Document Type : Original Article



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 
 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
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.


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