Blood transfusion reactions are any of a number of reactions that occur during or after a blood transfusion. They are often a result of the cat’s immune system responding to donor blood cells and antibodies. Cats are blood typed similarly to humans, with Types A, B, and AB. Giving the wrong type of blood will result in immediate and often severe symptoms in most cats, the worst occurring when a Type B pet is given Type A blood. Proper blood type matching and cross-matching, correct blood storage, and proper transfusion practices will reduce the risk of blood transfusion reactions.

The symptoms of a blood transfusion reaction can occur immediately or may be delayed and begin a few days after the transfusion occurred. Any cat undergoing a blood transfusion should be carefully monitored for reactions during and after the transfusion. Reactions can be severe and in some cases fatal. Symptoms may also vary depending on the type of reaction your pet is experiencing. 

Symptoms Include:

There are several types of reactions a cat may have during or after a blood transfusion. The most common types are: 

Blood transfusion reactions can have several causes. Immune-mediated reactions are caused by the immune system’s natural response to the blood cells, platelets, and antibodies in the donor blood. In some cases, this is a result of a mismatch in the donor blood type and your pet’s blood type (for example a Type B cat being given Type A blood). This causes inflammation and blood cell breakdown, which results in serious symptoms and can result in death. Even with the right type of blood, the immune system could still develop antibodies that react with the donor blood, which causes the other immune-mediated reactions including acute lung injury and delayed reactions.

Transfusion reactions can also be caused by contaminated or tainted blood. Bacteria, viruses, and other diseases may contaminate donor blood. Blood storage practices can also cause transfusion reactions. Blood that has been stored at the wrong temperature or kept past its expiration date are some examples of improper blood storage. Other causes of reaction include volume overload from too much transfused blood or hypothermia caused by a transfusion of blood that is too cold.

Veterinarians are generally able to diagnose a blood transfusion reaction through observation of clinical signs and timing of symptoms. During and after a blood transfusion, your pet will be carefully monitored by veterinary staff for any signs of a reaction because there is some risk with any transfusion. Body temperature (rectal), urine output, pulse rate, breathing rate, color, and demeanor will be monitored and tracked to help quickly identify any potential issues. A preliminary diagnosis will be made if changes in these monitored conditions occur or if the cat starts to display other symptoms like vomiting and shaking or seizures. Veterinary staff will also check PCV or red blood cell levels for signs of reaction after the transfusion.

If a reaction is observed during a transfusion, the immediate treatment is slowing down or stopping the transfusion temporarily. In many cases, this will make minor reactions manageable, but it also gives the veterinarian an opportunity to analyze the reaction for additional treatments. Treatment will differ somewhat depending on the type of reaction the cat is having. Common treatments include:

Many cats that experience a blood transfusion reaction will have a full recovery. Immediate treatment increases your pet’s chances. To support your cat’s recovery, continue to monitor them after a transfusion for delayed reactions and signs of anemia. Bring your cat back to the veterinarian if you observe any changes in coloring, breathing, diet, or behavior.