Anticoagulants and surgery


In this blog I am going to discuss how anaesthetists manage patients who are already on anticoagulants. There is another blog on my website about using anticoagulants after operations to prevent deep vein thrombosis and other clotting problems


Patients who are on anticoagulants or blood thinners will not form clots and are more likely to bleed. For many operations this increases risk. However other operations can safely be performed on anticoagulants and it is always the surgeon’s decision whether anticoagulants constitute a risk.


My surgeons will discuss with me whether they want the anticoagulants stopped for the operation. If we stop anticoagulants – either warfarin or the newer anticoagulants such as dabigatran – it can take several days for the clotting to return to normal. If the anticoagulant is being given for a low risk situation such as atrial fibrillation we normally stop the anticoagulant for a few days and in the case of warfarin check the clotting has returned to normal.


If the anticoagulant is important for example if a patient is being treated for an existing clot, we should not leave the patient except for the period of surgery. We therefore start the patient on an injection of daily heparin which maintains anticoagulation. The heparin is then stopped 24 hours before surgery. The clotting will return to normal during that time, but if there is still poor clotting we can give an antidote called protamine. Protamine only works against heparin, not the other anticoagulants.


After the operation we need to decide when to restart anticoagulation. If there is a risk of bleeding from the surgery we keep patients on heparin which can be reversed. The oral anticoagulants are then restarted and in the case of warfarin blood tests are used to adjust the dose. Patients at low risk can simply restart their warfarin or dabigatran whereas high risk patients will need to remain on heparin until the oral anticoagulant has taken effect