Air-driven nebulised high-dose salbutamol in severe chronic obstructive airways disease: is it safe?

The increasing use of air-driven nebulised bronchodilators by patients with airflow obstruction has raised concern about the safety of this practice. We have investigated the effects of 10 mg salbutamol, nebulised in air, on blood gas tensions, heart rate and plasma potassium (K+), when administered alone to 9 patients with severe chronic obstructive airway disease and then in combination with a therapeutic dose of oral sustained-release theophylline to 5 of them on 2 separate occasions. No significant reductions in PaO2 were observed with either treatments. Heart rate increased significantly from 77.8 +/- 3.7 beats/min (mean +/- s.e.m.) at baseline to a peak of 87.1 +/- 4.4 beats/min at 45 min (p less than 0.001) with salbutamol alone and there was a similar trend of increase after combined therapy. K+ decreased significantly from a baseline of 4.0 +/- 0.3 to a minimum of 3.6 +/- 0.2 mmol/l at 90 min (p less than 0.001) with combined therapy but did not change significantly with single therapy. No subject developed any significant cardiac arrhythmias on either occasion. Although the number of subjects studied is small, our data suggest that air-driven nebulised high-dose salbutamol may be safe in the treatment of severe chronic obstructive airway disease but when combined with oral theophylline, a significant fall in plasma potassium may occur. This could be of clinical significance in hypokalaemic patients. When combination treatment is used, monitoring of plasma potassium is recommended.