Anticoagulants and Surgery Part I

The peri-operative management of anticoagulation can be complex. This article highlights some of the challenges of managing anticoagulated patients who are undergoing surgery from the perspective of a GP and a physician.

Part II of this article – which we will publish in the next edition of Defence Update – will discuss the issue from a surgeon’s and an anaesthetist’s point of view.

MDA National frequently receives notifications from Members about complications involving patients taking anticoagulant drugs who undergo surgical procedures. Some recent incident reports include:

Case One

A 58 year old patient underwent a total knee replacement. She was on warfarin because of an underlying thrombophilic disorder and a patent foramen ovale. The surgeon recommenced warfarin on the first post-operative day. The patient developed a large haemarthrosis which was managed conservatively with pressure bandaging. She subsequently developed a peroneal nerve palsy which was thought to be secondary to the pressure from the haematoma and bandaging.

Case Two

A 70 year old patient was booked for cataract surgery. She was on warfarin because of atrial fibrillation, which was then ceased pre-operatively. The cataract surgery was uneventful but the patient suffered a large stroke two days post-operatively.

Case Three

A 55 year old patient was commenced on clopidogrel following coronary stenting five years earlier. He was booked for elective surgery and stopped the clopidogrel 10 days pre-operatively. The patient suffered an intra-operative myocardial infarction and was unable to be resuscitated. Autopsy revealed blockage of his coronary stent.

Case Four

A 63 year old patient underwent a colonoscopy. His regular medications included aspirin and clopidogrel. A number of biopsies were performed during the colonoscopy. Nine days post-procedure the patient suffered a major gastrointestinal bleed.

A GP’s perspective

A/Prof Moira Sim

Warfarin is highly effective in reducing morbidity and mortality relating to arterial and venous thrombosis.¹ Despite the risk of serious bleeding (between 1.2-8.1% of patients on long-term warfarin anticoagulation treatment) its use is common and increasing in the community.²

While patients on warfarin are often older, studies support the use of anticoagulation with increasing age.¹ With age comes increasing comorbidities including indications for surgery, for which warfarin is usually a contraindication.³

There is a need to make decisions on the cessation of warfarin prior to the surgery. As with all decisions there are benefits and risks. Who makes the decision on whether and when to stop warfarin? Should it be the GP, the surgeon, the anaesthetist or someone else?

Patients need advice which is consistent and this therefore means that decisions have to not only be well communicated to the patient, but they need to be communicated along the continuum of care. The patient needs to understand the plan early so uncertainty about anticoagulation does not become a reason for increased anxiety at the time of surgery, and the patient is not sent home after attending for admission because the INR is too high for surgery to be considered.

GPs are the coordinators of patient care and, in most cases, will have information about the rationale for the commencement of warfarin and understanding of the planned duration. Occasionally this information is not easily available to the GP, who may have recently taken over care, or may not have access to previous records. However, this is usually easily remedied as GPs can seek the information and review the rationale for the use of warfarin, including consultation with the physician who may have been involved in the decision to commence or continue warfarin. With this information GPs can assess the risk of cessation of warfarin.

However, surgical and anaesthetic methods have continued to change and most GPs are unlikely to know the contemporary surgical processes such as the surgical approach, the preferences of the surgeon, or whether reversal of warfarin or other strategies to manage bleeding are used by the anaesthetist. Without this understanding of the contemporary procedures in the operating room, GPs cannot necessarily assess the risk of continued warfarin or advise the patient on this risk. It would be useful for the GP to know the INR level above which the surgeon considers surgery to be too risky.

Ultimately this is an issue which requires good communication from:

• the GP who should inform the surgeon of the use and rationale of warfarin
• the surgeon who should inform the GP of the risks and requirements of surgery in relation to warfarin, and communicate with the anaesthetist who will need to be prepared for complications relating to coagulation
• all health professionals involved in the continuum of care, so that consistent advice is provided to the patient about warfarin.

Beyond warfarin there are now the new direct thrombin inhibitors such as dabigatran which, unlike warfarin, cannot be reversed with vitamin K. Patients may also be on the antiplatelet treatment, clopidogrel, premature cessation of which is associated with intracoronary stent thrombosis. Communication between treating doctors to assess the risks and benefits of surgery and cessation of anticoagulation is critical in providing optimal patient outcomes.

A physician’s perspective

A/Prof David O Watson

The management of anticoagulant and antiplatelet therapy is particularly the province of general practice. Usually, it is not the GP who initiates these therapies. In the context of a patient undergoing surgery or any other procedure it is usually the decision of the proceduralist, with the GP being advised sometime later. Herein lies one of the great problems of patient management and a potential source of difficulty.

Anticoagulants

For the most part this is warfarin.

In patients with atrial fibrillation, there’s generally little difficulty. Warfarin can be withdrawn about five days ahead of the procedure and provided the INR is below 1.5, most would consider it safe to proceed.

Warfarin can be recommenced post-procedure at a suitable time that will depend on the nature of what has been done. Frequently, as there is no hurry to return the patient to a therapeutic INR, the warfarin re-start might be done without a loading dose. Where appropriate, the patient should be covered with a prophylactic dose of a heparin preparation.

Patients with prosthetic heart valves need additional consideration of how to protect the valve from thrombosis with the patient off warfarin. Patients with deep venous thrombosis and/or pulmonary embolism (VTE) require individual decisions about warfarin withdrawal and appropriate cover depending on:

- the nature of the VTE problem

- the procedure

- whether there is a recognised thrombophilic state (especially anti-thrombin factor III deficiency).

Rarely, there may be procedures where no withdrawal of warfarin is seen as necessary by the proceduralist.

It is good practice for the proceduralist to consult with the patient’s GP and/or cardiologist or physician, so the decision on how to manage the process and anticoagulants is a joint one.

Antiplatelet drugs

Most frequently this issue crops up with coronary artery stents. Again management will be influenced by:

• the planned procedure
• the nature of the stents in situ
• when the stents were put in place.

Here, the proceduralist will have a view as to whether antiplatelet therapy needs to be withdrawn but in any event; best practice would suggest there is contact with the patient’s cardiologist to establish the plan of management. Again, the patient’s GP needs to be in the decision loop.

Newer anticoagulants

There has been much interest in the arrival of newer agents like dabigatran and rivaroxaban as replacements for warfarin. The biggest single problem that will emerge with these drugs centres on the reality that they are difficult to reverse. This will have an impact only in the emergency situation for procedures. There will routinely still need to be a conversation between proceduralist, the patient’s GP and the individual who initiated the use of the drug to establish the plan of management around the procedure.

Summary

The issues are complex. There is an essential need for good communication between proceduralist, patient, the patient’s GP and any specialist involved in the care around the indication for, and use of, anticoagulant or antiplatelet drugs to establish the safest environment around the proposed procedure.