Snapshot A 55-year-old man presents to the emergency room with lightheadedness and altered mental status. He is not accompanied by any family members, but a list of medications was found in his wallet, including coumadin. On physical exam, he is noted to be pale. Laboratory examination reveals low hemoglobin to 7.0 g/dL, and an elevated INR at 4. He is found to be type O blood and he is started on a red blood cell transfusion. A few minutes after, he begins having shaking chills and was found to be febrile with hypotension. After double checking the blood product, it is noted that the wrong blood product, which was type AB, was given to the patient. The transfusion is immediately stopped and he is admitted to the intensive care unit for close monitoring and repeat transfusion with the right blood products. Introduction Overview acute hemolytic transfusion reaction occurs after transfusion causing ABO blood group incompatibility immune-mediated reaction is caused by IgM anti-A, anti-B, or anti-A and B antibodies and can be life threatening nonimmune mediated caused by non-ABO antibodies have milder clinical courses Epidemiology Incidence relatively rare given screening measures in place Risk factors group O recipient history of previous transfusion reaction misidentification of recipient or donor blood components ETIOLOGY Pathogenesis mechanism immune-mediated complement-mediated intravascular hemolysis tumor necrosis factor may play a role in end-organ damage nonimmune-mediated results in extravascular sequestration and damaged transfused RBCs Presentation Symptoms symptoms often occur early in the transfusion, often minutes after starting common symptoms fever chills red urine flank/back pain Physical exam inspection flushing wheezing hypotension Studies Serum labs repeat ABO typing repeat crossmatch testing direct Coombs test positive direct antiglobulin reaction serial hemoglobin levels hemolysis labs low haptoglobin elevated lactate dehydrogenase (LDH) Urine dipstick hemoglobinuria Differential Transfusion-related acute lung injury key distinguishing factor another transfusion reaction that is characterized by shortness of breath, hypoxemia, and rales Treatment Medical cessation of transfusion hemodynamic supportive care large bore intravenous access with normal saline decrease risk of renal failure mannitol may also decrease the risk of renal failure monitor for disseminated intravascular coagulation diuretics if patient is at risk for circulatory overload Complications Renal failure Disseminated intravascular coagulation (DIC) Prognosis Worse prognosis in group O recipient receiving group AB or group A red blood cell transfusion Mortality increases with volume of incompatible blood transfused