Transsinusoidal fluid dynamics in canine liver during venous hypertension.

Abstract

Arterial pressure, portal pressure, inferior vena caval pressure, hepatic interstitial pressure (implanted capsule technique), prenodal lymph flow and the protein concentration in plasma and lymph were studied in the anesthetized dog under normal conditions and during graded venous hypertension resulting from inferior vena caval occlusion. Under control conditions, portal, interstitial and inferior vena caval pressures were 7.0, 5.8 and 2.0 mm Hg, respectively, and the lymph-plasma protein concentration ratio was 0.95. During acute venous hypertension, 64% of the inferior vena caval pressure increase was transmitted to the hepatic interstitium, and lymph flow increased 63% for every 1 mm Hg increment in interstitial pressure. The lymph-plasma protein concentration ratio did not change significantly during venous hypertension, indicating that the reflection coefficient of the sinusoidal wall for the major plasma proteins is close to 0 and protein transport across the microvascular wall is due mainly to bulk flow. Using portal, interstitial and inferior vena caval pressures as limits for possible values of sinusoidal pressure, control sinusoidal pressure was between 5.8 and 7.0 mm Hg and .apprx. 90% of the increase in inferior vena caval pressure was transmitted to the sinusoids. Changes in interstitial pressure, lymph flow and surface transudation rate are major compensatory mechanisms of the liver to limit interstitial engorgement during venous hypertension.