PRESSURE-FLOW ANALYSIS OF PORTAL-VEIN AND HEPATIC-ARTERY INTERACTIONS IN PORCINE LIVER

Interactions between the hepatic arterial and portal venous circulations were investigated in nine intact and eight isolated perfused porcine livers. Pressure-flow (P-Q) relationships were obtained in either the portal vein or hepatic artery with constant baseline or low flow in the other bed and a stable hepatic venous pressure (P-hv) The slope was obtained by linear regression analysis of the P-Q relationship, and effective back pressure (P-back) was Obtained from the pressure intercept for the portal vein and the measured zero-flow pressure for the hepatic artery. The P-back in the hepatic artery (13.4 +/- 1.5 mmHg) and the portal vein (4.6 +/- 0.3 mmHg) were higher than P-hv (P < 0.05). Reducing portal vein flow (Q(pv)) produced an increase in hepatic artery flow (Q(ha)) (P < 0.05) due only to a decrease in slope (P < 0.05). Decreasing Q(ha) caused an identical change in P-back Of the portal vein (P < 0.05) in the intact and isolated liver preparations. A change in Q(pv) alters the hepatic arterial resistance upstream from the site of a constant arterial P-back Changes in total flow through the common sinusoidal compartment appear to alter the P-back Of the portal vein via hydraulic mechanisms.