Magnesium sulfate is effective for severe acute asthma treated in the emergency department

QUESTION

What is the effectiveness of intravenous magnesium sulfate in patients with acute asthma who were treated in the emergency department?

DATA SOURCES

Studies were identified from the Cochrane Airways Review Group Register, MEDLINE, EMBASE/Excerpta Medica, CINAHL (Cumulative Index to Nursing and Allied Health), and the Cochrane Library. We also manually searched 20 high-quality respiratory journals and bibliographies of relevant articles and contacted authors and content experts.

STUDY SELECTION

Studies were selected if they were randomized controlled trials or quasi-randomized trials, included adults or children seen at an emergency department with acute asthma, and compared the use of intravenous magnesium sulfate with placebo.

DATA EXTRACTION

Data on study and patient characteristics, hospital admissions, pulmonary function, vital signs, and adverse events were extracted.

MAIN RESULTS

We reviewed 27 studies for inclusion, and 7 trials (665 patients; 5 trials of adult and 2 of pediatric patients, with 6 from the United States and 1 from India) met the inclusion criteria. Analyses of all patients and of patients with severe asthma showed a reduction in hospital admission rates (table), whereas no difference was shown for patients with mild to moderate asthma. Studies that included all patients showed no differences in measures of pulmonary function (peak expiratory flow rate or forced expiratory volume in 1 second) or vital signs (heart rate, respiratory rate, or blood pressure). In studies of patients with severe asthma, the peak expiratory flow rate improved by 52 L/min (95% confidence interval 27-78 L/min; 3 studies) and the forced expiratory volume in 1 second by 8% of the predicted value (95% confidence interval 5%-12%; 3 studies). Data were insufficient to assess adverse events.

Table 1.

Magnesium sulfate vs placebo for hospital admissions among patients with acute asthma at end of study^*

	Weighted event rates		Relative risk reduction (95% CI)	Number needed to treat (CI)
Patients	Magnesium sulfate	Placebo
All	23%	45%	30% (2 to 49)	5 (3 to 63)
Severe asthma	51%	91%	44% (29 to 56)	3 (2 to 4)

^*Relative risk reduction, 95% confidence interval, and number needed to treat calculated from data in article

CONCLUSION

The use of intravenous magnesium sulfate reduces the rate of hospital admissions and improves pulmonary function in patients with severe acute asthma treated in the emergency department.