Intravenous magnesium sulfate as an adjunct in the treatment of acute asthma.

STUDY OBJECTIVE: This study was conducted to determine whether intravenous magnesium sulfate (MgSO4), when used as part of a standardized treatment protocol, can improve pulmonary function and decrease admission rate in patients presenting to the emergency department with exacerbations of asthma.

DESIGN: In this randomized double-blind placebo-controlled study, patients with acute asthma were treated with inhaled beta-agonists at regular intervals and intravenous (IV) steroids. At 30 min after entry, patients received either 2 g IV MgSO4 or IV placebo. Patients were monitored for up to 4 h with regular measurements of pulmonary function. Patients who were discharged from the emergency department were contacted at 1 day and 7 days for follow-up.

SETTING: Emergency departments of a university-affiliated, voluntary hospital and municipal hospital.

PARTICIPANTS: Asthmatics aged 18 to 65 years during acute exacerbation with FEV1 less than 75% predicted both before and after a single albuterol treatment.

INTERVENTIONS: Patients were given 2 g of MgSO4 or placebo as an adjunct to standardized emergency department procedure for acute asthma.

MEASUREMENTS AND RESULTS: One hundred thirty-five patients were studied. Hospital admission rates were 35.3% for placebo-treated group and 25.4% for the magnesium-treated group (p = 0.21). FEV1 measured at 120 min was 56% predicted for the placebo-treated group and 55% predicted for the magnesium-treated group. (p = 0.92) For subgroup analysis, patients were divided into "severe" (baseline FEV1 < 25% predicted on presentation) or "moderate" (baseline FEV1, 25 to 75% predicted on presentation). For the severe group, admission rates were 78.6% (11/14) for the placebo-treated group and 33.3% (7/21) for the magnesium-treated group (p = 0.009). For the moderate patients, admission rates were 22.4% (11/49) for the placebo-treated group and 22.2% (10/25) for the magnesium-treated group (p = 0.98). There was no significant improvement in FEV1 in the moderate group for magnesium-treated patients. However, in the severe group, there was a significant improvement in FEV1 at 120 min and 240 min (p = 0.014 and 0.026, respectively).

CONCLUSION: Intravenous MgSO4 decreased admission rate and improved FEV1 in patients with acute severe asthma but did not cause significant improvement in patients with moderate asthma.