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Transfusion reactions are defined as adverse events associated with the transfusion of whole blood or one of its components. These may range in severity from minor to life-threatening. Reactions can occur during the transfusion (acute transfusion reactions) or days to weeks later (delayed transfusion reactions) and may be immunologic or non-immunologic. A reaction may be difficult to diagnose as it can present with non-specific, often overlapping symptoms. The most common signs and symptoms include fever, chills, urticaria (hives), and itching. Some symptoms resolve with little or no treatment. However, respiratory distress, high fever, hypotension (low blood pressure), and red urine (hemoglobinuria) can indicate a more serious reaction. Types of transfusion reactions include the following: acute hemolytic, delayed hemolytic, febrile non-hemolytic, anaphylactic, simple allergic, septic (bacterial contamination), transfusion-related acute lung injury (TRALI), and transfusion-associated circulatory overload (TACO). All suspected reactions should result in immediately stopping the transfusion and notifying the blood bank and treating clinician. Acute Transfusion Reactions Mild allergic: Attributed to hypersensitivity to a foreign protein in the donor product. Anaphylactic: Similar to a mild allergic reaction, however resulting in a more severe reaction. Sometimes this can occur in a patient with IgA deficiency who makes alloantibodies against IgA and then receives blood products containing IgA. Febrile non-hemolytic: Generally thought to be caused by cytokines released from blood donor leukocytes (white blood cells). Septic: Caused by bacteria or bacterial byproducts (such as endotoxin) which may contaminate blood. Acute hemolytic transfusion reactions: Can result in intravascular or extravascular hemolysis, depending on the specific etiology (cause). Immune-mediated reactions are often a result of recipient antibodies present to blood donor antigens. Non-immune reactions are possible, and occur when red blood cells are damaged before transfusion (e.g., by heat or incorrect osmotic conditions). Transfusion-associated circulatory overload (TACO): Occurs when the volume of the transfused component causes hypervolemia (volume overload). Transfusion-related acute lung injury: Acute lung injury is due to antibodies in the donor product (human leukocyte antigen or human neutrophil antigen) reacting with antigens in the recipient. The recipient’s immune system responds and causes the release of mediators that lead to pulmonary edema. Possibly contributing to this are clinical conditions that predispose the patient including infection, recent surgery, or inflammation. Delayed Transfusion Reactions Delayed hemolytic transfusion reaction: Typically caused by an anamnestic response to a foreign antigen that the patient was previously exposed to (generally by prior transfusion or pregnancy). Transfusion-associated graft-versus-host disease: Results from engraftment of donor lymphocytes (commonly found in cellular blood products) into an immunocompromised recipient’s bone marrow. The donor lymphocytes recognize the patient as foreign and react against the recipient’s body. The patient’s immune system is unable to clear the foreign lymphocytes. This is rare but often fatal. #BloodGroup #BloodType #bloodTransfussion
