Showing papers on "Body water published in 1994"

Lean body mass estimation by creatinine kinetics.

Abstract: A new technique for estimating lean body mass (LBM) from creatinine kinetics has been developed. It is based on the principle that creatinine production is proportional to LBM and that, in the steady state, creatinine production is equal to the sum of creatinine excretion (urinary and dialytic) and metabolic degradation. This technique was applied to 17 normal subjects, 26 stable, chronic hemodialysis (HD) patients, and 71 stable, chronic peritoneal dialysis (PD) patients. In the HD group, LBM was also determined by bioimpedance in 11 patients and calculated from total body water, measured as the volume of urea distribution of a sterile urea infusion, in 15 patients. In normal subjects and in the PD group, LBM was assessed by creatinine kinetics as well as by bioimpedance, near infrared, and anthropometric techniques. In the HD patients, LBM by creatinine kinetics correlated significantly with LBM from total body water and the bioimpedance technique. There was no statistical difference between the total body water and creatinine kinetics techniques, but the bioimpedance values were systematically higher than those obtained by the kinetic technique. In the PD group and in normal volunteers, LBM values by creatinine kinetics correlated significantly with the other methods but were lower. Forty-seven percent of the HD patients and 66% of the PD patients had significantly lower LBM by creatinine kinetics than expected for their sex and age. Estimation of LBM by creatinine kinetics is proposed as a simple and convenient technique for the routine nutritional assessment of dialysis patients.

Body fluid balance in dehydrated healthy older men : thirst and renal osmoregulation

Abstract: We examined osmotic control of thirst and free water clearance in healthy older (65+, n = 10) and younger (Y, n = 6) subjects during a 3-h rehydration period after an approximately 2.4% decrease in body weight. Plasma volume (PV), plasma osmolality (Posm), renal function, and thirst were measured before and after dehydration and during rehydration. In 65+, baseline PV was lower (43.1 +/- 1.6 vs. 48.1 +/- 2.5 ml/kg), Posm was higher (287 +/- 1 vs. 281 +/- 2 mosmol/kgH2O), and perceived thirst was lower than in Y. During dehydration, the osmotic threshold for increased thirst was shifted to a higher Posm in 65+. Total fluid intake was greater in Y than in 65+ (16.6 +/- 4.1 vs. 8.9 +/- 2.0 ml/kg); however, the relation between thirst and the rate of fluid intake was identical. Thus the blunted rehydration in 65+ is related to a lower overall sensation of thirst. The stimulus-response characteristics of osmotic control of free water clearance was similar in 65+ and Y; however, 65+ operated around a higher Posm and on a less-steep portion of the stimulus-response curve. These data support the hypothesis that the hyperosmotic hypovolemic state of healthy older individuals is not a result of a simple water deficit but represents a shift in the operating point for control of body fluid volume and composition.

Development of two methods to estimate body composition of bears

Abstract: The measurement of body composition in black bears (Ursus americanus), brown bears (U. arctos), and polar bears (U. maritimus) was investigated by means of isotopic water dilution and bioelectrical impedance analysis (BIA). The basic relationships between body lipid, water, protein, and ash were determined by direct chemical measurement of 13 black and 6 brown bears. Body water and lipid content as a percentage are highly correlated (r2 = 0.98, standard error of the estimate (SEE) = 1.1%) and inversely proportional. The dry, lipid-free mass averaged 83.5 ± 1.6% protein and 16.5 ± 1.6% ash. Either isotopic water dilution or BIA can be used to estimate body lipid content of healthy, uninjured bears (r2 = 0.93, SEE = 2.7% and r2 = 0.96, SEE = 2.2%, respectively). Isotopic water equilibrated with body water by 150 min. Abscesses and recent injuries (i.e., gunshot or snare wounds) produced erroneous body composition estimates when BIA was used, but only when the injury was in the conductor path between the BIA...

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

Abstract: 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.

In vivo measurement of fatty acids and cholesterol synthesis using D2O and mass isotopomer analysis

Abstract: The synthesis of palmitate, stearate, and cholesterol in liver and nervous tissues (brain, cord, and nerve) of Sprague-Dawley rats was determined using deuterated water (D2O) and mass isotopomer analysis. Rats were given 4% deuterium in their drinking water after each receiving an intraperitoneal priming dose. Animals were killed at 1, 2, 4, and 8 wk for deuterium enrichment in body water and determination of mass isotopomer distribution in lipids from various tissues. In 1 wk, the enrichment in the body water reached a plateau of 2.6%, which is 65% of that in the drinking water. We observed the maximum incorporation number (N) in all lipids to be higher than those previously observed, being 22, 24, and 30 for liver palmitate, stearate, and cholesterol, respectively, and N may vary among tissues. Using a single exponential model, we found the half-time (t1/2) and the plateau levels of the newly synthesized lipids of the nervous tissues (t1/2 values ranging from 5 to 28 days) to be different from those of the liver (t1/2 values < or = 4 days) in this relatively long-term study. Mass isotopomer distribution analysis and D2O can be used not only to quantitate the replacement rate of many lipids in various compartments but may also be used to elucidate the tissue-specific synthetic pathways from N.

Apparent paradox of neurohumoral axis inhibition after body fluid volume depletion in patients with chronic congestive heart failure and water retention.

Abstract: BACKGROUND--Hypovolaemia stimulates the sympathoadrenal and renin systems and water retention. It has been proposed that in congestive heart failure reduction of cardiac output and any associated decrease in blood pressure cause underfilling of the arterial compartment, which promotes and perpetuates neurohumoral activation and the retention of fluid. This study examined whether an intravascular volume deficit accounts for patterns that largely exceed the limits of a homoeostatic response, which are sometimes seen in advanced congestive heart failure. METHODS AND RESULTS--In 22 patients with congestive heart failure and water retention the body fluid mass was reduced by ultrafiltration and the neurohumoral reaction was monitored. A Diafilter, which was part of an external venous circuit was regulated to produce 500 ml/hour of ultrafiltrate (mean (SD) 3122 (1199) ml) until right atrial pressure was reduced to 50% of baseline. Haemodynamic variables, plasma renin activity, noradrenaline, and aldosterone were measured before and within 48 hours of ultrafiltration. After ultrafiltration, which produced a 20% reduction of plasma volume and a moderate decrease in cardiac output and blood pressure (consistent with a diminished degree of filling of the arterial compartment), there was an obvious decrease in noradrenaline, plasma renin activity, and aldosterone. In the next 48 hours plasma volume, cardiac output, and blood pressure recovered; the neurohumoral axis was depressed; and there was a striking enhancement of water and sodium excretion with resolution of the peripheral oedema and organ congestion. The neurohumoral changes and haemodynamic changes were not related. There were significant correlations between the neurohumoral changes and increase in urinary output and sodium excretion. CONCLUSIONS--In advanced congestive heart failure arterial underfilling was not the main mechanism for activating the neurohumoral axis and retaining fluid. Because a decrease in circulating hormones was associated with reabsorption of extravascular fluid it is likely that hypoperfusion and/or congestion of organs, such as the kidney and lung, reduce the clearance of circulating noradrenaline and help to keep plasma concentrations of renin and aldosterone raised. A positive feedback loop between fluid retention and plasma hormone concentrations may be responsible for progression of congestive heart failure.

Calculation of total body water in infancy

Abstract: Objective: Total body water can be calculated using stable isotopes by two alternative approaches known as the plateau method and the back extrapolation method. These methods treat the isotopic data in different ways and consequently do not necessarily produce identical values for total body water. Total body water was therefore calculated using both methods using two different tracers, H-2 and O-18.

Differences between young and old females in the five levels of body composition and their relevance to the two-compartment chemical model.

Abstract: BACKGROUND Body composition differs between young and old females, although the magnitude of these age-related changes remains uncertain. This uncertainty persists because methodology applied in earlier studies required assumptions that may be age-dependent and also because studies included young and old subjects who differed substantially in body size and health status. METHODS To resolve these earlier concerns we examined components at the atomic, molecular, cellular, tissue-system, and whole body levels of body composition in 19 weight- and height-matched pairs of young (age 19-35 yrs) and old (age > 65 yrs) healthy White females. Isotope dilution, dual photon, whole-body counting, hydrodensitometry, and anthropometric methods were used either alone or in combination to produce multicomponent models. RESULTS Old females had significantly more fat, greater truncal skinfolds and circumferences, and significantly less fat-free body mass (FFM), total body potassium (TBK), total body water (TBW), and bone mineral than did their young matched counterparts. Skeletal muscle mass was less in the old females, although the magnitude of the difference from young females varied between the three indices examined. The main assumptions (i.e., TBW/FFM = 0.73 kg/kg and density of FFM = 1.100 g/cc) which the widely used two-compartment TBW and hydrodensitometry methods are based on were not significantly different in young and old females. In contrast, the main assumed steady-state value for the two-compartment TBK method (TBK/FFM = 64.2 mmol/kg) was significantly lower (p < .001) in the old females. CONCLUSION New approaches thus allow for a critical reexamination of body composition in elderly subjects, and these methods also give new insight into less complex widely used body composition techniques.

A Pharmacokinetic Model of Topotecan Clearance from Plasma and Cerebrospinal Fluid

Abstract: We present a physiological pharmacokinetic model that describes the plasma and cerebrospinal fluid (CSF) concentrations of topotecan [(S)-9-dimethylaminomethyl-10-hydroxyamptothecin hydrochloride, SK&F 104864-A, NSC 609699] following i.v. and intraventricular administrations in monkeys. The model consists of three physical spaces: the CSF, the plasma, and a body compartment. The model incorporates such processes as reversible conversion of topotecan lactone to an inactive hydroxy acid form, microvascular exchange between CSF and plasma, bulk CSF flow, exchange between plasma and body compartments, and elimination of drug from the plasma compartment. Several parameters in the model were obtained from published literature on the physiology of the monkey. The model was then fit to the plasma and CSF data to deduce the other parameters. Calculated clearances of topotecan lactone and total drug from the CSF after intraventricular injection were 3.9 and 2.2 ml/h, respectively. Clearances of topotecan lactone and total drug from the plasma following a 10-min infusion were 26.3 liters/h/m2 and 17.8 liters/h/m2, respectively. The calculated ratios of the area under the concentration curve in the CSF following i.v. infusion to the area under the concentration curve in plasma were 0.11 and 0.19 for topotecan and total drug, respectively, indicating significant CSF penetration. The volume of distribution was 0.77 liters/kg, which represents distribution in a volume approximating total body water. The forward and reverse rate constants for the lactone-to-hydroxy acid conversion were 1.0 and 0.29 h-1, respectively. Comparison of the clearances (normalized to body surface area) with values reported for mice and humans shows reasonable similarity across species. This pharmacokinetic model may help guide future development and refinement of clinical protocols, especially in the treatment of diseases of the central nervous system.

Comparative evaluation of body composition methods and predictions, and calculation of density and hydration fraction of fat-free mass, in obese women

Abstract: The objective of this study was to apply a three-component model of body composition to a group of obese women in order to (a) establish the relative value of a number of readily available prediction equations by comparison of the extent of agreement between these predictions and body composition estimated by the model and other reference methods and (b) evaluate density and hydration of fat-free mass. Estimation of body composition was carried out by reference methods and prediction equations and the usefulness of these prediction equations for application specifically to obese women was evaluated. The subjects were 15 obese, otherwise healthy, Caucasian women (body mass index > 30kg/m2 and body fat > 40% of body weight, as originally determined using densitometry). Body composition was estimated using three established reference methods (deuterium dilution which primarily measures total body water, densitometry for body fat and fat-free mass and total body potassium) and the three component model constructed from deuterium dilution and densitometry. Density and hydration fraction of the fat-free mass were calculated from appropriate values obtained as integral parts of the three-component model. In addition, body composition was predicted from various prediction equations incorporating weight and height (some of which include a factor for age), from a number of prediction equations utilizing different terms involving the same whole-body bio-electrical impedance measurement and from measurements of skinfold thickness and near infrared interactance. The extent of agreement between methods was assessed using bias and 95% limits of agreement. Mean density of fat-free mass was found to be 1.104 kg/l (s.d. 0.006kg/l) with a range of 1.093 to 1.117 kg/l, and mean hydration fraction was 0.712 (s.d. 0.016) with a range of hydration from 68.2% to 75.1% (all values were calculated from the three-component model). In general, the reference methods (densitometry, deuterium dilution, the three-component model and total body potassium) demonstrated better agreement with each other than with the prediction methods or equations. In these obese women, skinfold thickness measurements are apparently less reliable (large bias and 95% limits of agreement) than in the lean subjects of a variety of other studies. A majority of interpretations of weight and height measurements and predictions incorporating impedance/resistance measurements are apparently not applicable to this group of obese women, due to large values for both bias and 95% limits of agreement.(ABSTRACT TRUNCATED AT 400 WORDS)

Measuring the body composition of elderly subjects: a comparison of methods

Abstract: There is a paucity of data on differences between methods for the assessment of body composition in elderly subjects. Studies on younger adults suggest that such differences are of some practical significance at the individual level. In the present study the following methods of estimating percentage body fatness (BF%) were compared in healthy elderly men and women (mean age 70 (SD 6) years: densitometry; skinfold thickness; total body water; bioelectrical impedance (BIA) using an age-specific predictive equation and the manufacturers' equation; body mass index (BMI). Though BF% estimates from the various methods tended to be highly correlated with those from densitometry and with each other, differences between methods at the individual level were marked. In particular, the age-specific equations based on BMI and BIA systematically overestimated BF% relative to the other methods. Biases between BF% estimates derived from densitometry, skinfolds, BIA (manufacturers' equation) and total body water were less marked, indicating little evidence of systematic differences between these methods in elderly subjects. Individual differences between methods were slightly greater than those reported in some studies of younger adults, but this may be of little practical significance, and may be considered inevitable in view of variability between and within subjects in the extent to which the underlying assumptions of these two-component methods are met in elderly subjects.

Renal and Extrarenal Considerations in High-Dose Mannitol Therapy

Abstract: It is well recognized that the large doses of mannitol used in treating cerebral edema alter extracellular fluid (ECF) volume, osmolality, and composition to a degree which, under some circumstances, can lead to acute renal failure, cardiac decompensation, and other difficulties It is less well appreciated that the patient's body habitus, age, total body water content relative to body weight, pretreatment plasma sodium concentration and plasma osmolality, and the presence of edema or ascites also can influence the degree of ECF change and the rate of mannitol excretion to a significant degree Here, we show how these changes occur and the way in which their magnitude can be predicted prior to therapy so as to minimize the risk of an adverse result

Use of bioelectrical impedance analysis to assess body composition of seals

Abstract: Bioelectrical impedance analysis (BIA) measures resistance and reactance of a current as it passes through an organism. The validity of using BIA as a tool to measure body water content, and hence body composition and condition, was tested on harp and ringed seals. The resistance and reactance readings from BIA were compared to estimates of total body water (TBW) determined via tritiated water dilution. The relationship between resistance and TBW (% of body mass) was linear after logarithmic transformation and the two variables were highly correlated. We describe the electrode configuration and placements which provide reliable results in these seals. Our findings indicate that BIA has considerable potential as an inexpensive, rapid, and reliable technique for estimating body composition of phocid seals.

Are bioelectric impedance measurements valid in patients with cystic fibrosis

Abstract: This pilot study compared the use of bioelectric impedance analysis (BIA), a rapid, portable, and painless method of measuring body composition, to isotope dilution in patients with and without cystic fibrosis (CF). Many methods exist for measuring body composition but these measures can be difficult to use in the clinical setting. BIA has been validated as a tool for nutritional assessment in healthy adults, but it must be validated in patient populations with specific disease-related nutritional problems, such as CF. Ten ambulatory patients with CF were selected along with ten controls matched for age, sex, and body mass index (BMI; wt/ht2). Total body water (TBW) was determined using isotoperatio mass spectrometry on urine specimens before and after patients consumed 0.2 g/kg deuterium-rich water. BIA was performed using a tetrapolar technique; 500 microA of current at 50 kHz was introduced and the voltage drop measured. Seven men and three women were studied in each group. Median age was 27 (range, 18-39) and median BMI was 19.2 (range, 16.7-30.1) in CF adults. Median age was 27.5 (range, 15-43) and median BMI was 20.7 (range, 19.4-31.6) in controls. The resistance index (RI; ht2/resistance) correlated strongly with TBW in patients with CF (r = 0.88; y = 0.482x + 11.138; p < 0.05) as well as in controls (r = 0.87; y = 0.661x + 1.299; p < 0.05). We conclude that BIA is a rapid, portable, and painless method for measuring body composition that correlates well with the deuterium-dilution method.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrafiltration in peritoneal dialysis

Abstract: There is a clinical requirement to remove excess body water, electrolytes, and other uremic toxins on a regular basis from patients with end-stage renal failure. During extracorporeal artificial kidney treatment, fluid is removed by simply applying a difference in hydrostatic or hydraulic pressure across the synthetic membrane. This approach is impractical during peritoneal dialysis; instead, fluid is removed from the patient by creating a difference in osmotic pressure between dialysis solution and blood. Thus, fluid removal during peritoneal dialysis is primarily by osmosis and is commonly referred to as osmotic ultrafiltration (or simply ultrafiltration) because of the similarities between transmembrane fluid movement by osmosis and ultrafiltration [1]. We will focus in this chapter on describing both the driving forces that move fluid across the peritoneum and the rate of solute transport that accompanies this transperitoneal fluid movement.

Effect of recombinant human growth hormone on cellular sodium metabolism

Abstract: 1. The effect of treatment with recombinant human growth hormone on urinary sodium excretion, total body water, the renin-angiotensin system and erythrocyte sodium metabolism was investigated in 16 adults with growth hormone deficiency. 2. Total body water was determined by isotopic dilution, and erythrocyte electrolyte contents were analysed using flame photometry. The rate of sodium influx and the efflux rate constant of sodium were calculated from values of 22Na in erythrocytes in vitro. 3. One week of treatment with recombinant human growth hormone caused a decrease in urinary sodium excretion in 9/10 patients and an increase in erythrocyte sodium content. Total body water, plasma renin activity, angiotensin II concentration and transmembrane sodium transport were unaltered. 4. Six months of treatment with recombinant human growth hormone caused significant increases in total body water, erythrocyte sodium content and sodium transmembrane influx. Plasma renin activity tended to increase, whereas blood pressure and serum sodium and potassium concentrations remained unchanged. After 6 months on recombinant human growth hormone total body water showed a significant negative correlation with plasma renin activity. 5. The enhanced erythrocyte sodium transport, if this reflects what happens in the renal tubular cell, combined with a decrease in urinary sodium excretion, during treatment with recombinant human growth hormone could indicate an increase in tubular sodium reabsorption induced by the hormone. An increased plasma renin activity associated with the lack of blood pressure rise would reinforce sodium and water retention.

Comparison of D2O and ethanol dilutions in total body water measurements in humans

Abstract: Total body water was measured by ethanol dilution and D2O stable isotope dilution in a group of 20 healthy volunteers (5 females and 15 males), predominantly 23- to 31-year-old students. Both indicator substances were given orally with an ethanol burden of 0.8 g/kg body weight and a D2O burden of 0.1 g/kg body weight after 12-h food and fluid restriction. This first direct comparison of total body water (TBW) from ethanol and D2O dilutions revealed the ethanol compartments to be smaller than those of D2O. The quotient of TBW (ethanol)/TBW (D2O) was 97.7% , which is the order of the quotient TBW (H2 18O)/TBW (D2O) (=97%), well known from the literature and taken to represent relatively exactly the value of TBW overestimation (based on H/D exchange for acid protons) following D2O dilution [36]. Thus the value of TBW (ethanol) is almost identical to that of H2 18O, which provides direct evidence that ethanol is distributed only in the body water.