Subclinical hypothyroidism affects the intraoperative and postoperative hemodynamics in coronary artery bypass graft surgery: should we supplement with thyroxine preoperatively

Background
Our aim was to reveal the effect of the subclinical hypothyroid state on cardiac surgery, to derive a conclusion to include thyroid profile tests as a routine in cardiac surgery patients, and to know the role of thyroxine supplementation preoperatively in subclinical hypothyroid patients on the perioperative course.
Patients and methods
Between March 2007 and April 2010, we operated upon 87 patients of coronary artery revascularization, who had subclinical hypothyroidism as confirmed by laboratory investigations [high thyroid-stimulating hormone (TSH) and normal levels of T3 and T4]. We divided them into two groups: group A included patients who received preoperative thyroxine (47 patients) and group B included patients who were not supplemented with thyroxine preoperatively (40 patients). Preoperative, intraoperative, 24-h postoperative, and before discharge assessment of the cardiac function [ejection fraction percent (EF%)] as well as assessment of the thyroid profile (TSH, T3, and T4) were performed in all patients in both groups.
Results
We found an increased incidence of operative and postoperative complications in group B than in group A. The intraoperative and immediate postoperative EF% showed significant myocardial depression in group B ( < 0.003) and group A ( < 0.001) when compared with preoperative value. After 24 h of operation, the effect of thyroxine started to appear with a marked improvement in the cardiac functions in both groups. In group B, the EF% improved from 37.5 ± 3.07% at 12 h after operation to 45.6 ± 2.0% at 24 h after operation and to 53.76 ± 7.7% just before hospital discharge. With respect to the thyroid profile, there was a marked decrease in the level of T3 in group B intraoperatively (0.9 ± 0.3 pg/ml; < 0.002). The level was corrected 24 h postoperatively, after the intake of the Eltroxine, to 2.3 ± 0.8 pg/ml and then to 2.5 ± 1.1 pg/ml before hospital discharge. The level of TSH was markedly increased in group B intraoperatively (14.3 ± 4.7 μIU/l; = 0.007 between both groups). The TSH level started to decrease in both groups after intake of Eltroxine in hospital. There was an increased incidence of supraventricular arrhythmias, mainly atrial fibrillation (four cases in group A and eight cases in group B).
Conclusion
Thyroid function tests should be a routine preoperative investigation in any patient admitted for cardiac surgery. The preoperative supplementation of thyroxine is vital and decreases the operative and postoperative morbidity and mortality in patients with subclinical hypothyroidism.