OK, let's be honest: You really cannot prevent the physiologic mechanisms of a transfusion reaction with premedication. All you can do is mask the clinical manifestations of several of them. Before I get too far ahead of myself, let's make sure you understand what "premedication" means.
Pre-transfusion medication is most commonly a dose of roughly 325 mg of acetaminophen (a.k.a. Tylenol) and 25 mg of diphenhydramine (a.k.a. Benadryl). These are given a half hour or so before transfusion, with the intention of specifically masking the fever and rash of some transfusion reactions. Here is where some disagreement begins. Many people believe that giving premedication is the "lazy" way out, designed to give a resident or intern a chance to sleep through the night. Further, the argument goes, masking the manifestations of transfusion reactions is not only a lazy idea, but a dangerous one, too! "If my patient is having a reaction, I need to know about it, doggone it!"
Well, I'm certainly in favor of careful patient monitoring during transfusion, as well as for the prevention of interns and residents sleeping through the night (that's why I'm a pathologist, by the way!), but the argument calling this practice dangerous simply doesn't hold water, in my opinion! Realistically, 325 mg of acetaminophen will prevent only the febrile manifestations of a febrile nonhemolytic transfusion reaction, which is a benign reaction anyway! Acute hemolytic reactions are strong and mighty, and should break through the puny little bit of Tylenol like Hercules snapping a pencil! The same analogy applies for Benadryl: urticarial reactions will be suppressed (at least partly), while anaphylactic reactions just laugh at that puny medicine!
So, if premedication only prevents things you don't care about anyway, what's the big deal about using it? Personally, I don't see the drawbacks. I should be fair and say, however, that some big-time Heme-Onc docs I know believe that acetaminophen premedication shouldn't be used in neutropenic patients, but primarily because of the potential of blocking a neutropenic fever (a separate issue entirely).
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