How low can we go with the dialysate flow? A retrospective study on the safety and adequacy of a water-saving dialysis prescription

Abstract

Background: Green nephrology encompasses all initiatives in kidney care that have a positive impact on climate and environment. To prepare the dialysate, at least 120 L of water are needed for one 4-h session with a dialysate flow (Qd) set at 500 mL/min. A lower dialysate flow rate is associated with a significant reduction in the amount of water used. The aim of this study was to check whether change of Qd from 500 mL/min to 300 mL/min has a significant impact on dialysis adequacy.

Methods: The study was a retrospective analysis. Due to administrative issues, a satellite dialysis center reduced their dialysate flow to 300 mL/min for a month. The center then increased Qd to 500 mL/min again. We analyzed laboratory data from 3 months before dialysate flow reduction, in the month with Qd reduced to 300 mL/min, and from 3 months thereafter with Qd set at 500 mL/min.

Results: Twenty-four people were included in the final analysis. There were no significant changes in urea reduction ratio caused by lower rate of Qd [64.50 (61.75-71.00) vs 67.00 (63.00-72.25) vs 69.00 (63.75-72.25), analysis of variance F(2,46) = 0.71, P = .50]. Similarly, hemodialysis adequacy expressed by Kt/V did not differ at any Qd [1.23 (1.12-1.41) vs 1.25 (1.18-1.40) vs 1.35 (1.19-1.48), ANOVA F(2,46) = 2.51, P = .09]. There was a small but statistically significant increase in mean predialysis potassium with lower Qd [potassium = 5.18 (95% confidence interval, 95% CI, 4.96-5.44) vs 5.46 (95% CI 5.23-5.69) vs 5.23 (95% CI 4.99-5.47) mmol/L at Qd = 500, 300 and 500 mL/min, respectively, P = .039].

Conclusion: Reduction in dialysate flow rate to 300 mL/min seems safe and does not cause any short-term negative effects in this small study. Thus, we might be able to achieve a similar therapeutic effect while saving water consumption. Larger, long-term studies incorporating patient-reported outcome measures are needed to confirm the efficacy of this approach.

Keywords: Kt/V; dialysate flow; dialysis adequacy; green nephrology; water.

Graphical Abstract

Figure 1:

(A) Kt/V at different time points with different Qd. (B) Potassium removal rate at different time points with different Qd. (C) Predialysis potassium at different time-points with different Qd. ^*Statistically significant difference.