Inhaled magnesium sulfate in the treatment of acute asthma

Background Asthma exacerbations can be frequent and range in severity from mild to life‐threatening. The use of magnesium sulfate (MgSO₄) is one of numerous treatment options available during acute exacerbations. While the efficacy of intravenous MgSO₄ has been demonstrated, the role of inhaled MgSO₄ is less clear. Objectives To determine the efficacy and safety of inhaled MgSO₄ administered in acute asthma. Specific aims: to quantify the effects of inhaled MgSO₄ I) in addition to combination treatment with inhaled β₂‐agonist and ipratropium bromide; ii) in addition to inhaled β₂‐agonist; and iii) in comparison to inhaled β₂‐agonist. Search methods We identified randomised controlled trials (RCTs) from the Cochrane Airways Group register of trials and online trials registries in September 2017. We supplemented these with searches of the reference lists of published studies and by contact with trialists. Selection criteria RCTs including adults or children with acute asthma were eligible for inclusion in the review. We included studies if patients were treated with nebulised MgSO₄ alone or in combination with β₂‐agonist or ipratropium bromide or both, and were compared with the same co‐intervention alone or inactive control. Data collection and analysis Two review authors independently assessed trial selection, data extraction and risk of bias. We made efforts to collect missing data from authors. We present results, with their 95% confidence intervals (CIs), as mean differences (MDs) or standardised mean differences (SMDs) for pulmonary function, clinical severity scores and vital signs; and risk ratios (RRs) for hospital admission. We used risk differences (RDs) to analyse adverse events because events were rare. Main results Twenty‐five trials (43 references) of varying methodological quality were eligible; they included 2907 randomised patients (2777 patients completed). Nine of the 25 included studies involved adults; four included adult and paediatric patients; eight studies enrolled paediatric patients; and in the remaining four studies the age of participants was not stated. The design, definitions, intervention and outcomes were different in all 25 studies; this heterogeneity made direct comparisons difficult. The quality of the evidence presented ranged from high to very low, with most outcomes graded as low or very low. This was largely due to concerns about the methodological quality of the included studies and imprecision in the pooled effect e