Efficacy of β₂-agonists in bronchiolitis: A reappraisal and meta- analysis

Objective. To evaluate the efficacy of β₂-agonists in bronchiolitis. Design. Critical review and meta-analysis of randomized controlled trials of inhaled β₂-agonists. Results. Three inpatient and five outpatient studies were identified. Inpatient studies (82 patients) were characterized by wide variability in therapeutic regimens and measurement of outcomes. Several problems were identified in the selection and specification of patients, such as failure to assess the prestudy duration of illness or to exclude patients already taking bronchodilators. Metaanalysis was not possible for inpatient trials due to the great variability in study outcomes, timing of outcome assessment, and drug regimens. Results of inpatient trials were contradictory: one found significant reductions in the clinical score and a shorter hospital stay with treatment, whereas two others found only significant oxygen desaturations. Outpatient studies (251 patients) examined immediate changes in physiologic measures and clinical scores after two treatments, but have not examined the effects of the longer-term regimen customarily used by clinicians. Meta-analysis revealed that short-term β₂- agonist therapy had no impact on the hospitalization rate or respiratory rate, and had a statistically significant but clinically insignificant impact on oxygen saturation and heart rate. The diversity of scoring systems precluded pooling of clinical score data. Conclusions. Despite eight clinical trials, conclusive evidence for the efficacy of β₂-agonist therapy for bronchiolitis remains unavailable. Well-designed inpatient trials are needed. Meta-analysis of outpatient studies does not support the use of β₂-agonist therapy for bronchiolitis, but investigators have not studied the outcomes and the long-term outpatient regimen customarily used by clinicians.