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.