Pharmacologic intervention to minimize postbypass bleeding and blood product transfusions has received increasing attention for both medical and economic reasons.Two hundred ten patients were entered into a double-blinded, prospective, randomized study to receive either 10 g of fibrinolytic inhibitor tranexamic acid before incision (n = 104) or 250 mL of placebo saline solution (n = 106). All subjects requiring cardiopulmonary bypass were deemed suitable, including those having first-time coronary bypass grafting, valve replacement, and reoperation.There were no statistically significant differences between the groups with respect to demographic or operative characteristics. The tranexamic acid group had a 48% reduction in 24-hour blood drainage (p0.001) and received 69% fewer total units of packed red blood cells, 83% fewer total units of plasma, and 75% fewer platelet transfusion units than controls. Only 13 of 104 tranexamic acid patients received blood products versus 33 of 106 controls (p0.001). The incidences of thrombotic complications, perioperative myocardial infarction, renal failure, and neurologic complications were not significantly different between the two groups. The tranexamic acid group had 0% mortality versus 1.9% for controls (not significant).Tranexamic acid is safe and effective in reducing blood loss and blood use in a wide variety of cardiac surgical patients.