Clinical Scenario

A 56‐year‐old male presents to you requesting extraction of his upper right first premolar (#14). The tooth is currently painful with a 2‐week history of periodic swelling and pus discharge.

Structured Learning

1. Why is this patient taking warfarin?
   • It is used as an anticoagulant for the prevention of thromboembolic events due to the patient’s history of pulmonary embolism and peripheral vascular disease
2. What specific questions should you ask the patient in relation to his warfarin medication?
   • Check the therapeutic/target INR
   • How, where and how often is the INR monitored – it may be undertaken at an anticoagulation clinic via a standard blood test/point of care device, or the patient may have his own machine for use at home (Figure 10.3.2)
     

     

     

   • Stability of INR results (related to how often the warfarin dose is adjusted/frequency of testing) – this can be determined from the INR record book that most patients have in their possession
   • Confirm when the last INR test was undertaken
     • Ideally this should be no more than 24 hours prior to an invasive dental procedure
     • If the patient has a stable INR profile, an INR test result no more than 72 hours prior to the procedure may be acceptable depending on local protocols

3. The patient informs you that he last had an INR test undertaken at his local anticoagulation clinic 1 day ago. The result was 4.3. How does this impact on your dental management?
   • As the INR was >4.0, elective dental treatment, namely extraction of the #14, should be delayed (Table 10.3.1)
   • The anticoagulation service already advised the patient to reduce his warfarin dose and arranged to retest the INR in 1 week
   • Liaise with the service to advise them that a dental extraction is planned and arrange a dental appointment within 24 hours of the planned repeat INR
   • Once the INR is <4.0, the patient can receive dental treatment in primary care without needing to stop or adjust warfarin dose
4. The patient asks if you can give him medication to reverse the effect of warfarin to allow extraction of the #14 on the same day. Is this possible?
   • Warfarin is reversible by vitamin K, but this is not commonly used in relation to dental treatment
   • It may be used if there is prolonged bleeding following an invasive procedure
   • Fresh frozen plasma and prothrombin complex concentrate have also been used for life‐threatening haemorrhages
5. Tooth #14 is painful and infected. It is not possible to drain the buccal swelling. What do you need to consider if you decide to prescribe antibiotics until you can extract the tooth?
   • Many antibiotics can interact with warfarin
   • They commonly inhibit warfarin metabolism, prolonging its action and raising the INR
   • Antibiotics in the same class have similar effects on INR (Table 10.3.2)
   • The effect is generally more pronounced in older patients and/or those with multiple medical comorbidities, such as this patient
   • Metronidazole should be avoided where possible
   • Consider empirical dose reduction of other antibiotics
   • If antibiotics are prescribed:
     • The patient should be advised of the risk of the INR being affected
     • The anticoagulation clinic should be contacted as more frequent INR testing may be required (INR can be affected within 2‐3 days, causing potentially severe bleeding risk)
6. The patient returns to you a week later for dental extraction of #14. He informs you that he decided to omit his warfarin dose the day before his dental appointment so that he would not bleed after the procedure. Why is this not advisable?
   

   Prior to dental procedure

   Check the international normalised ratio (INR), ideally no more than 24 h prior to an invasive dental procedure Checking no more than 72 h before is acceptable if the patient has a stable INR (i.e. patient does not require weekly monitoring and has not had any INR measurements above 4.0 in the last 2 months) If there is reason to believe a test result obtained 72 h prior to the dental procedure is not reflective of current level, INR should be retested within 24 h before dental procedure If extensive maxillofacial surgery is required, an approach of discontinuing warfarin and introducing heparin as a bridging agent may be used, owing to heparin’s rapid onset and short half‐life Warfarin is ceased and intravenous heparin instituted to allow INR to decrease to a level appropriate for surgery Warfarin is then reinstituted post surgery INR is checked on a daily basis until it is within therapeutic range, and heparin therapy discontinued once this has been achieved As this requires inpatient hospital management, significant social and financial costs, and interdisciplinary co‐operation, it is not an appropriate management protocol for less complicated surgery or low‐risk patients

   If INR is >4.0

   Delay elective dental treatment and inform the patient’s general medical practitioner or anticoagulation service if they are not already aware Refer to secondary care if urgent treatment is required Be aware that prescribing amoxicillin for the dental condition may affect the INR level; ideally the INR should be checked 24 h after starting the antibiotic Enquire if there have been any recent health or dietary changes that may have contributed to increased INR

   If INR is <4.0

   Treat without interrupting vitamin K antagonists Consider limiting initial treatment area (e.g. perform a single extraction or limit subgingival periodontal scaling to 3 teeth, then assess bleeding before continuing) For procedures with a higher risk of postoperative bleeding complications, consider staging treatment over separate visits Use local haemostatic measures to achieve haemostasis; actively consider suturing and packing, taking into account patient factors Consider tranexamic acid 5% mouthwash 10 mL for 2 min, 4 times daily for 2–5 days (utility of tranexamic acid as an additional haemostatic measure in warfarinised patients is controversial) Advise patient to take paracetamol, unless contraindicated, for pain relief rather than aspirin or other non‐steroidal anti‐inflammatory drugs Caution with prescription of metronidazole, erythromycin, broad‐spectrum antibiotics, sulfonamides, tetracycline and azole antifungals If prescribing more than a single dose of antibiotic, consider reviewing patients routinely at 2–3 days postoperatively to check INR, remembering that absence of bleeding does not rule out an elevated INR Be aware that presurgery fasting and problems eating due to multiple extractions may have an effect on INR

   • There is strong evidence of increased risk of serious thromboembolic complications, including death, in patients whose anticoagulant therapy is interrupted
   • This risk is significantly higher than the risk of bleeding complications in patients whose anticoagulant therapy is continued
   • The overwhelming majority of patients taking warfarin before and after extractions whose INR is <4.0 at time of extraction do not have clinically significant bleeding postoperatively that requires more than local haemostatic measures, and any increase in bleeding is manageable at home
7. What other factors do you need to consider in your risk assessment?
   • Social
     • Reduced mobility
     • Wheelchair accessibility to/within dental clinic
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