Hepatic assist devices

Acute liver failure (ALF) is associated with significant morbidity and mortality. Better understanding of the pathophysiology of the disease and improvements in patient management have resulted in increased survival. Liver transplantation remains the only proven therapeutic modality. Primarily because of organ donor shortage, a number of strategies have been developed in an attempt to support patients with severe ALF until either an organ becomes available for transplantation or until they recover. Liver support strategies include use of either non-biological or biological systems. Non-biological systems include plasma exchange, hemodialysis, hemofiltration, charcoal and resin hemoperfusion. These systems are able to remove toxins, but their utility is limited by their inability to provide missing liver synthetic function. Biological liver support systems include ex vivo liver perfusion and use of hepatocyte-based extracorporeal devices. Like non-biological systems, biological ones provide a means of detoxification and in addition biotransformation and biosynthetic functions. The major limitation of these systems is the lack of availability of an effective highly differentiated human hepatocyte line for clinical use. Currently clinically tested liver support systems use either porcine hepatocytes or human hepatoma cell lines. As liver support therapy evolves, there will be a role for both biological and non-biological liver support systems to treat specific forms of liver failure.