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How to perform a crossmatch in a dog or cat | VETgirl Veterinary Continuing Education Videos

In this VETgirl online veterinary continuing education video, we demonstrate how to perform a crossmatch. This is a procedure that veterinary professionals must feel comfortable performing to ensure appropriate administration of blood products.

Often times, a blood type can be performed in lieu of crossmatching. However, in the patient that has been previously transfused or has evidence of agglutation, the use of crossmatch is imperative to ensure that the patient will tolerate the transfusion product well. The goal of performing a crossmatch is to look for the presence of antibodies in the recipient against the donor’s red blood cells. If an inappropriate blood product is given to a patient, a severe transfusion reaction can be seen in the form of a hemolytic reaction or even death.

In dogs, the most antigenic antibodies are DEA 1.1 and 1.2. Remember that dogs can typically be safely given their first transfusion; it’s not until a second transfusion that the patient has been sensitized to a previously transfused red cell antigen. Again, for a first time transfusion in a dog, a transfusion can be safely given without blood typing or crossmatching (VETgirl still recommends blood typing so you can appropriate utilize blood products in your hospital). For a second-time transfusion, a crossmatch must be performed. Check out our video on how to make a transfusion in your hospital for a dog here. For cats, check out this video. (NOTE: Videos are only available for our VETgirl ELITE members, and you must be logged in to check them out!).

In cats, a first time transfusion is never safe, as there is no universal donor in cats. Cats have naturally occurring antibody to red blood cell antigens. In cats, the most common blood type is Type A; however, B, AB and Mik also exist. Keep in mind that administration of the wrong blood type in a cat can result in acute death. Remember, B students hate A students. Type B cats hate Type A blood and can have acute hemolytic anemia and death with as little as 1 ml of blood.

So, how do we perform a crossmatch? Typically, we test for major and minor crossmatch. Major crossmatch is the most important and is testing for antibodies in the recipient against transfused donor red blood cell antigens. With the minor crossmatch, we are testing for antibodies in the donor’s serum to the patient/recipient’s red blood cells. Here, this video demonstrates how to perform this. Make sure to look for evidence of agglutination both macro- and microscopically.
If there is no reaction with the major crossmatch, the transfusion can be safely given. If there is reaction with a major crossmatch, the blood should NOT be given. If the minor crossmatch is compatible, the transfusion should be given however, if there is agglutination, ideally, the red blood cells should be washed. The likelihood of reaction is less severe, and in a bind, this can be given.

Need a refresher on transfusions? Watch our VETgirl ELITE video on transfusion medicine here again for a review!

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