Extracorporeal Chloride Removal by Electrodialysis A Novel Approach to Correct Acidemia

Rationale: Acidemia is a severe condition among critically ill patients. Despite lack of evidence, sodium bicarbonate is frequently used to correct pH; however, its administration is burdened by several side effects. We hypothesized that the reduction of plasma chloride concentration could be an alternative strategy to correct acidemia. Objectives: To evaluate feasibility, safety, and effectiveness of a novel strategy to correct acidemia through extracorporeal chloride removal by electrodialysis. Methods: Ten swine (six treated and four control animals) were sedated, mechanically ventilated and connected to an extracorporeal electrodialysis device capable of selectively removing chloride. In random order, an arterial pH of 7.15 was induced either through reduction of ventilation (respiratory acidosis) or through lactic acid infusion (metabolic acidosis). Acidosis was subsequently sustained for 12-14 hours. In treatment pigs, soon after reaching target acidemia, electrodialysis was started to restore pH. Measurements and Main Results: During respiratory acidosis, electrodialysis reduced plasma chloride concentration by 26 +/- 65 mEq/L within 6 hours (final pH = 7.36 +/- 0.04). Control animals exhibited incomplete and slower compensatory response to respiratory acidosis (final pH = 7.29 +/- 0.03; P<0.001). During metabolic acidosis, electrodialysis reduced plasma chloride concentration by 15 +/- 3 mEq/L within 4 hours (final pH = 7.34 +/- 0.07). No effective compensatory response occurred in control animals (final pH = 7.11 +/- 0.08; P<0.001). No complications occurred. Conclusions: We described the first in vivo application of an extracorporeal system targeted to correct severe acidemia by lowering plasma chloride concentration. Extracorporeal chloride removal by electrodialysis proved to be feasible, safe, and effective. Further studies are warranted to assess its performance in the presence of impaired respiratory and renal functions.