Comparison of the Two Doses (30 mg/kg versus 50 mg/kg) of Magnesium Sulphate in Attenuation of Haemodynamic Stress Response during Laryngoscopy and Tracheal Intubation: A Randomised Clinical Study

Introduction: Laryngoscopy and endotracheal intubation are known to elicit significant sympathoadrenal responses, which can lead to haemodynamic instability. Magnesium sulphate has been shown to attenuate this stress response through various mechanisms.

Aim: To compare the efficacy of two different doses of magnesium sulphate (30 mg/kg vs 50 mg/kg) in attenuating the haemodynamic changes during laryngoscopy and tracheal intubation.

Materials and Methods: This randomised clinical study was conducted at the Department of Anaesthesiology, Shrimati Bhikhiben Kanjibhai Shah Medical Institute and Research Centre, Sumandeep Vidyapeeth Deemed To Be University, Piparia, Vadodara, Gujarat, India, from January 2023 to June 2024. It included 60 American Society of Anaesthesiologists (ASA) physical status grade I and II patients aged 18-65 years scheduled for elective surgeries under general anaesthesia. Patients were randomly divided using computerised randomisation into two groups of 30 each: Group I received magnesium sulphate 30 mg/kg intravenoulsy (i.v.), and Group II received magnesium sulphate 50 mg/kg i.v. diluted in 50 mL of normal saline, administered over 10 minutes before induction. Haemodynamic parameters (heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure) were recorded at baseline, after drug administration, after induction, during laryngoscopy and intubation, and at 1, 3, 5, 7, and 10 minutes post-intubation. Statistical analysis was performed using unpaired Student’s t-test and Chi-square test, with p-value<0.05 considered significant.

Results: The demographic characteristics (mean age: group I 38.9±7.5 years, group II 41.0±8.8 years; gender ratio M:F - group I 17:13, group II 18:12; mean weight: group I 66.3±6.3 kg, group II 65.9±5.7 kg) were comparable between groups. Heart rate showed significant differences between groups during laryngoscopy (group I: 94.0±5.1 vs group II: 89.4±5.2 beats/min, p-value<0.001) and at intubation (group I: 97.7±5.5 vs group II: 93.5±5.0 beats/min, p-value=0.003). Systolic blood pressure at intubation was 131.0±6.2 mmHg in group I versus 124.8±5.4 mmHg in group II (p-value<0.001). Diastolic blood pressure at intubation was 80.7±4.7 mmHg in group I versus 76.4±4.8 mmHg in group II (p-value<0.001). Mean arterial pressure at intubation was 97.4±4.7 mmHg in group I versus 92.5±4.3 mmHg in group II (p-value<0.001). Both magnesium sulphate groups showed significant attenuation of the haemodynamic stress response to laryngoscopy and intubation compared to baseline values. Group II (50 mg/kg) demonstrated greater attenuation of blood pressure responses than group I (30 mg/kg), but with a higher incidence of hypotension (20% vs 10%).

Conclusion: Both doses of magnesium sulphate effectively attenuate the haemodynamic stress response to laryngoscopy and tracheal intubation. While the 50 mg/kg dose provided better blood pressure control, the 30 mg/kg dose had a more favourable side-effect profile. The choice of dosage should be individualised based on patient characteristics and the anticipated degree of haemodynamic stress.