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Three Part Question

In [children with status asthmaticus] does [acute administration of intravenous magnesium sulphate] [reduce hospital admission rate]?

Clinical Scenario

Jimmy was in the emergency department (ED) with his third severe asthma attack of the winter. He could tell he was going to be admitted ... again. He was not improving much after one hour on continuous nebulised albuterol and intravenous steroids. The new paediatric registrar was running around asking for the magnesium. The senior consultant looked at him like he was a misplaced obstetrician. What evidence did he have to suggest magnesium might make Jimmy better and prevent admission?

Search Strategy

Cochrane and Medline
Medline- {"magnesium" AND "asthma" AND "child" AND [(double and blind) or placebo]}

Search Outcome

Cochrane Database of Systematic Reviews-none with children
Medline - 18 hits of which 4 were pertinent. One additional meta-analysis was identified; hospital admission rate was not assessed as an outcome

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Devi 1997 India	47 children in ED with severe status asthmaticus	RCT (level 1b)	Admission to hospital	ARR 0.34 (95% CI 0.07 to 0.61); NNT 3 (95% CI 2 to 14)	0.2cc/kg 50% MgSO4 given
Scarfone et al 2000 USA	54 children in ED with moderate status asthmaticus	RCT (level 1b)	Admission to hospital	ARR 0.07 (95% CI 0.2 to 0.34). NNT 14 (95% CI 3 to 8: NNH 8 to 5)	75 mg/kg MgSO4 (max 2.5mg)
Ciarallo et al 1996 USA	31 in ED with moderate to severe status asthmaticus	RCT (level 1b)	Admission to hospital	ARR 0.27 (95% CI 0.05 to 0.49). NNT 4 (95% CI 2 to 19)	25mg mg/kg MgSO4 (max 2 g)
Ciarallo et al 2000 USA	30 children in ED with moderate to severe status asthmaticus	RCT (level 1b)	Admission to hospital	ARR 0.5 (95% CI 0.24 to 0.76). NNT 2 (95% CI 1 to 4)	40 mg/kg MgSO4 (max 2 g)

Comment(s)

Three of these four studies of intravenous MgSO, in paediatric ED patients with moderate-severe status asthmaticus showed significant reduction in hospitalisation rates compared to controls. (A formal meta-analysis of these trials would give a better quality answer than to simply add up study numbers.) These patients had all already been treated with maximal inhaled P agonist therapy and corticosteroids. The rough similarity of the asthma response rate (ARR) in the three positive trials suggests a real and clinically significant improvement in an obvious clinical endpoint-hospitalisation. MgSO, is easy to administer, can be used in conjunction with other therapies, and appears to show a clinical effect within one to two hours. The Cochrane review combines adults and children, was performed before two of the studies (the Scarfone and 2nd Ciarallo papers) appeared, and did not separate out children in a subgroup analysis in terms of hospitalisation rates (Rowe et al, 2000). The other systematic review (Alter et al, 2000) did not evaluate hospital admission as an outcome measure. Though difficult to compare severity of patients across studies, all patients were "moderately to severely" affected and very likely to require hospitalisation. Furthermore, given the low cost and lack of any side effects noted across the studies (it will of course take thousands of patients studied to confidently conclude a drug is "safe"), intravenous magnesium may be indicated in paediatric refractory status asthmaticus. A formal systematic review of these studies is needed.

Clinical Bottom Line

Magnesium sulphate may reduce hospitalisation rates of paediatric patients with severe status asthmaticus (NNT -3). The most severely affected patients stand to benefit the most; MgSO, should be considered in refractory patients with impending respiratory failure.

References

1. Rowe BH, Bretzlaff JA, Bourdon C, et al. Magnesium sulfate for treating exacerbations of acute asthma in the emergency department. Cochrane Database Syst Rev 2000;2:CDOO1 490.
2. Alter HJ, Koepsell TD, Hilty WM. Intravenous magnesium as an adjuvant in acute bronchospasm a meta-analysis. Ann Emerg Med 2000;36(3):191-7.
3. Devi PR, Kumar L, Singhi SC, et aL. Intravenous magnesium sulfate in acute severe asthma not responding to conventional therapy. Indian Pediatr 1997;34(5):389-97.
4. Scarfone RJ, Loiselle JM, Joffe MD, et al. A randomized trial of magnesium in the emergency department treatment of children with asthma. Ann Emerg Med 2000;36(6):572-8.
5. Ciarallo L, Sauer AH, Shannon MW. Intravenous magnesium therapy for moderate to severe pediatric asthma: results of a randomized, placebo-controlled trial. J Pediatr 1996;129(6):809-14.
6. Ciarallo L, Brousseau D, Reinert S. Higher-dose intravenous magnesium therapy for children with moderate to severe acute asthma. Arch Pediatr Adolesc Med 2000; 154(10):979-83.