Supplementary Material for: Effect of Lowering Dialysate Flow Rate on Dialysis Dose and Laboratory Values

Background: The rationale behind using higher dialysate flow rates stems from the idea of maximizing a dialysis membrane’s extraction ratio. Subsequent developments in dialysis membrane design, including the hollow fiber undulations, spacer yarns, and altering the fiber packing density helped reduce blood and dialysate flow mismatch in dialysis membranes. Methods: Single-center retrospective analysis of in-center dialysis patients. Adult (age ≥18 years) in-center hemodialysis patients who were receiving dialysis at the centers 3 months prior to and 3 months following the change in dialysate flow rates were included in the study (December 2022 to May 2023). Dialysate flow rates were reduced from 800 to 600ml/min – using the same access and dialysis membrane. Results: 68 patients were enrolled in the study. The change of dialysate flow rate did not result in a statistically significant change in dialysis adequacy (Kt/Vurea). All regression coefficients were below 0.05 (i.e. a 0.05 change in dialysis adequacy for flow rate 600 vs 800ml/min). Significant associations were found between dialysis adequacy and both the blood flow rate and dialysate sodium, but these were also clinically negligible differences. Analysis of patients’ laboratory testing showed no statistically significant difference in serum electrolyte values (sodium, potassium, bicarbonate, blood urea nitrogen and creatinine) Conclusion: In patients treated using the same dialysate filter and dialysis access, changing the dialysate flow rate from 800 to 600ml/min does not result in clinically significant changes in either patients’ measured serum electrolytes or dialysis adequacy.