Apheresis: blood washing as therapy

Some diseases or poisoning have substances in the blood that can cause harm. The blood plasma can be freed from these substances by means of apheresis procedures – by passing the blood through a device outside the body. The term apheresis generally refers to medical procedures whose therapeutic effect consists in removing components of the blood. These components are removed outside the body in a so-called extracorporeal circuit. The patient is connected to an apheresis machine.

The most well-known form of apheresis, also known as  blood washing  , is dialysis. In the case of a number of diseases, special blood purification processes can remove substances from the bloodstream in a targeted manner and thus have a positive influence on the course of the disease. One of the best-known methods of blood washing is dialysis, which, as a so-called kidney replacement method, takes over the function of the kidneys and removes toxic substances.

How does apheresis work?

Less well known than dialysis is therapeutic apheresis, in which pathological proteins, pathogenic substances or cells bound to proteins are removed outside the body (extracorporeally). This is done either with the help of a filter (membrane plasma separator) or with a centrifuge. In principle, there are two different approaches:

  • In the apheresis device, the blood plasma is first separated from the blood cells (plasma separation ) and only in the second step is the plasma cleaned of the pathogenic substances. This blood washing can in turn be done in different ways:
    • Unselective plasma exchange  (plasmapheresis): Here, all of the patient plasma obtained is discarded and replaced with a special nutrient solution.
    • Selective plasma exchange : Here, only the specific disease-causing proteins (e.g. in autoimmune diseases) are removed using filters or other methods; the patient receives the rest of the plasma back.
  • Second possibility: The blood plasma is not separated from the blood cells, but the pathogenic substances are removed directly from the whole blood in the apheresis device using  activated charcoal  or exchange resin ( whole blood apheresis ). This method is also known as  hemoperfusion  .

In all cases, the affected person receives two accesses, usually via the veins – the blood is taken from one access, then passed through the apheresis device and, after cleaning and, if necessary, the addition of replacement fluid, returned through the other vein. Apheresis requires close cooperation between the doctor treating the underlying condition and the one performing the apheresis. Apheresis treatments are performed on an outpatient basis, but in special centers. There are currently about 100 apheresis centers in the Federal Republic, in which the treatment of lipid metabolism diseases is carried out.

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