Uncontrolled trial of cryofiltration in rheumatoid arthritis

Use of Therapeutic Apheresis methods in ICU

Apheresis is a modern medical approach in which plasma or cellular components are separated from the whole blood. Apheresis can be either diagnostic or therapeutic. Diagnostic apheresis is typically applied in hematology and cancer research. Therapeutic Apheresis (TA) includes a broad spectrum of extracorporeal treatments applied in various medical specialties, including Intensive Care Unit (ICU). Considering the complexity of the pathophysiologic characteristics of various clinical entities and in particular sepsis, apheresis methods are becoming increasingly applicable. Therapeutic Plasma Exchange (TPE) is the most common used method in ICU. It is considered as first line therapy for Thrombotic Thrombocytopenic Purpura (TTP) and Guillain Barre Syndrome, while the current data for sepsis are scarce. Over the last decades, technologic evolution has led to increasing application of new and more selective methods based on adsorptive techniques. In this review we will describe the current data of characteristics of different techniques, safety and clinical impact of apheresis methods used in ICUs.

Therapeutic apheresis in autoimmune diseases

Systemic autoimmune diseases based on an immune pathogenesis produce autoantibodies and circulating immune complexes, which cause inflammation in the tissues of various organs. In most cases, these diseases have a bad prognosis without treatment. Therapeutic apheresis in combination with immunosuppressive therapies has led to a steady increase in survival rates over the last 35 years. Here we provide an overview of the most important pathogenic aspects indicating that therapeutic apheresis can be a supportive therapy in some systemic autoimmune diseases, such as systemic lupus erythematosus, antiphospholipid syndrome, rheumatoid arthritis, and inflammatory eye disease. With the introduction of novel and effective biologic agents, therapeutic apheresis is indicated only in severe cases, such as in rapid progression despite immunosuppressive therapy and/or biologic agents, and in patients with renal involvement, acute generalized vasculitis, thrombocytopenia, leucopenia, pulmonary, cardiac, or cerebral involvement. In mild forms of autoimmune disease, treatment with immunosuppressive therapies and/or biologic agents seems to be sufficient. The prognosis of autoimmune diseases with varying organ manifestations has improved considerably in recent years, due in part to very aggressive therapy schemes.

The selective therapeutic apheresis procedures

Selective apheresis procedures have been developed to target specific molecules, antibodies, or cellular elements in a variety of diseases. The advantage of the selective apheresis procedures over conventional therapeutic plasmapheresis is preservation of other essential plasma components such as albumin, immunoglobulins, and clotting factors. These procedures are more commonly employed in Europe and Japan, and few are available in the USA. Apheresis procedures discussed in this review include the various technologies available for low-density lipoprotein (LDL) apheresis, double filtration plasmapheresis (DFPP), cryofiltration, immunoadsorption procedures, adsorption resins that process plasma, extracorporeal photopheresis, and leukocyte apheresis.

Birth of the concept and the development of extracorporeal immunomodulation

Extracorporeal immunomodulation is a term that presents the concept and techniques of a group of therapeutic procedures by which immunological circumstances in a patient's body, suppression or activation, drastically are altered by applying extracorporeal circulation. This had been achieved only by administration of the pharmacological agents, such as immunosuppressive agents before the introduction of extracorporeal immunomodulation. From the view of removal of the pathogenic substances in the circulating blood, it is regarded as belonging to the blood purification procedures. In respect to the technology, plasmapheresis is an important and a key procedure in most of the cases. The concept and current clinical practices are described in the text.

Current topics on cryofiltration technologies

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 degrees C) and room temperatures (25 degrees 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 degrees C. Several filters have been used for this procedure like the AP06M (Asahi Medical, Tokyo, Japan) with a 0.2 microm pore size, a 0.65 m2 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 microm pore size was tried in vitro but proved inadequate by design. Currently in our institution, the cryoglobulin filter (Pall Medical, Ann Arbor, MI, U.S.A.) is used with a 4.3 microm pore size, a 0.135 m2 surface area, and an acrylic co-polymer 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 degrees C. The AP06M, the AC1740 (Asahi Medical) with a 0.02 microm pore size, a 1.70 m2 surface area, and a CDA membrane, and the Evaflux-4A (Kuraray Company, Osaka, Japan) with a 0.03 microm pore size, a 2 m2 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.

The current status of extracorporeal immunomodulation

A course of extracorporeal immunomodulation is defined as a treatment which intervenes and consequently modulates or, in other words, activates and/or suppresses the immune mechanisms utilizing an extracorporeal procedure. Such treatment has traditionally depended on administration of drugs, typically steroids and/or immunosuppressants. Most of the apheresis techniques currently available belong to or are very similar to those used for blood purification and involve the removal of the pathogenic substances such as antibody(ies) and/or immune complex(es). The cellular components are also treated in extracorporeal immunomodulation. As some of the extracorporeal immunomodulation techniques have already demonstrated clinical effectiveness that cannot be achieved by conventional therapies, it is appropriate to propose a new therapeutic approach to the immunological disorders.

Artificial liver. State of the art

If an effective hepatic assist system existed, it could serve as a bridge to transplantation. Most of the patients waiting for liver transplantation have chronic liver insufficiency but are not in hepatic coma. Various hepatic assist systems have been used to salvage patients with acute liver insufficiency. Most attempts have been disappointing. The methods used have included plasma exchange, plasma adsorption, double filtration, cryofiltration, thermofiltration, the combination of plasma exchange and amino acid hemodialysis, and others. For patients with chronic liver disease with moderate liver function impairment and limited to one or only a few areas of metabolic abnormality, a hepatic assist might allow the life of the patient to be maintained temporarily. The application of hepatic assist methods for chronic liver disease patients treated at the Cleveland Clinic has been encouraging. One of the patients who suffered from sclerosing cholangitis has maintained a near-normal life for almost five years by 170 plasma treatments. This is in spite of the fact that, at the onset of treatment, the patient was nearly comatose. Unfortunately, this patient did not wish to receive a liver transplantation. Based upon this experience, the concept of a bridge to transplantation approach to hepatic assist devices appears feasible. In addition, it is speculated that hepatic assistance during the early recovery stage of liver transplantation and during mild episodes of rejection may be useful.