CONTINUOUS INTRADIALYTIC CALF BIOIMPEDANCE SPECTROS-COPY CAN DETECT ADMINISTRATION OF SMALL AMOUNTS OF NORMAL SALINE IN HEMODIALYISIS PATIENTS

Abstract

Purpose: Changes in ECW are reflected in changes in extracellular resistance (Re) measured by bioimpedance (BIA). The sensitivity of calf (BIA) to detect the administration of small amounts of normal saline in hemodialysis patients was examined. Methods: Calf extracellular (Re) and intracellular resistance (Ri) and cell membrane capacitance (Cm) were measured with the Xitron 4000 device. 4 electrodes were placed 10 cm apart on the calf for the duration of hemodialysis treatments during which patients received normal saline boluses of 150–250 cc. for hypotension or symptoms. We calculated the ratio of Re at time 0 (RO) to the Re at time t (Re) and plotted this ratio (RO Rt) against time. Using the student t test, we then compared the RO2 Rt prior to the administration of saline to the peak change detected within 30 mins. Results: we examined 100 BIA recordings and found 8 patients who had hypotension requiring the administration of saline. The mean change in RO Rt was 2.77%±3.0 %. This change was statistically significant (p = 0.03). All patients showed an increase in blood volume (p=0.008). The changes in absolute Re, Ri, Cm and the ratio of Cm and Ri to the initial values were not significant. Conclusion: Continuous intradialytic calf BIA is sensitive to even the small changes in extracellular resistance caused by the infusion of 150–250cc of normal saline. This supports the growing data that calf bioimpedance will he a useful tool to evaluate fluid status in hemodialysis patients.