A prospective randomized and double-blind study was performed to evaluate 
whether perioperative triiodothyronine administration has any effect on 
cardiovascular performance after coronary artery bypass surgery. Sixty patients 
were assigned to 2 groups of 30 each. When crossclamping ended, group A received 
an intravenous bolus of triiodothyronine, followed by infusion for 6 hours. 
Group B received a placebo. Serum triiodothyronine levels and hemo-dynamic 
parameters were serially measured. Mean postoperative cardiac index was 
slightly, but not significantly, higher in group A, whereas systemic vascular 
resistance was significantly lower in group A. Compared with preoperative 
values, serum triiodothyronine levels dropped significantly in group B at the 
end of cardiopulmonary bypass and remained low 12 hours postoperatively, while 
levels rose significantly in group A. No significant differences were detected 
between the groups in the incidence of arrhythmia, the need for inotropic 
support, intensive care unit stay, mortality, and morbidity. Perioperative 
administration of triiodothyronine increased cardiac output slightly and 
decreased systemic vascular resistance, but it had no effect on operative 
outcome. Routine use after coronary surgery is thus not recommended.