CommentThe stated purpose of this article was to find the optimal dose of tranexamic acid using a methodology of bolus administration followed by infusion of one-tenth that bolus for 12 hr. The reader is reminded that this study only looked at postoperative blood loss and not intraoperative blood loss. Although this paper is well presented, its real interest perhaps stems from issues relating to blood conservation that were alluded to in the text.The first was the attempt to identify factors that were linked to less postoperative blood loss. These were female gender, undergoing repeat sternotomy, and increased weight. The reduced blood loss found in patients having repeat sternotomy is, of course, counterintuitive. Although the authors introduce the possibility that tranexamic acid may have some increased efficacy in patients undergoing repeat sternotomy, the more likely explanation lies in the fact that only 20 (13%) of their patients were having repeat cardiac surgery. They also point out that the surgical team may have been more attentive to intraoperative hemostasis in this category of patients.Although tranexamic acid reduced total postoperative blood loss, the only risk factor for receiving a blood transfusion was having a low hematocrit initially. Tranexamic acid approached significance (P< 0.075) and might have an impact on a population larger than 200. Another explanation may be that this team was willing to withhold transfusions until the hematocrit was 20%, thereby reducing the overall incidence of transfusions and placing only a select group of patients at risk in the first place.