The effect of increased inferior vena cava pressure on hepatic circulation in the dog.

Inferior v. cava pressure (IVCP) was raised in the dog by a baloon catheter introduced via the jugular vein. Hepatic artery flow (HAF) and portal venous flow (PVF) were measured with the electromagnetic flow meter. The increase of IVCP reduced uniformly HAF and PVF, the relative contribution of the two vessels to the HBF did not change. The relationship between IVCP increase and HAF reduction and between the decrease of AP-IVCP and the reduction of HAF was linear. There was no sign of autoregulation or vasomotor regulation of HAF. The changes in IVCP are only partially transmitted to the portal venous pressure (PVP). There was no change in intrahepatic portal resistance with increased IVCP. The increase in PVP did not lead to resistance changes in the splanchnic circulation. As a sign of the autoregulation of splanchnic circulation of the AP-PVP versus PVF curve was concave to the pressure axis. It is concluded that as a result of opposing autoregulatory and vasomotor influences in the intact animal the hepatic circulation appears to react passively to the increased outflow pressure.