27 Etiology: Delayed hemolytic reactions occur in patients who have undetectable levels of antibody when pretransfusion testing is performed, so that seemingly compatible units of red blood cells are transfused. Exposure to antigen positive red blood cells provokes an anamnestic response and increased synthesis of the corresponding antibody. After several days, the antibody titer becomes high enough to hemolyze transfused red cells. Symptoms: In most cases, delayed hemolytic reactions are asymptomatic and the only noticeable sign is a more rapid fall in the post-transfusion hemoglobin level than is clinically expected. Occasionally a patient experiences a flu-like illness. Fever is the most common symptom, followed by jaundice. In rare instances, hemolysis may be brisk (especially when Kidd antibodies are implicated) resulting in fever, hemoglobinemia and hemoglobinuria.

Consequences: Generally, delayed hemolytic reactions do not result in serious adverse sequelae. Occasionally, the decrease in a patient's hemoglobin associated with a delayed hemolytic transfusion reaction may be misdiagnosed as internal bleeding. Lab Data: Delayed hemolytic transfusion reactions are most often detected by the blood bank when laboratory tests reveal a positive direct antiglobulin test and/or an indirect antiglobulin test. Other lab findings include decreasing hemoglobin or hematocrit, increasing indirect bilirubin, and positive antibody screen posttransfusion.
Treatment: Treatment is rarely necessary. Urine output and renal function should be monitored. Transfusion of antigen negative blood may be necessary for treatment of anemia.

Prevention: The responsible antibody should be identified and all additional units should be negative for the corresponding antigen. When RBC antibodies are identified, patients should be informed and advised to provide this information when they are hospitalized elsewhere. Carrying a transfusion alert card is recommended. Physicians whose patients tell them about previously identified antibodies should immediately notify the Transfusion Service.

Last Updated on Monday, 18 July 2011