VALIDATION OF CHANGES IN EXTRACELLULAR VOLUME MEASURED DURING HEMODIALYSIS USING A SEGMENTAL BIOIMPEDANCE TECHNIQUE

Sum of segmental bioimpedance analysis (BIA(S)) has recently been intr oduced as a more accurate estimation of extracellular volume (ECV). Th e current study was designed to compare the changes in ECV estimated b y whole body bioimpedance (BIA(W)) and BIA(S) and to determine whether BIA(S) could be used to accurately estimate changes in ECV compared w ith the ultrafiltration volume (UFV) as measured by the dialysis machi ne. Ten men (age, 49 +/- 10 years; dry weight, 78 +/- 13 kg) were stud ied during hemodialysis (HD). A multifrequency bioimpedance analyzer ( BIS4000B; Xitron Technologies, San Diego, CA) and a digital switch dev eloped by the authors were used to automatically collect data from thr ee body segments (arm, trunk, and leg) and the whole body using the st ated technique. There was a significant difference in Delta ECVw and U FV at the end of the treatment (2.75 +/- 0.74 L vs 3.95 +/- 0.73 L, p < 0.05) because fluid removal from the trunk has almost no effect on w hole body resistance. However, Delta ECVS was not significantly differ ent from UFV(3.76 +/- 0.65 L vs 3.95 +/- 0.73 L, p = NS). BIA(S) is a more accurate approach to monitor changes in ECV during HD than is BIA (W) because changes in local resistance can be allocated to segments w ith uniform geometry and resistivity. This is a prerequisite for futur e studies on dynamics of regional fluid distribution during hemodialys is.