Thyroid and brain natriuretic peptide response in children undergoing cardiac surgery for congenital heart disease: Age-related variations and prognostic value

Background: Interest in hormonal response after pediatric cardiac surgery is growing, but many aspects remain unclear. The aim of this study was to test age-related variations and prognostic values of thyroid hormones, and brain natriuretic peptide (BNP) levels before and after surgery. Methods and Results: A total of 162 children undergoing cardiac surgery were divided into 3 age groups (group 1, n=57 neonates; group 2, n=58 infants; group 3, n=47 toddlers). Free thyroid hormones (fT3 and fT4), thyrotropin (thyroid-stimulating hormone [TSH]) and BNP were measured preoperatively, daily postoperatively in the intensive care unit and after 15 days. The primary outcome was time to extubation (TTE; variable used as time to event by survival analysis). The hormonal response differed among age groups. In older children the TSH nadir occurred at 6-12 h after surgery (0.42 mIU/L, P<0.001), with a progressive recovery thereafter, while in neonates the TSH nadir occurred later, at 36-60 h (0.14 mIU/L, P<0.001), followed by a much slower recovery. In neonates, BNP also dropped after surgery (from 2,899 to 824.0 ng/L, P<0.001) while increased in older children (from 71.00 to 527.00 ng/L, P<0.001). On multivariate analysis independent predictors of TTE were fT3 nadir in all age groups, together with TSH nadir and Aristotle score in neonates, and body surface area and BNP peak in older children. Conclusions: BNP and thyroid response after pediatric cardiac surgery differs widely according to age. Beside Aristotle score, combined measurement of fT3 and TSH are the strongest predictors of TTE, especially in neonates.