Emergency treatment of acute asthma with albuterol metered-dose inhaler plus holding chamber: how often should treatments be administered?

STUDY OBJECTIVE: To determine the optimal treatment interval for administering albuterol metered-dose inhaler (MDI) with a holding chamber to patients presenting to the emergency department (ED) with acute asthma.

DESIGN: Prospective, randomized, double-blind study.

SETTING: EDs of two affiliated teaching hospitals in the Bronx, NY.

PATIENTS: One hundred adult patients with acute asthma and FEV1 <60% predicted of normal.

INTERVENTIONS: At entry (T=0 min), eligible patients all openly received inhaled albuterol (six puffs) via MDI with a spacer. Subsequently, in a double-blind fashion, they received six puffs of albuterol or placebo with new MDIs and spacers at 30, 60, and 90 min such that group 1 (n=34) received albuterol every 30 min, group 2 (n=33) every 60 min, and group 3 (n=33) at 120 min only. FEV1 and vital signs were measured at T=0 and at 15, 30, 60, 90, and 120 min following initial treatment. Potassium levels were measured at T=0 and 120 min. Adverse events, the use of additional inhaled beta-agonists or systemic corticosteroids, and hospitalization rates were recorded.

MEASUREMENTS AND RESULTS: At T=0, the groups did not differ in age, FEV1, or prescribed asthma medications. All groups showed significant improvement in FEV1 (p<0.05; T=120 vs 0 min). The conditions of groups 1 and 2 improved significantly more than those of group 3, but did not differ compared to each other. The mean+/-SEM change in FEV1 (T=120 vs 0 min) was 0.993+/-0.108, 0.858+/-0.135, and 0.321+/-0.056 L, respectively, for the three groups. Separate analysis for patients with FEV1% <40% or >40% predicted showed similar results. However, patients who initially were low responders to albuterol treatment (<15 percentage point increase at 15 min) improved significantly with 30-min treatments compared to the other two treatment regimens. Patients who initially responded with >15 percentage point increase in FEV1 at 15 min following initial albuterol inhalation benefited equally from 30- or 60-min treatments compared to 120 min. Potassium levels did not change significantly during the study. Adverse events and hospitalization rates were equivalent. After the conclusion of the study, group 3 patients required a greater number of beta-agonist treatments prior to eventual discharge from the ED.

CONCLUSIONS: For acute asthma, albuterol MDI with a holding chamber can be given optimally at 60-min intervals with minimal adverse effects for the majority of patients. However, patients who initially demonstrate a low or poor bronchodilator response to albuterol should be given subsequent treatments at 30-min intervals. This will optimize care and conserve resources for patients who will benefit the most.