18 month old mice concentrate their urine as well, but still lose weight (negative water balance). 27 month old mice do not concentrate their urine as well and lose even more weight than the 18 month old mice, indicating a larger negative water balance. Negative water balance in older mice is accompanied by increased vasopressin excretion, providing further evidence of dehydration. All 3 groups maintain water balance while consuming only the water in gel food containing 56% water. However, both older groups excrete a smaller volume of urine of higher osmolality, indicating greater extra urinary water loss. Since their feces also contain less water, the excess water lost by the older mice apparently is through other routes, presumably insensible loss through the respiratory tract and skin. The greater insensible water loss occurs at an earlier age (18 months) than decreased urine concentrating ability (27 months). We propose that insensible water loss through skin and respiration increases with age, making a major contribution to aging related dehydration.

Effect of exercise-induced dehydration on time-trial exercise

OBJECTIVE: To use the meta-analytical procedures to determine the magnitude of the effect of exercise-induced dehydration (EID) upon time-trial (TT) exercise performance. METHODS: Studies were located via database searches and cross-referencing. TT performance outcomes were converted to mean percentage changes in power output. Random-effects model meta-regressions, analogue to the ANOVA and weighted mean effect summaries were used to delineate the effect of the EID-associated body weight (BW) loss on TT performance. RESULTS: Five research articles, all using cycling TTs, were included, producing 13 effect estimates and representing 39 subjects. The mean ambient temperature, relative humidity, exercise intensity and duration of the exercise trials were 26.0 ¬± 6.7¬∞C, 61 ¬± 9%, 68 ¬± 14% of VO(2max) and 86 ¬± 34 min, respectively. The effect of EID (mean BW loss of 2.20 ¬± 1.0%) during self-paced exercise conditions was to produce a non-significant increase in endurance performance of 0.06 ± 2.72% (p=0.94), compared with the maintenance of euhydration (mean BW loss of 0.44 ± 0.48%). Meta-regression analyses revealed a statistically significant relationship between the percentage changes in power output and exercise intensity and duration, but not with the EID-associated percentage changes in BW loss. Drinking according to the dictate of thirst was associated with an increase in TT performance compared with a rate of drinking below (+5.2 ¬± 4.6%, p=0.01) or above (+2.4 ¬± 5.0%, p=0.40) thirst. The probability that drinking to thirst confers a real and meaningful advantage on TT performances conducted under field conditions compared with a rate of drinking below and above thirst sensation is of the order of 98% and 62%, respectively. CONCLUSIONS: (1) Compared with euhydration, EID (up to 4% BW loss) does not alter cycling performances during out-of-door exercise conditions; (2) exercise intensity and duration have a much greater impact on cycling TT performances than EID and; (3) relying on thirst sensation to gauge the need for fluid replacement maximises cycling TT performances.

Thirst in the elderly with and without heart failure

Elderly patients with heart failure (HF) may be troubled by thirst, despite the fact that elderly have an impaired ability to sense thirst. The present study was undertaken to compare the intensity of thirst in patients with and without HF and to evaluate how this symptom relates to the health-related quality of life and indices of the fluid balance. Forty-eight patients (mean age 80 years) admitted to hospital with worsening HF (n = 23) or with other acute illness (n = 25) graded their thirst and estimated their health-related quality of life (HRQoL). Serum sodium was measured and urine samples were assessed for color and electrolyte content. The HF patients reported significantly more intensive thirst (median = 75 mm) compared with those in the control group (median = 25 mm; p < 0.0001). There was no statistically significant relationship between thirst and HRQoL, which was low overall. Serum sodium and urine color did not differ significantly between the groups, but the urine of the HF patients had a lower sodium concentration and osmolality. We conclude that elderly patients with worsening HF have considerably increased thirst and, hence, intense thirst should be regarded as a symptom of HF.

Changes in total body water content during running races of 21.1 km and 56 km in athletes drinking ad libitum.

OBJECTIVE: To measure changes in body mass (BM), total body water (TBW), fluid intake, and blood biochemistry in athletes during 21.1-km and 56-km foot races. DESIGN: Observational study. SETTING: 2009 Two Oceans Marathon, South Africa. PARTICIPANTS: Twenty-one (21.1 km) and 12 (56 km) participants were advised to drink according to thirst or their own race drink plan (ad libitum). MAIN OUTCOME MEASURES: Body mass, TBW, plasma osmolality, plasma sodium (p[Na]), and plasma total protein ([TP]) concentrations were measured before and after race. Fluid intake was recorded from recall after race. RESULTS: Significant BM loss occurred in both races (21.1 km; -1.4 ± 0.6 kg; P < 0.000 and 56 km; -2.5 ± 1.1 kg; P < 0.000). Total body water was reduced in the 56-km race (-1.4 ± 1.1 kg; P < 0.001). A negative linear relationship was found between percentage change (%Δ) in TBW and %Δ in BM in the 56-km runners (r = 0.6; P < 0.01). Plasma osmolality and [TP] increased significantly in the 56-km runners (6.8 ± 8.2 mOsm/kg H2O; P < 0.05 and 5.4 ± 4.4 g/L; P < 0.01, respectively), but all other biochemical measures were within the normal range. CONCLUSIONS: Although TBW decreased in the 56-km race and was maintained in the 21.1-km race, the change in TBW over both races was less than the BM, suggesting that not all BM lost during endurance exercise is a result purely of an equivalent reduction in TBW. These findings support the interpretation that the body primarily defends p[Na] and not BM during exercise and that a reduction in BM can occur without an equivalent reduction in TBW during prolonged exercise. Furthermore, these data support that drinking without controlling for BM loss may allow athletes to complete these events.

Fluid replacement requirements for child athletes.

Thermoregulatory responses to exercise differ in prepubertal athletes compared with their adult counterparts. It is important, therefore, to consider fluid requirements specific to this age group to prevent risks of dehydration and diminished sports performance. Relative to their body size, children demonstrate lower sweat water losses during exercise than adults. Nonetheless, percentage levels of incurred dehydration are similar in pre- and postpubertal athletes. Moreover, voluntary (ad libitum) drinking volumes in children in respect to their body size are comparable or greater than those of adults. Given an adequate opportunity to drink during exercise, volume intake driven by thirst should be expected to prevent significant levels of dehydration in child athletes. The amount can be calculated conservatively as an hourly fluid intake of 13 mL/kg (6 mL/lb) bodyweight. Equally important is post-exercise fluid replenishment (approximately 4 mL/kg [2 mL/lb] for each hour of exercise) to avoid initiating subsequent exercise bouts in a dehydrated state. Choice of fluid should be dictated by taste preference, since volume of intake, rather than fluid content, is the most critical issue in child athletes. Since children may lack motivation for proper fluid intake behaviours, the responsibility falls to coaches and parents to assure that young athletes receive appropriate hydration during and after exercise bouts.

Changes in sensory perception of sports drinks when consumed pre, during and post exercise.

The aim of this study was to examine sensory perceptions towards different formulations of sports drinks when consumed before, at various points during, and following exercise. Following familiarization 14 recreational runners underwent four trials in a single blind counterbalanced design. Each trial utilised one of four different solutions: 7.5% carbohydrate, 421 mg L(-1) electrolyte (HiC-HiE); 7.5% carbohydrate, 140 mg L(-1) electrolyte (HiC-LoE); 1.3% carbohydrate, 421 mg L(-1) electrolyte (LoC-HiE) and water. Subjects were provided with 50-ml samples to ingest and then rate (using a 100-mm line scale) the intensity of sweetness, saltiness, thirst-quenching ability and overall liking before (-30 min), during (0, 30 and 60 min) and following (90 and 120 min) treadmill running exercise. Ratings of sweetness for all energy-containing drinks were higher during exercise relative to pre- and post-exercise conditions (P<0.05); ratings also increased with duration of exercise (P<0.001). Sweetness ratings for LoC-HiE increased during exercise (P<0.05) but remained the same for other beverages. Ratings of saltiness decreased for all energy-containing drinks during exercise relative to pre-exercise (P<0.05); ratings decreased with duration of exercise in these drinks (P<0.05). Ratings of thirst-quenching ability (P=0.039) and overall liking (P=0.013) increased with duration of exercise with all beverages. Significant changes in sensory perception occur when consuming sports drinks during exercise relative to non-exercise conditions. Temporal changes also occur during exercise itself which leads to enhanced liking of all beverages.

Hydration in cancer patients.

PURPOSE OF REVIEW: To provide an overview of issues central to hydration in an oncology population while highlighting recent advances and publications in the clinical and scientific literature. RECENT FINDINGS: Dehydration accounts for a significant number of unplanned visits to cancer clinics and emergency rooms. The decision to provide or withhold fluid in patients with terminal cancer is strongly influenced by subjective beliefs and the decision to use of hydration at the end of life should be individualized. Chronic dehydration may play a role in the pathogenesis of cancer. SUMMARY: Cancer patients are at high risk for dehydration from both the disease and the treatment. Treating physicians should have a low threshold for providing additional fluids to prevent dehydration. For patients at the end of life, hydration may be indicated in select patients.

Intravenous versus oral rehydration in athletes.

Fluid is typically administered via intravenous (IV) infusion to athletes who develop clinical symptoms of heat illness, based on the perception that dehydration is a primary factor contributing to the condition. However, other athletes also voluntarily rehydrate with IV fluid as opposed to, or in conjunction with, oral rehydration. The voluntary use of IV fluids to accelerate rehydration in dehydrated, though otherwise healthy athletes, has recently been banned by the World Anti-Doping Agency. However, the technique remains appealing to many athletes. Given that it now violates the Anti-Doping Code, it is important to determine whether potential benefits of using this technique outweigh the risks involved. Several studies have shown that rehydration is more rapid with IV fluid. However, the benefits are generally transient and only small differences to markers of hydration status are seen when comparing IV and oral rehydration. Furthermore, several studies have shown improvements in cardiovascular function and thermoregulation with IV fluid, while others have indicated that oral fluid is superior. Subsequent exercise performance has not been improved to a greater extent with one technique over the other. The paucity of definitive findings is probably related to the small number of studies investigating these variables and the vast differences in the designs of studies that have been conducted. The major limitation of IV rehydration is that it bypasses oropharyngeal stimulation, which has an influence on factors such as thirst sensation, antidiuretic hormone (arginine vasopressin) release, cutaneous vasodilation and mean arterial pressure. Further research is necessary to determine the relative benefits of oral and IV rehydration for athletes.

Thirst and hydration: physiology and consequences of dysfunction.

The constant supply of oxygen and nutriments to cells (especially neurons) is the role of the cardiovascular system. The constant supply of water (and sodium) for cardiovascular function is the role of thirst and sodium appetite and kidney function. This physiological regulation ensures that plasma volume and osmolality are maintained within set limits by initiating behaviour and release of hormones necessary to ingest and conserve water and sodium within the body. This regulation is separated into 2 parts; intracellular and extracellular (blood). An increased osmolality draws water from cells into the blood thus dehydrating specific brain osmoreceptors that stimulate drinking and release of anti diuretic hormone (ADH or vasopressin). ADH reduces water loss via lowered urine volume. Extracellular dehydration (hypovolaemia) stimulates specific vascular receptors that signal brain centres to initiate drinking and ADH release. Baro/volume receptors in the kidney participate in stimulating the release of the enzyme renin that starts a cascade of events to produce angiotensin II (AngII), which initiates also drinking and ADH release. This stimulates also aldosterone release which reduces kidney loss of urine sodium. Both AngII and ADH are vasoactive hormones that could work to reduce blood vessel diameter around the remaining blood. All these events work in concert so that the cardiovascular system can maintain a constant perfusion pressure, especially to the brain. Even if drinking does not take place ADH, AngII and aldosterone are still released. Furthermore, it has been observed that treatment of hypertension, obesity, diabetes and cancer can involve renin-AngII antagonists which could suggest that, in humans at least, there may be dysfunction of the thirst regulatory mechanism.

Thermoregulatory responses and hydration practices in heat-acclimatized adolescents during preseason high school football.

ONTEXT: Previous researchers have not investigated the thermoregulatory responses to multiple consecutive days of American football in adolescents. OBJECTIVE: To examine the thermoregulatory and hydration responses of high school players during formal preseason football practices. DESIGN: Observational study. SETTING: Players practiced outdoors in late August once per day on days 1 through 5, twice per day on days 6 and 7, and once per day on days 8 through 10. Maximum wet bulb globe temperature averaged 23 +/- 4 degrees C. PATIENTS OR OTHER PARTICIPANTS: Twenty-five heat-acclimatized adolescent boys (age = 15 +/- 1 years, height = 180 +/- 8 cm, mass = 81.4 +/- 15.8 kg, body fat = 12 +/- 5%, Tanner stage = 4 +/- 1). MAIN OUTCOME MEASURE(S): We observed participants within and across preseason practices of football. Measures included gastrointestinal temperature (T(GI)), urine osmolality, sweat rate, forearm sweat composition, fluid consumption, testosterone to cortisol ratio, perceptual measures of thirst, perceptual measures of thermal sensation, a modified Environmental Symptoms Questionnaire, and knowledge questionnaires assessing the participants' understanding of heat illnesses and hydration. Results were analyzed for differences across time and were compared between younger (14-15 years, n = 13) and older (16-17 years, n = 12) participants. RESULTS: Maximum daily T(GI) values remained less than 40 degrees C and were correlated with maximum wet bulb globe temperature (r = 0.59, P = .009). Average urine osmolality indicated that participants generally experienced minimal to moderate hypohydration before (881 +/- 285 mOsmol/kg) and after (856 +/- 259 mOsmol/kg) each practice as a result of replacing approximately two-thirds of their sweat losses during exercise but inadequately rehydrating between practices. Age did not affect most variables; however, sweat rate was lower in younger participants (0.6 +/- 0.2 L/h) than in older participants (0.8 +/- 0.1 L/h) (F(1,18) = 8.774, P = .008). CONCLUSIONS: Previously heat-acclimatized adolescent boys (T(GI) < 40 degrees C) can safely complete the initial days of preseason football practice in moderate environmental conditions using well-designed practice guidelines. Adolescent boys replaced most sweat lost during practice but remained mildly hypohydrated throughout data collection, indicating inadequate hydration habits when they were not at practice.

The effects of fluid ingestion on free-paced intermittent-sprint performance and pacing strategies in the heat.

The purpose of this study was to examine the effects of fluid ingestion on pacing strategies and performance during intermittent-sprint exercise in the heat. Nine male rugby players performed a habituation session and 2 x 50-min intermittent-sprint protocols at a temperature of 31 degrees C, either with or without fluid. Participants were informed of a third session (not performed) to ensure that they remained blind to all respective conditions. The protocol consisted of a 15-m sprint every minute separated by self-paced bouts of hard running, jogging, and walking for the remainder of the minute. Sprint time, distance covered during self-paced exercise, and vertical jump height before and after exercise were recorded. Heart rate, core temperature, nude mass, capillary blood haematocrit, pH, lactate concentration, perceptual ratings of perceived exertion, thermal stress, and thirst were also recorded. Sprint times (fluid vs. no-fluid: 2.82 +/- 0.11 vs. 2.82 +/- 0.14) and distance covered during self-paced exercise (fluid vs. no-fluid: 4168 +/- 419 vs. 3981 +/- 263 m) were not different between conditions (P = 0.10-0.98) but were progressively reduced to a greater extent in the no-fluid trial (7 +/- 13%) (d = 0.56-0.58). There were no differences (P = 0.22-1.00; d = <0.20-0.84) between conditions in any physiological measures. Perceptual ratings of perceived exertion and thermal stress did not differ between conditions (P = 0.34-0.91; d < or =0.20-0.48). Rating of thirst after exercise was lower in the fluid trial (P = 0.02; d = 0.62-0.73). The present results suggest that fluid availability did not improve intermittent-sprint performance, however did affect pacing strategies with a greater reduction in distance covered of self-paced exercise during the no-fluid trial.

Is drinking to thirst optimum?

BACKGROUNDS/AIMS: Prior to 1969, athletes were advised to avoid drinking during exercise. At least 4 subsequent events led to the adoption of a radically different approach. By 1996, all exercisers were advised to drink 'as much as tolerable' in order to insure that they did not lose any weight during exercise -the 'zero percent dehydration' doctrine. This advice requires that athletes drink enough to 'stay ahead of thirst'. The act of drinking is a basic survival instinct that has been regulated by complex, unconscious controls ever since the first fish-like creatures moved onto land and should not require conscious adjustment. METHODS: Literature survey of all studies comparing the effects of drinking to thirst (ad libitum) and drinking to prevent any weight loss during exercise - the'zero percent dehydration' doctrine. RESULT: No study found that drinking more than ad libitum during exercise produced any biological advantage, but it could cause exercise-associated hyponatremia. CONCLUSION: Drinking ad libitum appears to optimize performance and safety during exercise in many situations. The presence of thirst, not of water loss, may be the biological signal that impairs exercise performance in those who drink less than their thirst dictates during exercise.

Pediatric disorders of water balance

Fluid homeostasis requires adequate water intake, regulated by an intact thirst mechanism and appropriate free water excretion by the kidneys, mediated by appropriate secretion of arginine vasopressin (AVP, also known as antidiuretic hormone). AVP exerts its antidiuretic action by binding to the X chromosome-encoded V2 vasopressin receptor (V2R), a G protein-coupled receptor on the basolateral membrane of renal collecting duct epithelial cells. After V2R activation, increased intracellular cyclic adenosine monophosphate mediates shuttling of the water channel aquaporin 2 to the apical membrane of collecting duct cells, resulting in increased water permeability and antidiuresis. Clinical disorders of water balance are common, and abnormalities in many steps involving AVP secretion and responsiveness have been described. This article focuses on the principal disorders of water balance, diabetes insipidus, and the syndrome of inappropriate antidiuretic hormone secretion.

 

Hyponatremia and antidiuresis syndrome.

Antidiuretic hormone (ADH), or arginine vasopressin (AVP), is primarily regulated through plasma osmolarity, as well as non-osmotic stimuli including blood volume and stress. Links between water-electrolyte and carbohydrate metabolism have also been recently demonstrated. AVP acts via the intermediary of three types of receptors: V1a, or V1, which exerts vasoconstrictive effects; pituitary gland V1b, or V3, which participates in the secretion of ACTH; and renal V2, which reduces the excretion of pure water by combining with water channels (aquaporin 2). Antidiuresis syndrome is a form of euvolaemic, hypoosmolar hyponatraemia, which is characterised by a negative free water clearance with inappropriate urine osmolality and intracellular hyper-hydration in the absence of renal, adrenal and thyroid insufficiency. Ninety percent of cases of antidiuresis syndrome occur in association with hypersecretion of vasopressin, while vasopressin is undetectable in 10% of cases. Thus the term "antidiuresis syndrome" is more appropriate than the classic name "syndrome of inappropriate ADH secretion" (SIADH). The clinical symptoms, morbidity and mortality of hyponatraemia are related to its severity, as well as to the rapidity of its onset and duration. Even in cases of moderate hyponatraemia that are considered asymptomatic, there is a very high risk of falls due to gait and attention disorders, as well as rhabdomyolysis, which increases the fracture risk. The aetiological diagnosis of hyponatraemia is based on the analysis of calculated or measured plasma osmolality (POsm), as well as blood volume (skin tenting of dehydration, oedema). Hyperglycaemia and hypertriglyceridaemia lead to hyper- and normoosmolar hyponatraemia, respectively. Salt loss of gastrointestinal, renal, cutaneous and sometimes cerebral origin is hypovolaemic, hypoosmolar hyponatraemia (skin tenting), whereas oedema is present with hypervolaemic, hypoosmolar hyponatraemia of heart failure, nephrotic syndrome and cirrhosis. Some endocrinopathies (glucocorticoid deficiency and hypothyroidism) are associated with euvolaemic, hypoosmolar hyponatraemia, which must be distinguished from SIADH. Independent of adrenal insufficiency, isolated hypoaldosteronism can also be accompanied by hypersecretion of vasopressin secondary to hypovolaemia, which responds to mineralocorticoid administration. The causes of SIADH are classic: neoplastic (notably small-cell lung cancer), iatrogenic (particularly psychoactive drugs, chemotherapy), lung and cerebral. Some causes have been recently described: familial hyponatraemia via X-linked recessive disease caused by an activating mutation of the vasopressin 2 receptor; and corticotropin insufficiency related to drug interference between some inhaled glucocorticoids and cytochrome p450 inhibitors, such as the antiretroviral drugs and itraconazole, etc. SIADH in marathon runners exposes them to a risk of hypotonic encephalopathy with fatal cerebral oedema. SIADH treatment is based on water restriction and demeclocycline. V2 receptor antagonists are still not marketed in France. These aquaretics seem effective clinically and biologically, without demonstrated improvement to date of mortality in eu- and hypervolaemic hyponatraemia. Obviously treatment of a corticotropic deficit, even subtle, should not be overlooked, as well as the introduction of fludrocortisone in isolated hypoaldosteronism and discontinuation of iatrogenic drugs.

Nutritional, Physiological and Perceptual Responses During a Summer Ultra-Endurance Cycling Event.

Despite the rapid growth of mass-participation road cycling, little is known about the dietary, metabolic and behavioral responses of ultra-endurance cyclists. This investigation describes physiological responses, perceptual ratings, energy balance, and macronutrient intake of 42 men (mean ± SD; age, 38±6 y; height, 179.7±7.1 cm; body mass, 85.85±14.79 kg) and 6 women (age, 41±4 y; height, 168.0±2.9 cm; body mass, 67.32±7.21 kg) during a summer 164-km road cycling event. Measurements were recorded one day before, and on Event Day (10.5 h) at the start (0 km), at two aid stations (52 km and 97 km), and at the finish line (164 km). Ambient temperature was >39.0°C during the final 2 h of exercise. Mean finish times for men (9.1±1.2 h) and women (9.0±0.2 h) were similar, as were mean gastrointestinal temperature [TGI], four hydration biomarkers, and five perceptual (e.g., thermal, thirst, pain) ratings. Male cyclists consumed enough fluids on Event Day (5.91±2.38 L; 49% water) to maintain body mass within 0.76 kg, start to finish, despite a sweat loss of 1.13±0.54 L·h and calculated energy expenditure of 3,115 Kcal·10.5h. However, men voluntarily under-consumed food energy (deficit of 2,594 Kcal, 10.9 MJ), and specific macronutrients (carbohydrates, 106±48 g; protein, 8 ± 7 g; and sodium, 852 ± 531 mg) between 0530 and 1400 h. Also, a few men exhibited extreme final values (i.e., urine specific gravity of 1.035 to 1.038, n=5; body mass loss >4 kg, n=2; TGI, 39.4 and 40.2). We concluded that these findings provide information regarding energy consumption, macronutrient intake, hydration status and the physiological stresses that are unique to ultra-endurance exercise in a hot environment.

Changes in core temperature and hydration status during a competitive football match played in cool conditions.

Football is played throughout the world in a wide range of environmental conditions. Thermal responses to match play in temperate and warm conditions have been widely reported, but there little published work that has quantified changes in core temperature and hydration status when football is played in cool conditions. Fifteen male university football players (age 20 ± 1 y, height 1.81 ± 0.06 m, body mass 79.7 ± 9.5 kg) took part in a competitive match in cool conditions (6.5 ± 0.8°C, 66 ± 4% relative humidity). Core temperature (Tc) was measured using an ingestible telemetric sensor (HQ Inc. Florida, USA). Sweat losses were assessed from the change in body mass after correction for the volume of fluid consumed. Tc prior to the start of the match was 37.3±0.3°C. T of the starting players increased as the match progressed (P < 0.05), with values of 39.0±0.4°C and 39.1±0.4°C recorded at half time and full time respectively. The highest individual Tc was 39.6°C. The Tc of the reserve players (n=5) increased above resting values after the warm up (P < 0.05), but decreased as the match progressed. While this was not statistically different from prematch values, two reserves did fall below 37.0°C. Body mass losses of starting players were 1.04±0.35 kg (range 0.57-1.48 kg). Fluid intake during the match was 0.72±0.34 l. When corrected for the ingestion of fluid, and any urine output, the estimated sweat losses were 1.53±0.41 l (range 0.75-2.00 l), which corresponds to a sweat rate of 1.0±0.3 l/h (range 0.5-1.3 l/h). The present study suggests that players involved in competitive football matches played in cool conditions exhibit similar thermoregulatory and hydration responses to those reported during match play in more temperate conditions. As competitive football is played in colder conditions than those experienced in this study, further research into the physiological response of players to these conditions is warranted.

Voluntary fluid intake in the cold.

When exercising in a cold environment, fluid losses can occur via sweat, cold induced diuresis and respiration but failure to replace lost fluid is common in the cold due to a blunted thirst response (Kenefick et al. Med Sci Sports Exerc 2004;36;1528-34). This study assessed voluntary fluid intake and measures of hydration status following moderate intensity exercise in the cold. Ten healthy males (age 22±2 years, mass 67.8±7.0 kg, height 1.77±0.06 m, VO(2peak) 60.5±8.9 ml.kg.min(-1)) completed two trials following familiarisation separated by 7-14 days. In each trial, subjects sat for 30 min before cycling at 70% VO(2peak) for 60 min in either 25.0±0.1°C, 50.8±1.5% RH (warm) or 0.4±1.0°C, 68.8±7.5% RH (cold). Subjects then sat for 120 min at 22.2±1.2°C, 50.5±8.0% RH. Ad libitum drinking was allowed during the exercise and recovery periods. Urine volume, body mass, serum osmolality and Na and K concentrations and sensations of thirst were measured at baseline, postexercise and after 60 and 120 min of the recovery period. Sweat loss was lower in the cold trial (0.48±0.15 l vs 0.96±0.18 l) (p0.05). Postexercise serum osmolality was higher compared to baseline in the cold (292±2 vs 287±3 mOsm.kg(-1), p<0.0001) and warm trials (288±5 vs 285±4 mOsm.kg(-1); p=0.048). Voluntary fluid intake was less in the cold environment, however in both the warm and cold environment, ad libitum fluid intake, combined with fluid losses, resulted in similar changes in body mass.

Update: Cold weather injuries, U.S. Armed Forces, July 2006-June 2011.

From July 2010 through June 2011, the number of U.S. service members treated for cold injuries (n=557) was similar to recent prior years. The most frequently reported cold injury was hypothermia in the Marine Corps and frostbite in the other service branches. Cold injury rates were generally highest among service members who were less than 20 years old and of black, non-Hispanic race/ethnicity. Service members who train in wet and freezing conditions -- and their supervisors at all levels -- should know the signs of cold injury, ensure adequate hydration, and avoid tobacco, caffeine, and vasoconstrictive medications.

Improving the hydration of hospital patients.

Dehydration occurs when the body loses fluids at a greater rate than it takes in. For some patients, achieving a fluid balance is difficult without assistance and they rely on interventions by health professionals. In 2009, a fluid balance audit was carried out in an acute hospital. The aim was to identify whether clinical practice could be improved, and if health professionals could assist their patients' hydration during their admission by using a hands-free drinks system.

Examining the influence of hydration status on physiological responses and running speed during trail running in the heat with controlled exercise intensity.

The purpose of this study was to determine the effects of dehydration at a controlled relative intensity on physiological responses and trail running speed. Using a randomized, controlled crossover design in a field setting, 14 male and female competitive, endurance runners aged 30 ± 10.4 years completed 2 (hydrated [HY] and dehydrated [DHY]) submaximal trail runs in a warm environment. For each trial, the subjects ran 3 laps (4 km per lap) on trails with 4-minute rests between laps. The DHY were fluid restricted 22 hours before the trial and during the run. The HY arrived euhydrated and were given water during rest breaks. The subjects ran at a moderate pace matched between trials by providing pacing feedback via heart rate (HR) throughout the second trial. Gastrointestinal temperature (T(GI)), HR, running time, and ratings of perceived exertion (RPE) were monitored. Percent body mass (BM) losses were significantly greater for DHY pretrial (-1.65 ± 1.34%) than for HY (-0.03 ± 1.28%; p < 0.001). Posttrial, DHY BM losses (-3.64 ± 1.33%) were higher than those for HY (-1.38 ± 1.43%; p < 0.001). A significant main effect of T(GI) (p = 0.009) was found with DHY having higher T(GI) postrun (DHY: 39.09 ± 0.45°C, HY: 38.71 ± 0.45°C; p = 0.030), 10 minutes post (DHY: 38.85 ± 0.48°C, HY: 38.46 ± 0.46°C; p = 0.009) and 30 minutes post (DHY: 38.18 ± 0.41°C, HY: 37.60 ± 0.25°C; p = 0.000). The DHY had slower run times after lap 2 (p = 0.019) and lap 3 (p = 0.025). The DHY subjects completed the 12-km run 99 seconds slower than the HY (p = 0.027) subjects did. The RPE in DHY was slightly higher than that in HY immediately postrun (p = 0.055). Controlling relative intensity in hypohydrated runners resulted in slower run times, greater perceived effort, and elevated T(GI), which is clinically meaningful for athletes using HR as a gauge for exercise effort and performance.

 

Examining the influence of hydration status on physiological responses and running speed during trail running in the heat with controlled exercise intensity

The purpose of this study was to determine the effects of dehydration at a controlled relative intensity on physiological responses and trail running speed. Using a randomized, controlled crossover design in a field setting, 14 male and female competitive, endurance runners aged 30 ± 10.4 years completed 2 (hydrated [HY] and dehydrated [DHY]) submaximal trail runs in a warm environment. For each trial, the subjects ran 3 laps (4 km per lap) on trails with 4-minute rests between laps. The DHY were fluid restricted 22 hours before the trial and during the run. The HY arrived euhydrated and were given water during rest breaks. The subjects ran at a moderate pace matched between trials by providing pacing feedback via heart rate (HR) throughout the second trial. Gastrointestinal temperature (TGI), HR, running time, and ratings of perceived exertion (RPE) were monitored. Percent body mass (BM) losses were significantly greater for DHY pretrial (-1.65 ± 1.34%) than for HY (-0.03 ± 1.28%; p < 0.001). Posttrial, DHY BM losses (-3.64 ± 1.33%) were higher than those for HY (-1.38 ± 1.43%; p < 0.001). A significant main effect of TGI (p = 0.009) was found with DHY having higher TGI postrun (DHY: 39.09 ± 0.45°C, HY: 38.71 ± 0.45°C; p = 0.030), 10 minutes post (DHY: 38.85 ± 0.48°C, HY: 38.46 ± 0.46°C; p = 0.009) and 30 minutes post (DHY: 38.18 ± 0.41°C, HY: 37.60 ± 0.25°C; p = 0.000). The DHY had slower run times after lap 2 (p = 0.019) and lap 3 (p = 0.025). The DHY subjects completed the 12-km run 99 seconds slower than the HY (p = 0.027) subjects did. The RPE in DHY was slightly higher than that in HY immediately postrun (p = 0.055). Controlling relative intensity in hypohydrated runners resulted in slower run times, greater perceived effort, and elevated TGI, which is clinically meaningful for athletes using HR as a gauge for exercise effort and performance.

Voluntary drinking behaviour, fluid balance and psychological affect when ingesting water or a carbohydrate-electrolyte solution during exercise

This study investigated the effects of drink composition on voluntary intake, hydration status, selected physiological responses and affective states during simulated gymnasium-based exercise. In a randomised counterbalanced design, 12 physically active adults performed three 20-min intervals of cardiovascular exercise at 75% heart rate maximum, one 20-min period of resistance exercise and 20min of recovery with ad libitum access to water (W), a carbohydrate-electrolyte solution (CES) or with no access to fluids (NF). Fluid intake was greater with CES than W (1706±157 vs. 1171±152mL; P<0.01) and more adequate hydration was achieved in CES trials (NF vs. W vs. CES: -1668±73 vs. -700±99 vs. -273±78g; P<0.01). Plasma glucose concentrations were highest with CES (CES vs. NF vs. W: 4.26±0.12 vs. 4.06±0.08 vs. 3.97±0.10mmol/L; P<0.05). Pleasure ratings were better maintained with ad libitum intake of CES (CES vs. NF vs. W: 2.72±0.23 vs. 1.09±0.20 vs. 1.74±0.33; P<0.01). Under conditions of voluntary drinking, CES resulted in more adequate hydration and a better maintenance of affective states than W or NF during gymnasium-based exercise.

Beverage consumption and BMI of British schoolchildren aged 9-13 years

OBJECTIVE: Adequate fluid intake has been well documented as important for health but whether it has adverse effects on overall energy and sugar intakes remains under debate. Many dietary studies continue to refrain from reporting on beverage consumption, which the present study aimed to address. DESIGN: A cross-sectional survey investigated self-reported measures of dietary intake and anthropometric measurements. SETTING: Primary and secondary schools in south-west London, UK. SUBJECTS: Boys and girls (n 248) aged 9-13 years. RESULTS: Boys consumed 10 % and girls consumed 9 % of their daily energy intake from beverages and most children had total sugar intakes greater than recommended. Beverages contributed between a quarter and a third of all sugars consumed, with boys aged 11-13 years consuming 32 % of their total sugar from beverages. There was a strong relationship between consumption of beverages and energy intake; however, there was no relationship between beverage type and either BMI or BMI Z-score. Fruit juices and smoothies were consumed most frequently by all girls and 9-10-year-old boys; boys aged 11-13 years preferred soft drinks and consumed more of their daily energy from soft drinks. Milk and plain water as beverages were less popular. CONCLUSIONS: Although current health promotion campaigns in schools merit the attention being given to improving hydration and reducing soft drinks consumption, it may be also important to educate children on the energy and sugar contents of all beverages. These include soft drinks, as well as fruit juices and smoothies, which are both popular and consumed regularly.

Exercise-induced dehydration with and without environmental heat stress results in increased oxidative stress

While in vitro work has revealed that dehydration and hyperthermia can elicit increased cellular and oxidative stress, in vivo research linking dehydration, hyperthermia, and oxidative stress is limited. The purpose of this study was to investigate the effects of exercise-induced dehydration with and without hyperthermia on oxidative stress. Seven healthy male, trained cyclists (power output (W) at lactate threshold (LT): 199 ± 19 W) completed 90 min of cycling exercise at 95% LT followed by a 5-km time trial (TT) in 4 trials: (i) euhydration in a warm environment (EU-W, control), (ii) dehydration in a warm environment (DE-W), (iii) euhydration in a thermoneutral environment (EU-T), and (iv) dehydration in a thermoneutral environment (DE-T) (W: 33.9 ± 0.9 °C; T: 23.0 ± 1.0 °C). Oxidized glutathione (GSSG) increased significantly postexercise in dehydration trials only (DE-W: p < 0.01, DE-T: p = 0.03), and while not significant, total glutathione (TGSH) and thiobarbituric acid reactive substances (TBARS) tended to increase postexercise in dehydration trials (p = 0.08 for both). Monocyte heat shock protein 72 (HSP72) concentration was increased (p = 0.01) while lymphocyte HSP32 concentration was decreased for all trials (p = 0.02). Exercise-induced dehydration led to an increase in GSSG concentration while maintenance of euhydration attenuated these increases regardless of environmental condition. Additionally, we found evidence of increased cellular stress (measured via HSP) during all trials independent of hydration status and environment. Finally, both 90-min and 5-km TT performances were reduced during only the DE-W trial, likely a result of combined cellular stress, hyperthermia, and dehydration. These findings highlight the importance of fluid consumption during exercise to attenuate thermal and oxidative stress during prolonged exercise in the heat.

Effects of hydration in contrast-induced acute kidney injury after primary angioplasty: a randomized, controlled trial

Background- Intravascular volume expansion represents a beneficial measure against contrast-induced acute kidney injury (CI-AKI) in patients undergoing elective angiographic procedures. However, the efficacy of this preventive strategy has not yet been established for patients with ST-elevation-myocardial infarction (STEMI), who are at higher risk of this complication after primary percutaneous coronary intervention (PCI). In this randomized study we investigated the possible beneficial role of periprocedural intravenous volume expansion and we compared the efficacy of 2 different hydration strategies in patients with STEMI undergoing primary PCI. Methods and Results- We randomly assigned 450 STEMI patients to receive (1) preprocedure and postprocedure hydration of sodium bicarbonate (early hydration group), (2) postprocedure hydration of isotonic saline (late hydration group), or (3) no hydration (control group). The primary end point was the development of CI-AKI, defined as an increase in serum creatinine of ≥25% or 0.5 mg/dL over the baseline value within 3 days after administration of the contrast medium. Moreover, we evaluated a possible relationship between the occurrence of CI-AKI and total hydration volume administered. There were no significant differences in baseline clinical, biochemical, and procedural characteristics in the 3 groups. Overall, CI-AKI occurred in 93 patients (20.6%): the incidence was significantly lower in the early hydration group (12%) with respect to both the late hydration group (22.7%) and the control group (27.3%) (P for trend=0.001). In hydrated patients (early and late hydration groups), lower infused volumes were associated with a significant increase in CI-AKI incidence, and the optimal cutoff point of hydration volume that best discriminates patients at higher risk was ≤960 mL. Conclusions- Adequate intravenous volume expansion may prevent CI-AKI in patients undergoing primary PCI. A regimen of preprocedure and postprocedure hydration therapy with sodium bicarbonate appears to be more efficacious than postprocedure hydration only with isotonic saline. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00770614.

The validity of multi-frequency bioelectrical impedance measures to detect changes in the hydration status of wrestlers during acute dehydration and rehydration

The objective of this study was to examine the validity of multi-frequency direct segmental bioelectrical impedance analysis (DSM-BIA) measures to detect changes in the hydration status of wrestlers after undergoing 3% acute dehydration and a 2-h rehydration period. 56 NCAA wrestlers: (mean ± SEM); age 19.5 ± 0.2 years, height 1.73 ± 0.01 m, body mass (BM) 82.5 ± 2.3 kg were tested in euhydrated, dehydrated (-3.5%), and a 2-h rehydration conditions using DSM-BIA to detect changes in hydration status. Hydration status was quantified by measuring changes in plasma osmolality (Posm), urine osmolality (Uosm), urine specific gravity (Usg), BM and weighted segmental impedance at frequencies of 5, 20, 50, 100, and 500 Khz. Weighted segmental impedance significantly increased after a 3.5% reduction in body weight for all five frequencies evaluated, but did not return to baseline at 2-h rehydration. Posm (303 ± 0.6 mOsm·L), Uosm (617 ± 47 mOsm·L) and Usg (1.017 ± 0.001) all significantly increased at post-dehydration and returned to baseline at 2-h rehydration. Estimations of extracellular water (ECW) were significantly different throughout the trial, but there were no significant changes in estimations of total body water (TBW) or intracellular water (ICW). Results of the present study demonstrate the potential use of DSM-BIA as a field measure to assess the hydration status of wrestlers for the purpose of minimal weight certification prior to the competitive season. When employing DSM-BIA to assess hydration status, results indicated that changes in weighted segmental impedance at the frequencies evaluated (5, 20, 50, 100, and 500 Khz) are sensitive to acute changes in dehydration, but lag behind changes in the standard physiological (plasma and urinary) markers of hydration status after a 2-h rehydration period.

Nutrition for sports performance: issues and opportunities

Diet can significantly influence athletic performance, but recent research developments have substantially changed our understanding of sport and exercise nutrition. Athletes adopt various nutritional strategies in training and competition in the pursuit of success. The aim of training is to promote changes in the structure and function of muscle and other tissues by selective modulation of protein synthesis and breakdown in response to the training stimulus. This process is affected by the availability of essential amino acids in the post-exercise period. Athletes have been encouraged to eat diets high in carbohydrate, but low-carbohydrate diets up-regulate the capacity of muscle for fat oxidation, potentially sparing the limited carbohydrate stores. Such diets, however, do not enhance endurance performance. It is not yet known whether the increased capacity for fat oxidation that results from training in a carbohydrate-deficient state can promote loss of body fat. Preventing excessive fluid deficits will maintain exercise capacity, and ensuring adequate hydration status can also reduce subjective perception of effort. This latter effect may be important in encouraging exercise participation and promoting adherence to exercise programmes. Dietary supplement use is popular in sport, and a few supplements may improve performance in specific exercise tasks. Athletes must be cautious, however, not to contravene the doping regulations. There is an increasing recognition of the role of the brain in determining exercise performance: various nutritional strategies have been proposed, but with limited success. Nutrition strategies developed for use by athletes can also be used to achieve functional benefits in other populations.

 

Hydration status assessment by multi-frequency bioimpedance in patients with advanced chronic kidney disease

Introduction: Body composition assessment has the potential to improve the care of patients with chronic kidney disease (CKD). Whole-body multiple-frequency bioimpedance spectroscopy (BIS) appears to be a useful and appropriate technique for assessing hydration status and body composition in CKD patients. Objective: The aims of this study were to determine the hydration status by BIS in patients with advanced CKD, and to analyse the association of body fluid status with common clinical and biochemical characteristics. The prognostic value of the phase angle at 50KHz (PA) was also evaluated. Patients and methods: The study group consisted of 175 patients (66±14 year, 77 females) with eGFR<40ml/min not yet on dialysis. Body composition was assessed by BIS (BCM, Fresenius). Hydration status was expressed as a percentage of the total body water (TBW). Patients were prospectively followed-up for a median of 481 days, and the main determinants of mortality were estimated by Cox regression analysis. Results: The majority of patients (85%) showed a hydration status within ±5% TBW. Patients with oedemas or uncontrolled arterial hypertension showed mean estimate fluid overload significantly higher than that of the other study patients. Fluid overload was negatively associated with serum albumin levels, body mass index and urinary sodium/potassium ratio; and positively with male gender and diabetes. During the follow-up period, 16 patients died (9%). The main determinants of mortality adjusted for other potential covariates were: Davies comorbidity index (HR=4.304; P=.001), and PA (per each º; HR=0.491; P=.026). Conclusions: BIS may help identify changes in hydration status in CKD patients not fully appreciated by clinical or biochemical assessment. PA was a significant predictor of mortality in these patients.

Measuring and managing fluid balance

Ensuring patients are adequately hydrated is an essential part of nursing care, yet a recent report from the Care Quality Commission found "appalling" levels of care in some NHS hospitals, with health professionals failing to manage dehydration. This article discusses the importance of hydration, and the health implications of dehydration and overhydration. It also provides an overview of fluid balance, including how and why it should be measured, and discusses the importance of accurate fluid balance measurements.

Are diagnostic criteria for acute malnutrition affected by hydration status in hospitalized children? A repeated measures study

INTRODUCTION: Dehydration and malnutrition commonly occur together among ill children in developing countries. Dehydration (change in total body water) is known to alter weight. Although muscle tissue has high water content, it is not known whether mid-upper arm circumference (MUAC) may be altered by changes in tissue hydration. We aimed to determine whether rehydration alters MUAC, MUAC Z score (MUACz), weight-for-length Z-score (WFLz) and classification of nutritional status among hospitalised Kenyan children admitted with signs of dehydration. STUDY PROCEDURE: We enrolled children aged from 3 months to 5 years admitted to a rural Kenyan district hospital with clinical signs compatible with dehydration, and without kwashiorkor. Anthropometric measurements were taken at admission and repeated after 48 hours of treatment, which included rehydration by WHO protocols. Changes in weight observed during this period were considered to be due to changes in hydration status. RESULTS: Among 325 children (median age 11 months) the median weight gain (rehydration) after 48 hours was 0.21 kg, (an increase of 2.9% of admission body weight). Each 1% change in weight was associated with a 0.40 mm (95% CI: 0.30 to 0.44 mm, p < 0.001) change in MUAC, 0.035z (95% CI: 0.027 to 0.043z, P < 0.001) change in MUACz score and 0.115z (95% CI: 0.114 to 0.116 z, p < 0.001) change in WFLz. Among children aged 6 months or more with signs of dehydration at admission who were classified as having severe acute malnutrition (SAM) at admission by WFLz <-3 or MUAC <115 mm, 21% and 19% of children respectively were above these cut offs after 48 hours. CONCLUSION: MUAC is less affected by dehydration than WFLz and is therefore more suitable for nutritional assessment of ill children. However, both WFLz and MUAC misclassify SAM among dehydrated children. Nutritional status should bere-evaluated following rehydration, and management adjusted accordingly. FULL TEXT AVAILABLE IN PUBMED

Managing patients with dengue fever during an epidemic: the importance of a hydration tent and of a multidisciplinary approach.

BACKGROUND: Dengue fever is one of the most common tropical diseases worldwide. Early detection of the disease, followed by intravenous fluid therapy in patients with dengue hemorrhagic fever (DHF) or with warning signs of denguehas a major impact on the prognosis. The purpose of this study is to describe the care provided in a hydration tent, including early detection, treatment, and serial follow-up of patients with dengue fever. FINDINGS: The analysis included all patients treated in the hydration tent from April 8 to May 9, 2008. The tent was set up inside the premises of the 2nd Military Firemen Group, located in Meier, a neighborhood in Rio de Janeiro, Brazil. The case form data were stored in a computerized database for subsequent assessment. Patients were referred to the tent from primary care units and from secondary city and state hospitals. The routine procedure consisted of an initial screening including vital signs (temperature, blood pressure, heart rate, and respiratory rate), tourniquet test and blood sampling for complete blood count. Over a 31-day period, 3,393 case recordings were seen at the hydration tent. The mean was 109 patients per day. A total of 2,102 initial visits and 1,291 return visits were conducted. Of the patients who returned to the hydration tent for reevaluation, 850 returned once, 230 returned twice, 114 returned three times, and 97 returned four times or more. Overall, 93 (5.3%) patients with DHF seen at the tent were transferred to a tertiary hospital. There were no deaths among these patients. DISCUSSION: As the epidemics were already widespread and there were no technical conditions for routine serology, all cases of suspected dengue fever were treated as such. Implementing hydration tents decrease the number of dengue fever hospitalizations.

Hydration Status in Adolescent Judo Athletes Before and After Training in the Heat.

Adolescent judo athletes that train in tropical climates may be in a persistent state of dehydration because they frequently restrict fluids during daily training sessions to maintain or reduce their body weight and are not given enough opportunities to drink. PURPOSE: Determine the body hydration status of adolescent judo athletes before (PRE), immediately after (POST), and 24 hours after (24H) a training session and document sweat Na+ loss and symptoms of dehydration. METHODS: Body mass and urine color and specific gravity (USG) were measured PRE, POST, and 24H after a training session in a high heat stress environment (29.5 ± 1.0°C; 77.7 ± 6.1% RH) in 24 adolescent athletes. Sweat sodium loss was also determined. A comparison was made between mid pubertal (MP) and late pubertal (LP) subjects. RESULTS:The majority of the subjects started training with a significant level of dehydration. During the training session, MP subjects lost 1.3 ± 0.8% of their pre-training body mass while LP subjects lost 1.9 ± 0.5% (P < 0.05). Sweat sodium concentration was 44.5 ± 23.3 mmol/L. Fluid intake from a water fountain was minimal. Subjects reported symptoms of dehydration during the session which in some cases persisted throughout the night and the next day. The 24H USG was 1.028 ± 0.004 and 1.027 ± 0.005 g/ml for MP and LP, respectively. CONCLUSIONS: Adolescent judo athletes arrive to practice with a fluid deficit, do not drink enough during training, and experience symptoms of dehydration which may compromise the quality of training and general well being.

Effects of graded exercise-induced dehydration and rehydration on circulatory markers of oxidative stress across the resting and exercising human leg

Exercise in the heat enhances oxidative stress markers in the human circulation, but the contribution of active skeletal muscle and the influence of hydration status remain unknown. To address this question, we measured leg exchange of glutathione (GSH), glutathione disulfide (GSSG), superoxide dismutase activity (SOD) and isoprostanes in seven males at rest and during submaximal one-legged knee extensor exercise in the following four conditions: (1) control euhydration (0% reduction in body mass), (2) mild-dehydration (2%), (3) moderate-dehydration (3.5%), (4) rehydration (0%). In all resting and control exercise conditions, a net GSH uptake was observed across the leg. In contrast, a significant leg release of GSH into the circulation (-354 ± 221 μmol/min, P < 0.05) was observed during exercise with moderate-dehydration, which was still present following full rehydration (-206 ± 122 μmol/min, P < 0.05). During exercise, mild and moderate-dehydration decreased both femoral venous erythrocyte SOD activity (195 ± 6 vs. 180 ± 5 U/L, P < 0.05) and plasma isoprostanes (30 ± 1.1 vs. 25.9 ± 1.3 pg/L, P < 0.05), but during rehydration these were not different from control. In conclusion, these findings suggest that active skeletal muscles release GSH into the circulation under moderate dehydration and subsequent rehydration, possibly to enhance the antioxidant defense.

24h-Sodium excretion and hydration status in children and adolescents - Results of the DONALD Study

BACKGROUND & AIMS: To describe actual data on intake, sources, age and time trends of urinary sodium excretion and to analyze the potential association between urinary sodium excretion and hydration status respective beverage consumption in a sample of healthy German children and adolescents. METHODS: Data of 1575 24 h-urine samples and weighed dietary records of 499 children (249 boys) aged 4-18 years of the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study collected in 2003-2009 were analyzed using linear mixed effects regression models. Free water reserve (FWR, measured urine volume (ml/24 h) minus the obligatory urine volume (ml/24 h)) was used as a marker for hydration status. RESULTS: Urinary sodium excretion was between 1.4 g/day and 3.2 g/day, showing a positive age trend but remained stable during the study period. In girls, there was a significant positive association between salt excretion and FWR (p = 0.04). Per g/MJ urinary sodium excretion, beverage intake increased by 0.05 g/MJ (boys) or 0.08 g/MJ (girls). CONCLUSION: Hydration status was not affected by salt intake in this sample of healthy children and adolescents in a western life style, due to a compensatory increase in beverage consumption.

Water balance throughout the adult life span in a German population

Mild dehydration, defined as a 1-2 % loss in body mass caused by fluid deficit, is associated with risks of functional impairments and chronic diseases. Whether water requirements change with increasing age remains unclear. Therefore, the aim of the present investigation is to quantify hydration status and its complex determining factors from young to old adulthood to analyse age-related alterations and to provide a reliable database for the derivation of dietary recommendations. Urine samples collected over a 24 h period and dietary records from 1528 German adults (18-88 years; sub-sample of the first National Food Consumption Survey) were used to calculate water intake (beverages, food and metabolic water) and water excretion parameters (non-renal water losses (NRWL), urine volume, obligatory urine volume) and to estimate hydration status (free-water-reserve) and 'adequate intake (AI)'. Median total water intake (2483 and 2054 ml/d, for men and women, respectively (P < 0·0001)), decreased with increasing age only in males (P = 0·001).

Impaired cognitive function and mental performance in mild dehydration.

Dehydration is a reliable predictor of impaired cognitive status. Objective data, using tests of cortical function, support the deterioration of mental performance in mildly dehydrated younger adults. Dehydration frequently results in delirium as a manifestation of cognitive dysfunction. Although, the occurrence of delirium suggests transient acute global cerebral dysfunction, cognitive impairment may not be completely reversible. Animal studies have identified neuronal mitochondrial damage and glutamate hypertransmission in dehydrated rats. Additional studies have identified an increase in cerebral nicotinamide adenine dinucleotide phosphate-diaphorase activity (nitric oxide synthase, NOS) with dehydration. Available evidence also implicates NOS as a neurotransmitter in long-term potentiation, rendering this a critical enzyme in facilitating learning and memory. With ageing, a reduction of NOS activity has been identified in the cortex and striatum of rats. The reduction of NOs synthase activity that occurs with ageing may blunt the rise that occurs with dehydration, and possibly interfere with memory processing and cognitive function. Dehydration has been shown to be a reliable predictor of increasing frailty, deteriorating mental performance and poor quality of life. Intervention models directed toward improving outcomes in dehydration must incorporate strategies to enhance prompt recognition of cognitive dysfunction.

Dehydration impairs vigilance-related attention in male basketball players.

PURPOSE: To determine the effects of dehydration (DEH) on attentional vigilance in male basketball players. METHODS: The Test of Variables of Attention (TOVA; Universal Attention Disorders) was administered to 11 male basketball players (17-28 yr) at baseline (test 1), after walking (50% V O2max) in the heat (40 degrees C and 20% relative humidity) (test 2), and then after a simulated basketball game (test 3). Tests 2 and 3 were performed while subjects were either DEH (1-4%) or euhydrated (EUH). The TOVA consisted of target-infrequent and target-frequent conditions, simulating static and dynamic (such as a basketball game) environments, respectively. TOVA measures included errors of omission (OE) and commission (CE), response time (RT), and sensitivity. RESULTS: During the target-infrequent half of test 3, EUH resulted in significantly better sensitivity (+0.4+/-1.2 vs -0.9+/-1.3), faster RT (-8+/-20 vs +16+/-28), and fewer OE (-0.4+/-0.7 vs +1.3+/-2.4) compared with DEH. During the target-frequent half, EUH resulted in significantly fewer OE (-4+/-15 vs +5+/-7) and CE (-1.9+/-3.2 vs 0.6+/-1.4) in test 2 and greater sensitivity (+0.7+/-2.6 vs -0.7+/-1.1) and faster RT (-21+/-28 vs +5+/-31) than DEH in test 3. CONCLUSION: Vigilance-related attention of male basketball players was impaired by DEH, especially during the target-frequent condition of the TOVA. These results suggest that fluid replacement is essential to prevent the decline in vigilance that occurs with DEH in highly dynamic environments. Therefore, basketball players should be advised to maintain EUH for optimal concentration and attentional skills during competition.

Effects of fluid ingestion on cognitive function after heat stress or exercise-induced dehydration.

This study investigated the effects of heat exposure, exercise-induced dehydration and fluid ingestion on cognitive performance. Seven healthy men, unacclimatized to heat, were kept euhydrated or were dehydrated by controlled passive exposure to heat (H, two sessions) or by treadmill exercise (E, two sessions) up to a weight loss of 2.8%. On completion of a 1-h recovery period, the subjects drank a solution containing 50 g l(-1) glucose and 1.34 g l(-1) NaCl in a volume of water corresponding to 100% of his body weight loss induced by dehydration. (H1 and E1) or levels of fluid deficit were maintained (H0, E0). In the E0, H0 and control conditions, the subject drank a solution containing the same quantity of glucose diluted in 100 ml of water. Psychological tests were administered 30 min after the dehydration phase and 2 h after fluid ingestion. Both dehydration conditions impaired cognitive abilities (i.e. perceptive discrimination, short-term memory), as well as subjective estimates of fatigue, without any relevant differences between the methods. By 3.5 h after fluid deficit, dehydration (H0 and E0) no longer had any adverse effect, although the subjects felt increasingly tired. Thus, there was no beneficial effect of fluid ingestion (H1 and E1) on the cognitive variables. However, long-term memory retrieval was impaired in both control and dehydration situations, whereas there was no decrement in performance in the fluid ingestion condition (H1, E1).

Dehydration and cognitive performance.

Human neuropsychology investigates brain-behavior relationships, using objective tools (neurological tests) to tie the biological and behavior aspects together. The use of neuropsychological assessment tools in assessing potential effects of dehydration is a natural progression of the scientific pursuit to understand the physical and mental ramifications of dehydration. It has long been known that dehydration negatively affects physical performance. Examining the effects of hydration status on cognitive function is a relatively new area of research, resulting in part from our increased understanding of hydration's impact on physical performance and advances in the discipline of cognitive neuropsychology. The available research in this area, albeit sparse, indicates that decrements in physical, visuomotor, psychomotor, and cognitive performance can occur when 2% or more of body weight is lost due to water restriction, heat, and/or physical exertion. Additional research is needed, especially studies designed to reduce, if not remove, the limitations of studies conducted to date. FREE FULL TEXT AVAILABLE IN PUBMED.

Effects of acute dehydration on brain morphology in healthy humans.

Dehydration can affect brain structure which has important implications for human health. In this study, we measured regional changes in brain structure following acute dehydration. Healthy volunteers received a structural MRI scan before and after an intensive 90-min thermal-exercise dehydration protocol. We used two techniques to determine changes in brain structure: a manual point counting technique using MEASURE, and a fully automated voxelwise analysis using SIENA. After the exercise regime, participants lost (2.2% +/- 0.5%) of their body mass. Using SIENA, we detected expansion of the ventricular system with the largest change occurring in the left lateral ventricle (P = 0.001 corrected for multiple comparisons) but no change in total brain volume (P = 0.13). Using manual point counting, we could not detect any change in ventricular or brain volume, but there was a significant correlation between loss in body mass and third ventricular volume increase (r = 0.79, P = 0.03). These results show ventricular expansion occurs following acute dehydration, and suggest that automated longitudinal voxelwise analysis methods such as SIENA are more sensitive to regional changes in brain volume over time compared with a manual point counting technique.

The relation of hydration status to cognitive performance in healthy older adults,

Little is known about the relation of hydration status to cognitive performance in older adults, who may be more vulnerable to poor hydration and cognitive impairment. We examined whether hydration status was related to cognitive functioning in 28 healthy community-dwelling older adults. Hierarchical regression models demonstrated that lower hydration status was related to slowed psychomotor processing speed and poorer attention/memory performance, after controlling for demographic variables and blood pressure

Effect of water deprivation on cognitive-motor performance in healthy men and women,

Whether mental performance is affected by slowly progressive moderate dehydration induced by water deprivation has not been examined previously. Therefore, objective and subjective cognitive-motor function was examined in 16 volunteers (8 females, 8 males, mean age: 26 yr) twice, once after 24 h of water deprivation and once during normal water intake (randomized cross-over design; 7-day interval). Water deprivation resulted in a 2.6% decrease in body weight. Neither cognitive-motor function estimated by a paced auditory serial addition task, an adaptive 5-choice reaction time test, a manual tracking test, and a Stroop word-color conflict test nor neurophysiological function assessed by auditory event-related potentials P300 (oddball paradigm) differed (P > 0.1) between the water deprivation and the control study. However, subjective ratings of mental performance changed significantly toward increased tiredness (+1.0 points) and reduced alertness (-0.9 points on a 5-point scale; both: P < 0.05), and higher levels of perceived effort (+27 mm) and concentration (+28 mm on a 100-mm scale; both: P < 0.05) necessary for test accomplishment during dehydration. Several reaction time-based responses revealed significant interactions between gender and dehydration, with prolonged reaction time in women but shortened in men after water deprivation (Stroop word-color conflict test, reaction time in women: +26 ms, in men: -36 ms, P < 0.01; paced auditory serial addition task, reaction time in women +58 ms, in men -31 ms, P = 0.05). In conclusion, cognitive-motor function is preserved during water deprivation in young humans up to a moderate dehydration level of 2.6% of body weight. Sexual dimorphism for reaction time-based performance is present. Increased subjective task-related effort suggests that healthy volunteers exhibit cognitive compensating mechanisms for increased tiredness and reduced alertness during slowly progressive moderate dehydration.

Stress- and treatment-induced elevations of Cortisol levels associated with impaired declarative memory in healthy adults.

Two studies investigated the association between cortisol levels and memory performance in healthy adults. In a first study, 13 subjects were exposed to a brief psychosocial laboratory stress ("Trier Social Stress Test") with a subsequent test of declarative memory performance. Results indicated a significant negative relationship between stress-induced cortisol levels and performance in the memory task, i.e. subjects with high cortisol response to the stressor showed poorer memory performance. In a second experiment it was investigated if cortisol, alone, i.e. independent of psychological stress, would also impair memory function. In this study, 40 healthy subjects received either 10 mg cortisol or placebo orally. One hour later they were tested for procedural and declarative memory and spatial thinking. Subjects who received cortisol showed impaired performance in the declarative memory and spatial thinking tasks but not in the procedural memory task. From these results we conclude that in healthy adults elevated free cortisol levels are associated with impaired memory function.

Differential effects of hot-humid and hot-dry environments on mental functions.

Twenty five subjects acclimatised to heat artificially were exposed to "basic effective temperatures" (BET) of 25.0 degrees, 29.6 degrees, 32.2 degrees, 33.3 degrees and 35.0 degrees C BET under conditions of both humid and dry heat. The object of the investigation was to ascertain the nature of effects of varying degrees of heat stress on mental alertness, associative learning, reasoning ability and dual-performance efficiency. A further aim was to determine the temperature levels at which impairment of psychological functions was severe enough to be of practical concern. The duration of each exposure was four hours, during which subjects performed physical exercise followed by rest every 30 min. It was found that all the psychological functions tested were adversely affected under extreme heat, and that a significant drop in various psychological functions was seen at effective temperatures of 32.2 degrees C and 33.3 degrees C in hot-humid and hot-dry conditions respectively. It is concluded that at the same effective temperatures the magnitude of the overall effect on psychological functions under humid conditions is relatively greater than that under dry conditions.

The effects of moderate heat stress on mental performance.

Moderate heat stress is believed to affect mental performance by lowering levels of arousal. Conscious effort can counteract this effect. In most experiments, raised temperatures are perceived at the start by subjects and can act as a stimulus to exert conscious effort. In practice, temperatures usually rise slowly and may therefore have a more marked effect. Thirty-six male and 36 female 17-year-old subjects in standard cotton uniforms (0.7 clo) were exposed in groups of four in a climate chamber to rising air-temperature conditions typical of occupied classrooms, in the range 20--29 degrees C. The maximum rate of rise was 4 degrees C/h. Each group performed mental work during three successive periods of 50 min with 10-min breaks between. During each break the air temperature was reduced by 3 degrees C. Sentence comprehension was significantly reduced by intermediate levels of heat stress in the third hour. A multiplication task was performed significantly more slowly in the heat by male subjects, showing a minimum at 28 degrees C. Recognition memory showed a maximum at 26 degrees C, decreasing significantly at temperatures below and above, and an independent measure of degree of certainty in recall showed a maximum at 27 degrees C. These findings are in accordance with the hypothesis of reduced arousal in moderate heat stress in the absence of conscious effort.

Improved thermoregulation caused by forced water intake in human desert dwellers.

Residents of the Negev desert in Israel sustain a mild state of dehydration. Low, concentrated urine outputs, high incidence of kidney diseases and high hematocrit ratios characterize this population. Educational programs to increase the awareness of the population to the dangers of dehydration have undoubtedly failed. It was our purpose to see whether forced increased drinking will affect the above variables. Ten healthy subjects were asked to double their normal voluntary water intake without (phase II) and with salt supplements (50 mM NaCl, 20 mM KCl) (phase III), for one week. After phases II and III significant increases in body masses, decreased concentrations of serum proteins, hemoglobin, hematocrit ratios and serum osmolalities were found. No significant changes were found in the concentrations of sodium and potassium in the serum. At the end of each phase, the subjects were asked to exercise on a bicycle ergometer for 60 min at 50% VO2max in a heated chamber at 45 degrees C, and 30%-50% relative humidity. Experiments were terminated if and when heart-rates exceeded 180 bpm or the rectal temperature increased to 39 degrees C. After both experimental phases, subjects increased their tolerance to heat, extending the exercise periods by 25% and 30%. Compared with their starting levels, hematocrit ratios, serum proteins and hemoglobin concentrations increased in phases II and III while no changes were recorded in the control period (phase I). It is suggested that spontaneous voluntary water drinking in desert dwellers is not enough to achieve a true state of "euhydration".

Fluid intake and risk of bladder and other cancers.

There are appreciable differences in total fluid intake at the individual and population level, and substantial difficulties in obtaining valid measures of fluid intake. Epidemiological studies have examined the association between fluid intake and different types of cancer. For bladder cancer, fluid consumption has been associated with a moderate increase of risk in some studies, including a multicentric case-control study from the United States, based on about 3000 cases, with a decrease in others, including the Health Professional Follow-up study, or with no material association. The evidence, therefore, is far from consistent. Sources and components of fluids were also different across different types studies. From a biological point of view, a decreased fluid intake could result in a greater concentration of carcinogens in the urine or in a prolonged time of contact with the bladder mucosa because of less frequent micturition. Carcinogenic or anticarcinogenic components of various beverages excreted in the urine may also play a role in the process. It has been suggested that fluid consumption has a favorable effect on colorectal cancer risk. Fluid intake may reduce colon cancer risk by decreasing bowel transit time and reducing mucosal contact with carcinogens. Low fluid intake may also compromise cellular concentration, affect enzyme activity in metabolic regulation, and inhibit carcinogen removal. However, epidemiological data are inadequate for evaluation. Data are sparse and inconsistent for other neoplasms, including breast cancer. The fluid constituent of foods, confounding, interactions and possible influences of specific types of beverages should be investigated further. In conclusion therefore the association between total fluid intake and cancer risk remains still open to debate.

Mild dehydration: a risk factor of constipation?

Constipation defined as changes in the frequency, volume, weight, consistency and ease of passage of the stool occurs in any age group. The most important factors known to promote constipation are reduced physical activity and inadequate dietary intake of fibres, carbohydrates and fluids. Fluid losses induced by diarrhoea and febrile illness alter water balance and promote constipation. When children increase their water consumption above their usual intake, no change in stool frequency and consistency was observed. The improvement of constipation by increasing water intake, therefore, may be effective in children only when voluntary fluid consumption is lower-than-normal for the child's age and activity level. In the elderly, low fluid intake, which may be indicative of hypohydration, was a cause of constipation and a significant relationship between liquid deprivation from 2500 to 500 ml per day and constipation was reported. Dehydration is also observed when saline laxatives are used for the treatment of constipation if fluid replacement is not maintained and may affect the efficacy of the treatment. While sulphate in drinking water does not appear to have a significant laxative effect, fluid intake and magnesium sulphate-rich mineral waters were shown to improve constipation in healthy infants. In conclusion, fluid loss and fluid restriction and thus de-or hypohydration increase constipation. It is thus important to maintain euhydration as a prevention of constipation.

Mild dehydration: a risk factor of urinary tract infection?

Bacterial growth in the urinary tract is usually prevented by host factors including bacterial eradication by urinary and mucus flow, urothelial bactericidal activity, urinary secretory IgA, and blood group antigens in secretions which interfere with bacterial adherence. Bacterial eradication from the urinary tract is partially dependent on urine flow and voiding frequency. Therefore, it seems logical to postulate a connection between fluid intake and the risk of urinary tract infections (UTIs). However, experimental and clinical data on this subject are conflicting. Experimental studies concerning the effect of water intake on susceptibility and course of UTIs were predominantly performed in the 60s and 70s. Despite many open questions, there has been no continuous research in this field. Only few clinical studies producing contradictory results are available on the influence of fluid intake concerning the risk of UTI. One explanation for the inconsistency between the data might be the uncertainty about the exact amounts of fluid intake, which was mostly recorded in questionnaires. So far, there is no definitive evidence that the susceptibility for UTI is dependent on fluid intake. Nevertheless, adequate hydration is important and may improve the results of antimicrobial therapy in UTI. Results of experimental and clinical studies concerning urinary hydrodynamics are the basis for advice given by expert committees to patients with UTI to drink large volumes of fluid, void frequently, and completely empty the bladder. The combination of the behaviourally determined aspects of host defence and not simply increasing fluid intake is important in therapy and prophylaxis of UTI.

The importance of good hydration for the prevention of chronic diseases.

There is increasing evidence that mild dehydration plays a role in the development of various morbidities. In this review, the effects of hydration status on chronic diseases are categorized according to the strength of the evidence. Positive effects of maintenance of good hydration are shown for urolithiasis (category lb evidence); constipation, exercise asthma, hypertonic dehydration in the infant, and hyperglycemia in diabetic ketoacidosis (all category IIb evidence); urinary tract infections, hypertension, fatal coronary heart disease, venous thromboembolism, and cerebral infarct (all category III evidence); and bronchopulmonary disorders (category IV evidence). For bladder and colon cancer, the evidence is inconsistent.

The importance of good hydration for day-to-day health.

The role of hydration in the maintenance of health is increasingly recognized. Studies in healthy adults show that even mild dehydration impairs a number of important aspects of cognitive function such as concentration, alertness, and short-term memory. However, due to the lack of suitable tools for assessment of hydration status, the effects of hydration on other aspects of day-to-day health and well-being remain to be demonstrated.

Mild dehydration: a risk factor for dental disease?

A review of the published international literature was undertaken to investigate whether dehydration is a risk factor for dental disease. Published evidence of associations between saliva and dental disease and between saliva and dehydration was observed, but the precise nature of these associations is unclear and no evidence of a direct link between dehydration and dental disease was found. It is concluded that no direct link between dehydration and dental disease has been proven, although there is considerable circumstantial evidence to indicate that such a link exists.

Fluid intake and the risk of bladder cancer in men.

BACKGROUND: Studies in animals have shown that the frequency of urination is inversely associated with the level of potential carcinogens in the urothelium. In humans, an increase in total fluid intake may reduce contact time between carcinogens and urothelium by diluting urinary metabolites and increasing the frequency of voiding. The data on fluid intake in relation to the risk of bladder cancer are inconclusive. METHODS: We examined the relation between total fluid intake and the risk of bladder cancer over a period of 10 years among 47,909 participants in the prospective Health Professionals Follow-up Study. There were 252 newly diagnosed cases of bladder cancer during the follow-up period. Information on total fluid intake was derived from the reported frequency of consumption of the 22 types of beverages on the food-frequency questionnaire, which was completed by each of the 47,909 participants who were free of cancer in 1986. Logistic-regression analyses were performed to adjust for known and suspected risk factors for bladder cancer. RESULTS: Total daily fluid intake was inversely associated with the risk of bladder cancer; the multivariate relative risk was 0.51 (95 percent confidence interval, 0.32 to 0.80) for the highest quintile of total daily fluid intake (>2531 ml per day) as compared with the lowest quintile ( or =1440 ml [6 cups] per day vs. 1831 ml per day vs. <735 ml per day). CONCLUSIONS: A high fluid intake is associated with a decreased risk of bladder cancer in men. FREE FULL TEXT AVAILABLE IN PUBMED.

Relationship of food groups and water intake to colon cancer risk.

The association between food groupings and adenocarcinoma of the colon was investigated in a population-based case-control study of men and women ages 30-62 years. Colon cancer cases (238 men and 186 women) diagnosed from 1985 to 1989 were identified from the Seattle-Puget Sound Surveillance, Epidemiology, and End Results Registry. Controls (224 men and 190 women) were selected using a random digit telephone dialing method. Dietary information was gathered using an 80-item food frequency questionnaire. Foods were grouped and analyzed by quartile of intake, with adjustment for age and total energy intake. Among women, a reduced risk of colon cancer was associated with a high intake of fruits and vegetables [adjusted odds ratio (OR) for highest versus lowest quartile, 0.48; 95% confidence interval (CI), 0.26-0.86; P for trend, P = 0.02]. Inverse associations were also observed for the consumption of total (hot and cold) cereals (OR, 0.47; 95% CI, 0.25-0.91; P = 0.05), dairy products (OR, 0.40; 95% CI, 0.21-0.79; P = 0.05), and water (OR for > 5 glasses/day versus 4 glasses/day versus < or = 1 glass/day, 0.68; 95% CI, 0.38-1.22; P = 0.16). Total meat consumption was associated with an increased risk of distal colon cancer among men (OR, 2.20; 95% CI, 1.08-4.48; P = 0.01). These results were not confounded by body mass index or other measured health behaviors. Results of this research support previous findings which associate intake of fruits, vegetables, grains, and dairy products with reduced colon cancer risk, and meat intake with an increased colon cancer risk. This study also reports a new finding of a possible inverse association of water consumption (glasses of plain water per day) with colon cancer risk. FREE FULL TEXT AVAILABLE IN PUBMED.

Mild dehydration induced echocardiographic signs of mild mitral valve prolapse in healthy females with prior normal cardiac findings.

This study was designed to investigate the hypothesis that mitral valve prolapse (MVP) can be induced after diuresis in women without the abnormality who have characteristic body habitus. Fifteen tall, slim, healthy female volunteers with a normal cardiac findings, echocardiogram, and history were investigated after mild diuresis with furosemide and after placebo. All subjects lost weight after furosemide and placebo administration; but mean weight loss was significantly greater after furosemide administration than after placebo administration. Echocardiography showed MVP in none of the 15 patients before treatment, in seven after administration of placebo, and in seven after administration of furosemide. Coaptation point prolapsed superior to the anulus in seven subjects with echocardiographically determined MVP. Left ventricular end-diastolic dimensions decreased significantly after placebo or furosemide administration in subjects in whom MVP developed compared with the measurement in those in whom MVP did not develop. Murmurs characteristic of MVP disappeared in all four rehydrated subjects and echocardiographic changes resolved in two of the five rehydrated subjects. Thus echocardiographically determined MVP can be induced by mild dehydration in women with phenotypic body habitus of MVP; changes may resolve with rehydration. Results suggest an explanation for variable physical examination findings in persons with MVP.

Dehydration induced by bowel preparation in older adults does not result in cognitive dysfunction.

BACKGROUND: Postoperative cognitive dysfunction occurs in a proportion of patients after noncardiac surgery. Older patients are particularly vulnerable. We hypothesized that dehydration, a common perioperative problem in the elderly, may provoke cognitive dysfunction. We used a clinical scenario free of surgical/anesthetic intervention to determine whether dehydration caused by bowel preparation results in cognitive changes. METHODS: Thirty-eight patients of an age associated with a significant incidence of postoperative cognitive dysfunction were recruited in a prospective observational study. A further control group of 14 patients undergoing sigmoidoscopy, who did not receive any bowel preparation, were matched for age, education, and gender. RESULTS: Loss of total body weight (1.5 kg [95% CI: 0.9-2.2]; P < 0.001) occurred in patients undergoing bowel preparation (2.0 [95% CI: 1.3-2.6] percent total body weight), whereas sigmoidoscopy patients' weight did not change (0.17 kg [95% CI: -0.2-0.6 kg]; P = 0.26). Total body water, derived from foot bioimpedance, indicated dehydration in the bowel preparation group only (mean impedance change 36 [Omega] [95% CI; 25-46], P < 0.001) with a calculated decrease of 2.6% in total body water (95% CI: 1.1-4.8; P < 0.001). Hematocrit increased after bowel preparation only (prebowel prep 0.41 [0.40-0.43] versus postbowel prep 0.43 [0.42-0.45]; P = 0.003). Despite this degree of dehydration, all cognitive tests were within 1 SD of the population mean of normal values. Repeated measures analysis of variance did not reveal significant changes for within group comparisons over time for motor speed (P = 0.51), executive function (P = 0.57), Trail Making Tests and recall (P = 0.88), other than a 3 s slowing in learning ability (Rey Auditory Verbal Learning Test; P = 0.04). Hydration status did not affect learning (P = 0.42), recall (P = 0.30) motor speed (P = 0.36), or executive function tests (P = 0.26). CONCLUSION: Dehydration alone does not result in cognitive dysfunction. FREE FULL TEXT AVAILABLE IN PUBMED.

Oral rehydration therapy before surgery in elderly patients.

Oral rehydration therapy before surgery may be useful for elderly patients in perioperative management especially induction of general anesthesia, as they cannot preserve water in the body sufficiently. In elderly patients oral rehydration therapy is favorable to intravenous hydration as in younger patients. However, if swallowing is impaired or there are risks for aspiration, gastric emptying rate is decreased; gastroesophageal reflux disease is pointed out;\ncognitive function is disordered; or delirium has appeared, oral rehydration therapy should be carefully considered. It may be necessary to provide preoperative oral rehydration therapy to high risk elderly patients when they are hospitalized and they should be watched for taking oral rehydration solution soon by hospital nurses.

Preoperative oral hydration for pregnant women.

Preoperative oral hydration is an important component of "enhanced recovery alter surgery" strategies. This was originally developed for patients undergoing colon surgery. The Obstetric Anesthesia Practice Guideline issued by American Society of Anesthesiologists states that intake of minimum amount of clear fluid 2 hours prior to surgery may be safe. However, anesthesiologists have to consider physiological changes that parturients undergo during pregnancy, such as increased risk of aspiration and impaired glucose tolerance. We also have to consider the potential effect of glucose loading on neonates. Mothers are more likely to develop ketosis by glucose loading. It also stimulates insulin release in the fetus, which can result in neonatal hypoglycemia. In addition, sodium overloading may deteriorate intra-vascular dehydration and cause lung edema to mothers. On the other hand, oral hydration can alleviate a sense of thirst and increase maternal satisfaction. Our data showed that maternal urinal ketone body at delivery tended to decrease with oral hydration during labor. Moreover, some articles suggest that oral hydration may improve utero-placental perfusion. Therefore, we have to balance risks and benefits of oral hydration in parturients. Further investigations are needed among this specific subgroup of patients in order to establish the safe application of preoperative oral hydration.

Reduced hydration status characterized by disproportionate elevation of blood urea nitrogen to serum creatinine among the patients with cerebral infarction.

The significance of fluid metabolism among the patients with cerebral infarction has barely mentioned in the literature despite the several reports suggesting the potential risk of reduced hydration status for the development of cerebral infarction. The aim of the this study is to explore the validity of the presumable relationship between hydration status and cerebral infarction. Ninety-seven patients with cerebral infarction from April 1, 2008 to March 31, 2009 were retrospectively investigated, and their hydration status were evaluated by using several clinical parameters such as a blood urea nitrogen to serum creatinine (BUN/Cr) ratio of >25 and plasma osmolality. Subjects with active infection, congestive heart failure, hepatic failure, gastrointestinal bleeding, or a malignancy were excluded since these conditions should modulate the absolute value of BUN/Cr ratio without a change in hydration status. Twenty-eight patients (29%) were considered as having reduced hydration status. The BUN/Cr ratio decreased significantly after the initiation of medical support (median 21.3; IR: 18.1-24.6), including oral or parenteral fluid supplementation, in comparison to the values at the time of patient admission (median 30.0; IR: 26.8-40.7; p<0.0001). Similar decreases were also observed in the hematocrit, hemoglobin, and plasma osmolality. The group considered to have reduced hydration status had a significantly higher prevalence of cardioembolic stroke than the other subjects. The hydration status may be a contributing factor to subtypes of cerebral infarction. Whether our findings are also the case with overall patients with cerebral infarction should be evaluated in greater detail.

Dehydration: why is it still a problem?

Reports from organisations such as the Care Quality Commission have identified many hospital patients, particularly older people, are suffering from dehydration. A range of national initiatives have emphasised the importance of hydration and nutrition, and offered guidance to help address shortcomings, yet the problems persist. This article examines the interplay of factors that affect the assessment and identification of dehydration, and its prevention. It also offers strategies to help nurses to ensure patients receive adequate hydration.

Variation in attitudes towards artificial hydration at the end of life: a systematic literature review.

PURPOSE OF REVIEW: Artificial hydration in end-of-life care is an important and emotive topic that frequently raises concerns from patients, relatives and healthcare professionals (HCPs). The aim of this review was to give an overview of currently available evidence around opinions and attitudes towards artificial hydration at the end of life. RECENT FINDING: In total 11 studies reported on opinions towards providing artificial hydration, nine studies reported on attitudes towards the effect of artificial hydration on quality-of-life and four studies towards its effect on survival. Reported percentages of respondents in favour of providing artificial hydration at the end of life varied from 22 to 100% and for nonprovision from 0 to 75%. One-third of the general public has been found to think that artificial hydration improves comfort, while among patients a majority feels it can have a physical or psychological benefit. HCPs were found to be less optimistic: 1-43% thought patients benefit from artificial hydration at the end of life. HCPs mostly agree artificial hydration does not prolong survival, although up to 89% of patients expect it does. SUMMARY: Opinions and attitudes towards the use of artificial hydration at the end of life vary. Communication of this imperative topic in end-of-life care is important for better care and should be research-based.

Does having a drink help you think? 6-7-Year-old children show improvements in cognitive performance from baseline to test after having a drink of water

Little research has examined the effect of water consumption on cognition in children. We examined whether drinking water improves performance from baseline to test in twenty-three 6-7-year-old children. There were significant interactions between time of test and water group (water/no water), with improvements in the water group on thirst and happiness ratings, visual attention and visual search, but not visual memory or visuomotor performance. These results indicate that even under conditions of mild dehydration, not as a result of exercise, intentional water deprivation or heat exposure, children's cognitive performance can be improved by having a drink of water.

An exploration of factors that influence the regular consumption of water by Irish primary school children.

BACKGROUND: Inadequate hydration has been linked to many factors that may impact on children's education and health. Teachers play an important role in the education and behaviour of children. Previous research has demonstrated low water intake amongst children and negative teachers' attitudes to water in the classroom. The present study aimed to explore teachers' knowledge about water and the perceived barriers to allowing children access to water during lesson time. METHODS: In-depth interviews were conducted with 12 teachers from primary schools in the Midlands of Ireland. Interviews were continued until there was saturation of the data. Thematic analysis of the data was conducted. RESULTS: Participants had a poor knowledge of hydration requirements and the associated health benefits and effect on concentration. Low water intake amongst teachers and pupils, and barriers such as disruption to class and increased need to urinate, were reported. Teachers identified the hydration effect on learning as the education message most likely to influence the decision to allow water in the classroom. CONCLUSIONS: The issues, opinions and perceived barriers raised by teachers as part of this qualitative research provide a basis for future health promotion around water.

Dehydration Affects Brain Structure and Function in Healthy Adolescents

It was recently observed that dehydration causes shrinkage of brain tissue and an associated increase in ventricular volume. Negative effects of dehydration on cognitive performance have been shown in some but not all studies, and it has also been reported that an increased perceived effort may be required following dehydration. However, the effects of dehydration on brain function are unknown. We investigated this question using functional magnetic resonance imaging (fMRI) in 10 healthy adolescents (mean age = 16.8, five females). Each subject completed a thermal exercise protocol and nonthermal exercise control condition in a cross-over repeated measures design. Subjects lost more weight via perspiration in the thermal exercise versus the control condition (P < 0.0001), and lateral ventricle enlargement correlated with the reduction in body mass (r = 0.77, P = 0.01). Dehydration following the thermal exercise protocol led to a significantly stronger increase in fronto-parietal blood-oxygen-level-dependent (BOLD) response during an executive function task (Tower of London) than the control condition, whereas cerebral perfusion during rest was not affected. The increase in BOLD response after dehydration was not paralleled by a change in cognitive performance, suggesting an inefficient use of brain metabolic activity following dehydration. This pattern indicates that participants exerted a higher level of neuronal activity in order to achieve the same performance level. Given the limited availability of brain metabolic resources, these findings suggest that prolonged states of reduced water intake may adversely impact executive functions such as planning and visuo-spatial processing.

The effect of voluntary dehydration on cognitive functions of elementary school children

AIMS: (1) To describe the occurrence of voluntary dehydration in two classes of elementary school students as expressed by their morning and noon-time urine osmolality; and (2) to determine the relationship between the children's scores on cognitive tests and their state of hydration. METHODS: Group comparison among fifty-eight sixth-grade students (age range 10.1-12.4 y old) during mid-June at two schools in a desert town. Morning and noon-time urine samples were collected in school, and five cognitive tests were scored in the morning and at noon-time. Main outcome measures: (1) morning and noon-time urine osmolality; (2) scores of five cognitive tests (hidden figures, auditory number span, making groups, verbal analogies, and number addition) that were applied in the morning and at noon-time. RESULTS: Thirty-two students were dehydrated (urine osmolality above 800 mosm/kg H(2)O) in the morning. An individual's noon-time urine osmolality was highly related to morning osmolality (r=0.67, p=0.000). The morning cognitive scores were similar in the hydrated and dehydrated students (p=0.443). The adjusted mean scores of the noon-time tests, with the morning test scores as covariates, demonstrated an overall positive trend in four of the five tests in favor of the hydrated group (p=0.025). The effect was mainly due to the auditory number span test (p=0.024). CONCLUSION: Voluntary dehydration is a common phenomenon in school-aged children that adversely affects cognitive functions.

The effect of the consumption of water on the memory and attention of children

The impact of asking children to drink water during their school days, and its possible influence on school performance, has been little considered using intervention studies. Therefore in the afternoon the cognitive functioning of 40 children (mean of 8 years and 7 months) was assessed twice, once after drinking 300 ml of water and on another day when no water was provided. Memory was assessed by the recall of 15 previously presented objects. Recall was significantly better on the occasions when water had been consumed. The ability to sustain attention was measured by asking the child to respond to a light that followed an auditory warning after a delay of either 3 or 12 s. The ability to sustain attention was not significantly influenced by whether water had been drunk.

The effect of voluntary dehydration on cognitive functions of elementary school children.

AIMS: (1) To describe the occurrence of voluntary dehydration in two classes of elementary school students as expressed by their morning and noon-time urine osmolality; and (2) to determine the relationship between the children's scores on cognitive tests and their state of hydration. METHODS: Group comparison among fifty-eight sixth-grade students (age range 10.1-12.4 y old) during mid-June at two schools in a desert town. Morning and noon-time urine samples were collected in school, and five cognitive tests were scored in the morning and at noon-time. Main outcome measures: (1) morning and noon-time urine osmolality; (2) scores of five cognitive tests (hidden figures, auditory number span, making groups, verbal analogies, and number addition) that were applied in the morning and at noon-time. RESULTS: Thirty-two students were dehydrated (urine osmolality above 800 mosm/kg H(2)O) in the morning. An individual's noon-time urine osmolality was highly related to morning osmolality (r=0.67, p=0.000). The morning cognitive scores were similar in the hydrated and dehydrated students (p=0.443). The adjusted mean scores of the noon-time tests, with the morning test scores as covariates, demonstrated an overall positive trend in four of the five tests in favor of the hydrated group (p=0.025). The effect was mainly due to the auditory number span test (p=0.024). CONCLUSION: Voluntary dehydration is a common phenomenon in school-aged children that adversely affects cognitive functions.

Voluntary hypohydration in 10- to 12-year-old boys,

This study was performed to determine whether a) children voluntarily dehydrate while exercising in hot climate; b) such dehydration affects their well-being and thermoregulation. Eleven 10p to 12-yr old, partially acclimatized boys underwent two work-in-the-heat protocols (cycle rides, 45% aerobic capacity at 39 degrees C, 45% rh). During one session they drank only voluntarily when thirsty (VD). In the other, drinking was forced (FD) to replenish fluid losses. VD induced a progressively increasing fluid loss (0.3% of body wt.h-1) due to insufficient drinking (72% of intake in FD). URinary output was lower (55.7 vs. 81.6 ml.h-1) and its osmolality higher (880 vs. 523 meq.1-1) than during FD. Sweat rate, rectal (Tre) and mean skin (T-sk) temperatures, heart rate, rate of perceived exertion, sweat gland counts, blood hemoglobin, hematocrit (Hct), serum electrolytes, and total proteins did not differ between sessions. However, the rise of Tre, Hct, and proteins positively correlated with hypohydration level. It is concluded that exercising children progressively dehydrate when not forced to drink. At equal levels of % weight loss they have greater Tre rise than do lean adults.

A study of the association between children's access to drinking water in primary schools and their fluid intake: can water be ‘cool’ in school?

BACKGROUND: Water is essential for health. The 'Water is Cool in School' campaign promoted improved drinking water access in UK schools. Implementation has been patchy, and impact has not been studied. The aim of this study is to determine whether fluid intake and frequency of toilet visits are associated with children's access to drinking water in the classroom. METHODS: A total of 145 schoolchildren in Year 2 (aged 6-7 years) and 153 in Year 5 (aged 9-10 years) classes were studied in six Southampton schools. Total fluid intake and toilet visits were recorded during one school day. Schools were recruited according to drinking policy: 'prohibited access' = water prohibited in classroom; 'limited access' = water allowed in classroom but not on the desk; and 'free access' = water bottle encouraged on the desk. Data were analysed on an intention-to-treat basis. RESULTS: In total, 120 children in prohibited access, 91 in limited access and 87 in free access settings were recruited. Total fluid intake was significantly higher in Year 2 free access schools (geometric mean 293, range 104-953 mL) compared with prohibited access schools (geometric mean 189, range 0-735 mL, P=0.046), in Year 5 free access schools (geometric mean 489, range 88-1200 mL) compared with prohibited access schools (geometric mean 206, range 0-953 mL, P=0.001), and in free access versus limited access schools (geometric mean 219, range 0-812 mL, P=0.003). A total of 81% and 80% of children in prohibited and limited access schools, respectively, consumed below the minimum recommended amount of total fluid at school, compared with 46.5% in the free access schools. In total, 34.6% of children did not use the toilets at all during the school day. There was no trend observed between water access and frequency of toilet visits (median of 1 trip for each group, P=0.605). CONCLUSION: Most children have an inadequate fluid intake in school. Free access to drinking water in class is associated with improved total fluid intake. Primary schools should promote water drinking in class.

A study of the association between children's access to drinking water in primary schools and their fluid intake: can water be ‘cool’ in school?

BACKGROUND: Water is essential for health. The 'Water is Cool in School' campaign promoted improved drinking water access in UK schools. Implementation has been patchy, and impact has not been studied. The aim of this study is to determine whether fluid intake and frequency of toilet visits are associated with children's access to drinking water in the classroom. METHODS: A total of 145 schoolchildren in Year 2 (aged 6-7 years) and 153 in Year 5 (aged 9-10 years) classes were studied in six Southampton schools. Total fluid intake and toilet visits were recorded during one school day. Schools were recruited according to drinking policy: 'prohibited access' = water prohibited in classroom; 'limited access' = water allowed in classroom but not on the desk; and 'free access' = water bottle encouraged on the desk. Data were analysed on an intention-to-treat basis. RESULTS: In total, 120 children in prohibited access, 91 in limited access and 87 in free access settings were recruited. Total fluid intake was significantly higher in Year 2 free access schools (geometric mean 293, range 104-953 mL) compared with prohibited access schools (geometric mean 189, range 0-735 mL, P=0.046), in Year 5 free access schools (geometric mean 489, range 88-1200 mL) compared with prohibited access schools (geometric mean 206, range 0-953 mL, P=0.001), and in free access versus limited access schools (geometric mean 219, range 0-812 mL, P=0.003). A total of 81% and 80% of children in prohibited and limited access schools, respectively, consumed below the minimum recommended amount of total fluid at school, compared with 46.5% in the free access schools. In total, 34.6% of children did not use the toilets at all during the school day. There was no trend observed between water access and frequency of toilet visits (median of 1 trip for each group, P=0.605). CONCLUSION: Most children have an inadequate fluid intake in school. Free access to drinking water in class is associated with improved total fluid intake. Primary schools should promote water drinking in class.

Relation between hydration status in children and their dietary profile-results from the DONALD study,

OBJECTIVE: To describe associations between hydration status and dietary behaviour in children, as current research indicates that hydration status is influenced by nutrition vice versa, hydration status may influence dietary behaviour. DESIGN: Cross-sectional analyses of data from the Dortmund Nutritional and Anthropometric Longitudinally Designed Study, (DONALD) using 24-h urine samples to determine the hydration status and 3-day weighed food records to describe the dietary profile of the children. SETTING: Secondary analyses of data from an observational study. SUBJECTS: A group of 4-11 year old children living in Dortmund, Germany; N=717. METHODS: Hydration status was determined by calculating the 'free water reserve', using analyses of the 24-h urine samples. Nutrient intake per day was calculated from the 3-day weighed food records. Children were categorized into groups of hydration status and analysed for significant differences in their dietary profile. RESULTS: Children in the highest group of the hydration status had significant higher total water intake, lower energy density of the diet and a lower proportion of metabolic water compared to children in the lowest group of the hydration status. In addition, analyses showed - although not significant in all subgroups - that better hydrated children consumed more water from beverages and water-supplying foods and less energy from fat. CONCLUSIONS: Euhydrated children, that are children in the highest group of hydration status, had a more preferable dietary profile than children at risk of insufficient hydration. SPONSORSHIP: Funding for the DONALD Study and its analyses is provided by the Ministry of Innovation, Science, Research and Technology of the State of North Rhine-Westphalia, Germany.

Hydration-sensitive Gene Expression in Brain.

Dehydration has a profound influence on neuroexcitability. The mechanisms remained, however, incompletely understood. The present study addressed the effect of water deprivation on gene expression in the brain. To this end, animals were exposed to a 24 hours deprivation of drinking water and neuronal gene expression was determined by microarray technology with subsequent confirmation by RT-PCR. As a result, water deprivation was followed by significant upregulation of clathrin (light polypeptide Lcb), serum/glucocorticoid-regulated kinase (SGK) 1, and protein kinase A (PRKA) anchor protein 8-like. Water deprivation led to downregulation of janus kinase and microtubule interacting protein 1, neuronal PAS domain protein 4, thrombomodulin, purinergic receptor P2Y- G-protein coupled 13 gene, gap junction protein beta 1, neurotrophin 3, hyaluronan and proteoglycan link protein 1, G protein-coupled receptor 19, CD93 antigen, forkhead box P1, suppressor of cytokine signaling 3, apelin, immunity-related GTPase family M, serine (or cysteine) peptidase inhibitor clade B member 1a, serine (or cysteine) peptidase inhibitor clade H member 1, glutathion peroxidase 8 (putative), discs large (Drosophila) homolog-associated protein 1, zinc finger and BTB domain containing 3, and H2A histone family member V. Western blotting revealed the downregulation of forkhead box P1, serine (or cysteine) peptidase inhibitor clade H member 1, and gap junction protein beta 1 protein abundance paralleling the respective alterations of transcript levels. In conclusion, water deprivation influences the transcription of a wide variety of genes in the brain, which may participate in the orchestration of brain responses to water deprivation.

Hydration-sensitive Gene Expression in Brain.

Dehydration has a profound influence on neuroexcitability. The mechanisms remained, however, incompletely understood. The present study addressed the effect of water deprivation on gene expression in the brain. To this end, animals were exposed to a 24 hours deprivation of drinking water and neuronal gene expression was determined by microarray technology with subsequent confirmation by RT-PCR. As a result, water deprivation was followed by significant upregulation of clathrin (light polypeptide Lcb), serum/glucocorticoid-regulated kinase (SGK) 1, and protein kinase A (PRKA) anchor protein 8-like. Water deprivation led to downregulation of janus kinase and microtubule interacting protein 1, neuronal PAS domain protein 4, thrombomodulin, purinergic receptor P2Y- G-protein coupled 13 gene, gap junction protein beta 1, neurotrophin 3, hyaluronan and proteoglycan link protein 1, G protein-coupled receptor 19, CD93 antigen, forkhead box P1, suppressor of cytokine signaling 3, apelin, immunity-related GTPase family M, serine (or cysteine) peptidase inhibitor clade B member 1a, serine (or cysteine) peptidase inhibitor clade H member 1, glutathion peroxidase 8 (putative), discs large (Drosophila) homolog-associated protein 1, zinc finger and BTB domain containing 3, and H2A histone family member V. Western blotting revealed the downregulation of forkhead box P1, serine (or cysteine) peptidase inhibitor clade H member 1, and gap junction protein beta 1 protein abundance paralleling the respective alterations of transcript levels. In conclusion, water deprivation influences the transcription of a wide variety of genes in the brain, which may participate in the orchestration of brain responses to water deprivation.

Randomized trial of bioelectrical impedance analysis versus clinical criteria for guiding ultrafiltration in hemodialysis patients: effects on blood pressure, hydration status, and arterial stiffness.

BACKGROUND: Chronic fluid overload is common in maintenance hemodialysis (HD) patients and is associated with severe cardiovascular complications, such as arterial hypertension, left ventricular hypertrophy, congestive heart failure, and arrhythmia. Therefore, a crucial target of HD is to achieve the so-called dry weight; however, the best way to assess fluid status and dry weight is still unclear. Dry weight is currently determined in most dialysis units on a clinical basis, and it is commonly defined as the lowest body weight a patient can tolerate without developing intra-dialytic or inter-dialytic hypotension or other symptoms of dehydration. One of the most promising methods that have emerged in recent years is bioelectrical impedance analysis (BIA), which estimates body composition, including hydration status, by measuring the body's resistance and reactance to electrical current. Our objective was to study the effect BIA-guided versus clinical-guided ultrafiltration on various cardiovascular disease risk factors and markers in HD patients. MATERIALS AND METHODS: We included 135 HD patients from a single center in a prospective study, aiming to compare the long-term (12 months) effect of BIA-based versus clinical-based assessment of dry weight on blood pressure (BP), pulse wave velocity (PWV), and serum N-terminal fragment of B-type natriuretic peptide (NT-proBNP). The body composition was measured using the portable whole-body multifrequency BIA device, Body Composition Monitor-BCM(®) (Fresenius Medical Care, Bad Homburg, Germany). RESULTS: In the "clinical" group there were no changes in BP, body mass index (BMI), and body fluids. The PWV increased from 7.9 ± 2.5 to 9.2 ± 3.6 m/s (P = 0.002), whereas serum NT-proBNP decreased from 5,238 to 3,883 pg/ml (P = 0.05). In the "BIA" group, BMI and body volumes also did not change; however, there was a significant decrease in both systolic BP, from 144.6 ± 14.7 to 135.3 ± 17.8 mmHg (P < 0.001), and diastolic BP, from 79.5 ± 9.7 to 73.2 ± 11.1 mmHg (P < 0.001). In this group, PWV also decreased from 8.2 ± 2.3 to 6.9 ± 2.3 m/s (P = 0.001) and NT-proBNP decreased from 7,552 to 4,561 pg/ml (P = 0.001). CONCLUSION: BIA is not inferior and possibly even better than clinical criteria for assessing dry weight and guiding ultrafiltration in HD patients.

Cortical activation and lamina terminalis functional connectivity during thirst and drinking in humans.

The pattern of regional brain activation in humans during thirst associated with dehydration, increased blood osmolality and decreased blood volume is not known. Furthermore, there is little information available about associations between activation in osmoreceptive brain regions such as the organum vasculosum of the lamina terminalis and the brain regions implicated in thirst and its satiation in humans. With the objective of investigating the neuroanatomical correlates of dehydration and activation in the ventral lamina terminalis this study involved exercise-induced sweating in 15 people and measures of regional cerebral blood flow using a functional magnetic resonance imaging (fMRI) technique called pulsed arterial spin labelling. Regional brain activations during dehydration, thirst and post-drinking were consistent with the network previously identified during systemic hypertonic infusions, thus providing further evidence that the network is involved in monitoring body fluid and the experience of thirst. Regional cerebral blood flow (rCBF) measurements in the ventral lamina terminalis were correlated with whole brain rCBF measures to identify regions that correlated with the osmoreceptive region. Regions implicated in the experience of thirst were identified including cingulate cortex, prefrontal cortex, striatum, parahippocampus and cerebellum. Furthermore, the correlation of rCBF between the ventral lamina terminalis and the cingulate cortex and insula was different for the states of thirst and recent drinking, suggesting that functional connectivity of the ventral lamina terminal is a dynamic process influenced by hydration status and ingestive behavior.

Eating for Performance: Bringing Science to the Training Table.

Despite many advances in nutritional knowledge and dietary practices, sports nutrition-associated issues, such as fatigue, loss of strength and stamina, loss of speed, and problems with weight management and inadequate energy intake, are common. Sound nutritional practices and well-designed patterns of eating are not awarded the same priority as training and many athletes fail to recognize that poor eating habits or suboptimal hydration choices may detract from athletic performance. Those who care for athletes and active individuals must take an active role in their nutritional well-being. This article reviews the present generally accepted principles for nutritional management in sport.

Estimation of normal hydration in dialysis patients using whole body and calf bioimpedance analysis.

Prescription of an appropriate dialysis target weight (dry weight) requires accurate evaluation of the degree of hydration. The aim of this study was to investigate whether a state of normal hydration (DW(cBIS)) as defined by calf bioimpedance spectroscopy (cBIS) and conventional whole body bioimpedance spectroscopy (wBIS) could be characterized in hemodialysis (HD) patients and normal subjects (NS). wBIS and cBIS were performed in 62 NS (33 m/29 f) and 30 HD patients (16 m/14 f) pre- and post-dialysis treatments to measure extracellular resistance and fluid volume (ECV) by the whole body and calf bioimpedance methods. Normalized calf resistivity (ρ(N)(,5)) was defined as resistivity at 5 kHz divided by the body mass index. The ratio of wECV to total body water (wECV/TBW) was calculated. Measurements were made at baseline (BL) and at DW(cBIS) following the progressive reduction of post-HD weight over successive dialysis treatments until the curve of calf extracellular resistance is flattened (stabilization) and the ρ(N)(,5) was in the range of NS. Blood pressures were measured pre- and post-HD treatment. ρ(N)(,5) in males and females differed significantly in NS. In patients, ρ(N)(,5) notably increased with progressive decrease in body weight, and systolic blood pressure significantly decreased pre- and post-HD between BL and DW(cBIS) respectively. Although wECV/TBW decreased between BL and DW(cBIS), the percentage of change in wECV/TBW was significantly less than that in ρ(N)(,5) (-5.21 ± 3.2% versus 28 ± 27%, p < 0.001). This establishes the use of ρ(N)(,5) as a new comparator allowing a clinician to incrementally monitor removal of extracellular fluid from patients over the course of dialysis treatments. The conventional whole body technique using wECV/TBW was less sensitive than the use of ρ(N)(,5) to measure differences in body hydration between BL and DW(cBIS).

Urine specific gravity as a predictor of early neurological deterioration in acute ischemic stroke.

We previously found that a blood urea nitrogen/creatinine (BUN/Cr) ratio >15 is an independent predictor of early neurological deterioration after acute ischemic stroke, which suggests that dehydration may be a cause of early deterioration. The aim of this study was to determine whether urine specific gravity, which is another indicator of hydration status and one that is more easily obtained, is also an independent predictor of early deterioration or stroke-in-evolution (SIE). Demographic and clinical data were recorded at admission from patients with acute ischemic stroke who were prospectively enrolled from October 2007 to June 2010. We compared patients with and without stroke-in-evolution (based on an increase of 3 points or more points on the National Institutes of Health Stroke Scale within 3 days). Univariate and multivariate statistical analyses were carried out. A total of 317 patients (43 SIE and 274 non-SIE) were enrolled; the first 196 patients comprised the cohort of our previous study. The only two independent predictors of early deterioration or SIE were BUN/Cr>15 and urine specific gravity>1.010. After adjusting for age and gender, patients with a urine specific gravity>1.010 were 2.78 times more likely to develop SIE (95% CI=1.11-6.96; P=0.030). Urine specific gravity may be useful as an early predictor of early deterioration in patients with acute ischemic stroke. Patients with urine specific gravity⩽1.010 therefore may have a reduced likelihood of early neurological deterioration.

Artificial nutrition and hydration in the last week of life in cancer patients. A systematic literature review of practices and effects.

BACKGROUND: The benefits and burdens of artificial nutrition (AN) and artificial hydration (AH) in end-of-life care are unclear. We carried out a literature review on the use of AN and AH in the last days of life of cancer patients. Materials and methods: We systematically searched for papers in PubMed, CINAHL, PsycInfo and EMBASE. All English papers published between January 1998 and July 2009 that contained data on frequencies or effects of AN or AH in cancer patients in the last days of life were included. RESULTS: Reported percentages of patients receiving AN or AH in the last week of life varied from 3% to 53% and from 12% to 88%, respectively. Five studies reported on the effects of AH: two found positive effects (less chronic nausea, less physical dehydration signs), two found negative effects (more ascites, more intestinal drainage) and four found also no effects on terminal delirium, thirst, chronic nausea and fluid overload. No study reported on the sole effect of AN. CONCLUSIONS: Providing AN or AH to cancer patients who are in the last week of life is a frequent practice. The effects on comfort, symptoms and length of survival seem limited. Further research will contribute to better understanding of this important topic in end-of-life care.

 

A pilot study to assess if urine specific gravity and urine colour charts are useful indicators of dehydration in acute stroke patients.

The purpose of this pilot study was to examine whether urine specific gravity and urine colour could provide an early warning of dehydration in stroke patients compared with standard blood indicators of hydration status. Background. Dehydration after stroke has been associated with increased blood viscosity, venous thrombo-embolism and stroke mortality at 3-months. Earlier identification of dehydration might allow us to intervene to prevent significant dehydration developing or reduce its duration to improve patient outcomes. Methods. We recruited 20 stroke patients in 2007 and measured their urine specific gravity with urine test strips, a refractometer, and urine colour of specimens taken daily on 10 consecutive days and compared with the routine blood urea:creatinine ratios over the same period to look for trends and relationships over time. The agreement between the refractometer, test strips and urine colour were expressed as a percentage with 95% confidence intervals. Results. Nine (45%) of the 20 stroke patients had clinical signs of dehydration and had a significantly higher admission median urea:creatinine ratio (P=0.02, Mann-Whitney U-test). There were no obvious relationships between urine specific gravity and urine colour with the urea:creatinine ratio. Of the 174 urine samples collected, the refractometer agreed with 70/174 (40%) urine test strip urine specific gravity and 117/174 (67%) urine colour measurements. Conclusions. Our results do not support the use of the urine test strip urine specific gravity as an early indicator of dehydration. Further research is required to develop a practical tool for the early detection of dehydration in stroke patients.

Fluid replacement requirements for child athletes.

Thermoregulatory responses to exercise differ in prepubertal athletes compared with their adult counterparts. It is important, therefore, to consider fluid requirements specific to this age group to prevent risks of dehydration and diminished sports performance. Relative to their body size, children demonstrate lower sweat water losses during exercise than adults. Nonetheless, percentage levels of incurred dehydration are similar in pre- and postpubertal athletes. Moreover, voluntary (ad libitum) drinking volumes in children in respect to their body size are comparable or greater than those of adults. Given an adequate opportunity to drink during exercise, volume intake driven by thirst should be expected to prevent significant levels of dehydration in child athletes. The amount can be calculated conservatively as an hourly fluid intake of 13 mL/kg (6 mL/lb) bodyweight. Equally important is post-exercise fluid replenishment (approximately 4 mL/kg [2 mL/lb] for each hour of exercise) to avoid initiating subsequent exercise bouts in a dehydrated state. Choice of fluid should be dictated by taste preference, since volume of intake, rather than fluid content, is the most critical issue in child athletes. Since children may lack motivation for proper fluid intake behaviours, the responsibility falls to coaches and parents to assure that young athletes receive appropriate hydration during and after exercise bouts.

Fluid balance of elite Brazilian youth soccer players during consecutive days of training.

In this study we investigated pre-training hydration status, fluid intake, and sweat loss in 20 elite male Brazilian adolescent soccer players (mean ± s: age 17.2 ± 0.5 years; height 1.76 ± 0.05 m; body mass 69.9 ± 6.0 kg) on three consecutive days of typical training during the qualifying phase of the national soccer league. Urine specific gravity (USG) and body mass changes were evaluated before and after training sessions to estimate hydration status. Players began the days of training mildly hypohydrated (USG > 1.020) and fluid intake did not match fluid losses. It was warmer on Day 1 (33.1 ± 2.4°C and43.4 ± 3.2% relative humidity; P < 0.05) and total estimated sweat losses (2822 ± 530 mL) and fluid intake (1607 ± 460 mL) were significantly higher (P < 0.001) compared with Days 2 and 3. Data also indicate a significant correlation between the extent of sweat loss and the volume of fluid consumed (Day 1: r = 0.560, P = 0.010; Day 2: r = 0.445, P = 0.049; Day 3: r = 0.743, P = 0.0001). We conclude that young, native tropical soccer players arrive hypohydrated to training and that they exhibit voluntary dehydration; therefore, enhancing athletes' self-knowledge of sweat loss during training might help them to consume sufficient fluid to match the sweat losses.

Decreased mortality in acute pancreatitis related to early aggressive hydration.

OBJECTIVE: Early aggressive intravenous hydration is believed to prevent morbidity and mortality by preventing intravascular volume depletion and maintaining perfusion of the pancreas possibly preventing pancreatic necrosis. The following study was initiated to determine the relationship between the observed decrease in mortality and the role of early aggressive hydration. METHODS: A consecutive series of patients with acute pancreatitis from a single community hospital in1998 were compared to a consecutive series of patients with acute pancreatitis from the same institution in 2008. RESULTS: Significantly more patients developed pancreatic necrosis; 26 (15%) of 173 patients in 1998 compared to 4 (4%) of 113 patients in 2008. The mean rate of hydration was significantly higher in 2008 compared with that in 1998 (P=0.02). In 1998, hydration was provided at 184 mL/h during the first 6 hours and 188 mL/h during the first 12 hours compared with 284 mL/h during the first 6 hours and 221 mL/h during the first 12 hours in 2008. There was a significant decrease in mortality in 2008 compared with that in 1998 (3.5% vs 12%, P=0.03). CONCLUSIONS: The decrease in mortality seen in patients with acute pancreatitis during the last decade may be related to the increased aggressive hydration preventing pancreatic necrosis.

Fat-free mass hydration in newborns: assessment and implications for body composition studies.

AIM: Equipment (Pea Pod) offering new possibilities to assess infant body composition has recently become available and has already been used in several studies. In the Pea Pod, body density is converted to body composition using one of two models ('Fomon' or 'Butte') with different water content in fat-free mass (hydration factor, HF). In healthy full-term infants, we assessed HF and its biological variability in 12 newborns and calculated body composition using the two models at 1 and 12 weeks in 108 infants. Body weight and volume were assessed in Pea Pod, and body water was assessed using isotope dilution. RESULTS: Hydration factor was 80.9% with low biological variability (0.8% of average HF). Body fat (%) was significantly lower at 1 and 12 weeks when calculated using the 'Butte' model than when using the 'Fomon' model. The difference was more pronounced at one than at 12 weeks. CONCLUSION: Our HF value agrees with that in the 'Fomon' model, its low biological variability can be reconciled with the statement that Pea Pod is accurate in newborns and 'Fomon' is the best available model for studies in Pea Pod.

Exercise-associated hyponatremia: the influence of pre-exercise carbohydrate status combined with high volume fluid intake on sodium concentrations and fluid balance.

To evaluate the effect of hydration and carbohydrate (CHO) status on plasma sodium, fluid balance, and regulatory factors (IL-6 & ADH) during and after exercise; 10 males completed the following conditions: low CHO, euhydrated (fluid intake = sweat loss) (LCEH); low CHO, dehydrated (no fluid) (LCDH); high CHO, euhydrated (HCEH); and high CHO, dehydrated (HCDH). Each trial consisted of 90-min cycling at 60% VO(2) max in a 35°C environment followed by 3-h rehydration (RH). During RH, subjects received either 150% of sweat loss (LCDH & HCDH) or an additional 50% of sweat loss (LCEH and HCEH). Blood was analyzed for glucose, IL-6, ADH, and Na(+). Post-exercise Na(+) was greater (p < 0.001) for LCDH and HCDH (141.7 + 0.72 and 141.6 + 0.4 mM) versus LCEH and HCEH (136.4 + 0.6 and 135.9 + 0.3 mM). Post-exercise IL-6 was similar in all conditions, and post-exercise ADH was greater (p = 0.01) in dehydrated versus euhydrated conditions. The rate of urine production was greater in HCEH (7.59 + 3.0 mL/min) compared to all other conditions (3.86 + 2.2, 5.29 + 3.1, and 2.96 + 1.1 mL/min for LCDH, LCEH, and HCDH, respectively). Despite CHO and hydration manipulations, no regulatory effects of IL-6 and ADH on plasma [Na(+)] were observed. With euhydration during exercise and additional fluid consumed during recovery, a high-CHO status increased urinary output during recovery, and it decreased the frequency of hyponatremia (Na(+) < 135 mM). Therefore, a high-CHO status may provide some protection against exercise-associated hyponatremia.

timizing fluid management in patients with acute decompensated heart failure (ADHF): the emerging role of combined measurement of body hydration status and brain natriuretic peptide (BNP) levels.

The study tests the hypothesis that in patients admitted with acutely decompensated heart failure (ADHF), achievement of adequate body hydration status with intensive medical therapy, modulated by combined bioelectrical vectorial impedance analysis (BIVA) and B-type natriuretic peptide (BNP) measurement, may contribute to optimize the timing of patient's discharge and to improve clinical outcomes. Three hundred patients admitted for ADHF underwent serial BIVA and BNP measurement. Therapy was titrated to reach a BNP value of 250 pg/ml). Worsening of renal function (WRF) was evaluated during hospitalization. Death and rehospitalization were monitored with a 6-month follow-up. BNP value on discharge of ≤250 pg/ml led to a 25% event rate within 6 months (Group A: 17.4%; Group B: 21%, Chi2; n.s.), whereas a value >250 pg/ml (Group C) was associated with a far higher percentage (37%). At discharge, body hydration was 73.8 ± 3.2% in the total population and 73.2 ± 2.1, 73.5 ± 2.8, 74.1 ± 3.6% in the three groups, respectively. WRF was observed in 22.3% of the total. WRF occurred in 22% in Group A, 32% in Group B, and 20% in Group C (P = n.s.). Our study confirms the hypothesis that combined BNP/BIVA sequential measurements help to achieve adequate fluid balance status in patients with ADHF and can be used to drive a "tailored therapy," allowing clinicians to identify high-risk patients and possibly to reduce the incidence of complications secondary to fluid management strategies.

Spit: Saliva in Nursing Research, Uses and Methodological Considerations in Older Adults.

Over the last 10 years, interest in the analysis of saliva as a biomarker for a variety of systemic diseases or for potential disease has soared. There are numerous advantages to using saliva as a biological fluid, particularly for nurse researchers working with vulnerable populations, such as frail older adults. Most notably, it is noninvasive and easier to collect than serum or urine. The authors describe their experiences with the use of saliva in research with older adults that examined (a) osmolality as an indicator of hydration status and (b) cortisol and behavioral symptoms of dementia. In particular, the authors discuss the timing of data collection along with data analysis and interpretation. For example, it is not enough to detect levels or rely solely on summary statistics; rather it is critical to characterize any rhythmicity inherent in the parameter of interest. Not accounting for rhythmicity in the analysis and interpretation of data can limit the interpretation of associations, thus impeding advances related to the contribution that an altered rhythm may make to individual vulnerability.

Initial hydration status, fluid balance, and psychological affect during recreational exercise in adults.

There is little information on the impact of hydration status on the psychological response to exercise despite potential implications for adherence to an exercise programme and for overall health and fitness. We investigated initial hydration status, fluid balance, and psychological responses associated with a typical recreational exercise session in healthy adults. Fifty-two participants performed a freely chosen gymnasium-based exercise session at a fitness centre, with ad libitum access to fluids. Urine samples were collected on arrival for analysis of osmolality. Sweat loss was estimated from the change in body mass after correction for fluid intake and urinary losses. Subjective psychological ratings were recorded before and after exercise. Pre-exercise urine osmolality was above 900 mOsmol · kg(-1) (used as a threshold for hypohydration) in 37% of participants. Fluid intake during exercise was 390 ± 298 mL, while estimated sweat loss was 794 ± 391 mL. The percentage change from pre-exercise body mass was -0.62 ± 0.20%. Physically active adults who arrived to take part in exercise hypohydrated reported more negative changes in psychological affect in response to their subsequent freely chosen recreational exercise session than those classified as euhydrated prior to exercise (-0.2 ± 0.7 vs. 0.8 ± 0.7; P < 0.005).

Bioelectrical impedance analysis: population references values for phase angle by age and sex

BACKGROUND: Phase angle is an indicator based on reactance and resistance obtained from bioelectrical impedance analysis (BIA). Although its biological meaning is still not clear, phase angle appears to have an important prognostic role. OBJECTIVE: The aim of this study was to estimate population averages and SDs of phase angle that can be used as reference values. DESIGN: BIA and other methods used to evaluate body composition, including hydrodensitometry and total body water, were completed in 1967 healthy adults aged 18-94 y. Phase angle was calculated directly from body resistance and reactance, and fat mass (FM) was estimated from the combination of weight, hydrodensitometry, and total body water by using the 3-compartment Siri equation. Phase angle values were compared across categories of sex, age, body mass index (BMI), and percentage FM. RESULTS: Phase angle was significantly (P < 0.001) smaller in women than in men and was lower with greater age (P < 0.001). Phase angle increased with an increase in BMI and was significantly inversely associated with percentage fat in men. Phase angle was significantly predicted from sex, age, BMI, and percentage FM in multiple regression models. CONCLUSIONS: Phase angle differs across categories of sex, age, BMI, and percentage fat. These reference values can serve as a basis for phase angle evaluations in the clinical setting.

One-year incidence of hyperosmolar states and prognosis in a geriatric acute care unit.

BACKGROUND: Hyperosmolar syndromes are associated with high mortality rates, yet little is known about their incidence and their prognosis. OBJECTIVE: To determine the 1-year incidence of hyperosmolar states and the prognostic factors for in-hospital and 1-year mortality. METHOD: A 6-month prospective cohort study was conducted in a 40-bed acute care geriatric unit and included all patients who developed plasma osmolarity of 320 mosm/l or greater. Age, sex and known cognitive impairment as possible risk factors of hyperosmolarity were assessed. In-hospital and 1-year mortality were calculated and risk factors for death among baseline patient characteristics were sought. RESULTS: 48 (11) of the 436 inpatients in the study were identified as hyperosmolar. Diabetic hyperosmolarity was found in 8 patients. Cognitive impairment was a risk factor for hyperosmolarity (relative risk 2.39, 95% confidence interval 2.18-3.33, p < 0.001), but not age or sex. Infections were accompanied by hyperosmolarity in 30 (62.5). Thirty-five patients (72.9) were bed- or chair-ridden. In-hospital mortality was higher in hyperosmolar patients (35.4) than in the others (16.7%, p = 0.003). Causes of death were infection in 5 (29.4), terminal cachexia in 5, thrombosis in 3, gastric bleeding in 1, renal failure in 2 and heart failure in 1. Functional dependency for mobility was a risk factor for in-hospital mortality but not the degree of hyperosmolarity. One-year mortality was 68.7%. Functional dependency and pressure ulcers were independent predictors of 1-year mortality (p = 0.005 and p = 0.044, respectively). CONCLUSION: Hyperosmolar states occurred in cognitively impaired and dependent patients and resulted in high mortality rates at short and at mid-term. Mortality was related to functional dependency rather than to hyperosmolarity.

Migration of the bioelectrical impedance vector in healthy elderly subjects.

OBJECTIVE: We describe the effects of aging on the bioelectrical impedance vectors in healthy men and women. METHODS: Resistance (R) and reactance (Xc; standard, tetrapolar analysis at 50-kHz frequency) were measured in 201 volunteers (97 men and 104 women) aged 60 to 89 y. Criteria of exclusion from the sample were hospitalization within 3 mo before the survey, current medical treatment, physical handicaps, or other pathologies that might influence the measurements. Stature, weight, and four body circumferences were also measured, and body mass index was calculated. The values of R and Xc were normalized for stature (H) and adjusted for body circumferences by means of covariance analysis. Age- and sex-dependent bioelectrical changes were evaluated by two-factor analysis of variance and Hotelling's T(2) test. RESULTS: The bioelectrical data of the sample agreed well with the normal reference values of the Italian population. R/H showed a significant increase with age in both sexes, whereas Xc/H and the phase angle significantly decreased. The greatest changes occurred in the 70- to 79-y to the 80- to 89-y groups. After adjustment of the bioelectrical values for body circumferences, only Xc/H and the phase angle showed significant differences that decreased with age. CONCLUSIONS: The impedance vectors of healthy individuals showed a clear trend in the elderly, in both sexes, and particularly after age 80 y. The bioelectrical parameters indicated a reduction of soft tissue mass with age, as they tended to approach values typical of pathologically lean subjects (cachetic and anorexic states). After adjustment for the circumferences, the changes in the vector concerned only the Xc component, a measure of the capacitance produced by cell membranes of soft tissues. Therefore, in addition to the quantitative change, the electrical properties of the tissues may also change.

Age-associated alterations in thirst and arginine vasopressin in response to a water or sodium load.

We have examined simultaneous changes in thirst, plasma osmolality and arginine vasopressin, after oral water loading or hypertonic saline infusion. The studies were carried out in the same subjects, comprising young controls aged 26.8 years (SD 4.8, n = 10) and health status-defined elderly people aged 72.1 years (SD 3.1, n = 10). Water loading caused significant falls in plasma osmolality (p < 0.001) and thirst (p < 0.001), but there was no variation with age. Infusion with 462 mmol/l of sodium chloride increased plasma osmolality significantly (p < 0.001), but there was no variation with age (p = 0.12). The perception of thirst during the osmotic loading experiment was recorded differently by the two age groups (p < 0.0001). However, linear regression analysis showed no age difference in the relationship between thirst and plasma osmolality during osmotic loading. During osmotic loading the relationship between the plasma concentration of arginine vasopressin in response to increasing plasma osmolality varied significantly (slope: p = 0.02; intercept: p = 0.02).

Comparison of four bioelectrical impedance analysis formulas in healthy elderly subjects.

BACKGROUND: Changes of body composition occur with aging and influence health status. Thus accurate methods for measuring fat-free mass (FFM) in the elderly are essential. OBJECTIVE: The purpose of this study was to compare FFM obtained by three bioelectrical impedance analysis (BIA) published formulas specific for the elderly and one equation intended for all age groups, with FFM derived from dual-energy X-ray absorptiometry (FFM(DXA)), in healthy elderly subjects. METHODS: Healthy Caucasian subjects over 65 years (106 women, age 75 +/- 6.2, body mass index 25.2 +/- 4.1 and 100 men, age 74.6 +/- 6.6, body mass index 25.8 +/- 3.0) were measured by DXA (Hologic QDR-4500) and BIA (Xitron, 50 kHz). FFM(BIA) was calculated by the published formulas of Deurenberg, Baumgartner, Roubenoff and Kyle and compared to FFM(DXA) by a Bland-Altman analysis. RESULTS: The Deurenberg and Roubenoff BIA formulas underestimated FFM compared to DXA by -7.1 and -2.9 kg in women and -6.7 and -2.3 kg in men, respectively. The Baumgartner formula overestimated FFM by 4.3 kg in women and 1.4 kg in men. The Kyle formula showed differences of 0.0 kg in women and 0.2 kg in men, and the limits of agreement of FFM(BIA (Kyle)) relative to FFM(DXA) were -3.3 and +3.3 kg for women and -3.8 and +4.3 kg for men. CONCLUSION: The Kyle BIA formula accurately predicts FFM in elderly Swiss subjects between 65 and 94 years, with a body mass index of 17 to 34.9 kg/m(2). The other BIA formulas developed especially for the elderly are not valid in this population.

Clinical indicators of dehydration severity in elderly patients.

STUDY OBJECTIVE: To determine which of the signs and symptoms of dehydration obtainable from patient history and physical examination in the emergency department are most useful in assessing the severity of dehydration in elderly patients. DESIGN: Prospective, correlational study. SETTING: Two university teaching hospitals. Patients: Fifty-five patients aged 60 or older presenting to the emergency department with suspected dehydration were studied. MEASUREMENTS AND MAIN RESULTS: In the emergency department, patients were evaluated by a standardized history and physical examination that included assessment of 38 signs and symptoms commonly attributed to dehydration. The relationships between the presence and intensity of these putative dehydration indicators and an independent rating of dehydration severity based on a comprehensive review of the medical record were evaluated. Also evaluated were the relationships between these dehydration indicators and patient age. Indicators that correlated best with dehydration severity but were unrelated to patient age included: tongue dryness (P less than 0.001), longitudinal tongue furrows (P less than 0.001), dryness of the mucous membranes of the mouth (P less than 0.001), upper body muscle weakness (P less than 0.001), confusion (P less than 0.001), speech difficulty (P less than 0.01), and sunkenness of eyes (P less than 0.01). Other indicators had only weak associations with dehydration severity or were also related to age. Patient thirst was unrelated to dehydration severity. CONCLUSIONS: A set of signs and symptoms related to dehydration severity in elderly patients has been identified. These indicators may be more useful for evaluation of dehydration severity in the emergency department than other commonly used indicators.

Evaluation of multi-frequency bio-impedance analysis for the assessment of extracellular and total body water in surgical patients.

1. Multi-frequency bio-impedance analysis has been used to estimate extracellular and total body water in a heterogeneous group of 43 surgical patients (23 males, 20 females). 2. Radioisotope-dilution methods were used for the measurement of extracellular and total body water. 3. Resistance and reactance were measured between wrist and ankle at frequencies from 5 kHz to 1 MHz. 4. Extracellular and total body water were estimated by multiple stepwise regression using the radioisotope values as the dependent variables. The parameters included in the regression were: resistance and reactance at each frequency, body habitus parameters, plasma albumin and plasma sodium. 5. The standard errors of the estimates between the measured and estimated values were 1.73 litres (coefficient of variation 9.6%) and 2.17 litres (coefficient of variation 6.0%) for extracellular and total body water, respectively. 6. These errors represent a useful improvement relative to those obtained from anthropometric estimates. However, the improvements relative to the use of a single frequency (50 kHz) are not clinically significant.

Bioelectrical impedance analysis: a review of principles and applications.

Whole-body bioelectrical impedance analysis (BIA) is widely used by researchers and clinicians as a noninvasive and safe method to estimate body composition and body water volume in children and adults. Development of new approaches, such as segmental and multifrequency analyzers, should greatly expand the utility of this electrical technique. This article reviews the principles, underlying assumptions, clinical applications and future directions of the BIA method.

Bioelectrical impedance analysis: part I. Review of principles and methods.

The use of bioelectrical impedance analysis (BIA) is widespread both in healthy subjects and patients, but suffers from a lack of standardized method and quality control procedures. BIA allows the determination of the fat-free mass (FFM) and total body water (TBW) in subjects without significant fluid and electrolyte abnormalities, when using appropriate population, age or pathology-specific BIA equations and established procedures. Published BIA equations validated against a reference method in a sufficiently large number of subjects are presented and ranked according to the standard error of the estimate. The determination of changes in body cell mass (BCM), extra cellular (ECW) and intra cellular water (ICW) requires further research using a valid model that guarantees that ECW changes do not corrupt the ICW. The use of segmental-BIA, multifrequency BIA, or bioelectrical spectroscopy in altered hydration states also requires further research. ESPEN guidelines for the clinical use of BIA measurements are described in a paper to appear soon in Clinical Nutrition.

Risk factors for dehydration among elderly nursing-home residents.

Dehydration is the most common fluid and electrolyte disorder among the elderly, yet risk factors are not known. This study identifies risk factors for dehydration in acutely ill nursing home residents. All 339 elderly resident of two nursing homes who developed an acute illness requiring hospitalization during 1984 were included in the study. The 173 patients having a serum Na less than 150 mg/dL and blood urea nitrogen to creatinine ratio (BUN:Cre) less than 20 were designated controls; 91 patients having a serum Na greater than 150 mg/dL or a serum BUN:Cre greater than 25 were designated cases. Odds ratios (OR) and confidence intervals were calculated for age, sex, chronic conditions, acute illnesses, medications, functional status measures, and season. Acutely ill dehydrated patients were female (OR, 3.3); over 85 years old (OR, 2.2); had more than four chronic conditions (OR, 4.0); took more than four medications (OR, 2.8); and were bedridden (OR, 2.9). Among the most severely dehydrated (serum Na greater than 150 mg/dL and BUN:Cre greater than 25), the odds ratios for the above factors were strengthened and other factors, such as inability to feed oneself and type of acute diagnosis, emerged as risk factors. Among the variables unrelated to functional status, laxatives (OR, 3.2) and chronic infections (OR, 1.8) were risk factors. We conclude that a group at high risk for dehydration can be defined and that they are better characterized by the number of chronic diseases and debilitated functional status than by acute disease processes.

Is bioelectrical impedance vector analysis of value in the elderly with malnutrition and impaired functionality?

OBJECTIVE: The calculation of body composition using bioelectrical impedance analysis is difficult in the elderly because most equations have been found to be inadequate, especially in the malnourished elderly. We therefore evaluated the use of bioelectrical impedance vector analysis in elderly nursing home residents. METHODS: One hundred twelve nursing home residents were included in the study (34 men, 78 women, age 85.1 y, age range 79.1-91.4 y). Nutritional status was determined by the Mini Nutritional Assessment (MNA), functional status was assessed by handgrip strength, knee extension strength, and Barthel's index, and bioelectrical impedance analysis was performed using Nutriguard M (Data Input, Darmstadt, Germany). RESULTS: Twenty-two nursing home residents were classified as well nourished (MNA I), 80 were considered to be at nutritional risk (MNA II), and 10 were classified as malnourished (MNA III). Handgrip strength, knee extension strength, and Barthel's index were lower in MNA II and MNA III than in MNA I. Phase angle also decreased significantly with the MNA (4.0, 3.8-4.7 degrees; 3.7, 3.3-4.3 degrees; and 2.9, 2.6-3.5 degrees). There was a significant displacement of the mean vector in MNA II and MNA III compared with MNA I. CONCLUSION: The bioelectrical impedance vector analysis resistance/reactance graph could represent a valuable tool to assess changes in body cell mass and hydration status in elderly nursing home residents.

Is bioelectrical impedance vector analysis of value in the elderly with malnutrition and impaired functionality?

OBJECTIVE: The calculation of body composition using bioelectrical impedance analysis is difficult in the elderly because most equations have been found to be inadequate, especially in the malnourished elderly. We therefore evaluated the use of bioelectrical impedance vector analysis in elderly nursing home residents. METHODS: One hundred twelve nursing home residents were included in the study (34 men, 78 women, age 85.1 y, age range 79.1-91.4 y). Nutritional status was determined by the Mini Nutritional Assessment (MNA), functional status was assessed by handgrip strength, knee extension strength, and Barthel's index, and bioelectrical impedance analysis was performed using Nutriguard M (Data Input, Darmstadt, Germany). RESULTS: Twenty-two nursing home residents were classified as well nourished (MNA I), 80 were considered to be at nutritional risk (MNA II), and 10 were classified as malnourished (MNA III). Handgrip strength, knee extension strength, and Barthel's index were lower in MNA II and MNA III than in MNA I. Phase angle also decreased significantly with the MNA (4.0, 3.8-4.7 degrees; 3.7, 3.3-4.3 degrees; and 2.9, 2.6-3.5 degrees). There was a significant displacement of the mean vector in MNA II and MNA III compared with MNA I. CONCLUSION: The bioelectrical impedance vector analysis resistance/reactance graph could represent a valuable tool to assess changes in body cell mass and hydration status in elderly nursing home residents.

Validation of multi-frequency bioelectrical impedance analysis in detecting in fluid balance of geriatric patients.

OBJECTIVES: Multi-Frequency Bioelectrical Impedance Analysis (MFBIA) is a quick, simple, and inexpensive method to assess body fluid compartments. This study aimed at determining the validity of MFBIA in detecting clinically relevant changes of fluid balance in geriatric patients. DESIGN: A prospective, observational study. SETTING: The 22-bed Geriatric Department of the University Hospital Nijmegen. PARTICIPANTS: Hospitalized patients were eligible if they did not have a pacemaker, were not suffering from terminal illnesses, and did not have psychogeriatric diseases likely to interfere with capacity to consent or comply. During a 16-months period, 218 patients were admitted, of whom 78 patients were eligible and 53 consented to participate. MEASUREMENTS: Each subject's fluid balance was diagnosed twice a week as dehydrated, overhydrated, or euvolemic, based on standardized physical examination, laboratory tests, and weight evaluation. Changes in fluid balance were quantified by measuring total body water (TBW) and extracellular fluid (ECF) applying deuterium- and bromide-dilution techniques. Impedance at 1, 5, 50, and 100 kHz and body weight were measured daily. Sensitivity and Guyatt's responsiveness indexes of MFBIA in detecting dehydration and overhydration were determined. RESULTS: In total, 1071 MFBIA measurements were performed, during which 14 transitions from dehydration to euvolemia and 13 transitions from overhydration to euvolemia were monitored. Rehydration of dehydrated patients caused an increase in TBW and ECF of 3.4 +/- 1.8 L and 1.9 +/- 1.9 L, respectively, which resulted in significant decreases in impedance of 133 +/- 67 omega at 1 kHz and 93 +/- 61 omega at 100 kHz (P = .001). Treatment of overhydrated patients caused a TBW and ECF loss of 3.8 +/- 4.2 L and 3.1 +/- 3.8 L, respectively, which resulted in significant increases in impedance of 104 +/- 72 omega at 1 kHz and 81 +/- 68 omega at 100 kHz (P < .001). Sensitivity of a single MFBIA in diagnosing dehydration and overhydration was 14% and 17%, respectively. Responsiveness indexes of weighing and MFBIA for dehydration and overhydration were similar at all frequencies and greater than one. CONCLUSION: The sensitivity of a single impedance measurement in detecting dehydration and overhydration was low. However, responsiveness of serial measurements to intra-individual changes in fluid balance was good. Therefore, this noninvasive technique may be used in clinical practice to improve monitoring fluid balance in geriatric patients, especially when daily weighing is difficult.

Source Study Bioelectrical impedance analysis estimation of water compartments in elderly diseased patients: the source study.

BACKGROUND: This study validates, in geriatric patients, bioelectrical impedance analysis (BIA) equations that had been derived to estimate total body water (TBW) and extracellular water (ECW) in healthy elderly subjects. METHODS: We performed a multicentric trial in six geriatric wards. We studied 169 patients with varying degrees of hydration: dehydrated, euvolemic, and overhydrated. BIA estimates of TBW and of ECW were compared with the measurement of TBW with (18)O dilution and of ECW with bromide (Br) dilution. RESULTS: BIA estimated TBW with a difference of 0.48 +/- 2.3 l (mean +/- SD) (50 kHz; p = .01) and 0.69 +/- 2.2 l (100 kHz; p < 0.001) compared with (18)O dilution. The difference was not affected by the hydration status. Estimates of ECW with BIA were systematically biased compared with Br dilution: 4.6 +/- 3.1 l (equation from Segal and colleagues; p < .001) and 3.4 +/- 2.9 l (equation from Visser and colleagues; p < .001). We propose a new, cross-validated equation. Conclusions. Body water spaces can be estimated accurately in geriatric patients with BIA.

Is bioelectrical impedance analysis a tool at bedside, during heat waves to assist geriatricians with discriminative diagnosis of hypertonic dehydration?

OBJECTIVES: To assess BIA data given by Analycor 3 and some bio-impedance equations to assist geriatricians with discriminative diagnosis of hypertonic dehydration, during heat waves. DESIGN: Prospective study: a dehydrated patients group has been compared with a randomised control group. SETTING: The study was carried out in a French geriatric department, in the Emile Roux geriatric hospital. PARTICIPANTS: 36: six men and twelve women in each group. MEASUREMENTS: The most valuable clinical indicators of dehydration severity were recorded and scored. BIA measurements were performed with an Analycor 3 analyzer; TBW was calculated from impedances at 50 and 100 kHz, ECW from impedance at 5 kHz; Calculations were made also with formula described in the literature, validated in healthy or in institutionalised elderly subjects. RESULTS: TBW and ECW values were always lower in dehydrated group than in control group, but without significance, whatever the applied formula; however ICW values calculated with "manufacturers equations" significantly decreased in dehydrated group. Data given by the analyzer used in this study, as well as BIA age specific equations discriminated the severely hypertonic dehydrated patients sub-group, but not the mildly hypertonic dehydrated patients sub-group. CONCLUSION: The BIA data given by the analyzer used in this study assist geriatricians at bedside with discriminative diagnosis of hypertonic dehydration, especially in severe hypertonic dehydration, but data given by the analyzer used in this study, as well as age specific equations are sometimes in poor agreement with clinical and biological parameters usually selected to assess dehydration, in mildly dehydrated patients.

Body water in the elderly: a review.

Body composition including the amount, the proportion of body weight, and the distribution of body water are of profound interest to both gerontology and geriatric medicine. In this article, methods of estimating body water, the changes with age and in disease, and clinical implications are reviewed. There are many methods to determine body water, the methods having different properties regarding e.g. feasibility and validity. Validation should for the methods used be performed in the population and age group under study. Body water decreases with age, and increases or decreases of body water are common in diseases common in old age. This has obvious clinical implications regarding e.g. geriatric pharmacotherapy, and water and electrolyte therapy. The need for methods to estimate body water and for avoiding both underhydration and overhydration is obvious both in gerontological and geriatric research and in clinical geriatric medicine.

Physician misdiagnosis of dehydration in older adults.

INTRODUCTION: Dehydration is a difficult clinical diagnosis in older adults because the physical signs of dehydration are often confusing. The clinical consequences of a diagnosis of dehydration are critical, since dehydration implies increased morbidity and mortality and aggressive rehydration can improve clinical outcome. The diagnosis is a sentinel event for nursing homes, and often is made at transfer to a hospital. OBJECTIVE: To define the accuracy of the clinical diagnosis of dehydration during hospital admission, and to observe persons admitted from long-term care. METHODS: A total of 102 consecutive medical admissions in persons older than 65 years with a diagnostic coding for dehydration either on admission or during the course of hospitalization over a 3-month period at a university teaching hospital were reviewed. The diagnosis of dehydration was considered confirmed if the calculated serum osmolarity was greater than 295 milliosmols (mOsmol). Subjects were considered to have intravascular volume depletion if the ratio of blood urea nitrogen (BUN) to serum creatinine was greater than 20 or the serum sodium was greater than 145 milligrams per deciliter. Subjects were considered to have hypovolemia if the serum osmolarity was greater than 295 and the BUN/creatinine ratio was greater than 20. RESULTS: Among subjects with a clinical diagnosis of dehydration, only 17% had a serum osmolarity >295 mOsm, and only 11% had a serum sodium greater than 145. A BUN/creatinine ratio greater than 20 was present in 68% of the subjects. Clinicians appear to be using the term dehydration synonymously with intravascular volume depletion. Even so, at least a third of the diagnoses of intravascular volume depletion in older adults were incorrect based on laboratory data. CONCLUSION: Physicians who diagnose dehydration during hospital admission may be relying more on physical signs than laboratory data. Little change in laboratory markers for hydration status occurs from the time of diagnosis to hospital discharge, suggesting that the clinical diagnosis does not affect fluid management. The data suggest a need for improvement in the differential diagnosis and management of volume changes in older persons.

Bioelectrical impedance analysis measurements of total body water and extracellular water in healthy elderly subjects.

OBJECTIVE: To address whether: (1) bioelectrical impedance analysis (BIA) can provide precise and accurate estimates of total body water (TBW) and extracellular water (ECW) in healthy elderly subjects, that display age-induced changes in body composition, (2) BIA models are improved by introducing variables related to geometrical body-shape and osmolarity. DESIGN: Cross-validation of available BIA models and models developed in the study. SUBJECTS: 58 healthy elderly subjects (31 women, 27 men, 66.8+/-4.7 y, mean +/- s.d.) MEASUREMENTS: BIA at 5, 50 and 100 kHz, 18O labelled water measurements of TBW, Br measurements of ECW, anthropometric variables, plasma osmolarity. RESULTS: Published BIA models for estimating TBW, entail various degrees of bias. Precise models (SEE of the models 0.8 L at 100 kHz, 1.0 L at 50 kHz) involving height2/resistance, weight, gender, circumferences and plasma osmolarity were established with data from 30 subjects chosen at random. Cross-validation of an independent group (n = 28) showed no bias (-1.5+/-3.2 L at 100 kHz, -1.4+/-3.2 L at 50 kHz, P = NS). CONCLUSION: We conclude that BIA models with increased accuracy and precision for predicting ECW and TBW can be derived in healthy elderly subjects. Repeated measures had a mean difference of 0.2+/-1.2 L.

Dehydration. Evaluation and management in older adults.

OBJECTIVE: To review published literature regarding dehydration in older individuals and formulate a consensus on the evaluation and treatment of this unrecognized cause of hospitalizations, morbidity, and mortality. DATA SOURCES AND STUDY SELECTION: The literature concerning dehydration in the elderly population from MEDLINE was reviewed from 1976 through 1995. Search terms included dehydration, elderly, evaluation, hospitalization, and treatment. Particular emphasis was placed on articles describing original research leading to the development of new information on the evaluation and treatment of dehydration and review articles relating to the epidemiology, detection, treatment and health outcomes of this syndrome common in the geriatric population, including frail, institutionalized individuals. DATA EXTRACTION: Data contributing to a broad scientific understanding of dehydration were initially grouped according to topic areas of the physiology of normal aging, illness-associated clinical reports of dehydration in the elderly population, and diagnostic and therapeutic interventions. The authors developed a consensus based on the weight of evidence presented and the authors' experience in the field. CONCLUSIONS: Early diagnosis is sometimes difficult because the classical physical signs of dehydration may be absent or misleading in an older patient. Many different etiologies place the elderly at particular risk. In patients identified as being at risk for possible dehydration, an interdisciplinary care plan with regard to prevention of clinically significant dehydration is critical if maximum benefit is to result.

Effects of fluid ingestion on cognitive function after heat stress or exercise-induced dehydration

This study investigated the effects of heat exposure, exercise-induced dehydration and fluid ingestion on cognitive performance. Seven healthy men, unacclimatized to heat, were kept euhydrated or were dehydrated by controlled passive exposure to heat (H, two sessions) or by treadmill exercise (E, two sessions) up to a weight loss of 2.8%. On completion of a 1-h recovery period, the subjects drank a solution containing 50 g l(-1) glucose and 1.34 g l(-1) NaCl in a volume of water corresponding to 100% of his body weight loss induced by dehydration. (H1 and E1) or levels of fluid deficit were maintained (H0, E0). In the E0, H0 and control conditions, the subject drank a solution containing the same quantity of glucose diluted in 100 ml of water. Psychological tests were administered 30 min after the dehydration phase and 2 h after fluid ingestion. Both dehydration conditions impaired cognitive abilities (i.e. perceptive discrimination, short-term memory), as well as subjective estimates of fatigue, without any relevant differences between the methods. By 3.5 h after fluid deficit, dehydration (H0 and E0) no longer had any adverse effect, although the subjects felt increasingly tired. Thus, there was no beneficial effect of fluid ingestion (H1 and E1) on the cognitive variables. However, long-term memory retrieval was impaired in both control and dehydration situations, whereas there was no decrement in performance in the fluid ingestion condition (H1, E1).

Role of dehydration in heat stress-induced variations in mental performance.

Variation in mental performance under different levels of heat stress-induced dehydration was recorded in 11 subjects heat acclimatized to the tropicals. Dehydration was induced by a combination of water restriction and exercise in heat. The psychological functions--arithmetic ability, short-term memory, and visuomotor tracking--were assessed in a thermoneutral room after the subjects recovered fully from the effects of exercise in heat, as reflected by their oral temperature and heart rate. The results indicated significant deterioration in mental functions at 2% or more body dehydration levels.

Role of dehydration in heat stress-induced variations in mental performance.

Variation in mental performance under different levels of heat stress-induced dehydration was recorded in 11 subjects heat acclimatized to the tropicals. Dehydration was induced by a combination of water restriction and exercise in heat. The psychological functions--arithmetic ability, short-term memory, and visuomotor tracking--were assessed in a thermoneutral room after the subjects recovered fully from the effects of exercise in heat, as reflected by their oral temperature and heart rate. The results indicated significant deterioration in mental functions at 2% or more body dehydration levels.

Dehydration impairs vigilance-related attention in male basketball players.

PURPOSE: To determine the effects of dehydration (DEH) on attentional vigilance in male basketball players. METHODS: The Test of Variables of Attention (TOVA; Universal Attention Disorders) was administered to 11 male basketball players (17-28 yr) at baseline (test 1), after walking (50% V O2max) in the heat (40 degrees C and 20% relative humidity) (test 2), and then after a simulated basketball game (test 3). Tests 2 and 3 were performed while subjects were either DEH (1-4%) or euhydrated (EUH). The TOVA consisted of target-infrequent and target-frequent conditions, simulating static and dynamic (such as a basketball game) environments, respectively. TOVA measures included errors of omission (OE) and commission (CE), response time (RT), and sensitivity. RESULTS: During the target-infrequent half of test 3, EUH resulted in significantly better sensitivity (+0.4+/-1.2 vs -0.9+/-1.3), faster RT (-8+/-20 vs +16+/-28), and fewer OE (-0.4+/-0.7 vs +1.3+/-2.4) compared with DEH. During the target-frequent half, EUH resulted in significantly fewer OE (-4+/-15 vs +5+/-7) and CE (-1.9+/-3.2 vs 0.6+/-1.4) in test 2 and greater sensitivity (+0.7+/-2.6 vs -0.7+/-1.1) and faster RT (-21+/-28 vs +5+/-31) than DEH in test 3. CONCLUSION: Vigilance-related attention of male basketball players was impaired by DEH, especially during the target-frequent condition of the TOVA. These results suggest that fluid replacement is essential to prevent the decline in vigilance that occurs with DEH in highly dynamic environments. Therefore, basketball players should be advised to maintain EUH for optimal concentration and attentional skills during competition.

Effects of dehydration and fluid ingestion on cognition.

The effects of exercise-induced dehydration and fluid ingestion on men's cognitive performance were assessed. Eleven young men attended separate sessions in which each individual cycled in a controlled environment at 60 % of V.O (2max) for periods of 15, 60, or 120 min without fluid replacement or 120 min with fluid replacement. Immediately following the assigned submaximal exercise period, the participant completed a graded exercise test to voluntary exhaustion. An executive processing test and a short-term memory test were performed prior to and immediately following exercise. Choice-response times during the executive processing test decreased following exercise, regardless of the level of dehydration. Choice-response errors increased following exercise, but only on trials requiring set shifting. Short-term memory performance improved following exercise, regardless of the level of dehydration. Changes in cognitive performance following exercise are hypothesized to be related to metabolic arousal following strenuous physical activity.

Influence of variations in body hydration on cognitive function: effect of hyperhydration, heat stress, and exercise-induced dehydration.

Submitted 8 healthy, endurance trained men (mean age 27.4 yrs), unacclimated to heat, to variations in body hydration. The Ss were kept euhydrated, dehydrated by controlled passive hyperthermia or exercise on a treadmill up to a weight loss of 2.8%, or hyperhydrated using a solution containing glycerol, with a total ingested volume equal to 21.4 ml/kg of body weight. On completion of a 90-min recovery period, the Ss were assigned a pedaling exercise and psychological tests of perceptive discrimination, psycho-motor skill, memory, fatigue and mood, were administered. Both dehydration conditions impaired cognitive abilities without any relative differences between them. Following arm crank exercise, further effects of dehydration were found for tracking performance only. Moreover, long-term memory was impaired in both control and hydration situations, whereas there was no decrement in performance in the hyperhydration condition.

Effect of water deprivation on cognitive-motor performance in healthy men and women.

Whether mental performance is affected by slowly progressive moderate dehydration induced by water deprivation has not been examined previously. Therefore, objective and subjective cognitive-motor function was examined in 16 volunteers (8 females, 8 males, mean age: 26 yr) twice, once after 24 h of water deprivation and once during normal water intake (randomized cross-over design; 7-day interval). Water deprivation resulted in a 2.6% decrease in body weight. Neither cognitive-motor function estimated by a paced auditory serial addition task, an adaptive 5-choice reaction time test, a manual tracking test, and a Stroop word-color conflict test nor neurophysiological function assessed by auditory event-related potentials P300 (oddball paradigm) differed (P > 0.1) between the water deprivation and the control study. However, subjective ratings of mental performance changed significantly toward increased tiredness (+1.0 points) and reduced alertness (-0.9 points on a 5-point scale; both: P < 0.05), and higher levels of perceived effort (+27 mm) and concentration (+28 mm on a 100-mm scale; both: P < 0.05) necessary for test accomplishment during dehydration. Several reaction time-based responses revealed significant interactions between gender and dehydration, with prolonged reaction time in women but shortened in men after water deprivation (Stroop word-color conflict test, reaction time in women: +26 ms, in men: -36 ms, P < 0.01; paced auditory serial addition task, reaction time in women +58 ms, in men -31 ms, P = 0.05). In conclusion, cognitive-motor function is preserved during water deprivation in young humans up to a moderate dehydration level of 2.6% of body weight. Sexual dimorphism for reaction time-based performance is present. Increased subjective task-related effort suggests that healthy volunteers exhibit cognitive compensating mechanisms for increased tiredness and reduced alertness during slowly progressive moderate dehydration.

Mild dehydration degrades mood and symptoms, not cognitive performance in females: a placebo-controlled study.

Little definitive information is available on the behavioral effects of dehydration. This study assessed effects of mild dehydration on cognitive performance and mood of healthy females, without hyperthermia. Healthy, active women (N=25; mean ± SD age, 23.0 ± 0.6 y; using oral contraceptives) participated in 3 placebo-controlled, randomized, single-blinded, repeated measure trials (9.8 h each) in 3 hydration states: exercise dehydration (D; three 40-min treadmill walks at 5.6 km·h–1, 5% grade, 28°C); D plus diuretic ingestion (D+F; furosemide, 40 mg); and control (CON; exercise, weight maintained by water intake). A comprehensive 6-task cognitive test battery (CTB), Profile of Mood States questionnaire (POMS) and visual analog scales (VAS) were administered. Paired t-tests compared CON (0.12 ± 0.06%) to all D and D+F trials that resulted in ≥1% (1.39 ± 0.30%) body mass loss. Differences (P<.05, CON versus D or D+F) existed at rest and during exercise for POMS (total mood disturbance, tension, vigor, fatigue, confusion) and VAS (task difficulty, concentration, headache). No differences in the CTB were observed. In conclusion, ratings of task difficulty, concentration and headache, as well as mood states were degraded by mild dehydration of 1.39% but cognitive performance was not. Funded by Danone Research, France.

Hydration and cognition: a critical review and recommendations for future research.

The limited literature on the effects of dehydration on human cognitive function is contradictory and inconsistent. Although it has been suggested that decrements in cognitive performance are present in the range of a 2 to 3% reduction in body weight, several dose-response studies indicate dehydration levels of 1% may adversely affect cognitive performance. When a 2% or more reduction in body weight is induced by heat and exercise exposure, decrements in visual-motor tracking, short-term memory and attention are reported, but not all studies find behavioral effects in this range. Future research should be conducted using dose-response designs and state-of-the-art behavioral methods to determine the lowest levels of dehydration that produce substantive effects on cognitive performance and mood. Confounding factors, such as caffeine intake and the methods used to produce dehydration, need to be considered in the design and conduct of such studies. Inclusion of a positive control condition, such as alcohol intake, a hypnotic drug, or other treatments known to produce adverse changes in cognitive performance should be included in such studies. To the extent possible, efforts to blind both volunteers and investigators should be an important consideration in study design.

Effects of caffeine, sleep loss, and stress on cognitive performance and mood during U.S. Navy SEAL training.

RATIONALE: When humans are acutely exposed to multiple stressors, cognitive performance is substantially degraded. Few practical strategies are available to sustain performance under such conditions. OBJECTIVE: This study examined whether moderate doses of caffeine would reduce adverse effects of sleep deprivation and exposure to severe environmental and operational stress on cognitive performance. METHODS: Volunteers were 68 U.S. Navy Sea-Air-Land (SEAL) trainees, randomly assigned to receive either 100, 200, or 300 mg caffeine or placebo in capsule form after 72 h of sleep deprivation and continuous exposure to other stressors. Cognitive tests administered included scanning visual vigilance, four-choice visual reaction time, a matching-to-sample working memory task and a repeated acquisition test of motor learning and memory. Mood state, marksmanship, and saliva caffeine were also assessed. Testing was conducted 1 and 8 h after treatment. RESULTS: Sleep deprivation and environmental stress adversely affected performance and mood. Caffeine, in a dose-dependent manner, mitigated many adverse effects of exposure to multiple stressors. Caffeine (200 and 300 mg) significantly improved visual vigilance, choice reaction time, repeated acquisition, self-reported fatigue and sleepiness with the greatest effects on tests of vigilance, reaction time, and alertness. Marksmanship, a task that requires fine motor coordination and steadiness, was not affected by caffeine. The greatest effects of caffeine were present 1 h post-administration, but significant effects persisted for 8 h. CONCLUSIONS: Even in the most adverse circumstances, moderate doses of caffeine can improve cognitive function, including vigilance, learning, memory, and mood state. When cognitive performance is critical and must be maintained during exposure to severe stress, administration of caffeine may provide a significant advantage. A dose of 200 mg appears to be optimal under such conditions. FREE FULL TEXT IN PUBMED

Severe decrements in cognition function and mood induced by sleep-loss, heat, dehydration and undernutrition during simulated combat.

BACKGROUND: Military exercises generate high levels of stress to simulate combat, providing a unique opportunity to examine cognitive and physiologic responses of normal humans to acute stress. METHODS: Cognitive and physiologic markers of stress were evaluated before, during, and after an intense training exercise conducted for 53 hours in the heat. Cognitive performance, mood, physical activity, sleep, body composition, hydration, and saliva cortisol, testosterone, and melatonin were assessed. Volunteers were 31 male U.S. Army officers from an elite unit, aged 31.6 +/- .4 years. RESULTS: Wrist activity monitors documented that soldiers slept only 3.0 +/- .3 hours during the exercise and were active throughout. Volunteers lost 4.1 +/- .2 kg (p < .001) of weight, predominately water (3.1 +/- .3 L) (p < .001). Substantial degradation in cognitive function, assessed with computerized tests, occurred. Vigilance, reaction time, attention, memory, and reasoning were impaired (p < .001). Mood, including vigor (p < .001), fatigue (p < .001), confusion (p < .001), depression (p < .001), and tension (p < .002), assessed by questionnaire, deteriorated. The highest cortisol and testosterone levels were observed before the exercise. CONCLUSIONS: This study quantifies the overwhelmingly adverse impact of multiple stressors on cognitive performance, mood, and physiologic parameters, during a continuous but brief military exercise conducted by highly motivated, well-trained officers.

The effects of fluid restriction on hydration status and subjective feelings in man.

Hydration status and the effects of hypohydration have been the topic of much public and scientific debate in recent years. While many physiological responses to hypohydration have been studied extensively, the subjective responses to hypohydration have largely been ignored. The present investigation was designed to investigate the physiological responses and subjective feelings resulting from 13, 24 and 37 h of fluid restriction (FR) and to compare these with a euhydration (EU) trial of the same duration in fifteen healthy volunteers. The volunteers were nine men and six women of mean age 30 (sd 12) years and body mass 71.5 (sd 13.4) kg. Urine and blood samples were collected and subjective feelings recorded on a 100 mm verbally anchored questionnaire at intervals throughout the investigation. In the EU trial the subjects maintained their normal diet. Body mass decreased by 2.7 (sd 0.6) % at 37 h in the FR trial and did not change significantly in the EU trial. Food intake in the FR trial (n 10) provided an estimated water intake of 487 (sd 335) ml and urinary losses (n 15) amounted to 1.37 (sd 0.39) litres. This is in comparison with an estimated water intake of 3168 (sd 1167) ml and a urinary loss of 2.76 (sd 1.11) litres in the EU trial. Plasma osmolality and angiotensin II concentrations increased from 0-37 h with FR. Plasma volume decreased linearly throughout the FR trial amounting to a 6.2 (sd 5.1) % reduction by 37 h. Thirst increased from 0-13 h of FR then did not increase further (P>0.05). The subjects reported feelings of headache during the FR trial and also that their ability to concentrate and their alertness were reduced.

Brain serotonin metabolism during water deprivation and hydration in rats.

The effects of two-day water deprivation and hyperhydration (provision of 4% sucrose solution for 48 h) on levels of serotonin and its major metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the midbrain and hypothalamus were studied in Wistar rats. The rates of diuresis (0.05 +/- 0.01 and 0.84 +/- 0.12 ml/h/100 g in water deprivation and hyperhydration respectively) and urine osmolality (1896 +/- 182 and 50 +/- 13 mOsm/kg) reflected increases and decreases in blood vasopressin levels. Water deprivation was associated with a significant increase in 5-HIAA levels in the midbrain and hypothalamus, along with a decrease in serotonin levels and a three-fold increase in serotonin catabolism (the 5-HIAA:serotonin concentration ratio). Hyperhydration induced moderate increases in serotonin and 5-HIAA levels in the hypothalamus with no changes in the midbrain. The blood corticosterone level doubled in water deprivation and decreased in hyperhydration. It is suggested that activation of the serotoninergic system induces a complex adaptive reaction in water deprivation. including mechanisms specific for the regulation of water-electrolyte homeostasis and non-specific stress mechanisms (vasopressin and corticoliberin secretion).

Severe decrements in cognition function and mood induced by sleep-loss, heat, dehydration and undernutrition during simulated combat.

BACKGROUND: Military exercises generate high levels of stress to simulate combat, providing a unique opportunity to examine cognitive and physiologic responses of normal humans to acute stress. METHODS: Cognitive and physiologic markers of stress were evaluated before, during, and after an intense training exercise conducted for 53 hours in the heat. Cognitive performance, mood, physical activity, sleep, body composition, hydration, and saliva cortisol, testosterone, and melatonin were assessed. Volunteers were 31 male U.S. Army officers from an elite unit, aged 31.6 +/- .4 years. RESULTS: Wrist activity monitors documented that soldiers slept only 3.0 +/- .3 hours during the exercise and were active throughout. Volunteers lost 4.1 +/- .2 kg (p < .001) of weight, predominately water (3.1 +/- .3 L) (p < .001). Substantial degradation in cognitive function, assessed with computerized tests, occurred. Vigilance, reaction time, attention, memory, and reasoning were impaired (p < .001). Mood, including vigor (p < .001), fatigue (p < .001), confusion (p < .001), depression (p < .001), and tension (p < .002), assessed by questionnaire, deteriorated. The highest cortisol and testosterone levels were observed before the exercise. CONCLUSIONS: This study quantifies the overwhelmingly adverse impact of multiple stressors on cognitive performance, mood, and physiologic parameters, during a continuous but brief military exercise conducted by highly motivated, well-trained officers.

Voluntary dehydration and cognitive performance in trained college athletes.

Cognitive and mood decrements resulting from mild dehydration and glucose consumption were studied. Men and women (total N = 54; M age = 19.8 yr., SD = 1.2) were recruited from college athletic teams. Euhydration or dehydration was achieved by athletes completing team practices with or without water replacement. Dehydration was associated with higher thirst and negative mood ratings as well as better Digit Span performance. Participants showed better Vigilance Attention with euhydration. Hydration status and athlete's sex interacted with performance on Choice Reaction Time and Vigilance Attention. In a second study, half of the athletes received glucose prior to cognitive testing. Results for negative mood and thirst ratings were similar, but for cognitive performance the results were mixed. Effects of glucose on cognition were independent of dehydration.

Dehydration-induced synaptic plasticity in magnocellular neurons of the hypothalamic supraoptic nucleus.

Norepinephrine plays a critical role in the regulation of hypothalamic neuroendocrine function, in large part through modulation of synaptic glutamate and gamma-aminobutyric acid (GABA) release. Hypothalamic magnocellular neuroendocrine cells undergo dramatic changes in synaptic organization under conditions of increased hormone release, including increased numbers of glutamatergic, GABAergic and noradrenergic synapses. We studied the functional plasticity of magnocellular neurons of the rat supraoptic nucleus induced by chronic dehydration using whole-cell recordings in hypothalamic slices. Dehydrated rats showed increases in glutamate and GABA release onto magnocellular neurons, as evidenced by an increase in the frequency of spontaneous excitatory (29%) and inhibitory (33%) postsynaptic currents. The change in glutamate release was likely due to increased numbers of release sites because paired-pulse facilitation analysis did not reveal a change in the probability of transmitter release. In untreated rats, norepinephrine facilitates glutamate release and attenuates GABA release onto magnocellular neurons. Dehydration resulted in a marked enhancement of norepinephrine's actions, doubling both the norepinephrine-induced increase in glutamate release and decrease in GABA release. The norepinephrine dose-response curve was shifted to the left with dehydration, revealing an increase in norepinephrine sensitivity. Thus, dehydration leads to an increase in glutamate and GABA release onto supraoptic magnocellular neurons as well as a marked enhancement of the facilitatory effect of norepinephrine on glutamate release and inhibitory effect on GABA release. This synaptic plasticity would be expected to increase the excitability of the magnocellular neurons and support the enhanced bursting capacity and facilitated hormone secretion observed in vivo with chronic dehydration. FREE FULL TEXT AVAILABLE IN PUBMED

Mild dehydration impairs cognitive performance and mood of men

The present study assessed the effects of mild dehydration on cognitive performance and mood of young males. A total of twenty-six men (age 20·0 (sd 0·3) years) participated in three randomised, single-blind, repeated-measures trials: exercise-induced dehydration plus a diuretic (DD; 40 mg furosemide); exercise-induced dehydration plus placebo containing no diuretic (DN); exercise while maintaining euhydration plus placebo (EU; control condition). Each trial included three 40 min treadmill walks at 5·6 km/h, 5 % grade in a 27·7°C environment. A comprehensive computerised six-task cognitive test battery, the profile of mood states questionnaire and the symptom questionnaire (headache, concentration and task difficulty) were administered during each trial. Paired t tests compared the DD and DN trials resulting in >1 % body mass loss (mean 1·59 (sd 0·42) %) with the volunteer's EU trial (0·01 (sd 0·03) %). Dehydration degraded specific aspects of cognitive performance: errors increased on visual vigilance (P = 0·048) and visual working memory response latency slowed (P = 0·021). Fatigue and tension/anxiety increased due to dehydration at rest (P = 0·040 and 0·029) and fatigue during exercise (P = 0·026). Plasma osmolality increased due to dehydration (P < 0·001) but resting gastrointestinal temperature was not altered (P = 0·238). In conclusion, mild dehydration without hyperthermia in men induced adverse changes in vigilance and working memory, and increased tension/anxiety and fatigue.
 
 

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