Transfusion reactions can be broadly categorized into three categories: Hemolytic, Delayed Hemolytic, and Nonhemolytic transfusion reactions. Typical signs and symptoms of a hemolytic transfusion reaction include chest and flank pain, nausea, and chills. These can be masked while under general anesthesia and so, more useful indicators include fever, hypotension, or red colored urine (a result of hemoglobinuria – not frank RBC’s in the urine). If a hemolytic transfusion reaction is suspected, in addition to immediately terminating the transfusion and providing the appropriate supportive treatment, it is necessary to perform a laboratory investigation in the form of the following:
Direct antiglobulin test (Coombs Test): Should be performed on patient’s post-transfusion serum, if the test is positive and with a negative DAT on a pre-transfusion sample, then a hemolytic transfusion reaction may have occurred. Of note, a negative DAT on a post-transfusion sample does not preclude a hemolytic transfusion reaction, as if most or all of the transfused donor cells have been destroyed by intravascular hemolysis. In this event the test would be a false negative.
Repeat Crossmatching: Repeat ABO typing, Rh typing, and antibody screen of patient’s pre/post transfusion samples as well as donor unit samples. If both pretransfusion and posttransfusion blood samples return incompatible, then a pre-transfusion clerical error may be at fault. Of note, the post-transfusion antibody screen may result in a false negative if most of the patient’s antibody is bound to donor cells.
Urine Free Hemoglobin: Hemolysis will result in hemoglobinuria and thus a positive urine hemoglobin; however, the presence of intact RBC’s indicates bleeding into the urinary tract, NOT hemolysis.
Serum bilirubin: Bilirubin (unconjugated) can be elevated as a byproduct of hemolysis. It is important to note that these levels will peak within 5-7 hours after transfusion, and will return to baseline within 24 hours in the setting of normal renal function.
Serum haptoglobin: Best performed when comparing both pretransfusion and posttransfusion samples, a decrease in serum haptoglobin can indicate hemolysis as haptoglobin binds hemoglobin that is liberated from red blood cells during hemolysis. It is important to note that haptoglobin is an acute phase protein and can be increased in any inflammatory condition including surgery.