Alkalemic conditions result in blood clotting in the circuit soon after initiating cardiopulmonary bypass

Abstract

Purpose : This study investigated the relationship between blood clotting in the circuit soon after initiating cardiopulmonary bypass (CPB) and echinocytes that appear with alkalemia, using a recirculation circuit filled with heparinized bovine blood.Methods : Alkalemic conditions in the recirculation circuit were prepared by adding various concentrations of NaHCO 3 to the priming fluid. Albumin was also added to confirm its inhibitory effect on blood clotting. Blood pH, hold-up, the pressure gradient, and red blood cell (RBC) reduction rate were monitored. Blood clots were examined microscopically.Results : Although blood pH was elevated under all experimental conditions, clotting in the circuit increased with increased concentrations of HCO3 -. Albumin inhibited the clotting under the same alkalemic conditions. Microscopic findings revealed echinocytes in the blood clots.Conclusions : The shape of echinocytes was transformed by a reduction in the Donnan equilibrium ratio because of changes in pH inside and outside the RBC membrane. Blood clotting in the circuit soon after initiating CPB may be caused by echinocytes that appear under alkalemic conditions. This was inhibited by albumin, suggesting that the addition of albumin to the priming fluid may prevent such clotting in the circuit after initiating CPB.