Low dose almitrine bismesylate improves pulmonary gas exchange during canine one-lung hypoxia

The effects of low dose almitrine bismesylate on pulmonary gas exchange, venous admixture, and pulmonary perfusion were examined in a canine one-lung hypoxic model. The left lung was ventilated with 10.4% oxygen, 89.3% nitrogen, and 0.3% halothane, while the right lung was ventilated with 99.7% oxygen and 0.3% halothane. Group 1 (n = 8) was given no other drug for 60 min. In group 2 (n = 10), consecutive almitrine doses of 0.5, 1, and 2 micrograms/kg.min were administered iv for 20 min/dose. Blood gas and central hemodynamic values remained unchanged in group 1. In group 2, significant increases in PaO2 and significant decreases in venous admixture, dependent on the dose administered, were observed. Mean PaO2 increased from 222 +/- 78 (SD) to 292 +/- 75 torr, and mean venous admixture decreased from 22 +/- 7% to 18 +/- 6% at 2 micrograms/kg.min. Both the decrease in mean left pulmonary blood flow and the increase in mean right pulmonary blood flow were slight, although the cardiac output was unchanged. These results indicate that iv infusion of 2 micrograms/kg.min of almitrine weakly enhances pulmonary vasoconstriction in a hypoxic area and improves pulmonary gas exchange in a moderately hypoxic condition.