Am. J. Respir. Crit. Care Med., Volume 160, Number 3, September 1999, 1028-1030

Effects of Salmeterol on Arterial Blood Gases in Patients with Stable Chronic Obstructive Pulmonary Disease
Comparison with Albuterol and Ipratropium

GHASSAN KHOUKAZ and NICHOLAS J. GROSS

Division of Pulmonary and Critical Medicine, Hines Veterans Affairs Hospital, Hines; and Department of Medicine, Stritch School of Medicine, Loyola University of Chicago, Maywood, Illinois

Administration of -adrenergic agonist bronchodilators to patients with airways obstruction commonly results in transient decreases in Pa_O2 levels despite bronchodilation, an effect that has been attributed to these drugs' pulmonary vasodilator action. We compared the acute effects on gas exchange of salmeterol with those of albuterol and the anticholinergic agent ipratropium in 20 patients with stable chronic obstructive pulmonary disease (COPD). Each agent was given in recommended dosage on separate days in a double-blind, crossover format, and the patients' arterial blood gases (ABGs) were measured at baseline and at intervals to 120 min. Small but statistically significant declines in Pa_O2, the primary outcome variable, were found after administration of both salmeterol and albuterol. The decline in Pa_O2 after salmeterol was of lesser magnitude but was more prolonged than that after albuterol, the greatest mean change being 2.74 ± 0.89 mm Hg (mean ± SEM) at 30 min after salmeterol, and 3.45 ± 0.92 mm Hg at 20 min after albuterol. Following ipratropium, the corresponding change was 1.32 ± 0.85 mm Hg at 20 min. These declines, which were almost entirely attributable to increases in the alveolar-arterial difference in oxygen tension (A-a)DO₂ tended to be more marked in subjects with higher baseline Pa_O2 values. No subject experienced a decline in Pa_O2 to levels below 59 mm Hg. There were no significant differences among the three drugs studied. We conclude that despite small decreases in Pa_O2 after each of the three drugs, the declines were small, transient, and of doubtful clinical significance.

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