Different doses of intravenous Magnesium sulfate on cardiovascular changes following the laryngoscopy and tracheal intubation: A double-blind randomized controlled trial.

OBJECTIVE: Laryngoscopy and intratracheal intubation may cause acute hemodynamic instabilities due to catecholamine release. Magnesium sulfate (MgSO4) prevents catecholamine release and results in bradycardia and vasodilatation, so can be used to diminish complications of laryngoscopy and intubation in doses > 50 mg/kg. The aim of this study was to compare the different doses of MgSO4 used to improve cardiovascular instabilities due to laryngoscopy and intratracheal intubation.

METHODS: In this double-blind randomized controlled trial, 120 patients undergoing elective surgery were divided equally into four groups (n = 30) and received different doses of MgSO4 as case groups (Group I: 30 mg/kg, Group II: 40 mg/kg, Group III: 50 mg/kg) or the equal volume of normal saline as a control group. The patients' hemodynamic status was recorded at baseline, before laryngoscopy and in 1, 3, 5, and 10 minutes after laryngoscopy. Bradycardia, tachycardia, hypertension, hypotension, ST-T changes, arrhythmias, and duration of extubation and laryngoscopy were also recorded.

FINDINGS: There was no significant difference in heart rate between four groups (Pbaseline = 0.46, Ppreoperation = 0.55, P1 min = 0.86, P3 min = 0.30, P5 min = 0.63, P10 min = 0.74). Systolic, diastolic and mean arterial pressures were statistically significant less at 1, 3, and 5 minutes after intubation in comparison with other times of following-up in the three groups received MgSO4 than the control group.

CONCLUSION: The use of MgSO4 in doses less than 50 mg/kg can be effective to reduce cardiovascular instability related to laryngoscopy and tracheal intubation.