What is a blood transfusion reaction?
A transfusion reaction is a medical reaction that occurs in response to a blood transfusion.
There are two types of transfusion reactions. Many reactions are classified as immunologic reactions, in which the immune system of the blood transfusion recipient has a reaction to the donated blood. Immunologic reactions include allergic reactions, hemolysis (in which the recipient’s immune system breaks down the donated red blood cells), and other types of immune responses.
Other transfusion reactions are non-immunologic. These reactions do not involve the immune system. Examples of non-immunologic transfusion reactions 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, or bacterial contamination of the transfused blood.
Many transfusion reactions occur acutely, within seconds of starting the transfusion up to 48 hours post-transfusion. In other cases, however, transfusion reactions may be delayed; these reactions may not be observed until days or weeks after the transfusion.
The overall reported incidence of transfusion reactions ranges from 5-25%.
What are the clinical signs of a blood transfusion reaction?
The clinical signs of a transfusion reaction vary depending on the type of reaction that occurs. The most common sign associated with a transfusion reaction is a fever, associated with an immunologic reaction.
Allergic reactions may be accompanied by hives, itching, skin inflammation/redness, vomiting, and diarrhea. Patients may also develop an elevated heart rate and rapid breathing. On physical examination, your veterinarian may note decreased blood pressure, pale gums, and other signs of decreased blood circulation.
"The most common sign associated with a transfusion reaction is a fever, associated with an immunologic reaction."
Patients experiencing hemolysis, in which the red blood cells are being broken down, often develop a yellow color to their skin, eyes, and gums. This is known as jaundice or icterus. The yellow color is caused by bilirubin, which is released from red blood cells as they burst within the bloodstream.
Volume/fluid overload may lead to excess accumulation of fluid in the lungs. This leads to signs such as coughing, shortness of breath, and labored breathing.
The clinical signs of infectious disease transmission and bacterial contamination vary, based upon 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 X-rays. The specific 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. This care often includes IV (intravenous) fluids to help maintain appropriate blood pressure.
"Your veterinarian will then administer medications specific to the type of reaction that your cat is experiencing."
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, steroids and/or epinephrine to stop the reaction. Patients with hemolytic reactions (in which their body is breaking down blood cells) may receive prolonged courses of immunosuppressive drugs. Your veterinarian may give antibiotics if bacterial contamination is suspected, or diuretics (medications that help in the elimination of fluid) if 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 more guarded if a sick or elderly cat experiences a severe reaction.
Is there a way to reduce the likelihood of my cat developing a blood transfusion reaction?
Prior to a blood transfusion, your veterinarian may perform tests to help ensure that the donor blood is a good match for your cat.
Just 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. 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.
"Just like humans, cats can have different blood types."
Cross matching is an additional test that can be performed prior to a blood transfusion. This test examines the effect of antibodies in the donor and recipients blood and how these antibodies will react with blood cells.
Prior to transfusions, donor blood should also be screened for the presence of infectious diseases. This screening will decrease the likelihood of your cat contracting an infection from receiving a blood donation.
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.