INDICATIONS FOR BLOOD PRODUCT TRANSFUSIONS

Transcription

1 INDICATIONS FOR BLOOD PRODUCT TRANSFUSIONS Sarah Perry, LVT, BS, VTS (ECC) Licensed Veterinary Technician Animal Neurology, Rehabilitation and Emergency Center 1120 Welch Rd. Commerce, MI A very common call received in the veterinary emergency room is for lethargy and increased respiratory rate and/or heart rate. This call usually prompts veterinarians and technicians to have concern for bleeding. There are many reasons that a patient may present for anemia or active bleeding. Treatment is through the administration of an appropriate blood product such as packed red blood cells, whole blood, plasma or other types of platelet concentrates. It is very important that staff be fully trained in how to recognize the need for blood products and what tests are necessary to determine what product is appropriate. Initial exam findings consistent with anemia and/or thrombocytopenia indicate the need for blood product administration. Signs associated with anemia are pale mucous membranes, tachycardia, tachypnea, lethargy, weak pulses pica (mostly cats) and signs of active bleeding such as hematuria, hematochezia, hematemesis, melena. Exam findings consistent with thrombocytopenia include signs of anemia (if actively bleeding) plus possibly petechia and/or ecchymoses. The administration of blood products does not come without risk. Therefore, strict guidelines should be developed for determining which patients are in need of blood products. It is now important to determine which patients absolutely need to have a blood product transfusion. Considerations for transfusion need include patients with acute blood loss, versus those with chronic anemia whose bodies have adapted to the decrease in red blood cells over time. Animals can compensate for chronic anemia through increasing cardiac output, redistributing blood flow and having a decrease in the hemoglobin need for oxygen. Patients with acute blood loss may be in need of a transfusion at a higher red blood cell count (or PCV) than those that have become accustomed to it. Patients in which anemia should be addressed include those with cardiac, renal or respiratory disease. Also those that may benefit from a transfusion more may include geriatrics, patients with cerebrovascular disease and critically ill patients. Once it is decided that a patient may be in need of a blood product it is important to determine which product is appropriate. For patients that have had massive hemorrhage a whole blood transfusion is appropriate because of not only the need for circulating red blood cells but also volume. For patients that are anemic from red blood cell destruction (IMHA) packed red blood cells are appropriate. There is not necessarily a set number that a PCV should be in order to transfuse a patient with red blood cells. The patient should be clinical. This means that when the patient is lethargic, weak and the PCV has fallen below 20% in dogs and 15% in cats a red blood cell transfusion may be indicated. Tachycardia and tachypnea are clinical findings that indicate that a transfusion is needed. The volume status of a patient should be taken into consideration. If a

2 patient is hypovolemic they are in need of volume. They should initially be fluid resuscitated and then can be given a red blood cell product when the PCV reaches 25-30%. Normovolemic patients (those that have compensated due to chronic anemia) are usually not clinical for the decreased red blood cell count and may not need to be transfused until the PCV reaches 12-18%. Cats overall are more tolerant of anemia. They may not show clinical signs until their PCV reaches 10-15%. Some patients with active hemorrhage may be due to an underlying coagulopathy. Plasma transfusions are primarily administered to patients with coagulopathies. These bleeding disorders may be genetic in origin (vonwillebrand s), from a toxin (rodenticide) or from severe inflammation or sepsis. Clotting factors that are present in plasma are also lost through massive hemorrhage. Plasma also contains albumin. In patients that have protein-losing enteropathy and are hypoalbuminemic a plasma transfusion may be needed to treat ascites. Albumin maintains intravascular volume. However, very large amounts of plasma are needed to increase levels of serum albumin small amounts. For this reason, synthetic colloids may be a better choice. Hetastarch and Dextran are synthetic colloids commonly used for volume expanders and colloidal support. Fresh Frozen Plasma (FFP) consists of albumin, coagulation factors and immunoglobulins. Plasma is considered FFP for up to one year. Frozen plasma contains factors II, VII, IX, X, albumin and immunoglobulins. It is can be frozen and viable up to 4 years. Cryoprecipitate is also available. It contains 50% of factor VIII (Von Willebrand s factor), 20-40% fibrinogen and some factor XIII. The remainder of the plasma left from removing the cryoprecipitate includes the remaining factors, as well as albumin and immunoglobulins. Platelet transfusions are possible but not always available in veterinary medicine due to expense and storage concerns. It is difficult to get a large enough volume of platelets that will improve hemorrhaging. Functional platelets are not available in stored whole blood, packed red blood cells or frozen plasma. Products that are available are platelet rich plasma or frozen platelet concentrate. The latter is very expensive but platelet function is maintained for up to 6 months. One unit of platelet concentrate raises the platelet count by about 20,000 u/l. One unit of platelet rich plasma can raise the platelet count in a patient approximately 10,000 u/l. When should a platelet transfusion be considered? They are usually only administered to patients with severe, life threatening thrombocytopenia or when active hemorrhage is present with platelet dysfunction. Platelet transfusions may not be as effective in larger dogs because of the large volume that is needed to maintain adequate hemorrhage control. Before administering blood products it is important to determine what blood type the patient is. Canines have dog erythrocyte antigens (DEA). These are glycoproteins or glycolipids that are on the surface of red blood cells. The presence or lack of these antigens is what determines a blood type (DEA positive or negative). There are thirteen blood groups recognized but there may be more antigen types not recognized yet. Of the thirteen that have been recognized, eight are considered international standards. They are DEA 1.1, 1.2, 3, 4, 5, 6, 7, 8. There are naturally occurring antibodies against DEA 3, 4, 5 and 7. Reactions occur when dogs that have blood negative for DEA 3, 4, 5 or 7 are transfused with blood from a donor that is positive for DEA 3, 4, 5 or 7. Loss of the transfused red blood cells happens in three to five days. The blood group that veterinarians are most concerned about is DEA 1.1. Canines do not have naturally occurring antibodies of DEA 1. This means that if a dog that is negative is given

3 positive blood it will not have an immediate reaction. However, antibodies can then be produced and subsequent positive transfusions may result in a reaction. Severe hemolytic transfusion reactions can occur with DEA 1.1 or 1.2 antigen-antibody reactions. Universal donors are negative for DEA 1.1, 1.2, 3, 5, 7 and positive for DEA 4. In the past, donors were universal if they were negative for DEA 1.1 and 1.2 only. If a patient requires multiple transfusions throughout its lifetime there is a higher the risk for transfusion reactions. Therefore, it is imperative that veterinary staff perform blood typing and crossmatch on all transfusion patients. Felines have three recognized blood groups. The groups are A, B and AB. Cats are different from dogs in that they do have naturally occurring antibodies against blood types. These antibodies are present at birth. Type A cats typically have a low level of anti-b antibodies. If a type A cat is transfused with Type B blood the red cells are typically destroyed in about 2-4 days. However, Type B cats have a high level of anti-a antibodies. Therefore if a type B cat is transfused with Type A blood a very acute hemolytic reaction can occur and could cause death. The last feline blood type is AB which is extremely rare. There is not a universal donor type for cats. Type B blood is more predominant in purebred felines. Breeds recognized as having more Type B cats are the Abyssinian, Devon Rex, Cornish Rex, British Shorthair, Birman, Himalayan and Scottish Fold. Also it has been noted that domestic shorthair felines in the Pacific Northwest have a higher tendency to have Type B blood than domestic shorthair cats from the East Coast. If a patient is receiving its very first transfusion it is not necessary to perform a crossmatch. It is very important to perform a crossmatch if a transfusion is being administered to a patient that has previously been transfused within 3 or 4 days. What is a crossmatch used to determine? A crossmatch determines if the patient has antibodies in its plasma against antigen on red blood cells from the donor. If the complete history of the pet is unknown (rescued at an older age) it is also important to crossmatch incase the pet received a transfusion before it came to live with its family. Even though veterinary staff does their best to avoid transfusion reactions, cross-matching does not guarantee that an adverse reaction may occur. Crossmatching does not detect antibodies against white blood cells and platelets. It also cannot predict acute hypersensitivity reactions. There are studies being performed showing that potentially the storage of red blood cells may have something to do with the development of transfusion reactions. There are now reliable crossmatching kits for purchase. Blood cross-match can be done without a commercial kit. The cross-matching procedure is as follows (from Animal Blood Resources): Procedure for major and minor crossmatch: 1). Collect blood into an EDTA tube from recipient and possible donor or take one segment from the donor blood bag and place blood in tube without anticoagulant. 2). Centrifuge tubes at 1000 x 9 for 5 min. to separate plasma from red blood cells. 3). Remove plasma from each sample with a clean pipette and transfer to clean, labeled glass or plastic tubes. 4). Wash RBCs 3 times with a normal saline solution; re-suspend to make a 3-5% RBC suspension (1 drop RBC: 20 drops saline). 5). Prepare for each donor 3 tubes labeled with Major, Minor, and Recipient control. Add to each tube 2 parts of plasma and 1 part of RBC suspension as follows: Major blood cross match: recipient plasma + donor cells

4 Minor blood cross match: donor plasma1 + recipient cells Recipient control: recipient plasma + recipient cells 6). Mix gently and incubate for 15 min. at room temperature. 7). Centrifuge for 15 sec. at 1000 x 9. 8). Examine the supernatant for hemolysis. 9). Gently re-suspend button of cells by tapping tube with a finger and examine for macroscopic agglutination. 10). If macroscopic agglutination is not observed, transfer a small amount onto a slide and examine for microscopic agglutination. Do not confuse agglutination with rouleaux which is not an indicator for agglutination. Interpretation: A control with recipient red cells and plasma is included because some recipients have immune mediated hemolysis with auto-agglutination. This can interfere with interpretation of the crossmatch. Any hemolysis and/or agglutination in the major or minor blood cross match but not in the control indicate an incompatibility and the need to choose a new donor. If the control is weakly positive and test sample is strong, results may be valid; if both are equal, no conclusions as to compatibility can be drawn. A compatible blood cross match does not prevent sensitization or delayed transfusion reactions. It only informs staff that at the present time there are no significant antibodies against the red cells. Another consideration, especially in patients with immune-mediated hemolytic anemia is the interference of auto-agglutination with blood typing and cross-matching. Most blood typing kits are able to interpret a blood type without the interference of auto-agglutination. A slide agglutination test can easily be performed to determine if a patient is auto-agglutinating. Auto-agglutination test: 1) Obtain a clean slide and place one drop of 0.9% saline on it 2) Place one drop (equal size) of non-coagulated blood (fresh out of patient or from an EDTA tube) 3) Use a trans-axial motion to rotate the slide and mix the two drops gently 4) Look for signs of red blood cell clumping (grossly) 5) Cover with a cover slip and look at the sample microscopically 6) Look for clumps of red blood cells, as this is agglutination 7) Distinguish from rouleaux,which looks like stacked coins, rather than clumps Canine patients that are auto-agglutinating should receive a negative or universal donor unit of blood as they will not be able to be cross-matched or typed. Cats should never be given blood without a blood type. All felines need to be blood typed and cross-matched. They should only be administered type specific transfusions. There is no universal donor for felines.

5 Blood Product Components Viability Indications for use Mode of Action Whole Blood - fresh RBC, Platelets Albumin, coag factors 6 hours or less -Anemia with lg. volume depletion (acute hemorrhage) -Anemia with concurrent thrombocytopenia/pathia or coag factor deficiency -Improve O2 carrying -Blood volume replacement -Coagulation factor replacement Whole Bloodstored RBC Albumin 21 days -Anemia with volume depletion (hemorrhage- acute or chronic) -Improve O2 carrying -Blood volume replacement Packed Red Blood Cells (PRBC) Red blood cells 35 days -Anemia Can be for pre-surgical correction, non-regenerative anemia, hemorrhage or IMHA -Improve O2 carrying Fresh Frozen Plasma All coag factors Albumin 1 year -Replacement of coagulation factors (anticoagulant rodenticide toxicity, DIC, VonWillebrand s Disease, factor deficiencies (congenital) -Hypoproteinemia -Control blood loss due to clotting factor deficiencies -Improve oncotic pressure Frozen Plasma Non-labile Coag factors 4 years -Replacement of non-labile coagulation factors (Anticoagulant rodenticide toxicity, hemophilia B) -Hypoproteinemia -Control of blood loss due to non-labile clotting factor deficiencies -Improve oncotic pressure Frozen Platelet Concentrate Plasma Platelets 6 months -Active bleeding from thrombocytopenia/pathy -Provides functional platelets

6 Cryoprecipitate Factors VIII and XIII, VonWillebrand factor, Fibronectin and Fibrinogen 1 year -vonwillebrand Disease -Hemophillia A -Manage hemorrhage and pre-surgical use for patients with vonwillebrand Disease and Hemophillia A