A 55-year-old man on ICU develops acute liver failure. His arterial ammonia is 180 µmol/L (normal <50). He has grade 3 hepatic encephalopathy. What is the primary mechanism by which hyperammonaemia causes cerebral oedema in acute liver failure?AAmmonia has no role in cerebral oedemaBAmmonia crosses the blood-brain barrier and is metabolised by astrocytes to glutamine via glutamine synthetase - glutamine acts as an osmole, drawing water into astrocytes causing cytotoxic (cellular) oedemaCAmmonia directly damages the blood-brain barrier causing vasogenic oedemaDAmmonia inhibits cerebral blood flowEAmmonia causes cortical necrosisCheck my answer