Filtration-assisted exchange transfusion using alpha alpha Hb, an erythrocyte substitute

A method for improving the efficiency of exchange transfusion to evaluate hemoglobin- (Hb) based erythrocyte substitutes is described. The method uses a continuous-flow hollow-fiber plasma separation filter to remove the erythrocytes while returning 75% of the plasma. The removed volume was replaced with a 14-g/dl solution of human Hb cross-linked between the alpha-chains with bis(3,5-dibromosalicyl)fumarate (alpha alpha Hb). Filtration of 2.76 blood vol in anesthetized swine resulted in a 95% reduction of hematocrit and produced a plasma Hb concentration of 7.63 g/dl. Hyperoncotic Hb solutions cause volume expansion, which reduces the efficiency of exchange but provides hemodynamic stability in the face of decreasing blood viscosity and subsequent intravascular volume loss with Hb redistribution. Filtration-assisted exchange transfusion is rapid, conserves valuable modified Hb, and ensures continuous adequate oxygen delivery.