Molecular Adsorbent Recirculating System (MARS)

Non-biological artificial liver support system that utilizes albumin as dialysate to remove protein bounded toxins in liver failure patients.

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Components

3 interconnected circuits:

• Blood circuit: Where patient’s blood is cycled through by a roller pump
• Extracorporeal circuit: Containing 600 ml of 20% human albumin with a charcoal column and an anion exchange resin column
• Dialysate circuit: Consists of a specific dialyzer running in countercurrent.

MARS membrane:

High flux membrane with a pore size that renders the membrane impermeable to albumin molecules, essential proteins or hormones.

The membrane has an asymmetric configuration, with a tunnel-like porous structure over the blood side and a port and adsorption structure over the dialysate side. This unique design allows the transport of bilirubin and other albumin-bound toxins, but not the albumin molecule itself, to cross the membrane.

Toxins bound to the albumin molecule in blood are released by physiochemical reaction with the albumin-related binding sites of the membrane. These toxins then traverse the membrane by means of a non energy-dependent process, which is similar to the transport of bilirubin molecules along the sinusoidal membrane of the hepatocytes. The toxins are then taken up by the albumin in the dialysate side. The toxin load albumin dialysate passed through two cleansing cartridge to remove the toxins adsorbed to the albumin molecules and regenerate the dialysate online for recirculation.

The dialysate flow rate is the same as the blood flow rate but in countercurrent. The first cartridge consisted of vapor-activated charcoal which is not coated with cellophane. It is suitable for elimination for low molecular weight non-polar compounds such as phenols and fatty acids. The other cartridge consisted of ion-exchanger resin column and it functions to remove anionic molecules such as bilirubin. The third circuit is a renal replacement circuit.

The MARS system is compatible with most of the dialysis and hemofiltration machine on market. The renal replacement circuit serves to remove hydro-soluble toxins and urea, as well as regulate fluid, electrolytes and acid bases.

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Indications

• Acute liver failure
• Acute decompensation on chronic liver disease: Progressive jaundice, hepatic encephalopathy, renal dysfunction
• Intractable pruritus in cholestasis
• Acute intoxication/overdose with substances potentially bound to albumin
• Other indications:
  • Acute hepatic failure after major hepatectomy
  • After liver transplantation
    • Primary non-function or primary dysfunction of the graft
    • Acute decompensation of the graft (disease recurrence…)
    • Secondary liver failure or multi-organ failure