Children undergoing cardiac operations in which cardiopulmonary bypass is used are at risk of significant postoperative blood loss. The acquired coagulopathy is complex but is thought to be due, in part, to excessive fibrinolysis. We examined the possibility of reducing postoperative blood loss in children by using the antifibrinolytic drug tranexamic acid. Using a prospective, randomized, double-blind study design, we administered a single dose of tranexamic acid (50 mg/kg intravenously) or saline placebo, before skin incision, in 88 children undergoing cardiac operations. Post-operative blood loss and fluid replacement were recorded for the next 24 hours. In addition, hemoglobin, platelet counts, and coagulation measures were recorded every 6 hours. When all patients were examined, there was no significant difference in postoperative blood loss between the treated and placebo groups (21.2 +/- 12 ml/kg per 24 hours, tranexamic acid, vs 27.2 +/- 20.3 mls/kg per 24 hours, placebo). However, when the children with cyanosis were analyzed separately, there was a highly significant difference in blood loss between the groups during the first 6 hours (11.2 +/- 3.7 ml/kg per 6 hours, tranexamic acid, vs 27.2 +/- 11.4 mls/kg per 6 hours, placebo; p < 0.002), as well as the overall 24 hour study period (23.7 +/- 7.5 mls/kg per 24 hours, tranexamic acid, vs 48.9 +/- 27.6 mls/kg per 24 hours, placebo; p < 0.02). Also significantly less blood and blood products were administered to the treated cyanosed group. Tranexamic acid produced a significant reduction in postoperative blood loss and blood product requirements in children with cyanosis undergoing heart operations. The drug had no effect in children without cyanosis or those requiring a second thoracotomy.

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There is a large variation in the dose of remifentanil tolerated by children while breathing spontaneously under anesthesia. A respiratory rate of <10 b.min(-1) appears to be the best predictor of the maximum tolerated dose.