Optimizing dialysis dose by increasing blood flow rate in patients with reduced vascular-access flow rate

Dialysis efficacy indexed by Kt/V can generally be augmented by increasing the dialyzer blood flow rate. However, increasing the dialyzer blood flow rate may lead to vascular-access recirculation (AR) in patients with a compromised vascular-access flow rate. This can have an attenuating effect on dialysis efficacy. The aim of the present study is to investigate the effect of dialyzer blood flow rates of 200, 300, and 400 mL/min on AR and Kt/V in 8 patients with low (<600 mL/min) and 13 patients with normal (>600 mL/min) vascular-access flow rates. AR and vascular-access flow rate were determined using an ultrasound saline dilution technique, and session-delivered Kt/V was computed using an on-line dialysate urea monitor. AR was minor and only observed in 4 patients in the low vascular-access flow rate group (0.9% +/- 0.6%) at dialyzer blood flow rates of 200 mL/min (1 patient), 300 mL/min (2 patients), and 400 mL/min (3 patients) and 4 patients in the normal vascular-access flow rate group (1.2% +/- 1.1%) at dialyzer blood flow rates of 200 mL/min (3 patients) and 300 mL/min (1 patient). Kt/V increased with increasing dialyzer blood flow rates in both groups, and in individual cases, there was no decrease in Kt/V at greater dialyzer blood flow rates in either group. Also in those patients with minor AR, Kt/V increased at greater dialyzer blood flow rates, except in 1 patient in the low-flow group, in whom Kt/V remained unchanged at a change in dialyzer blood flow rate from 300 to 400 mL/min, whereas AR increased. From this study, it is concluded that even in patients with low access flow, increasing dialyzer blood flow rate in general leads to an increase in delivered Kt/V regardless of vascular access flow rate.