Transfusion Medicine III

• Allergic reactions are among the most common adverse reactions to transfusion
• Most allergic transfusion reactions are examples of Type I hypersensitivity reactions
• Symptoms of Allergic Transfusion Reactions

  Urticaria (Hives)

  Pruritis

  Flushing

  Localized Angioedema

  Wheezing
• Allergic Transfusion Reactions are treated by suspending the transfusion and then restarting if hives resolve
• 60-80% of patients receive an antihistamine prior to transfusion in the US even though there is no evidence that this significantly reduces the risk of allergic reaction
• For severe recurrent allergic reactions, red cell and platelet products can be washed to remove residual plasma
• Anaphylactic reactions have any/all symptoms associated with symptom allergic reactions plus severe hypotension (shock)
• Most anaphylactic reactions are due to Type I hypersensitivity reactions, but they can also be due to 1) IgA antibodies in patients with IgA deficiency, 2) pre-existing antibodies to certain other serum proteins, or 3) transfusion of allergens in donor blood products
• Anaphylactic reactions can be treated by 1) stopping transfusion, 2) maintaining oxygenation, and 3) stabilizing hypotension
• Anaphylactic reaction due to IgA deficiency can be treated by providing patient with products washed to deplete plasma proteins or products collected from IgA deficient donors
• Hemolytic transfusion reactions occur when antigen-positive RBCs are transfused to a patient who has an alloantibody (antibody to an antigen that the patient does not have)
• Acute hemolytic transfusion reactions occur within 24 hours of transfusion and the antibody is generally present at the time of transfusion
• Delayed hemolytic transfusion reactions occur more than 24 hours after transfusion and the alloantibody is generally not detectable at the time of transfusion but develops later
• Intravascular hemolysis requires the activation of complement and results in the intravascular lysis of RBCs
• IgM antibodies are potent activators of complement and initiate the complement cascade leading to formation of the membrane attack complex (MAC) and the lysis of RBCs
• Extravascular hemolysis involves the binding of IgG to the surface of RBCs which opsonizes them and results in their removal by the reticuloendothelial cells of the spleen and liver
• During extravascular hemolysis, phagocytic cells of the reticuloendothelial system bind to the Fc of the IgG antibodies or to the C3b attached to the RBCs
• Symptoms of Acute Hemolytic Reactions

  Fever/Chills

  Pain

  Dypsnea

  Hypotension

  Hemoglobinemia, -uria

  Low Haptoglobin; High LDH
• Symptoms of Delayed Hemolytic Reactions

  Minimal Symptoms

  Unexpected Anemia

  Jaundice (occasional)
• The majority of acute hemolytic reactions are caused by clerical errors
• Lab Evaluation of Acute Hemolytic Reactions

  Hemolysis (visual)

  Confirm patient ABO

  Direct Antiglobin Test (+ in hemolytic reaction --> confirmatory)
• The main pathophysiological result of extravascular hemolysis is increased bilirubin
• The main pathophysiological result of intravascular hemolysis is hemoglobinemia and hemoglobinuria
• The most significant threats of acute hemolytic reactions are 1) renal failure and 2) disseminated intravascular coagulation
• Treatment for acute hemolytic transfusion reactions includes 1) stopping transfusion, 2) maintaining venous access, 3) maintaining urine output, 4) maintaining BP and 5) monitoring coagulation status
• In delayed hemolytic transfusion reactions, the red cell antibody develops in the recipient 7-21 days after the transfusion resulting in the destruction of the remaining transfused red cells
• Treatment for delayed hemolytic transfusion reactions is often unnecessary
• Both Transfusion Related Acute Lung Injury (TRALI) and Transfusion Associated Circulatory Overload (TACO) present with respiratory distress accompanied by a chest XR showing bilateral pulmonary infiltrates
• The distinguishing symptoms of Transfusion Related Acute Lung Injury are 1) fever/chills, 2) hypotension, and 3) CVP: normal to low
• The distinguishing symptoms of Transfusion Associated Circulatory Overload are 1) orthopnea, 2) hypertension, 3) elevated CVP and 4) elevated BNP
• We know that one of the mechanisms of TRALI is donor antibodies directed against recipient leukocytes
• Treatment for TRALI involves 1) stopping transfusion, 2) providing respiratory support, 3) vasopressors for hypotension
• TRALI is the most common cause of transfusion related death in the US
• One way to prevent TRALI is to minimize the use of donors who have an increased chance of having anti-leukocyte antibodies (e.g. multiparous women)
• Treatment for TACO involves 1) stopping transfusion, 2) managing symptoms and 3) diuretics
• TACO can be prevented by managing volume in susceptible patients and slowing infusion rate
• Febrile non-hemolytic transfusion reactions involve an increase in temperature within 4 hours of transfusion and are caused by WBCs and cytokines elaborated in the donor blood product
• Febrile non-hemolytic transfusion reactions can be treated with antipyretics and prevented by leukoreduction of blood products
• TA-Graft vs. -Host Disease is rare and only affects severely immunocompromised patients
• Symptoms of TA-Graft vs. -Host Disease include rash, liver function test abnormalities, diarrhea, N/V and pancytopenia