A hemolytic transfusion reaction is a serious problem that occurs after a patient receives a transfusion of blood. The red blood cells that were given to the patient are destroyed by the patient's own immune system.

Blood is classified into different blood types called A, B, AB, and O.

The immune system normally can tell its own blood cells from blood cells from another person. If other blood cells enter your body, your immune system may make antibodies again them. These antibodies will work to destroy the blood cells that the body does not recognize. For example, a person with type A blood makes antibodies against type B blood cells.

Another way blood cells may be classified is by Rh factors. People who have Rh factors in their blood are called "Rh positive." People without these factors are called "Rh negative." Rh negative people form antibodies against Rh factor if they receive Rh positive blood.

There are also other factors to identify blood cells, in addition to ABO and Rh.

Blood that you receive in a transfusion must be compatible. Being compatible means that your body will not form antibodies against the blood you receive. Blood transfusion between compatible groups (such as O+ to O+) usually causes no problem. Blood transfusion between incompatible groups (such as A+ to O-) causes an immune response. This can lead to a very serious transfusion reaction. The immune system attacks the donated blood cells, causing them to burst.

Today, all blood is carefully screened. Modern lab methods and many checks have helped make these transfusion reactions very rare.

• Bloody urine
• Chills
• Fainting or dizziness
• Fever
• Flank pain or back pain
• Rash

Symptoms of transfusion reaction usually appear during or right after the transfusion. Sometimes, they may develop after several days (delayed reaction).

This disease may change the results of these tests:

• Bilirubin
• CBC
• Coombs' test, direct
• Coombs' test, indirect
• Fibrin degradation products
• Haptoglobin
• Hematocrit
• Hemoglobin
• RBC count
• Serum creatinine
• Serum hemoglobin
• Urinalysis

Therapy can prevent or treat the severe effects of a hemolytic transfusion reaction. If symptoms occur during the transfusion, the transfusion is stopped immediately. Blood samples from the person getting the transfusion and from the donor may be tested to tell whether symptoms are being caused by a transfusion reaction.

Mild symptoms may be treated with the following:

• Antihistamine drugs (such as diphenhydramine) can treat itching and rash.
• The pain reliever, acetaminophen can reduce fever and discomfort.
• Corticosteroids (such as prednisone or dexamethasone) can reduce the immune response.
• Fluids given through a vein (intravenous) and other medications may be used to treat or prevent kidney failure and shock.

The outcome depends on the severity of the reaction. The disorder may disappear without problems. Or, it may be severe and life threatening.

• Acute kidney failure
• Anemia
• Discomfort
• Lung dysfunction
• Shock

Tell your health care provider if you are having a blood transfusion and you have had a reaction before.

Donated blood is put into ABO and Rh groups to reduce the risk of transfusion reaction.

Before a transfusion, patient and donor blood is tested (crossmatched) to see if it is compatible. A small amount of donor blood is mixed with a small amount of patient blood. The mixture is checked under a microscope for signs of antibody reaction.

Before the transfusion is given, the health care provider will usually check again to make sure you are receiving the right unit of blood.

Goodnough L. Transfusion medicine. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 183.