- \n
- Destruction of RBCs, such as in immune-mediated hemolytic anemia<\/a><\/strong>, bloodborne parasite infection, neoplasia, and toxicoses.<\/span><\/li>\n
- Increased loss of blood from hemorrhage, such as in trauma, neoplasia, bleeding disorders, and internal\/external parasitism.<\/span><\/li>\n
- Decrease in RBC production, such as in iron deficiency, drug toxicosis, neoplasia, and renal failure.\u00a0<\/span><\/span><\/li>\n<\/ul>\n
Anemia can be categorized as regenerative or nonregenerative. In regenerative anemia, there is evidence of active erythropoiesis such as increased numbers of reticulocytes, nucleated RBCs, and polychromasia. Regenerative responses indicate that anemia is due to loss or destruction of RBCs. Nonregenerative anemia is the result of inadequate erythropoiesis. Although decreased bone marrow production is the most common cause of nonregenerative anemia, blood loss and RBC destruction cannot be ruled out. Since bone marrow takes 3 to 5 days to respond to anemia, acute hemorrhage or hemolysis may appear nonregenerative. Clinical signs of anemia are listed in <\/span>BOX 1<\/span><\/strong>.<\/span><\/p>\n
BOX 1 Clinical Signs of Anemia<\/div><\/span><\/p>\n- \n
- Tachycardia <\/span><\/li>\n
- Lethargy <\/span><\/li>\n
- Pale mucous membranes <\/span><\/li>\n
- Tachypnea <\/span><\/li>\n
- Hypothermia <\/span><\/li>\n
- Hypotension<\/span><\/li>\n<\/ul>\n
<\/div><\/div><\/span><\/p>\n
Role of Blood Transfusion in Management of Anemia<\/h2>\n
RBC-containing transfusion products are used to replace or restore oxygen-carrying capacity in patients with anemia when fluids alone are not sufficient to correct tissue hypoxia.\u00a0<\/span><\/span><\/p>\n
A specific PCV at which RBC transfusion is necessary has not been identified. The entire clinical picture of the patient must be considered. Ideally, the approach to treatment should be individualized for each patient and be guided by its clinical signs and hematologic values. The goal of an RBC transfusion is to restore oxygen delivery to the tissues, and normalizing the PCV is typically not necessary to achieve this goal; therefore, the transfusion plan should be tailored to the patient\u2019s needs and not to a specific PCV. The following clinical signs may indicate the need for an RBC transfusion.<\/span><\/p>\n
- \n
- Tachycardia<\/span><\/li>\n
- Tachypnea<\/span><\/li>\n
- Prolonged capillary refill time\u00a0<\/span><\/span><\/li>\n
- Hypotension<\/span><\/li>\n
- Mucous membrane color<\/span><\/li>\n
- Acute blood loss >30% of body weight\u00a0<\/span><\/span><\/li>\n
- PCV <20% with other clinical signs consistent with hypoxia<\/span><\/li>\n
- Hypoproteinemia<\/span><\/li>\n
- Unresponsive to crystalloid or colloid therapy\u00a0<\/span><\/span><\/li>\n<\/ul>\n
Blood Product Selection<\/h2>\n
Component therapy is the separation of whole blood into individual fractions containing the transfusable components, including red cells, platelets, plasma, proteins, and cryoprecipitate. The use of component therapy is considered the most effective method of balancing clinical needs, risks of reaction, and restrictions of blood product availability. Appropriate blood products to treat anemia include fresh whole blood, stored whole blood, and packed RBCs (PBRCs).<\/span><\/p>\n
Whole Blood<\/h3>\n
Fresh whole blood contains all blood components, including RBCs, white blood cells, platelets, coagulation factors, albumin, globulins, and electrolytes. It is not processed and can be administered immediately or within 4 to 6 hours of collection at room temperature for optimal platelet activity. Transfusion of fresh whole blood is rarely indicated, as it increases the risk for transfusion reaction and is an inefficient use of limited resources.<\/span><\/p>\n
Stored whole blood can be maintained in the refrigerator for 35 days at 1 \u00b0C to 6 \u00b0C. Platelets in stored whole blood are not viable after 24 hours. Administration of stored whole blood is only indicated for RBC replacement and volume expansion.\u00a0<\/span><\/span><\/p>\n
Packed Red Blood Cells<\/h3>\n
Units of PRBCs contain RBCs, white blood cells, nonviable platelets, and a small amount of plasma. PRBCs can be stored for 35 to 42 days at 1 \u00b0C to 6 \u00b0C. During storage, PRBC units should be gently rocked daily to allow the cells access to nutrients, and they should be placed with space between them to allow appropriate oxygen exchange for RBC viability. PRBCs are used to improve oxygen-carrying capacity. When volume expansion is also necessary, the use of crystalloid fluids along with PRBCs produces results comparable to that of whole blood while decreasing the risk for transfusion reactions.\u00a0<\/span><\/span><\/p>\n
Although plasma products are not directly indicated for the treatment of anemia, products such as fresh frozen plasma, frozen plasma, cryoprecipitate, and platelet products may be necessary to control specific coagulopathies and decrease blood loss.<\/span><\/p>\n
Sources of Blood Products<\/h2>\n
Several commercial blood banks can provide blood products. A list is available on the Association of Veterinary Hematology and Transfusion Medicine website (<\/span>avhtm.org<\/span><\/a><\/strong>). Except for the California Department of Food and Agriculture, no organizations govern or regulate animal donor programs. Many blood banks voluntarily follow the 2016 American College of Veterinary Internal Medicine (ACVIM<\/a><\/strong>) consensus statement.1<\/sup><\/span><\/p>\n
Some private veterinary clinics and universities have their own canine and feline donor programs that use employee-, student-, and\/or volunteer-owned donors. Screening protocols should be evaluated before using their products. Clinics are encouraged to critically evaluate the operating procedures of their preferred blood source to ensure safe and efficacious transfusions.\u00a0<\/span><\/span><\/p>\n
Blood Typing and Crossmatching<\/h2>\n
Over the past several years, veterinary transfusion medicine has made continuous strides to ensure the safety and efficacy of transfusions. Typing and crossmatching between donors and recipients not only significantly reduces the risk of transfusion reactions but also allows for more efficient use of colony donors and available resources. Use of incompatible products is detrimental to the intended recipient and the purpose of the transfusion and reduces the lifespan of the transfused product.<\/span><\/p>\n
Dog Erythrocyte Antigens<\/h3>\n
Blood types in dogs are determined by the different proteins and complex carbohydrates located on RBC membranes, known as dog erythrocyte antigens (DEAs). Canine blood types include DEA 1, 3, 4, 5, and 7. One dog may possess multiple DEAs. DEA 1 is highly antigenic and is known to cause the more recognizable transfusion reactions. To further complicate compatibility discussions, the Dal, Kai 1, and Kai 2 antigens have also been identified. The absence of the Dal antigen is rare but is most common in Dalmatians, Doberman pinschers, and Shih Tzus.2,3<\/sup> The clinical relevance of Kai 1 and Kai 2 is uncertain at this time. In addition, 8 other antigens with variable clinical relevance have been described in dogs over the past 50 years.\u00a0<\/span><\/span><\/p>\n
Although the percentages vary geographically, approximately 63% to 67% of the canine population is positive for DEA 1. Recently, testing for DEA 4 and 5 has also become available. Ideally, DEA 1\u2013positive blood products should be administered to DEA 1\u2013positive recipients, allowing DEA 1\u2013negative blood to be administered to DEA 1\u2013negative recipients when necessary.\u00a0<\/span><\/span><\/p>\n
Feline Erythrocyte Antigens<\/h3>\n
There are 3 blood types in the feline population: A, B, and AB. Type A is the most common, type B occurs in 5% to 10% of cats, and AB is exceedingly rare in all breeds. The Mik antigen has also surfaced. Its relevance is not entirely understood at this time. The Mik antigen is present in most cats. Cats that are Mik negative are at risk for transfusion reactions.\u00a0<\/span><\/span><\/p>\n
There is no \u201cuniversal\u201d blood type in cats. Cats have naturally occurring alloantibodies to the other blood groups even without prior transfusions. Therefore, typing cats is essential, as incompatible blood types can lead to a fatal reaction, especially in type B cats receiving type A blood.4<\/sup> Two typing systems for identifying feline erythrocyte antigens (FEAs) are commercially available.\u00a0<\/span><\/span><\/p>\n
Blood Typing Tests<\/h3>\n
Both tests described in <\/span>BOX 2<\/span><\/strong> <\/b>have advantages and disadvantages. Veterinary nurses must acquaint themselves with the products and form their own preference.<\/span><\/p>\n
BOX 2 Blood Typing Tests: Step by Step<\/div>\nRapidVet-H Blood Typing Cardsa<\/sup> <\/span><\/h3>\n
Complete within 2 minutes in any clinical setting. The results of these tests are difficult to read when the patient has a low packed cell volume (PCV) and there are not enough cells to agglutinate. They may be subjective if performed by someone not comfortable with reading agglutination results. These tests have a shelf life of 24 months. <\/span><\/p>\n
Canine <\/span><\/strong><\/p>\n
- \n
- Designed to identify a single dog erythrocyte antigen (DEA) (1, 4, or 5; FIGURE A<\/strong>). <\/span><\/li>\n
- The test is set up with 3 wells: negative control, positive control, and patient. The provided buffer solution is added to each well. A positive control and a negative control are placed in their respective wells, and the recipient blood is placed into the patient well. <\/span><\/li>\n
- Any agglutination in the patient well, no matter how subtle, means that patient is positive for the tested antigen. <\/span><\/li>\n
- Always use the agglutination card that comes in the test. If agglutination is present, cell washing is necessary to continue. Continuing without cell washing will give a false-positive result.<\/span><\/li>\n<\/ul>\n
![\"\"](\"https:\/\/todaysveterinarynurse.com\/wp-content\/uploads\/sites\/3\/2021\/05\/Nusbaum_TVNSummer21_AnemicTransfusions_Box2A-232x300.jpg\")
<\/a>.<\/span><\/p><\/div>\n
Feline <\/span><\/strong><\/p>\n
- \n
- Designed to identify type A, B, or AB feline erythrocyte antigens (FEAs) (FIGURES B, C, AND D<\/strong>). <\/span><\/li>\n
- One drop of buffer and one drop of patient blood are placed into each well. <\/span><\/li>\n
- An additional drop of buffer is placed only into the type A well and observed for agglutination. This is an especially important step that is often overlooked. If this step is not completed, the results will be inaccurate.<\/span><\/li>\n<\/ul>\n
![\"\"](\"https:\/\/todaysveterinarynurse.com\/wp-content\/uploads\/sites\/3\/2021\/05\/Nusbaum_TVNSummer21_AnemicTransfusions_Box2B.jpg\")
<\/a> ![\"\"](\"https:\/\/todaysveterinarynurse.com\/wp-content\/uploads\/sites\/3\/2021\/05\/Nusbaum_TVNSummer21_AnemicTransfusions_Box2D.jpg\")
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<\/a><\/p>\n<\/h3>\n
QuickTest for Canine and Felineb<\/sup> <\/span><\/h3>\n
Complete within 2 minutes in any clinical setting. The canine test is designed to identify only the DEA 1 antigen (FIGURE E<\/strong>). The feline test is designed to identify FEAs A, B, and AB (FIGURE F<\/strong>). <\/span><\/p>\n
- \n
- For either test, add 3 drops of buffer (provided in the kit) and one single drop of blood into the provided well. <\/span><\/li>\n
- Place a membrane strip previously treated with monoclonal antibodies into the solution. <\/span><\/li>\n
- Through capillary action, solution migrates up the membrane, revealing a control line and a line that represents the presence or absence of DEA 1 (for canine) or FEA A, B, or AB (for feline). <\/span><\/li>\n
- Even the weak appearance of a line is considered a positive result. <\/span><\/li>\n
- This test is accurate even in the presence of agglutination or in samples with incredibly low PCV; however, the lower the PCV, the lighter the control appears.<\/span><\/li>\n<\/ul>\n
![\"\"](\"https:\/\/todaysveterinarynurse.com\/wp-content\/uploads\/sites\/3\/2021\/05\/Nusbaum_TVNSummer21_AnemicTransfusions_Box2E.jpg\")
<\/a> ![\"\"](\"https:\/\/todaysveterinarynurse.com\/wp-content\/uploads\/sites\/3\/2021\/05\/Nusbaum_TVNSummer21_AnemicTransfusions_Box2F.jpg\")
<\/a><\/p>\na<\/sup>DMS Laboratories, Flemington, NJ.
\nb<\/sup>Alvedia, Limonest, France.<\/em><\/p>\n<\/div><\/div>\nMajor and Minor Crossmatching\u00a0<\/span><\/h3>\n
Blood typing identifies certain known antigens in the patient and donor but does not identify antibodies in the patient or donor. The crossmatch procedure determines whether there is an antibody reaction to antigens in the donor and is performed to determine compatibility or incompatibility between donor and recipient. Screening for compatibility maximizes patient safety by reducing the risk of immune-mediated hemolytic transfusion reactions and improving survival of the RBCs. Major crossmatching detects antibodies in the recipient\u2019s serum that may agglutinate or lyse the donor\u2019s RBCs. Minor crossmatching detects antibodies in the donor\u2019s plasma directed against recipient RBCs.\u00a0<\/span><\/span><\/p>\n
Point-of-care testing can be performed manually or with affordable commercially available kits; therefore, crossmatching is considered the standard of care in transfusion medicine. It should be used in addition to blood typing, not as a substitute. Identification of the feline Mik <\/i>and <\/i>canine Dal, Kai 1, <\/i>and <\/i>Kai 2 antigens further supports the necessity of crossmatching all RBC transfusions.<\/span><\/p>\n
A 2016 study evaluated the accuracy of a gel-based commercial crossmatching kit and compared it with the standard manual method in a private veterinary referral practice. The authors concluded that the gel-based test was 3\u00d7 faster to perform; however, microagglutination and low-grade hemolysis made it difficult to interpret the test results, potentially leading to transfusion reactions.5<\/sup> Standard manual crossmatching (<\/span>BOX 3<\/span><\/strong>) remains the gold standard to determine compatibility.<\/span><\/p>\n
BOX 3 Step by Step: Manual Crossmatching<\/div><\/span><\/p>\n- \n
- Collect 0.5 to 1 mL blood in an EDTA tube and 1 to 2 mL in a clot tube from recipient and donor. Clearly label tubes. <\/span><\/li>\n
- Centrifuge tubes at standard speed for the centrifuge to separate red blood cells (RBCs) from plasma and serum. <\/span><\/li>\n
- Prepare 4% donor and recipient RBC suspensions in tubes or syringes by mixing 0.2 mL packed RBCs (PRBCs) and 4.8 mL saline. Use a separate pipette for each mixture and clearly label. <\/span>\n
- \n
- This step is optional but may retard rouleaux formation and facilitate microscopic observation. <\/span><\/li>\n<\/ol>\n<\/li>\n
- Label 4 glass slides as: <\/span>\n
- \n
- Donor control: Donor RBC\/donor RBC <\/span><\/li>\n
- Major x match: Donor RBC\/recipient serum or plasma <\/span><\/li>\n
- Minor x match: Recipient RBC\/donor serum or plasma <\/span><\/li>\n
- Recipient control: Recipient RBC\/recipient serum or plasma <\/span><\/li>\n<\/ol>\n<\/li>\n
- On each slide, place either 1 drop of serum or plasma and 1 drop of RBC suspension or 2 drops of serum and 1 drop of undiluted RBCs. Rapidly mix the drops together with an applicator stick. Use a separate stick for each slide. <\/span><\/li>\n
- Gently rock the slide and observe for macroscopic agglutination. Score the results as follows: <\/span><\/li>\n<\/ol>\n
4+ = one solid agglutinate <\/span><\/p>\n
3<\/span>+ = several large agglutinates <\/span><\/p>\n
2+ = medium-size agglutinates, clear background <\/span><\/p>\n
1+ = small agglutinates, turbid background <\/span><\/p>\n
0 = no agglutination <\/span><\/p>\n
Any agglutination (1+ or greater) or hemolysis = incompatible crossmatch <\/strong><\/span><\/p>\n
Smooth suspension = compatible crossmatch<\/strong><\/span><\/p>\n
<\/div><\/div><\/span><\/p>\n
Crossmatching is absolutely essential in patients that have been previously transfused with RBCs in the past 4 to 7 days, that have a transfusion reaction history, or for which the transfusion history is unknown. Although most dogs lack natural antibodies to DEA 1 and therefore may not react to an initial transfusion with DEA 1\u2013positive blood, such an exposure puts <\/span>them at risk for severe reactions to a second transfusion.6<\/sup> One study found that 7 out of 9 dogs receiving DEA 1\u2013positive RBCs became sensitized to other RBC antigens.7<\/sup> Another study concluded that crossmatching incompatibility can exist even between first-time transfusion recipients and potential blood donors.8<\/sup><\/span><\/p>\n
In the past, it was thought that pregnancy sensitized female animals to RBC antigens; however, this theory is no longer supported.9<\/sup><\/span><\/p>\n
Pretransfusion Preparation<\/h2>\n
Treatment with steroids or antihistamines prior to transfusion is not recommended, as it may mask transfusion reactions. Initial vital signs should be recorded and the patient fully evaluated before beginning the transfusion. The presence of vomiting, facial edema, hemolysis, or pigmenturia before transfusion should be recorded on a form such as the one shown in the sample (<\/span>BOX 4<\/span><\/strong>).<\/span><\/p>\n
- Major x match: Donor RBC\/recipient serum or plasma <\/span><\/li>\n
- Label 4 glass slides as: <\/span>\n
- Centrifuge tubes at standard speed for the centrifuge to separate red blood cells (RBCs) from plasma and serum. <\/span><\/li>\n
- Place a membrane strip previously treated with monoclonal antibodies into the solution. <\/span><\/li>\n
- One drop of buffer and one drop of patient blood are placed into each well. <\/span><\/li>\n
- The test is set up with 3 wells: negative control, positive control, and patient. The provided buffer solution is added to each well. A positive control and a negative control are placed in their respective wells, and the recipient blood is placed into the patient well. <\/span><\/li>\n
- Tachypnea<\/span><\/li>\n
- Lethargy <\/span><\/li>\n
- Increased loss of blood from hemorrhage, such as in trauma, neoplasia, bleeding disorders, and internal\/external parasitism.<\/span><\/li>\n
![\"Nusbaum_TVNSummer21_AnemicTransfusions_Box4\"](\"https:\/\/todaysveterinarynurse.com\/wp-content\/uploads\/sites\/3\/2021\/05\/Nusbaum_TVNSummer21_AnemicTransfusions_Box4.jpg\")
<\/a><\/span><\/p>\n