We sought to determine whether false neurotransmitters (FNTs) play an important role as determinants not only of hepatic encephalopathy but also of hyperdynamic syndrome in cirrhosis. A combined biochemical and hemodynamics study of 55 bleeding cirrhotic patients was made. We evaluated the aromatic and aliphatic branched-chain amino acids and octopamine serum levels as well as the hemodynamic measurements. The results show that there is a correlation between levels of serum octopamine and aromatic amino acids and hepatic coma: the higher the octopamine level, the deeper the hepatic coma. There is also a correlation between aromatic amino acids and cardiac index and total peripheral resistance. Furthermore, when a narrowing of arteriovenous difference in oxygen occurs and oxygen consumption decreases, there is an increase not only in the level of aromatic amino acids, but also in octopamine level, suggesting an important linkage between hemodynamic and metabolic impairment.