Venous, arterial, and arterialized-venous blood ammonia levels and their relationship to hepatic encephalopathy after propranolol.

To assess side effects of propranolol in the treatment of portal hypertension, we measured blood ammonia in 14 cirrhotics before and after administration of propranolol, and in six cirrhotics before and after placebo. We evaluated ammonia blood levels obtained from three sites: venous, arterial, and arterialized-venous, obtained by warming the forearm. Ammonia concentration of arterial and arterialized-venous blood were abnormal for all cirrhotics studied and significantly greater than the ammonia concentration of venous blood (p less than 0.01). When propranolol was administered to patients with alcoholic cirrhosis and marginal liver function, as reflected by ammonia levels above 60 microM, it caused a significant increase in ammonia levels in arterialized-venous and arterial, but not in venous, blood (p less than 0.05). Propranolol caused a significant increase in the time required to perform sensitive psychometric tests (p less than 0.05). Encephalopathy usually became clinically apparent when the mean of the arterial and arterialized-venous blood ammonia levels rose above 122 microM.