BackgroundAntifibrinolytic medications administered before skin incision decrease bleeding after cardiac surgery. Numerous case reports indicate thrombus formation with administration of [Greek small letter epsilon]‐aminocaproic acid ([Greek small letter epsilon]‐ACA). The purpose of this study was to examine the efficacy of [Greek small letter epsilon]‐ACA administered after heparinization but before cardiopulmonary bypass in reducing bleeding and transfusion requirements after primary coronary artery bypass surgery.MethodsSeventy‐four adult patients undergoing primary coronary artery bypass surgery were randomized to receive 125 mg/kg [Greek small letter epsilon]‐ACA followed by an infusion of 12.5 mg [middle dot] kg‐1[middle dot] h‐1or an equivalent volume of saline. Coagulation studies, thromboelastography, and platelet aggregation tests were performed preoperatively, after bypass, and on the first postoperative day. Mediastinal drainage was recorded during the 24 h after surgery. Homologous blood transfusion triggers were predefined and transfusion amounts were recorded.ResultsOne patient was excluded for surgical bleeding and five patients were excluded for transfusion against predefined criteria. One patient died from a dysrhythmia 2 h postoperatively. Among the remaining 67, the [Greek small letter epsilon]‐ACA group had less mediastinal blood loss during the 24 h after surgery, 529 +/‐ 241 ml versus 691 +/‐ 286 ml (mean +/‐ SD), P < 0.05, despite longer cardiopulmonary bypass times and lower platelet counts, P < 0.05. Platelet aggregation was reduced in both groups following cardiopulmonary bypass but did not differ between groups. Homologous blood transfusion was similar between both groups.ConclusionsProphylactic administration of [Greek small letter epsilon]‐ACA after heparinization but before cardiopulmonary bypass is of minimal benefit for reducing blood loss postoperatively in patients undergoing primary coronary artery bypass grafting.