Schematic diagram of the Molecular Adsorbents Recirculation System. Blood is dialysed against an albumin containing secondary circuit. The MARS® membrane allows passage of both water-soluble and the free fraction of protein-bound hepatic failure related toxins. In the secondary circuit, the albumin solution is regenerated by low-flux dialysis and passage over two adsorbent surfaces, an activated charcoal and an anion exchanger, respectively. For regional citrate anticoagulation, citrate is continuously infused in the afferent blood tubing, thus reducing ionized calcium concentrations at the MARS dialyzer inlet to 0.2 to 0.3 mmol·l-1. Restoration of blood calcium is by dialysis against dialysate containing Ca2+ at a concentration of 1.5 mmol·l-1. Systemic ionized calcium concentrations are repeatedly monitored during the procedure. If systemic calcium concentration falls below 0.8 mmol·l-1 despite calcium influx through the dialysate, additional CaCl2 is administered as an intravenous bolus injection. MARS, Molecular Adsorbents Recirculation System.