Effects of porta-systemic shunting and ammonia infusion on cerebral blood flow autoregulation in the rat

Abstract   Background: Portacaval shunting of blood, hyperammonemia, and impaired cerebral blood flow (CBF) autoregulation are assumed to be involved in the development of high intracranial pressure (ICP) in liver failure. In this study, we determined whether CBF autoregulation is impaired by portacaval anastomosis and hyperammonemia. Methods: Four groups of pentobarbital-sedated and mechanically ventilated rats were investigated after construction of a portacaval anastomosis or following sham operation. Half of the rats received either infusion of ammonia (55 μmol/kg/minute) or saline for 180 minutes. Arterial pressure and ICP was monitored, and lower limit of CBF autoregulation was determined.