ALF is defined as a condition in which hepatic injury occurs in a liver that is either normal or considered to have normal functional reserve, leading to severe hepatic dysfunction within 8 weeks of the initial onset of symptoms. This is characterized by a prothrombin time of 40% or less or an INR value of 1.5 or higher. ALF is classified into two categories: the “coma type,” which presents with hepatic encephalopathy of grade II or higher (Table 35.1), and the “non-coma type,” where the patient is either clear-headed or exhibits grade I hepatic encephalopathy. The coma type acute liver failure is subclassified as shown in Table 35.2.