What is Apheresis?
Pheresis is from a Greek word that means subtraction or "to take away." The prefix "a" added to it means "separation," but apheresis and pheresis are often used interchangeably.
An apheresis unit's primary function is to provide treatments to patients who need specific components of their blood removed from their bodies. Today, most apheresis devices use centrifugation to accomplish this task.
To understand centrifugation, you must appreciate that blood has several parts. A good analogy is that blood is a lot like vegetable soup. The liquid portion of blood is the plasma. Much like soup broth, which has salts and flavoring dissolved in it, plasma contains proteins such as antibodies and clotting factors and comprises about 60% of your total blood volume. Just as soup contains a variety of vegetables, your blood also contains many different types of cells: red blood cells (which are the most numerous), platelets and different kinds of white blood cells.
During centrifugation, the blood goes into a machine called a separator, where it spins so fast that it separates into layers by density. The most dense red cells spin the farthest away, and the white cells lie on top of them. The platelets are smallest and least dense. The plasma lies in a thick layer on top and can be removed, if desired, with hardly any loss of blood cells. Alternatively, one particular layer of cells can also be collected and stored for later use, or removed and discarded so the patient's body can heal.
Who Needs Apheresis?
- People with myasthenia gravis, chronic inflammatory demyelinating polyneuropathy (CIDP), cold agglutinin disease, cryoglobulinemia, or TTP, may need a plasmapheresis
- Cancer patients undergoing chemotherapy may need cytapheresis
- People who have been unable to control their LDL ("bad") cholesterol with medication and a healthy diet may benefit from liposorption
- Protein A apheresis can be an effective treatment for patients suffering from rheumatoid arthritis
Apheresis/infusion units perform several types of procedures, including:
- Protein A apheresis
- Outpatient infusion and transfusion
Plasmapheresis is a procedure in which a large portion of a patient's plasma is removed and discarded and replaced with fresh donor plasma or a protein solution (human albumin). A physician will order this type of treatment if some substance in the patient's plasma is making him or her sick. If the substance, such as an antibody, is removed, the patient's health will hopefully improve. This procedure may be used for many diseases, including:
- myasthenia gravis (a chronic autoimmune neuromuscular disorder)
- chronic inflammatory demyelinating polyneuropathy (CIDP, an acquired immune-mediated inflammatory disorder)
- Cold agglutinin disease (CAD, an autoimmune disease)
- Cryoglobulinemia (abnormal proteins in the blood)
- TTP (thrombotic thrombocytopenic purpura, a clotting disorder often associated with viral infection or ingestion of bacterially contaminated food)
During cytapheresis, one particular type of cell is specifically removed from the spinning layers of blood. The most common type of cytapheresis is the peripheral blood stem cell (which is also called the peripheral blood progenitor cell) collection. These cells are the most flexible cells in your blood. Because your body can turn stem cells into various types of blood cells, they're very valuable in the treatment of some types of cancer. These cells are different from embryonic stem cells, and are less flexible.
Unfortunately, some cancers are so tenacious that only extremely high doses of chemotherapy will destroy them. But these high doses can also kill normal cells and leave the patient open to serious infections and other undesirable side effects. With cytapheresis, the stem cells are collected before chemotherapy, and returned to the patient—much like a transfusion—after the drugs have worn off. The patient avoids the drugs' strong effects and the normal cells survive to do their important work.
Liposorption is one of the newer procedures some apheresis units are now performing. During liposorption, the patient's blood is separated into cells and plasma, then the plasma is diverted over a column containing dextran sulfate. This material locks onto the LDL—or "bad"—cholesterol in the patient's blood and safely removes it without removing the HDL (good) cholesterol. The balance of plasma is then returned to the patient with his or her blood cells.
Doctors may recommend liposorption for patients who have high cholesterol levels that haven't responded to medications and diet. Some people have a genetic predisposition for high cholesterol. No matter how carefully they watch their diets and how faithfully they take their medications, their cholesterol levels are dangerously high. This condition can be detected with a blood test. Typically, patients undergo liposorption treatments every two weeks.
Protein A apheresis
Protein A apheresis separates the blood cells and plasma, then diverts the flow of plasma over a column containing a bacterially produced substance known as "Protein A" before returning it to the patient. The mechanism of action of how such columns of Protein A work is not exactly clear, but may involve the absorption and removal of certain types of antibodies or antibody/antigen complexes from one's circulation. Rheumatoid arthritis patients referred for Protein A apheresis typically undergo a course of 12 weekly treatments.
While you are undergoing a procedure in the unit, a pathology resident and attending physician will review your care plan and monitor your progress. The unit's registered nurses will attend to you throughout each procedure.
The unit is open Monday through Friday from 8 am to 4 pm, and closed on weekends and holidays, except for emergencies.