Prostacyclin effect on blood pressure in pig with aortic obstruction

Cardiovascular effects of infused prostacyclin (PGI2) were investigated in hypertensive anesthetized pigs in the steady state and at 1,2,3,4,5,10,15,20 and 30 min after the beginning of the infusion. PGI2 were perfused at the rate of 2 microgram/Kg/min for 4 min before and after vagosympathectomy. We measured the mean arterial pressure, heart rate, cardiac output, stroke volume, mean pulmonary arterial pressure, mean pulmonary wedge pressure and calculated total systemic resistance and total pulmonary resistance. Our findings suggest that prostacyclin lowers pulmonary and systemic blood pressure in hypertensive animal by vasodilatation. The decrease in mean arterial pressure does not produce any change in heart rate probably because the substance also has a vagal effect. Finally, it might reduce venous return by dilatation of capacitance vessels. PGI2 appears to be a powerful vasodilator agent acting both afterload and preload without influencing heart rate or stroke volume.