Transfusion reactions are usually separated into two categories: immunological and non-immunological. The most common reactions to transfusions are fever, vomiting and facial edema. These are generally mild. More severe reactions, including intravascular hemolysis, shock and dyspnea, are seen far less frequently. In a study of 133 cats administered 246 transfusions, adverse reactions were seen in 6.3% of the 191 whole blood or packed red cell transfusions. No reactions were seen with 55 fresh frozen plasma transfusions. The reactions consisted of (in decreasing frequency) transient pyrexia, delayed hemolysis, circulatory overload, facial edema, acute hemolysis and death. In a study of 131 dogs administered 163 packed red blood cell transfusions, 13% of the dogs suffered acute (vomiting, intravascular hemolysis, icterus) or delayed (rapid decrease in post-transfusion hematocrit) hemolytic transfusion reactions.
Transfusion reactions can be minimized (and even prevented in some instances) by crossmatching or typing animals prior to transfusion and by paying strict attention to transfusion procedures, e.g. maintaining strict aseptic techniques, infusing products slowly, not using out-of-date or discolored products, closely observing the animal during the transfusion procedure (especially in the first 15 to 30 minutes).
In general, treatment of transfusion reactions is symptomatic and logical. First and foremost, if a transfusion reaction develops, the transfusion should be stopped immediately (if the reaction is severe) or slowed (for milder reactions). The product should be sent for bacteriological culture (as well as a gram stain smear made from the bag to look for bacteria). The animal should be treated symptomatically, e.g. if showing signs of shock, intravenous fluid therapy at shock doses and corticosteroids should be initiated. If showing signs of an anaphylactic reaction, corticosteroids and/or antihistamines can be administered. Currently, it is not recommended to administer pre-transfusion corticosteroids and/or antihistamines to try and prevent an allergic-type transfusion reaction. These reactions are generally mild and can be minimized by slow transfusion rates and by not mixing multiple bags from different donors. If an animal is known to have had previous hypersensitivity reactions, then pre-medication with anti-allergic drugs is indicated.
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