Regional blood acidification inhibits coagulation during extracorporeal carbon dioxide removal (ECCO₂R)

Background: Consumption of platelets and coagulation factors during extracorporeal carbon dioxide removal (ECCO₂R) increases bleeding complications and associated mortality. Regional infusion of lactic acid enhances ECCO₂R by shifting the chemical equilibrium from bicarbonate to carbon dioxide. Our goal was to test if regional blood acidification during ECCO₂R inhibits platelet function and coagulation. Methods: An ECCO₂R system containing a hemofilter circulated blood at 0.25 L/min in eight healthy ewes (Ovis aries) for 36 h. Three of the sheep received ECCO₂R with no recirculation compared to five sheep that received ECCO₂R plus 12 h of regional blood acidification via the hemofilter, placed upstream from the oxygenator, into which 4.4 M lactic acid was infused. Blood gases, platelet count and function, thromboelastography, coagulation-factor activity, and von Willebrand factor activity (vWF:Ag) were measured at baseline, at start of lactic acid infusion, and after 36 h of extracorporeal circulation. Results: Twelve hours of regional acid infusion significantly inhibited platelet aggregation response to adenosine diphosphate; vWF; and platelet expression of P-selectin compared to control. It also significantly reduced consumption of fibrinogen and of coagulation factors V, VII, IX, compared to control. Conclusions: Regional acidification reduces platelet activation and vitamin-K-dependent coagulation-factor consumption during ECCO₂R. This is the first report of a simple method that may enhance effective anticoagulation for ECCO₂R.