Effects of nafamostat mesilate and minimal-dose aprotinin on blood-foreign surface interactions in cardiopulmonary bypass

Background The pharmacological inhibition of blood-foreign surface interactions is an attractive strategy for reducing the morbidity associated with cardiopulmonary bypass. We compared the inhibitory effects of nafamostat mesilate (a broad-spectrum synthetic protease inhibitor) and minimal-dose aprotinin on blood-surface interactions in clinical cardiopulmonary bypass. Methods Eighteen patients undergoing coronary surgery were divided into three groups: (1) the control group (heparin, 4 mg/kg; n=6), (2) the nafamostat mesilate group (heparin plus nafamostat, 0.2 mg/kg bolus followed by 2.0 mg/kg/h during cardiopulmonary bypass; n=6), and (3) the aprotinin group (heparin plus aprotinin, 2.0 × 10 4 KIU/kg; n=6). Platelet count, platelet aggregation, β-thromboglobulin, prothrombin fragment F1.2, thrombin-antithrombin complex, plasminogen activator inhibitor-1, α2-plasmin inhibitor-plasmin complex, D-dimer, neutrophil elastase, and interleukin-6 were measured before, during, and after bypass. Bleeding times and blood loss were recorded. Results There were no significant differences between groups in platelet count, β-thromboglobulin, plasminogen activator inhibitor-1, interleukin-6, bleeding times, or blood loss. Platelet aggregation was better preserved at 12 hours after surgery in the nafamostat and aprotinin groups than in the control group. Prothrombin fragment F1.2, thrombin-antithrombin complex and neutrophil elastase levels were significantly reduced by aprotinin, but not by nafamostat as compared with the control group. The α2-plasmin inhibitor-plasmin complex and D-dimer were significantly lower with either of the drugs. Aprotinin showed better control of D-dimer than did nafamostat. Conclusions Nafamostat mesilate fails to reduce thrombin formation and neutrophil elastase release, whereas minimal-dose aprotinin inhibits both. Neither nafamostat nor aprotinin inhibits platelet activation. Nafamostat reduces fibrinolysis during cardiopulmonary bypass, although its effect is not as potent as aprotinin.