HEMODIALYSIS UREA REBOUND AND MEMBRANE BIOCOMPATIBILITY - ACCURACY OFKT V ESTIMATIONS/

To date, the magnitude, causes, and factors that govern urea rebound a re not clearly defined. This study was undertaken to determine the pos sible influence of the biocompatibility of dialyzer membrane on urea r ebound and to assess the participation of rebound in the calculation o f Kt/V-urea by different methods. Blood urea samples were obtained bef ore, and at 2, 30, and 60 min posthemodialysis in 8 patients undergoin g dialysis with 2 different membranes, Cuprophan and polyacrylonitrile (24 sessions with each membrane). Urea rebound was documented in all patients. The degree of rebound was large, 20%, and it was achieved wi thin 30 min after the end of dialysis. Urea rebound was observed with both Cuprophan and polyacrylonitrile membranes, without significant di fferences. Kt/V-urea significantly decreased (p < 0.001) by all method s when urea rebound was incorporated. We conclude that urea rebound is clinically very important and is not influenced by the biocompatibili ty of the dialyzer membrane. This phenomenon must be taken into accoun t in the calculation of Kt/V; otherwise, it might be overestimated.