Triiodothyronine Supplementation in Patients Undergoing...
Patients undergoing cardiopulmonary bypass may develop clinically significant physiologic alterations in the perioperative period, including alteration of thyroid hormone concentrations. Alterations in the concentration of thyroid hormones are of concern due to the effects of these hormones on cardiac function. Hypothyroidism is associated with a decrease in cardiac performance; therefore, supplementation with the active thyroid hormone triiodothyronine (T₃) in patients undergoing cardiopulmonary bypass has been investigated to improve outcomes. In addition, T₃ has been studied as an agent to reduce the frequency of atrial fibrillation after cardiopulmonary bypass.

Clinically significant physiologic alterations result when a patient undergoes cardiopulmonary bypass. These alterations may include neurologic, hematologic, renal, and endocrine sequelae. Among the endocrine alterations, attention has been placed on the effect of cardiopulmonary bypass on thyroid hormones because of the effects of these hormones on cardiac function. Specifically, cardiopulmonary bypass has been shown to decrease concentrations of triiodothyronine (T₃), the physiologically active thyroid hormone, thus inducing a hypothyroid state.

Hypothyroidism is associated with a decrease in myocardial contractility, decrease in heart rate, decrease in cardiac output and stroke volume, and an increase in systemic vascular resistance (SVR). The effect of this decline in cardiac performance may result in difficulty weaning the patient from cardiopulmonary bypass at the end of the procedure. Therefore, investigations were undertaken to determine if supplementation with T₃ could improve cardiac function and improve patient outcomes. Subsequently, the utility of T₃ in preventing atrial fibrillation after cardiopulmonary bypass was assessed.