Hemodynamic analysis of the portal circulation during temporary portal vein occlusion and after portal-systemic shunt surgery
Archie, J.P.
Surgery 82(5): 674-679
1977
ISSN/ISBN: 0039-6060 PMID: 918854 Document Number: 116932
Simple principles of fluid mechanics are used to determine the physical meaning of free and clamped portal vein pressures in patients with portal hypertension undergoing portal-systemic shunt operations. Two frequently used indices of hemodynamic staging in these patients are the maximum perfusion pressure or the difference between the splanchnic occluded portal pressure (Ppvs) and the hepatic occluded portal pressure (Ppvh), and the difference between the free portal pressure (Ppv) and Ppvh. Analysis of fluid mechanics show that neither of these indices directly or accurately predicts hepatic blood flow. The fractional percentage of planchnic blood flow that goes to the portal vein depends on the ratio Ppv/Ppvs. Reverse portal vein flow occurs only when Ppv/Ppvs > 1. The fractional percentage of total hepatic flow arising from the hepatic artery is a fucntion of Ppvh/Ppv. The fractional percentage of decrease in hepatic blood flow when the portal vein is occluded is equal to Ppvh/Ppv. The ratio of hepatic blood flow after portal-systemic shunting to preshunt flow is equal to the ratio of post- to preshunt free portal pressures. All equations are nondimensional and normalized and hence are globally applicable, independent of size of the patient and absolute regional blood flows. They may form a basis for quantitative intraoperative assessment of hepatic perfusion, selection of type of shunt and hemodynamic staging.