Learningaboutbloodcomponentt
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BANKED BLOOD COMPONENTS ARE those components In 2002, a blood substitute with extended viability was of whole blood that are stored and administered in their released for use in South Africa. Hemopure, which is original biological form; that is, without pharmaceutical derived from bovine hemoglobin, is a chemically stabilized alteration. More than 20 million units of banked blood com- molecule that has the same oxygen-carrying capacity, ponents are transfused annually in the United States.1 This gram for gram, as human hemoglobin and has a half-life of article will focus on four components—packed red blood 24 to 48 hours. Hemopure molecules are much smaller cells (PRBCs), platelets, plasma, and cryoprecipitate—that than RBCs, have lower viscosity (resistance to flow) and are frequently used to treat trauma, surgical, and cancer release oxygen to the tissues more readily than RBCs.3 As a patients, as well as other patients who are experiencing a result, Hemopure may prove to be more useful than human deficiency as a result of physiologic or pathologic distur- RBCs in some cases of hypotension or in situations where bances. A fifth product, granulocytes, has practically the patient’s vessels are partially occluded. Human testing in disappeared from blood bank shelves, but because it still the United States started in 2003, but was stopped by the has minimal usefulness, I’ll discuss it briefly. FDA in 2005 when Creutzfeldt-Jakob disease (CJD) was Banked blood components are obtained, processed, and recognized in cattle.4 stored under guidelines from the American Association of Today the greatest relief for PRBC use is recombinant Blood Banks and the FDA, and retain all of their biological human erythropoietin therapy. The kidneys produce and properties. Adding preservatives and anticoagulants and release a hormone called erythropoietin, which stimulates removing cellular debris (such as leukocytes) extends the the production of RBCs. Recombinant human erythropoietin shelf life of components but doesn’t alter the biological has been used for years to help boost red cell production in features. Because the components contain the host’s bio- patients with diabetes whose kidneys have failed. In recent logical properties, the recipient may develop a reaction years, epoetin has proven beneficial in treating anemia that to the product. results from cancer chemotherapy; the drug stimulates bone marrow production of red cells. Packed red blood cells Two products, epoetin alfa and darbepoetin alfa, are on PRBCs are the most frequently used banked blood compo- the market. Because they’re expensive, their use may be lim- nent. They’re administered to patients with chronic or acute ited, although they’re often covered by insurance. For acute anemia to prevent or reduce the effects of anemia. To safe- blood loss and most other symptomatic anemias, red cell guard the blood supply, blood banks have developed review transfusion remains the treatment of choice. The use of boards to assure that the use of red cells is appropriate.2 whole blood is generally reserved for autologous transfu- PRBCs have a shelf life of 6 weeks under normal refriger- sions in the form of preoperative donation or cell savage. ation. Researchers are looking into ways to increase the shelf Autologous blood use not only increases patient safety, but life of fresh PRBCs to 11 weeks. With the addition of glyc- also reduces stress on the always-strained blood supply. To erol, red cells can be frozen and maintained at minus 65º C date, the use of homologous whole blood is recommended (minus 85º F) for 10 years or longer. After thawing, cells are only for patients requiring blood therapy after liver trans- deglycerized in a hypertonic saline bath and must be trans- plant, to reduce the number of donor exposures.2 fused within 24 hours.1 Frozen cells contain all of the prop- Leukocyte depletion, originally done only at the bedside, erties of refrigerated cells, but the process of washing may is now routinely performed on all processed units of PRBCs. reduce the cellular yield by as much as 10%. This not only increases the shelf life of the unit, it also The need for PRBCs continues to grow. Blood banks decreases the risk of nonhemolytic transfusion reactions— struggle to meet this need, and researchers are still stymied once the most frequent adverse reaction to transfusions.1 in their efforts to develop a suitable substitute. For years, Irradiated red cells are recommended for patients at risk perfluorocarbons have been considered as a potential hemo- for graft-versus-host disease (GVHD), a potentially fatal globin substitute because they have 100 times the oxygen disorder in which donor cells take over the immune sys- solubility of human blood. However, these products can’t tem. Irradiated cells have a shelf life of 28 days. However, sustain oxygenation for a sufficient length of time to be ben- irradiation can be performed at any time during storage so eficial in treating chronic or severe anemia.2 the normal shelf life may not be compromised. www.nursing2009.com April | Nursing2009 | 31 Platelets human thrombopoietin is good news for Platelets reside in the buffy coat portion cancer patients whose platelet stores Pharmacologic products of centrifuged blood, which appears as may be depleted from chemotherapy or can enhance platelet a whitish meniscus between the red radiation. The drug can be administered production, but haven’t cells and plasma. After the red cells are at home as a subcutaneous injection yet supplanted platelet expressed from a unit of blood, the plas- aimed at boosting platelet counts within therapy. ma is centrifuged a second time to con- 7 to 10 days, so cancer therapy can centrate the platelets further. Originally, continue with minimal interruption. platelets were administered as single- However, as with recombinant human donor units; because a therapeutic dose required 6 to 10 erythropoietin, recombinant human thrombopoietin is bene- units, patients were exposed to multiple donors with each ficial only when low platelet counts can be anticipated and transfusion. Today, platelet concentrates are more commonly the patient has adequate time for recovery. Another limiting used. These are obtained by apheresis or plateletpheresis, a factor is that recombinant human thrombopoietin therapy is process that returns blood to the donor after the platelets are associated with potentially fatal adverse reactions resulting removed.1 One unit of apheresis platelets contains a thera- from hepatotoxicity. New recombinant DNA products, now in peutic dose, and exposes the recipient to only one donor per clinical trials, are demonstrating efficacy in increasing platelet transfusion. Patients who require frequent transfusions can counts when the bone marrow is functioning normally. be matched to a designated donor who may donate as often However, patients with bone marrow suppression aren’t see- as every other day to provide 100% of the recipient’s needed ing a benefit. Therefore, these drugs may be used to increase platelets. the platelet yield from donors, but aren’t likely to be the treat- As with red cells, platelets may be irradiated before trans- ment of choice for thrombocytopenia.2 fusion to reduce the risk of GVHD. To reduce the risk of platelet alloimmunization and nonhemolytic febrile reac- Plasma tions, all units of platelets undergo leukocyte filtration (also Plasma, the major noncellular blood component, is a fluid called leukocyte depletion) to remove most of the white containing clotting factors, electrolytes, and proteins (includ- blood cells. Alloimmunization is a condition in which the ing albumin). The red and white cells and platelets are sus- body’s immune system sensitizes donor platelets, reducing pended in plasma. Plasma is routinely removed immediately their activity potential so that patients receive little benefit after blood donation, frozen, and stored for up to 1 year. from the transfusion. Fresh frozen plasma is indicated for: The removal of leukocytes before platelet storage has • preoperative or bleeding patients who need replacement potential ramifications. Leukocytes continue to exert an of multiple plasma coagulation factors (for example, pa- immunoresponse even during storage. Because RBC prod- tients with liver disease) ucts are stored under refrigeration, the risk of bacterial con- • patients receiving massive transfusions who have clini- tamination in leukocyte-reduced components is minimal. cally significant coagulation deficiencies Platelets, however, are stored at room temperature, and in the • patients taking warfarin who are bleeding or need to un- absence of leukocytes, provide an optimal medium for bacte- dergo an invasive procedure before vitamin K can reverse rial growth. Bacterial contamination is the second most com- anticoagulation, or who need to have anticoagulation ther- mon cause of death related to blood transfusions (after acute apy after the procedure hemolytic transfusion reaction), and platelets are the blood • patients who have thrombotic thrombocytopenic purpura component most likely to be contaminated with bacteria. and need a transfusion or plasma exchange To reduce the risk of infusing contaminated platelets, a • patients with selected coagulation factor deficiencies, sample from each unit is cultured and incubated until the congenital or acquired, for which no specific coagulation time of transfusion. If the culture is positive, the unit is concentrates are available pulled and immediately destroyed.