Anticoagulants and Surgery Part II

An Anaesthetist’s Perspective

There is a process problem for community anticoagulated patients having procedures because of:

• increasing usage of anticoagulants in the community (warfarin at 9% p.a.)
• introduction of new anticoagulants (direct thrombin inhibitors and thienopyridines)
• changes in the imperative for their continuation
• use of over-the-counter antiplatelet drugs
• increased productivity through same day admission for procedures.

There is a risk that fragmentation of care and specialist silos result in problems with:

• timely identification of who is anticoagulated, with what and why
• whether and when to stop anticoagulation for a procedure
• whether to bridge with other therap
• when to reinstitute, and with what.

The judgement on this will require a detailed knowledge of:

• the indication for anticoagulation
• any comorbidities and treatments
• The details of the procedure and anaesthesia to be performed.

• be explicitly nominated for that role so everyone knows who is making the decisions
• remain up to date on the drugs and their indications and management
• communicate with all parties and be available to discuss the issues at odd times
• ensure patients understand and comply with directions.

Some surgeons and proceduralists are comfortable coordinating this but if not they should ensure someone else is nominated.

These duties cannot be reduced to an algorithm or guidelines due to the multiplicity of clinical scenarios; however the relevant guidelines are a building block that all physicians should be familiar with in order to avoid departure from accepted clinical standards.

Mixups over the handling of perioperative anticoagulation cause unnecessary productivity loss as well as distress for the patient when delays result.

Challenges faced by anaesthetists

Anaesthetic blocks

The use of spinal, epidural and ophthalmic regional local anaesthetic blocks in anticoagulated patients is relatively or absolutely contraindicated due to the risk of haematoma causing disastrous complications. However for many patients, this is a safe technique and a most accepted technique for anaesthesia, e.g. for an obese diabetic having foot surgery. If that patient has AF and is on warfarin, are they better off continuing the anticoagulant and having a GA, or ceasing it and having a spinal block? That decision should be made after discussion with both the physician who understands the risk of stroke in that patient, and the patient themselves.

Bleeding

Significant bleeding can itself cause coagulopathy which can be challenging to manage even without anticoagulants complicating the picture. The location of the bleeding is
also relevant – in the retina or the brain or spinal column the consequences can be severe from small quantities. Occult bleeding, for example inside the GI tract after polypectomy, can be a disaster due to delayed diagnosis and the day procedure nature of the service. Management of difficult airways is more complicated if bleeding occurs during instrumentation of the nose or throat. Ear, nose and throat or airway surgery can be difficult to perform at all if brisk bleeding occurs during the procedure, thus frustrating the entire enterprise.

Emergency surgery

Emergency surgery, particularly for trauma and multi-trauma or to treat complications of overdose of anticoagulant (e.g. leading to extradural haematoma) may require reversal of vitamin K antagonist drugs and careful management of the replacement of blood products.

Patients particularly sensitive to blood loss, such as those with severe cardiac or respiratory comorbidity, and seriously ill patients, pose additional challenges, often out of hours when advice is harder to access.

Conclusion

The challenge is not only to know what should be done, but to make sure it actually happens at the right time, every time, year in and year out in a busy practice where you need to:

• identify who is anticoagulated, with what and why
• whether and when to stop anticoagulation for a procedure
• whether to bridge with other therapy
• when to reinstitute, and with what.

By Dr Andrew Miller
MBBS LLB(Hons) FANZCA FACLM

A Surgeon’s Perspective

The perioperative management of the anitcoagulated patient is an exercise in balancing the risks of bleeding versus the risk of thrombosis. Exactly quantifying
these risks in an individual patient though can be highly problematic and few randomised controlled trials exist to justify particular regimens. Furthermore, surgeons often feel that physicians don’t understand the risks and consequences of bleeding and physicians feel that surgeons don’t understand the risks and consequences of thrombosis.

What is the risk of thrombosis?

It is important to understand that thromboembolic risk varies significantly with patients and, in the case of mechanical valve replacement, device related factors. Table 1 ¹ summarises those at highest risk.

What is the consequence of thrombosis?

Embolic stroke can result in major disability or death in 70% of patients; thrombosis of a coronary valve is fatal in 15% of patients. Perioperative myocardial ischaemia increases mortality by two to four times.

The use of dual antiplatelet agents (aspirin and a thienopyridine – clopidogrel or ticlopidine) in patients with coronary stents creates frustration for cardiologists and surgeons alike. The message for surgeons is that indiscriminant cessation of antiplatelet agents in patients who have undergone recent coronary stenting (6 weeks for a bare metal stent and 12 months for a drug-eluting stent [DES]) very significantly risk coronary occlusion (up to 29% of DES patients). In the majority of cases, stent thrombosis will result in myocardial infarction and a 25-40% mortality rate. Conversely, the message for cardiologists should be to not go placing stents without thought as to imminent surgical requirements that might be safely achievable before the patient is committed to a period of mandatory anticoagulation.

Surgeons: listen to your physicians. Negotiate a plan of management with regard to perioperative anticoagulation long before the patient is admitted. Don’t stop anticoagulation without reference. Stay abreast of anticoagulant drug therapy (including the newer oral agents like rivaroxaban and dabigatran). Where possible, avoid discontinuing aspirin therapy. The use of aspirin in the perioperative period increases risk of bleeding by only a minor degree (by a factor of 1.5 times in a meta-analysis of 474 trials) but reduces the risk of major cardiac events by 80%.

What is the risk of bleeding?

Physicians: listen to your surgeons. Don’t commence anticoagulation in the perioperative period without careful discussion regarding the risks of bleeding: the clinical consequences may range from annoying to catastrophic. Furthermore, postoperative bleeding will delay recommencement of anticoagulation, further increasing the risk of thromboembolism. Particular procedures associated with a high risk of bleeding include coronary bypass surgery, heart-valve replacement surgery, intracranial and spinal surgery, aortic aneurysm repair, peripheral bypass vascular surgery, major orthopaedic procedures, reconstructive plastic surgery and prostate and bladder surgery.

It may not be all or none

Interruption of anticoagulation is not required for all surgical procedures. For example, minor dermatologic procedures, dental extractions and even cataract surgery can generally be safely performed in the warfarinised patient.

In those patients at significant risk off anticoagulant therapy the the use of bridging anticoagulation using a short-acting anticoagulant (such as heparin) allows anticoagulation
to be continued right up to just before the time of surgical intervention and recommenced as soon as haemostasis has been safely achieved afterwards, thereby minimising the time off treatment. Where temporary cessation of anticoagulation is deemed surgically necessary and the risk of VTE is unacceptably high, then placement of an inferior vena cava filter can be considered.

Conclusion

Navigating the issues surrounding perioperative anticoagulation begins and ends with dialogue. Individualize patient management. Don’t act without consultation.

By Dr Robert Davies
MBBS, FRACS

• 1 Douketis JD, Berger PB, Dunn AJ et al. The perioperative management of antithrombotic therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest 2008;
  133 (6 Suppl): 299S – 339S.↑
• 2 National Blood Authority. Patient Blood Management Guidelines: Module 2 Perioperative. 2012. ↑
• 3 Baker R, Coughlin PB, Gallus AS, Harper PL, Salem HH, Wood EM, the Warfarin Reversal Consensus Group. Warfarin reversal: consensus guidelines, on behalf of the Australasian Society of Thrombosis and Haemostasis. Med J Aust 2004;181(9):492-7.↑