Pathophysiology
Clinical meaning
Blood transfusion reactions result from recipient immune response to foreign antigens on donor blood components. Acute hemolytic transfusion reactions (AHTR) are the most dangerous, caused by ABO incompatibility where pre-formed IgM antibodies bind donor red blood cells, activating complement cascade leading to intravascular hemolysis, hemoglobinemia, hemoglobinuria, DIC, and renal failure. Febrile non-hemolytic reactions are the most common, caused by recipient antibodies reacting to donor white blood cell antigens or cytokines accumulated during storage. Transfusion-related acute lung injury (TRALI) involves donor antibodies activating recipient neutrophils in pulmonary capillaries, causing non-cardiogenic pulmonary edema. Transfusion-associated circulatory overload (TACO) results from volume overload, particularly in patients with compromised cardiac function.