In some illnesses or poisonings there are substances in the blood that can cause harm. The blood plasma can be liberated from these substances by means of an apheresis procedure - by passing the blood through a device outside the body. The term apheresis generally refers to medical procedures whose therapeutic effect is the removal of constituents of the blood. The removal of these components takes place outside the body in a so-called extracorporeal circulation. The patient is connected to an apheresis device.
The best known form of apheresis, which is also called blood washing, is dialysis. In a number of diseases, special blood purification methods can specifically remove substances from the bloodstream and thereby positively influence the course of the disease. Among the best known methods of blood washing is dialysis, which takes over as a so-called renal replacement therapy in a disorder of the kidneys their function and removes toxic substances.
How does apheresis work?
Less well known as dialysis is therapeutic apheresis, which removes abnormal proteins, whitening substances or cells bound to whitening substances outside the body (extracorporeal). This is done either with the help of a filter (Membranplasmaseperator) or with a centrifuge. In principle, two approaches are distinguished:
- 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 purified of the pathogenic substances. This blood wash can be done in different ways:
- Unselective plasma exchange (plasmapheresis): Here the entire patient plasma obtained is discarded and replaced by a special nutrient solution.
- Selective plasma exchange: Here only the special pathogenic proteins (eg in autoimmune diseases) are removed with filter or other methods, the rest of the plasma is returned to the patient.
- Second possibility: The separation of blood plasma from the blood cells is waived, but the pathogenic substances are removed in the apheresis device directly from the whole blood using activated carbon or exchange resin (whole blood apheresis). This method is also called hemoperfusion.
The affected person receives in all cases two accesses usually via the veins - from one access the blood is taken, then passed through the apheresis device and returned to the cleaning and possibly adding replacement liquid through the other vein. Apheresis requires the close collaboration of the physician treating the underlying disease with the one performing the apheresis. Apheresis treatments are carried out on an outpatient basis but in special centers. There are currently about 100 apheresis centers in the Federal Republic of Germany, where treatments for lipometabolic disorders are mainly carried out.