The Acute Crash
A TRUE TRANSFUSION EMERGENCY: The situation that I call the "acute crash" occurs when a patient has total or near-total cardiorespiratory collapse within the first few moments of the transfusion.
This is a true and total emergency, and requires prompt and decisive action on the part of the transfusing staff. It may also require the Blood Bank physician to get involved on an emergency basis. In general, most of us are not particularly comfortable with that type of situation (that's partly why most of us are Pathologists; the other reason is that we are a group filled with an enormous number of tremendous geeks!), so it is critical to have a good, sound differential diagnosis in mind before you are faced with an acute crash. The three things that should be on the top of your list are: Acute hemolytic transfusion reaction, bacterial contamination, and anaphylactic reaction. In addition, transfusion-related acute lung injury may share some features with these entities. Finally, non-transfusion entities such as acute myocardial infarction, pulmonary embolism, etc, must be considered (though we won't talk about them here).
Acute Hemolytic Transfusion Reaction
Acute hemolytic reactions, as I have previously stated, must be at the top of your differential every time something unusual happens during a transfusion. In fact, if you assume acute hemolysis and make yourself disprove it, you will make it very difficult to miss one of these. In truth, however, acute hemolytic reactions don't usually present this way. Most acute hemolytic reactions have a more gradual onset, with fever and chills at the beginning, then progression into shock and/or DIC. ABO mismatches, in particular when a group O recipient gets blood from a group A or B donor, however, can give you an acute crash. Acute hemolysis must be treated by immediate cessation of the blood product, careful volume resusucitation and monitoring of renal function, and a careful watch for DIC.
Bacterial Contamination (Septic Reaction)
Contamination of blood products by bacteria (especially gram-negative bacteria) gives a patient an acquired sepsis, with all the usual manifestations. The usual culprit is the endotoxin from these contaminating organisms. Classically , patients with bacterial contamination present with an acute crash with a high fever in the first few minutes of transfusion. The fever is useful in the distinction from anaphylaxis (which is generally afebrile). The treatment of these reactions is discussed elsewhere, but the short version is that the patient needs IV antibiotics and careful monitoring right away.
Anaphylactic Transfusion Reaction
The last of these beastly reactions that may lead to an acute crash is the anaphylactic reaction. Anaphylaxis from transfusion is fortunately rare, and is often related to exposure to serum IgA in an IgA-deficient patient. Out of all of the acute reactions, this one is the most acute; they may occur in the first few drops of the transfusion. The classic way to tell anaphylaxis from bacterial contamination is by the lack of fever with anaphylaxis, but this is not always reliable. Since the treatment of anaphylaxic reactions is epinephrine (and we're talking RIGHT NOW!), and delays may be fatal, it not unreasonable to give epinephrine while waiting for antibiotics to arrive, or while you are trying to sort it all out.
A Word About TRALI
We don't always think about transfusion-related acute lung injury (TRALI) in the setting of the acute crash, because the symptoms are mainly respiratory. But, in the early stages of a TRALI reaction, a patient may have dramatic respiratory insufficiency that may be confused with one of the above diagnoses, especially with anaphylaxis. However, TRALI generally does not occur as dramatically or overwhelmingly as these other reactions.
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