Apheresis is a automated machine-assisted procedure in which blood is removed from a patient through an intravenous line. The blood is fed into an apheresis machine where it is centrifuged to separate the blood into parts (Red Blood Cells, Plasma, Platelets, White Blood Cells). Individual components can be harvested and the remainder of the components can be returned back into the patient. Apheresis can be used as a way to donate Red Blood Cells, Platelets, Plasma, Granulocytes, Stem Cells, etc., but also as a therapeutic procedure for many conditions.
|The TerumoBCT Spectra Optia is a common CFC|
apheresis machine and a popular choice for therapeutic apheresis.
The majority of new apheresis technologies on the market are CFC based. Haemonetics makes most of the IFC-based apheresis machines in the market today such as the MCS+,PCS2, and CYMBAL. They've also made S-30 and V-50 machines in the past. Trima Accel, Optia Spectra, Cobe Spectra, Amicus by Fresnius Kabi are some of the more popular and commonly used CFC devices.
Typically, it is required to perform some calculations prior to performing an apheresis procedure to ensure the proper amount of blood is removed and returned. Most importantly the Total Blood Volume of a person must be calculated. It is not enough to assume the "average" of 5.0 liters. Typically this calculation involves a patient's height, weight, and sex. Depending on the procedure, it may be necessary to know the patient's hematocrit, plasma volume, pre-transfusion Hemoglobin S percentage, etc. Many of the automated systems will perform a Total Blood Volume or plasma volume calculation right in the software.
- Red Blood Cells -- Apheresis can be used to donate Red Blood Cells. The machine will separate the Red Blood Cells to collect and return plasma, platelets, and white blood cells back to the patient. This donation type is often termed "Power Reds" or "Double Reds" due to the fact that the collection results in a donation of two whole Red Blood Cell units compared to just one during a normal gravity fed whole-blood donation. Patients must meet a strict height and weight minimum to be able to donate with their blood donation center. There is generally a minimum Hemoglobin requirement as well which is usually 13.3g/dL. Patients will generally have less side effects compared to typical whole blood donation, because their plasma is being returned.
- Plasma --- The process is also known as Plasmapheresis -- Blood plasma can be donated via apheresis as well. The procedure has the ability to collect up to four times the amount of plasma that would be donated during a normal whole blood donation. This is especially important for patients who are type AB. Type AB plasma is compatible with all blood types, which makes it a top choice for emergent situations, such as a trauma, when a patient's blood type may not be yet known. Depending on the patient's blood volume, enough plasma may be collected to process up to four entire units of plasma. Plasmapheresis is the preferred donation method for type AB patients for this reason! Patients can generally donate every 28 days. That's 13 times a year!
- Platelets -- Platelets collected via apheresis are typically the most common type of platelet available on a transfusion center Blood Bank's shelf. Some blood centers do still offer pooled platelets collected from several whole blood donations, but they are much less common these days. Apheresis platelet collection is also the preferred method of collection for platelets. Depending on the platelet count and blood volume of a patient, an apheresis procedure can procure up to three entire units of platelets. This is especially important because platelets are in constant need. A unit of platelets is only good for 3-5 days once it reaches a transfusion center Blood Bank. A platelet donor can donate much more often than Red Blood Cells or plasma. It may depend on the blood center, but the American Red Cross for example, allows donation of platelets every 7 days.
- Granulocytes -- Granulocytes (a type of White Blood Cell) can be donated to those battling severe infection who don't have a functioning immune system to fight the infection by themselves and haven't responded to antimicrobials. This is not a routine donation, and blood centers will generally contact previously known donors (such as frequent apheresis platelet donors) to come in and donate granulocytes. Donors, especially in the United States may be given Granulocyte Colony Stimulating Factor (G-CSF) to stimulate the production of excess granulocytes that can then be harvested in greater numbers during apheresis.
- Stem Cells -- The most common form of hematopoietic (blood) stem cell donation today is through apheresis. Donors will typically be asked to receive injections of Filgrastim (Neupogen) for a few days prior to donating. Filgrastim forces tells the bone marrow to make more cells, and in doing such creates a higher concentration of circulating hematopoietic (blood) stem cells in the donor as well. The vast majority of donors have a high enough stem cell count that they only need to donate once after being stimulated with Filgrastim. The recipient requiring a stem cell transplant can then receive the hematopoietic stem cell donation via simple intravenous infusion like any other blood product.
- Sickle Cell Disease --- patients who consistently have higher Hemoglobin S counts and are prone to sickle cell complications or HAVE such complications as Sickle Crises, Acute Chest, stroke, etc., are the most common population to benefit from Red Blood Cell exchanges. The apheresis process can remove a large portion of the patient's sickled blood and replace it with donor NON-sickled (Hemoglobin S negative) blood. The procedure will not remove 100% of Hemoglobin S positive cells in one procedure. Many patient's who meet the criteria will be set up on a schedule and get regular, usually monthly RBCX transfusions. This procedure can help relieve symptoms from the previously mentioned as well as relieve issues such as iron overload that may be seen in sickle patient's who receive frequent simple transfusions. Using an automated apheresis also allows the clinical team to accurately input values to achieve a target post-transfusion HgbS count as well as hematocrit.
- Intracellular Infection -- Patients with severe intracellular parasitic protozoan infections such as Babesia or Malaria with a high parasitic load may benefit from Red Blood Cell exchange therapy to lower the amount of parasite-infected Red Blood Cell within the body. This is usually done in conjunction with other therapies and is not the first line therapy. With Malaria apheresis may be indicated when %parasitemia reaches 30% or greater in patient's without excess complications, and 10% or greater with patient's with infection complications. Babesia infected patients will generally benefit from apheresis if there %parasitemia is 10% or greater who have severe symptoms or are at high risk of complications. This is not commonly performed and typically other methods of treatment will be sought first.
- Incompatible Hematopoietic Stem Cell Transplant -- Patient's receiving ABO incompatible hematopoietic stem cell transplants may have their allogeneic stem cell collection Red Blood Cell depleted which lowers the amount of incompatible Red Blood Cells that they may come in contact with. This is done to prevent any immediate hemolyzing event upon infusion of the product.
- Erythrocytosis -- Patients with a erythrocytosis (excess Red Blood Cells in circulation) may benefit from an apheresis procedure designed to lower the amount of the red blood cells in circulation to prevent or alleviate symptoms caused by too many Red Blood Cells in circulation. The removed blood is generally replaced with 4% albumin. Erythrocytosis can be caused by Polycythemia vera, a type of cancer, or by other secondary causes. Erythrocytapheresis (Red Blood Cell apheresis) is more likely to be performed on a patient with Polycythemia vera than a patient with secondary causes of erythrocytosis.
- Hereditary Hemochromatosis -- Patient's with hereditary hemochromatosis have a genetic predisposition to retain more iron than is actually needed. The iron builds up in the body and can begin to exhibit toxic affects on the body and organs. One way to remove excess iron is by removing portions of the blood at given intervals. Often times, this is done by a simple phlebotomy where blood is drawn into a bag (similar to donating blood) and discarded. Depending on the indications and conditions of the patients apheresis may also be used to achieve this. Some studies have shown it is more effective in reducing the iron storage overload over traditional phlebotomy methods.
- Thrombotic Thrombocytopenic Purpura (TTP) -- Patient's with TTP often have an autoantibody inhibiting the function of an enzyme known as ADAMTS13. This enzyme helps to ensure von-Willebrand factor/platelet complexes do not grow out of control and form clots within the circulating blood. Patient's with TTP are at an extreme risk of clotting due to this inhibition, but also bleeding because platelets are used up in this process of inhibition as well. Donor FFP units, which should have normal levels of ADAMTS13 and no autoantibodies, are generally used in this instance to replace the patient's plasma.
- Myasthenia gravis (MG) --- MG is an autoimmune condition in which autoantibodies (antibodies directed towards part of yourself) attack specific neuromuscular targets such as nicotinic acetylcholine receptor or Muscle-Specific Kinase which can lead to skeletal muscle weakness and fatigue. Patient's with MG can typically get rounds of plasmapheresis which can remove their plasma containing the harmful autoantibodies and replace it with an albumin solution.
- Goodpasture Syndrome -- Goodpasture Syndrome is another autoimmune disease in which autoantibodies are created towards the "Basement Membrane" of the lungs and/or kidneys. These antibodies can eventually lead to the destruction of lung and kidney tissue which can cause bleeding in the lungs, hemoptysis (coughing up blood), and glomerulonephritis/kidney damage. A plasma exchange with albumin can help remove these autoantibodies from causing damage.
- Guillain-Barre syndrome - Patient's with Guillain-Barre syndrome have autoantibodies directed towards the peripheral nervous system (as opposed to the Central Nervous System such as brain or spinal cord) and sometimes the myelin sheath, which protects and insulates nerve cells causing pain and muscle weakness/fatigue. Plasmapheresis is a usable treatment to remove the antibodies from the patient's plasma.