Current Topics on Cryofiltration Technologies

Abstract

In the last 40 years, therapeutic plasmapheresis techniques have been improving considerably. These include cryofiltration technologies providing novel ways of removing large amounts of cryoproteins from plasma. The concept of cryofiltration involves exposure of plasma to below core (37°C) and room temperatures (25°C) without freezing. It was initially used to treat diseases such as cryoglobulinemia with systemic vasculitis, rheumatoid arthritis, systemic lupus erythematosus, and ABO-incompatible transplants. There are 2 basic types of cryofiltration. The first method removes cryoproteins, namely cryoglobulins that precipitate at 4°C. Several filters have been used for this procedure like the AP06M (Asahi Medical, Tokyo, Japan) with a 0.2 m pore size, a 0.65 m 2 surface area, and a cellulose diacetate (CDA) membrane. It has been used in the United States and Japan for treatment of rheumatoid arthritis and cryoglobulinemia. A major disadvantage was frequent filter plugging, which was cumbersome and it is no longer used in the United States. The G3 cryofilter (Gelman Sciences, Ann Arbor, MI, U.S.A.) with a 3 m pore size was tried in vitro but proved inadequate by de-sign. Currently in our institution, the cryoglobulin filter (Pall Medical, Ann Arbor, MI, U.S.A.) is used with a 4.3 m pore size, a 0.135 m 2 surface area, and an acrylic copolymer pleat membrane. We performed over 1,200 procedures in 40 patients in the last 8 years. The second type of cryofiltration removes cryogel, which is an agglutination complex of fibrinogen, fibronectin, fibrin split products, and cold insoluble proteins with a heparin core, at temperatures between 2 and 10°C. The AP06M, the AC1740 (Asahi Medical) with a 0.02 m pore size, a 1.70 m 2 surface area, and a CDA membrane, and the Evaflux-4A (Kuraray Company, Osaka, Japan) with a 0.03 m pore size, a 2 m 2 surface area, and an ethylene vinyl alcohol membrane are used to remove cryogel to treat ABO-incompatible transplants as well as rheumatoid arthritis and other previously mentioned diseases. This article will discuss each cryofiltration treatment modality.

Heparin Cryoprecipitation Reduces Plasma Levels of Non-Traditional Risk Factors for Atherosclerosis in vitro

“…These studies indicated that 14 IU/ml of sodium heparin is the lowest level of heparin required for application of the HCP method (data not shown). Heparin, a highly charged polyanion, is capable of forming soluble and insoluble complexes with proteins, which upon freezing and the application of centrifugal force will accelerate their precipitation [17,18] . The precipitate or the cryogel is insoluble in cold temperatures but mostly soluble at 37 ° C, enabling its removal by centrifugation at lower temperatures.…”

New Options of Apheresis in Renal Diseases: How and When?

“…This technique is employed in selective removal of cryoglobulins and immunological complexes used in the treatment of cryoglobulinemia. Two types of cryofiltration are used: (1) removal of cryoglobulins precipitating in the temperature of 4 ° C and (2) removal of cryogel (anticoagulant complex consisting of fibrinogen, fibronectin, fibrin degradation products, cold insoluble proteins and heparin core) conducted in the temperature of 2-10 ° C [15,16] .…”

Therapeutic apheresis in special populations

“…This procedure selectively removes cryoproteins such as cryoglobulins to treat cryoglobulinemia and cryofibrinogen to treat cryofibrinogemia or any other cryoprotein to treat cryoprecipitate induced diseases [24,25]. In this procedure, plasma is separated, exposed to 48C in a thermoregulator unit, cryoprotein will be precipitated and removed by 4.3 micron pore size Cryofilter.…”