Intravenous beta agonist in severe acute asthma

Abstract

Study objective: To determine whether salbutamol is more effective in treating severe asthma when given intravenously or by inhalation.

Design: Randomised trial of short term response to intravenous versus nebulised salbutamol in acute severe asthma.

Setting: District general hospital (secondary care centre).

Participants: 76 patients aged 16-70 admitted to hospital with acute severe asthma (peak expiratory flow rate less than 50% of predicted) during study period. Five withdrawn because of adverse effects of treatment or non-response. Of remaining 71, 34 allocated to nebuliser group and 37 to intravenous treatment group. Patients with history of cardiovascular disease or recent corticosteroid or intravenous bronchodilator treatment excluded. Admission characteristics similar in the two groups.

Interventions: All patients given 5 mg nebulised salbutamol on admission before randomisation plus 200 mg hydrocortisone bolus intravenously and 35% inspired oxygen throughout. Nebuliser group received two more 5 mg doses of nebuliser salbutamol at 30 minutes and 2 hours; intravenous group received 4 hours' continuous salbutamol infusion (12 micrograms/min) starting at 30 minutes plus supplementary intravenous potassium chloride. No other bronchodilators used.

Endpoint: Change in peak expiratory flow rate over 4 hours.

Measurements and main results: Peak expiratory flow rate improved more in intravenous group (25.2%) than in nebuliser group (14.3%) (p less than 0.01, 95% confidence interval 2.4 to 19.1%). Tachycardia caused two withdrawals from intravenous group; non-response caused three withdrawals from nebuliser group.

Conclusions: Intravenous salbutamol is more effective than nebulised salbutamol in acute severe asthma but may have unacceptable cardiovascular effects.