Department: CLINICAL QUERIES
My patient has a history of recurrent pulmonary embolism (PE) for which he is currently taking warfarin. He has been scheduled for bilateral total knee arthroplasty (TKA). As part of the preoperative regimen, the physician has prescribed outpatient “warfarin bridging” with enoxaparin. How should I educate my patient about this process?—P.T., N.Y.
Morgan Elizabeth Weithman, PharmD; Amy Sieber, PharmD; Jessica Brewer, BSN, MSN, RN; and Daniel Sheridan, MS, RPh, respond: Many patients who are at high risk for deep vein thrombosis and/or PE are prescribed the anticoagulant warfarin for prophylaxis. If these patients need a major invasive procedure, such as TKA, or a high-bleed-risk procedure such as any cardiac, spinal, or neurologic surgery, the warfarin will be temporarily discontinued to reduce the risk of excessive bleeding during surgery. Because warfarin will not return to a therapeutic level for several days after it is resumed, the prescriber may order bridging with enoxaparin injections for perioperative antithrombotic therapy.
Bridging provides continuity of antithrombotic therapy, decreasing the risk of thrombosis. The transition generally spans 5 days before the procedure to several days or even a week or more after the procedure.
Before initiating bridging therapy, assess the patient for allergies, because systemic allergic reactions to enoxaparin have been documented.1 Also assess the patient's renal function and weight; dosing for enoxaparin is weight-based and may need adjustment in patients with renal dysfunction. If in doubt, ask the prescriber or a pharmacist.
Teach the patient or family caregiver proper dosage preparation and administration, including subcutaneous injection technique. Also teach the patient or family/caregiver to inject the medication at the same time each day and to alternate injection sites between the left and right anterolateral and left and right posterolateral abdominal wall.
As part of patient education, review the bridging protocol with the patient according to the following general outline. However, keep in mind that bridging is patient-specific and that the protocol may vary based on the patient's clinical status and the healthcare provider's judgment.2-4
- Instruct the patient to begin holding warfarin 5 days before the planned procedure or as otherwise directed by the provider. The provider may order an international normalized ratio (INR) level to make sure that the patient's INR is therapeutic before discontinuing warfarin.
- Initiate enoxaparin 24 hours or more following the first missed dose of warfarin or when the INR is estimated to be below the patient's INR goal range. Enoxaparin can be dosed at either 12- or 24-hour intervals depending on patient parameters such as weight and renal function. Enoxaparin injections should continue until 24 hours before the procedure.
- Instruct the patient to hold enoxaparin 24 hours before the procedure; otherwise, the procedure may need to be canceled or rescheduled due to the increased bleeding risk.
- Warfarin therapy should resume the evening postprocedure unless otherwise specified. In some cases, the provider may prescribe a dose that is slightly larger than usual for the first 1 to 2 days to help boost INR into the target range.
- Enoxaparin should be restarted when clinically appropriate. This is generally within 24 hours after surgery for patients undergoing a low-bleeding-risk procedure such as a colonoscopy or bronchoscopy, but may be up to 72 hours in high-bleeding-risk surgeries such as bowel resection or any cardiac surgery.
- Teach the patient to continue both warfarin and enoxaparin therapy for a minimum of 5 days postprocedure and until INR is at goal level before discontinuing enoxaparin, as directed by the healthcare provider. The provider will likely instruct the patient at subsequent follow-up visits when to stop the enoxaparin.
Make sure the patient has a personal bridging chart containing specific doses, dates, and times of when bridging medications (warfarin and enoxaparin) should be administered. The information should be tailored to the patient's literacy level.5 In addition:
- emphasize the need to resume warfarin dosing the evening postsurgery because warfarin needs several days to return to therapeutic levels in the body. This will allow the patient to discontinue enoxaparin injections as soon as the INR is in range (minimum of 5 days post-op).
- stress the importance of strictly adhering to the bridging regimen. Inform the patient that errors could be life-threatening in perioperative patients who are susceptible to both postoperative bleeding and thrombosis.
- reassess the patient's self-care knowledge and provide additional education as needed. Utilize the “teach-back” method to review the bridging chart and ensure thorough understanding.4,5
- make sure the patient is scheduled for follow-up post-op care as directed, including lab work to monitor INR levels, and reinforce the importance of keeping these appointments.
1. Lovenox (enoxaparin sodium injection) for subcutaneous and intravenous use. Prescribing information.
2. Douketis JD, Spyropoulos AC, Spencer FA, et al Perioperative management of antithrombotic therapy: antithrombotic therapy and prevention of thrombosis. Chest
. 2012;141(2 suppl):e326S–e350S.
3. Doherty JU, Gluckman TJ, Hucker WJ, et al 2017 ACC expert consensus decision pathway for periprocedural management of anticoagulation in patients with nonvalvular atrial fibrillation: a report of the American College of Cardiology Clinical Expert Consensus Document Task Force. J Am Coll Cardiol
4. Douketis JD, Lip GYH. Perioperative management of patients receiving anticoagulants. UpToDate. 2018. http://www.uptodate.com