Dialysate Flow Rate and Delivered Kt/Vurea for Dialyzers with Enhanced Dialysate Flow Distribution

Background and objectives Previous in vitro and clinical studies showed that the urea mass transfer-area coefficient (KoA) increased with increasing dialysate flow rate. This observation led to increased dialysate flow rates in an attempt to maximize the delivered dose of dialysis (Kt/Vurea). Recently, we showed that urea KoA was independent of dialysate flow rate in the range 500 to 800 ml/min for dialyzers incorporat-ing features to enhance dialysate flow distribution, suggesting that increasing the dialysate flow rate with such dialyzers would not significantly increase delivered Kt/Vurea. Design, setting, participants, & measurements We performed a multi-center randomized clinical trial to com-pare delivered Kt/Vurea at dialysate flow rates of 600 and 800 ml/min in 42 patients. All other aspects of the dialysis prescription, including treatment time, blood flow rate, and dialyzer, were kept constant for a given patient. Delivered single-pool and equilibrated Kt/Vurea were calculated from pre- and postdialysis plasma urea concentrations, and ionic Kt/V was determined from serial measurements of ionic dialysance made throughout each treatment. Results Delivered Kt/Vurea differed between centers; however, the difference in Kt/Vurea between dialysate flow rates of 800 and 600 ml/min was NS by any measure (95 % confidence intervals of 0.064 to 0.024 for single-pool Kt/Vurea, 0.051 to 0.023 for equilibrated Kt/Vurea, and 0.029 to 0.099 for ionic Kt/V). Conclusions These data suggest that increasing the dialysate flow rate beyond 600 ml/min for these dialyz-ers offers no benefit in terms of delivered Kt/Vurea