Management of Patients on Warfarin undergoing Surgery (1)

If DVT or PE <1 month ago (defer surgery if possible) or
Acute Arterial emboli(2) <1 month ago

Before Surgery:

• Withhold warfarin for 4 days prior to operation day. The aim is to allow INR to drop to <1.5 on day of surgery.
• Commence LMWH (e.g., enoxaparin 1 mg/kg BD) at treatment dose when INR <2. Last dose prior to surgery given in morning, the day BEFORE surgery, i.e., no LMWH for 24-36 hours prior to surgery.

or

• Commence IV unfractionated heparin when INR <2. Stop 6 hours prior to surgery.
• Test INR on day of surgery. If still ≥1.5 discuss with Surgeon and Anaesthetist.

After Surgery:

• Restart warfarin (patient's usual daily dosing) AND either IV unfractionated heparin or LMWH at treatment dose, commencing 12-24 hours after surgery. Discuss with Surgeon/ Anaesthetist prior to recommencing therapy.
• Continue with LMWH or unfractionated heparin until INR >2.

If DVT or PE >1 month ago or Acute Arterial emboli(2) >1 month ago

Before Surgery:

• Withhold warfarin for 4 days prior to operation day. The aim is to allow INR to drop to <1.5 on day of surgery.
• Commence on LMWH at prophylactic dose e.g., enoxaparin 40 mg subcut daily. Last dose given on the day BEFORE surgery.
• Test INR on day of surgery. If INR ≥1.5 discuss with Surgeon and Anaesthetist.

After Surgery:

• Continue with LMWH at prophylactic dose after procedure, preferably on day of surgery.
• Restart warfarin (patient's usual daily dosing) 12-24 hours after the surgery. Ensure therapy commenced only after discussion with Surgeon and/or Anaesthetist.
• Continue with LMWH until INR >2.

If in Atrial Fibrillation

Before Surgery:

• Withhold warfarin for 4 days prior to operation day. The aim is to allow INR to drop to <1.5 on day of surgery.
• Test INR on day of surgery. If INR ≥1.5 discuss with Surgeon and Anaesthetist.

After Surgery:

• Restart warfarin (patient's usual daily dose) preferably on evening of day of surgery. Ensure therapy is recommenced only after discussion with Surgeon and/or Anaesthetist.

Note: The INR is likely to be subtherapeutic for 5-7 days.

If Prosthetic Heart Valves

If uncertain about management before or after surgery, discuss with Cardiac Surgeon.

• Mechanical aortic valve only(3) inserted >6 months ago and no other additional risk factors:
  • Before Surgery: Thromboembolic risk is low, follow regimen as for atrial fibrillation.
  • After Surgery: Regimen as for atrial fibrillation
• Other valves, multiple valves, valve replacement <6 months ago or additional risk factors(4):
  • Before Surgery: Thromboembolic risk is high, follow regimen as for DVT/PE <1 month ago.
  • After Surgery: Regimen as for DVT/PE <1 month ago.

1. For emergency surgery in patients on warfarin therapy, an INR of <1.5 can usually be achieved by infusion of Prothrombinex-VF (50 unit/kg) and fresh frozen plasma 1 unit (approximately 300 mL) with IV vitamin K 5 mg. However, do not give vitamin K to a patient with a prosthetic valve without prior discussion with Cardiac Surgeon. (To arrange Prothrombinex-VF, complete the Blood Product Request QMR22B form with the required dose (50 units/kg). Write "Life-threatening bleed on warfarin" clearly on the form. Send in a Lamson tube to the Blood Bank or fax to Blood Bank (80159), then inform the New Zealand Blood Service doctor on call via phone (80310).)
2. With a history of arterial emboli, concurrent antiplatelet therapy is also an important part of the prevention of further episodes - cessation of any antiplatelet therapy as well as oral anticoagulants needs to be considered in light of the risk of bleeding versus emboli. Consult Cardiac Surgeon.
3. St Jude Medical Bileaflet aortic valve, CarboMedics Bileaflet aortic valve, Medtronic-Hall tilting disk aortic valve.
4. Risk factors: History of TIAs, CVA, systemic emboli, atrial fibrillation, severe LV systolic dysfunction, recurrent congestive heart failure, previous thromboembolism, hypercoagulable conditions.

Management of Patients on Dabigatran Undergoing Surgery

• Assess the risk of bleeding against the risk of thrombosis when considering discontinuing anticoagulation.
• For minor procedures, dabigatran may not need to be discontinued.
• If dabigatran does need to be stopped, it is important to plan ahead as there is no treatment available to immediately reverse dabigatran.
• For detailed information see the PHARMAC website Guidelines for testing and perioperative management of dabigatran.
• If further advice is required, contact the Haematologist on call.