Background Intravenous magnesium sulfate, a rescue therapy added to combined bronchodilator and systemic steroid therapy for moderate and severe asthma, is uncommonly administered. We hypothesised that nebulized magnesium sulfate would confer benefit without undue risk.
Methods Patients aged 2 to 14 y with moderate and severe status asthmaticus (PRAM severity score >4) admitted to infirmary care were randomised double-blind to 800 mg nebulized magnesium sulfate or normal saline placebo via Aeroneb Pro and Idehaler, after intensive therapy with combined albuterol-ipratropium and intravenous methylprednisolone. Time to medical readiness for discharge was the primary outcome; sample size was chosen to detect a 10% improvement. Improvement over time in PRAM severity score and other secondary outcomes were compared for the overall group and severe asthma subset.
Results 191 magnesium sulfate and 174 placebo patients met criteria for analysis. The groups were similar with mean baseline PRAM scores >7. Blinded active therapy significantly increased blood magnesium level 2 h post-treatment 0.85 (SD 0.07) vs 0.82 (SD 0.06) mmol/L, p = 0.001). There were no important adverse effects. However, accelerated failure time analysis showed a non-significantly shortened time to medical readiness for discharge of 14% favouring the magnesium sulfate group, OR=1.14, 95% CI 0.93 to 1.40, p = 0.20. Mean times until readiness for discharge were 14.6 h [SD 9.7] vs 15.6 h [SD 11.3] for the investigational and placebo groups, respectively, p = 0.9.