Bromide space determination using anion-exchange chromatography for measurement of bromide

Use of bioelectrical impedance spectroscopy to provide a measure of body composition in sows

The ability to accurately estimate fat mass and fat-free mass (FFM) has the potential to improve the way in which sow body condition can be managed in a breeding herd. Bioelectrical impedance spectroscopy (BIS) has been evaluated as a practical technique for assessment of body composition in several livestock species, but similar work is lacking in sows. Bioelectrical impedance uses population-specific algorithms that require values for the apparent resistivities of body fluids and body proportion factors. This study comprised three major aims: (i) to derive apparent resistivity coefficients for extracellular water (ECW) and intracellular water (ICW) required for validation of BIS predictions of total body water (TBW) in live sows against standard reference tracer dilution methods; (ii) to develop predictions of TBW to body composition prediction algorithms, namely FFM, by developing a body geometry correction factor (Kb) and (iii) to compare the BIS predictions of FFM against existing impedance predictors and published prediction equations for use in sows, based on physical measurements of back-fat depth and BW (P2-based predictors). Whole body impedance measurements and the determination of TBW by deuterium dilution and ECW by bromide dilution were performed on 40 Large White x Landrace sows. Mean apparent resistivity coefficients of body fluids were 431.1 Ω.cm for ECW and 1827.8 Ω.cm for ICW. Using these coefficients, TBW and ECW were over-estimated by 6.5 and 3.3%, respectively, compared to measured reference values, although these differences were not statistically different (P > 0.05). Mean Kb was 1.09 ± 0.14. Fat-free mass predictions were 194.9 kg, which equates to 60.9% of total sow weight, and 183.0 kg for BIS and the deuterium dilution method, respectively. Mean differences between the predicted and measured FFM values ranged from -8.2 to 32.7%, but were not statistically different (P > 0.05). Method validation (leave-one-out procedure) revealed that mean differences between predicted and measured values were not statistically significant (P > 0.05). Of the impedance-based predictors, equivalence testing revealed that BIS displayed the lowest test bias of 11.9 kg (8.2%), although the P2-based prediction equations exhibited the lowest bias and percentage equivalence, with narrow limits of agreement. Results indicate although differences between mean predicted and measured values were not significantly different, relatively wide limits of agreement suggest BIS as an impractical option for assessing body composition in individual sows compared to the use of existing prediction equations based on BW and back fat.

Assessment of Fluid Status in Peritoneal Dialysis Patients

Objectives

To assess the influence of abnormalities in fluid status and body composition on agreement between multifrequency bioimpedance analysis (MF-BIA), segmental BIA (ΣBIA), the Watson formula, and tracer dilution techniques.

Design

Cross-sectional.

Setting

Multicenter.

Patients

40 patients (29 males, 11 females) on peritoneal dialysis (PD).

Main Outcome Measures

Agreement between the various techniques used to assess total body water (TBW) [MF-BIA, deuterium oxide (D2O), and the Watson formula] and extracellular water (ECW) [MF-BIA, bromide dilution (NaBr), and ΣBIA], also in relation to the relative magnitude of the body water compartments [ECW (NaBr):body weight (BW) and TBW (D2O):BW] and body composition (DEXA). Second, the relation between body water compartments with echocardiographic parameters.

Results

Wide limits of agreement were observed between tracer dilution techniques and MF-BIA [TBW (D2O – MF-BIA) 2.0 ± 3.9 L; ECW (NaBr – MF-BIA) –2.8 ± 3.9 L], which were related to the relative magnitude of the body water compartments: r = 0.70 for ECW and r = 0.40 for TBW. ΣBIA did not improve the agreement [ECW (NaBr – ΣBIA): 3.7 ± 2.9 L]. Also, wide limits of agreement were observed between D2O and the Watson formula (–2.3 ± 3.3 L). The difference between D2O and Watson was related to hydration state and to percentage of fat mass ( r = 0.70 and r = –0.53, p < 0.05). Both ECW and TBW as assessed by BIA and tracer dilution were related to echocardiographic parameters.

Conclusion

Wide limits of agreement were found between MF-BIA and ΣBIA with dilution methods in PD patients, which were related to hydration state itself. The disagreement between the Watson formula and dilution methods was related to both hydration state and body composition.

Fluid Status, Blood Pressure, and Cardiovascular Abnormalities in Patients on Peritoneal Dialysis

♦ Objective

Hypertension, reduced arterial distensibility, and left ventricular hypertrophy (LVH) are risk factors for mortality in hemodialysis patients. However, few studies have focused on the relation between fluid status, blood pressure (BP), and cardiovascular abnormalities in peritoneal dialysis (PD) patients. This study was designed, first, to assess, using tracer dilution techniques, fluid status in PD patients compared to a control population of stable renal transplant (RTx) patients; second, to study the relation between fluid status, BP, and arterial wall abnormalities; third, to assess the determinants of cardiac structure; and last, to compare office and ambulatory BP measurements with respect to cardiac abnormalities.

♦ Design

Cross-sectional study.

♦ Setting

Multicenter study.

♦ Patients

41 stable PD patients with a mean Kt/V urea of 2.4 ± 0.7, and 77 stable RTx patients.

♦ Intervention

Fluid status was assessed by tracer dilution techniques: extracellular volume (ECV) with bromide dilution; total body water (TBW) with deuterium oxide; and plasma volume (PV) with dextran 70. Echocardiography was performed to assess left ventricular mass (LVM), left ventricular end diastolic diameter (LVEDD), and relative wall thickness as indicators of LVH. Echography of the common carotid artery was performed to assess arterial distensibility. Both office and 24-hour ambulatory BP measurements were performed.

♦ Results

Fluid status, as assessed by ECV corrected for body surface area (BSA) (ECV:BSA), was significantly different between PD and RTx patients (9.4 ± 2.6 vs 8.6 ± 1.2 L/m2, p < 0.05). In 36.6% of the PD patients, ECV:BSA was above the 90th percentile of the RTx patients. Fluid status corrected for BSA, assessed by TBW (TBW:BSA), ECV (ECV:BSA), or plasma volume (PV:BSA), was significantly related to diastolic BP (DBP) ( r = 0.35, r = 0.37, r = 0.53; p < 0.05). Arterial distensibility of the common carotid artery was related to systolic BP (SBP) ( r = –0.36, p < 0.05). ECV was significantly related to LVEDD ( r = 0.41, p < 0.05) as a marker of eccentric LVH, whereas arterial distensibility was related to relative wall thickness ( r = –0.53, p < 0.001) as a marker of concentric LVH. An abnormal day–night BP rhythm, which was not related to fluid status, was observed in 68.4% of patients. Ambulatory DBP and SBP but not office DBP and SBP were related to LVM ( r = 0.43, r = 0.46; p < 0.01).

♦ Conclusions

A large proportion of PD patients whose treatment prescriptions are in accordance with the Dialysis Outcomes Quality Initiative guidelines were found to be overhydrated compared with a population of stable RTx patients. Fluid status was significantly related to DBP and eccentric LVH, whereas arterial distensibility of the common carotid artery was significantly related to SBP and concentric LVH. In contrast to ambulatory BP, office BP was not related to LVM.

Clinical usefulness of bioimpedance analysis for assessing volume status in patients receiving maintenance dialysis

Chronic volume overload is associated with left ventricular hypertrophy and high cardiovascular mortality in patients undergoing dialysis. Therefore, estimating body fluid status is important in these patients. However, most dry-weight assessments are still performed clinically, while attempts have been made to measure the volume status and dry weight of patients undergoing dialysis using bioimpedance analysis (BIA). BIA uses the electrical properties of the human body to alternate current flow and measures resistance values to estimate body water content and composition. BIA is divided into single-frequency BIA, multi-frequency BIA, and bioimpedance spectroscopy (BIS) according to the number of frequencies used, and into whole-body and segmental BIA according to whether or not the whole body is divided into segments. Extracellular water (ECW), intracellular water, and total body water (TBW) contents can be measured with BIA. Dry weight can be estimated by measuring the volume overload of the patient through the ECW/TBW and ECW-to-body weight ratios. Other estimation methods include the normovolemia/hypervolemia slope method, a resistance-reactance (RXc) graph, overhydration measurements using a body composition monitor, and calf BIS. In this review, we will examine the principles of BIA, introduce various volume status measurement methods, and identify the optimal method for patients undergoing dialysis.

Changes in red blood cell volume during transition of heart failure status: a reflection of cellular hydration status?

This study examined how changes in heart failure (HF) status induce changes in the index of erythrocyte hydration based on mean red blood cell volume (MCV). Data from 47 HF patients (32% men; 78.2 ± 9.7 years) that experienced worsening and recovery of HF were analysed. Blood tests included measurements of MCV, albumin, serum solutes and b-type natriuretic peptide (BNP). Among a total of 47 worsening HF events, changes in MCV were positively correlated with changes in body weight (r = 0.31, p = .034), serum sodium (r = 0.417, p = .0036), and chloride (r = 0.457, p = .0012), and negatively correlated with changes in blood urea nitrogen (r= -0.389, p = .0069) and creatinine (r= -0.494, p = .0004). At recovery from worsening of HF by conventional diuretic therapy, change in MCV was positively correlated with the change in body weight (r = 0.457, p = .0012), serum sodium (r = 0.466, p = .001) and chloride (r = 0.484, p = .0006). Multivariate regression analysis demonstrated an independent association between the increase in serum chloride and MCV from stability to worsening of HF (odds ratio [OR] 6.02, 95% confidence interval [CI] 1.09-33.2, p = .039) and the increase or absence of change in serum chloride concentration and preserved MCV after decongestion (OR 11.5, 95% CI 1.53-85.9, p = .017). In conclusion, this study demonstrates that the changes in MCV under transition in HF status do not reflect a change that occurs in parallel with changes in HF-related markers, such as body weight and serum BNP level, but is independently associated with a change in the serum chloride concentration. Whether changes in MCV actually reflect the bodily cellular hydration status warrants further research.

Relation of Disease with Standardized Phase Angle among Older Patients

BACKGROUND

A low phase angle (PA) has been associated with negative outcome in specific diseases. However, many patients suffer from several co-morbidities. This study aims at identifying the impact of the type and the severity of diseases on PA in a retrospective cohort study of older people.

METHODS

We included all people ≥65 years who underwent a PA measurement (Nutriguard®) between 1990 and 2011 at the Geneva University Hospitals. PA was standardized for gender, age and body mass index according to German reference values. Co-morbidities were reported in form of the Cumulative Illness Rating Scale which considers 14 different organs/systems (disease categories), each rated from 0 (healthy) to 4 (severe illness) (severity grades). The association between the diseases categories and standardized PA was evaluated by a multivariate linear regression. For each significant disease category, we performed univariate regression models. The adjusted R2 was used to identify the best predictors of standardized PA. We considered that the severity grade affected standardized PA if there was a progressive decrease in the regression coefficients.

RESULTS

We included 1181 people (37% women). The multivariate regression model showed that the disease categories explain 17% of the variance of standardized PA. Many disease categories affect standardized PA and the ones best associated with standardized PA were the hematopoietic and vascular (R2 7.4%), the musculo-skeletal (R2 5.5%) and the respiratory (R2 4.0%) diseases. The regression coefficients in the univariate linear regression model decreased progressively with higher severity grades in respiratory (-0.15, -0.27, -0.55, -0.67) and musculo-skeletal diseases (-0.09, -0.46, -0.85, -0.86).

CONCLUSIONS

Many different diseases affect standardized PA. The higher the severity grade in musculo-skeletal and respiratory diseases, the lower is the standardized PA.

Body Composition Tools for Assessment of Adult Malnutrition at the Bedside: A Tutorial on Research Considerations and Clinical Applications

Because of the key role played by the body's lean tissue reserves (of which skeletal muscle is a major component) in the response to injury and illness, its maintenance is of central importance to nutrition status. With the recent development of the Academy of Nutrition and Dietetics/American Society for Parenteral and Enteral Nutrition diagnostic framework for malnutrition, the loss of muscle mass has been recognized as one of the defining criteria. Objective methods to evaluate muscle loss in individuals with acute and chronic illness are needed. Bioimpedance and ultrasound techniques are currently the best options for the clinical setting; however, additional research is needed to investigate how best to optimize measurements and minimize error and to establish if these techniques (and which specific approaches) can uniquely contribute to the assessment of malnutrition, beyond more subjective evaluation methods. In this tutorial, key concepts and statistical methods used in the validation of bedside methods to assess lean tissue compartments are discussed. Body composition assessment methods that are most widely available for practice and research in the clinical setting are presented, and clinical cases are used to illustrate how the clinician might use bioimpedance and/or ultrasound as a tool to assess nutrition status at the bedside. Future research needs regarding malnutrition assessment are identified.

Long-Term Body Composition Changes in Women Following Roux-en-Y Gastric Bypass Surgery

BACKGROUND

Although most individuals experience successful weight loss following Roux-en-Y gastric bypass (RYGB), weight regain is a concern, the composition of which is not well documented. Our aim was to evaluate changes in body composition and handgrip strength as a measure of functional status in participants from a previous 1-year post-RYGB longitudinal study who had undergone RYGB approximately 9 years prior.

METHODS

Five women from an original larger cohort were monitored pre-RYGB and 1.5 months, 6 months, 1 year, and 9 years post-RYGB. Body composition was assessed at all time points using dual energy x-ray absorptiometry and multiple dilution. Handgrip strength was measured using a digital isokinetic hand dynamometer (Takei Scientific Instruments, Ltd, Tokyo, Japan).

RESULTS

Mean time to final follow-up was 8.7 years. Lean soft tissue (LST) loss over the ~9-year period was on average 11.9 ± 5.6 kg. Compared with 1-year post-RYGB, 9-year LST was 4.4 ± 3.0 kg lower ( P = .03). Fat-free mass decreased over the 9-year period by 12.6 ± 5.8 kg. Mean fat mass (FM) decreased from 75.4 ± 22.6 kg pre-RYGB to 35.5 ± 21.5 kg 1 year post-RYGB but then trended toward an increase of 8.6 ± 7.0 kg between 1 year and 9 years post-RYGB ( P = .053). Loss of LST was correlated with loss of handgrip strength ( r = 0.64, P = .0005).

CONCLUSION

The continued loss of lean mass associated with decreased handgrip strength occurring with long-term trend toward FM regain post-RYGB is concerning. The loss of LST and functional strength carries particular implications for the aging bariatric population and should be investigated further.

Resistivity coefficients for body composition analysis using bioimpedance spectroscopy: effects of body dominance and mixture theory algorithm

Body composition is commonly predicted from bioelectrical impedance spectroscopy using mixture theory algorithms. Mixture theory algorithms require the input of values for the resistivities of intra-and extracellular water of body tissues. Various derivations of these algorithms have been published, individually requiring resistivity values specific for each algorithm. This study determined apparent resistivity values in 85 healthy males and 66 healthy females for each of the four published mixture theory algorithms. The resistivity coefficients determined here are compared to published values and the inter-individual (biological) variation discussed with particular reference to consequential error in prediction of body fluid volumes. In addition, the relationships between the four algorithmic approaches are derived and methods for the inter-conversion of coefficients between algorithms presented.

A critical evaluation of bioimpedance spectroscopy analysis in estimating body composition during GH treatment: comparison with bromide dilution and dual X-ray absorptiometry

OBJECTIVE

To compare estimates by bioimpedance spectroscopy analysis (BIS) of extracellular water (ECW), fat mass (FM), and fat-free mass (FFM) against standard techniques of bromide dilution and dual energy X-ray absorptiometry (DXA) during intervention that causes significant changes in water compartments and body composition.

METHODS

Body composition analysis using BIS, bromide dilution, and DXA was performed in 71 healthy recreational athletes (43 men, 28 women; aged 18-40 years; BMI 24 ± 0.4 kg/m(2)) who participated in a double-blinded, randomized, placebo-controlled study of GH and testosterone treatment. The comparison of BIS with bromide dilution and DXA was analyzed using linear regression and the Bland-Altman method.

RESULTS

At baseline, there was a significant correlation between BIS and bromide dilution-derived estimates for ECW, and DXA for FM and FFM (P<0.001). ECW by BIS was 3.5 ± 8.1% lower compared with bromide dilution, while FM was 22.4 ± 26.8% lower and FFM 13.7 ± 7.5% higher compared with DXA (P<0.01). During treatment, the change in ECW was similar between BIS and bromide dilution, whereas BIS gave a significantly greater reduction in FM (19.4 ± 44.8%) and a greater increase in FFM (5.6 ± 3.0%) compared with DXA (P<0.01). Significant differences in body composition estimates between the BIS and DXA were observed only in men, particularly during the treatment that caused greatest change in water compartments and body composition.

CONCLUSION

In healthy adults, bioimpedance spectroscopy is an acceptable tool for measuring ECW; however, BIS overestimates FFM and substantially underestimates FM compared with DXA.

Extracellular water and blood pressure in adults with growth hormone (GH) deficiency: a genotype-phenotype association study

Objectives

Growth hormone deficiency (GHD) in adults is associated with decreased extracellular water volume (ECW). In response to GH replacement therapy (GHRT), ECW increases and blood pressure (BP) reduces or remains unchanged. Our primary aim was to study the association between polymorphisms in genes related to renal tubular function with ECW and BP before and 1 year after GHRT. The ECW measures using bioimpedance analysis (BIA) and bioimpedance spectroscopy (BIS) were validated against a reference method, the sodium bromide dilution method (Br⁻).

Design and Methods

Using a candidate gene approach, fifteen single-nucleotide polymorphisms (SNPs) in nine genes with known impact on renal tubular function (AGT, SCNN1A, SCNN1G, SLC12A1, SLC12A3, KCNJ1, STK39, WNK1 and CASR) were genotyped and analyzed for associations with ECW and BP at baseline and with their changes after 1 year of GHRT in 311 adult GHD patients. ECW was measured with the Br⁻, BIA, and BIS.

Results

Both BIA and BIS measurements demonstrated similar ECW results as the reference method. At baseline, after adjustment for sex and BMI, SNP rs2291340 in the SLC12A1 gene was associated with ECW volume in GHD patients (p = 0.039). None of the SNPs influenced the ECW response to GHRT. One SNP in the SLC12A3 gene (rs11643718; p = 0.024) and three SNPs in the SCNN1G gene [rs5723 (p = 0.02), rs5729 (p = 0.016) and rs13331086 (p = 0.035)] were associated with the inter-individual differences in BP levels at baseline. A polymorphism in the calcium-sensing receptor (CASR) gene (rs1965357) was associated with changes in systolic BP after GHRT (p = 0.036). None of these associations remained statistically significant when corrected for multiple testing.

Conclusion

The BIA and BIS are as accurate as Br⁻ to measure ECW in GHD adults before and during GHRT. Our study provides the first evidence that individual polymorphisms may have clinically relevant effects on ECW and BP in GHD adults.

Effect of short-term GH and testosterone administration on body composition and glucose homoeostasis in men receiving chronic glucocorticoid therapy

OBJECTIVE

Long-term pharmacological glucocorticoid (GC) therapy leads to skeletal muscle atrophy and weakness. The objective of this study was to investigate whether short-term treatment with GH and testosterone (T) can increase lean mass without major impairment of glucose homoeostasis in patients on GC therapy.

DESIGN, MATERIALS AND METHODS

This was a prospective, open-label, randomised, crossover study. Twelve men (age 74±6 years) on chronic GC treatment participated. The effects of 2 weeks' treatment with GH, testosterone and the combination of both on lean body mass (LBM), appendicular skeletal muscle mass (ASMM), extracellular water (ECW), body cell mass (BCM) and plasma glucose concentrations were investigated.

RESULTS

LBM increased significantly after GH (Δ1.7±1.4 kg; P=0.007) and GH+testosterone (Δ2.4±1.1 kg; P=0.003), but not testosterone alone. ASMM increased after all three treatment periods; by 1.0±0.8 kg after GH (P=0.005), 1.7±0.4 kg after GH+testosterone (P=0.002) and 0.8±1.0 kg after testosterone (P=0.018). The increase in ASMM was larger with combined treatment than either GH or testosterone alone (P<0.05). ECW increased significantly after GH+testosterone by 1.5±2.6 l (P=0.038) but not after GH or testosterone alone. BCM increased slightly after single and combined treatments, but the changes were not significant. Fasting glucose increased significantly after GH (Δ0.4±0.4 mmol/l, P=0.006) while both fasting (Δ0.2±0.3 mmol/l, P=0.045) and post glucose-load (Δ1.8±2.3 mmol/l, P=0.023) plasma glucose concentrations increased after GH+testosterone.

CONCLUSIONS

GH and testosterone induce favourable and additive body compositional changes in men on chronic, low-dose GC treatment. In the doses used, combination therapy increases fasting and postprandial glucose concentration.

Growth hormone administration: is it safe and effective for athletic performance

Human growth hormone (GH) is widely abused by athletes; however, there is little evidence that GH improves physical performance. Replacement of GH in GH deficiency improves some aspects of exercise capacity. There is evidence for a protein anabolic effect of GH in healthy adults and for increased lean body mass following GH, although fluid retention likely contributes to this increase. The evidence suggests that muscle strength, power, and aerobic exercise capacity are not enhanced by GH administration, however GH may improve anaerobic exercise capacity. There are risks of adverse effects of long-term abuse of GH. Sustained abuse of GH may lead to a state mimicking acromegaly, a condition with increased morbidity and mortality.

Multifrequency bioelectrical impedance analysis and bioimpedance spectroscopy for monitoring fluid and body cell mass changes after gastric bypass surgery

BACKGROUND & AIMS

There is a growing need for clinically applicable body composition assessment tools for extremely obese individuals. The objective of this research was to evaluate several bioimpedance techniques for monitoring changes in fluid, particularly intracellular water (reflecting body cell mass) after bariatric surgery.

DESIGN

Fifteen extremely obese women (body mass index: 48.9+/-7.0 kg/m(2); age: 48+/-9 years) were assessed before (baseline; T1), and approximately 6 weeks after gastric bypass surgery (T2) by several multifrequency bioelectrical impedance analysis approaches (MFBIA; QuadScan 4000), a bioimpedance spectroscopy device (BIS; Hydra 4200), and multiple dilution.

RESULTS

BIS provided intracellular water estimates that were comparable to criterion, based on mean comparisons, at both time points (T1: criterion: 24.2+/-3.1L, BIS: 24.0+/-3.7 L; T2: criterion: 20.6+/-3.7 L, BIS: 19.7+/-3.2L). MFBIA (with Deurenberg equations) provided comparable measures to criterion only at T2 (criterion: 20.3+/-3.7L, MFBIA: 20.6+/-2.7 L). Both MFBIA (with QuadScan proprietary equations) and BIS produced estimates of intracellular water change that were comparable to dilution. There was substantial variability in individual volume measures.

CONCLUSIONS

Although MFBIA and BIS hold promise as convenient techniques for assessing fluid changes, individual variability in measurements makes them impractical for assessment of extremely obese patients in the clinical setting.

Body fluid volumes measurements by impedance: A review of bioimpedance spectroscopy (BIS) and bioimpedance analysis (BIA) methods

This paper reviews various bioimpedance methods permitting to measure non-invasively, extracellular, intracellular and total body water (TBW) and compares BIA methods based on empirical equations of the wrist-ankle resistance or impedance at 50 kHz, height and weight with BIS methods which rely on an electrical model of tissues and resistances measured at zero and infinite frequencies. In order to compare these methods, impedance measurements were made with a multifrequency Xitron 4200 impedance meter on 57 healthy subjects which had undergone simultaneously a Dual X-ray absorptiometry examination (DXA), in order to estimate their TBW from their fat-free-mass. Extracellular (ECW) and TBW volumes were calculated for these subjects using the original BIS method and modifications of Matthie[Matthie JR. Second generation mixture theory equation for estimating intracellular water using bioimpedance spectroscopy. J Appl Physiol 2005;99:780-1], Jaffrin et al. [Jaffrin MY, Fenech M, Moreno MV, Kieffer R. Total body water measurement by a modification of the bioimpédance spectroscopy method. Med Bio Eng Comput 2006;44:873-82], Moissl et al. [Moissl UM, Wabel P, Chamney PW, Bosaeus I, Levin NW, et al. Body fluid volume determination via body composition spectroscopy in health and disease. Physiol Meas 2006;27:921-33] and their TBW resistivities were compared and discussed. ECW volumes were calculated by BIA methods of Sergi et al. [Sergi G, Bussolotto M, Perini P, Calliari I, et al. Accuracy of bioelectrical bioimpedance analysis for the assessment of extracellular space in healthy subjects and in fluid retention states. Ann Nutr Metab 1994;38(3):158-65] and Hannan et al. [Hannan WJ, Cowen SJ, Fearon KC, Plester CE, Falconer JS, Richardson RA. Evaluation of multi-frequency bio-impedance analysis for the assessment of extracellular and total body water in surgical patients. Clin Sci 1994;86:479-85] and TBW volumes by BIA methods of Kushner and Schoeller [Kushner RF, Schoeller DA. Estimation of total body water by bioelectrical impedance analysis. Am J Clin Nutr 1986;44(3):417-24], Lukaski et al. [Lukaski HC, Bolonchuk WW. Estimation of body fluid volumes using tetrapolar bioelectrical impedance measurements. Aviat Space Environ Med 1988;59:1163-9], Hannan et al. [Hannan WJ, Cowen SJ, Fearon KC, Plester CE, Falconer JS, Richardson RA. Evaluation of multi-frequency bio-impedance analysis for the assessment of extracellular and total body water in surgical patients. Clinical Science 1994;86:479-85], Deurenberg et al. [Deurenberg P, van der Koy K, Leenen R, Westrate JA, Seidell JC. Sex and age specific prediction formulas for estimating body composition from bioelectric impedance: a cross validation study. Int J Obesity 1991;15:17-25] These volumes were compared against those given by BIS method and, in the case of TBW, with those by DXA. For ECW, a good agreement was found between various BIS methods and that of Sergi while Hannan's values were higher. Both Matthie's and Moissl's methods gave mean TBW resistivities and volumes lower than those of Jaffrin's and DXA methods. Kushner et al. method gave values of TBW not significantly different from those of Jaffrin et al. and DXA, as Hannan's method in men, but Lukaski and Deurenberg methods led to an underestimation.

Gene expression profiling of human skeletal muscle in response to stabilized weight loss

BACKGROUND

Diet-induced weight reduction promotes a decrease in resting energy expenditure that could partly explain the difficulty in maintaining reduced body mass. Whether this reduction remains after stabilized weight loss is still controversial, and the molecular mechanisms are unknown.

OBJECTIVE

The objective was to investigate the effect of a stabilized 10% weight loss on body composition, metabolic profile, and skeletal muscle gene expression profiling.

DESIGN

Obese women were assigned to a 4-wk very-low-calorie diet, a 3-6-wk low-calorie diet, and a 4-wk weight-maintenance program to achieve a 10% weight loss. Resting energy expenditure, body composition, plasma variables, and skeletal muscle transcriptome were compared before weight loss and during stabilized weight reduction.

RESULTS

Energy restriction caused an 11% weight loss. Stabilization to the new weight was accompanied by an 11% decrease in the resting metabolic rate normalized to the body cellular mass. A large number of genes were regulated with a narrow range of regulation. The main regulated genes were slow/oxidative fiber markers, which were overexpressed, and the gene encoding the glucose metabolism inhibitor PDK4, which tended to be down-regulated. The knowledge-based approach gene set enrichment analysis showed that a set of genes related to long-term calorie restriction was up-regulated, whereas sets of genes related to insulin, interleukin 6, and ubiquitin-mediated proteolysis were down regulated.

CONCLUSIONS

Weight loss-induced decreases in resting metabolic rate persist after weight stabilization. Changes in skeletal muscle gene expression indicate a shift toward oxidative metabolism.

Impact of acute and chronic low-dose glucocorticoids on protein metabolism

CONTEXT

High-dose glucocorticoids cause acute protein loss by increasing protein breakdown and oxidation. Whether lower glucocorticoid doses, typical of therapeutic use, induce sustained catabolism has not been studied.

OBJECTIVE

Our objective was to assess the effect of acute and chronic therapeutic glucocorticoid doses on protein metabolism.

DESIGN AND SETTING

We conducted an open longitudinal and a cross-sectional study at a clinical research facility.

PATIENTS AND INTERVENTION

Ten healthy subjects were studied before and after a short course of prednisolone (5 and 10 mg/d sequentially for 7 d each). Twelve subjects with inactive polymyalgia rheumatica receiving chronic (>12 months) prednisone (mean = 5.0 +/- 0.8 mg/d) were compared with 12 age- and gender-matched normal subjects.

MAIN OUTCOME MEASURE

Whole-body protein metabolism was assessed using a 3-h primed constant infusion of 1-[(13)C]leucine, from which rates of leucine appearance (leucine Ra, an index of protein breakdown), leucine oxidation (Lox, index of protein oxidation) and leucine incorporation into protein (LIP, index of protein synthesis) were estimated.

RESULTS

Prednisolone induced an acute significant increase in Lox (P = 0.008) and a fall in LIP (P = 0.08) but did not affect leucine Ra. There was no significant difference between the effects of the 5- and 10-mg prednisolone doses on leucine metabolism. In subjects receiving chronic prednisone therapy, leucine Ra, Lox, and LIP were not significantly different from normal subjects.

CONCLUSION

Glucocorticoids stimulate protein oxidation after acute but not chronic administration. This time-related change suggests that glucocorticoid-induced stimulation of protein oxidation does not persist but that a metabolic adaptation occurs to limit protein loss.

Validation of Bioimpedance Spectroscopy to Assess Acute Changes in Hydration Status

PURPOSE

To validate bioimpedance spectroscopy (BIS) as a field method for measuring small, acute changes in extracellular water (ECW) during a fluid fast/rehydration manipulation.

METHODS

Seventeen young adults (15 female, 2 male) participated in a 4-d fluid fast/rehydration protocol designed to induce acute changes in ECW. ECW change (DeltaECW), measured by bioimpedance spectroscopy (BIS-DeltaECW), was compared with DeltaECW, measured by bromide dilution (Br-DeltaECW), and change in body weight (DeltaBW).

RESULTS

Regardless of hydration status, BIS-DeltaECW and Br-DeltaECW were similar; during dehydration, the mean difference between these two methods was 0.16 kg (P=0.61), and during rehydration, the mean difference was 0.58 kg (P=0.06). Assuming that DeltaECW=DeltaBW, DeltaECW as estimated from DeltaBW differed significantly from Br-DeltaECW, but not from BIS-DeltaECW. In addition, BIS-DeltaECW correlated significantly with DeltaBW (r=0.57 and 0.65 during dehydration and rehydration, respectively). However, the magnitude of DeltaECW impacted the accuracy of BIS-DeltaECW because BIS measures tended to overestimate DeltaECW at values between 0.0 and 1.0 kg and to underestimate changes at values above 1.0 kg.

CONCLUSION

These findings suggest that BIS provides an accurate estimate of DeltaECW compared with bromide dilution during short-term changes in hydration.

Thickened Fluids and Water Absorption in Rats and Humans

Individuals with dysphagia are commonly provided with oral fluids thickened to prevent aspiration. Most thickening agents are either gum-based (guar or xanthan) or are derived from modified starches. There is evidence, predominantly anecdotal, that dysphagic individuals are subclinically dehydrated. Dysphagia has a particular impact on elderly individuals and there is justifiable concern for dehydration in this population. It has been speculated that dehydration may, in part, be the result of the water-holding capacity of these thickening agents decreasing water absorption from the gut. The aim of this study was to determine the rate of intestinal absorption of water from thickened fluids. The method used was a laboratory tracer study in rats and humans in vivo. We found that there were no significant differences in water absorption rates between thickened fluids or pure water irrespective of thickener type (modified maize starch, guar gum, or xanthan gum). These data provide no support for the view that the addition of thickening agents, irrespective of type, to orally ingested fluids significantly alters the absorption rate of water from the gut.

A whole-body model to distinguish excess fluid from the hydration of major body tissues

BACKGROUND

Excess fluid (ExF) accumulates in the body in many conditions. Currently, there is no consensus regarding methods that adequately distinguish ExF from fat-free mass.

OBJECTIVE

The aim was to develop a model to determine fixed hydration constants of primary body tissues enabling ExF to be calculated from whole-body measurements of weight, intracellular water (ICWWB), and extracellular water (ECWWB).

DESIGN

Total body water (TBW) and ECWWB were determined in 104 healthy subjects by using deuterium and NaBr dilution techniques, respectively. Body fat was estimated by using a reference 4-component model, dual-energy X-ray absorptiometry, and air-displacement plethysmography. The model considered 3 compartments: normally hydrated lean tissue (NH_LT), normally hydrated adipose tissue (NH_AT), and ExF. Hydration fractions (HF) of NH_LT and NH_AT were obtained assuming zero ExF within the diverse healthy population studied.

RESULTS

The HF of NH_LT mass was 0.703 +/- 0.009 with an ECW component of 0.266 +/- 0.007. The HF of NH_AT mass was 0.197 +/- 0.042 with an ECW component of 0.127 +/- 0.015. The ratio of ECW to ICW in NH_LT was 0.63 compared with 1.88 in NH_AT. ExF can be estimated with a precision of 0.5 kg.

CONCLUSIONS

To calculate ExF over a wide range of body compositions, it is important that the model takes into account the different ratios of ECW to ICW in NH_LT and NH_AT. This eliminates the need for adult age and sex inputs into the model presented. Quantification of ExF will be beneficial in the guidance of treatment strategies to control ExF in the clinical setting.

Body fluid volume determination via body composition spectroscopy in health and disease

The assessment of extra-, intracellular and total body water (ECW, ICW, TBW) is important in many clinical situations. Bioimpedance spectroscopy (BIS) has advantages over dilution methods in terms of usability and reproducibility, but a careful analysis reveals systematic deviations in extremes of body composition and morbid states. Recent publications stress the need to set up and validate BIS equations in a wide variety of healthy subjects and patients with fluid imbalance. This paper presents two new equations for determination of ECW and ICW (referred to as body composition spectroscopy, BCS) based on Hanai mixture theory but corrected for body mass index (BMI). The equations were set up by means of cross validation using data of 152 subjects (120 healthy subjects, 32 dialysis patients) from three different centers. Validation was performed against bromide/deuterium dilution (NaBr, D2O) for ECW/TBW and total body potassium (TBK) for ICW. Agreement between BCS and the references (all subjects) was -0.4 +/- 1.4 L (mean +/- SD) for ECW, 0.2 +/- 2.0 L for ICW and -0.2 +/- 2.3 L for TBW. The ECW agreement between three independent reference methods (NaBr versus D2O-TBK) was -0.1 +/- 1.8 L for 74 subjects from two centers. Comparing the new BCS equations with the standard Hanai approach revealed an improvement in SEE for ICW and TBW by 0.6 L (24%) for all subjects, and by 1.2 L (48%) for 24 subjects with extreme BMIs (<20 and >30). BCS may be an appropriate method for body fluid volume determination over a wide range of body compositions in different states of health and disease.

Characterization of the metabolic phenotypes of Cushing's syndrome and growth hormone deficiency: a study of body composition and energy metabolism

OBJECTIVE

A comparison of the severity and distribution of perturbations in body composition and their relationship to energy metabolism in glucocorticoid excess and GH deficiency (GHD) has not been undertaken before. The aim of this study was to investigate the impact of Cushing's syndrome (CS) and GHD on whole and regional body composition and energy metabolism.

DESIGN

Cross-sectional study design.

PATIENTS

Eighteen subjects with CS (12 women, aged = 41.5 +/- 3.0 years, 24-h urinary free cortisol = 1601 +/- 361 nmol/day, normal < 300 nmol/day), 22 subjects with GHD (14 women, age = 42.9 +/- 2.9 years) and 18 normal subjects (11 women, age = 46.8 +/- 2.8 years).

MEASUREMENTS

Lean body mass (LBM), fat mass (FM) and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA). Resting energy expenditure (REE) and fat oxidation (Fox) were assessed by indirect calorimetry.

RESULTS

Mean percentage FM was significantly greater by 30% in CS (P = 0.002) and 22% in GH-deficient subjects (P = 0.014) than in normal subjects. LBM was significantly lower by 15% in CS (P = 0.002) and 11% in GHD (P = 0.013). In CS, the proportion of lean tissue in the limbs was 12% less than in normal (P = 0.001) and GH-deficient subjects (P = 0.0005). Truncal fat represented a greater proportion of total FM in CS (52.5 +/- 1.8%vs. 46.9 +/- 1.3%, P = 0.014) than in normal subjects, but not in GHD. REE and Fox, corrected for LBM, were significantly lower in GHD (P < 0.02 for both vs. normal) but not in CS.

CONCLUSION

FM was higher and LBM lower in both CS and GHD. However, there is a greater abnormality of regional body composition in patients with CS who exhibit a lower limb lean mass and a greater truncal fat. Reduced REE and Fox contribute to increased adiposity in GHD. As REE and Fox are not perturbed in CS, other mechanisms must explain the marked gain in truncal and total fat.

Human water needs

Healthy humans regulate daily water balance remarkably well across their lifespan despite changes in biological development and exposure to stressors on hydration status. Acute or chronic body water deficits result when intakes are reduced or losses increase, but day-to-day hydration is generally well maintained so long as food and fluid are readily available. Total water intake includes drinking water, water in beverages, and water in food. Daily water needs determined from fluid balance, water turnover, or consumption studies provide similar values for a given set of conditions. A daily water intake of 3.7 L for adult men and 2.7 L for adult women meets the needs of the vast majority of persons. However, strenuous physical exercise and heat stress can greatly increase daily water needs, and the individual variability between athletes can be substantial.

Hydration assessment techniques

Water in the human body is essential for metabolism, temperature regulation, and numerous other physiological processes that are consistent with good health. Accurate, precise, and reliable methods to assess body fluid compartments are needed. This review describes the hydration assessment techniques of isotope dilution, neutron activation analysis, bioelectrical impedance, body mass change, thirst, tracer appearance, hematologic indices, and urinary markers. It also provides guidance for selecting techniques that are appropriate for use with unique individuals and situations.

Effect of liver cirrhosis on body composition: evidence of significant depletion even in mild disease

BACKGROUND AND AIMS

Malnutrition is common in liver cirrhosis patients. However, it is under-diagnosed because liver disease affects the traditional nutritional assessment. An understanding of changes in body composition and the establishment of the tissue-loss pattern in liver cirrhosis patients could help practitioners to better manage malnutrition in this setting. The aims of this study were: to quantify body composition changes, to determine tissue loss pattern, and to assess the relation of these to the severity of hepatic dysfunction.

METHODS

Seventy-nine patients and 17 controls were studied. Total body water and extracellular water were measured using dilution techniques. Intracellular water and body cell mass were calculated from these parameters. Total body fat was obtained using absorptiometry.

RESULTS

Extracellular water was increased and intracellular water was decreased in patients. The two major compartments (body cell mass and body fat) were significantly reduced, mainly in patients with moderate and severe disease. However, significant losses occurred even in Child-Pugh class A patients. We established a tissue-loss pattern. In Child-Pugh class A patients body fat loss predominated. Child-Pugh class B patients had losses in at least one of the two compartments. Most Child-Pugh class C patients had simultaneous depletion in both compartments.

CONCLUSIONS

Liver cirrhosis was characterized by a significant reduction in body cell mass and body fat and by a redistribution of body water. Significant losses occurred even in patients with mild disease. There was a more pronounced loss of fat in the initial stages, followed by an accelerated loss of body cell mass in the advanced stages of liver cirrhosis.

Assessment of volume depletion in children with malaria

BACKGROUND

The degree of volume depletion in severe malaria is currently unknown, although knowledge of fluid compartment volumes can guide therapy. To assist management of severely ill children, and to test the hypothesis that volume changes in fluid compartments reflect disease severity, we measured body compartment volumes in Gabonese children with malaria.

METHODS AND FINDINGS

Total body water volume (TBW) and extracellular water volume (ECW) were estimated in children with severe or moderate malaria and in convalescence by tracer dilution with heavy water and bromide, respectively. Intracellular water volume (ICW) was derived from these parameters. Bioelectrical impedance analysis estimates of TBW and ECW were calibrated against dilution methods, and bioelectrical impedance analysis measurements were taken daily until discharge. Sixteen children had severe and 19 moderate malaria. Severe childhood malaria was associated with depletion of TBW (mean [SD] of 37 [33] ml/kg, or 6.7% [6.0%]) relative to measurement at discharge. This is defined as mild dehydration in other conditions. ECW measurements were normal on admission in children with severe malaria and did not rise in the first few days of admission. Volumes in different compartments (TBW, ECW, and ICW) were not related to hyperlactataemia or other clinical and laboratory markers of disease severity. Moderate malaria was not associated with a depletion of TBW.

CONCLUSIONS

Significant hypovolaemia does not exacerbate complications of severe or moderate malaria. As rapid rehydration of children with malaria may have risks, we suggest that fluid replacement regimens should aim to correct fluid losses over 12-24 h.

Hydration Testing in Collegiate Wrestlers Undergoing Hypertonic Dehydration

Because dehydration (DEH) violates assumptions used in the assessment of body composition, hydration testing has become an integral part of minimal weight (MW) assessment.

PURPOSE

To determine the accuracy of hydration tests for the detection and quantification of hypertonic DEH.

METHODS

Twenty-five male collegiate wrestlers (mean +/- SD, age: 20.0 +/- 1.4 yr, height: 175.0 +/- 7.1 cm, body mass: 81.7 +/- 15.3 kg) had their hydration assessed under well-controlled conditions of euhydration (EUH) and DEH. The DEH phase occurred on the same day as EUH, after subjects acutely dehydrated 2-6% of body weight through fluid/food restriction and exercise in a hot environment.

RESULTS

All hydration tests except plasma potassium significantly increased from EUH to DEH, and meaningful cutoff values could be established for most tests. Cutoff values for urine tests were 586 mOsm.L(-1) for osmolality and 71 mEq.L(-1) for potassium. Plasma cutoff values were 293 mOsm.L(-1) for osmolality, 140 mEq.L(-1) for sodium, 103 mEq.L(-1) for chloride, and 3.5 pg.mL(-1) for arginine vasopressin. For ratio tests, a urine:plasma osmolality of 2.06 and an extracellular:intracellular water of 0.533 measured by the bioelectrical impedance spectroscopy were cutoff values. For urine specific gravity, a cutoff value of 1.020 g.mL(-1) had a sensitivity and specificity of 96% each for the automated harmonic oscillation technique and 87% and 91% (respectively) for the dipstick technique. Protein (by dipstick) was detected in 5% of subjects in EUH, and 100% of subjects in DEH. Correlations between hydration tests and dehydration were only low to moderate.

CONCLUSION

This study supports a specific gravity cutoff of 1.020 g.mL(-1) for the identification of hypertonic DEH. Future research should test the cutoff values established in this study and explore the relationship between DEH and urine protein.

The Effect of Dehydration on Wrestling Minimum Weight Assessment

Given that some wrestlers arrive for minimum weight (MW) testing in a dehydrated condition, it is important to understand the effects of dehydration on MW assessment methods.

PURPOSE

To determine the effect of dehydration on the assessment of MW by three-site skinfolds with the Lohman formula (SF), leg-to-leg bioelectrical impedance analysis (BIA), and multifrequency bioelectrical impedance spectroscopy (BIS) compared with a four-component (4C) criterion.

METHODS

Twenty-two male collegiate wrestlers (mean +/- SD, age: 19.9 +/- 1.4 yr, height: 174.0 +/- 6.8 cm, body mass: 77.4 +/- 9.1 kg) had their body composition assessed by the 4C criterion, hydrostatic weighing (HW), SF, BIA, and BIS in euhydration (EUH) and dehydration (DEH). Subjects dehydrated 2-5% of body weight through fluid restriction and exercise in a hot environment.

RESULTS

In EUH, the total error (TE) for HW (1.75 kg) and SF (2.15 kg) were not significantly different, but the TE for HW and SF methods were significantly lower than the TE for both BIS (3.68 kg) and BIA (3.77 kg). In DEH, SF, BIA, and BIS methods had a TE approaching or exceeding 4 kg (8.8 lb). Dehydration increased the TE for SF and BIA through an artificial lowering of body weight and for BIS by an increased error in intracellular water prediction.

CONCLUSION

Acute thermal dehydration violates assumptions necessary for the accurate and precise prediction of MW by SF, leg-to-leg BIA, and multifrequency BIS.

Measurement of nutritional status in simulated microgravity by bioelectrical impedance spectroscopy

The potential of bioelectrical impedance spectroscopy (BIS) for assessing nutritional status in spaceflight was tested in two head-down-tilt bed-rest studies. BIS-predicted extracellular water (ECW), intracellular water (ICW), and total body water (TBW) measured using knee-elbow electrode placement were compared with deuterium and bromide dilution (DIL) volumes in healthy, 19- to 45-yr-old subjects. BIS was accurate during 44 h of head-down tilt with mean differences (BIS - DIL) of 0-0.1 kg for ECW, 0.3-0.5 for ICW, and 0.4-0.6 kg for TBW (n = 28). At 44 h, BIS followed the within-individual change in body water compartments with a relative prediction error (standard error of the estimate/baseline volume) of 2.0-3.6% of water space. In the second study, BIS did not detect an acute decrease (-1.41 +/- 0.91 kg) in ICW secondary to 48 h of a protein-free, 800 kcal/day diet (n = 18). BIS's insensitivity to ICW losses may be because they were predominantly (65%) localized to the trunk and/or because there was a general failure of BIS to measure ICW independently of ECW and TBW. BIS may have potential for measuring nutritional status during spaceflight, but its limitations in precision and insensitivity to acute ICW changes warrant further validation studies.

Effect of icodextrin on volume status, blood pressure and echocardiographic parameters: a randomized study

Overhydration is a risk factor for hypertension and left ventricular hypertrophy in peritoneal dialysis patients. Recently, a high prevalence of subclinical overhydration was observed in peritoneal dialysis patients. Aim of the present open-label randomized study was to assess the effect of a icodextrin 7.5% solution on fluid status [extracellular water (ECW) bromide dilution], blood pressure regulation (24-hour ambulatory measurements) and echocardiographic parameters during a study period of 4 months, and to relate the effect to peritoneal membrane characteristics (dialysate/plasma creatinine ratio). Forty peritoneal dialysis patients (22 treated with icodextrin, 18 controls) were randomized to either treatment with icodextrin during the long dwell or standard glucose solutions. Thirty-two patients (19 treated with icodextrin, 13 controls] completed the study. The use of icodextrin resulted in a significant increase in daily ultrafiltration volume (744 +/- 767 mL vs. 1670 +/- 1038 mL; P = 0.012) and a decrease in ECW (17.5 +/- 5.2 L vs. 15.8 +/- 3.8 L; P = 0.035). Also the change in ECW between controls and patients treated with icodextrin was significant (-1.7 +/- 3.3 L vs. +0.9 +/- 2.2 L; P = 0.013). The effect of icodextrin on ECW was not related to peritoneal membrane characteristics, but significantly related to the fluid state of the patients (ECW:height) (r = -0.72; P < 0.0001). Left ventricular mass (LVM) decreased significantly in the icodextrin-treated group (241 +/- 53 grams vs. 228 +/- 42 grams; P = 0.03), but not in the control group. In this randomized open-label study, the use of icodextrin resulted in a significant reduction in ECW and LVM. The effect of icodextrin on ECW was not related to peritoneal membrane characteristics, but was related to the initial fluid state of the patient.

Sodium bromide by instrumental neutron activation analysis quantifies change in extracellular water space with wound closure in severely burned children

BACKGROUND

The ability to measure extracellular water (ECW) in critically ill patients can significantly enhance current methods of assessing fluid homeostasis, body composition, and response to nutritional therapy. We measured corrected bromide space to determine change in ECW with wound closure among acutely burned children.

METHODS

Fifteen children with burns over 30% of their total body surface area had their ECW determined following hemodynamic stabilization and when wound closure was complete. Plasma samples were obtained at baseline and 4 hours after receiving 25 mg/kg of sodium bromide. Plasma bromide was quantified by instrumental neutron activation analysis.

RESULTS

Mean CBS decreased with wound closure (9.1 +/- 4.1 vs 7.9 +/- 3.9 liters; P =.04), indicating a significant decrease in ECW over the course of recovery. A decline in weight also occurred over the same period (32.4 +/- 15.2 vs 29.1 +/- 13.5 kg; P =.007); however, change in corrected bromide space as a proportion of weight was not statistically significant.

CONCLUSION

A significant decrease in ECW accompanies the weight loss observed in patients following wound closure. Measurement of bromide dilution space is a convenient method for monitoring ECW that can be done at the bedside.

Fluid status in CAPD patients is related to peritoneal transport and residual renal function: evidence from a longitudinal study

BACKGROUND

Both peritoneal transport characteristics as well as residual renal function are related to outcome in patients treated with continuous ambulatory peritoneal dialysis (CAPD). It has been suggested that part of this relationship might be explained by an effect of both parameters on the fluid state in CAPD patients or by the relationship between inflammation and peritoneal transport.

METHODS

In the present study, the relationship between fluid state [extracellular water (ECW) (sodium bromide); total body water (TBW) (deuterium oxide)] with peritoneal transport characteristics (2.27% glucose dialysate/plasma creatinine [D/P (creat)] ratio), residual renal function (residual glomerular filtration rate [rGFR] by urine collection) and C-reactive protein (CRP) was assessed in 37 CAPD patients in a cross-sectional and longitudinal design, with 25 patients completing the study.

RESULTS

In the cross-sectional part ECW, corrected for height (ECW:height), was inversely related to rGFR (r=-0.40, P=0.016), whereas during the longitudinal part, D/P[creat] was related to the change in ECW (r=0.40, P=0.05). Neither D/P[creat] nor rGFR were related to CRP, whereas a significant relationship was observed between ECW:height and CRP (r=0.58, P=0.0001). Patients were dichotomized according to rGFR (<2 or >2 ml/min). Despite a higher daily peritoneal glucose prescription (216.3+/-60.0 vs 156.5+/-53.0 g/24 h; P=0.004) and peritoneal ultrafiltration volume (1856+/-644 vs 658+/-781 ml/24 h, respectively; P=0.0001), the patients with a rGFR <2 ml/min showed a higher ECW:height compared with the group with rGFR >2 ml/min (12.5+/-3.8 vs 9.2+/-2.2 l/m, respectively; P=0.003). Results for TBW were comparable.

CONCLUSION

Fluid state was significantly related to peritoneal transport characteristics and rGFR. The larger ECW:height in CAPD patients with a negligible rGFR existed despite a higher peritoneal ultrafiltration volume and higher peritoneal glucose prescription. These findings raise doubts as to whether fluid state in CAPD patients with a diminished rGFR can be adequately controlled on standard glucose solutions without an additional sodium and fluid restriction. The preliminary finding of a relationship between CRP and fluid state might suggest a relationship between overhydration and inflammation.

Pharmacokinetics and clinical utility of sodium bromide (NaBr) as an estimator of extracellular fluid volume in horses

The purpose of this study was to describe the pharmacokinetics of bromide in horses and to evaluate the corrected bromide space as an indicator of extracellular fluid volume (ECFV) in horses after the administration of a single dose of bromide by intravenous infusion. Sodium bromide (30 mg/kg of body weight, IV) was administered to 6 clinically healthy mares over a period of 3 minutes. Blood samples were collected before infusion and at intervals between 0.5 hours and 53 days after infusion. Mean elimination half-life (harmonic mean) was 126 hours (5.2 days), clearance was 1.4 +/- 0.09 mL/(kg x h), area under the curve was 17,520 +/- 1,100 microg x h/mL. and volume of distribution (steady state) was 0.255 +/- 0.015 L/kg. The mean corrected bromide space was determined from the volume of distribution (steady state) and the serum concentrations of bromide at equilibration. Corrected bromide space, an estimate of ECFV, was 0.218 +/- 0.01 L/kg. The conclusion was made that ECFV of horses can be estimated by measuring bromide concentrations in a preinfusion serum sample and a sample obtained 5 hours after the administration of bromide.

Body composition in patients with an ileostomy and inflammatory bowel disease: validation of bio-electric impedance spectroscopy (BIS)

OBJECTIVE

To validate bio-electric impedance spectroscopy (BIS) by comparison with other methods for determination of body water compartments in stable subjects with an ileostomy and no or minor small bowel resection for inflammatory bowel disease (IBD).

SUBJECTS

Twenty-one subjects were included, age range 36-65 y (female/male=12/9), Crohn's disease (CD), n=14, ulcerative colitis (UC), n=6 and indeterminate colitis (IDC), n=1.

METHODS

Fluid compartments were assessed by the use of three independent methods: BIS, dual-energy X-ray absorptiometry (DXA) and dilution techniques (DIL); tritiated water (total body water, TBW); and bromide (extracellular water, ECW), respectively. Intra-cellular water (ICW) was calculated as TBW-ECW. For comparison TBW was also predicted according to an empirical formula. Differences were analysed using Bland-Altman plots.

RESULTS

The mean TBW values obtained from the impedance measurement differed in the order of -2.21 (DIL) to 1.41 (DXA) in women and -2.01 (DIL) to 2.61 (DXA) in men, from the measured and derived values of total body water. Prediction of TBW gave values that were close to BIS, with a mean difference of -0.31 in male subjects and +0.51 in female subjects. Assessment of ECW revealed that the mean difference between dilution and impedance was less in women than in men (P<0.01).

CONCLUSION

The differences between all methods to assess fluid compartments are pronounced. To further investigate the use of the method in clinical practice for dynamic monitoring of rehydration in ileostomates with acute diarrhoea, repeated measurements together with comparison with weight fluid-balance charts are suggested.

SPONSORSHIP

The study was supported by grants from the Swedish Medical Research Council (17X-03117), Göteborgs Läkarsällskap and IB and A Lundbergs forskningsstiftelse.

Beneficial effects of adenosine triphosphate on nutritional status in advanced lung cancer patients: a randomized clinical trial

PURPOSE

In a randomized clinical trial in patients with advanced non-small-cell lung cancer (NSCLC), infusion with adenosine 5'-triphosphate (ATP) inhibited loss of body weight and quality of life. In the present article, the effects of ATP on body composition, energy intake, and energy expenditure as secondary outcome measures in the same patients are reported.

PATIENTS AND METHODS

Patients with NSCLC, stage IIIB or IV, were randomized to receive either 10 intravenous, 30-hour ATP infusions every 2 to 4 weeks or no ATP. Fat mass (FM), fat-free mass (FFM), and arm muscle area were assessed at 4-week intervals for 28 weeks. Food intake, body cell mass (BCM), and resting energy expenditure (REE) were assessed at 8-week intervals for 16 weeks. Between-group differences were tested for statistical significance by repeated-measures analysis of covariance.

RESULTS

Fifty-eight patients were randomized (28 ATP, 30 control). No change in body composition over the 28-week follow-up period was found in the ATP group, whereas, per 4 weeks, the control group lost 0.6 kg of FM (P =.004), 0.5 kg of FFM (P =.02), 1.8% of arm muscle area (P =.02), and 0.6% of BCM/kg body weight (P =.054) and decreased 568 KJ/d in energy intake (P =.0001). Appetite also remained stable in the ATP group but decreased significantly in the control group (P =.0004). No significant differences in REE between the ATP and control groups were observed.

CONCLUSION

The inhibition of weight loss by ATP infusions in patients with advanced NSCLC is attributed to counteracting the loss of both metabolically active and inactive tissues. These effects are partly ascribed to maintenance of energy intake.

Body composition in Prader-Willi syndrome compared with nonsyndromal obesity: Relationship to physical activity and growth hormone function

OBJECTIVE

To study the relationship of fat mass, extracellular-to-intracellular-water ratio, and bone mineral density with growth hormone function and physical activity in Prader-Willi syndrome.

STUDY DESIGN

There were 17 patients with PWS (10 women, ages 7.5-19.8 years) and 17 obese control patients, matched for gender and bone age. FM and extracellular-to-intracellular-water ratio were measured by bromide-deuterium dilution, BMD by dual-energy x-ray absorptiometry, GH function by fasted serum insulin-like growth factor-I concentration, and physical activity by doubly-labeled water in combination with basal metabolic rate by a ventilated hood.

RESULTS

The PWS group had a similar fat mass, but a lower fat-free mass, whereas the extracellular-to-intracellular-water ratio was higher compared with the control group (0.87 +/- 0.07 l/l and 0.80 +/- 0.06 l/l, respectively [P <.01]). Fat mass was inversely related with PA in the PWS group, whereas IGF-I was positively correlated with FFM, ICW, and BMD of the limbs. BMD tended to be lower in patients with PWS.

CONCLUSIONS

In children and adolescents with PWS, adiposity is associated with a reduced fat-free mass and extracellular-to-intracellular-water ratio is increased. Both findings are related to GH function and physical activity. BMD, especially in the limbs, tends to be reduced in patients with PWS and is related to GH function.

Role of bioimpedance spectroscopy in assessment of body water compartments in hemodialysis patients

Bioimpedance spectroscopy (BIS) has been advocated as a tool to assess fluid status in hemodialysis (HD) patients. However, uncertainty remains about the reliability of BIS in patients with abnormalities in fluid status. Aims of the study are to assess the agreement between total-body water (TBW) and extracellular volume (ECW) measured by BIS and tracer dilution (deuterium oxide [D(2)O] and sodium bromide [NaBr]), the influence of the relative magnitude of water compartments (expressed as TBW(D(2)O) and ECW(NaBr):body weight) on the agreement between BIS and tracer dilution, and the ability of BIS to predict acute changes in fluid status. BIS and tracer dilution techniques were performed in 17 HD patients before a dialysis session. Moreover, the relation between BIS and gravimetric weight changes was assessed during both isolated ultrafiltration and HD. Correlation coefficients between TBW and ECW measured by BIS and tracer dilution were r = 0.71 and r = 0.71, respectively. Mean differences (tracer-BIS) were 6.9 L (limits of agreement, -1.5 to 21.6 L) for TBW and 2.3 L (limits of agreement, -1.7 to 9.7 L) for ECW. There was a significant relationship between the relative magnitude of TBW and ECW compartments and disagreement between BIS and tracer dilution (r = 0.65 and r = 0.77; P < 0.05). During both isolated ultrafiltration and HD, there was a significant relation between gravimetric changes and change in ECW(BIS) (r = 0.83 and r = 0.76; P < 0.05), but not with change in TBW(BIS). In conclusion, agreement between BIS and tracer dilution techniques in the assessment of TBW and ECW in HD patients is unsatisfactory. The discrepancy between BIS and dilution techniques is related to the relative magnitude of body water compartments. Nevertheless, BIS adequately predicted acute changes in ECW during isolated ultrafiltration and HD, in contrast to changes in TBW.

Sulfate production depicts fed-state adaptation to protein restriction in humans

One feature of the adaptation to dietary protein restriction is reduced urea production over the hours after consumption of a test meal of fixed composition. This adaptation is impaired in conventionally treated insulin-dependent diabetes mellitus (Hoffer LJ, Taveroff A, and Schiffrin A. Am J Physiol Endocrinol Metab 272: E59--E67, 1997). We have now tested the response to a test meal containing less protein and included as a main outcome variable the production of sulfate, a specific indicator of sulfur amino acid catabolism. Six normal men consumed a mixed test meal containing 0.25 g protein/kg and 10 kcal/kg while adapted to high (1.5 g x kg(-1) x day(-1)) and low (0.3 g. kg(-1) x day(-1)) protein intakes. They followed the identical protocol twice. Six subjects with insulin-dependent diabetes consumed the test meal while adapted to their customary high-protein diet. Adaptation to protein restriction reproducibly reduced 9-h cumulative postmeal urea N and S production by 22--29% and 49--52%, respectively (both P < 0.05). Similar results were obtained for a postmeal collection period of 6 h. The response of the diabetic subjects was normal. We conclude that reductions in postmeal urea and sulfate production after protein restriction are reproducible and are evident using a postmeal collection period as short as 6 h. Sulfate production effectively depicts fed-state adaptation to protein restriction.

Acute phase response and energy balance in stable human immunodeficiency virus-infected patients: a doubly labeled water study

We sought to assess possible associations of the acute phase response with energy balance as a cause of malnutrition in uncomplicated HIV-infection. Seven stable HIV-infected patients and 7 control subjects were followed for 2 weeks for blood chemistry, body composition, total and resting energy expenditure (TEE, REE), heart rate, energy intake, and physical activity; 6 patients were investigated for interleukin-2 receptor. TEE, REE, energy intake, and anthropometric data in patients and control subjects were very similar. However, physical activity, total body potassium, and bioimpedance phase angle were decreased (1.41 +/- 0.08 vs 1.55 +/- 0.9, 152 +/- 10 g vs 191 +/- 37 g, and 6.4 +/- 0.8 degrees vs 7.1 +/- 0.5 degrees; each P < .05), and mean heart rate, fibrinogen, and erythrocyte sedimentation rate were increased in HIV-infected patients (84 +/- 6 bpm vs 76 +/- 8 bpm, 4.3 +/- 1.2 g/L vs 2.5 +/- 0.4 g/L, and 21 +/- 13 mm vs 2 +/- 3 mm; P < .05). The deviation between the measured and the predicted REE in the patient group correlated positively with heart rate and serum interleukin-2 receptor concentrations (r = 0.83 and r = 0.91; P < .05). Possible increases in REE caused by an ongoing acute phase response may be counterbalanced by reduced physical activity that results in normal TEE in HIV infection.