Reperfusion injury often develops after cardiopulmonary bypass (CPB) during coronary artery bypass grafting (CABG), and MgSO4 is known to be related to such injury. The goal of this study was to determine the hemodynamic and oxygen metabolic effects of administering MgSO4 after cessating cardiopulmonary bypass during coronary bypass surgery in control and nicardipine infusion groups.

After obtaining hospital ethics committee clearance, we studied 29 patients with coronary artery disease scheduled for CABG, who were randomly assigned to receive nicardipine (0.5 microgram/kg/min, n = 11) or placebo (n = 18). All patients were administered MgSO4 (60 mg/kg) after the cessation of CPB. The hemodynamic variables and oxygen parameters were recorded and calculated by continuous cardiac output and mixed venous oxygen saturation monitoring, through a thermodilution Swan-Ganz catheter before and 20 minutes after MgSO4 administration.

Heart rate was reduced after administering MgSO4 in both groups, and the mean arterial pressure was also reduced in the nicardipine group. The cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, right and left stroke work indices were well-maintained after administering MgSO4. Mixed venous oxygen saturation and other oxygen parameters were maintained without change after MgSO4 administration.

The present study shows that MgSO4 can be used without inducing any significant oxygen metabolism or hemodynamic derangements during CABG. But further work is needed to elucidate the myocardial protective effects of MgSO4.