Tri-iodothyronine treatment in children after cardiac surgery: a double-blind, randomised, placebo-controlled study

Serum thyroid hormone concentrations decline transiently during critical illness and after surgical procedures. We investigated prospectively the endocrine and haemodynamic effects of tri-iodothyronine treatment after cardiopulmonary bypass operations in children with congenital cardiac malformations. We did a randomised, double-blind, placebo-controlled trial, in which 40 children (median age 0·6 years; range 2 days to 10·4 years) were randomly assigned placebo (saline) or one daily infusion of tri-iodothyronine (2 μg/kg bodyweight on day 1 after surgery and 1 μg/kg bodyweight on subsequent postoperative days up to 12 days after surgery. Before and 2 h, 24 h, and 72 h after the first infusion, plasma concentrations of thyroid hormones were measured by RIA, and systolic cardiac function was evaluated by echocardiography. During the postoperative course intensive-care measures were assessed by use of the therapeutic intervention scoring system. In all patients, postoperative plasma concentrations of thyrotropin, thyroxine, free thyroxine, tri-iodothyronine were abnormally low and plasma concentrations of reverse tri-iodothyronine were raised. After start of treatment, tri-iodothyronine was significantly higher in patients given tri-iodothyronine than in those receiving placebo, whereas thyrotropin, thyroxine, free thyroxine, and reverse tri-iodothyronine remained similar in the two groups. At discharge, thyroid hormones of all patients were within the normal range, but thyrotropin secretion increased to plasma concentrations higher than those seen before treatment. The mean change of cardiac index was significantly higher in children given tri-iodothyronine (20·4% [SD 19·6] vs 10·0% [15·2]; p=0·004). Systolic cardiac function improved most in patients given tri-iodothyronine after longer cardiopulmonary bypass operations. Overall, patients given tri-iodothyronine had significantly lower mean treatment scores. Treatment of children with tri-iodothyronine after cardiopulmonary bypass operations raises tri-iodothyronine plasma concentrations and improves myocardial function especially in patients with low postoperative cardiac output without adverse events, and without delaying postoperative recovery of thyroid function. Furthermore, tri-iodothyronine reduces the need for postoperative intensive care.