[Association of plasma ammonia and GABA levels and the degree of hepatic encephalopathy].

Several toxic factors have been implicated in the pathogenesis of hepatic encephalopathy (PSE) among which ammonia plays a dominant role. More recently, the gamma-aminobutyric acid (GABA) hypothesis in which an increase in the GABA-ergic tone and the presence of one or more GABA/benzodiazepine receptor ligands which interact with that receptor, has been proposed. We investigated the levels of GABA and ammonia in plasma of patients with acute PSE to test the hypothesis that elevated plasma GABA levels would be found in acute encephalopathy and that GABA levels would correlate with the degree of hepatic encephalopathy. We measured plasma levels of GABA and ammonia during an acute episode of PSE, spontaneous or precipitated by gastrointestinal bleeding or sepsis, and performed assessments of PSE by the PSE index. Patients were evaluated before and two days after standard treatment with lactulose. We also measured plasma GABA levels in the hepatic vein of a selected group of patients undergoing hemodynamic studies. Plasma GABA levels were significantly higher in patients with acute PSE (458 +/- 108 pmol/mL) when compared with normal subjects (110 +/- 23 pmol/mL) (p < 0.01) although no correlation was found between plasma GABA concentration and the degree of PSE. Changes in plasma ammonia, however, correlated with improvements in the PSE index (r = 0.56; p < 0.02) and with abnormalities in the EEG (r = 0.65; p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)