Practical Challenges in the Management of Oral Anticoagulation

Steven R. Kayser, PharmD


Prog Cardiovasc Nurs. 2005;20(2):80-85. 

In This Article

Interruption of Therapy

For patients requiring prolonged or lifetime therapy with warfarin, interruption of warfarin may be problematic. The easiest way to manage interruption in patients undergoing short-term anticoagulation therapy (6 months) is to wait until therapy has been completed to perform the procedure. For others, careful planning and communication is key. The best way to approach these situations is to carefully consider and balance the risks of bleeding and the risks of thrombosis ( Table III ). For example, if a patient falls into a low-bleeding-risk and low-thrombosis category, it may be safe to withhold warfarin for a period of time. If the patient is considered a high thrombotic risk, regardless of the likelihood of bleeding, anticoagulation must be continued, requiring discontinuation of warfarin and switching to heparin for a period of time.

For many years it was recommended to discontinue warfarin to perform dental work. It is now recognized that this may not only be unnecessary, but that it may be dangerous. Numerous studies have shown that routine dental work and many extractions may be performed when the INR is within the range of 2-3.[18,19] Guidelines have been developed for performance of gastrointestinal procedures,[20,21] dermatologic procedures, and dental procedures.

If the surgical procedure does require interruption of warfarin therapy, careful planning is essential to minimize the time that the patient remains subtherapeutic.[22] If the INR is within the range of 2-3, several days may be required for the INR to drop to less than 1.5 and a corresponding time to be restored to the range of 2-3. If it is necessary to perform the procedure urgently, administration of vitamin K will decrease the INR within 6-8 hours with IV administration and 24 hours following oral administration. Vitamin K given subcutaneously is erratically absorbed and works no faster than when given orally.[23,24,25] Administration of vitamin K may result in relative resistance to resumption of warfarin, so the dose of vitamin K should be the lowest required. If immediate reversal is required, fresh frozen plasma will return the INR toward normal and last for approximately 4 hours. The volume required may be poorly tolerated in patients who have evidence of increased intravascular volume.[26]

Patients with prosthetic heart valves who require interruption of therapy may require "bridging" with heparin and this may be accomplished with LMW heparins in many instances.[5] For patients who are found to have an elevated INR and are not bleeding, and in whom complete reversal of the INR is not desired, small oral doses of vitamin K can bring the INR down within 24 hours.[27] Guidelines for management of high INRs have been recently published as part of the seventh Consensus Conference on Antithrombotic Therapy, published by the American College of Chest Physicians ( Table IV ).[6] If the INR is elevated, it is important to attempt to discover the reason, as well as make sure there is no bleeding. If no bleeding is present and the INR is >5, holding several doses will result in a decrease over several days. Administration of 2.5 mg of vitamin K orally has been shown to decrease the INR to <5 and, in most cases, to within the desired therapeutic range within 24 hours. Small doses have not been associated with resistance to subsequent reinstitution of warfarin. If the INR is >10, larger doses may be required (for example, 5 mg). Some recent experience shows that doses as low as 1 mg may also work. To administer 1 mg, it may be necessary to go to a health food store to purchase 100 µg tablets, since the only commercial source of oral vitamin K available from the pharmaceutical industry is 5 mg. IV vitamin K can be administered orally, but this is not as well accepted and is more expensive.


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