THYROID-HORMONE TREATMENT AFTER CORONARY-ARTERY BYPASS-SURGERY

Background. Thyroid hormone has many effects on the cardiovascular sys tem. During and after cardiopulmonary bypass, serum triiodothyronine c oncentrations decline transiently, which may contribute to postoperati ve hemodynamic dysfunction. We investigated whether the perioperative administration of triiodothyronine (liothyronine sodium) enhances card iovascular performance in high-risk patients undergoing coronary-arter y bypass surgery. Methods. We administered triiodothyronine or placebo to 142 patients with coronary artery disease and depressed left ventr icular function. The hormone was administered as an intravenous bolus of 0.8 mu g per kilogram of body weight when the aortic cross-clamp wa s removed after the completion of bypass surgery and then as an infusi on of 0.113 mu g per kilogram per hour for six hours, Clinical and hem odynamic responses were serially recorded, as was any need for inotrop ic or vasodilator drugs. Results. The patients' preoperative serum tri iodothyronine concentrations were normal (mean [+/-SD] value, 81+/-22 ng per deciliter [1.2+/-0.3 nmol per liter]), and they decreased by 40 percent (P<0.001) 30 minutes after the onset of cardiopulmonary bypas s, The concentrations in patients given intravenous triiodothyronine b ecame supranormal and were significantly higher than those in patients given placebo (P<0.001). However, the concentrations were once again similar in the two groups 24 hours after surgery. The mean postoperati ve cardiac index was higher in the triiodothyronine group (2.97+/-0.72 vs. 2.67+/-0.61 liters per minute per square meter of body-surface ar ea, P=0.007), and systemic vascular resistance was lower (1073+/-314 v s. 1235+/-387 dyn . sec . cm(-5), P=0.003). The two groups did not dif fer significantly in the incidence of arrhythmia or the need for thera py with inotropic and vasodilator drugs during the 24 hours after surg ery, or in perioperative mortality and morbidity. Conclusions. Raising serum triiodothyronine concentrations in patients undergoing coronary -artery bypass surgery increases cardiac output and lowers systemic va scular resistance but does not change outcome or alter the need for st andard postoperative therapy.