Aprotinin administration in the pericardial cavity does not prevent platelet activation

Objectives: Aprotinin is frequently administered systemically to patients u ndergoing cardiopulmonary bypass to inhibit activation of platelets and pla sma protein systems and thus reduce postoperative blood loss. Two reports o n local aprotinin administration, that is, into the pericardial cavity, als o indicated improvement in postoperative blood loss, but the underlying mec hanism was not investigated. We previously reported the disappearance of gl ycoprotein Ib from the platelet surface and the appearance of platelet-deri ved microparticles in the pericardial cavity of patients undergoing cardiop ulmonary bypass as signs of platelet activation. Here, we investigated whet her such local aprotinin administration reduced platelet activation. Methods: In a double-blind study, 6 patients received aprotinin (500,000 KI U) into the pericardial cavity during the operation and 7 patients received a placebo. Platelet surface glycoprotein Ib expression, concentration of m icroparticles, and concentration of complexes of platelets with leukocytes, erythrocytes, or each other, were measured by flow cytometry. Results: We confirmed the reduced glycoprotein Ib expression and the increa sed concentration of microparticles in the pericardial cavity, as previousl y reported, and found no increased concentration of platelet complexes. How ever, no differences between aprotinin and placebo treatments were observed in these platelet activation parameters in the pericardial cavity or the s ystemic circulation. Conclusion: We conclude that administration of aprotinin into the pericardi al cavity during cardiopulmonary bypass and at concentrations similar to th e systemic application does not reduce platelet activation in that compartm ent or the systemic circulation.