Despite the progress of intensive care medicine, liver failure still has a poor prognosis. To bridge the period of acute decompensation, extracorporeal liver support devices have been developed. In contrast to bioartificial devices (“bioliver”), artificial devices (“liver dialysis”) are already widely used to support liver detoxifikation, especially MARS (Molecular Adsorbents Recirculation System; Gambro, Germany) and Prometheus (Fresenius Medical Care, Germany). Both systems remove protein-bound and watersoluble toxins from the blood with a different technical approach. In MARS, toxin removal takes place by diffusion over an albuminimpermeable membrane against a secondary circuit filled with albumin. The loaded albumin is then “recycled” by adsorber and low flux dialysis inside the secondary circuit. In Prometheus, the albumin fraction is separated into the secondary circuit through an albumin-permeable filter. There, the albumin fraction is directly purified by adsorber (Fractionated Plasma Separation and Adsorption; FPSA). Afterwards, high flux hemodialysis is performed. In-vivo comparisons of both systems demonstrated higher extraction capacities for bilirubin, urea and ammonia under Prometheus than under MARS.
Several publications have consistently reported an improval of hepatic encephalopathy and biochemistry for both systems. However, only a few randomized controlled clinical trials exist. Some of them described an improved survival in patients with liver failure. The FDA approval study confirmed the significant improvement of encephalopathy by MARS. Recent data suggest a reduction of portalvenous pressure. Further indications may be severe refractory pruritus and intoxications with protein-bound drugs. A cochrane metaanalysis of extracorporeal devices found a significant survival benefit for patients with acute-on-chronic liver failure despite the low number of controlled trials. In the meantime some large multicenter trials have been initiated, amongst them one for patients with acute liver failure (MARS) and for one patients with acute-on-chronic liver failure (Prometheus). The results of these trials should provide better insights into these new devices.