Background:There have been many concerns about alteration in hemodynamic parameters within and shortly after endotracheal intubation (ETI) in patients scheduled for elective coronary artery bypass grafting (CABG).Objectives:We compared the attenuation effect of magnesium sulfate and lidocaine on hemodynamic responses after ETI, in patients undergoing CABG.Patients and Methods:In this randomized controlled trial 150 patients undergoing elective CABG were enrolled. Included patients were randomly allocated to three groups and received lidocaine (1.5 mg/kg), magnesium sulfate (50 mg/kg within five minute), or normal saline, 90 seconds before ETI. Baseline hemodynamic parameters including heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were recorded immediately before anesthesia induction, before intubation, immediately after intubation, and at second and fifth minutes after intubation.Results:The baseline hemodynamic variables had no deference among the three groups. HR between intubation and five minute after intubation was significantly lower in two groups received lidocaine or magnesium sulfate in comparison with placebo group. Lidocaine induced more than 20% decrease in HR and MAP immediately after intubation; hence, lidocaine group showed significant MAP reduction in comparison with the two other groups.Conclusions:Lidocaine induced hemodynamic instability but premedication of magnesium sulfate maintained hemodynamic stability after intubation. Therefore, in patients undergoing CABG who received high-dose intravenous analgesic for general anesthesia, the administration of magnesium sulfate might result in maintaining hemodynamic stability after ETI in comparison with lidocaine.