What is a blood transfusion reaction?
A transfusion reaction is an adverse response by the body to a blood transfusion. There are two types of transfusion reactions: immunologic and non-immunologic.
With immunologic reactions, the transfusion recipient’s immune system has a reaction to the donated blood. Immunologic reactions include allergic reactions, hemolysis (in which the recipient’s immune system destroys the donated red blood cells), and other immune responses. Many transfusion reactions are classified as immunologic.
Non-immunologic reactions do not involve the immune system. Examples include fluid overload (when the body is unable to tolerate the increased blood volume that results from a transfusion), citrate toxicity (an uncommon reaction to an anticoagulant used in blood transfusions), infectious disease transmission, and bacterial contamination of the transfused blood.
Many transfusion reactions occur quickly, within seconds of starting the transfusion and up to 48 hours post-transfusion. In other cases, transfusion reactions may may not be observed until days or weeks after the transfusion. The reported incidence of transfusion reactions ranges from 1% to 26%, depending on the underlying cause.
What are the clinical signs of a blood transfusion reaction?
The clinical signs of a transfusion reaction vary depending on the type of reaction.
- The most common sign of a transfusion reaction is fever associated with an immunologic reaction.
- Allergic reactions may be accompanied by hives, itching, skin inflammation/redness, vomiting, or diarrhea.
- Patients may develop an elevated heart rate and rapid breathing. On physical examination, your veterinarian may note decreased blood pressure, pale gums, weak pulse, and other signs of decreased blood circulation.
- Patients experiencing hemolysis often develop a yellow color to their skin, eyes, and gums, a condition known as jaundice or icterus. The yellow color is caused by bilirubin, which is released from red blood cells as they are destroyed.
- Volume/fluid overload may lead to signs such as coughing, shortness of breath, and labored breathing, due to excess accumulation of fluid in the lungs.
- The clinical signs of infectious disease transmission and bacterial contamination vary based on the type of infection involved.
How is a blood transfusion reaction diagnosed?
In many cases, a transfusion reaction can be diagnosed based on clinical signs alone. If new clinical signs develop during or immediately after a blood transfusion, a transfusion reaction is frequently the cause of these signs. The diagnosis of a transfusion reaction may be confirmed using blood tests, urinalysis, or other tests, such as radiographs (X-rays). The tests performed to diagnose a transfusion reaction will vary depending on the type of transfusion reaction that your veterinarian suspects.
How is a blood transfusion reaction treated?
The first step in treating a transfusion reaction is to immediately stop the transfusion, if it is still being delivered. Your veterinarian will then provide supportive care for your cat, which often includes IV (intravenous) fluids to help maintain appropriate blood pressure.
"The first step in treating a transfusion reaction is to immediately stop the transfusion."
Your veterinarian will then administer medications specific to the type of reaction that your cat is experiencing. In the case of an allergic reaction, your veterinarian will administer antihistamines, corticosteroids and/or epinephrine (Adrenalin Chloride®) to stop the reaction. Patients with hemolytic reactions may receive prolonged courses of immunosuppressive drugs. Your veterinarian may give antibiotics if bacterial contamination is suspected or diuretics (“water pills”) if a fluid overload is suspected.
What is the prognosis for a blood transfusion reaction?
Prognosis varies depending on the severity of the reaction and the patient’s overall health status. Mild reactions in otherwise healthy cats have a favorable prognosis, while the prognosis is less certain if a sick or elderly cat experiences a severe reaction.
How can I reduce the likelihood of a blood transfusion reaction?
Prior to a blood transfusion, your veterinarian may perform tests to help ensure the donor blood is a good match for your cat. Like humans, cats can have different blood types. Blood types in cats use an AB system, in which cats may have Type A blood, Type B blood, or Type AB blood (rare).
After determining your cat’s blood type, your veterinarian can choose a blood donor with an appropriate blood type to decrease the likelihood of transfusion reaction. Your veterinarian may have access to a feline blood bank that carries both Type A and Type B blood that has already been tested for infectious diseases.
Cross-matching is an additional test that can be performed before a blood transfusion. This test examines the effect of antibodies in the donor and recipient blood and how these antibodies react with blood cells. This test may not be necessary for a cat’s first transfusion but should be done before any subsequent transfusions. The first transfusion introduces foreign red blood cells, which may prompt your cat’s immune system to make antibodies that will attack those foreign red blood cells in future transfusions.
Donor blood should always be screened for the presence of infectious diseases before it is transfused. This screening will decrease the likelihood of your cat contracting an infection such as feline leukemia, feline immunodeficiency virus, or mycoplasma.
In addition to these measures, your veterinarian will carefully track your cat’s vital signs before, during, and after a blood transfusion. This monitoring can help detect transfusion reactions early, improving the likelihood of successful treatment.
