An experimental study of hepatic blood flow and oxygen metabolism with the portal vein transiently blocked

Though numerous studies of systemic hemodynamics concerned with transient blockade of the portal vein exist, few studies have been performed specifically to assess blood flow and oxygen metabolism in the liver under such conditions. We blocked the portal vein in adult mongrel dogs and measured systemic hemodynamics, hepatic blood flow, total oxygen delivery to the liver, and the oxygen consumption and extraction ratio in order to evaluate the effect of a blockade of the portal vein on hepatic oxygen metabolism. In addition, a portal vein bypass was established and its effect on the liver was evaluated in comparison to a simple blockade of the portal vein. The results suggested that arterial blood pressure and cardiac output declined severely upon simple blockade of the portal vein, and a decrease in total hepatic blood flow which could be avoided by establishing a portal vein bypass was also observed. Simple blockade of the portal vein maximally accelerated the oxygen extraction ratio, though oxygen consumption by the liver significantly decreased due to insufficient oxygen supply caused by the decrease in blood flow in the hepatic artery. With a portal vein bypass, however, blood flow in the hepatic artery did not fall, oxygen consumption was maintained at a constant level, and a moderate rise in the oxygen extraction ratio was observed. These results indicate that establishing a portal vein bypass may be useful to protect the liver.