Effects of hypoxia on the hemodynamic actions of prostaglandin E₁

The effect of prostaglandin E₁ (PGE₁) on central and peripheral hemodynamics was studied in seven conscious dogs under conditions of normoxia and hypobaric hypoxia to ascertain if hypoxia attenuated the cardiovascular actions of PGE₁. Silastic catheters were chronically implanted in the pulmonary artery, left atrium, and aorta. Acute hypoxia was produced in a hypobaric chamber maintained at 446 mmHg pressure (14,000 feet). PGE₁ at sea level (normoxia) resulted in significant increases in heart rate, cardiac output, left ventricular stroke work and pulmonary blood volume as well as significant decreases in aortic, pulmonary arterial, and left atrial pressures. During hypobaric hypoxia, PGE₁ produced essentially identical effects on all hemodynamic parameters except pulmonary blood volume and pulmonary arterial pressure where marked attenuation of PGE₁ action occurred. Significant hypoxemia does not alter the peripheral and myocardial actions of PGE₁ in intact animals. Attenuation of the pulmonary hemodynamic actions of PGE₁ may be secondary to the effect of hypoxia on certain segments of the pulmonary vascular bed.