Blood products are administered in a dedicated IV line with an in-line blood filtration set (see blood product filter image). Only pumps approved for blood products (or gravity flow, without a pump) should be used for delivering blood transfusion.
Transfusion rate depends on patient condition, with rapid rates warranted in individuals with hemodynamic instability and slower delivery (over 4 hours) in more stable patients. Slower transfusion rates are indicated in patients with cardiac disease or renal insufficiency.
Calcium-containing fluids cannot be administered with blood products, and medications should not be administered with the blood transfusion. RBCs remain in the refrigerator until just before use, while frozen plasma products are thawed immediately before use.
Courtesy of Dr. Shauna Blois.
All blood donors and recipients should be typed for dog erythrocyte antigen (DEA) 1 (dogs) or AB (cats) before transfusion to allow transfusion of type-matched RBC products. While DEA 1-positive dogs can receive DEA 1-negative RBC products without risk of incompatibility, use of DEA 1-positive blood products in DEA 1-positive recipients allows for prudent management of blood bank resources.
Dogs with DEA 1 weak positive blood type warrant special consideration in transfusion, due to the unknown immunological risk of transfusing DEA 1 strongly positive blood to a DEA 1 weak positive dog. A DEA 1 weak positive blood donor is treated as DEA 1-positive, while a DEA 1 weak positive recipient should receive DEA 1-negative blood.
The volume of RBCs transfused can be calculated based on the desired posttransfusion PCV. Patients do not require a normal PCV to achieve hemodynamic stability.
Transfusion volume (in mL) can be calculated as follows:
Packed RBC volume to transfuse = ([desired PCV – recipient's PCV]/unit PCV) × BV × BW
where BV is the recipient's total blood volume (in mL/kg) estimated as 40–60 mL/kg in cats and 80–90 mL/kg in dogs, and BW is body weight (in kg).
For coagulopathies, the recommended dose of plasma to transfuse is 10–20 mL/kg (dogs) or 6–10 mL/kg (cats).
Plasma is not efficient for treatment of hypoproteinemia, but volume of plasma (in mL) can be calculated as the following:
Volume of plasma to transfuse = ([desired TP – recipient's TP]/unit TP) × BV × BW
where TP is total protein, BV is the recipient's total blood volume (in mL/kg) estimated as 40–60 mL/kg in cats and 80–90 mL/kg in dogs, and BW is body weight (in kg).
Canine lyophilized albumin is reconstituted to various concentrations just before use depending on need. A 5% solution is recommended for normovolemic dogs. Dosing to achieve a patient albumin level of 2–2.5 g/dL is recommended; 450 mg/kg is needed to raise serum albumin by 0.5 g/dL.
Platelet-rich plasma, platelet concentrate, and cryopreserved platelet transfusions are dosed at 1 unit per 10 kg of recipient's body weight and administered within 2 hours.
If patient condition permits, many clinics use a test dose before administering an RBC transfusion, giving a small amount of blood (eg, 0.25 mL/kg for 15 minutes) and closely monitoring for clinical signs of a transfusion reaction. If no concerns are noted, the transfusion proceeds at the indicated rate.
Risks of Blood Transfusion in Dogs and Cats
Transfusion recipients should be closely monitored throughout and after the transfusion. Vital signs should be assessed every 15 minutes during the first hour, hourly until cessation of the transfusion, then at 15 minutes, 1 hour, and 24 hours after the transfusion is finished. Patients should be assessed immediately if any clinical signs of a reaction are suspected. PCV can be assessed when RBC transfusion is completed to evaluate transfusion efficacy.
Fever
Fever is one of the most common clinical signs of a transfusion reaction. A febrile nonhemolytic transfusion reaction (FNHTR) is defined as a body temperature > 39°C (102.2°F) and an increase in temperature of > 1°C (1.8°F), during or within 4 hours of a transfusion, with no other identified causes. An FNHTR is a mild and self-limiting reaction secondary to transfusion of leukocyte and platelet antigens, as well as proinflammatory mediators, and does not require treatment. More severe transfusion reactions can also present with fever; therefore, fever should prompt complete patient assessment.
Use of leukoreduced blood products has been associated with decreased rates of FNHTR in dogs.
Hemolysis
Hemolysis can be due to nonimmunological causes (eg, damage to RBCs transfused from improper storage or administration techniques) or to immunological causes from type II hypersensitivity (antigen-antibody) reactions. The most common example of an immunological acute hemolytic transfusion reaction (AHTR) is transfusion of a blood type against which the recipient has antibodies.
Clinical signs of AHTR can range in severity from fever, tachycardia, and dyspnea to hypotension, shock, and disseminated intravascular coagulation. AHTRs are characterized by an inadequate increase in PCV after transfusion and clinical signs of hemolysis (eg, new hyperbilirubinemia or hemoglobinemia, presence of spherocytes, presence of ghost cells). Fever might be present.
In the case of an AHTR, the transfusion must be stopped and fluid resuscitation and other supportive care initiated as needed. Delayed hemolytic transfusion reactions can occur secondary to immunological incompatibilities and are often not clinically detectable other than by an accelerated decline in PCV > 24 hours after RBC transfusion.
Respiratory Distress
Respiratory distress transfusion reactions are most commonly due to transfusion-associated circulatory overload (TACO).
Clinical signs of TACO include new onset of respiratory distress (eg, tachypnea, cough) during or within 24 hours after the transfusion. Radiographic signs of enlarged pulmonary venous vasculature or pulmonary parenchymal infiltrates, cardiac ultrasonogram showing enlarged left atrial to aortic ratio, or new increases in BNP (brain natriuretic peptide) concentration support a diagnosis of TACO.
TACO is treated by stopping the transfusion, judicious use of diuretics, and supportive care.
Transfusion-related acute lung injury is not commonly reported in veterinary patients.
Acute Allergic Reactions
Acute allergic reactions cause a range of clinical signs during or within a few hours of a transfusion. Canine allergic reactions typically involve the skin and GI tract, with urticaria, edema, and vomiting commonly reported. Feline allergic reactions are primarily respiratory in nature and can cause dyspnea, although skin and GI signs can also occur. More severe allergic and anaphylactic reactions can cause hypotension and shock. Antihistamines are used to treat mild allergic reactions.
For clinical signs of anaphylaxis, epinephrine and other supportive care, as indicated, are administered.
Infection
Transfusion-transmitted infection reactions arise after transfusion of pathogen-contaminated blood products. Clinical signs depend on the pathogen transmitted. Bacterial contamination of blood products can lead to a range of clinical signs, including vomiting, fever, and shock. Samples of the transfused product and of the recipient's blood should be cultured to investigate suspected bacterial contamination.
Xenotransfusion
Transfusion of canine blood to a feline recipient (xenotransfusion) has been occasionally reported as an option for transfusing cats, especially when type B blood is not available for a type B recipient. Transfused canine RBCs have a short half-life in feline recipients, and there is risk of AHTR. Crossmatching is recommended before xenotransfusion to identify the most suitable transfusion product. Xenotransfusion is only indicated if all other compatible species-specific transfusion options are exhausted and warrants close consultation with clients regarding associated risks.
Neonatal Isoerythrolysis
Type B queens have high titer, naturally occurring alloantibodies against type A erythrocytes, and their colostrum contains a high concentration of these anti-A antibodies. Type A or AB offspring born to a type B queen acquire anti-A antibodies in colostrum. In a neonate during the first 24 hours after birth, intestinal permeability is increased, and antibodies are absorbed systemically, leading to hemolysis. Consequently, during this period, type A and AB kittens should receive alternative feeding. Because intestinal permeability decreases within 24 hours of birth, kittens can return to nurse from the queen 24 hours after birth. Genotyping can identify B/B breeding pairs to prevent neonatal isoerythrolysis.
Key Points
Blood typing for DEA 1 is strongly recommended before transfusion in dogs; AB blood typing is essential before transfusion in cats.
Cats can have naturally occurring alloantibodies against other blood types; both cats and dogs can acquire antibodies against nonself blood types through transfusion exposure.
Major crossmatching is recommended in dogs > 4 days after any transfusion and in cats, regardless of previous transfusion history, > 2 days after prior transfusion to decrease risk of immunological incompatibility between blood donors and recipients.
For More Information
Wardrop KJ, Birkenheuer A, Blais MC, et al. Update on canine and feline blood donor screening for blood-borne pathogens. J Vet Intern Med. 2016;30(1):15-35.
Wardrop KJ, Davidow EB. Laboratory testing in transfusion medicine. Vet Clin North Am Small Anim Pract. 2023;53(1):265-278.
Davidow EB, Blois SL, Goy‐Thollot I, et al. Association of Veterinary Hematology and Transfusion Medicine (AVHTM) transfusion reaction small animal consensus statement (TRACS) part 1: definitions and clinical signs. J Vet Emerg Crit Car. 2021;31(2):141-166.
Davidow EB, Blois SL, Goy‐Thollot I, et al. Association of Veterinary Hematology and Transfusion Medicine (AVHTM) transfusion reaction small animal consensus statement (TRACS) part 2: prevention and monitoring. J Vet Emerg Crit Car. 2021;31(2):167-188.
Odunayo A, Nash KJ, Davidow EB, et al. Association of Veterinary Hematology and Transfusion Medicine (AVHTM) transfusion reaction small animal consensus statement (TRACS) part 3: diagnosis and treatment. J Vet Emerg Crit Car. 2021;31(2):189-203.
Also see pet owner content regarding blood groups and blood transfusions in dogs and cats.
