Nebulised Magnesium Sulphate as an Adjunct to Standard Bronchodilator Therapy in Adults with Acute Severe Asthma: A Randomised, Double-Blind, Placebo-Controlled Trial

Abstract

Background: Acute severe asthma remains a frequent cause of emergency attendance, and a substantial proportion of patients respond incompletely to inhaled beta-2 agonists, ipratropium bromide and systemic corticosteroids. Nebulised magnesium sulphate has been proposed as an inexpensive adjunct that acts directly at the airway smooth muscle, but the reported evidence has been inconsistent. The present trial evaluated whether the addition of nebulised magnesium sulphate to standard therapy improved airflow obstruction and reduced hospital admission in adults with acute severe asthma. Methods: A randomised, doubleblind, placebo-controlled trial was conducted in the emergency department of a tertiary care teaching hospital over 18 months. One hundred adults aged 18 to 60 years with acute severe asthma and a peak expiratory flow rate below 50% of predicted were randomised in a 1:1 ratio. Group A received three doses of nebulised isotonic magnesium sulphate (500 mg in 2.5 mL) and Group B received 2.5 mL of nebulised 0.9% saline, each combined with salbutamol and ipratropium bromide at 20-minute intervals. All patients received intravenous hydrocortisone. The primary outcome was the change in peak expiratory flow rate expressed as percentage predicted at 240 minutes. Secondary outcomes included forced expiratory volume in one second, Borg dyspnoea score, hospital admission, emergency department length of stay and adverse events. Results: The two groups were comparable at baseline. The mean improvement in peak expiratory flow rate at 240 minutes was 34.2 ± 9.8% predicted in Group A and 26.9 ± 10.4% predicted in Group B (mean difference 7.3, 95% confidence interval 3.3 to 11.3; p < 0.001). Hospital admission occurred in 11 (22.0%) and 21 (42.0%) patients respectively (p = 0.032). Mean emergency department stay was shorter in Group A (5.8 ± 1.9 versus 7.2 ± 2.4 hours; p = 0.002). Adverse events were minor and comparable between groups. Conclusion: Nebulised magnesium sulphate added to standard bronchodilator therapy produced a modest but statistically significant improvement in airflow obstruction and reduced hospital admission in adults with acute severe asthma, with the greatest benefit in the most severely obstructed patients.