Coupled Plasma Filtration Adsorption: A Multipurpose Extracorporeal Detoxification Therapy

Coupled plasma filtration adsorption (CPFA) is a detoxification system that combines a plasma adsorption circuit with a continuous renal replacement therapy. The circuit consists of a plasma filter, a resin/adsorbent cartridge and a haemofilter. It differs from many other types of extracorporeal therapies in that the upper part of the circuit can be considered a “closed loop”. In this manner, the plasma separated by the plasma filter passes through an adsorbent cartridge containing a resin with high affinity to many cytokines, mediators and toxins/poisons. After passing through the cartridge, the purified plasma is returned to the patient. The second part of the circuit, the haemofilter, can then be used to remove small toxins that are not adsorbed by the resin or to modulate the patient hematic volume. Although more complex, the use of a plasma-separation step prior to the passage through the resin cartridge offers advantages over adsorption by haemoperfusion. The plasma passes through the resin cartridge with a lower velocity than the blood flow, and this allows better contact time for the toxins with the resin, and more thorough penetration into the resin pores. The adsorption of many toxins is highly dependent on a factor expressed as linear velocity. In addition, the plasma does not contain cells or a very limited number of platelets, allowing less potential activation upon contact with the resin. Although the technique was originally developed for the treatment of sepsis and septic shock, there are many additional applications where there can be an advantage of having access to larger molecular weight toxins (compared to haemofiltration) and avoiding the loss of important physiologic substances such as albumin. Some of these new applications, in patients with or without acute kidney injury, include liver failure, rhabdomyolysis, severe autoimmune exacerbations and poisonings. In this article, we discuss some of the basic principles involved in sorbent technology, and how these may contribute to treatment efficacy, review the actual experiences with CPFA and finally discuss the results of recent human studies and their implications.