Direct measurement of blood pressures in minute vessels of the liver

Abstract

A method has been described which allows the insertion of microneedles into minute blood vessels of the transilluminated rat liver. Using dye injections under controlled pressures and direct observation, blood pressures in the terminal portal venules as well as in the central veins of this preparation have been determined and have been compared with simultaneous pressure measurements in the mesenteric veins and in the vena cava at the level of entry of the hepatic veins. The results indicate an unexpectedly large pressure drop in the portal venous tree (from 13 cm H₂O in the portal vein to approximately 6 cm in the portal venules), a significant pressure drop between portal venules and central veins (from 6 to 2.5 cm H₂O), and a paradoxical mean pressure relation between central vein and vena cava. Discussion of these results has been presented in terms of methodological problems, the implication of the results for the control of blood flow distribution in the liver, and the intermittency of hepatic vein flow in the rat.