Effect of vasodilator treatment on the resolution of oleic acid injury in dogs.

Diffuse pulmonary injury is accompanied by reduction of blood flow to injured areas because of local pulmonary vasoconstriction, vascular thrombosis, and vascular obliteration. To assess whether reduced pulmonary arterial blood flow might produce relative ischemia in injured areas and consequent potentiation of the injury, we studied the effects of vasodilator treatment in a dog model of diffuse alveolar damage. Twenty-five awake dogs with arterial and pulmonary arterial catheters in place were given 0.08 ml/kg oleic acid, a dose that produces a diffuse lung injury that largely resolves over a 1-wk period. Ten of the animals were treated with minoxidil, a potent vasodilator and inhibitor of hypoxic pulmonary vasoconstriction. Observations were made for a total of 96 h. At 24 h, treated animals had lower pulmonary vascular resistance (207 +/- 85 versus 348 +/- 136 dyne X s X cm-5, p less than 0.01) but higher venous admixture (30 +/- 10% versus 18 +/- 12%, p less than 0.05) and thermodilution-measured lung water (17 +/- 8 ml/kg versus 9 +/- 2 ml/kg, p less than 0.05). However, by 96 h, there were no differences between the 2 groups in any measured parameters of hemodynamic status, gas exchange, or histologic examination. We conclude that pulmonary vasodilation increased blood flow to injured areas but did not affect eventual resolution of the injury.