Analysis of hemodynamic and respiratory effects of PGI2 in the pig

Cardiovascular and pulmonary effects of prostacyclin (PGI2) were investigated in the anaesthetized pig before and after vagosympathectomy at 1',2',3',4',5',10',15' and 20' after the beginning of the infusion. The animals were perfused with PGI2,2ug/kg/min for 4 min. We measured the following parameters : mean arterial pressure, heart rate, cardiac output, stroke volume, mean pulmonary arterial pressure, mean wedge pressure, left stroke work, total systemic resistance, total pulmonary resistance, tidal volume, respiratory frequency, minute volume, lung resistance and compliance, end-tidal CO2, transpulmonary pressure. Our findings suggest that the hypotension observed is due to a reduction in total peripheral resistance by a direct effect of PGI2 on the vascular bed without inhibition of the sympathetic nervous system. Prostacyclin does not directly modify cardiac function and produces a decrease in preload by venous dilation. The changes in pattern of breathing are related to the hypotensive effect of PGI2.