HEMODIALYSIS UREA REBOUND - THE EFFECT OF INCREASING DIALYSIS EFFICIENCY

Urea rebound has been documented to occur after hemodialysis, but the magnitude and causes are not clearly defined. In this study we evaluat ed the effect of high-flux hemodialysis on urea rebound and Kt/V. Bloo d urea nitrogen samples were obtained before, immediately after, and 3 0 minutes after hemodialysis in 49 patients. Rebound was evaluated wit h respect to dialysis efficiency, dialysis treatment time, the occurre nce of hypotension, and hematocrit. Urea rebound was significant and r esulted in an overall decrease in Kt/V from 1.2 +/- 0.3 to 1.0 +/- 0.2 (P < 0.001). Of the 45 patients with a measured Kt/V of greater than 1.0, 40% had an actual delivered Kt/V of less than 1.0 once rebound wa s taken into account. Urea rebound correlated strongly with dialysis e fficiency but not with hypotension, suggesting that rebound resulted p rimarily from delayed urea mass transfer across cell membranes. We con clude that increasing dialysis efficiency increases urea rebound and i ncreases the error in Kt/V determinations from single pool urea kineti cs. (C) 1995 by the National Kidney Foundation, Inc.