Crossmatching

Blood transfusion is becoming a common procedure performed in animals. Prior to transfusing, blood typing is performed to determine the blood type of the donor and recipient. Transfusing the same blood type can help reduce the risk of transfusion reaction. Unfortunately, transfusing the same blood type does not guarantee that a reaction will not occur. For this reason, cross matching is often performed. This can help determine if the blood that the animal is receiving is compatible with his own blood. Cross matching is also important if blood typing is not possible due to time constraints or lack of blood typing kits.

Cross matching is indicated before a blood transfusion, especially if the blood types of the donor and recipient are not known or if this is not the patient's first transfusion. Prior transfusions can predispose a pet to transfusion reaction, even if given the same blood type. Cross matching can help detect potential reactions and allow the veterinarian to select a more compatible blood product.

There are no real contraindications to performing this test in an animal prior to blood transfusion. However, if the pet has an illness that results in agglutination or red blood cell breakdown, cross matching cannot accurately be performed.

What Does Cross Matching Reveal?

Cross matching reveals whether or not the blood that is to be given to a pet will be compatible. Samples of the donor's red blood cells and plasma are combined with the recipient's red blood cells and plasma in a test tube. These samples are then examined for reactions. If a reaction is noted in the test tube, that donor is not used to supply a transfusion. Cross matching may need to be performed on several different donors to find blood that is compatible.

How Is Cross Matching Done?

A blood sample from the donor and the recipient are needed. These samples are collected in separate glass tubes. The blood is then separated into red blood cells and plasma. Based on what type of transfusion is to be given, a major or a minor cross match will be performed.

If red blood cells are to be transfused, a major cross match is performed. The donor's red blood cells are combined with the recipient's plasma. After mixing, the combined sample is examined for a breakdown of red blood cells. If a breakdown is noted, the blood is not compatible and should not be given.

If plasma is to be transfused, a minor cross match is performed. The donor's plasma is combined with the recipient's red blood cells. As with the major cross match, the sample is then examined for signs of red blood cell breakdown. If noted, the plasma should not be given.

If a whole blood transfusion is to be given, including both red blood cells and plasma, a major and a minor cross match should be performed. If incompatibility is noticed in either sample, the blood should not be given.

Usually, the cross match is performed in the veterinary hospital and is typically complete in 30 to 60 minutes. Sometimes, samples may be submitted to a laboratory for cross matching. This is usually done if a future transfusion is possible since the results may take 1 to 2 days.

Is Cross Matching Painful?

Any pain involved is associated with the collection of the blood sample, since a needle is used to pierce the skin and enter a blood vessel to draw the sample. As with people, the pain experienced from a needle will vary from individual to individual.

Is Sedation or Anesthesia Needed?

Neither sedation nor anesthesia is needed in most patients; however, some pets resent needle sticks and may need tranquilization or ultra short anesthesia.