Five RCTs were included in the review with 374 participants. The mean sample size was 75 patients.
All studies were of good quality, scoring greater than or equal to 0.7, with a kappa value of 0.90 for inter-rater agreement.
The overall pooled ES for pulmonary function in 4 studies was statistically non significant (ES 0.02, 95% CI: -0.20, +0.24). Homogeneity was also statistically non significant (chi-squared =4.12, P>0.3).
The sensitivity analysis did not alter the results significantly in terms of methodological quality, study size and therapeutic protocol. In addition, it provided no evidence of systematic bias. Pooled results revealed that MgSO4 did not reduce admission rates significantly (OR 0.68, 95% CI: 0.41, 1.15, Z-statistic=1.35, P=0.18). The authors state that the test of homogeneity was also not statistically significant (chi-squared=6.15, P=0.1), although a P-value of 0.1 is deemed to be statistically significant by some research groups. Further analysis showed that the distribution of admission rate was skewed owing to a small number of patients with unusually high admission rates. Excluding those patients produced an OR of 0.83 (95% CI: 0.29, 1.38). There was insufficient information to pool other outcomes such as blood-pressure, heart rate or side-effects ratio.
Weak correlations were found between ES and quality (rho=-0.35, P=0.5), ES and year of publication (rho=-0.43, P=0.39), and quality and year (rho=0.30, P=0.6).
Side-effects: in one trial minor side-effects such as flushing, mild fatigue, and burning at the intravenous site, were noted in 58% of patients who received MgSO4.