[Cerebral manifestations in the hepatic coma syndrome (author's transl)]

The pathogenesis of hepatic encephalopathy has been investigated in a two-stage devascularization model in the rat with portavacal shunt and hepatic artery ligation. There is a significant increase in brain octopamine and phenylethanolamine and a decrease in brain norepinephrine (NE) 6 to 9 hours after hepatic artery ligation. The depletion of NE seems the sequel of diminished synthesis in the presence of an unaltered turnover rate, due to a blockade of tyrosine hydroxylase either by accumulation of false neurochemical transmitters or by phenylalanine. It is most marked in the cortex and midbrain. The high-energy phosphate compounds, ATP, phosphocreatine and glucose-6-phosphate are not diminished in hepatic coma, nor is glucose, indicating that other mechanism are involved in the pathogenesis of metabolic state by the increased ammonia level. "intestinal sterilization" and total colectomy have no significant effect on the ammonia level, but cause a decrease in the level or aromatic precursor amino acids in the plasma and brain, with normalization of the level of cerebral transmitters. These results permit the formulation of a unified concept of the hepatic coma syndrome and its clinical manifestations such as flapping tremor, the hyperdynamic cardiovascular state and the hepatorenal syndrome. Moreover, they form the basis for the introduction of a new therapeutic principle in the management of hepatic encephalopathy by L-dopa or modified amino acid solutions, which act by altering the central and peripheral neurotransmitters.