Contribution of the arterial blood ketone body ratio to elevate plasma amino acids in hepatic encephalopathy of surgical patients.

To clarify the role of hepatic metabolic derangements in elevated plasma amino acid levels, the patterns of plasma amino acids in 17 surgical patients with hepatic failure were analyzed in relation to the blood ketone body ratio (acetoacetate to beta-hydroxybutyrate), which reflects the mitochondrial redox potential. The blood ketone body ratios were 0.49 in eight alert patients with hepatic failure and 0.28 in nine patients with grade IV hepatic coma, compared with values of 0.79 to 6.42 in patients with healthy livers. The plasma concentrations of alanine, proline, phenylalanine, and tyrosine were negatively correlated with the blood ketone body ratio. Elevations of alanine, phenylalanine, tyrosine, and glutamate were greater in comatose patients than in alert patients. Also, the molar ratios between the plasma concentrations of the branched-chain amino acid and the aromatic amino acids were positively correlated with the blood ketone body ratio (r = 0.78, p less than 0.0001). We suggest that a reduced mitochondrial redox potential, coupled with enhanced muscle breakdown, results in inhibition in the entrance of the amino acids into the Krebs' cycle and then the characteristic changes in the free amino acid patterns which result in hepatic coma.