As part of a series of blog posts surrounding World Patient Safety Day 2022's theme of 'Medication Safety', Consultant Trauma & Orthopaedics Surgeon Mr Haroon Rehman discusses the management of anti-coagulants (“blood-thinning” medications) around the time of surgery.
The management of anti-coagulants (“blood-thinning” medications) around the time of surgery is extremely important. The most common reasons for patients to use these medications include atrial fibrillation (irregular heartbeat); acute coronary syndrome (previous heart attack); heart valve replacement; previous stroke; prothrombotic/hypercoagulation states (the body making more blood clots than it should) and periods of immobility.
There are many different types of anti-coagulant medication that work in slightly different ways. In general, anti-coagulants prevent the formation of a substance called thrombin, an enzyme which helps form the material for a clot. Anti-platelet medications also affect clotting by preventing platelets (clot forming cells) from adhering and becoming active.
All operations can increase the risk of blood clotting, and major operations on the abdomen, chest or large joints such as hip and knee are associated with a higher risk of thromboembolic events (harm from blot clots). Surgeons take great care to balance the risks of thromobemoblic events with the risk of major bleeding. Bleeding risk can manifest itself in a collection of blood inside the body (haematoma) or leaky wounds which fail to heal and can become infected. Bleeding risk is not only considered for the operation itself, but also the anaesthetic. Surgery from hip to foot can be done under spinal anaesthetic (injection into spine). The space around the spinal cord within the bony tunnel that protects it is relatively small. A small amount of bleeding caused by the spinal anaesthetic can therefore collect and compress the spinal cord, affecting its function in movement and sensation.
There are several factors that determine which strategy is best, including the reasons for taking the medication and the nature of the surgery itself. Therefore, patient-centred, patient-specific advice is offered prior to surgery. This advice may be offered at pre-assessment clinics for elective (planned) surgery. In complex cases where patients have multiple other illnesses, surgeons will give advice in consultation with vascular medicine, cardiology and anaesthesia.
Generally, anti-coagulants are stopped for a period prior to surgery. In emergency situations, surgeons may administer medications that reverse the effects of anti-coagulants. In some cases where the clotting risk is substantial, the anti-coagulant may be “bridged” leading into surgery. An example of this is stopping warfarin and starting heparin. Warfarin is often stopped 5 days before surgery in low to intermediate clotting risk, and is restarted 24-48 hours afterwards. Clotting is measured by a blood test known as an INR. Vitamin K can be given by injection into the veins/muscles or taken orally to help reverse the effects of warfarin. Another family of anticoagulants are the direct oral anticoagulants including dabigtran, apixaban, edoxaban and rivaroxaban. They generally do not require bridging or reversal on account of the short duration of effect (“half-life”). These drugs are often stopped 24-72 hours before surgery. Finally, anti-platelet medication is similarly stopped 5-7 days before surgery. Aspirin is often stopped 7-10 days before surgery but for some operations may not be stopped at all.
Patients should take advice from their surgical team, as polices vary between surgical specialties and hospitals.