Nonbiological liver support: historic overview.

An effective hepatic assist system could serve as a bridge to transplantation or to treat acute or chronic hepatic failure. Early nonbiological approaches focused on the removal of low molecular weight toxins by dialysis or hemoperfusion, such as over charcoals or resins. This approach led to clinical trials that showed varying degrees of success. Introduction of more porous membranes and blood separation technologies stimulated the development of plasma exchange, on-line plasma fractionation technologies with sorbents and membranes, and other schemes of sorbent-blood interactions based on the principles of dialysis and hemofiltration with sorbent perfusion. Although detoxification of blood has improved the prognosis for acute liver failure, key issues of when to initiate treatment and by which method need to be resolved. In chronic liver disease, blood detoxification can be applied in patients intractable to conventional therapies and for some awaiting transplantation to relieve disease symptoms such as pruritus, jaundice, elevated bile acids, hyperbilirubinemia, endotoxemia, and hypercholesterolemia. Although biological support is considered the ideal, nonbiological techniques can be useful because hepatocytes possess a regenerative capacity and temporary support is helpful. Available nonbiological liver support technologies can substitute for select liver functions in acute and chronic disease.