Erythrocyte filterability and lysosomal enzymes in patients requiring cardiopulmonary bypass

Erythrocyte filterability, an index of deformability, and lysosomal enzyme activity were studied in 34 patients requiring cardiopulmonary bypass. In addition fresh human erythrocytes were analyzed after incubation for filterability changes after exogenous lysosomal enzymes were added to the suspension medium. The results showed statistically significant elevations of the filterability index (decrease in filterability of the red cells) after 10 minutes on cardiopulmonary bypass as well as postoperatively. Likewise cathepsin D concentration after 10 minutes of cardiopulmonary bypass of 8.4 plus or minus 0.8 U. was significantly elevated over the preoperative level of 5.3 plus or minus 0.7 U. Furthermore, the pump prime was found to have the highest filterability index as well as concentration of cathepsin D. Supporting our hypothesis that lysosomal enzymes may be a factor affecting erythrocyte integrity was the elevation of the filtration index to 10.5 plus or minus 0.3 U. during incubation with exogenous lysosomal enzymes compared with the control index of 9.0 plus or minus 0.2 U. This stduy implies that the pump prime should be an area of further investigation if alterations of erythrocyte filterability (deformability) and lysosomal enzymes during extracorporeal circulation are shown to have clinical importance.