Use of bioartificial and artificial liver support devices.

With all the new work and current interest in extracorporeal liver support systems incorporating hepatocytes, the findings with earlier artificial systems need to be reconsidered, particularly as they may constitute a component of some bioartificial devices. Furthermore, new and more effective artificial systems are currently under development. Essential hepatic functions need to be replaced, including excretory (the capability of adsorbents and dialysis) and synthetic and biotransformatory function, but the relative importance of these three functions in terms of promoting recovery of the native liver is as yet unclear. Two bioartificial devices have already been used clinically in the treatment of acute liver failure (ALF): the bioartificial liver (BAL) based on pig hepatocytes attached to microcarriers, and the extracorporeal liver assist device (ELAD) which contains a human liver-derived tumor cell line. As with earlier completely artificial systems, the results so far obtained in man are less impressive than in animal models of ALF. An important question not yet answered relates to quantity of cells and specific function in the new hybrid bioreactor devices required for clinical benefit, as well as the duration of support needed. A better understanding of the effects of these devices on the metabolic function of the damaged liver and the recovery process will be essential in the further development and design of effective systems. Controlled clinical trials on a multicenter basis will be needed for proper evaluation of these new approaches to treatment of ALF. From our own initial experience, the design of these protocols and the selection of biochemical tests will be difficult.