Aprotinin prevents cardiopulmonary bypass-induced platelet dysfunction. A scanning electron microscope study.

Background: Administration of aprotinin during extracorporeal circulation reduces blood loss and improves platelet function.
Methods and Results: To evaluate the protective effect of aprotinin on platelets, 50 patients undergoing cardiopulmonary bypass were randomized before surgery to one of three groups. Seventeen patients (group A) received continuous high-dose aprotinin (7 x 10(6) KIU) during cardiopulmonary bypass, 17 (group B) received a single bolus of aprotinin in the pump prime (2 x 10(6) KIU), and 16 (group C) received placebo. Scanning electron microscopy was used to evaluate platelet aggregation on extracellular matrix. The platelet function was graded from 1 to 4, with grade 4 being normal aggregation. Immediately after cardiopulmonary bypass, 16 patients in group A (94%) reached preoperative aggregation grade (mean grade, 3.4 +/- 0.7) compared with nine of 17 in group B (52%) (mean grade, 2.9 +/- 1.2), and none in group C (0%) (mean grade, 1.4 +/- 0.5; p < 0.001). Postoperative platelet count did not differ significantly among the three groups. After surgery, group A bled less than groups B and C (395 +/- 120 versus 488 +/- 135 and 780 +/- 408 ml, respectively; p < 0.01). Patients in the aprotinin groups received fewer red blood cell units (0.9 +/- 1.2 and 1.9 +/- 1.2 versus 3.4 +/- 1.9, respectively; p < 0.01) and were exposed to less homologous blood products (1.3 +/- 1.7 and 2.1 +/- 1.1 versus 6.1 +/- 5, respectively; p < 0.001).
Conclusions: By preserving platelet function, aprotinin improves postoperative hemostasis in all patients who receive high dose and in most who receive low dose.