To provide an approach to the perioperative management of warfarin-treated patients who require an elective or urgent surgery/procedure. - To provide an approach for bridging anticoagulation, if needed, during warfarin interruption. For guidance on management of patients who require an urgent or emergency surgery/procedure, please refer to the Perioperative Anticoagulant Management Algorithm found on the Thrombosis Canada website under the "Tools" tab.Bridging anticoagulation refers to giving a short-acting anticoagulant, typically a low molecular weight heparin (LWMH), before and after surgery or invasive procedure to minimize the time that warfarintreated patients are not anticoagulated. This is different from providing routine thromboprophylaxis in the post-operative setting.# BRIDGING ANTICOAGULATION OPTIONS:
Pre-and post-operative dosing:
- Subcutaneous (SC) therapeutic-dose LMWH: enoxaparin 1 mg/kg twice daily or 1.5 mg/kg once daily, dalteparin 100 IU/kg twice daily or 200 IU/kg once daily, or tinzaparin 175 IU/kg once daily. - Intravenous (IV) unfractionated heparin (UFH) to achieve a therapeutic activated partial thromboplastin time (aPTT) defined according to local laboratory parameters is not commonly used.
Alternative post-operative dosing:
- In patients having a high-bleed-risk surgery/procedure, an alternate post-operative management option should be considered with a prophylactic dose of SC LMWH: enoxaparin 40 mg once daily, dalteparin 5000 IU once daily or tinzaparin 4500 IU once daily. - In patients having a high-bleed-risk surgery/procedure that is cardiac, spinal or intracranial, postoperative therapeutic-dose LMWH bridging should be avoided; alternate options are low-dose prophylactic LMWH, delaying anticoagulation until the bleed risk decreases or resuming warfarin alone.

# MONITORING:
There is no need for laboratory monitoring with SC LMWH bridging. Monitoring of the aPTT is required for bridging with IV UFH.

# ADVERSE EFFECTS:
Bridging is associated with a 2% increase in risk for major bleeding and a 10-15% risk for minor bleeding. Bridging should be used carefully to minimize this bleeding risk.

# PERI-PROCEDURE MANAGEMENT QUESTIONS AND ANSWERS:
Is peri-procedure warfarin interruption always needed? Deciding if warfarin interruption is needed is based on the bleeding risk of the surgery/procedure (see Table 1). Most surgeries/procedures require warfarin interruption but, in general, minimal-bleed-risk procedures (e.g. dental, cataract surgery, minor skin procedures) do not need warfarin interruption.  - Chronic atrial fibrillation with a CHADS2 score- of 3-4 - Newer generation (bileaflet) mechanical aortic valve - Prior arterial or venous thromboembolism within last 3-12 months

# LOW-RISK (BRIDGING ANTICOAGULATION IS NOT RECOMMENDED):
- Chronic atrial fibrillation (valvular or non-valvular) with a CHADS2 score- of 0-2 - Prior venous thromboembolism over 12 months ago - Bioprosthetic heart valve *CHADS2 score estimates the risk of stroke in patients with non-valvular atrial fibrillation. The score is the total points for the presence of congestive heart failure (1), hypertension (1), age > 75 yrs (1), diabetes (1), stroke, transient ischemic attack or systemic embolism (2). Consider a temporary inferior vena cava filter to be inserted after warfarin interruption and prior to surgery for patients in whom surgery is necessary within 1 month of a proximal DVT; filter can be left in situ for 1-2 weeks until therapeutic anticoagulation is re-established. Elective surgery within 3 months after a diagnosis of deep vein thrombosis or pulmonary embolism should generally be avoided.

# What is the perioperative anticoagulant management after warfarin interruption for elective procedures?
A suggested management algorithm is shown in the Figure below.

# FIGURE 1. PERIOPERATIVE MANAGEMENT OF WARFARIN-TREATED PATIENTS BEFORE AND AFTER SURGERY/PROCEDURE
When is it safe to resume bridging anticoagulation after surgery/procedure?
The timing of post-procedure resumption of bridging depends on: a) the bleeding risk of the procedure (see Table 1), b) whether there has been adequate post-operative hemostasis (based on wound inspection and drainage tubes to detect bleeding), and c) the class of anticoagulant used.
Minimizing bleeding is important because of associated morbidity; a delay in warfarin resumption because of bleeding also exposes patients to an increased thromboembolic risk.

# Is interruption of anticoagulation needed?
Continue anticoagulation: see Table 1  Stop warfarin 5 days before procedure and check INR day -1 to ensure 1.5 or less. If INR >1.5 administer vitamin K1 1-2 mg orally. Use therapeutic LMWH ~3 days before surgery. Last preoperative dose 24 h before surgery (1/2 of daily). Resume therapeutic dose LMWH according to bleeding risk as outlined in Table 3 after surgery. Resume warfarin postoperatively when patient drinking fluids, consider bolus dose.

# Yes TABLE 3. POST-OPERATIVE RESUMPTION OF BRIDGING ANTICOAGULATION
Resumption of therapeutic doses of any anticoagulant should not occur earlier than the time periods suggested below.

# LOW/MODERATE-BLEED-RISK PROCEDURE:
- Therapeutic-dose LMWH/UFH, starting approximately 24 hours after surgery (i.e. day after surgery)

# HIGH-BLEED-RISK PROCEDURE:
- Therapeutic-dose LMWH/UFH, starting 48-72 hours after surgery - Alternate management: prophylactic LMWH, starting 12-24 hours after surgery (i.e. day after surgery) or resume warfarin alone with no post-operative LMWH/UFH

# SPECIAL CONSIDERATIONS:
Dental procedures: In patients having 1-2 dental extractions or endodontic (root canal) procedures, warfarin can be safely continued. To reduce the incidence of gingival bleeding, patients can take oral tranexamic acid mouthwash (5 mL just before the procedure, and 2-3 times daily after the procedure until bleeding subsides).

# Eye procedures:
In patients having a cataract extraction, especially if done with topical and not retrobulbar anesthesia, warfarin can be safely continued. For other eye procedures, warfarin is generally interrupted but consultation with an ophthalmologist is advised.
Colonoscopy & gastroscopy: Warfarin interruption will be needed for most patients who undergo colonoscopy because the potential for polyp removal cannot always be determined beforehand. Caution is warranted after removal of large (>1 cm) polyps since bleeding can occur 2-7 days after polypectomy due to dislodgement of eschar. Polyp-related bleeding may be reduced with endoscopic application of clips to the polyp stalk. 
OTHER RELEVANT THROMBOSIS CANADA CLINICAL GUIDES:
- Unfractionated Heparin, Low Molecular Weight Heparin and Fondaparinux - Warfarin

# Date of version: 04Sept2021
Please note that the information contained herein is not to be interpreted as an alternative to medical advice from your doctor or other professional healthcare provider. If you have any specific questions about any medical matter, you should consult your doctor or other professional healthcare providers, and as such you should never delay seeking medical advice, disregard medical advice or discontinue medical treatment because of the information contained herein.