Peri-Operative Management of Warfarin Patients

 

 

The Australasian Society of Thrombosis and Haemostasis have recently published guidelines on the reversal of anticoagulation in patients on long term warfarin. These guidelines include the peri-operative and peri-procedural management of warfarinised patients, and form the basis of these Clinical Board Guidelines.

 

General Comments on peri-operative warfarin management

 
  • In any individual patient it is important to consider the benefits vs risks of any approach.

 

  • Warfarin is a medication with a narrow therapeutic index. Stopping before an elective operation/procedure and restarting again is ideally done with close monitoring of the INR in a planned, organised way.

 

  • If a patient has a condition which requires long term Warfarin, then the patient and associated management must be discussed with the Anaesthetist.

 

  • If the therapeutic INR is in the range 2-3 it usually takes about 4 days for the INR to fall to 1.5 or less in most patients.

 

  • At INR < 1.5, most surgery and procedures can be safely performed. It is important to discuss the acceptable INR with the surgeon/proceduralist involved, as there is variation from case to case.

 

  • After restarting warfarin it usually takes 3 days for the INR to reach > 2.0

 

  • Not all patients on warfarin need Bridging Anticoagulation. Careful consideration is required to decide if a patient needs Bridging Anticoagulation with heparin (either Low Molecular Weight Heparin such as Enoxaparin/Clexane or IV heparin).

 

Differences in approach to anticoagulant management pre- and postoperatively relates to the fact that surgery is an important risk factor for venous, but not arterial thromboembolism.

 

 

Bleeding risk for operations and procedures for warfarinised patients

Procedures at low risk of bleeding in warfarinised patients

·        Simple dental/periodontal  work

·        Minor dermatological procedures

For such procedures, there is no need to stop or reverse anticoagulation, as the risk of bleeding is low, and if bleeding occurs it can be managed by local pressure.

 

Procedures at higher risk of bleeding in warfarinised patients

For non-minor procedures, anticoagulation will need to be reversed (see below for guide to doing this).

If there is a significant risk of thrombosis then bridging anticoagulation should be strongly considered.

Refer for the tables below as a guide to balancing these risks for your patient, and developing a management plan.

  

Risk of thrombosis or thromboembolism

 

Initial indication for anticoagulation

Patients are at relatively LOW risk of thrombosis if they have had:

Patients are at relatively HIGH risk of thrombosis if they have had:

Stroke prophylaxis due to Atrial Fibrillation

 

NO stroke/TIA in past month

Stroke/TIA in the past month

DVT/PE

 Index event (eg DVT/PE) requiring anticoagulation occurred >3 months ago

 Acute thrombosis (DVT) in past 3 months (consider caval filter if VTE within previous 2 weeks)

Mechanical heart valve

See table below

Lower risk valves-discuss management with cardiologist, some individuals need to be managed as HIGH risk.

Higher risk valves - manage as HIGH risk

 

  

 

Risk of thrombosis with mechanical heart valves

 

Lower risk mechanical valves

Higher risk mechanical valves

Lone Mechanical Aortic valve-Modern type (post-1990 in most cases)

Lone Mechanical Mitral valve- Modern type bileaflet or tilting valve and no previous embolic event

≥2 mechanical valves- e.g aortic and mitral OR mitral and tricuspid

Any older style mechanical valve in mitral, aortic or tricuspid position inserted pre-1990

 

PLUS all of the following:

 

·         Normal left ventricular function

·         No previous embolic event

·         Sinus Rhythm

Modern lone mechanical valve PLUS any of the following:

·         Impaired left ventricular function

·         Previous embolic event (esp < 3mths) relating to valve

·         Pro-embolic arrhythmia (eg atrial fibrillation)

 

 

Managing oral anticoagulation during invasive procedures according to

the risk of thrombosis or thromboembolism

 

Regional Anaesthesia

If regional anaesthesia (such as spinal or epidural anasthaesia) is planned for your patient, this must be discussed with the anaesthetist (go to ‘regional anaesthesia’).

           

Days before surgery

Low risk

no need to bridge

High risk

Bridging with LMWH (enoxaparin/Clexane)

(LMWH can be used for most patients and is more convenient than unfractionated heparin)

High risk

Bridging with unfractionated heparin

(use unfractionated heparin where significant bleeding risk exists)

4 days before surgery

 

Stop warfarin

Organise daily INR blood tests

 

Stop warfarin

Organise daily INR blood tests

 

Stop warfarin

Organise daily INR blood tests

 

3 & 2 days before surgery

 

No need to bridge with LMWH or heparin

 

Bridge with therapeutic dose LMWH when INR drops below 2

Stop LMWH 24h pre-op

 

Bridge with therapeutic dose IV heparin when INR drops below 2

 

Night before op

 

INR>2 given 1-5mg vit K

 

INR>2 given 1-5mg vit K

 

Stop heparin 4 h pre-op

 

INR>2 given 1-5mg vit K

 

 

Day of op

 

INR<1.5; operate

INR>1.5 give FFP or defer procedure

 

INR<1.5; operate

INR>1.5 give FFP or defer procedure

 

INR<1.5; operate

INR>1.5 give FFP or defer procedure

After surgery

Start usual maintenance dose warfarin on day of surgery

Consider thromboprophylaxis with 20mg or 40mg enoxaparin post op

Start thromboprophylactic dose (40mg) LMWH 12 to 24h post op once haemostasis is secured

 

When haemostasis is secured, start usual dose of warfarin on the evening after surgery

 

Stop LMWH when INR >2 for 48 hours

Start heparin 12 hours after major surgery aiming for APTT 1.5x patient’s normal (usually around 1000 units / hour) once haemostasis is secured.

 

When haemostasis is secured, start usual dose of warfarin on the evening after surgery

 

Check APTT 12 hours after restarting therapy

 

Stop IV heparin when INR >2 for 48 hours

 

 

 

 

Bridging anticoagulation-

Low Molecular Weight Heparin Vs Unfractionated Heparin

For most patients, LMWH (such as enoxaparin, or Clexane®) can be used as bridging anticoagulation, avoiding frequent APTT blood tests.

Unfractionated heparin can be used if there is a major risk of bleeding during the bridging period, as it has a shorter half life and is also easier to reverse.

 

Choosing the dose of enoxaparin (Clexane)   -  go to ‘using enoxaparin’

If renal function is normal, use full therapeutic dose (1mg/kg up to 100mg maximum dose, TWICE a day) once the INR drops below 2.0

If renal function is impaired (creatinine clearance <30ml/min) use reduced dose (1mg/kg up to 100mg, ONCE a day)

 

If there are any questions regarding bridging anticoagulation, discuss with the relevant expert…

·        Cardiologist

·        Haematologist

·        Surgeon

·        Physician

·        Anaesthetist

 

 

Re-starting Warfarin after the operation

Refer to table above for guide. If there is significant intraoperative bleeding or other complications, then discuss with Haematology or senior colleague.

 

 

 

 

Important:    If you have any queries about what to do, discuss with the Haematologist on call.

 

 

  

 

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