A New Way To Reverse Excessive Blood Thinning from Warfarin

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The summary below is from the full report titled "Reversal of Warfarin-Induced Excessive Anticoagulation with Recombinant Human Factor VIIa Concentrate." It is in the 3 December 2002 issue of Annals of Internal Medicine (volume 137, pages 884-888). The authors are RAE Deveras and CM Kessler.

What is the problem and what is known about it so far?

Warfarin is a drug that "thins the blood" by interfering with normal blood clotting. Doctors prescribe warfarin to prevent blood clots in the legs, lungs, heart, and brain. People who take warfarin need frequent blood tests to make sure that the extent of blood thinning is appropriate. If the blood is thinned too much, serious bleeding from the nose or lungs or in the urine and gastrointestinal tract can occur. Doctors use different methods to reverse excessive blood thinning (excessive anticoagulation) from warfarin. If the degree of thinning is high but there is no bleeding, doctors decrease or stop warfarin therapy and watch the patient carefully. They also may give vitamin K to speed the reversal of warfarin's effects. If the patient is bleeding or needs an immediate procedure that could be complicated by bleeding (such as surgery), doctors give blood products (such as fresh-frozen plasma) through the vein to rapidly reverse anticoagulation from warfarin. Sometimes it is difficult to obtain and give the blood products quickly, and blood products have potentially serious side effects. Other ways to rapidly counteract anticoagulation from warfarin are needed.

Why did the researchers do this particular study?

To see whether a human-made agent (human recombinant factor VIIa concentrate, or rFVIIa) that was originally developed to control bleeding in patients with hemophilia would safely and rapidly reverse anticoagulation from warfarin.

Who was studied?

The study included 13 patients who had highly thinned blood from warfarin and needed rapid reversal of anticoagulation.

How was the study done?

The researchers gave each patient a single dose of rFVIIa in the vein. They did blood tests (prothrombin times and international normalized ratios) that measured the amount of blood thinning before and after they gave rFVIIa. They also assessed whether bleeding was stopped or prevented and whether rFVIIa had any harmful effects.

What did the researchers find?

All patients had immediate reversal of blood thinning with rFVIIa. Four patients who were bleeding from too much warfarin stopped bleeding. No patients who had invasive procedures developed bleeding complications from too much anticoagulation. No adverse side effects were reported.

What were the limitations of the study?

The study was small and did not directly compare different ways of reversing anticoagulation from warfarin.

What are the implications of the study?

Recombinant factor VIIa is a promising new way to rapidly reverse too much anticoagulation from warfarin. We now need studies that directly compare benefits, harms, and costs of rFVIIa with traditional ways of reversing too much anticoagulation.