Apheresis is a Greek word meaning “to take away”. It is performed using a machine that separates a person’s blood into its components (red blood cells, platelets, white blood cells and plasma) so one of its components can be selectively removed or replaced.
During an apheresis procedure involving donors, the blood is collected and returned via needles inserted into a vein in the arm. For patients, a central line or catheter inserted into a large vein in the upper chest is used to remove and return their blood.
As the blood comes in the machine, the blood cells separate into layers based on density.
“Red cells go to the bottom, white blood cells and platelets go in the middle and plasma goes to the top,” said Dr. Kathy Puca, pathology physician with Marshfield Clinic Health System. “Specific white blood cells have different density, so even those can layer within that middle layer.”
All of this occurs using a sterile closed system, with about an eight-ounce cup of blood outside of the body at any one time. As the machine removes or collects the desired portion, the rest of the blood cells go back into the body. Fluids such as albumin or saline are typically given to replace the portion that is removed.
An apheresis procedure can take from two to five hours, depending on the patient’s illness and what component needs to be collected. Apheresis is generally painless, though there may be some side effects.
During the apheresis procedure, a medicine known as an anticoagulant is mixed with the blood coming into the machine to stop the blood from clotting. This medicine can have some mild side effects that include tingling around the lips or in the fingers and toes, or feeling lightheaded or cold. To prevent these symptoms, patients are often given calcium during the procedure.
This technology has several uses in health care. Below are examples of apheresis procedures for different uses.
Donation of plasma and platelets
The most likely form of apheresis you have seen or experienced is the donation of plasma and platelets.
To donate plasma or platelets, you would undergo an apheresis procedure. Your blood would be removed, separated into layers and the donation center would remove the plasma or platelets from your blood.
At certain plasma donation centers, the plasma that is collected is further pooled and made into a simple form of protein called albumin, which is given to patients with shock following serious injury, undergoing surgery or with burns.
“Blood centers collect plasma by apheresis that is processed and frozen. This plasma is thawed at the hospitals and used for bleeding patients due to trauma or complex surgeries to replace clotting factors,” Dr. Puca said.
Stem cell transplants for cancer
Stem cells are immature cells that develop in the bone marrow and can grow into red blood cells, white blood cells, or platelets. Doctors may treat certain types of cancer, such as myeloma and lymphoma, using stem cell transplants. Before a stem cell transplant can occur, the patient must first have an apheresis procedure to harvest or collect some white blood cells and stem cells.
“First, we give a growth factor medication to increase the number of white blood cells, especially the stem cells which are immature bone marrow cells, in the blood stream,” said Dr. Puca. “We have specially trained nursing staff at Marshfield Medical Center that perform apheresis procedures to collect these stem cells.”
The apheresis procedure usually lasts for about five hours to collect an adequate amount of stem cells for two transplants in case of relapse.
The white blood cells are then processed and frozen until the patient has completed their chemotherapy or radiation treatments. If needed, the cells can be stored for up to 10 years after collection.
After the apheresis procedure is complete, the patient would come back for an intense round of chemotherapy, which wipes out their bone marrow. After treatment is complete, the white blood cells and stem cells collected during the apheresis procedure are then thawed and infused back into the patient, like a blood transfusion. The infused stem cells then grow and form bone marrow again.
This is called an autologous hematopoietic stem cell transplant because the patient provided his or her own white blood cells for the transplant. There is also a version of the treatment where the patient receives stem cells donated by a healthy person, which is called an allogeneic hematopoietic stem cell transplant.
Plasma and red blood cell exchanges
During therapeutic plasma exchange, the apheresis procedure removes the plasma component from the patient’s blood and replaces it with a new fluid. This removes an antibody that is causing the immune system to respond and attack healthy organs.
Therapeutic plasma exchange is a common treatment for autoimmune conditions where the body’s immune system attacks healthy cells in the nervous system such as Guillain-Barré syndrome and myasthenia gravis. It is also a common procedure done as part of a treatment protocol when a patient is rejecting a solid organ transplant.
Red blood cell exchange does the same thing, but instead of removing the plasma, abnormal red blood cells are removed and replaced with healthy red blood cells from donors.
Individuals with sickle cell disease are more prone to strokes because their sickled cells tend to stick together, which can cause their blood to clot more easily. Patients with this condition undergo apheresis to exchange red blood cells, which prevents reoccurring strokes.
For more information about apheresis, talk to your doctor.