HEMODYNAMIC AND HUMORAL CONDITIONS IN STEPWISE REDUCTION OF PULMONARYBLOOD-FLOW DURING VENOARTERIAL BYPASS IN AWAKE GOATS

The effects of reduced pulmonary arterial blood flow (PAF) during veno arterial bypass (VAB) on hemodynamic and humoral conditions were inves tigated in a series of experiments in a chronic animal model. A bivent ricular bypass system was installed in five adult goats weighing 49.8 +/- 1.1 kg. Two weeks later, the extracorporeal circuitry was changed to VAB without anesthesia. The PAF was reduced stepwise from 100% to 5 0, 25, 10, and 0% of total systemic flow. The mean aortic pressure and systemic vascular resistance decreased from 110 +/- 14 to 66 +/- 3 mm Hg and from 1,288 +/- 77 to 740 +/- 73 dyne.sec/cm(5), respectively, i n proportion to the decrease in PAF from 100 to 0%. The prostaglandin E-2 concentration increased from 1.5 +/- 0.6 to 8.8 +/- 0.6 pg/ml foll owing the decrease in PAF from 100 to 0%. The renin-angiotensin system increased in proportion to the decrease in PAF. In contrast, the epin ephrine and norepinephrine concentrations (60 +/- 10 and 227 +/- 80 pg /ml, respectively, at 100% PAF) did not change appreciably even at 10% PAF, but were markedly elevated to 335 +/- 117 and 2,088 +/- 1,503 pg /ml at 0% PAF. The antidiuretic hormone level similarly changed. In co nclusion, decrease in PAF during VAB exerts significant effects on hem odynamics in a proportional manner and on vasoactive humoral factors i n a diverse manner.