Adverse Effects of Blood Transfusion

This chapter outlines the clinical signs and the associated physiologic mechanisms of transfusion reactions for the small animal practitioner. Febrile or allergic reactions may occur in the same manner as severe hemolytic reaction. For this reason, any change in the patient's condition during blood infusion should be considered a possible sign of adverse reaction and should be evaluated. Acute hemolytic transfusion reactions occur within 24 hours of a red cell transfusion. Primarily mediated by immunoglobulin G (IgG), they are antigen-antibody, type 2 hypersensitivity reactions and result in an abrupt hemolytic transfusion reaction with intravascular hemolysis. Since dogs lack clinically significant red cell alloantibodies, acute hemolytic transfusion reactions are primarily caused by sensitization from a previous blood transfusion. Delayed hemolytic transfusion reactions occur more than 24 hours after transfusion, with onset varying from 2 to 21 days. These reactions are often the result of an amnestic response to a red cell antigen that the recipient lacks.