Cardiovascular Effects of Intravenous Triiodothyronine in Patients Undergoing Coronary Artery Bypass Graft Surgery

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Abstract
Objective. —To test the hypothesis that triiodothyronine (T3) administration improves hemodynamic variables and decreases inotropic drug requirements in cardiac surgery patients. Design. —Prospective, randomized, double-blind, placebo-controlled trial. Setting. —Tertiary care medical center. Patients. —A total of 211 patients undergoing coronary artery surgery at high risk for requiring inotropic drug support. Intervention. —At release of aortic cross-clamp, patients were randomized to an intravenous infusion of T3(0.8 μg/kg followed by 0.12 μg·kg-1·h-1for 6 hours), dopamine (positive control, 5 μg·kg-1·min-1for 6 hours), or placebo. Main Outcome Measures. —Perioperative hemodynamic variables, inotropic support requirements, and serum T3concentrations. Results. —Mean±SEM free T3serum concentrations decreased significantly during cardiopulmonary bypass in all groups (from 0.0035±0.0001 nmol/L [0.23±0.01 ng/dL] to 0.001±0.0001 nmol/L [0.07±0.00 ng/dL];P=001) and increased to 0.0133±0.0004 nmol/L [0.87±0.03 ng/dL] (twice normal range;P<.001) following initiation of intravenous T3. Intravenous T3did not change hemodynamic variables or inotropic drug requirements; however, heart rate increased (P<.001), and a trend toward decreased use of inotropic agents was demonstrated in the dopamine group. Conclusions. —Triiodothyronine administration prevents decreases in serum thyroid hormone concentrations associated with cardiopulmonary bypass. Intravenous T3does not have dramatic effects on hemodynamic variables in this setting as has been previously suggested. Although mild effects on myocardial performance may exist, we cannot recommend at this time the routine use of intravenous T3as an inotropic agent in patients undergoing coronary artery bypass graft surgery. (JAMA. 1996;275:687-692)