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Pharmacology

How Do I Manage A Patient Who Is On Anticoagulants?

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Mark DonaldsonWe are very pleased to present this series of videos by Dr. Mark Donaldson, Director of Pharmacy Services at the Kalispell Regional Medical Center and faculty member at the University of Montana and the Oregon Health & Sciences University

There is no such thing as medical clearance. In fact, the dentist retains the primary responsibility for the procedures carried out for the immediate management of many untoward complications. While it is always prudent to get a consult with a medical practitioner, such as the patient’s primary prescriber or cardiologist, at the end of the day, the onus is on the dentist to keep up with the medical and dental literature and to make the appropriate decisions.

In the second part, we look at the science of clotting. What is the clinician’s view of haemostasis? As a quick review, if we go below the gum line and we do some type of dental surgery causing tissue injury, the body responds by activating platelets which travel to that area to cause healing or the platelet plug in that area.

In the third part, practical dental management of patients on anticoagulants is discussed. The challenge as practitioners we have is whether or not we want to stop the warfarin or not stop the warfarin preoperatively?

 

Follow-up: What further information would you like on this topic? Email us at jcdaoasis@cda-adc.ca

Readers are invited to comment on this initial response and provide further insights by posting in the comment box which you will find by clicking on “Leave a reply“ below. You are welcome to remain anonymous and your email address will not be posted .

 

 

7 Comments

  1. Sarah Johnston March 12, 2013

    You had mentioned that with the newer anticoagulants (Dabigatran for e.g) that you would stop 24 hours prior to a surgical dental procedure. However, this would not be the case for warfarin, due to the risk for cardiac events. Why is it OK to stop the newer meds for 24 hours prior and after and not OK for warfarin?

    Reply
    1. Mark Donaldson March 13, 2013

      Thank you very much for your excellent question. The answer has to do with both mechanism of action and pharmacokinetics; in particular half-life.

      Warfarin inhibits the vitamin K-dependent clotting factors II, VII, IX and X. Because of this non-specific interaction, it is difficult to assign a true half-life to warfarin and instead we use the half-life of the longest acting clotting factor as a surrogate. In this case, factor II has a half-life of about 40 hours, so the half-life of warfarin is probably close to this. When we are thinking about the potential side effects of warfarin therapy in our patients (i.e., bleeding) we are then equating this half-life to clinical response; in other words, the effects of warfarin if you were to give a single dose last for at least 40 hours in the body.

      Why do we not stop warfarin prior to surgery? Because of this non-specific action, relatively long half-life, drug- and dietary-interactions and interpatient variability we cannot be sure that stopping the drug 24 hours ahead of surgery will be effective in mitigating bleeding risk in all patients. Maybe it should be 48 hours or 72 hours prior. More importantly, what is the risk versus benefit? If we cannot definitively determine when to stop the drug (and consequently, when to restart the medication), are we safer to simply keep patients on the drug (in which case 1% of patients may not achieve good hemostasis postoperatively) or should we consider interrupting the therapy (in which case about 1% of patients could suffer a venous-thrombolic event (VTE) such as a stroke or heart attack). We have great strategies and medicines to manage the 1% of patients who do not get good hemostasis initially; we cannot reverse the 1% who may face mortality.

      In contrast to warfarin, the newer agents that are mentioned (dabigatran, rivaroxaban and apixaban) all have specific mechanisms of action (they target just one clotting factor), and they all have short half-lives (less than 12 hours). For these reasons we can safely stop and start the medications without putting our patients at risk of becoming too under-anticoagulated or too over-anticoagulated. These points are definitely easier to emphasize graphically, but I think my statements are clear.

      Finally, you bring up an excellent idea for a fourth video in this section and that would be the concept of, “bridge therapy.” There are certainly some labile cardiac patients who need to be effectively anticoagulated at all times, but for whom their warfarin puts them into a high risk category for bleeding when they require some type of surgical intervention. In these patients we can transition them to a low molecular weight heparin (LMWH) such as enoxaparin around their surgical procedure and once their surgery is complete they can be transitioned back to their warfarin.

      Thank you for the suggestion! I will work toward compiling this information too. Best regards,

      Mark

  2. anton james March 13, 2013

    thanks for this informative series .
    Do you not feel as an inter professional courtesy , the physician prescribing the anti-coagulants should always be consulted ?.. In joint consultation , a decision is thence made . As a dentist, I often lean towards accepting my responsibility to deal with a case of prolonged bleeding , versus exposing the patient to a thrombo-embolitic event . I also would consider the extent of the tissue trauma expected . Am I off-track in my thinking ?

    Reply
    1. Mark Donaldson March 13, 2013

      You are definitely on the right track, however, the scenario you describe may be more idyllic than reality. It would certainly be ideal if you could consult directly with the patients’ cardiologist or primary prescriber in order to come up with the best combined plan for the patient. It would also be ideal if all parties were up to date on current guidelines and medications such that an informed decision is made each and every time. And finally, it would most ideal if all of the above happened in a timely manner to facilitate efficient care. Unfortunately, this is not everyone’s reality.

      We each have busy lives and busy practices. When you call a physician’s office you seldom get to speak to the physician directly for that peer-to-peer consult in order to come up with a sound strategy for the patient in your chair. Furthermore, if you are able to reach the physician directly, it is not always on that initial call, but rather when they have time to call you back; at which point your patient may already be gone. I do suggest a simple pre-printed fax-back form asking that the physician review the short summary you provide and then to either write a response or simply check one of the options you may recommend that they then sign and fax back to you. This could facilitate a quick curb-side consult that minimizes the impact on the physician’s day, however, this strategy is not always successful either.

      For all of these reasons, I agree with you that it is a professional courtesy, and we do try to make the attempt at a direct consultation, however, given the barriers illustrated above, the dentist is often left with the patient in the chair who requires care, and without a medical consult to help direct treatment. “The dentist retains the primary responsibility for the procedures carried out for the immediate management of many untoward complications.”

      Thank you again for your question,

      Mark

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    Reply
  4. Anders Nattestad March 22, 2013

    Mark,

    Could you address the ethical dilemma of a patient on warfarin either themselves or by their doctor (not familiar with the current science and practice) stopping coumadin several days before a surgical procedure. The patient is in the chair and the INR is lets say 0.9. Do you abort the procedure and send the patient home to take their medication or do you proceed now that the wrong decision has been made? Obviously we would instruct the patient/doctor to follow the guidelines you covered next time.

    Reply
    1. Mark Donaldson March 25, 2013

      Thank you for your question. I will have to first start with the disclaimer that I am not an expert in ethics, but I certainly feel experienced enough with the situation you describe to make a knowledgeable comment.

      If a patient is on coumadin to prevent some type of venousthromboembolic event (VTE), then they need to have their INR in a particular range so that they are protected from such an event occurring (typically 2.0-3.0 or 2.5-3.5 if they have a mechanical valve in situ). If they (or their physician) decide to stop the coumadin several days ahead of a dental appointment in order to mitigate the potential for poor post-operative hemostasis, and they fall below their target INR range that is keeping them “safe” (i.e., 0.9), I believe you should abort the appointment.

      While I am not a legal expert, if you have knowledge of the above situation and you proceed with the appointment, in a court of law this would be exceedingly difficult to defend if the patient goes on to suffer some type of event such as transischemic attack, pulmonary embolus, myocardial infarction, stroke or even worse, death. As crass as it may seem, the legal experts have access to the same guidelines that I have presented, and to which you also have access, so practicing outside the standard of care would be ill advised.

      If I were to play the devil’s advocate in this scenario, and the patients’ physician has documented evidence that they advised the patient to stop the coumadin several days ahead of the dental appointment, you may be somewhat insulated from any legal fallout were there to be an untoward event. However, I still agree with Dr. Burket’s statement that, “There is no such thing as medical clearance. In fact, the dentist retains the primary responsibility for the procedures carried out for the immediate management of many untoward complications.” If you know what the guidelines state, yet provide treatment to a patient whose physician may not be aware of the current guidelines, it is you who are putting the patient at risk. After all, the oath that we took upon graduation was to, “first, do no harm.”

      Thank you again for your excellent question.

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