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Am Fam Physician. 2002;66(12):2324

Each year in the United States, acute asthma attacks account for approximately 1.8 million visits to emergency departments. Approximately 500,000 patients are hospitalized each year with the diagnosis of asthma. The mainstay of current therapy for patients with acute asthma is beta agonists and systemic steroids. Beta agonists provide an immediate response, while systemic steroids take several hours to improve pulmonary function. Recent studies have found that intravenous magnesium sulfate may be an effective and safe adjuvant in the treatment of acute asthma attacks. Some studies have shown that intravenous magnesium sulfate may benefit patients with severe asthma but not those with mild to moderate asthma. Silverman and associates studied the effectiveness of intravenous magnesium sulfate as an adjuvant in the treatment of patients with severe acute asthma.

The trial was a placebo-controlled, double-blind, randomized clinical trial undertaken in the emergency departments of eight hospitals. Patients who presented to these emergency departments with acute asthma were included if they were between 18 and 60 years of age and had a forced expiratory volume in one second (FEV1) that was no more than 30 percent predicted. All patients received nebulized albuterol at regular intervals and intravenous methylprednisolone. Thirty minutes after arrival in the emergency department, the patients were randomized to receive 2 g of intravenous magnesium sulfate or placebo. The main outcome measure was theFEV1 at 240 minutes. Intent to treat was also analyzed at 240 minutes.

There were 248 patients who met the inclusion criteria for the study. The mean FEV1 on arrival at the emergency department was 23 percent predicted. At 240 minutes, patients who received intravenous magnesium sulfate had a significant improvement in FEV1 compared with the placebo group. The effectiveness of the intravenous magnesium was greater in patients with a lower FEV1 on admission to the emergency department. If the initial FEV1 was less than 25 percent predicted, there was a substantial improvement of FEV1 in patients treated with magnesium. The use of intravenous magnesium sulfate did not affect the hospital admission rate.

The authors conclude that intravenous magnesium sulfate improves pulmonary function when used as an adjuvant to asthma therapy in patients with severe acute asthma. They believe that the use of magnesium should be considered in the treatment of acutely ill patients with severe airway obstruction.

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