Either whole blood or blood components can be used for transfusion. Whole blood is used exactly as it was received from the donor. Blood components are parts of whole blood, such as red blood cells (RBCs), plasma, platelets, clotting factors, immunoglobulins, and white blood cells. Whole blood is used only when needed or when components are not available. Most of the time, whole blood is not used because the patient's medical condition can be treated with a blood component. Too much whole blood can fluid-overload a patient's circulatory system. This can create high blood pressure and congestive heart failure (overwork of the heart muscle to pump the extra fluid volume). The use of blood components is more efficient and effective because blood that has been fractionated (processed) into components can be used to treat more than one person.
Plasma is the liquid portion of blood. It contains many useful proteins, especially clotting factors and immunoglobulins. After they are processed, plasma or plasma factors (fractions) are usually frozen. Some plasma fractions are freeze-dried. These fractions include clotting factors I through XIII. Some people have an inherited disorder in which the body produces too little of the plasma clotting factors VIII (hemophilia A) or IX (hemophilia B). Transfusions of these clotting factors help people with hemophilia to stop bleeding. Frozen plasma must be thawed before it is used and freeze-dried plasma must be mixed with liquid (reconstituted). In both cases, these blood fractions are usually small in volume and can be injected by syringe and needle.
Red blood cells are the blood component most frequently used for transfusion. RBCs are the only cells in the body that transport oxygen. A transfusion of RBCs increases the amount of oxygen that can be carried to the tissues of the body. RBCs that have been separated from the liquid plasma (packed RBCs) are given to people who have anemia (low red cell count) or who have lost a lot of blood. There are many causes of anemia. In cancer, anemia is caused by the destruction of red blood cells by disease, by medications such as chemotherapy, or by disease in the bone marrow where red blood cells are produced. To determine how serious the anemia is, the physician will do a CBC (complete blood count) to look at the hemoglobin level (the oxygen-carrying capacity of the red blood cells), and a hematocrit (the percentage of RBCs in a given volume of blood).
Platelets are another component frequently given by transfusion. Platelets are a key factor in blood clotting. The clear fluid that carries blood cells (plasma) also contains blood-clotting factors. The platelets and plasma clotting factors are extracted from donated blood and concentrated for use. These factors are used to treat
Immunoglobulins, also called gamma globulin or immune serum, are collected from plasma for use in temporarily boosting the immune capability of a patient. White blood cells (WBCs) are another infection-fighting component of the blood. White blood cells are given by transfusion only rarely. Immunoglobulins are the infection-fighting fraction of blood plasma. This blood fraction is given to people who have difficulty fighting infections, especially people whose immune systems are depressed by diseases, such as HIV/AIDS and cancer. Immmunoglobulins are also used to prevent tetanus after cuts, to treat animal bites when rabies infection is suspected, or to treat severe childhood diseases. Immunoglobulins can also be used to treat idiopathic thrombocytopenic purpura (ITP), a condition characterized by a low platelet count and excessive bruising.
Granulocytes are a type of white blood cell that fight infection. Granulocyte transfusion is no longer done because of the fever it produces and the potential transmission of infectious diseases through white cells. These infections (CMV or cytomegalovirus) would be particularly dangerous to a cancer patient with a weakened immune system. Chemotherapy patients can develop a low WBC (white cell count). A specific white blood cell called the neutrophil is carefully monitored because it is very important in fighting multiple types of infection. If neutrophil counts are very low, the physician may order special medications that stimulate the production of neutrophils in the bone marrow. These medicines are called colony-stimulating factors or growth factors, and include granulocyte colony-stimulating factor (G-CSF or filgrastim), granulocyte macrophage colony-stimulating factor (GM-CSF or sargramostim), and interleukin-3.
Researchers have been working to develop a substitute for blood that will avoid the risks associated with blood transfusion. Products are being developed that will perform the functions of red blood cells, such as carrying oxygen through the blood stream, but there is no real substitute for the transfusion of human blood. Two products that are currently available are known as hemoglobin-based oxygen carriers and perfluorochemical compounds. These products can be used on a short term basis to perform the function of blood, but are still considered experimental.
Other types of products that can help patients in need of large volumes of body fluids are volume expanders such as normal saline solution, lactated ringers, or dextran. These are IV (intravenous) solutions that can replace lost fluid volume but not the red blood cells' function of carrying oxygen to the body. Other volume expanders include albumin, a protein solution used to stabilize oncotic pressure (pressure within the veins) and prevent or treat shock. Growth factors, as mentioned earlier, help promote the production of specific white cells needed to fight infections. Erythropoietin and thrombopoietin are products available to help stimulate the production of red blood cells and platelets. None of these products replace the benefits of blood or blood component transfusions.
Researchers are looking at the efficacy of using sibling blood components, specifically transfusions of stem cells and T-cells, a part of the immune system that can attack and destroy cancer cells. Blood from tissue-matched sibling donors reduces the rejection rate by the patient's body chemistry. This technique is being studied in renal (kidney) tumors, and early results show promise. Researchers are particularly interested in this therapy for renal tumors with metastasis (spreading of the cancer to other parts of the body) because this type of cancer does not usually respond to standard cancer therapy protocols. While blood transfusions and bone marrow transplants have been used extensively for cancers of the blood, this is the first time transfusions have been successful in the treatment of solid tumors (such as renal tumors).
Researchers are also looking at the placenta and umbilical cord as a source for blood stem cells for transplant. This method is called cord blood transplantation. It offers an alternative for patients who do not have a sibling donor, or cannot locate a match in the National Marrow Donor Program (NMDP) registry.
Each year in the United States, about 14, 000, 000 pints of blood are donated. Blood collection is strictly regulated by the Food and Drug Administration (FDA). The FDA has rules for the collection, processing, storage, and transportation of blood and blood products. In addition, the American Red Cross, the American Association of Blood Banks, and most states have specific rules for the collection and processing of blood. The main purpose of regulation is to ensure the quality of blood and to prevent the transmission of infectious diseases through donated blood. Before blood and blood products are used, they are extensively tested for infectious agents, such as hepatitis and HIV/AIDS. Screening prevents blood donation by people who could transmit diseases or by people whose medical condition would place them at risk if they donated blood. Some geographical areas or communities have a high rate of hepatitis or HIV/AIDS. Blood collection in most of these areas has been discontinued.
Autologous transfusion is a procedure in which patients donate blood for their own use. Patients who are to undergo surgical procedures for which a blood transfusion might be required may elect to donate a store of blood for the purpose ahead of time. The blood is stored at the hospital for the exclusive use of the patient. This procedure assures that the blood type is an exact match. It also assures that no infection will be transmitted through the blood transfusion. This is most helpful to cancer patients because of the reduction of risk for a transfusion reaction and for infection risks associated with transfusions. As with other forms of specialized blood donations, there is a processing fee for collection and delivering each unit of blood, which may not be reimbursed by health insurance.
Directed donors are family or friends of the patient who needs a transfusion. Some people think that family and friends provide a safer source of blood than the general blood supply. Studies do not show that directed donor blood is any safer. Blood that is not used for the identified patient becomes part of the general blood supply.
Apheresis is a special procedure in which only the necessary components of a donor's blood are collected. The remaining components are returned to the donor. A special blood-processing