Effects of salmeterol on arterial blood cases in patients with stable chronic obstructive pulmonary disease - Comparison with albuterol and ipratropium

Administration of P-adrenergic agonist bronchodilators to patients with air ways obstruction commonly results in transient decreases in Pa,, levels des pite bronchodilation, an effect that has been attributed to these drugs' pu lmonary vasodilator action. We compared the acute effects on gas exchange o f salmeterol with those of albuterol and the anticholinergic agent ipratrop ium in 20 patients with stable chronic obstructive pulmonary disease (COPD) . Each agent was given in recommended dosage on separate days in a double-b lind, crossover format, and the patients' arterial blood gases (ABGs) were measured at baseline and at intervals to 120 min. Small but statistically s ignificant declines in Pa-O2 the primary outcome variable, were found after administration of both salmeterol and albuterol. The decline in Pa-O2 afte r 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 +/- S EM) at 30 min after salmeterol, and -3.45 +/- 0.92 mm Hg at 20 min after al buterol. Following ipratropium, the corresponding change was -1.32 +/- 0.85 mm Hg at 20 min. These declines, which were almost entirely attributable t o increases in the alveolar-arterial difference in oxygen tension Delta(A-a )Do(2) tended to be more marked in subjects with higher baseline Pa-O2 valu es. No subject experienced a decline in Pa-O2 to levels below 59 mm Hg. The re were no significant differences among the three drugs studied. We conclu de that despite small decreases in Pa-O2 after each of the three drugs, the declines were small, transient, and of doubtful clinical significance.