Indirect Measures of Total Body Water May Confound Precise Assessment of Peritoneal Dialysis Adequacy

Urea kinetic modeling (UKM) has yet to be optimized as a practical tool for assessing adequacy of therapy In continuous ambulatory peritoneal dialysis (CAPO) patients. Watson equation (WV) and 58% body weight (58%WT) estimates of total body water (TBW) are Indirect measures likely to yield Imprecise estimates of Kt/V. Bioelectrical Impedance (BEl) measures body composition as a function of electrical conductance, minimizing fat contribution to TBW. TBW values were highest when measured as 58%WT and lowest when calculated from WV. These differences were most striking In patients with overweight body habitus. BEI-derived TBW correlated best with UKM values. The relationship between BEI-derived and anthropometrically derived TBW was best In patients of normal habitus. Kt/V values were highest when calculated from WV-derived volumes and significantly differed from Kt/V values calculated from BEI-derived and 58%WT volumes. When segregated by habitus, however, only In overweight patients was this pattern of clinical significance. Serial body weight, lean body mass, and TBW remained stable In patients of normal habitus. Overweight patients increased weight by 5%, lean mass by 2%, and TBW by 5%, 3%, and 2% when measured by 58%WT, WV, and BEl, respectively. BEl measures of TBW exclude fat mass and thus strengthen the use of Kt/V for assessing dialysis adequacy In CAPO patients of all body weights.

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Total body water and body composition in chronic peritoneal dialysis patients.

Journal of the American Society of Nephrology ◽

10.1681/asn.v8121906 ◽

1997 ◽

Vol 8 (12) ◽

pp. 1906-1914 ◽

Cited By ~ 1

Author(s):

W Arkouche ◽

D Fouque ◽

C Pachiaudi ◽

S Normand ◽

M Laville ◽

...

Keyword(s):

Peritoneal Dialysis ◽

Total Body Water ◽

Resting Metabolic Rate ◽

Bioelectrical Impedance ◽

Skinfold Thickness ◽

Body Water ◽

Fat Free Mass ◽

Chronic Peritoneal Dialysis ◽

Dialysis Patients ◽

Total Body

In this investigation, total body water (TBW) in ten chronic peritoneal dialysis patients was studied by deuterium (TBW-2H), skinfold thickness (TBW-ST), Watson formula (TBW-WA), 58% of body weight (TBW-58%), and bioelectrical impedance (TBW-BIA), and these results were compared with the reference oxygen18 (TBW-18O) method. We also analyzed the fat-free mass (FFM) by skinfold thickness (FFM-ST), bioelectrical impedance (FFM-BIA), oxygen18 (FFM-18O), and creatinine kinetics method (FFM-CK). In addition, resting metabolic rate was measured by indirect calorimetry. Compared with TBW-18O, TBW-58% and TBW-BIA were significantly different (P < 0.01). TBW-2H overestimated TBW-18O by 4.3%. TBW-ST and TBW-WA gave slightly greater values than TBW-18O, although these values were nonstatistically significant. The best prediction of total body water from these methods was obtained with the Watson formula. When Kt/V was calculated from these results, the values obtained were statistically greater (BIA, P < 0.001) and smaller (58% BW, P < 0.01) than those obtained with either 18O or Watson formula. The fat-free mass estimation also led to discrepant findings. Indeed, FFM-CK was significantly lower (P < 0.05) as compared with FFM-ST, FFM-BIA, or FFM-18O. Resting metabolic rate was strongly correlated with FFM estimated by skinfold thickness (r = 0.91, P < 0.001), bioelectrical impedance (r = 0.85, P < 0.005), and 18O (r = 0.77, P < 0.01), but not when fat-free mass was estimated by the creatinine kinetic method. The water content of fat-free mass estimated by skinfold thickness was found to be 69.7 +/- 6.9% in these patients, a value lower than the standard 73.2% found in healthy adults. This study confirms that there is an abnormal water distribution in chronic peritoneal dialysis patients. However, when compared with the oxygen18 reference method, the Watson formula allows a reliable estimation of Kt/V.

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Effects of a 14-Day Hydration Intervention on Individuals with Habitually Low Fluid Intake

Annals of Nutrition and Metabolism ◽

10.1159/000515375 ◽

2021 ◽

Author(s):

Aaron R. Caldwell ◽

Megan E. Rosa-Caldwell ◽

Carson Keeter ◽

Evan C. Johnson ◽

François Péronnet ◽

...

Keyword(s):

Body Weight ◽

Total Body Water ◽

Fluid Intake ◽

Urine Volume ◽

Urine Osmolality ◽

Body Water ◽

Control Group ◽

Intervention Phase ◽

Total Body ◽

Experimental Group

Background: Debate continues over whether or not individuals with low total water intake (TWI) are in a chronic fluid deficit (i.e., low total body water) [<xref ref-type="bibr" rid="ref1">1</xref>]. When women with habitually low TWI (1.6 ± 0.5 L/day) increased their fluid intake (3.5 ± 0.1 L/day) for 4 days 24-h urine osmolality decreased, but there was no change in body weight, a proxy for total body water (TBW) [<xref ref-type="bibr" rid="ref2">2</xref>]. In a small (n = 5) study of adult men, there were no observable changes in TBW, as measured by bioelectrical impedance, after increasing TWI for 4 weeks [<xref ref-type="bibr" rid="ref3">3</xref>]. However, body weight increased and salivary osmolality decreased indicating that the study may have been underpowered to detect changes in TBW. Further, no studies to date have measured changes in blood volume (BV) when TWI is increased. Objectives: Therefore, the purpose of this study was to identify individuals with habitually low fluid intake and determine if increasing TWI, for 14 days, resulted in changes in TBW or BV. Methods: In order to identify individuals with low TWI, 889 healthy adults were screened. Participants with a self-reported TWI less than 1.8 L/day (men) or 1.2 L/day (women), and a 24-h urine osmolality greater than 800 mOsm were included in the intervention phase of the study. For the intervention phase, 15 participants were assigned to the experimental group and 8 participants were assigned to the control group. The intervention period lasted for 14 days and consisted of 2 visits to our laboratory: one before the intervention (baseline) and 14 days into the intervention (14-day follow-up). At these visits, BV was measured using a CO-rebreathe procedure and deuterium oxide (D2O) was administered to measure TBW. Urine samples were collected immediately prior, and 3–8 h after the D2O dose to allow for equilibration. Prior to each visit, participants collected 24-h urine to measure 24-h hydration status. After the baseline visit, the experimental group increased their TWI to 3.7 L for males and 2.7 L for females in order to meet the current Institute of Medicine recommendations for TWI. Results: Twenty-four-hour urine osmolality decreased (−438.7 ± 362.1 mOsm; p < 0.001) and urine volume increased (1,526 ± 869 mL; p < 0.001) in the experimental group from baseline, while there were no differences in osmolality (−74.7 ± 572 mOsm; p = 0.45), or urine volume (−32 ± 1,376 mL; p = 0.89) in the control group. However, there were no changes in BV (Fig. <xref ref-type="fig" rid="f01">1</xref>a) or changes in TBW (Fig. <xref ref-type="fig" rid="f01">1</xref>b) in either group. Conclusions: Increasing fluid intake in individuals with habitually low TWI increases 24-h urine volume and decreases urine osmolality but does not result in changes in TBW or BV. These findings are in agreement with previous work indicating that TWI interventions lasting 3 days [<xref ref-type="bibr" rid="ref2">2</xref>] to 4 weeks [<xref ref-type="bibr" rid="ref3">3</xref>] do not result in changes in TBW. Current evidence would suggest that the benefits of increasing TWI are not related changes in TBW.

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Influence of Posture and Frequency Modes in Total Body Water Estimation Using Bioelectrical Impedance Spectroscopy in Boys and Adult Males

Nutrients ◽

10.3390/nu6051886 ◽

2014 ◽

Vol 6 (5) ◽

pp. 1886-1898 ◽

Cited By ~ 4

Author(s):

Masaharu Kagawa ◽

Connie Wishart ◽

Andrew Hills

Keyword(s):

Impedance Spectroscopy ◽

Total Body Water ◽

Bioelectrical Impedance ◽

Body Water ◽

Adult Males ◽

Total Body

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Bipedal bioelectrical impedance analysis reproducibly estimates total body water in hemodialysis patients

American Journal of Kidney Diseases ◽

10.1053/ajkd.2002.29907 ◽

2002 ◽

Vol 39 (1) ◽

pp. 154-158 ◽

Cited By ~ 21

Author(s):

Robert F. Kushner ◽

David M. Roxe

Keyword(s):

Total Body Water ◽

Bioelectrical Impedance Analysis ◽

Bioelectrical Impedance ◽

Impedance Analysis ◽

Hemodialysis Patients ◽

Body Water ◽

Total Body

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Estimation of water content by tritium dilution of animals subjected to rapid live-weight changes

The Journal of Agricultural Science ◽

10.1017/s0021859600020384 ◽

1969 ◽

Vol 72 (1) ◽

pp. 31-40 ◽

Cited By ~ 10

Author(s):

W. R. McManus ◽

R. K. Prichard ◽

Carolyn Baker ◽

M. V. Petruchenia

Keyword(s):

Body Weight ◽

Water Content ◽

Total Body Water ◽

Compensatory Growth ◽

Specific Activity ◽

Tritiated Water ◽

Body Water ◽

Under Nutrition ◽

The Mean ◽

Total Body

SUMMARYThe use of tritiated water to estimate total body-water content of animals experiencing recovery from under-nutrition was studied.The time for equilibration of tritiated water (TOH), given intraperitoneally, with total body water (TBW) was determined in rabbits and in rats. As judged by the specific activity of blood water, equilibration had occurred by 76–125 min in the rabbit and did not appear to be affected by the plane of nutrition. However, between slaughter groups the specific activity of water obtained from the liver 180 min after injection of TOH was significantly different from the specific activity of water simultaneously obtained from the blood plasma. It is concluded that the liver is not a suitable tissue to use for testing achievement of equilibration.As judged by the specific activity of blood water compared to that of water from the whole body macerate, equilibration in mature rats either in stable body condition or undergoing rapid compensatory growth occurred in less than 60 min.A trial comparing TOH-space (corrected by 3% body weight) and actual TBW (by desiccation) was conducted on thirty rabbits which experienced under-nutrition followed by compensatory growth.Prior to under-nutrition the agreement between actual and estimated TBW was satisfactory and within 2·3%. During compensatory growth the agreement was poor— the TOH values over-estimating actual TBW by about 12%.A trial with mature rats confirmed the findings with rabbits. For rats in stable body weight the mean estimated TOH-space for fourteen animals was within 1·2% of the actual TBW. For fourteen rats undergoing compensatory growth the mean estimated TOH-space (corrected by 3% body weight) overestimated actual TBW by 6·2%.

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