DETERMINATION OF DRY WEIGHT IN HEMODIALYSIS PATIENTS BY MONITORING CHANGES IN THE SLOPE OF EXTRACELLULAR VOLUME (ECV) DURING DIALYSIS

Abstract

Correct estimation of dry weight in hemodialysis (HD) patients is imprecise. Since leg is more hydrated than other body segments, monitoring ECV changes in leg could determine if patients achieve dry weight. We hypothesize that if change in the slope of ΔECV (ΔECV = ECV/ECV0) approach zero at the end of HD, patients have achieved dry weight. Measurement of electrical resistivity ρ = R.A/L [ohm cm) in leg provides a quantitative measure for comparison to normal hydration in controls. Ten HD patients (3f/7m, age 56±8 years), were studied twice at different post dialysis body weight in one week. Relative change in ECV in leg was continuously measured during HD by Xitron 40006. The % change in ΔECV (ΔECV20) during the last 20 min of HD was used to indicate fluid status of legs. Resistivity was measured at the beginning and end of HD sessions. * P < 0.05 vs Dry Weight. Resistivity was significantly greater and mean arterial blood pressure (MAP) was significantly less before HD when dry weight was attained in these patients, with a decrease of about 1.8 kg body weight. In the period when dry weight was not achieved, resistivity was significantly less than controls (591±89) (P < 0.05). The slope of ΔECV20 during last 20 min. was significantly less when dry weight was achieved. Monitoring changes in slope and resistivity could become a reliable and accurate method to establish dry weight during HD.Table