Peri-operative management of anticoagulation (blood thinning)

Why is peri-operative management of blood thinning important?

Patients who are on blood thinning medication may require the blood thinning to be stopped around the time of surgery. This is to make sure that the bleeding risks during surgery are minimized. At the same time, it is also important to ensure patients who require blood thinning are not placed at any major risk of blood clots.

How long will I need to stop my blood thinning for?

This will depend on the condition for which you are being treated with blood thinning medication – most people are on a medication called warfarin.

Generally, patients on warfarin should stop the warfarin 5 days before the operation. This will make sure that the effect of warfarin decreases prior to surgery and the risk of bleeding are reduced.

Do I need any blood tests to monitor my warfarin level?

This will depend on the reason for which you are on warfarin – an INR should be performed 3 days after stopping the warfarin. If you INR is low at this time (generally less than 1.5) you may need another form of blood thinning prior to the surgery.

This other form of blood thinning is called Clexane. Clexane is given by an injection under the skin once per day. Clexane can be used as "bridging" blood thinning (i.e. can be used to make sure your blood is thin enough to prevent blood thinning prior to the surgery but avoid you having an increased risk of blood clots if your warfarin level is too low).

When should I stop the Clexane?

The effect of clexane is shorter that warfarin – it needs to stop 24 hours prior to the surgery.

  • Your last dose of Clexane should be on the morning before your day of surgery.

Do I need to do anything else?

Depending on the type of surgery and the reason for which you are on blood thinning, you may need to be admitted on night prior to your surgery – you may even need another form of blood thinning medication to "cover" the risk of blood clots right up until the time of surgery. This medication is called Heparin and is given straight into the blood circulation byan infusion.


  • Stop warfarin 5 days prior to surgery
  • Have an INR 2 days after stopping the wafarin
  • You may need to start Clexane injections if your warfarin level is low (<1.5)
  • Your last dose of Clexane should be on the morning before your day of surgery.
  • This dose should be half of your normal daily dose.


The information presented in this fact sheet is intended as a general guide only. Patients should seek further advice and information about Peri-operative management of anticoagulation and or their individual condition from their treating haematologist or doctor.

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