Pharmacokinetic evaluation of triiodothyronine supplementation in childrenafter modified Fontan procedure

Background-Triiodothyronine (T-3) supplementation may be a useful adjunct i n the management of patients after cardiopulmonary bypass. Limited data are available regarding the use and pharmacokinetics of T-3 in children. The p resent study was performed to evaluate T-3 pharmacokinetics in a cohort of children undergoing the modified Fontan procedure. Methods and Results-A total of 28 patients were enrolled in this randomized , prospective study. The patients were divided into 4 groups: 1 group recei ved a placebo and 3 groups received intravenous T-3 at dosages of 0.4, 0.6, and 0.8 mu g/kg, respectively. All 28 patients survived their operative pr ocedures. Two patients developed low cardiac output, and 3 patients had ple ural effusions. The median length of hospital stay was 7 days. The mean fre e T-3 level was 316+/-67 pg/dL after then administration of a placebo. Pati ents who received T-3 had mean peak free T-3 levels of 972+/-88, 1351+/-299 , and 1869+/-281 pg/dL for the dosages of 0.4, 0.6, and 0.8 mu g/kg, respec tively, The calculated half-life of T-3 was 7 hours. Conclusions-The half-life of intravenous T-3 in children is approximately o ne-third of that reported for adults, These results provide a framework for studying the efficacy of T-3 supplementation in children undergoing open-h eart surgery.