Identifying infants at risk of marked thyroid suppression post-cardiopulmonary bypass

Abstract

Objective: The clinical benefit of tri-iodothyrinone (T(3)) replacement following congenital heart surgery with cardiopulmonary bypass (CPB) is not clear in unselected cohorts of children. Infants with more marked thyroid hormone suppression or prolonged post-CPB recovery may benefit from T(3) replacement. This study aimed to identify infants at risk of more marked suppression by examining the relationship between organ support parameters during CPB and post-operative thyroid hormone levels.

Design and setting: Prospective observational study in a tertiary referral centre for congenital heart surgery.

Patients: 36 infants less than 12 months of age were recruited following CPB.

Measurements and results: Thyroid hormone levels were measured on admission to the intensive care unit and on post-operative days 1 and 2. Increasing CPB time was associated with decreasing admission free T(3) and thyroid-stimulating hormone. Younger, smaller infants had lower admission levels of free T(3) on univariant analysis. Infants who continued to require ventilation 48 h after admission to the ICU had a mean free T(3) level on post-operative day 2 that was 0.9 pmol/l lower than in those who had been extubated.

Conclusions: Prospective studies of T(3) replacement in selected young infants (less than 3 months) with long CPB time (greater than 120 min) during congenital heart surgery are warranted.