Abstract
Hemodynamic and humoral conditions under various pulmonary blood flow during venoarterial bypass (VAB) were quantitatively investigated in a series of chronic animal experiments. A biventricular bypass system was installed in 6 adult goats weighing 50.0±1.1 kg. Two weeks later the extracorporeal circuitry was changed to VAB without anesthesia. The PAF was reduced stepwise from 100% to 50, 25, 10 and 0% of total systemic flow. The mean aortic pressure (mAoP) and systemic vascular resistance (SVR) decreased in proportion to the decrease in PAF and caused a sort of shock state at 0% PAF. The prostaglandin E2 (PGE2) concentration increased following the decrease in PAF from 100 to 0%. The renin-angiotensin system increased in proportion to the decrease in PAF. In contrast, the catecholamines concentrations did not change appreciably even at 10% PAF, but were markedly elevated at 0% PAF. The antidiuretic hormone level similarly changed. In conclusion, decrease in PAF during VAB exerts significant effects on the hemodynamics. The changes in the levels of vasodilators, especially PGE2, may play a substantial role in the decrease in SVR, whereas changes in vasoconstrictors are likely to be a secondary reaction to the decrease in mAoP.
