Effect of dopamine infusion on pulmonary gas exchange in lambs.

We studied the effects of dopamine HCl, a potent vasoactive catecholamine, on ventilation-perfusion matching and pulmonary hemodynamics in infant lambs breathing room air and a hypoxic gas mixture. Neither alveolar hypoxia alone, nor dopamine infusion alone during room air breathing, significantly altered the ventilation-perfusion (VA/Q) distribution or intrapulmonary shunt size. Dopamine infusion during room air breathing did increase pulmonary blood flow (PBF; p less than 0.05). Dopamine infusion plus alveolar hypoxia was associated with a significant increase in minute ventilation, PBF, and pulmonary arterial pressure (Ppa), a doubling (p less than 0.01) of the fraction of PBF to low VA/Q lung regions, and a significant increase (p less than 0.05) in intrapulmonary shunt when compared to results obtained during hypoxic gas breathing without dopamine infusion. We conclude the dopamine infusion increased PBF during room air breathing, and perturbed ventilation-perfusion matching and increased Ppa and minute ventilation with no net change in arterial pO2 during the breathing of a hypoxic gas mixture.