Chloride removal and bicarbonate replacement by isotonic sodium bicarbonate-based continuous hemodiafiltration: a novel method to correct severe metabolic acidosis.

Background: Previous reports highlighted the efficacy of hemofiltration utilizing isotonic sodium bicarbonate solution as replacement fluid for severe metabolic acidosis. This approach corrects metabolic acidosis by eliminating chloride and supplementing bicarbonate. Here, we present the results of an in vitro study aimed at determining the effect of Isotonic sodium bicarbonate-based Continuous HemoDiafiltration (IBB-CHDF).

Methods: Conventional Continuous HemoDiaFiltration (CHDF) and IBB-CHDF utilized aqueous solutions mimicking blood's electrolyte composition. To assess the efficacy and safety, we compared serial changes in pH, HCO₃^-, Na⁺, and K⁺ concentrations. Blood flow rate was 100 mL/min, and the dialysis fluid flow rate maintained 1.0 L/h for both CHDF and IBB-CHDF. Replacement flow rates ranged from 0.5 to 1.5 L/h for CHDF and 0.1 to 1.5 L/h for IBB-CHDF.

Results: At a replacement flow rate of 0.5 L/h with IBB-CHDF, bicarbonate increased from 14.7 mEq/L to within the physiological range (25.9 mEq/L), whereas in conventional CHDF, the post-treatment bicarbonate concentration did not increase (16.5 mEq/L). The maximum bicarbonate concentration achieved was 22.0 mEq/L at a replacement flow rate of 1.5 L/h in conventional CHDF. Notably, in IBB-CHDF, the sodium concentration remained constant at 150 mEq/L, 10 mEq/L higher than conventional CHDF, and did not escalate despite increasing the replacement flow rate.

Conclusion: IBB-CHDF effectively corrects metabolic acidosis without inducing sodium and water overload by eliminating excess chloride while providing bicarbonate.