Hemodynamic effects of prostaglandins and catecholamines in graded reduction of pulmonary flow during venoarterial bypass in awake goats

The roles of prostaglandins and catecholamines in the hypotensive hemodynamic change during cardiopulmonary support with a venoarterial bypass (VAB) were investigated in a series of chronic animal experiments of gradually reduced pulmonary arterial blood flow (PAF). The VAB system consisted of a pulsatile ventricular assist device, an artificial lung, and the right atrium uptake and descending aorta return cannulae in four adult goats weighing 49-51 kg. The PAF was adjusted to 50, 10, and 0% of the total systemic blood flow. Indomethacin, an inhibitor of prostaglandin production; phentolamine, an α-antagonist of catecholamine; and noradrenaline, an agonist of catecholamine were administered at each PAF condition. The mean aortic pressure (mAoP) and the systemic vascular resistance decreased in proportion to the decrease in PAF. Indomethacin increased the mAoP at all PAF conditions, indicating a relationship between prostaglandins and hypotension. Phentolamine decreased the mAoP at all PAF conditions, indicating a normal response of catecholamine receptors. However, noradrenaline increased the mAoP at 50 and 10% PAF, but did not appreciably increase the value at 0% PAF, indicating complete response of catecholamine receptors to endogenous catecholamines at 0% PAF only. In conclusion, prostaglandins play a substantial role in hypotension during VAB, and catecholamines may subsequently increase in compensation for extreme hypotension.