The goal of this study was to compare the adequacy of single and multifrequency bioimpedance analysis (BIA) to evaluate body water compartments, body composition, and nutritional status in maintenance hemodialysis patients.
Patients and Methods
Nineteen patients (12 male, 7 female), ages 28 to 82 years (mean, 58.9), treated with maintenance hemodialysis (MHD) for 0.5 to 15 years (mean, 7.3).
Total body water (TBW), extracellular water (ECW), fat-free mass (FFM), and body cell mass (BCM) volumes were estimated with single-frequency (sf BIA) and multifrequency (mf BIA) plethysmographs before and after a midweek dialytic session. Predialysis TBW also was estimated from anthropometric data (eTBW). Serum albumin, prealbumin and myoglobin, and creatinine index were determined as indicators of nutritional status and muscle mass.
Sf BIA and mf BIA gave similar results for TBW volumes. A high linear correlation was also found between eTBW values and both sf TBW and mf TBW; however, a statistically significant difference was found between e TBW and sf and mf TBW. Sf BIA and mf BIA gave quite different results for ECW, when measured predialysis (Figura 1).
The results obtained for FFM indicate a poor agreement between sf and mf BIA. The agreement was better when FFM was measured postdialysis.
The values of BCM, either measured predialysis or postdialysis, indicate a significant difference between sf and mf BIA. BCM estimated with mf BIA had a closer correlation with creatinine index than sf BIA. mf BCM had also a higher correlation with serum myoglobin, which is produced by muscle cells.
TBW can be estimated with enough confidence from either sf or mf BIA at any time. On the contrary, the results of ECW are significantly different with sf and mf BIA when measured predialysis. Thus, it seems more convenient to perform BIA after dialysis, in particular when assessing the “ideal” body weight.