Thermal desorption-gas chromatography of plasma isovaleraldehyde in hepatic encephalopathy in man.

The validation of a new assay for the leucine degradion product isovaleraldehyde in biological fluids is described. A gas purge technique was used with trapping of volatile constituents in a Tenax cartridge followed by automated thermal desorption and gas chromatographic analysis. The concentration of isovaleraldehyde during the course of hepatic encephalopathy (80 observations in 48 patients; 25 cirrhotic, 23 fulminant hepatic failure) was significantly increased compared to control subjects (0.58 +/- 0.08 compared to 0.17 +/- 0.02 mol/l; p less than 0.001). However, concentrations in grades 3-4 coma (37 observations) and grades 1-2 coma (30 observations) were similar and were not significantly different from values when encephalopathy was absent (grade 0; 13 observations). These results do not support an important role for isovaleraldehyde in the pathogenesis of hepatic encephalopathy.