• B H Rowe, J A Bretzlaff, C Bourdon, G W Bota, and C A Camargo.
• Division of Emergency Medicine and Department of Public Health Sciences, University of Alberta, Edmonton, Alberta, Canada. brian.rowe@ualberta.ca
• Ann Emerg Med. 2000 Sep 1; 36 (3): 181-90.

Study ObjectivesThere is some evidence that magnesium, when infused into asthmatic patients, can produce bronchodilation in addition to that obtained from standard treatments. This systematic review examined the effect of intravenous magnesium sulfate used for patients with acute asthma managed in the emergency department.MethodsOnly randomized controlled trials were eligible for inclusion. Studies were included if patients presented with acute asthma and were treated with intravenous magnesium sulfate versus placebo. Trials were identified from the Cochrane Airways Review Group register, which consists of a combined search of EMBASE, MEDLINE, and CINAHL databases and hand-searching of 20 key respiratory journals. Bibliographies from included studies and known reviews were searched. Primary authors and content experts were contacted. Data were extracted and methodologic quality was assessed independently by 2 reviewers. Missing data were obtained from authors.ResultsSeven trials (5 adult, 2 pediatric) involving a total of 668 patients were included. Overall, admission to hospital was not statistically reduced using magnesium sulfate (odds ratio [OR] 0.31, 95% confidence interval [CI] 0.09 to 1.02). In the severe subgroup, admissions were reduced in those receiving magnesium sulfate (OR 0.10, 95% CI 0.04 to 0.27). Overall, patients receiving magnesium sulfate demonstrated nonsignificant improvements in peak expiratory flow rates (PEFR) when all studies were pooled (weighted mean difference [WMD] 29 L/min, 95% CI -3 to 62). In studies of patients with severe acute asthma, PEFR WMD improved by 52 L/min (95% CI 27 to 78) favoring magnesium sulfate treatment. The absolute FEV(1) also improved by 10% predicted (95% CI 4 to 16) in patients with severe acute asthma. No clinically important changes in vital signs or side effects were reported.ConclusionCurrent evidence does not clearly support routine use of intravenous magnesium sulfate in all patients with acute asthma presenting to the ED. However, magnesium sulfate appears to be safe and beneficial for patients who present with severe acute asthma. Practice guidelines need to be changed to reflect these results.

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