Effect of recombinant aprotinin on platelet activation in patients undergoing open heart surgery

The hemostatic effect of recombinant (r)-aprotinin was studied in 41 patients undergoing cardiopulmonary bypass surgery. Flow cytometry was used to measure the expression of glycoprotein 1b (GP1b) and α-granule membrane protein 140 (GMP-140) on platelets. Additional parameters studied were β-thromboglobulin (β-TG), fibrinogen, fibrinopeptide A, plasminogen, platelet count, and the amount of postoperative chest tube drainage. Chest tube drainage was significantly less in the r-aprotinin-treated patients (p < 0.001). The percentage of platelets expressing GMP-140 increased to 9.7% in r-apro- tinin patients and to 12.1 % in controls during the surgery. The difference between both groups was not significant. Both values returned to baseline the next day. GP1b expression decreased in both groups by 33-38% during the surgery and returned to baseline the next day. GP1b expression and the plasma concentrations of fibrinogen, fibrinopeptide A, β-TG, and plasminogen were not different in r-aprotinin and control patients. We conclude that r-aprotinin reduces blood loss during cardiopulmonary bypass surgery, but the primary mechanism is likely not through a protective effect on platelets.