VENTILATION-PERFUSION RESPONSE AFTER FENOTEROL IN HYPOXEMIC PATIENTS WITH STABLE COPD

Background: The effects of vasoactive drugs, including bronchodilators , on vascular and pulmonary dynamics are interrelated, complex and dif ficult to measure, but important because of potential deleterious effe cts on gas exchange. Methods: To assess the effects of fenoterol at bo th high and low dose on pulmonary gas exchange in 24 hypoxemic patient s with stable COPD: fenoterol, 5 mg; fenoterol, 1 mg and ipratropium b romide, 0.5 mg; ipratropium bromide, 0.5 mg; or matched placebo were n ebulized in a double-blind, placebo-controlled fashion. Spirometry, ve ntilation, systemic hemodynamics, and respiratory and inert gases were measured before and 15, 60, and 120 min after each treatment. Results : Compared with placebo, heart rate (p<0.002) and cardiac output (p=0. 05) increased after high-dose fenoterol therapy to return to baseline values by 120 min, Following fenoterol at high dose, mean maximum PaO2 change from baseline decreased by 6.3+/-1.1 mm Hg (SD) and both alveo lar-arterial oxygen pressure difference (P[A-a]O-2), by 8.3+/-4.0 mm H g, and ventilation-perfusion (V over dot A/Q over dot) mismatching inc reased, as evidenced by increments of the dispersion of pulmonary bloo d now, without reaching significance; likewise, low-dose fenoterol the rapy increased V over dot A/Q over dot inequalities while both PaO2 an d P(A-a)O-2 remained unchanged. Conclusions: In this population of COP D patients, high-dose fenoterol therapy did not significantly increase heart rate and cardiac output resulting in minor adverse consequences on arterial oxygenation and V over dot A/Q over dot relationships.