Association of bioimpedance spectroscopy-based volume estimation with postdialysis hypotension in patients receiving hemodialysis

Clinical examination to determine the dry weight of patients on hemodialysis (HD) has been problematic, with studies showing discordance between physician assessment and objective measures of volume status.We studied the association between predialysis bioimpedance spectroscopy (BIS)-based estimates of fluid overload and postdialysis hypotension in 635 patients in the United States Renal Data System ACTIVE/ADIPOSE (A Cohort study To Investigate the Value of Exercise/Analyses Designed to Investigate the Paradox of Obesity and Survival in ESRD) study receiving HD in 2009-2011. We recorded predialysis and postdialysis weight and blood pressures over 3 consecutive HD sessions and performed BIS before a single session. Using a previously reported method of estimating normohydration weight, we estimated postdialysis fluid overload (FO_post) in liters. We used logistic regression with extracellular water/total body water (ECW/TBW) or estimated FO_post as the primary predictor and 1 or more postdialysis systolic blood pressures less than 110mmHg as the dependent variable. Models were adjusted for age, sex, race, ultrafiltration rate per kilogram of body weight, end-stage renal disease vintage, diabetes mellitus, heart failure, and albumin. Higher ECW/TBW was associated with lower odds of postdialysis hypotension (odds ratio [OR] 0.35, 95% confidence interval [CI] 0.15-0.84 per 0.1, P=0.02). Every liter of FO_post was associated with lower adjusted odds of postdialysis hypotension (OR 0.86, 95% CI 0.79-0.95, P=0.003). Prospective studies are needed to determine whether this application of BIS could improve current clinical efforts to minimize episodes of postdialysis hypotension without leading to volume overload.