Acute hemodynamic effects of prostacyclin infusion in severe or malignant hypertension.

Abstract

The hemodynamic effects of prostacyclin (PGI2) were studied in seven patients with severe or malignant hypertension. Blood pressure, cardiac output (Cardio-Green dilution method) and total blood volume (131I- Albumin dilution method) were measured before and during a PGI2 infusion, the effective dose ranging from 10 to 20 ng/kg/min. Cardiac index (CI) rose from 2.8 to 3.9 l/min/m2 and heart rate (HR) from 75 to 94 beats/min (P < 0.01). Mean blood pressure decreased from 154 to 120 mm Hg (P < 0.001) and total peripheral resistance from 4650 to 2540 dynes s cm−5 (P < 0.001). The ratio: central blood volume/total blood volume increased from 0.21 to 0.26 (P < 0.001). The decrease in blood pressure was related to the dose of prostacyclin (P < 0.001), but the vasodilatation was dose-dependent only from 5 to 12–5 ng/kg/min; for a higher dose, the decrease in blood pressure was related to the decrease in cardiac output as the heart rate was reduced. The results confirmed that PGI2 produces a potent vasodilatation of the arterial system; the decrease in blood pressure was limited by an increase in cardiac index mainly related to the tachycardia induced by prostacyclin; significant central translocation of blood suggested that PGI2 did not produce dilatation of the capacitance vessels. At low doses, the sympathetic nervous system was greatly stimulated by PGI2; at a higher dose, the vagal stimulation was predominant, inducing bradycardia and a fall in blood pressure.