Preoperative thyroid hormone levels predict ICU mortality after cardiopulmonary bypass in congenital heart disease patients younger than 3 months old

Background We aimed to study the effectiveness of preoperative thyroid hormone levels in predicting intensive care unit (ICU) mortality after cardiopulmonary bypass (CPB) in infants with congenital heart disease (CHD). Methods We retrospectively reviewed and analyzed data from 133 patients younger than 3 months old who underwent cardiac surgery with CPB from June 2017 to November 2019. ICU mortality prediction was assessed by multivariate binary logistic regression analysis and area under the curve (AUC) analysis. Results Non-survivors were younger (17.46 ± 17.10 days vs. 38.63 ± 26.87 days, P = 0.006), with a higher proportion of neonates (9/13 vs. 41/120, P = 0.017) and a higher proportion of individuals with a Risk Adjustment for Congenital Heart Surgery-1 (RACHS-1) score ≥ 4 (8/13 vs. 31/120, P = 0.020). No significant difference was found in CPB and aortic cross-clamping (ACC) time. The levels of free triiodothyronine (FT3) (3.91 ± 0.99 pmol/L vs. 5.11 ± 1.55 pmol/L, P = 0.007) and total triiodothyronine (TT3) (1.55 ± 0.35 nmol/L vs. 1.90 ± 0.57 nmol/L, P = 0.032) were higher in survivors than in non-survivors. In the ICU mortality prediction assessment, FT3 was an independent mortality predictor and showed a high AUC (0.856 ± 0.040). Conclusions The preoperative FT3 level was a powerful and independent predictor of ICU mortality after CPB in infants with CHD younger than 3 months old.