Dissimilar effects of prostacyclin on cardiac output and forearm blood flow in healthy men

Abstract

Summary. Cardiac output, heart‐rate, stroke volume, pressures in the brachial artery, right ventricle and pulmonary artery, forearm blood flow and in addition arterial concentrations of lactate, glucose and free fatty acids were measured in eight healthy male volunteers during i.v. infusion of prostacyclin in doses corresponding to 2 ng, 6 ng and 12 ng min ‐1 kg ‐1 b.w. The highest dose almost doubled cardiac output and this was achieved by similar increases in stroke volume and heart‐rate. Arterial diastolic and mean pressures decreased slightly while systolic pressure was unaffected. The calculated total systemic vascular resistance decreased to half the initial level. However, forearm blood flow increased insignificantly and forearm vascular resistance was not significantly altered. Pulmonary artery pressure rose only minimally, which in the presence of a great increase in cardiac output indicates pulmonary vasodilatation. Arterial lactate and glucose concentrations were not significantly altered while free fatty acid concentration increased slowly during the infusion period to a similar degree as previously shown in fasting individuals undergoing catheterisation. It is concluded that prostacyclin decreases both pulmonary and total systemic vascular resistance but unlike the most potent vasodilator of the ‘classical’ prostaglandins, PGE 17 it has dissimilar vasoactive potency in different systemic vascular beds as evidenced by the insignificant decrease in forearm, simultaneous with the pronounced decrease in total systemic vascular resistance.