When might a cat need a blood transfusion?

The most common reason for blood transfusions in cats is severe anemia. Blood loss may be caused by hemolysis (destruction of blood cells) or ineffective erythropoiesis (production of red blood cells).

The decision on whether or not your cat will need a blood transfusion will depend on their hematocrit (Hct). If your cat’s Hct is below 10-15%, a red blood cell (RBC) transfusion is recommended. Most anemia cases in cats are acute (sudden onset). If acute anemia is present or if your cat needs surgery, blood transfusions can be given even with higher Hct values.

Other important parameters that are taken into consideration to determine whether or not your cat will need a blood transfusion include:

• Tachycardia (increased heart rate)
• Weak pulse
• Lethargy
• Prolonged capillary refill time
• Other weakness indicators

Blood Groups in Cats

There are three general blood groups in cats - A, B, and AB. Group A is the most common and is predominant among European and American short- and longhair cats. Group B appears to be common in some pedigree feline breeds. Group AB is the rarest among these blood groups but is considered to be the most important.

Blood compatibility should be determined first before cats can be given a blood transfusion. A non-compatible blood transfusion can increase the risk of a cat developing severe life-threatening reactions. This negative reaction can occur because cats naturally possess antibodies against the blood group that they are lacking.

However, during the first weeks of a kitten’s life, they don’t have antibodies against other blood groups. This is especially true in kittens with type A or type B blood. Cats with type AB don’t have anti-A or anti-B antibodies.

Adverse reactions usually occur in cats with type B blood because they have naturally high levels of antibodies against type A blood. But reactions can also occur in type A cats against type B blood.

The Mik Blood Group in Cats

Recently, another blood group system has been identified in domestic shorthair cats. This is known as the “Mik antigen”; this means there are cats that are Mik positive or Mik negative. Adverse blood transfusion reactions can also occur in incompatible Mik transfusions.

Blood Typing and Blood Crossmatching (BCM) for Cats

Before a cat can have a blood transfusion, blood typing should be performed. There are special kits and laboratory procedures for this purpose.

If blood typing is not possible, such as during an emergency, a BCM can be done. Blood crossmatching determines whether the antibodies of the donor cat and recipient cat are compatible or not. Since BCM is only capable of detecting the antibodies that are currently present in the donor or recipient, it can increase the recipient cat’s risk for adverse reactions during future transfusions.

What happens during a cat’s blood transfusion?

Like in humans, blood transfusions in cats are performed using a special transfusion set.

At the onset, the rate of transfusion should be very slow, that is, 1-3 ml over 5 minutes. This should be done even with blood-typed or cross-matched blood transfusions. The recipient cat should be closely monitored for any sign of an adverse reaction triggered by incompatibility. If there’s none, the transfusion rate is gradually increased. A transfusion should be completed within 4 hours from the start to minimize or altogether prevent the risk of bacterial growth.

However, if the recipient cat has suffered a massive hemorrhage, blood transfusion should be given as rapidly as possible.

Can adverse reactions occur during blood transfusions in cats?

When a Type B cat receives Type A blood, this is an incompatible blood transfusion with a very high risk of a severe acute reaction. The symptoms include:

• Lethargy
• Bradycardia (abnormally slow heartbeat)
• Breathing problems - panting (dyspnea)
• Irregular heart rhythm (cardiac arrhythmia)
• Drooling (salivation)
• Vomiting
• Defecation and urination
• Neurological symptoms

The adverse reactions that can develop when type A cats are transfused with type B blood are generally milder. The symptoms that may be exhibited by the cat include restlessness, increased heart rate, and rapid breathing (tachypnea). However, this type of transfusion is not a viable option because red blood cells are rapidly destroyed.

For better results, type A recipient cats should only be transfused with blood from type A donors and type B cats with only type B blood. Since type AB cats don’t possess antibodies for Type A or B, they can be transfused with type AB, A, and B.

Identifying the type of naturally occurring antibodies is also important for cat breeders since type A kittens whose mother is type B have higher risks of developing neonatal isoerythrolysis.

Can transfusion reactions be prevented?

Blood transfusions can be life-saving but they’re not without potential problems, some of which can be serious and life-threatening. Any reaction to a blood transfusion generally appears during or shortly after the transfusion.

Fortunately, certain precautionary measures can help avoid transfusion-associated problems. In addition to following the guidelines for major transfusion parameters, such as donor selection, blood typing, blood storage, and administration, the following precautions must be observed at all times.

• Steps must be made to make sure that the blood of donor and recipient cats are compatible. Ideally, cross-matching must be performed to identify Mik antigen and other possible incompatibilities.
• The donor cat should undergo screening for blood-borne diseases, such as feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), and feline infectious anemia.
• Precautions should be observed to avoid overloading the recipient cat’s blood circulation during transfusion. Generally, blood transfusions should be given slowly to prevent heart failure.
• The recipient cat should be closely monitored especially upon the start of the transfusion so that any adverse reactions can be identified and the transfusion stopped.

With proper donor selection and appropriate compatibility screening, blood transfusions are well tolerated, appear effective, and may increase the chances of a cat’s survival.

Read more:

Feline Infectious Peritonitis (FIP)

Protecting Your Cat from Feline Distemper

Why is my cat panting?

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