Hepatic arterial and portal venous flows during hemorrhage

Changes of total liver blood flow (TLBF), portal venous and hepatic arterial flows have been investigated using a hemorrhagic model in dogs. The dogs were bled stepwise from normal blood pressure to a pressure of 50-60 mm Hg. TLBF was measured by the xenon clearance method. Hepatic arterial blood flow was measured by electromagnetic flowmeter. Portal venous flow was calculated by subtracting hepatic arterial blood flow from TLBF. Other parameters studied during the experiment were systemic arterial blood pressure and portal venous pressure. Under normotensive conditions TLBF in mean was registered as 127 ml/min X 100 g liver tissue (25 ml/min X kg body weight). The relation between the flow value in portal vein and hepatic artery was on average 2.3:1. The study shows that there was a pronounced decrease of TLBF flow during hemorrhage. Portal venous flow decreased almost parallel to TLBF, while hepatic arterial flow decreased to a lesser extent which means that there was autoregulation in this flow bed. Hepatic arterial flow successively constituted a larger part of TLBF, during hemorrhage sometimes 65% compared to the normal value of about 30%. During the study there was an increase of vascular resistance in the portal venous system and decreased resistance in the hepatic arterial bed.