The effects of intravenously administered almitrine (0.3 or 1.0 micrograms/kg/min, for 30 min) on hemodynamics and pulmonary gas exchange were assessed in eight dogs with acute lung injury induced by paraquat under controlled ventilation. Arterial blood gases, pulmonary and systemic hemodynamics, and ventilation-perfusion distribution (VA/Q) using the multiple inert gas elimination technique were examined before (control) and during infusion of almitrine. Almitrine produced significant increases in mean pulmonary arterial pressure from 17.4 +/- 3.3 (control, mean +/- SD) to 20.4 +/- 1.5 mmHg (1.0 micrograms/kg/min), and in total pulmonary vascular resistance. There was no change in other hemodynamic parameters, arterial gas tensions, or VA/Q distribution. These results indicate that almitrine causes pulmonary vasoconstriction without changing ventilation-perfusion distribution in dogs with paraquat-induced lung injury.