Half-dose aprotinin preserves hemostatic function in patients undergoing bypass operations.

High-dose aprotinin reduces bleeding in cardiac operations but with potential side-effects and increased cost. It is therefore mandatory that the effectiveness of a low dose be investigated. Half of the Hammersmith regimen was studied in cardiac surgical patients to find out how it could reduce bleeding. Blood fibrinolysis parameters were studied in 40 elective patients undergoing coronary artery bypass grafting in a double-blind, placebo-controlled study design. The plasma activities of tissue plasminogen activator, plasminogen activator inhibitor, alpha 2-antiplasmin, plasminogen, fibrinogen, and D-dimer as well as platelet number, bleeding times, activated clotting time, and aprotinin plasma concentrations were assessed before, during, and after the operation. Fibrinolysis was inhibited by aprotinin as evidenced by decreased D-dimer (p = 0.0001) and tissue plasminogen activator (p = 0.0432) levels and increased plasminogen activator inhibitor (p = 0.0105) and alpha 2-antiplasmin (p = 0.0002) levels during the operation. A postoperative abnormal bleeding time occurred 38% more frequently in the placebo group (p < 0.05). Aprotinin plasma concentrations reached adequate levels to inhibit plasmin and plasma kallikrein. This study showed that half-dose aprotinin significantly inhibits fibrinolysis and prevents postoperative abnormal bleeding time in cardiac surgical patients.