Effects of vena caval banding in experimentally induced multiple portosystemic shunts in dogs.
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Effects of vena caval banding on portal venous and vena caval hemodynamics were examined in 6 control dogs and in 10 dogs that had undergone attenuation (banding) of the abdominal part of the caudal vena cava and had dimethylnitrosamine-induced multiple portosystemic shunts (PSS). Additionally, indocyanine green (ICG) extraction and clearance after infusion to steady state were used to calculate hepatic plasma flow in these dogs. Sixteen dogs were randomly assigned to 2 groups: control (n = 6) or diseased (n = 10). Diseased dogs were administered dimethylnitrosamine (2 mg/kg, PO, twice weekly) until multiple PSS developed, as assessed by results of clinical laboratory tests, ultrasonography, and hepatic scintigraphy. Shunts were confirmed visually at celiotomy and by contrast portography. Venous pressures (caudal vena caval, portal, and hepatic) were recorded before and after vena caval banding for up to 7 days in dogs from both groups. Peritoneal cavity pressures were recorded in all dogs after closure of the body wall. To determine ICG extraction and clearance, a bolus injection of ICG (0.5 mg/kg, i.v.) was administered, followed by steady-state infusion of 0.097 mg/min. Extractions and clearances of ICG were measured, and from these, hepatic plasma flow rates were determined immediately before and after banding and at 6 hours, 48 hours, and 7 days after banding. The gradient (caudal vena caval pressure within 1 to 2 mm of Hg of portal pressure) between caudal vena cava and portal venous pressures established at banding was maintained after the first hour in both groups. Caudal vena cava pressures established at banding were maintained throughout the study, with the exception of the first hour in diseased dogs. Extraction ratios were higher in control dogs at all times, except at 48 hours. Clearance was higher in control dogs at all times. Hepatic plasma flow did not differ between groups, except immediately after banding, when flow was greater in diseased dogs, and differences were not found over time in either group. This study indicated that vena caval banding in this model of experimentally induced multiple PSS increases and maintains caudal vena cava pressure, relative to portal venous pressure (after the first hour) for 7 days, and that calculated hepatic plasma flow is not persistently improved by vena caval banding.
