Warfarin: PreOperative Procedure

Discontinuation

• typically discontinue warfarin five days before elective surgery  and, when possible, check the PT/INR on the day before surgery
• If the INR is >1.5, administer low dose oral vitamin K (eg, 1 to 2 mg) to hasten normalization of the PT/INR and recheck the following day.
• proceed with surgery when the INR is ≤1.4. An INR in the normal range is especially important in patients undergoing surgery associated with a high bleeding risk (eg, intracranial, spinal, urologic) or if neuraxial anesthesia is to be used
• This timing of warfarin discontinuation is based on the biological half-life of warfarin (36 to 42 hours) and the observed time for the PT/INR to return to normal after stopping warfarin (eg, two to three days for the INR to fall to below 2.0; four to six days to normalize)
• Normalization of the INR may take longer in patients receiving higher-intensity anticoagulation (INR 2.5 to 3.5), and in elderly individuals
• For a procedure that requires more rapid normalization of the INR, additional interventions may be needed to actively reverse the anticoagulant.
• This discontinuation schedule will produce a period of several days with subtherapeutic anticoagulation. As an example, it is estimated that if warfarin is withheld for five days before surgery and is restarted as soon as possible afterwards, patients would have a subtherapeutic INR for approximately eight days (four days before and four days after surgery)
• Thus, for patients at very high or high thromboembolic risk, bridging may be appropriate.

Use of bridging preoperatively

• generally reserve bridging for individuals considered at very high or high risk of thromboembolism (eg, recent stroke, mechanical heart valve, CHA₂DS₂-VASc score of 7 or 8, CHADS₂ score of 5 or 6) if they require interruption of warfarin
• In these cases, the bridging agent (eg, therapeutic dose subcutaneous low molecular weight [LMW] heparin) is started three days before surgery
• A bridging agent may also be appropriate if there is a prolonged period during which the patient cannot take oral medications (eg, postoperative ileus).

Restarting warfarin and postoperative bridging

• resume warfarin 12 to 24 hours after surgery, typically the evening of the day of surgery or the evening of the day after surgery, assuming there were no unexpected surgical issues that would increase bleeding risk and the patient is taking adequate oral fluids
• use the same dose the patient was receiving preoperatively
• After warfarin is restarted in the perioperative setting, it takes 5 to 10 days to attain a full anticoagulant effect as measured by an INR above 2.0.
• Thus, treat individuals at very high risk and some individuals with a high risk of thromboembolism with a heparin bridging agent during this period.

Reference:

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