Objective: To characterize the dose-related effects of dobutamine on pulmonary vascular tone and associated changes in right ventricular afterload in canine microembolic lung injury .
Design: Prospective, interventional study.
Setting: University laboratory.
Subjects: Ten anesthetized and ventilated dogs.
Interventions: Right heart catheterization for the measurement of pulmonary vascular resistance by multipoint mean pulmonary artery pressure (Ppa)/cardiac output (Q) plots, partitioning of pulmonary vascular resistance by the occlusion method, and determination of pulmonary arterial input impedance from spectral analysis of Ppa and Q waves, in ten anesthetized and ventilated dogs, before and after induction of acute microembolic lung injury, and without or with 5, 10, 15, and 20 microg.kg(-1).min(-1) dobutamine.
Measurements and main results: Microembolic pulmonary hypertension was associated with a shift of Ppa/Q plots to higher pressures, a slight decrease in the arterial component of pulmonary vascular resistance, a decrease in characteristic impedance, and an increase in the pulsatile component of right ventricular hydraulic load. At baseline, dobutamine had no effect on Ppa/Q plots at 5 and 10 microg.kg(-1).min(-1) but increased Ppa at 15 and 20 microg.kg(-1).min(-1). In microembolic pulmonary hypertension, the only effect of dobutamine on Ppa/Q plots was a decrease in Ppa at 20 microg.kg(-1).min(-1). Dobutamine had no effect on the partitioning of pulmonary vascular resistance or on pulmonary arterial input impedance spectrum.
Conclusions: Dobutamine at doses up to 10 microg.kg(-1).min(-1) has no flow-independent effect on the normal or the acutely hypertensive pulmonary circulation. Higher doses may be constricting or dilating depending on preexisting tone.