Assessing fluid change in hemodialysis: Whole body versus sum of segmentalbioimpedance spectroscopy

Background. Accurate estimation of extracellular fluid (ECF) is an importan t factor in assessing dry weight in hemodialysis patients. Bioimpedance spe ctroscopy (BIS) is a simple method to determine the compartmental distribut ion of body water in HD patients. Recent studies have shown that sum of seg mental BIS (SBIS) is less affected by the change of body position and may b e more accurate in measuring ECF change than whole body BIS (WBIS). We have compared SBIS and WBIS in estimating change in fluid volume during hemodia lysis. Methods. Twenty-eight patients (male 10, female 18) were studied during the ir regular hemodialysis. ECF changes estimated by both techniques were comp ared with actual weight change during the inter- and intradialytic periods. Results. Both techniques tracked fluid changes that correlated well with fl uid loss during the dialysis run (WBIS, r = 0.75, P < 0.001; SBIS, r = 0.65 , P < 0.001) and fluid gain in the interdialytic period (WBIS, r = 0.73, P < 0.01; SBIS, r = 0.6, P < 0.01). ECF changes estimated by SBIS and WBIS un derestimated weight loss 0.78 +/- 0.01 L and 0.6 +/- 0.01 L, respectively; and underestimated weight gain 0.66 +/- 0.18 L and 0.76 +/- 0.18 L, respect ively. Conclusions. While both WBIS and SBIS can be used to track relative ECF vol ume changes in HD patients, they are not accurate in quantifying changes in ECF volume. More studies are needed to evaluate the benefit of SBIS over W BIS in clinical practice.