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  Obtain consent when possible before administering blood transfusions and properly inform patients regarding the risk of developing complications.

  
  
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  Always transfuse leukocyte-reduced blood products to recipients who are immunocompromised to prevent graft versus host disease.

  
  
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  It may be difficult to clinically distinguish between benign (urticaria, simple febrile reactions) and more serious transfusion reactions (acute hemolysis, anaphylaxis, transfusion-associated acute lung injury, sepsis).

  
  
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  Whenever a transfusion reaction is suspected, immediately stop the transfusion, confirm that the correct blood product was administered to the correct recipient, and send samples of the transfused product and the recipient’s serum to the blood bank for further analysis.

Emergency transfusion of blood products is often necessary in the emergency department (ED) for life-threatening illness or injuries. Commonly transfused blood products include packed red blood cells (PRBCs), platelets, fresh-frozen plasma (FFP), and cryoprecipitate. In the United States, approximately 30 million units of blood components are transfused annually. Approximately 1% of patients receiving transfusions will develop a transfusion-related reaction, the most common being a simple febrile reaction. Transfusion reactions must be rapidly identified to prevent morbidity and mortality.

Acute intravascular hemolysis is due to ABO blood group incompatibility between the donor and recipient. Preformed antibodies in the patient’s serum react with antigens on the transfused PRBCs, resulting in complement-mediated intravascular RBC lysis. Patients present with chest pain, shortness of breath, back pain, fever, tachycardia, or shock. Complications include acute renal failure, disseminated intravascular coagulopathy (DIC), cardiovascular collapse, and death.

Delayed extravascular hemolysis is due to non-ABO blood group incompatibility between the donor and recipient. This type of hemolysis is the result of splenic removal of RBCs, which may present days to weeks after the transfusion and in general is not life-threatening.

Simple febrile reaction is the most common type of transfusion-related reaction, occurring in about 1–7% of all transfusions. It is caused by recipient antibodies to donor leukocytes. The risk is minimized by leukoreduction. Patients present with fever without urticaria, bronchospasm, or shock.

Type I hypersensitivity reactions include urticaria and anaphylaxis. Urticaria is the result of a mild reaction due to recipient antibodies to donor blood. Patients present with hives and pruritus without fever, bronchospasm, or shock. Anaphylaxis is a life-threatening reaction seen most commonly in immunoglobulin A (IgA)-deficient individuals who are transfused IgA-containing blood. Patients rapidly develop fever, airway obstruction, bronchospasm, urticaria, and/or shock.

Transfusion-associated acute lung injury (TRALI) may result in a life-threatening noncardiogenic pulmonary edema. It is associated with anti-HLA antibodies (higher rates in pregnant donors). It most commonly occurs after plasma transfusion but can occur from transfusion of any type of plasma-containing blood product (including PRBC, platelets, cryoprecipitate, etc). Signs and symptoms include fever, severe respiratory distress, noncardiogenic pulmonary edema and cardiovascular collapse.

Infectious complications to transfusion may be bacterial or viral. Bacterial infections are more common after platelet transfusion (stored at room temperature) and longer blood storage times. Organisms are most commonly skin or gastrointestinal flora. Diagnosis requires positive cultures from donor and recipient blood. Donor blood is prescreened for human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV), human T-lymphotropic virus (HTLV), West Nile virus (WNV), and parvovirus; nevertheless, there is a small risk of transmission of these pathogens (most commonly HCV) despite screening.

Massive transfusions put the patient at risk for developing coagulopathy, hyperkalemia, lactic acidosis, and hypothermia. Dilutional coagulopathy or thrombocytopenia can occur when >4 PRBCs are transfused within 1 hour or 10 units within 12 hours, without the addition of clotting factors or platelets. Hypocalcemia and metabolic alkalosis may occur due to the effect of citrate. Volume overload from transfusions is more common in the setting of underlying chronic cardiac or kidney disease as well as plasma transfusion. Patients present with acute pulmonary edema without fever or shock.

Graft-versus-host disease is a rare complication of transfusion seen in immunocompromised or familial recipients. It is associated with a very high mortality rate. Donor T lymphocytes attack recipient tissues. This complication is prevented by leukoreduction and irradiation. Patients may present with fever, rash, pneumonitis, abdominal pain, vomiting, diarrhea, transaminitis, and thrombocytopenia.

The incidence of transfusion-related complications is highlighted in Table 72-1