Oral triiodothyronine normalizes triiodothyronine levels after surgery for pediatric congenital heart disease

Objectives: This study was conducted to determine if oral triiodothyronine supplementation could prevent the decrease of serum triiodothyronine levels that commonly occurs after cardiopulmonary bypass for pediatric congenital heart surgery. Secondary objectives included identifying any significant adverse effects of oral triiodothyronine supplementation, including any effects on the thyroid/pituitary axis. Design: Randomized, placebo-controlled, doubleblind clinical trial. Setting: Operating room and ICU. Subjects: Infants and children younger than 2 years of age undergoing congenital heart surgery using cardiopulmonary bypass (n = 43). Interventions: Subjects were assigned to placebo (n = 15, group A) or one of two treatment groups: a low-dose group (group B, n = 14, 0.5 mcg/kg triiodothyronine orally every 24 hr for 3 d) or a high-dose group (group C, n = 14, 0.5 mcg/kg triiodothyronine orally every 12 hr for 3 d). Measurements and Main Results: Thyroid hormone, including total and free triiodothyronine levels at predetermined time points, potential side effects indicatinghyperthyroidism, indicators of the thyroid-pituitary axis, and clinicalendpoints. Oral triiodothyronine supplementation twice-daily maintainedserum triiodothyronine levels within normal limits in groupC, whereas serum levels progressively declined in groups A and B. A statistically significant difference in triiodothyronine levels between the treatment groups occurred between 18 and 36 hourspost cross-clamp release, with the largest difference in serum levelsbetween group C and group A noted at 36 hours post cross-clamprelease (total triiodothyronine, 0.71 ± 0.15 [0.34-1.08] ng/mL [p < 0.01]; free triiodothyronine, 2.56 ± 0.49 [1.33-3.79] pg/mL [p < 0.01]). There was no evidence of hyperthyroidism or suppressionof the pituitary-thyroid axis in either treatment group. Conclusions: Oral triiodothyronine supplementation at a dose of 0.5 mcg/kg every 12 hours for 3 days can maintain total and free triiodothyronine levels within normal limits after open-heart surgery using cardiopulmonary bypass for congenitalheart disease.