Effect of Reduced Dialysate Flow on Dialysis Adequacy: A Pilot Study

The standard dialysate flow (Qd) for hemodialysis (HD) is currently set at 500 mL/min. One potential, sustainable, and cost-effective solution for eco-friendly HD may involve reducing Qd to limit wastewater. However, the effect of reduced Qd on small molecule and middle molecule (MM) removal remains to be investigated.

In this prospective observational study, 74 patients on different maintenance dialysis modalities with Qd set at 500 mL/min (Qd500) were assigned to receive Qd at 400 mL/min (Qd400) for 3 months. Dialysis adequacy, including small solute removal and MM reduction ratio (RR), was evaluated at enrollment and after 3 months.

Compared to Qd500, Qd400 after 3 months achieved similar single-pool Kt/V (1.41 ± 0.30 vs. 1.43 ± 0.33, p = 0.58), equilibrated KT/V, urea RR, creatinine RR, and phosphate RR. Qd400 vs. Qd500 provided significantly higher beta2-microglobulin RR (77.0 [71.4-81.7] vs. 74.7 [68.4-79.4] %, p = 0.009) and lower kappa free light chain (FLC) RR (54.2 [42.1-64.4] vs. 57.6 [41.6-65.0] %, p = 0.03), whereas myoglobin and lambda FLC RR were similar. Qd400 resulted in higher pre-dialysis urea (20.2 ± 5.5 vs. 18.2 ± 6.2 mmol/L, p = 0.002), creatinine (694.0 ± 179.5 vs. 665.6 ± 220.4 µmol/L, p = 0.029), beta2-microglobulin (26.5 [23.0-30.0] vs. 23.5 [20.0-28.0] mg/L, p = 0.0001), and myoglobin (174.0 [122.0-251.0] vs. 159.5 [119.0-195.0] µg/L, p = 0.033) levels. Pre-dialysis levels of albumin, potassium, bicarbonate, phosphate, and calcium were similar between Qd400 and Qd500.

Three months of Qd at 400 mL/min appears to provide similar small molecule and MM removal, but with an increase in pre-dialysis urea, creatinine, beta2-microglobulin, and myoglobin levels. Although this strategy could help preserve water, its potential impact on long-term clinical outcomes deserves further evaluation.