First-line therapy for acute asthma attacks includes inhaled beta-agonist bronchodilators and corticosteroids. In severe asthma attacks, inhaled beta agonists may not penetrate the small airways, and response to the inhaled medication may be a result of the medication reaching the receptor sites through systemic circulation. It has been speculated that if the airways respond to inhaled beta agonists in this fashion, intravenous administration of the medication may provide an earlier response. Current clinical practice guidelines from Europe, Canada, and the United States suggest that beta agonists can be administered intravenously or subcutaneously as second-line therapy for acute asthma attacks in patients who do not respond to inhaled bronchodilators or systemic corticosteroids or if the inhaled route is not practical. The intravenous alternative is reserved for “near-death asthma” or “life-threatening asthma” by the various groups. However, these recommendations are based on limited studies, and the efficacy of intravenous administration in patients with acute asthma is currently under debate. Travers and colleagues reviewed evidence from randomized trials that support the use of intravenous beta agonists in patients with severe acute asthma.

The study was a meta-analysis of all randomized or quasi-randomized controlled trials of the use of intravenous beta agonists in the treatment of severe asthma attacks. The study population consisted of adult patients or children who presented to the emergency department with severe acute asthma attacks. All appropriate literature bases were searched for studies that met the inclusion criteria. Quality evaluation was performed, and data were extracted from the studies.

Of the 746 trials that met the inclusion criteria, 15 were included in the analysis. The trials used three different strategies: intravenous beta agonists with inhaled beta agonists versus inhaled beta agonists; intravenous beta agonists alone versus inhaled beta agonists; and intravenous beta agonists versus intravenous methylxanthines. The outcomes reviewed in the studies included pulmonary function, laboratory measures, adverse effects, clinical success, and vital signs. The meta-analysis did not show any statistical or clinical improvement in any of the variables. Seven methodologically strong trials did not show any change in heart rate or improvement of pulmonary function but did show an increased risk of adverse effects that did not reach clinical significance.

The authors conclude that the evidence for use of intravenous beta-agonist medications in severe asthma attacks is lacking. They add that the clinical benefit appears to be questionable, and the potential risk for adverse effects is evident. They state that intravenous beta-agonist medication should be used clinically only in patients who are not candidates for inhaled beta-agonist therapy.