In apheresis, blood is removed from a person and then returned after substances are removed from it.
Apheresis can be used to
- Obtain healthy blood components from a donor to transfuse to a person with a disorder
- Remove harmful substances or excessive numbers of blood cells from the blood of a person with a disorder (termed therapeutic apheresis)
The different components of blood that can be separated include
- Red blood cells
- White blood cells
Plasma contains antibodies (immunoglobulins) and clotting factors, which are sometimes separated from plasma.
The two most common types of apheresis that are used to remove harmful substances from blood are
- Plasma exchange
Cytapheresis may have different names, depending on the type of cell that is removed from the blood.
- Plateletpheresis: Platelet removal
- Leukapheresis: White blood cell removal
When plasma is separated from the blood, the procedure is called plasmapheresis. Plasmapheresis is often done on blood from healthy donors to obtain plasma for donation or to obtain specific substances such as clotting factors.
Red blood cell exchange also involves apheresis.
In plasma exchange, the person's blood is removed, and the plasma is separated from the blood cells and platelets. The plasma is discarded and the blood cells and platelets are returned to the person along with a plasma-replacing fluid, such as albumin.
Plasma exchange is used to treat disorders in which the person's plasma contains harmful substances (often antibodies). Such disorders include multiple sclerosis, myasthenia gravis and Guillain-Barré syndrome (neurologic disorders that cause muscle weakness), Goodpasture syndrome (an autoimmune disorder involving bleeding in the lungs and kidney failure), cryoglobulinemia (a disorder involving formation of abnormal antibodies), and thrombotic thrombocytopenic purpura (a rare clotting disorder). Apheresis can help control some chronic diseases but generally does not cure them. However, thrombotic thrombocytopenic purpura can be reversed with apheresis.
To be helpful, plasma exchange must be done often enough to remove the undesirable substance faster than the body produces it. However, apheresis is repeated only as often as necessary because the large fluid shifts between blood vessels and tissues that occur as blood is removed and returned may cause complications in people who are already ill.
In cytapheresis, excess numbers of certain blood cells are removed. Cytapheresis can be used to treat polycythemia (an excess of red blood cells), certain types of leukemia (a type of cancer in which there are excess white blood cells), and thrombocythemia (an excess of platelets).
Red blood cell exchange
In red blood cell exchange, diseased or abnormal red blood cells are removed by apheresis and then replaced by donor red blood cells. Red blood cell exchange is used to treat or sometimes prevent serious complications of sickle cell disease, such as stroke and acute chest syndrome.