Anaphylactic Reactions
PRESENTATION: The classic anaphylactic reaction is fast, severe, and dramatic!
Anapylactic reactions are unique among transfusion reactions because of the sheer speed with which they occur. A patient can be peacefully sitting/lying there, in no distress whatsoever (other than their need for a transfusion), and mere moments later be on death's door. I'm not trying to be overly dramatic, but that is how sudden these reactions can be.
Problems usually begin after the patient receives the first few drops of the transfused product. All blood products have been implicated, though the less plasma a product has, the less likely a product is to cause anaphylaxis according to recent data from the "Serious Hazards of Transfusion" (SHOT) initiative in the United Kingdom and Ireland. Anaphylaxis occurs rapidly, with systemic shutdown including hypotension, shock, loss of consciousness, and gastrointestinal symptoms such as vomiting, diarrhea, and cramps. I call this an "acute crash." Typically, fever is not present, and this is an important distinguishing factor between anaphylactic reactions and the other reactions that it can look like.
There are some allergic-type reactions that fall somewhere on the spectrum between the really benign and boring urticarial reaction and these full-blown anaphylactic reactions. Some people refer to these as "anaphylactoid" reactions, and you can click here for more information about them.
Let's move on to the mechanism of an anaphylactic reaction.
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