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Veterinarian Technician August 2010 (Vol 31, No 8)

Transfusion Medicine: Component Therapy

by Kara Trent, CVT, VTS (Anesthesia, ECC)

    CETEST This course is approved for 1.0 CE credits

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    With the increasing availability of various blood products, understanding and effectively using these products have become more important for veterinary staff. The technician’s role is facilitated by having a general understanding of the principles of transfusion medicine. Component therapy, which is currently recommended for administering transfusions, allows precise and efficient use of blood products and decreases the risk of adverse reactions.1

    Collecting Fresh Whole Blood

    Currently, the demand for blood products exceeds the supply of the few veterinary commercial blood banks in the United States. Some hospitals use in-house donors, which incurs expenses, including feeding, housing, and general patient care. Another option is recruiting donors through clients, employees, or the general public.2

    Regardless of the source, all donors should be screened and routinely evaluated by a veterinarian. Screening and routine evaluation should include a general health examination, appropriate vaccinations, administration of heartworm preventives, blood typing, and testing for endemic disease.3 Body weight should be ≥27 kg (≥59.4 lb) for canine donors and ≥5 kg (≥11 lb) for feline donors.2 Blood collection is often performed and overseen by veterinary technicians; therefore, it is important for technicians to know the requirements for donation and the importance of sterility during blood collection.

    Canine Blood Donation

    Dogs can donate a standard unit (450 mL) of whole blood every 3 weeks without negative effects.2 During blood collection, some dogs require sedation. However, careful selection of calm donors reduces the need for sedation. If sedation is necessary, acepromazine should be avoided because it can cause hypotension and alter platelet function.4,5 The preferred collection site is the jugular vein. Typically, placing the donor in lateral recumbency is preferred for blood collection, but patient positioning should be determined by the collector’s preference and skill. Blood can be collected by gravity or suction, depending on the supplies at the facility. Many types of blood collection bags as well as anticoagulant and preservative solutions are available.2 Typically, a closed system of collection and separation is recommended. With the closed system, the blood is not exposed to the environment during collection or separation.2 This minimizes the risk of bacterial contamination and allows rapid storage of whole blood or its components. To ensure sterility during blood component preparation, the use of plastic blood bags with satellite transfer containers is optimal.4 Blood products should be separated by centrifugation within 8 hours of collection. Packed red blood cells (pRBCs), platelet-rich plasma, platelet concentrates, fresh frozen plasma (FFP), frozen plasma, cryoprecipitate, and cryoprecipitate-poor plasma can all be separated from fresh whole blood.

    Feline Blood Donation

    Cats can donate 40 to 50 mL (11 to 15 mL/kg) of blood every 3 weeks.3 Donors usually require sedation during blood collection. When the sedation protocol is chosen, it is important to consider that cats may have hypotension-related adverse reactions after donation.3 If hypotension occurs after donation, intravenous volume expansion may be required.3 Placing the patient in lateral recumbency and using a large-gauge butterfly catheter are optimal. Few collection systems for cats are available, so 25- to 60-mL syringes are used.2 Acid citrate dextrose (also called anticoagulant dextrose), citrate phosphate dextrose, or citrate phosphate dextrose adenine 1 (CPDA-1) is added to the syringe at a ratio of 1 mL per 9 mL of blood. If heparin is used, the ratio should be 5 IU per 1 mL of blood.5 The storage guidelines for these preservatives are the same as those for canine blood. Because this collection technique is considered an open system, which increases the risk of contamination, blood should be transfused within 24 hours of collection.2 Separation of components is possible but is difficult due to the limited availability of equipment for cats.

    Compatibility Testing

    Blood groups are classified by particular antigens that erythrocytes possess on their cell membranes. Dog erythrocyte antigens (DEAs) can be positive or negative for each blood type, indicating whether they are positive or negative for the antigens. DEA 1 (1.1, 1.2), DEA 1.3, and DEA 7 are the most common blood types.5 DEA 1.1–negative donors are universal for dogs that have never received a blood transfusion.

    The feline blood types are A, B, and AB (which is very rare). Type A is dominant over type B.4,6 A cat should receive only its specific blood type during transfusion. However, in the rare case that a cat has type AB blood and an AB donor is not available, type A can be transfused.4

    Blood-Typing Cards

    Commercial blood-typing cards are available for quick, easy testing of canine and feline blood. When DEA 1.1–typing cards are used, false-positive results are possible.5 In feline blood typing, there is concern that type AB blood is not always recognized.4 Typically, blood-typing cards are reserved for emergencies when time does not allow more accurate matching procedures or when canine patients have not previously received a transfusion (FIGURE 1).

    Crossmatching

    Serologic compatibility testing is recommended in cats when blood typing is not available and in cats and dogs that have previously received transfusions.4 This test does not provide blood type but does determine the compatibility of the donor and recipient. Crossmatching is typically performed by veterinary technicians. It requires technical skill but can be performed in any facility with a centrifuge (BOX 1).7 Accurately following the steps for crossmatching and carefully reviewing the information to determine whether the donor and recipient will be an appropriate match are of paramount importance.

    Blood Products

    The technician’s knowledge of commonly used components during transfusion therapy is invaluable. While veterinarians choose the appropriate component for a patient’s condition, technicians routinely process the tests that aid in this decision. There are many important steps in determining which component is indicated for each patient. Many tests (e.g., complete blood count, chemistry analysis, coagulation profile) can determine the specific component the patient is lacking. The packed cell volume (PCV) and total solids (TS) value should always be determined together. In cases of acute hemorrhage, decreases in the PCV and TS value are common. This may not be recognized until after fluid therapy has been initiated. A PCV or hemoglobin level dictating when a red blood cell (RBC) transfusion should be administered has not been specified.1 The clinical signs of anemia (e.g., pale mucous membranes, delayed capillary refill time, tachycardia, tachypnea, hypotension, weakness, collapse) should be considered in the decision.Patients with chronic anemia may be able to compensate for their condition; therefore, they may tolerate a low PCV and hemoglobin level. However, major organs can no longer compensate when the PCV is 12% and the hemoglobin level is 3 g/dL.1

    Whole Blood

    Sometimes, whole blood may be the only product available because of limited blood-bank supplies or the inability to separate whole blood in-house, which requires expensive equipment and technical skill. For dogs, a unit of whole blood contains approximately 450 mL of blood and 63 mL of anticoagulant (CPDA or CPDA-1).1,8 For cats, a unit includes 54 mL of blood and 6 mL of anticoagulant (CPDA-1 or anticoagulant dextrose).8 Whole blood contains RBCs, platelets, coagulation factors, and plasma proteins (albumin and antithrombin III).6,8 Some clotting factors (V and VIII) and platelets are inactivated during storage. Therefore, if those components are needed—such as in patients with von Willebrand disease, hemophilia A, or thrombocytopenia—fresh whole blood should be transfused within 4 to 6 hours of collection.6 In cases in which coagulation defects result in massive, acute hemorrhage, fresh whole blood is the best option.6 Fresh or stored whole blood transfused at the recommended volume of 20 mL/kg raises the PCV approximately 10%.6 Normovolemic patients are at risk for volume overload; therefore, they should not receive whole blood if other products are available.1

    Packed Red Blood Cells

    pRBCs can be separated from plasma in-house if equipment is available. Otherwise, blood banks can routinely supply pRBCs. After centrifugation and separation of whole blood, the components (pRBCs and plasma with anticoagulant) are placed in separate satellite bags. pRBC units contain only small amounts of anticoagulants and plasma. The oxygen-carrying content of 1 unit of pRBCs equals that of 1 unit of whole blood, although the total volume is only 200 to 250 mL.2,8 The PCV of a unit of pRBCs is approximately 80%.1,6 For an adequate rate of infusion, saline should be added to decrease viscosity.1,6 To accomplish this, 10 mL of 0.9% saline should be added for every 30 mL of pRBCs.6 The low colloid oncotic pressure of pRBCs makes them an optimal choice for transfusions in patients that are anemic and normovolemic.8 The initial dose recommended for transfusion is 6 to 10 mL/kg.1,2 The PCV will rise by 1% for every 1 mL/kg of pRBCs administered.6

    Plasma

    Fresh plasma is used within 6 hours of separation, which must be done within 4 hours of collection.8 Plasma that has been refrigerated at 33.8°F to 42.8°F (1°C to 6°C) for up to 35 days (using CPDA-1) is considered stored plasma (SP).9 FFP is cooled at –4°F (–20°C) within 6 hours of collection and may be stored up to 1 year.1,8,9 Frozen plasma is cooled more than 6 hours after collection and can also be stored for 1 year.8 FFP that has been stored for more than 1 year is considered frozen plasma.8

    It is important to know the differences between each plasma type because plasma is commonly used for coagulopathies. The length of storage determines which coagulation factors remain in specific types of plasma. FFP is helpful in treating coagulopathies, including disseminated intravascular coagulation, von Willebrand disease, hemophilia, and rodenticide intoxication.1 The initial recommended dosage for treating coagulopathies is 6 to 10 mL/kg q8–24h, and the dosage is determined by the condition being treated.1

    Cryoprecipitate

    Cryoprecipitate is used to treat bleeding patients with von Willebrand disease, hemophilia A, or fibrinogen deficiency resulting from rattlesnake envenomation or liver failure. von Willebrand factor, fibrinogen, fibronectin, and factor VIII are all concentrated in cryoprecipitate.4,8 If cryoprecipitate is separated from plasma, its storage and handling are similar to those for FFP stored at –4°C (–20°C) for 1 year. The recommended dose for cryoprecipitate is 1 unit per 10 kg.1,2,8

    Hemoglobin-Based Oxygen Carriers

    Hemoglobin-based oxygen carriers (HBOCs) contain purified bovine hemoglobin (13 g/dL) in a modified lactated Ringer’s solution, have a pH of 7.8, and have an osmolality of 300 mOsm/kg.1,10 HBOCs serve only one function of blood—to carry oxygen. HBOCs do not contain RBCs or other antigenic components. HBOCs efficiently release oxygen at the tissue level because their decreased viscosity allows increased microvascular flow.6 HBOCs have many advantages over RBCs, including a longer shelf life, no need for compatibility testing, and a lower risk of causing reactions or transmitting infectious diseases. The disadvantages of HBOCs include high cost, interference with biochemical analyzers, and inconsistent availability. In addition, HBOCs can lead to volume overload because of their high colloid oncotic pressure (37 torr).9 HBOCs used in patients with hypotensive, hypovolemic, and traumatic shock have been shown to reduce fluid requirements, normalize blood pressure, attenuate vascular endothelial dysfunction, improve oxygenation transport and delivery, and prolong survival.11 The dosage for Oxyglobina (OPK Biotech, Cambridge, MA) is 10 to 30 mL/kg in dogs and 3 to 5 mL/kg in cats.8,10 Because of the risk for volume overload when HBOCs are used, patients should be monitored very closely. HBOCs are also a good source of hemoglobin for patients with immune-mediated hemolytic anemia because these patients typically have hemolytic reactions to RBC products.

    Albumin

    Many critically ill patients develop hypoalbuminemia. The important roles of albumin in homeostasis include maintaining plasma oncotic properties, being a carrier protein for many drugs, controlling vascular permeability, and maintaining metabolic and acid–base functions. Albumin provides 75% to 80% of plasma oncotic pressure.2,10 In ill patients, the plasma albumin level may decrease because of an associated catabolic state. When hydrostatic pressure is raised in patients predisposed to vasculitis, the potential for vasculitis is enhanced.10 Edema of multiple organs, including the pulmonary parenchyma, is a consequence of capillary leakage and can result in respiratory distress and death.10 No canine or feline concentrated albumin solutions are commercially available. Therefore, human serum albumin has recently been used.12 Albumin may also have benefits in managing patients with specific diseases, such as systemic inflammatory response syndrome and vasculitis. FFP can raise the serum albumin level, but an extremely large volume is necessary to do so; therefore, concentrated human albumin is a better option. The recommended dose of albumin is 2 mL/kg.12

    Administration of Blood Products

    During administration of blood products, the technician’s role is extremely important because it typically involves most of the patient monitoring. This increases the technician’s responsibility to understand the potential adverse reactions and know what clinical and physiologic signs to look for during administration of blood products. Technicians must also know how to properly prepare and handle blood components for administration. When products that have been frozen or refrigerated are used, care must be taken during thawing or warming. If plasma is being given and has been frozen, technicians should ensure that the packaging is intact (i.e., without cracks or holes). Excessive heating of blood products can have negative effects, such as precipitation and denaturation of proteins, destruction of clotting factors, and reduction of the oxygen-carrying capacity of RBCs.6 Technicians should also double-check that the correct product is being given to the patient.

    All blood products must be administered through a blood administration set with a 170-µm filter.4,8 These filters remove debris and clots that may form during storage. It is extremely important to carefully examine blood products to ensure that their color and consistency are normal. Blood products can be administered by transfusion via fluid pump or gravity drip. Transfusions are typically given intravenously but can be given intraosseously if necessary.

    Patient Monitoring

    During the administration of any blood product, close patient monitoring is necessary. At a minimum, the baseline blood work should include the PCV and TS value. If Oxyglobin is being administered, the hemoglobin level should be obtained. Body temperature, heart rate, respiratory rate, and mucous membrane color should all be recorded. If volume overloading is possible, central venous pressure monitoring is needed. The total volume to be administered depends on the patient’s weight and the depletion of the component being administered. The initial rate of administration should be one-fourth of the total rate, with monitoring every 15 minutes. If no reaction is seen, the rate should be increased to one-half. The rate can be increased until the desired rate is reached, with monitoring every 15 minutes for the first hour. For example, if the desired rate is 40 mL/h, the transfusion should begin at a rate of 10 mL/h. If there are no changes in the parameters within 15 minutes, the rate could be increased to 20 mL/h. Once the desired rate is set and no reactions are seen, monitoring can be performed hourly.6,8 If any reactions (e.g., vomiting, diarrhea, urticaria, tachycardia, respiratory distress, hypotension, alterations in mentation) are seen, the transfusion should be discontinued and the patient further evaluated.

    Transfusion Reactions

    Transfusion reactions are categorized as immunologic and nonimmunologic, both of which can be further divided into acute or delayed reactions. Acute reactions are seen within hours, whereas delayed reactions can occur up to 1 week or longer after a transfusion6 (BOX 2).

    Immunologic Reactions

    Acute immunologic reactions are the most common adverse effect of transfusions.6 These reactions include anaphylactic shock, acute hemolysis, and acute hypersensitivity, possibly resulting in death. These reactions are associated with antibodies directed at RBC antigens; therefore, they can usually be avoided by appropriate blood typing and/or crossmatching of blood products before administration.5,8 Dogs have a low prevalence of naturally occurring antierythrocytic antibodies; therefore, acute hemolytic reactions are rare.5 Signs of acute hemolysis include tachypnea, fever, hemoglobinemia, hemoglobinuria, collapse, and shock.13 Patients that have had a previous transfusion generally have an increased risk for reactions.5 Clinical signs of anaphylactic shock include collapse and respiratory arrest and/or cardiac arrest.13 The clinical signs of a hypersensitivity reaction include tachypnea, fever, cardiac arrhythmias, vomiting, urticaria, pruritus, and erythema.13

    Delayed immunologic reactions can be seen approximately 1 week or longer after transfusion. These reactions include a shortened RBC life span, thrombocytopenia, and immunosuppression.8

    Nonimmunologic Reactions

    Nonimmunologic reactions are typically due to inadequate donor screening or inappropriate collection, storage, and/or administration of blood products. Reactions include sepsis from blood contamination, acquisition of infectious disease, dilution coagulopathies, hypocalcemia (citrate toxicosis), embolic disease, circulatory overload, and hyperammonemia.8 To detect any of these reactions early, diligent monitoring is essential. Signs of citrate toxicosis include signs consistent with hypocalcemia (e.g., tremors, fever, cardiac arrhythmias, vomiting, seizures) and hypomagnesemia (e.g., cardiac arrhythmias, muscle weakness).13 Signs of circulatory overload include tachypnea, an increase in central venous pressure, and pulmonary edema.13 If a large volume is being transfused, close monitoring of the coagulation status and calcium level can help prevent problems.

    Suggested Treatments for Reactions

    The various transfusion reactions can produce many of the same clinical signs. Therefore, it may be necessary to identify a specific reaction with diagnostics such as electrocardiography, blood work, blood cytology, central venous pressure measurement, or radiography. In general, administration of the blood product should cease as soon as a transfusion reaction is detected. Anaphylactic shock should be treated with epinephrine and corticosteroids, and cardiopulmonary resuscitation should be performed if necessary.13 Treating a hypersensitivity reaction includes administering corticosteroids and/or antihistamines and then restarting the transfusion at a slower rate.13 An acute hemolytic reaction should be treated with corticosteroids and IV fluids, with or without vasopressor support to maintain blood pressure.13 For citrate overdose reactions, 10% calcium gluconate should be administered slowly IV while the patient is monitored by electrocardiography; magnesium sulfate should also be added to the fluids.13 Circulatory overload should be treated with diuretics, with or without vasodilators; the transfusion can be restarted at a lower rate, although switching to a different product (i.e., pRBCs instead of whole blood) may be more appropriate.13

    Conclusion

    Component therapy is currently recommended when administering transfusions because it allows replenishment of only what the patient lacks, thereby minimizing adverse effects. This therapy also allows multiple patients to be treated with a single donation. Proper collection, storage, and administration of blood products are necessary to decrease the chance of adverse effects.

    The role of the veterinary technician is very important in component therapy. Technicians have the significant responsibilities of collecting, preparing, and administering blood components as well as monitoring patients. Therefore, advanced knowledge and understanding of all aspects of component therapy are necessary to ensure the highest quality of patient care. Having a good understanding of possible transfusion reactions and knowing how to treat them decrease the chance of extreme adverse reactions.

    Downloadable PDF

    1. Hohenhaus AE. Blood transfusions, component therapy, and oxygen-carrying solutions. In: Ettinger SJ, Feldman EC, eds. Textbook of Veterinary Internal Medicine. 6th ed. St. Louis: Elsevier Saunders; 2005:464-468.

    2. Hohenhaus AE. Blood transfusions and blood substitutes. In: DiBartola SP, ed. Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice. 3rd ed. St. Louis: Elsevier Saunders; 2006:567-583.

    3. Beal MW. Practical transfusion medicine. Proc West Vet Conf 2004:1-6.

    4. Giger U. Transfusion medicine. In: Silverstein DC, Hopper K, eds. Small Animal Critical Care Medicine. St. Louis: Elsevier Saunders; 2009:281-286.

    5. Lanevschi A, Wardrop KJ. Principles of transfusion medicine in small animals. Canine Vet J 2001;42:447-454.

    6. Chiaramote D. Blood-component therapy: selection, administration, and monitoring. Clin Tech Small Anim Pract 2004;19:63-67.

    7. Wardrop KJ. Blood typing and crossmatching. In: Feldman BF, Zinkl JG, Jain NC, eds. Schlam’s Veterinary Hematology. Philadelphia: Lippincott Williams and Wilkins; 2000:795-798.

    8. Shaw SP. Transfusion medicine for the general practitioner. Proc West Vet Conf 2008:1-7.

    9. Callan MB, Rentko VT. Clinical applications of hemoglobin-based oxygen-carrying solutions. Vet Clin North Am Small Anim Pract 2003;42:1277-1293.

    10. Mathews KA, Barry M. The use of 25% human serum albumin: outcome and efficacy in raising serum albumin and systemic blood pressure in critically ill dogs and cats. J Vet Emerg Crit Care 2005;15:110-118.

    11. Muir WW, Wellman ML. Hemoglobin solutions and tissue oxygenation. J Vet Intern Med 2003;17:127-135.

    12. Powell LL. Use of albumin in dogs with septic peritonitis. Proc IVECCS 2008:1-4.

    13. Green MT. Transfusion medicine. In: Wingfield WE, Raffe MR, eds. The Veterinary ICU Book. Jackson Hole, WY: Teton New Media; 2002:189-201.

    aOxyglobin is currently unavailable. For more information, visit www.oxyglobin.com or call 866-933-2472.

    References »

    NEXT: Case Report: Hypercoagulability and Adrenal Dysfunction in Critical Care

    CETEST This course is approved for 1.0 CE credits

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