Thyroid function during and after cardiopulmonary bypass in children.

Background: The aim of the study was to elucidate the changes in thyroid function during and after cardiopulmonary bypass (CPB) in children.

Methods: Triiodothronine (T3), thyroxine (T4), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were determined preoperatively, at specific times throughout CPB, and serially up to 48 h postoperatively, in 10 children (median age 35, range 23-68 months) undergoing elective surgery for congenital heart disease.

Results: T3 decreased from 2.01 +/- 0.08 preoperatively to 0.94 +/- 0.10 nmol/l 24 h postoperatively (P < 0.05). T4 levels followed a pattern similar to changes in T3. FT4 increased from 17.4 +/- 0.7 preoperatively to 30.0 +/- 0.4 pmol/l after 30 min of CPB (P < 0.05). TSH decreased from 2.44 +/- 0.43 preoperatively to 0.93 +/- 0.21 24 h postoperatively (P < 0.05).

Conclusion: T3, T4 and TSH are significantly depressed after open heart surgery in children.