Pulmonary hemodynamic response to dopamine and dobutamine in hyperoxic and in hypoxic dogs.

The pulmonary hemodynamic response to dopamine and to dobutamine was investigated in dogs ventilated with hyperoxia (fraction of inspired O2 concentration [FIO2], 0.4 balance nitrogen) and challenged with short periods of inspiratory hypoxia (FIO2 0.125 or 0.1 for 10 min). Dopamine at doses of 5, 10, and 20 micrograms X kg-1 X min-1 (n = 7 dogs) increased cardiac index (CI) and pulmonary artery pressure (PAP) without change in indexed pulmonary vascular resistance (PVRI) at both FIO2 0.4 and 0.125. Hypoxia-induced increases in PVRI were unaffected by dopamine. Dobutamine at doses of 5, 10, and 20 micrograms X kg-1 X min-1 (n = 7 dogs) increased CI, with an increase in PAP without change in PVRI at FIO2 0.4, and at FIO2 0.125 there was no change in PAP and a decrease in PVRI. Hypoxia-induced increases in PVRI were inhibited by dobutamine, partially at 5 and 10 micrograms X kg-1 X min-1, and completely at 20 micrograms X kg-1 X min-1. In two additional groups of seven dogs the effects of reducing FIO2 from 0.4 to 0.1 without and with dopamine or dobutamine either at 10 micrograms X kg-1 X min-1 (n = 7) or at 20 micrograms X kg-1 X min-1 (n = 7) were studied at an unchanged CI obtained by stepwise inflations of a balloon placed in the inferior vena cava. At constant flow both amines increased PVRI at FIO2 0.4 and did not significantly affect hypoxia-induced increases in PVRI.(ABSTRACT TRUNCATED AT 250 WORDS)