Abstract: Objective: The aim of this study is to evaluate altered thyroid function after off-pump coronary artery bypass surgery among patients aged over 80-year-old, and to investigate the potential association between thyroid alterations and postoperative parameters. Methods: From 2005-6 to 2009-12, alterations in thyroid function were analyzed in 50 patients. The blood samples were taken on 1 day prior to surgery, upon arrival to ICU, and on postoperative day 1, 2, 5. Meanwhile, according to European System for Cardiac Operative Risk Evaluation, the patients were divided into high risk group or median and low risk group. The altered thyroid function and perioperative parameters were compared between two groups. Results: Among 50 patients studied, except free thyroxine increased transiently, other thyroid hormone decreased significantly. There were statistical differences between the groups in clinical data, including inotropic score, IABP assist, mean duration of ventilatory support and mean length of ICU stay. Additionally, 12 patients of high risk group exhibited significantly lower levels of total and free triiodothyronine as compared with 38 patients of median and low risk group; No significant differences in levels of total and free thyroxine were observed between two groups; Thyroid-stimulating hormone differed significantly between two groups, and the recovery in thyroid-stimulating hormone was observed in median and low risk group, as was recognized the initiation of re-establishment of thyroid hormones homeostasis from suppression. Conclusion: Our findings indicated that off-pump surgery could not prevent the onset of nonthyroid illness syndrome, and the low triiodothyronine in critically cardiosurgical patients was observed to correspond to the period when hemodynamic dysfunction occurred, which had important implications for prognosis and therapy after cardiac surgery.

Key words: Thyroid hormone, Nonthyroid illness syndrome, Cardiac intensive care Coronary artery bypass surgery