Blood ammonia levels were measured in 40 of 43 cases of Reye's syndrome; the blood ammonia level was elevated in 32 cases. The level of blood ammonia was directly related to the level of consciousness and survival. There was no correlation between subsequent changes in the blood ammonia level and the clinical course. We conclude that ammonia intoxication contributes to the encephalopathy of Reye's syndrome, and, probably, that other factors secondary to hepatic dysfunction are also important. In the presence of encephalopathy, biochemical criteria indicating hepatic dysfunction appear to provide a rational, nonhistologic basis for the diagnosis of Reye's syndrome.
Allen M. Glasgow, Robert B. Cotton, Kamnual Dhiensiri. Reye's SyndromeI. Blood Ammonia and Consideration of the Nonhistologic Diagnosis. Am J Dis Child. 1972;124(6):827–833. doi:10.1001/archpedi.1972.02110180029003