The definitive treatment of patients with acute liver failure is liver transplantation. Organ Procurement and Transplantation Network status 1 patients receive priority, but the median waiting time in 2002 was 11 days. Patients who are small or have an unusual blood type are expected to wait even longer. Because cerebral edema and death may occur before a liver is available, numerous methods of bridging patients to transplantation by artificial means have been proposed. To date, no system of hepatic support has been proven effective at delaying the onset of cerebral edema in controlled trials.