The Effect of Hypothyroidism on a Composite of Mortality, Cardiovascular and Wound Complications After Noncardiac Surgery: A Retrospective Cohort Analysis.

BACKGROUND: We tested the hypothesis that hypothyroidism, as defined by thyroid-stimulating hormone (TSH) concentration, is associated with a severity-weighted composite of mortality and major cardiovascular and infectious complications after noncardiac surgery.

METHODS: In this retrospective cohort study, we evaluated adults at the Cleveland Clinic Main Campus between 2005 and 2012, who had had available TSH concentrations within the 6 months before noncardiac surgery. Patients were categorized as (1) hypothyroid (patients who had diagnosis of hypothyroidism any time prior to surgery and increased TSH value (> 5.5 mIU/L) within 6 months prior to surgery); (2) treated (hypothyroid diagnosis and normal TSH concentrations [0.4-5.5 mIU/L]); and (3) euthyroid (no hypothyroid diagnosis and normal TSH concentrations). We conducted pairwise comparisons among the 3 groups using inverse propensity score weighting to control for observed confounding variables. Average relative effect generalized estimating equation model was used for the primary outcome composite of in-hospital cardiovascular morbidity, surgical wound complication or infection, and mortality. Logistic regression and Cox proportional hazards regression were used for secondary outcomes of intraoperative vasopressor use and duration of hospitalization, respectively.

RESULTS: We identified 800 hypothyroid patients (median TSH: 8.6 mIU/L [Q1, Q3: 6.5, 13.0]), 1805 treated patients (2.0 mIU/L [1.1, 3.2]), and 5612 euthyroid patients (1.7 mIU/L [1.1, 2.6]). There were no significant differences among the hypothyroid, treated, and euthyroid patients on the primary composite outcome (all P values ≥0.30). Hypothyroid patients were slightly more likely to receive vasopressor during surgery than either treated (odds ratio, 1.17; 99.2% confidence interval [CI], 1.01-1.36) or euthyroid (odds ratio, 1.12; 99.2% CI, 1.02-1.24) patients. Furthermore, hypothyroid patients were slightly but significantly less likely to be discharged at any given postoperative time than treated patients (hazard ratio, 0.92; 99.2% CI, 0.86-0.99).

CONCLUSIONS: Hypothyroidism was not associated with worse postoperative mortality, wound, or cardiovascular outcomes in noncardiac patients. Thus, postponing surgery to initiate thyroid replacement therapy in patients with hypothyroidism seems unnecessary.