IV Magnesium Sulfate in the Treatment of Acute Severe Asthma

Abstract & Commentary

Synopsis: The end point of FEV1 at 240 minutes favored the use of MgSO4 for the most severe group.

Source: Silverman RA, et al. Chest. 2002;122:489-497.

Silverman and colleagues used the emergency departments in 8 hospitals to assess the role of MgSO4 in acute asthma in a sizeable number of patients (n = 248). They segregated their findings by severity of asthma. Those with less than 25% of predicted FEV1 on admission had a statistically significant favorable outcome of predicted FEV1, and had results similar to placebo. They did not include pediatric patients, and continued the nebulized albuterol and IV methylprednisolone, in addition to the 2 g of magnesium that was administered 30 minutes after arrival in the emergency department. However, the end point of FEV1 at 240 minutes favored the use of MgSO4 for the most severe group.

Comment by Sheldon L. Spector, MD, FACP, FAAA, FACA

Variables that have contributed to the controversy regarding MgSO4 in the literature include: 1) the age of the patients who were studied; 2) initial pulmonary function at the time of arrival in the emergency room; 3) dose of MgSO4 used; 4) route of administration; 5) end point results; 6) the number of patients included in the study; and 7) type of blinding and randomization. Although the majority of trials included adult patients, a few were conducted in the pediatric age group. In fact, 4 trials using pediatric patients support the use of MgSO4 in asthma,1-4 and one does not.5 In pediatric studies, a weight-based dosing regimen was usually done and this regimen varied from 25-100 mg/kg.

Some published case reports included asthmatic patients who failed to respond to traditional treatments such as albuterol, aminophylline, and corticosteroids. The mechanism of action of magnesium in alleviating an asthmatic attack is unknown. However, the ability of magnesium to impede movement of calcium and decrease the uptake of calcium by the bronchial smooth muscle is associated with bronchodilatation and inhibition of degranulization of mast cells. Since calcium also has a role in triggering the release of thromboxane and leukotrienes, it may antagonize these mediators, as well. The possibility that magnesium deletion may actually occur with adrenergic excess is another hypothesis. Side effects reported with MgSO4 included flushing or facial warmth; dry mouth; and fatigue. With rapid infusions, bradycardia and hypotension have occurred.

This study contributes to our knowledge regarding which subgroup of severe asthmatic patients might best respond to MgSO4, ie, with an FEV1 of less than 25% when first seen. The literature might also favor its use in the pediatric population, although more studies are needed.

Dr. Spector, Clinical Professor, Department of Medicine, UCLA School of Medicine, Los Angeles, is Associate Editor of Internal Medicine Alert.

References

1. Ciarallo L, Sauer AH, Shannon MW. J Pediatr. 1996; 129:809-814.

2. Devi PR, et al. Indian Pediatr. 1997;34:389-397.

3. Gurkan F, et al. Eur J Emerg Med. 1999;6:201-205.

4. Ciarallo L, Brousseau D, Reinert S. Arch Pediatr Adolesc Med. 2000;154:979-983.

5. Scartone RJ, et al. Ann Emerg Med. 2000;36:572-578.