POSTOPERATIVE COURSE AFTER PORTACAVAL ANASTOMOSIS IN RATS IS DETERMINED BY THE PORTACAVAL PRESSURE-GRADIENT

Variability in experimental results have led to criticism regarding the validity of the rat after portacaval anastomosis (PCA) as a model of changes induced by portal-systemic shunting (PSS). A nonsuture technique using cyanoacrylate glue has been reported to yield a better experimental preparation. To investigat if variations in splanchnic hemodynamics could explain different outcomes after the procedure, male rats received either an end-to-side PCA or sham operations (16 rats each). The PCA was constructed using the "suture" or "glue" technique (8 rats each). Beginning on postoperative day 24 under methoxyflurane and ketamine anesthesia, pressures were recorded from the portal vein, inferior vena cava, and femoral artery. Blood flow to the splanchnic organs and the percent PSS were assessed using the microsphere technique. The rate of delivery of NH3 from the portal vein to the systemic circulation and the concentration of glutamine in the cerebrospinal fluid were determined. In PCA rats, weight gain was significantly impaired, and all animals had evidence of liver atrophy (in both suture and glue groups) when compared with sham animals; a trend toward greater weight gain was seen in glue rats. Portal vein inflow, PSS, NH3 delivery, and CSF glutamine were significantly increased in both PCA-suture and PCA-glue animals compared with sham rats, although no significant differences were seen between the two PCA techniques. When PCA rats from either technique were grouped according to the pressure gradient between portal vein and inferior vena cava, striking differences between animals were now evident. Rats with an "open" anastomosis (gradient less-than-or-equal-to 2.0 mmHg) showed a significantly smaller weight gain, a greater degree of liver atrophy, a larger portal venous inflow, and a larger NH3 delivery to the systemic circulation, resulting in higher CSF glutamine levels. We conclude that the variability of results after PCA by either the suture or glue technique can be explained by the development of shunt stenosis. Measurement of the portacaval pressure gradient may help to standardize this model.