Many of you have had a deep vein thrombosis (DVT) or pulmonary embolus (PE) or know somebody who has been affected by these conditions. Some of you will have had a short course of treatment, but if you have had more than one clot, you will likely stay on long-term treatment. Currently, most people with a DVT or PE are treated with newer drugs such as dabigatran, rivaroxaban or apixaban, but many have found warfarin the best option.
But what happens if you need surgery? Most people are concerned that they have an increased risk of bleeding if they keep taking their treatment and an increased risk of a blood clot if they stop. How do we decide what is the safest way to manage surgery?
If you are going for surgery, you must talk to your surgeon and the anaesthetist at least a week before your operation.
If you are going for a major operation, you will usually have a chance to talk about your anticoagulants at the preoperative anaesthetic clinic.
Who is at risk?
The most important consideration when assessing somebody who has had a DVT or PE, is to know when they last had a clot. If you had a blood clot less than 3 months ago you have a high risk of another clot if your treatment is stopped. The risk gradually gets less over time. If you need surgery less than 3 months after your most recent clot, your surgeon should consider delaying the surgery. After 3 months, surgery is generally safe, but some surgeons like to wait 6 months after a clot before operating.
If your surgery cannot be delayed and you are taking warfarin, you will need bridging* anticoagulation.
If it is more than 3 months since your most recent clot, you can safely stop warfarin around surgery.
Do some people have a very high risk?
Yes, there are some people with a very high risk of a blood clot if warfarin is stopped, even if their last clot was years ago. These are people with the following conditions
- Antithrombin deficiency
- Protein C deficiency
- Protein S deficiency
- Homozygous factor V leiden
- Antiphospholipid syndrome
These may sound like fairly obscure diagnoses, but if you have one of these disorders your doctor will have told you.
Note that heterozygous factor V Leiden (inherited from one parent) is not a major risk. Homozygous Factor V Leiden is where the condition is inherited from both parents and has a very high risk of thrombosis. This is a rare condition.
Some people don’t fit into a specific category. The assessment of your risk must be individualised. There may be other reasons why your doctor assesses you as high risk, so it is important that you discuss what treatment is safest for you before going for surgery.
This means you need to change to a short-acting anticoagulant for a few days around surgery. This is usually to a low molecular weight heparin; enoxaparin (Clexane) is used in New Zealand. I will discuss more details in a later post.