What is the preoperative evaluation and management of heparin and warfarin?

Updated: Mar 16, 2020
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
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Heparin is a glycosaminoglycan with potent anticoagulant activity. Its anticoagulant activity is due to a portion of the molecule's high affinity binding to antithrombin III and subsequent acceleration of its already potent anticoagulant action. Heparin also inhibits platelet function and increases the permeability of vessel walls. Low-dose heparin (5000 U subcutaneously bid) has a negligible effect on measurable coagulation and does not require discontinuation or adjustment prior to surgery. Full-dose intravenous or subcutaneous heparin does have a significant effect and needs to be stopped prior to surgery. The half-life of standard heparin ranges from approximately 45-60 minutes. Therefore, it should be discontinued 5 half-lives, or at least 5 hours, prior to the surgery.

Low molecular weight heparin (eg, enoxaparin) is a relatively new heparin that is increasingly being used. It has a lower molecular weight and negligible effects on platelet function and vascular permeability. It inhibits activated factor Xa. The average half-life of low molecular weight heparin is approximately 3 hours. Therefore, discontinuation at least 15 hours prior to surgery is recommended.

Warfarin (Coumadin) is another commonly used anticoagulant that acts by inhibiting a hepatic microsomal reductase that converts vitamin K to its active form. With vitamin K in an inactive form, the vitamin K–dependent clotting factors cannot be formed. Anticoagulant effects are delayed in onset and persist for several days after discontinuation. Stopping warfarin at least 3 days prior to surgery is recommended. In situations in which anticoagulation is absolutely necessary, heparin can be started while warfarin is stopped. The heparin can then be stopped hours prior to surgery. Warfarin can be restarted at the presurgery dosage 1 day after surgery.

Always carefully consider the underlying reason (eg, stroke, thrombosis) for anticoagulation before it is discontinued. For many patients, the risks of discontinuing their anticoagulant agents exceed the risk of perioperative bleeding, which may be as low as 1.6%. Thoughtful consideration of the risk-to-benefit ratio is needed. Consultation with the patient's primary care physician is warranted if any doubt exists with regard to managing the perioperative dose of warfarin or heparin.

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