Source Department of Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, China; Email: firstname.lastname@example.org.
BACKGROUND AND AIMS: Although the exact pathogenetic factor in hepatic encephalopathy is still unknown, ammonia is considered to be the major cause of neurotoxicity. However, previous studies on the relationship between ammonia and the severity of hepatic encephalopathy have yielded variable results. Since unionized ammonia is the only form of ammonia that is able to freely spread through the blood-brain barrier and cause cerebral dysfunction, we tested the hypothesis that concentration of unionized ammonia is correlated with the severity of hepatic encephalopathy.
METHODS: 156 patients with cirrhosis (74 with hepatic encephalopathy and 82 without) were enrolled, and underwent clinical examination and blood testing. Ammonia, pNH3 and pH determinations were repeated after two days of treatment. The differences in venous ammonia, pNH3, and pH among patients with and without encephalopathy were analyzed.
RESULTS: Among cirrhotic patients with hepatic encephalopathy, pH, pNH3 and ammonia levels were all higher than those among patients without hepatic encephalopathy, and alkalosis was more common in patients with hepatic encephalopathy. Both venous ammonia and pNH3 were significantly correlated to the clinical grade of hepatic encephalopathy; however, the r was similar for venous ammonia (r=0.63) and pNH3 (r=0.68). The follow-up of 20 patients showed that the median levels of pH, pNH3 and venous ammonia decreased; venous ammonia levels were unchanged or higher in some patients after resolution of hepatic encephalopathy.
CONCLUSION: This study supports that pH-dependant pNH3 and pH could be useful diagnostic and prognostic tools in cirrhotic patients with hepatic encephalopathy.