New method of evaluating sublethal damage to erythrocytes by blood pumps

We recently proposed a new concept, the total destruction time of erythrocytes, to indicate sublethal damage to erythrocytes by blood pumps. In this article, results of additional experiments concerning this new concept are reported. Five paired in vitro hemolysis tests with bovine blood were conducted using a cone-type centrifugal pump (Group A) and an impeller-type pump (Group B). A total pressure head of 100 mm Hg was applied. The factors evaluated were the normalized index of hemolysis and the total destruction time, or the pumping duration, required to raise the level of the plasma-free hemoglobin to 50% of the total hemoglobin. The morphologic change of the erythrocytes also was analyzed. The percentage of crenated cells was calculated from blood smear specimens 1 min after starting the pumps and 2 h before the total destruction time of Group A in each experiment. Although there was no statistical difference in the normalized index of hemolysis between the two groups, the total destruction time of Group A erythrocytes was significantly shorter than that of Group B (18.9 +/- 4.5 h and 33.7 +/- 9.9 h in Group A and Group B, respectively; p < 0.02). The rate of crenated erythrocytes was higher in Group A than in Group B at a point 2 h before the total destruction time of Group A. The total destruction time values seem to define a good method for establishing sublethal traumatic damage to erythrocytes in blood pumps.