Introduction
Apheresis is a procedure in which blood from a donor or a patient is removed and separated into various components. The required component is removed, and the remaining components are returned to the bloodstream. The components of therapeutic apheresis are:
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Therapeutic plasma exchange (replacement of plasma).
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Cytapheresis.
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Extracorporeal photopheresis (isolation of white blood cells and exposure to ultraviolet radiation).
Therapeutic cytapheresis is a component of apheresis in which cellular components of the blood are removed to treat specific medical conditions.
What Is Therapeutic Cytapheresis?
Therapeutic cytapheresis is a procedure that removes specific pathologic cellular components from a patient's blood or collects a particular cellular component from a donor's blood. The procedure is performed in hematological, oncological, and infectious patients.
What Are the Uses of Therapeutic Cytapheresis?
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In patients with sickle cell disease, defective red blood cells (RBC) are removed to be replaced with normal ones. The procedure is indicated in patients with sickle cell disease (sickle-shaped RBCs are present) and stroke (damage to the brain due to blood supply interruption), pregnancy, acute chest syndrome (lung complication of sickle cell disease), and frequent or severe sickle cell crises. Replacement of RBC reduces hemoglobin S to less than 30 percent. However, a simple transfusion does not raise the risk of increased viscosity with increased hematocrit (increase in RBC volume).
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Acute leukemia patients undergoing therapeutic cytapheresis can reduce severe thrombocytosis (high platelet count) and leukocytosis (high white blood cell count).
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Therapeutic cytapheresis is performed on chronic myeloid leukemia (blood cell cancer originating in bone marrow) patients in the accelerated or blast crisis phase where there is a risk for thrombosis (blood clot), hemorrhage (bleeding within the body), and cerebral or pulmonary complications developing from extreme leukocytosis.
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The peripheral blood vessels are collected through therapeutic cytapheresis for autonomous or allogeneic bone marrow reconstitution (changes in bone marrow architecture).
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For immune modulation cancer therapy, lymphocytes are collected through therapeutic cytapheresis.
What Are the Types of Therapeutic Cytapheresis?
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Therapeutic Platelet Removal (Plateletpheresis or Thrombocytapheresis): The procedure is helpful in essential thrombocytosis, where platelets are removed and discarded. Platelets are not replaced rapidly as white blood cells (WBC), but one or two procedures can reduce platelet levels. However, the effect of the procedure lasts temporarily, and the platelet levels do not return to normal.
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Therapeutic WBC Removal (Leukocytapheresis): The procedure removes WBC from blood with few procedures and relieves leukostasis (WBC obstructs microvasculature). There is a temporary and mild reduction in WBC. The collected WBC cells are discarded while treating acute leukemia to reduce their count. Alternatively, the collected WBC cells are transfused if granulocytes or hematopoietic progenitor cells (stem cells) are collected. Leukocytapheresis is indicated in patients with hyperleukocytosis and symptomatic leukostasis.
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Therapeutic RBC Removal (Erythrocytapheresis): In patients, pathologic red blood cells are removed for therapeutic purposes, or one to two units of donor RBC are removed for blood transfusion. Erythrocytapheresis helps treat sickle cell anemia.
How Is Blood Collected for Therapeutic Cytapheresis?
The blood is drawn and returned through needles placed in arm veins or intravenous catheters. A blood thinner is added to the blood to prevent it from clotting within the machine. A small blood sample is collected to test for blood components and blood. About one cup of blood at a time is drawn outside the body into the machine. The procedure must be stopped if the blood clots within the machine or the centrifuge malfunctions. This can lead to loss of blood.
The most common blood thinners used are citrates. When added to the blood, citrate chelates with calcium and blocks calcium-dependent clotting factor reactions. It ensures that extracorporeal blood (blood outside the body) remains fluid and minimizes the activation of platelets and clotting factors.
What Is the Procedure for the Separation of Cellular Components in Blood?
Automated apheresis devices work on principles of centrifugation or filtration technology. The centrifugation procedure separates blood components depending on their specific gravity. The blood components separated are plasma, platelets, lymphocytes, monocytes, granulocytes, and red blood cells. The plasma is the least dense, and red blood cells have the highest density. The densest components are collected away from the axis of rotation, while the least dense components are collected close to the axis. The density of red cells and granulocytes is similar; therefore, they are poorly separated in centrifugation. Erythrocytapheresis removes only red blood cells from the peripheral circulation. Leukapheresis and plateletpheresis remove or collect white blood cells and platelets, respectively.
What Are the Indications for Therapeutic Cytapheresis?
According to the American Society of Apheresis (ASFA), the indications for therapeutic cytapheresis are considered as
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Category I - Indicated in patients with leukemia associated with hyperleukocytosis syndrome, sickle cell syndrome, and thrombocytosis. The disorders that accept therapeutic cytapheresis as the first line of therapy are considered for this category.
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Category II - Indicated in patients with cutaneous T-cell lymphoma (cancer of lymphatic T-cells), hairy cell leukemia (excess lymphocytes are produced by bone marrow), hyperparasitemia like malaria, and peripheral blood cell collection for hematopoietic reconstitution. Category II includes diseases with therapeutic apheresis as the second line of therapy.
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Category III - In patients with life-threatening hemolytic transfusion reaction, multiple sclerosis (immune system attacks outer covering of nerves), and sickle cell disease. In Category III, therapeutic apheresis is found to be not optimal.
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Category IV - In patients with leukemia without hyperleukocytosis syndrome and hypereosinophilia (increased eosinophil count). Disorders in which evidence shows therapeutic apheresis are ineffective or harmful are grouped in category IV.
What Is the Risk Associated With Therapeutic Cytapheresis?
The most common side effects are:
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Bruising from needle sticks or mild discomfort.
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Blood thinners lower calcium levels causing temporary numbness and tingling in the jaw and fingers to develop.
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Blood thinners produce a sour taste in the mouth.
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A blood count will fall following the procedure. There may be a 50 percent reduction in platelet levels which can cause spontaneous bleeding. However, loss of red blood cells does not need transfusion.
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Therapeutic cytapheresis may have to be repeated several times or may be less effective.
Less common symptoms include nausea, vomiting, fainting, anxiety, and severe cramping of muscles within the jaw and fingers. In rare instances, seizures may develop.
How Can Side Effects Be Prevented?
The steps to reduce side effects are slowing the procedure, administering calcium, and adding blood thinners to the blood within the machine to prevent it from clotting. Smaller or anemic patients may require the apheresis machine to be primed with red blood cells to prevent blood loss.
Conclusion
Therapeutic cytapheresis treats sickle cell anemia, thrombocytosis, and leukocytosis patients. The pathologic blood components or excess blood cells are removed and may or may not be replaced by donor cells. The procedure is generally safe with less risk for mortality. The procedure can have some side effects in patients that can be overcome by administering calcium, carrying out the procedure slowly, and adding blood thinners.
