[Changes in body fluid compartments estimated by multifrequency bioelectric impedance analysis in patients treated by...

Bioimpedance is a simple non-invasive method of assessing body composition. The aim of this study was to investigate the effect of changes in body fluid related to haemodialysis on measured bioimpedance parameters, to determine correlation between bioimpedance data and the volume of ultrafiltratum, and to collect data on alterations of body fluids resulting from a treatment. Measurements were done on 19 patients (mean age 36.7 years) prior to and after haemodialysis. After dialysis we found significantly higher impedance values on each measured frequency (1, 5, 10, 50, 100 kHz) (p < 0.001). An inverse correlation was found between the changes in body weight (x) and resistance at 50 kHz (y): y = 8.4830-2.1850x (r = 0.7167, p < 0.01). Total body water calculated by bioimpedance analysis (BIA) decreased from 38.47 +/- 8.567 litres (56.07%) to 35.06 +/- 8.045 significantly (p < 0.001), and the reduction of extracellular water proved to be also significant [from 15.76 +/- 2.992 litres (22.97%) to 14.06 +/- 2.736 litres (21.17%), p < 0.001]. The relationship between the change in calculated body water (x) and the volume of ultrafiltratum (y) is: y = -0.5590 + 0.5864x (r = 0.4898 p < 0.05), bioimpedance in our study overestimated the fluid loss by 55%. The intradialytical shifts between extra- and intracellular spaces might be responsible for the difference in the two values.