Effect of respiratory acidosis on plasma and CSF free amino acids.

Acid-base data and levels of selected cerebrospinal fluid (CSF) free amino acids were analyzed in a series of 8 patients in acute respiratory failure. In these patients, there were increased CSF concentrations of methionine, phenylalanine, tyrosine, histidine, alpha-amino-N-butyric acid, glutamic acid, glutamine, glycine, alanine, and ammonia, while arginine decreased. Phenylalanine, tryosine, and alanine were correlated with CSF PCO2; and alpha-amino-N-butyric acid to the buffer capacity of CO2 and pH. The data suggest the hypothesis that there are two metabolic phases for ammonia removal from brain tissue, that could explain some of these pathhophysiological conditions.