Background: Narcotics are the most common drugs used after cardiac surgery and their side effects, including respiratory depression, hemodynamic instability, nausea and vomiting, and itching are dose dependent. Magnesium is both an N Methyl D Aspartate (NMDA)-receptor and a calcium-receptor antagonist and can modify the important mechanisms of nociception. The purpose of this study was to investigate the effect of magnesium sulfate on the pain score and reducing narcotic requirement in coronary artery bypass grafting surgery (CABG) patients.
Methods: This randomized, double blinded, placebo-controlled trial recruited 185 patients (105 male and 80 female) undergoing elective CABG. Mean age was 58±11 years (range=24 to 79 years). The patients were divided into two groups randomly: Group 1 received magnesium sulfate as an IV infusion (80 mg/kg) during a one-hour period post induction and Group 2 received the same volume of normal saline as a placebo. During the postoperative period, the patients’ morphine requirement and pain score (visual analogue scale=scaled as 0 to 10, 0=no pain and 10=worst possible pain) at 6^th, 12^th, 18^th, and 24^th hours were recorded and documented.
Results: There were no significant differences between the two groups with respect to the baseline data. In the magnesium sulfate group, only 30 (32%) patients needed morphine sulfate, whereas 75 (83%) patients in the placebo group required some doses of morphine sulfate (p value<0.001). The odds ratio showed that magnesium sulfate could strongly prevent the need for opioid analgesics for pain control.
Conclusion: The intraoperative use of magnesium sulfate can reduce the need for opioids post CABG.