An effective hepatic assist system could serve as a bridge to transpla
ntation or to treat acute or chronic hepatic failure. Early nonbiologi
cal approaches focused on the removal of low molecular weight toxins b
y dialysis or hemoperfusion, such as over charcoals or resins. This ap
proach led to clinical trials that showed varying degrees of success.
Introduction of more porous membranes and blood separation technologie
s stimulated the development of plasma exchange, on-line plasma fracti
onation technologies with sorbents and membranes, and other schemes of
sorbent-blood interactions based on the principles of dialysis and he
mofiltration 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 chr
onic liver disease, blood detoxification can be applied in patients in
tractable to conventional therapies and for some awaiting transplantat
ion to relieve disease symptoms such as pruritus, jaundice, elevated b
ile acids, hyperbilirubinemia, endotoxemia, and hypercholesterolemia.
Although biological support is considered the ideal, nonbiological tec
hniques can be useful because hepatocytes possess a regenerative capac
ity and temporary support is helpful. Available nonbiological liver su
pport technologies can substitute for select liver functions in acute
and chronic disease.