OBJECTIVE: This study aims to elucidate the relationship between thyroid function and surgical prognosis in patients undergoing cardiac and major vascular surgeries. METHODS: A retrospective cohort study was conducted on patients undergoing cardiac or major vascular surgeries. Preoperative thyroid function tests, including TSH, free T3, and free T4 levels, as well as postoperative thyroid function tests, were assessed. Key postoperative outcomes, such as total hospital stay, postoperative hospital stay, ICU stay, and duration of mechanical ventilation, were recorded and analyzed. The analytical approach included Pearson correlation, multivariable logistic regression models, and restricted cubic splines. RESULTS: This study analyzed a cohort of 472 patients who underwent various cardiovascular surgeries, including coronary artery bypass grafting (173 patients), aortic surgery (131 patients), valve surgery (125 patients), and primary cardiac neoplasms resection (43 patients). Significant changes in thyroid hormone levels were observed preoperatively and postoperatively, with TSH, FT3, and FT4 levels showing a significant decrease from preoperative values (p <
0.001). Multivariate logistic regression analysis further revealed that ΔTSH is significantly associated with total hospital stay, postoperative hospital stay, and duration of mechanical ventilation
postoperative FT3 levels were significantly inversely related to total hospital stay, ICU stay, and ventilator requirements. Additionally, although no significant nonlinear relationships were found (all p >
0.05). CONCLUSIONS: Thyroid dysfunction may impact postoperative outcomes in cardiac and major vascular surgery patients.