The role of magnesium sulfate in tracheal intubation without muscle relaxation in patients undergoing ophthalmic surgery

BACKGROUND Muscle relaxant agents usually use to facilitate tracheal intubation; however, sometimes limitations exist. Magnesium (Mg) sulfate is a candidate for muscle relaxant substitute. This study was designed to determine the effect of Mg sulfate accompanied with propofol and fentanyl in patients undergoing ophthalmic surgery. MATERIALS AND METHODS In a double-blind randomized protocol and before tracheal intubation, Mg sulfate 40, 45, or 50 mg/kg in 100 ml of saline (Groups 1-3, respectively) or saline alone (Group 4) were administrated intravenously in 100 patients (n = 25 in each group) with the American Society of Anesthesiologist (ASA) physical Status I, II, or III. The patients' intubation condition in all subjects were determined and described. RESULTS The patients' demographic data including age, ASA, systolic and diastolic blood pressures, intraocular pressure, and body mass index were not significantly different between the groups. A better mask ventilation feasibility in Mg sulfate 45 group (Group 2) was observed when compared with Mg sulfate 50 (Group 3) (P = 0.022) and saline group (Group 4) (P = 0.021). In addition, the vocal cord movement and muscle relaxant requirement in saline group were significantly different from others groups (P < 0.05). The laryngoscopic time in saline group was greater than other groups significantly (P < 0.0001). CONCLUSION Intravenous administration of Mg sulfate accompanied with propofol and fentanyl facilitates the tracheal intubation without neuromuscular blocking agents. To avoid Mg level increasing in plasma; however, the low dose of Mg sulfate is suggested.