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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?
Structured clinical question
In children with status asthmaticus [patient] does acute administration of intravenous magnesium sulphate [intervention] reduce hospital admission rate [outcome]?
Search strategy and outcome
Cochrane Database of Systematic Reviews—none with children (1). Medline—“magnesium” AND “asthma” AND “child” AND [(double and blind) or placebo]—four pertinent trials in 18 hits. One additional meta-analysis was identified; hospital admission rate was not assessed as an outcome (2). See table 2.
Three of these four studies of intravenous MgSO4 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 β 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. MgSO4 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; MgSO4 should be considered in refractory patients with impending respiratory failure.
Citation Study group Study type (level of evidence) Outcome Key results Comments
Deviet al (1997) 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) 0.2 cc/kg 50% MgSO4 given Scarfone et al (2000) 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 2.5 g) Ciarallo et al (1996) 31 children 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) 25 mg/kg MgSO4 (max 2 g) Ciarallo et al (2000) 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) .
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