RELIABLE ESTIMATION OF DRY WEIGHT IN HAEMODIALYSIS PATIENTS BY THE BIOELECTRICAL IMPEDANCE ANALYSIS

초록

Introduction and Aims: There were significant differences in the slopes of the ultrafiltration (UF) amount removed during haemodialysis (HD) sessions versus the percentage change in the extracellular fluid/total body water ratio for the right lower extremity (ECF/TBWright leg) plot in normohydrated (NH) and overhydrated states. The purpose of this study was to develop and validate a method for predicting dry weight (DW) using these results. Methods: It was hypothesized that for patients to become NH, the slope of the UF amount versus the percentage changes in ECF/TBWright leg plot should be same as that of NH patients and a method for predicting DW was developed. To validate the accuracy of this method, the ECF/TBWright leg was measured by eight-point tactile-electrode bioelectrical impedance analysis before and after HD in 17 newly enrolled NH patients. Using the current DW (cDW) of subjects as a reference, we compared the accuracies of pDW1 (our devised method) and pDW2 (the normovolaemia/hypervolaemia slope method). Results: The mean cDW, pDW1 and pDW2 values were 56.8 ± 7.9, 56.4 ± 7.7 and 56.3 ± 8.0 kg, respectively. No significant differences existed between cDW, pDW1 and pDW2. pDW1 had a lower root mean square error than pDW2 (1.12 vs 1.69). On the Bland–Altman plot, differences between pDW1 and cDW were closer to zero than between pDW2 and cDW. Conclusions: A new method was developed of predicting the DW using the relationship between the UF amount and the percentage change in the ECF/TBW ratio of the lower extremities after HD. The devised method appears to be as accurate as the normovolaemia/hypervolaemia slope method.