High-Dose Insulin Administration Improves Left Ventricular Function After Coronary Artery Bypass Graft Surgery

ObjectiveTo test the hypothesis that the intravenous administration of high doses of insulin while maintaining normoglycemia (GIN therapy) improves myocardial function after coronary artery bypass graft (CABG) surgery.DesignA prospective, randomized clinical trial.SettingA university hospital.ParticipantsForty patients undergoing elective CABG surgery.InterventionsPatients were randomized to the GIN or control group. Applying the principles of the hyperinsulinemic-normoglycemic clamp technique in the GIN group, insulin was administered at 5 mU/kg/min during surgery. Glucose 20% was infused at a rate adjusted to maintain blood glucose (BG) between 4.0 and 6.0 mmol/L. Patients in the control group received insulin on a sliding scale, also aiming at normoglycemia.Measurements and Main ResultsSystemic hemodynamic parameters included heart rate, mean arterial pressure, pulmonary artery wedge pressure, vascular resistance index, and cardiac index (CI). Left ventricular function was assessed by transesophageal echocardiography using the myocardial performance index (MPI) as a parameter of global left ventricular function, the fractional area change (FAC) for systolic function, and flow propagation velocity for diastolic function before and after surgery. All patients receiving GIN therapy were hyperinsulinemic (3,474 ± 1,204 pmol/L) and normoglycemic, showing a lower mean BG concentration (4.9 ± 0.5 mmol/L) than patients in the control group (8.2 ± 2.0 mmol/L). Patients receiving GIN therapy had an increased CI after surgery compared with the control group (p = 0.005). The GIN therapy was associated with improved MPI and FAC values when compared with standard care. Also, there was no difference in the parameters indicating left ventricular diastolic function.ConclusionsIntraoperative GIN therapy improves global and systolic left ventricular function after CABG surgery.