The effect of mechanically enhancing portal venous inflow on hepatic oxygenation, microcirculation, and function in a rabbit model with extensive hepatic fibrosis

Enhancing the portal venous blood flow (PVBF) has been shown to reduce port al pressure and intrahepatic vascular resistance and to improve liver funct ion in isolated cirrhotic rodent livers in vitro, The aim of this study was to assess the short-term effect of mechanically pumping the portal inflow on hepatic microcirculation (HM), oxygenation, and function in an animal mo del of extensive hepatic fibrosis. New Zealand white rabbits underwent lapa rotomy and exposure of the liver: group 1 (n = 7) were normal controls; gro up 2 (n = 7) had hepatic fibrosis. Total hepatic blood flow (THBF) and HM w as measured along with continuous monitoring of intrahepatic tissue oxygena tion using near infrared spectroscopy (NIRS). Baseline hepatic hemodynamics and liver function were measured in both groups. PVBF was then increased b y 50% over a 3-hour period in the hepatic fibrosis group using a miniature portal pump designed for human implantation, and the hemodynamics were moni tored continuously, Liver function tests were repeated after portal pumping . In comparison with normal controls, animals with hepatic fibrosis had a h igher portal pressure (13.0 +/- 3.6 vs. 3.7 +/- 1.4 mm Hg, P <.001, mean +/ - SD vs. controls), reduced PVBF (52.4 +/- 24.6 vs. 96.9 +/- 21.1 mL/min, P =.003), and increased portal vascular resistance (P =.001), THBF and flow in the HM was lower than in controls, and liver function tests were abnorma l. After a 3-hour period of enhanced portal flow in animals with hepatic fi brosis, the portal pressure greatly reduced (13.0 +/- 3.6 to 2.5 +/- 1.1 mm Hg, P <.001) as did the intrahepatic portal resistance (0.32 +/- 0.18 to 0 .04 +/- 0.03 mm Hg/mL/min, P =.006). Flow in the HM improved (143 +/- 16 to 173 +/- 14 flux units, P =.006) and was associated with improved hepatic t issue oxygenation, tissue oxy-hemoglobin (HbO(2)) and cytochrome oxidase be ing increased by 24.4 +/- 7.5 and 5.65 +/- 2.30 mu mol/L above the baseline value (P <.001), respectively. A 3-hour period of mechanical portal pumpin g produced a dramatic improvement in liver function, bilirubin (41.1 +/- 25 .9 to 10.0 +/- 5.9 mu mol/L, P =.040), aspartate transaminase (AST) (135.5 +/- 52.3 to 56.3 +/- 19.8 U/L, P =.006) and lactate dehydrogenase (LDH) (2, 030.1 +/- 796.3 to 1,309.8 +/- 431.6 IU/L, P =.006; prepumping vs. postpump ing, all P <.050). In conclusion, portal pumping in this rabbit model with extensive hepatic fibrosis improved liver parenchymal perfusion, oxygenatio n, and function.