Showing papers on "Body water published in 1998"

Urinary indices during dehydration, exercise, and rehydration

Abstract: This investigation evaluated the validity and sensitivity of urine color (Ucol), specific gravity (Usg), and osmolality (Uosm) as indices of hydration status, by comparing them to changes in body water. Nine highly trained males underwent a 42-hr protocol involving dehydration to 3.7% of body mass (Day 1, -2.64 kg), cycling to exhaustion (Day 2, -5.2% of body mass, -3.68 kg), and oral rehydration for 21 hr. The ranges of mean (across time) blood and urine values were Ucol, 1-7; Usg, 1.004-1.029; Uosm, 117-1,081 mOsm x kg-1; and plasma osmolality (Posm), 280-298 mOsm x kg-1. Urine color tracked changes in body water as effectively as (or better than) Uosm, Usg, urine volume, Posm, plasma sodium, and plasma total protein. We concluded that (a) Ucol, Uosm, and Usg are valid indices of hydration status, and (b) marked dehydration, exercise, and rehydration had little effect on the validity and sensitivity of these indices.

Sequential changes in the metabolic response in severely septic patients during the first 23 days after the onset of peritonitis

Abstract: OBJECTIVE: To quantify the sequential changes in metabolic response occurring in patients with severe sepsis after the onset of peritonitis. SUMMARY BACKGROUND DATA: Understanding the changes in energy expenditure and body composition is essential for the optimal management of severely septic patients; however, they have not been quantified in the context of modern surgical care. METHODS: Twelve patients with severe sepsis secondary to peritonitis (median APACHE II score = 21.5) had measurements of energy expenditure and body composition as soon as they were hemodynamically stable and 5, 10, and 21 days later. Sequential measurements of acute-phase proteins and cytokine responses were also made. RESULTS: Resting energy expenditure rose to 49% above predicted and remained elevated throughout the study period. Total energy expenditure was 1.25 x resting energy expenditure. Body fat was oxidized when energy intake was insufficient to achieve energy balance. There was a positive fluid balance of 12.5 1 over the first 2 days after onset of sepsis; thereafter, body water changes closely paralleled body weight changes and were largely accounted for by changes in extracellular water. During the 21 -day study period, there was a loss of 1.21 kg (13%) of total body protein. During the first 10 days, 67% of the protein lost came from skeletal muscle, but after this time it was predominantly from viscera. Intracellular potassium levels were low but did not deteriorate further after hemodynamic stability had been reached. There was a reprioritization of hepatic protein synthesis that was obligatory and independent of changes in total body protein. The cytokine responses demonstrated the complexity, redundancy, and overlap of mediators. CONCLUSIONS: The period of hypermetabolism in severely septic patients is similar to that previously described, but the fluid changes are larger and the protein loss is greater. Protein loss early on is predominantly from muscle, thereafter from viscera. Fat loss can be prevented and cell function preserved once hemodynamic stability is achieved.

Six-compartment body composition model: inter-method comparisons of total body fat measurement.

Abstract: OBJECTIVE: To compare 16 currently used total body fat methods to a six-compartment criterion model based on in vivo neutron activation analysis. DESIGN: Observational, inter-method comparison study. SUBJECTS: Twenty-three healthy subjects (17 male and 6 female). MEASUREMENTS: Total body water (TBW) was measured by tritium dilution; body volume by underwater weighing (UWW); total body fat and bone mineral by dual-energy X-ray absorptiometry (DXA), total body potassium (TBK) by whole-body 40K counting; total body carbon, nitrogen, calcium, phosphorus, sodium and chlorine by in vivo neutron activation analysis; skinfolds/circumferences by anthropometry (Anth); and resistance by single-frequency bioimpedance analysis (BIA). RESULTS: The average of total body fat mass measurements by the six-compartment neutron activation model was 19.7±10.2 kg (mean±s.d.) and comparable estimates by other methods ranged from 17.4–24.3 kg. Although all 16 methods were highly correlated with the six-compartment criterion model, three groups emerged based on their comparative characteristics (technical error, coefficient of reliability, Bland-Altman analysis) relative to criterion fat estimates, in decreasing order of agreement: 1. multi-compartment model methods of Baumgartner (19.5±9.9 kg), Heymsfield (19.6±9.9 kg), Selinger (19.7±10.2 kg) and Siri-3C (19.6±9.9 kg); 2. DXA (20.0±10.8 kg), Pace-TBW (18.8±10.1 kg), Siri-2C (20.0±9.9 kg), and Brozek-UWW (19.4±9.2 kg) methods; and 3. Segal-BIA (17.4±7.2 kg), Forbes-TBN (21.8±10.5 kg), Durnin-Anth (22.1±9.5 kg), Forbes-TBK (22.9±11.9 kg), and Steinkamp-Anth (24.3±9.5 kg) methods. CONCLUSION: Relative to criterion fat estimates, body composition methods can be organized into three groups based on inter-method comparisons including technical error, coefficient of reliability and Bland-Altman analysis. These initial groupings may prove useful in establishing the clinical and research role of the many available fat estimation methods.

Comparisons of two-, three-, and four-compartment models of body composition analysis in men and women

Abstract: This study compared the traditional two-compartment (fat mass or FM; fat free mass or FFM) hydrodensitometric method of body composition measurement, which is based on body density, with three (FM,...

Analytic assessment of the various bioimpedance methods used to estimate body water

Abstract: Knowledge of patient fluid distribution would be useful clinically. Both single-frequency (SF) and impedance modeling approaches are proposed. The high intercorrelation between body water compartments makes determining the best approach difficult. This study was conducted to evaluate the merits of an SF approach. Mathematical simulation was performed to determine the effect of tissue change on resistance and reactance. Dilution results were reanalyzed, and resistance and parallel reactance were used to predict the intracellular water for two groups. Results indicated that the amount of intracellular and extracellular water conduction at any SF can vary with tissue change, and reactance at any SF is affected by all tissue parameters. Modeling provided a good prediction of dilution intracellular and extracellular water, but an SF method did not. Intracellular, extracellular, and total body water were equally predicted at all frequencies by SF resistance and parallel reactance. Extracellular and intracellular water are best measured through modeling, because only at the zero and infinite frequencies are the results sensitive only to extracellular and intracellular water. At all other frequencies there are other effects.

Discriminating between body fat and fluid changes in the obese adult using bioimpedance vector analysis

Abstract: OBJECTIVE: Conventional body composition methods may produce biased quantification of fat and fat-free mass in obese subjects, due to possible violation of the assumption of constant (73%) tissue hydration. We used an assumption-free, graphical method for interpreting body weight variation in obesity using bioelectrical measurements. DESIGN: 540 obese subjects with body mass index (BMI) >31 kg/m2 without apparent edema were compared to 726 healthy subjects with BMI <31 kg/m2 and to 50 renal patients with apparent edema. A subgroup of 48 obese subjects were evaluated again after weight loss (8.6 kg, 3 BMI units) following one-month energy restriction (5 MJ/d, 1200 kcal/d). 32 obese uremic patients were evaluated before and after a dialysis session (3.2 kg fluid removed). Direct measurements obtained from standard 50 kHz frequency bioelectrical impedance analyzer were used as impedance vectors in the Resistance-Reactance Graph. RESULTS: 1) Impedance vectors of obese subjects could be discriminated from those of edematous patients with 91% correct allocation; 2) A significant lengthening of vectors was observed after fluid loss of 3 kg in obese subjects; but 3) A body weight loss of about 9 kg after energy restriction was associated with no vector displacement. CONCLUSION: A different impedance vector pattern was associated with body weight loss in obesity due to fluid removal (vector lengthening) versus an energy-restricted diet (no vector displacement).

Human hydrometry: comparison of multifrequency bioelectrical impedance with2H2O and bromine dilution

Abstract: The traditional method of assessing total body water (TBW), extracellular water (ECW), and intracellular water (ICW) has been the use of isotopes, on the basis of the dilution principle. Although t...

Energy and water metabolism, body composition, and hormonal changes induced by 42 days of enforced inactivity and simulated weightlessness.

Abstract: Inactivity causes profound deleterious changes. We investigated in eight healthy men the impact of a 42-day head-down bed rest (HDBR) on energy and water metabolism and their interrelationships with body composition (BC) and catabolic and anabolic hormones. Total energy expenditure (TEE), total body water, water turnover, and metabolic water formation were assessed by the doubly labeled water method 15 days before and for the last 15 days of HDBR. Resting energy expenditure was determined by indirect calorimetry, and BC was determined by dual energy x-ray absorptiometry. Urinary excretion of cortisol, GH, normetanephrine, metanephrine, urea, and creatinine were measured daily. HDBR resulted in significant reductions in body weight (2%), total body water (5%), metabolic water (17%), and lean body mass (LBM; 4%), but fat mass and water turnover did not change. Segmental BC showed a decreased LBM in legs and trunk, whereas fat mass increased, no significant changes were noted in the arms. The hydration of LBM was unchanged. TEE and energy intake decreased significantly (20% and 13%), whereas resting energy expenditure was maintained. Expenditure for physical activity dropped by 39%. Subjects were in energy balance during HDBR, whereas it was negative during the control period (-1.5 MJ/day). There were decreases in urinary normetanephrine (23%) and metanephrine (23%), but urinary cortisol (28%; weeks 2 and 3), GH (75%; weeks 2-4), and urea (15%; weeks 3 and 4) increased. It was concluded that during prolonged HDBR no relevant modifications in water metabolism were triggered. BC changes occurred in the nonexercised body segments, and the reduction in TEE was due to inactivity, not to LBM loss. Moreover, body weight alone does not accurately reflect the subject's energy state, and energy balance alone could not explain the body weight loss, which involves a transient metabolic stress.

Extracellular fluid volume determined by bioelectric impedance and serum albumin in CAPD patients.

Abstract: Aim. To investigate the relationship between serum albumin and extracellular fluid volume, as measured by multifrequency bioelectrical impedance, in stable patients treated by CAPD. Method. Fifty-nine stable CAPD patients were assessed. Serum albumin (bromocresol green) and CRP, age, dialysate to plasma (D/P) creatinine ratio, normalized protein catabolic rate (nPCR), daily urine and peritoneal protein losses, and extracellular fluid volume (Vecf) were measured in each patient. Vecf was calculated as a percentage of actual body weight (Vecf% ABW ), of lean body mass derived from anthropometry (Vecf% LBM ) and of total body water ( Vecf% Vtbw). Comparisons between those with a normal serum albumin (≥37 g/l) and those with a low serum ajbumin (<37 g/l) were made by Mann-Whitney U test. Correlations with serum albumin were sought by Pearson's test. Results. The D/P creatinine ratio, daily peritoneal and urine protein losses, and extracellular fluid volume (Vecf% LBM and Vecf% Vtbw) were all significantly greater in patients with serum albumin <37 g/1 as compared to those ≥37 g/l; P< 0.05. Age, CRP, and nPCR were not different. Serum albumin was negatively correlated with Vecf% LBM, r = - 0.25; P= 0.05, Vecf% Vtbw, r= -0.39; P=0.002, and daily urinary albumin loss, r= -0.25, P=0.06. Conclusion. Hypoalbuminaemia is partly dependent on subclinical overhydration in CAPD patients. Serum albumin is negatively correlated with increased extracellular fluid volume and the proportion of Vecf to Vtbw is increased in hypoalbuminaemic patients. Multifrequency bioelectrical impedance is able to identify these abnormalities.

Body fluids monitor

Abstract: Method and apparatus are described for determining volumes of body fluids in a subject using bioelectrical response spectroscopy. The human body is represented using an electrical circuit. Intra-cellular water is represented by a resistor in series with a capacitor; extra-cellular water is represented by a resistor in series with two parallel inductors. The parallel inductors represent the resistance due to vascular fluids. An alternating, low amperage, multi-frequency signal is applied to determine a subject's impedance and resistance. From these data, statistical regression is used to determine a 1% impedance where the subject's impedance changes by no more than 1% over a 25 kHz interval. Circuit components of the human body circuit are determined based on the 1% impedance. Equations for calculating total body water, extra-cellular water, total blood volume, and plasma volume are developed based on the circuit components.

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

Abstract: 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.

Body composition changes in anorexia nervosa.

Abstract: Objective: To assess the body composition changes in anorexia nervosa and after medium term recovery. Design: A descriptive study. Setting: Rome, Italy. Subjects: Twenty women affected by anorexia nervosa (AN) with a BMI [weight (kg)/height (m)] below 17 kg/m and weight-stable for at least three months, were compared with 10 well nourished control women (CO) and nine rehabilitated subjects (R-AN), who had a BMI above 18.5 kg/m stable for at least the last six months. Interventions: Body fat was assessed by underwater weighing, muscle mass by urinary creatinine, total body water (TBW) by impedance parameters (50 kHz and 800 μA), skeletal mass by anthropometry and radius bone mineral density by dual photon absorptiometry in ultra-distal (UD-BMD) and medio-distal (MD-BMD) sites. Results: The AN group, as compared to the control group, had a significantly lower weight, body mass index (BMI kg/m) and percent body fat (P<0.0000). Creatinine urinary excretion was lowest in absolute term and when expressed as creatinine height index or per kg fat free mass (FFM) (P<0.0000); muscle mass per kg body weight was 13% lower (P<0.01). Ultra distal bone mineral density (UD-BMD) was 6% lower (not significant). TBW as percent of body weight was significant higher (P<0.001): however TBW/FFM % was not statistically different with large inter-individual variability. An altered distribution of extra and intra-cellular water was suggested by the phase angle (AN: 4.4±0.8°; CO: 6.1±0.4°; (P<0.0000). In rehabilitated anorexic patients (R-AN) the fat mass represented 53% of the weight gain. Their creatinine excretion remained still below the mean value of the controls (P<0.001). The impedance parameters were not significantly different between the R-AN and the CO groups, however, the phase angle of the R-AN (5.0±0.7°) remained lower than in the CO group, indicating that the water distribution was still altered. Conclusions: This study shows that AN is a condition of reduced body fat as well as of muscle mass, with a slightly reduced bone mass. In the course of rehabilitation, most of the weight regained is represented by fat, while the muscle mass appears to lag behind, at least in the medium term. Sponsorship: National Research Council (CNR), Italy, Target Project ‘Prevention and Control Disease Factors’ Subproject ‘Nutrition’ no. 94.00686 PF 41.

Assessment of foot-to-foot bioelectrical impedance analysis for the prediction of total body water

Abstract: Objective: To investigate the accuracy of foot-to-foot impedance methodology for the prediction of total body water and whether leg length rather than stature should be used in the prediction of total body water. Design: Cross-sectional study using volunteers from the community. Setting: University laboratory. Subjects: 57 subjects (29 male; 28 female) aged 19‐56 y. Interventions: Total body water was measured using a deuterium oxide dilution technique. Total body water was also predicted using foot-to-foot impedance apparatus (Tanita Inc, Tokyo, Japan, Model TBF 305). Results: Mean values for predicted and measured total body water differed by 0.7 l. However this bias was not constant across all individuals with a progressive underestimation of total body water by foot-to-foot impedance technology as the water content of the body increases. Also the use of leg length did not improve the accuracy of the prediction equation. Conclusions: At the population level predictions of total body water obtained from foot-to-foot impedance technology compare well with measured total body water. However the significant correlation between the difference between predicted and measured total body water and the absolute value for total body water is a concern especially if the technology is used for body composition assessment during a weight loss program. Sponsorship: RJH was in receipt of a Queensland University of Technology Vacation Scholarship. Descriptors: bioelectrical impedance; total body water; body composition

Bioelectrical impedance analysis predicts outcome in patients with suspected bacteremia

Abstract: Fluid shifts from intracellular to extracellular water (ICW to ECW) are a feature of sepsis, caused by increased vascular permeability and cell catabolism. Changes in ECW and total body water (TBW) were assessed in a prospective observational study of patients with bacteremia by a bedside technique, and its prognostic impact determined. In 78 hospital patients with fever, the resistance ratio (Rinf/RO) and estimated ECW/TBW ratio from multifrequency bioelectrical impedance analysis, and serum albumin concentration were measured. Rinf/RO and ECW/TBW ratios decreased from day 0 to 2 in patients with significant bacteremia (n=31), but not in patients with doubtful or negative blood cultures (n=22 and 25). Increased Rinf/RO at baseline, and further increase of ECW/TBW from day 0 to 2, were associated with lower rate of recovery after 1 week and with higher mortality. Baseline Rinf/RO above the media (0.75) had positive and negative predictive values of 0.31 and 0.95 for death. This prognostic effect was independent of underlying disease and blood culture result in a multivariate model. Hypoalbuminemia at baseline was predictive of outcome, but changes in albumin from day 0 to 2 were unrelated to blood culture results or outcome. In patients with bacteremia, fluid shifts from intracellular to extracellular water occur early, are rapidly reversible by antibiotic treatment but are associated with adverse prognosis. Bioelectrical impedance deserves further study as a tool for bedside monitoring of patients with bacteremia.

Effect of growth hormone on height, weight, and body composition in Prader-Willi syndrome

Abstract: AIMS—To evaluate the effect of the administration of growth hormone on stature, body weight, and body composition in children aged between 4 and 10 years with Prader-Willi syndrome. METHODS—Height, weight, and skinfold thickness were recorded in 25 children using standard anthropometric techniques at recruitment, and six months later, shortly before the start of daily subcutaneous injections of growth hormone. Body composition was assessed via a measurement of total body water using stable isotopes. Measurements were repeated at the end of the six months of growth hormone administration. Measurements of height, weight, and skinfold thickness were expressed as standard deviation scores (SDSs). RESULTS—There was a significant reduction in the percentage of body fat after growth hormone treatment; height velocity doubled during treatment; body weight did not change significantly when expressed as an SDS. Skinfold thickness at both the triceps and subscapular site decreased in absolute terms and when expressed as an SDS. CONCLUSIONS—These results indicate sufficient potential benefit to justify a more prolonged trial of growth hormone treatment and an exploration of different dosage regimens in children with Prader-Willi syndrome.

Plasma volume expansion with oral fluids in hypohydrated men at rest and during exercise.

Abstract: Background: The purpose for this study was to evaluate various carbohydrate (CHO)-electrolyte fluid formulations for consumption by astronauts to maintain or restore their plasma volume (PV) and total body water (TBW) during and after extravehicular activity (exercise experiment, EE) and for a few hours before reentry and immediately after landing (rest experiment RE). Hypothesis: That fluid formulation electrolyte content would be more important than osmotic (Osm) content for increasing or maintaining PV during the RE and EE. Methods: In the RE, 5 healthy men (23-44 yr), previously dehydrated for 24 h, drank 6 fluid formulations (Water, 19.6 Na, 157 Na, 19.6 Na + glucose, and the prepared drinks Performance® and Power)-one each at weekly intervals, and then sat for 70 min. In the EE, four healthy 24-h dehydrated men (30-46 yr) exercised for 70 min supine on a cycle ergometer (load = 71 ± 1% peak VO 2 ). Results: Rest: Subjects who consumed formulations with total Osm concentrations nearer the normal range (157 Na - 270 mOsm . kg -1 , Performance® with 19.6 mEq . L -1 Na - 380 mOsm, and to some extent Power with 23.5 mEq . L -1 Na - 390 mOsm) had the greater increases in PV; intake of drink 157 Na, with the largest Na content, induced the greatest hypervolemia of 7.6% (p < 0.05). The various additional ions, in addition to 19.6 Na, probably contributed to the 4.6% (p < 0.05) hypervolemia with Performance®. Water was not effective. Exercise: Stabilization of PV between 15-70 min was not related to drink total CHO, Na or Osm content. Performance® and 157 Na were no more effective than 19.6 Na or 19.6 Na + glu for PV stabilization. Water was the least effective. Regulatory mechanisms controlling PV during exercise appear to be independent of oral fluid formulation Osm-electrolyte content. Conclusions: Drink cation (sodium) content is more important that its total osmotic content for increasing plasma volume at rest. Fluid formulations with greater hypervolemic action in resting subjects may not be as effective during exercise; therefore different formulations for use during exercise appear to be necessary.

Body composition in patients treated with peritoneal dialysis.

Abstract: Introduction Background. Malnutrition is a common complication in uremia and during maintenance dialysis. Several Malnutrition is a common complication in uremia and factors contribute to its development. DiVerent modes during maintenance dialysis [1‐3] which is associated of dialysis treatment may diVer in their eVects on with increased morbidity and mortality [4‐7]. Several nutritional status. factors contribute to the protein-energy malnutrition Methods. In order to analyse the nutritional con- in dialysis patients and various dialysis modalities may sequences of peritoneal dialysis (PD), body composi- diVer in their eVect on nutritional status [8]. tion analyses were performed in PD patients between Peritoneal dialysis (PD) may oVer potential nutriFebruary 1993 and March 1996. Body cell mass (BCM ) tional advantages compared with hemodialysis in that was estimated from measurements of total body potas- it provides a continuous energy supply, which may sium ( TBK ) in a whole-body counter. Total body have a protein-sparing eVect. In addition, the catabolic water ( TBW ) was determined by measurement of stimuli of hemodialysis, e.g. blood‐membrane intertritiated water. Body fat (BF ) was calculated from actions, are avoided. Protein losses in the peritoneal body weight (BW ), TBK and TBW. Observed values dialysate appear to be of the same magnitude as in were related to predicted (o/p) derived from local various hemodialysis modalities. However, increased population studies. abdominal filling and discomfort combined with supResults. Sixty patients were repeatedly investigated pressed appetite as a consequence of glucose uptake during the study period. Of these, 34 were investigated are factors that may negatively influence nutritional during the first year of PD. At the start of dialysis, status in PD patients [9]. TBK o/p was 0.94 and BF o/p 0.76. No change in The risk of malnutrition in PD is supported by the body composition was seen during the observation cross-sectional study of Young et al. which showed period in the group as a whole. However, within the that signs of malnutrition were present in a considergroup individual changes in BW were strongly correl- able proportion of patients who had been on PD for ated with individual changes in BF (r=0.66, P= more than 3 months [2]. In this multi-center study, 0.0001). Twenty-six patients were examined during the nutritional status was assessed by anthropometric and second and third year of PD. In this group, BW o/p biochemical methods. remained constant over time. However, there was a At the Department of Nephrology, Sahlgrenska small but significant decline of TBK o/p and a concom- University Hospital in Gothenburg, we used body itant increase of BF o/ p( P<0.05). No correlation was composition analyses to evaluate the nutritional eVects observed between changes in TBK and changes in of low protein diet in predialytic patients [10] as well serum albumin. as to study the nutritional status of patients on mainConclusions. The results of this study indicate, that tenance hemodialysis [11]. In 1993, body composition there may be a risk for further reduction of body cell analyses were included as a measure of nutritional mass during long-term PD treatment, while body status in the regular follow-up of PD patients. The energy stores are maintained or even increased. aim of the present study was to evaluate changes in

Potential errors in the application of mixture theory to multifrequency bioelectrical impedance analysis

Abstract: Potential errors in the application of mixture theory to the analysis of multiple-frequency bioelectrical impedance data for the determination of body fluid volumes are assessed. Potential sources of error include: conductive length; tissue fluid resistivity; body density; weight and technical errors of measurement. Inclusion of inaccurate estimates of body density and weight introduce errors of typically but incorrect assumptions regarding conductive length or fluid resistivities may each incur errors of up to 20%. Keywords: mixture theory, errors, bioelectrical impedance analysis, multiple-frequency bioelectrical impedance analysis

Human body‐fluid distribution during exercise in hot, temperate and cool environments

Abstract: Using a simultaneous-dilution technique, we investigated body-fluid volume changes during exercise in seven males, during 50 min of cycling (50% maximal work rate) in hot (36.2 degrees C), temperate (22.0 degrees C) and cool conditions (14.4 degrees C). Total body water (TBW), extracellular fluid (ECFV), plasma (PV) and erythrocyte volumes (RCV) were measured, while blood volume (BV), interstitial fluid volume (IFV), extracellular water (ECW) and intracellular water volumes (ICW) were derived. During the initial 10 min of cycling, BV decreased in all environments (P .01), primarily because of a PV reduction (P = 0.01), while IFV, ECFV and ICW were not significantly changed. By 30 min, BV recovered in the temperate and cool conditions, despite mass losses of 563 and 520 mL (respectively), but remained depleted in the hot condition (P = 0.01). The 50-min volume changes revealed that, throughout exercise, body-fluid losses appeared to be drawn primarily from the extracellular space, regardless of air temperature. In the hot condition, the PV change represented 63% of the TBW loss, with the ICW contributing 23%. It was concluded that, during cycling, progressive dehydration mainly affected the extracellular space, with the intravascular and intracellular spaces being defended in less stressful conditions.

Body composition measurements during wasting diseases.

Abstract: Body wasting is a common feature of severe chronic diseases Determination of body compartments is essential in the evaluation of patients with wasting diseases in order to optimize their nutritional support The main methods described together with their advantages and disadvantages are anthropometric measurements, bioelectrical impedance analysis, dual-energy X-ray absorptiometry, total body water, total body potassium and in-vivo neutron activation analysis The combination of dual-energy X-ray absorptiometry to measure bone and fat mass and bioelectrical impedance analysis to determine total body water and fat-free mass permits evaluation of body composition and periodic follow-up of body compartments in various pathologies Total body potassium, total body water and in-vivo neutron activation analysis are research methods that elucidate the abnormal consequences of chronic pathologies on hydration status and body cell mass

Validation of predictive equations for use of deuterium oxide dilution to determine body composition of dogs

Abstract: OBJECTIVE To validate equations predicting body composition of dogs, using deuterium oxide dilution. ANIMALS 38 female and 37 male dogs selected by defined body weight and body condition criteria. PROCEDURE Measured equilibrated deuterium concentration in serum after i.v. administration of isotope was used to determine isotope space and predict body water, fat, nitrogen, and ash contents determined from analysis of homogenized carcass. Equations predicting body composition were derived, using regression analysis, and were validated, using data-splitting techniques. RESULTS Deuterium space (in kilograms) overestimated kilograms of body water content by mean 21.8% +/- SD of 4.18%. Regression equations were derived and validated to predict kilograms of body water and ash from kilograms of deuterium space, and proportion of body water, fat, nitrogen, and ash from proportion of deuterium space. Coefficients of determination (r2) and means of standard errors of estimating new values (SEE) were, respectively, 0.993 and 0.4 kg for body water content, and 0.942 and 0.08 kg for ash content. For proportions, SEE were 2.0, 2.7, 0.1, and 0.4% for body water, fat, nitrogen, and ash, respectively. Two factors, time for isotope equilibration and whether samples were processed by vacuum sublimation, improved SEE for proportion of body water from 2.0 to 1.3% and of fat from 2.7 to 1.8%. Equations predicting absolute quantities of fat and nitrogen could be derived but not validated. CONCLUSIONS Deuterium dilution can be used to predict body composition of dogs with precision equal to that determined for other species.

Four-site skinfold anthropometry (FSA) versus body impedance analysis (BIA) in assessing nutritional status of patients on maintenance hemodialysis: which method is to be preferred in routine patient care?

Abstract: Background. Both four-site skinfold anthropometry (FSA) and bioelectrical impedance analysis (BIA) claim to be useful in routine clinical practice of maintenance dialysis as easy methods to assess nutritional status. The purpose of this study was to investigate which of these two methods is to be preferred. Methods. Both before and after dialysis nutritional and hydration status were evaluated by BIA in 20 stable hemodialysis patients. Variables of nutritional status as lean body mass (LBM) and body fat (BF) were assessed by four-site skinfold anthropometry (LBM-FSA and BF-FSA) and BIA (LBM-BIA and BF-BIA). Variables of hydration status were total body water (TBW), its distribution into intracellular and extracellular compartments (ICW and ECW, respectively) and ICW/ECW. Results. Weight loss during dialysis correlated with a change of LBM-FSA (r = 0.75. p <0.005) and also with that of LBM-BIA (r = 0.69, p <0.005). To promote reliability of follow-up measurements in intervention studies it is warranted to evaluate nutritional status in an unchanged hydration status. The highly significant correlation (r = 0.93, p <0.005) between the two techniques and the comparability between means and SD indicate that both techniques were almost equivalent to each other, although, compared to LBM-BIA, LBM-FSA was less affected by changes in fluid status. The same held true for BF-BIA and BF-FSA. BF-FSA correlated significantly with BF-BIA (r = 0.65, p <0.005), whereas no difference of mean ± SD was found between BF-FSA and BF-BIA. Conclusion. FSA and BIA are almost comparable techniques to assess both LBM and BF, although FSA is less affected by changes in fluid status. However, assessing LBM in normohydration is mandatory. Compared with FSA, BIA is able to establish hydration status and lacks depency on operator interpretation. Therefore, in routine patient care the BIA technique is the one to be preferred.

Description and Evaluation of a Method Based on Magnetic Resonance Imaging to Estimate Adipose Tissue Volume and Total Body Fat in Infants

Abstract: Information about body fatness is important during nutritional assessment of infants, but current methods to estimate body composition in vivo are often not applicable in infants. Therefore, a new method based on magnetic resonance imaging (MRI) was developed. This method, which can assess the volume and distribution of adipose tissue (AT) as well as total body fat, was applied in 11 healthy full-term infants. Their total body water was also estimated using the isotope dilution technique. Adipose tissue volume (ATV) was calculated from AT area in 16 images of the body taken by an MRI scanner (1.5 tesla). AT area was assessed using a computer program in which AT criteria was defined by the observer. ATV of the infants was therefore evaluated once by three observers and twice by a fourth observer. The different observers estimated total, s.c., and non-s.c. ATV with a precision that varied between 1.9 and 7.2%, 2.0 and 4.8%, and 4.2 and 40.7%, respectively. Variations during AT area calculations accounted for a large part of the imprecision when assessing total and s.c. ATV. The linear relationship between percent total body water and total ATV in relation to body weight was significant in all evaluations. Although average total ATV varied when estimated by the four observers, there was, within each evaluation, a fairly constant order between infants with respect to their ATV. It is concluded that the MRI procedure represents a useful possibility to assess body fatness in infants.