OBJECTIVE: To test the hypothesis that triiodothyronine (T(3)) 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 T(3) (0.8 microg/kg followed by 0.12 microg.kg(-1).h(-1) 
for 6 hours), dopamine (positive control, 5 microg.kg(-1).min(-1) for 6 hours) 
or placebo.
MAIN OUTCOME MEASURES: Perioperative hemodynamic variables, inotropic support 
requirements, and serum T(3) concentrations.
RESULTS: Mean+/-SEM free T(3) serum 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 [0.7+/- 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 T(3). Intravenous T(3) did 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 T(3) 
does 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 T(3) as 
an inotropic agent in patients undergoing coronary artery bypass graft surgery.