Influence of fluid status on techniques used to assess body composition in peritoneal dialysis patients.

OBJECTIVE: A reliable assessment of nutritional state in peritoneal dialysis (PD) patients is of great importance. Nevertheless, techniques used to assess body composition in patients on PD may be affected by abnormalities in fluid status. The primary aim of the present study was to compare different techniques used to evaluate body composition and to assess the influence of fluid status on the assessment of body composition. The secondary aim was to assess the relevance of handgrip muscle strength in the nutritional evaluation of the patient. METHODS: In 40 PD patients, dual-energy x-ray absorptiometry (DEXA), multifrequency bioimpedance analysis (MF-BIA), and anthropometry were compared with respect to the evaluation of body composition [fat mass and lean body mass (LBM; by DEXA), and fat-free mass (FFM; by MF-BIA, anthropometry]. The influence of fluid status on the measurement of LBM/FFM by the various techniques was assessed by their relation to left ventricular end-diastolic diameter (LVEDD), assessed by echocardiography, and by estimating the ratio between extracellular water (ECW) and total body water (TBW), assessed by bromide and deuterium dilution, with LBM (DEXA). The relevance of handgrip muscle strength as a nutritional parameter was assessed by its relation to LBM and other nutritional parameters. RESULTS: Despite highly significant correlations, wide limits of agreement between the various techniques were present with respect to assessment of body composition (expressed as % body weight) and were most pronounced for anthropometry: LBM (DEXA) - FFM (MF-BIA) = 3.4% +/- 12.2%; LBM (DEXA) - FFM (anthropometry) = -5.7% +/- 7.8%; fat mass (DEXA - MF-BIA) = -4.2% +/- 7.9%; fat mass (DEXA - anthropometry) = 2.9% +/- 7.2%. The ratio between ECW and LBM (DEXA) was 0.36 +/- 0.08 L/kg (range 0.25 - 0.67 L/kg), and the ratio between TBW and LBM was 0.75 +/- 0.06 L/kg (range 0.63 - 0.86 L/kg), which shows the variability in hydration state of LBM/FFM between individual patients. LBM/FFM measured by all three techniques was significantly related to LVEDD, suggesting an important influence of hydration state on this parameter. Handgrip muscle strength was significantly related to LBM/FFM, as measured by all three techniques, but not to other nutritional parameters. CONCLUSION: Wide limits of agreement were found between various techniques used to assess body composition in PD patients. The assessment of body composition was strongly influenced by hydration state. The handgrip test is related to body composition, but not to other nutritional parameters.

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.

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 (sigmaBIA), 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 sigmaBIA], 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. sigmaBIA did not improve the agreement [ECW (NaBr-sigmaBIA): 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 sigmaBIA 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.