Five randomised placebo-controlled trials (RCTs; n=182) were included.
All 5 included trials were judged to be of good quality: four were awarded a score of 4, while the fifth was awarded the maximum score of 5.
Magnesium sulphate was shown to significantly reduce the incidence of hospitalisation in paediatric acute asthma compared with placebo (OR 0.29, 95% CI: 0.14, 0.59, P<0.006), based on 4 RCTs. There was no evidence of statistical heterogeneity (P=0.13). The ARR for hospitalisation was 0.26 (95% CI: 0.12, 0.39, P=0.0001) and the NNT to avoid hospitalisation was 4 (95% CI: 3, 8). None of the included trials assessed the rate of ICU admission.
A significant reduction in persistent PEFR less than 60% was shown with magnesium sulphate compared with placebo (OR 0.16, 95% CI: 0.06, 0.42, P=0.0003), based on 3 RCTs. There was no evidence of statistical heterogeneity (P=0.97).
Significant improvements in PEFR (mean difference 8.58, 95% CI: 0.94, 16.22, P=0.028; based on 3 RCTs) and clinical symptoms (mean difference 1.33, 95% CI: 0.31, 2.36, P=0.011; based on 4 RCTs) were shown for magnesium sulphate compared with placebo, although significant statistical heterogeneity was found in both analyses (P<0.0001 and P=0.0001, respectively).
No subgroup analysis was carried out for age (stratified outcome data not available), severity of asthma (lack of variation in the included population: all patients had moderate to severe asthma), or dosage (no study compared the effectiveness of different doses). A sensitivity analysis according to trial quality was not performed because the included trials were of similar quality. Possible areas of heterogeneity were highlighted in supplemental tables, available on the journal's website (accessed 06/11/2006). See Web Address at end of abstract.
The funnel plot indicated possible publication bias in favour of the intervention.