The process of apheresis involves removal of whole blood from a patient or donor. Within an instrument that is essentially designed as a centrifuge, the components of whole blood are separated.
One of the separated portions is then withdrawn and the remaining components are retransfused into the patient or donor.
Roughly 250,000 plasmapheresis therapies are performed worldwide annually. The main purpose of therapeutic plasmapheresis is to treat auto-immune illnesses (e.g. rheumatoid arthritis) and sepsis (blood poisoning) and, in a specialized form, remove high concentrations of lipoproteins (blood lipids such as LDL cholesterol) directly from the blood or plasma.
This special form of plasmapheresis is termed LDL apheresis. A direct removal of lipoproteins from the blood is termed full-blood apheresis. If only the plasma is to be treated, a differentiation is made between non-selective and selective LDL apheresis.
In the case of semi-selective LDL apheresis (cascade filtration), the plasma is filtered in an additional second stage purely according to the size of the plasma proteins. However, desirable plasma constituents are also eliminated in this process.
In the case of the selective variant (H.E.L.P. apheresis), only certain (pathogenic) blood lipids are eliminated from the separated blood plasma. About 2000 patients worldwide are treated annually by means of LDL apheresis, 25% of them receiving the H.E.L.P. therapy.
Introduced 25 years ago, H.E.L.P. LDL apheresis has been used to treat 300,000 individual cases to date.
The components which are separated and withdrawn include:
- Plasma (plasmapheresis)
- Platelets (plateletpheresis)
- Leukocytes (leukapheresis)
In the diagram below, the process is illustrated. Whole blood is introduced into a chamber that is spinning, and the blood separates into components (P = plasma; PRP = platelet rich plasma; WBC = leukocytes; RBC = red blood cells) by gravity along the wall of the chamber.
The component to be removed can be selected by moving the level of the aspiration device at the right. In this example, plasma is being removed.
Adsorbers remove pathogenic substances from the blood
The treatment of blood outside the body by means of adsorbers is a new and innovative therapy concept based on the selective removal of undesirable and pathogenic substances from the blood. It is used for those patients in particular who have diseases which cannot be treated successfully by conventional methods.
The following diseases can be treated with the new technology:
- hypercholesterolaemia, a hereditary lipometabolic disorder
- auto-immune diseases such as lupus erythematosus as well as
- dilatative cardiomyopathy
- certain forms of nephritis, disorders of blood coagulation
- organ rejection
The process is very effective and extremely well tolerated as the patients are not given any drugs. For instance, the DALI system enables LDL cholesterol to be removed from whole blood for the first time.
As a result of the treatment, the development of coronary heart disease can be influenced in a positive way.
Treatment of blood outside the body
In all adsorber treatments, the blood flows through a tube from a vein in the arm of the patient into the adsorber.
The various adsorbers contain different materials which, like a sponge, selectively extract the undesirable and pathogenic substances from the blood.
The cleansed blood is then returned to the patient via the vein in the other arm. A special machine pumps the blood through the adsorber and monitors the blood circulation outside the body.
The purpose of therapeutic apheresis is to remove a component of the blood which contributes to a disease state. Examples include:
Plasmapheresis: within the plasma are contained antibodies and antigen-antibody complexes that may contribute to the deleterious effects of autoimmune diseases.
Removal of the plasma (and replacement with saline solution) will help to reduce circulating antibodies and immune complexes.
In rare circumstances, excess blood proteins are present that may cause circulatory problems. Examples of these diseases include:
- Waldenstrom’s macroglobulinemia
- Myasthenia gravis
- Guillain-Barré syndrome
- Hyperviscosity Syndromes
- Goodpasture’s syndrome
Plateletpheresis: rarely, in myeloproliferative disorders, the platelet count can be very high (thrombocytosis). Removal of platelets can help to avoid complications of thrombosis and bleeding.
Leukapheresis: in some cases of leukemia with very high white blood cell counts, removal of the excess leukocytes may help to prevent complications of thrombosis.
Stem Cell Harvesting: the small number of circulating bone marrow stem cells can be harvested to use in transplantation procedures.