Basics of Canine Blood Transfusion: A Review
Dr. Pankaj Hase
Assistant Professor
Mumbai Veterinary College, Mumbai
Blood transfusion has been employed for centuries to save the lives of both humans and animals. Recent breakthroughs in veterinary medicine have significantly improved blood transfusion techniques. Despite the improved information and accessibility of blood and its products, transfusion therapy has gotten more intricate. The implementation of advanced screening facilities, blood group testing, and procedures for cross-matching blood has significantly increased the complexity of the donor selection process. The development of blood component separation techniques has allowed clinicians to utilize specific components of blood based on the patient’s needs.
Blood Grouping:
Blood groups are designated based on the species-specific antigens found on the surface of red blood cells. These antigens have a significant impact on triggering immune-mediated responses and can lead to difficulties when transfusing blood between different blood groups. Transfusion therapies can trigger immune-mediated reactions in host animals when antigens are combined with platelets, leukocytes, and plasma proteins. Plasma contains endogenous antibodies that can spontaneously target antigens of different blood groups, even without prior contact to erythrocyte antigens. Red blood cell antigens exposure to blood transfusion, transplacental exposure, or colostrum might stimulate the development of antibodies in animals, including in cases of neonatal isoerythrolysis (NI). This article provides a description of blood types in various common domestic and companion animal species. These antigens are the ones that the veterinary practitioner should be most familiar with, according to a clinician’s perspective. Nevertheless, numerous additional blood group components and systems have been documented, and the absence of readily accessible typing sera does not decrease the potential importance of these alternative systems in the field of transfusion medicine.
The standardization involved defining the blood groups using isoimmune sera and establishing a standardized nomenclature for the canine blood group system.4.5 The initial workshop established the term “canine erythrocyte antigen” (CEA) together with a numerical identifier to denote the specific blood group antigen. The second workshop utilized the term dog erythrocyte antigen (DEA). The use of the new terminology was done to prevent any confusion with the carcinoembryonic antigen (CEA) system. The canine blood group system encompasses DEA 1.1, DEA 1.2, DEA 3, DEA 4, DEA 5, and DEA 7. The DEA naming system for canine blood groups is not universally recognized, however, certain authors employ the more recent genetic nomenclature system when documenting novel blood group specificities. In dogs, spontaneously occurring alloantibodies have limited clinical value, whereas in cats, they have significant therapeutic importance. The blood types DEA 1.1 and 1.2 are of utmost significance and are present in 60% of the canine population. These blood groups have the potential to cause severe transfusion reactions in dogs that have been sensitized before. The occurrence of DEA 1.3 has been reported in Australian German shepherd dogs. The DEA 4 blood group in dogs is commonly found at a high frequency and can lead to hemolytic transfusion responses. Four dogs with a history of sensitization to DEA Four instances of positive blood transfusions. Eleven Dogs that are previously sensitized to the DEA 3, 5, and 7 blood groups may experience delayed transfusion reactions if they lack these antigens.
Blood crossmatching
Agglutinating and/or hemolytic reactions between the donor and recipient are assessed using major and minor cross-matching tests. Agglutinating tests are enough for dogs and cats, but in horses, both agglutinating and hemolytic tests are necessary due to the presence of both agglutinating and hemolytic antibodies. The major crossmatch determines the presence (positive results) or absence (negative results) of measurable amounts of antibodies, whether naturally occurring or produced, in the recipient against donor erythrocyte antigens. It is essential to do a significant crossmatch in animals with potent naturally occurring antibodies, such as cats, or in those that may have developed antibodies due to previous transfusions. This remains accurate even if the identical donor blood is intended for multiple transfusions over an extended period. The minor crossmatch process is similar to the major crossmatch, but it specifically tests for the presence or absence of detectable antibodies in the plasma of the donor against the red blood cells of the receiver. The minor cross-matching procedure is not very important because the amount of donated plasma is significantly smaller than the recipient’s volume and is diluted in the recipient’s body, especially when only red blood cells are transfused.31 Transfusion of packed erythrocytes in dogs and horses may lead to unpleasant reactions due to the presence of antibodies against the recipient’s erythrocytes. For crossmatch testing, it is preferable to utilize an ethylenediaminetetraacetic acid (EDTA) tube and a clot tube obtained from the recipient. Using EDTA plasma instead of serum should be avoided as it leads to heightened rouleaux development and makes the interpretation of agglutination more challenging, especially in horses. Samples should be devoid of auto-agglutination, hemolysis, and lipemia to facilitate the interpretation of the results. If autoagglutination is detected or if suitable units are not available, it may be necessary to transfuse the least compatible unit, however, this carries a substantial risk. Transfusing even a small amount of blood that does not match is a dangerous technique and is never advised.
Crossmatching method
Obtain blood samples from both the donor and recipient using purple top and red top tubes, namely an EDTA tube and non-EDTA tubes, respectively. Utilize a centrifuge to separate the plasma and serum from the red blood cells. Extract the serum and transfer it to a distinct sterile tube. Dispose of the plasma contained in the EDTA tube. Perform a thorough cleansing of the red blood cells obtained from the EDTA tube. Transfer the red blood cells into a separate tube containing a solution of normal saline and subject them to centrifugation for 1 minute. Perform the procedure five times, discarding the liquid portion each time. To create a solution with a concentration between 2% and 4%, resuspend the cells. For example, combining 0.2mL of blood with 4.8mL of saline will yield a 4% solution. Assign the tubes with appropriate labels for the creation of the following mixtures: Major crossmatch (combining 2 drops of patient serum with 1 drop of donor RBC suspension), Minor crossmatch (combining 1 drop of patient RBC suspension with 2 drops of donor serum), and Control (combining 1 drop of patient RBC suspension with 1 drop of patient serum). Subject the mixtures to incubation at a temperature of 37°C for a duration of 15 to 30 minutes, followed by centrifugation for 15 seconds. If there is visible macroscopic evidence of either hemolysis or hemagglutination or if microscopic evidence of agglutination is observed, it indicates that the donor is not a suitable match.
Basic principles and criteria for Blood Transfusion:
To prevent transfusion responses, it is essential to do blood grouping and cross-matching between the donor and receiver before carrying out a blood transfusion. Aside from the possible negative response from a blood transfusion with incompatible blood types, the reduced lifespan of the transfused cells can lead to ineffectual treatment. It is important to thoroughly examine the species for compatibility and perform cross-matching to prevent initial sensitization and reduce the likelihood of future progeny suffering haemolytic illness. Historically, it was advised to perform cross-matching in dogs that had previously had a pregnancy. Nevertheless, a recent study has indicated that pregnancy does not appear to make dogs more responsive to antigens found in red blood cells. Blood typing for canine DEA 1.1 and feline kinds A and B are commonly performed in veterinary medicine. Research and reference laboratories are capable of conducting other groupings and cross-matching procedures. Due to the high level of danger involved, blood transfusions should only be carried out when necessary. Clients should provide their transfusion therapy history, which requires cross matching. In veterinary medicine, both whole blood and its components are transfused based on their availability and the specific indications for transfusion. Blood transfusion is mostly used to treat severe anaemia resulting from conditions such as bleeding, destruction of red blood cells, inadequate production of red blood cells, immune-mediated destruction of red blood cells, chronic inflammatory or infectious diseases, or cancer. Animals should undergo individual clinical evaluations. An established guideline for the management of anaemia is to administer a blood transfusion when the packed cell volume (PCV) falls below 10% to 15%. Animals experiencing sudden-onset anaemia typically need a blood transfusion before their packed cell volume (PCV) drops to 15%. This is in contrast to animals with long-term anaemia. In situations of thrombocytopenia, platelet transfusion is often recommended when platelet counts reach 10,000/μL. Other indications for transfusion include low blood volume, deficiency of clotting factors either as a main or secondary condition, and low levels of proteins in the blood. It is essential to label collected blood with comprehensive facts, and maintaining accurate records is vital for all instances of blood collection and administration.
Donor selection
Performing blood typing is necessary to identify suitable candidates for long-term blood donation. Only healthy young adults who have never received a blood transfusion should donate. Furthermore, donors are required to have completed regular physical, hematological, and clinical chemistry testing. To minimize the danger of disease transmission by blood, it is important to acquire a comprehensive health history of the anticipated donor by conducting a meticulous interview with the owner. In veterinary medicine, the primary limiting factor for testing individual units is typically the expense. Hence, a meticulous interview and blood screening of the donor are employed to mitigate the potential for infectious disease transmission. The donor must have received appropriate vaccinations and must have tested negative for blood parasites and other contagious disorders.
Transfusion procedure
Strict aseptic conditions must be upheld and meticulous aseptic protocols must be adhered to during the collection of blood for transfusion. ACVIM recommends that a distinct portion of each given blood unit be preserved for subsequent testing in cases where disease transmission is suspected after transfusion. It is recommended to use nonlatex filters with pore sizes of 150-170μm to filter blood before or during its delivery. Prior to administration, it is necessary to warm the blood to a temperature of 37°C in order to prevent the occurrence of hypothermia. The temperature should not exceed 37°C, as higher temperatures result in the breakdown of red blood cells and the deactivation of clotting components. Blood is delivered intravenously using commercially accessible intravenous sets equipped with filters. When there is a need for both crystalloid fluid therapy and reconstitution of blood components like packed erythrocytes, it is recommended to use a fluid that contains 0.9% saline. Lactated Ringer’s solution induces calcium chelation when used with anticoagulants containing citrate, leading to the production of blood clots. 5% dextrose in water causes the swelling and breakdown of red blood cells, whereas hypotonic saline fluids also promote the breakdown of red blood cells. Therefore, these fluids should not be used.
Circulatory overload and heart failure can occur due to the excessive and fast infusion of blood or plasma. In general, blood should be administered intravenously at a maximum rate of 10 millilitres per kilogramme per hour. It is important to start the transfusion cautiously and then gradually raise the flow rate. However, the infusion rate should be determined on an individual basis for each patient. As an illustration, individuals with hypovolemia may necessitate an infusion rate of 20 millilitres per kilogramme per hour, whereas individuals with cardiac, renal, or hepatic conditions or immobile calves may only require an infusion rate of 1 millilitre per kilogramme per hour. Rapid transfusion of blood may lead to symptoms such as excessive salivation, vomiting, and muscle fasciculations. To prevent contamination, it is necessary to transfuse warm blood within a maximum of 4 hours. The amount of blood to be transfused is calculated based on the recipient’s body weight, estimated blood volume, PCV (packed cell volume) of both the recipient and the donor, and the intended purpose of the therapy. A general rule for small animals is that administering 10-15mL/kg of packed erythrocytes or 20mL/kg of whole blood will raise the packed cell volume (PCV) by 10% if the donor has a PCV of around 40%.13.55 A study conducted on horses found that administering 15mL/kg of whole blood plus 8-10mL/kg of packed erythrocytes resulted in a 4% increase in packed cell volume (PCV) when the initial PCV of the donor was between 35-40%.
Preparatory measures prior to transfusion: Transfusion of fresh whole blood is recommended for treating acute haemorrhage, anaemia, coagulation problems, and thrombocytopenia. Whole blood that has been stored is suitable for transfusion in cases of anemia, although it does not include platelets or coagulation factors. Administering concentrated red blood cells is advised for animals with anaemia, especially those with a heightened susceptibility to excessive fluid accumulation. Fresh-frozen or stored-frozen plasma is utilized to treat individuals with congenital or acquired deficits of coagulation factors and hypoproteinaemia. Fresh-frozen plasma is recommended for treating hypogammaglobulinemia, which is a condition of inadequate transfer of antibodies, in calves, foals, puppies, and kittens. Platelet-rich plasma is recommended for the treatment of severe thrombocytopenia or thrombocytopenia. Hyperimmune equine plasma, or equine plasma with a high concentration of anti-endotoxin antibodies, has been administered to severely ill foals in the process of recovering from septicaemia. Hyperimmune serum products can be utilized in cattle afflicted with infectious diseases.57 Various blood substitutes have been utilised to treat anaemia in a range of animal species, such as dogs, cats, horses, birds, and ferrets. Some benefits of blood replacements include the absence of the need for blood typing and cross-matching, reduced danger of transmitting infectious diseases, and an extended shelf life. Nevertheless, the product carries a high price tag and must be disposed of if not utilised within a 24-hour timeframe. The half-life of the substance ranges from 18 to 40 hours, depending on the initial dose given. It is important to recognise the possibility of misuse of artificial oxygen-carriers in athletic dogs and horses.59 Finally, these products can disrupt patient monitoring through the use of colorimetric laboratory testing. Monitoring the impact of blood replacements on recipients should be done by assessing haemoglobin concentration, rather than PCV.
Adverse responses and subsequent consequences of blood transfusions:
Transfusion responses have the potential to occur either immediately or after a certain period of time. Acute intravascular hemolysis resulting in hemoglobinemia and hemoglobinuria can occur due to incompatible transfusions. The release of thromboplastic substances can result in diffuse intravascular coagulopathy. Mismatched transfusion can result in the release of vasoactive amines, which can lead to hypotension, shock, severe renal failure, and death. Delayed hemolysis is characterized by a reduction in packed cell volume (PCV) occurring within a time frame of 2 to 14 days following a blood transfusion. This condition is most frequently observed in animals that have undergone previous blood transfusions and have an antibody titer that is too low to be detected using cross-matching. Extravascular hemolysis typically leads to increased levels of bilirubin in the blood (hyperbilirubinemia) and the presence of bilirubin in the urine (bilirubinuria). The initial transfusion is typically safe for recipients who have not received a transfusion before, regardless of the blood group of the donor. This is because there are no alloantibodies against the common canine erythrocyte antigens 1.1 and 1.2, and sensitization does not happen during pregnancy in dogs. Administering an incompatible initial transfusion can sensitize the recipient to immunogenic antigens, such as 1.1, 1.2, 7, and others. This can lead to a reduced lifespan of the transfused cells during the first transfusion and increase the likelihood of experiencing a severe transfusion reaction in the future. DEA 1.1, the most potent antigen in dogs, triggers the most intense transfusion response.
A hemolytic reaction may occur when a second transfusion is given within four days after the first transfusion, in cases where there is a mismatch in the J-antigen. Neonatal isoerythrolysis refers to the destruction of red blood cells in newborns caused by antibodies from the mother that are received by colostrum.
Transfusion reactions typically manifest within 24-36 hours after birth in foals, presenting as conditions such as anaemia, liver failure, and kernicterus (bilirubin encephalopathy), which are the main factors leading to foal mortality. Additional complications, apart from erythrocyte antigen-antibody interactions, encompass fever, allergic reactions, circulatory overload, citrate toxicosis, ammonia toxicosis, and infection. Pyrexia is a prevalent clinical symptom of blood transfusion response. It might happen as a result of leukocyte or platelet antigens or due to sepsis caused by bacterial contamination of the blood. Allergic responses following transfusions in dogs, cattle, and horses are typically caused by a sensitivity to plasma proteins or leukocyte and platelet antigens. Circulatory overload may occur as a consequence when whole blood is administered to patients with reduced cardiac function.
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