Objectives: To determine the benefit of IV β2-agonists for severe acute asthma treated in the emergency department (ED).
Methods: Randomized controlled trials were identified using EMBASE, MEDLINE, and CINAHL; the Cochrane Airways Review Group database; hand searching; bibliographies; pharmaceutical companies; and author contact. Studies where IV β2-agonists were compared to placebo and/or existing standards of care were considered. Where appropriate, trials were combined using odds ratios (ORs) or weighted mean differences with 95% confidence intervals (CIs).
Results: From 746 identified references, 55 potentially relevant articles were identified and 15 articles were included. All trials were performed outside North America and were published prior to 1997. Three main treatment strategies were reviewed: strategy 1 (three articles), IV β2-agonists with inhaled β2-agonists vs inhaled β2-agonists; strategy 2 (six articles), IV β2-agonists alone vs inhaled β2-agonists; and strategy 3 (six articles), IV β2-agonists vs IV methylxanthines. Compared to all treatments, IV β2-agonist use did not lead to clinical or statistical significant differences in vital signs, pulmonary functions, laboratory measures, adverse effects, or clinical success. Although statistically nonsignificant, seven methodologically strong studies demonstrated that peak expiratory flows and heart rates were unchanged following β2-agonist use compared to all other treatments at 60 min (8.3 L/min [95% CI, 17.6 to 34.2] and 3.65 beats/min [95% CI, 2.9 to 10.2], respectively), with an increased risk of adverse effects (OR, 1.98; 95% CI, 0.5 to 8.2).
Conclusions: Evidence is lacking to support the use of IV β2-agonists in ED patients with severe acute asthma. Moreover, the clinical benefit appears questionable, while the potential clinical risks are obvious. The only recommendations for IV β-2agonist use should be in those patients in whom inhaled therapy is not feasible, or in the context of a controlled clinical trial comparing IV β2-agonists with standard care vs standard care alone.