The use of FFP to counteract anticoagulants is something that is sometimes misunderstood by both blood banking students and clinicians. The answer to this question is not always a simple one (at least in terms of Warfarin, better known as Coumadin). Let's tackle these one by one.
FFP and Coumadin
The bleeding patient who is anticoagulated with Coumadin is a significant challenge. As you probably know, Coumadin acts by inhibiting the gamma carboxylation of factors II, VII, IX, and X (the vitamin K dependent factors) in the liver. In order to reverse the anticoagulation, that inhibition must be overcome by the production of sufficient quantities of normal factors. The mainstay of therapy for these patients is vitamin K, which is necessary in order for the factors listed above to be produced in normal forms. Vitamin K is typically given subcutaneously, and it works great! The problem is that it takes about 24 hours to work due to the need for absorption and transport to the liver. If you need help right away, that's not good enough!
Vitamin K may also be given intravenously, though there are some clinicians that don't like that idea due to cases of anaphylaxis that have been reported, but many have used IV vitamin K successfully. Obviously, absorption is not an issue when an intravenous dose is given, but it still takes awhile for the liver to replenish the depleted vitamin K-dependent factors sufficiently to make a difference. Most of the time, IV vitamin K takes about 6 hours to work. Again, if you can wait that long, then IV vitamin K is a good choice.
However, if you need to reverse the anticoagulant right away, there is really only one choice: FFP. This situation is seen most commonly in patients who are anticoagulated warfarin and have a major bleed for whatever reason (though it is also seen in Coumadin overdoses). In cases like this, there is simply not enough time to wait for vitamin K to work (in whatever form). So, the emergent reversal of Coumadin is an indication for the use of FFP.
FFP and Heparin
OK, what about using FFP for reversing the effects of heparin? First, remember that heparin works for anticoagulation by potentiating the effect of the anticoagulant antithrombin (aka, antithrombin III). Antithrombin strongly inhibits thrombin (surprise, surprise!) as well as factor X, as well as several other factors to a lesser extent. The key things to know about heparin are that it has an incredibly short half-life and that it is easily reversed by the medication protamine sulfate.
About once a year or so, I will get a call from the OR wanting to nail someone with a bunch of FFP because of an overload of heparin. Why would I have a problem with this? Well, for two reasons. First, heparin reverses so rapidly with protamine that it seems silly to give FFP that is going to take 20 minutes to thaw, in addition giving a patient exposure to a blood product unnecessarily. Secondly, but more important, is the fact that FFP stinks for reversing heparin! Think about this: Heparin works by potentiating antithrombin, right? You should know that up until the last few years when antithrombin concentrates became available, the product of choice for antithrombin deficiency was (you guessed it): FFP! So, we are going to try to reverse the effects of a drug by giving the patient the very thing that the drug works on? Doesn't make much sense to me, and I hope not to you, either.
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