The quality of evidence is downgraded by study limitations (unclear allocation concealment), by inconsistency (variability in results), and by imprecise results (few patients and wide confidence intervals).
A Cochrane review [Abstract] 1 included 25 studies with a total of 2 907 subjects. Nine of the 25 studies involved adults, 4 included adult and paediatric patients, 8 paediatric patients, and in 4 studies the age of participants was not stated. The design, definitions, intervention and outcomes were different in all 25 studies.
Inhaled magnesium sulfate in addition to inhaled β2-agonist and ipratropium (7 studies):Some individual studies reported improvement in lung function indices favouring the intervention group, but results were inconsistent overall and the largest study found no between-group difference at 60 minutes. Admissions to hospital at initial presentation may be reduced by the addition of inhaled magnesium sulfate (RR 0.95, 95% CI 0.91 to 1.00, statistical heterogeneity I² = 52%; 4 studies, n=1 308) but no difference was detected for re-admissions or escalation of care to ITU/HDU. Serious adverse events during admission were rare. There was no difference between groups for all adverse events during admission (RD 0.01, 95% CI −0.03 to 0.05; 2 studies, n=1 197).
Inhaled magnesium sulfate in addition to inhaled β2-agonist (13 studies): Although some individual studies reported improvement in lung function indices favouring the intervention group, none of the pooled results showed a conclusive benefit as measured by FEV1 or predicted peak expiratory flow rate (PEFR). Pooled results for hospital admission showed a point estimate that favoured the combination of MgSO4 and β2-agonist, but it was not statistically significant (RR 0.78, 95% CI 0.52 to 1.15; 6 studies, n=375). There were no serious adverse events reported by any of the included studies and no between-group difference for all adverse events (RD −0.01, 95% CI −0.05 to 0.03; 5 studies, n=694).
Inhaled magnesium sulfate versus inhaled β2-agonist (4 studies): Two studies reported a benefit of β2-agonist over MgSO4 alone for PEFR and 2 studies reported no difference; the results were not pooled. Admissions to hospital were only reported by 1 small study and events were rare, leading to an uncertain result. No serious adverse events were reported in any of the studies; 1 small study reported mild to moderate adverse events but the result was imprecise
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