Brain edema in acute liver failure.

Brain edema and consequent increase in intracranial pressure is a major complication of acute liver failure (ALF) and is a major cause of death in this condition. Rapid accumulation of ammonia in brain has been implicated in the pathogenesis of brain edema in ALF. Increased brain ammonia may cause brain swelling via the osmotic effects of an increase in astrocytic glutamine concentration or by inhibition of glutamate removal from brain extracellular space. Acute liver failure results in altered expression of several genes in the brain, some of which code for proteins involved in central nervous system function such as the glutamate transporter GLT-1, the astrocytic structural protein, glial fibrillary acidic protein, and the water channel protein, aquaporin IV. Loss of expression of GLT-1 results in increased extracellular brain glutamate. Therapeutic measures currently used to prevent and treat brain edema in acute liver failure include mannitol; strategies aimed at lowering of gut ammonia production are generally ineffective. Studies in experimental animals suggest that mild hypothermia or the use of L-ornithine-L-aspartate may be useful in the prevention of brain edema in these patients.