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Potentially invasive dental treatment in a primary care setting on patients who are on antithrombotic medication
IntroductionThe use of oral antithrombotic medication is increasing and the dentist is likely to encounter patients taking such medications on a routine basis. Dentists need to develop a method of assessing patients who receive anticoagulation therapy. Decision making should not be abrogated or delegated to the physician alone. Sometimes a physician’s decision to discontinue anticoagulation therapy before oral surgery is not based on sound clinical science, but rather the physician’s experiences relative to general surgery, orthopaedic surgery and so forth (Jeske & Suchko, 2003). Wahl (2003) described this as one of the factors contributing to the many myths associated with the dental treatment of patients receiving oral anticoagulation therapy.
Oral anticoagulant agentsThere are two major types of oral anticoagulant agents commonly prescribed for outpatients. The first and most widely used is the warfarin sodium Coumadin. The second major group of oral anticoagulant agents is antiplatelet agents which includes aspirin, clopidrogel bisulfate and ticlopidine. Warfarin blocks the formation of prothrombin and other clotting factors involved in both the extrinsic and common coagulation pathways, and it prevents the metabolism of vitamin K to its active form in the synthesis of these factors. Warfarin has a slow onset of action and a half-life of 36 hours. It is prescribed for those with prosthetic heart valves, deep venous thrombosis, myocardial infarction, stroke, atrial fibrillation or unstable angina (Hambleton & O’Reilly, 2000). Aspirin inhibits the formation of the prostaglandin thromboxane A2 within the platelet, thus affecting thrombus formation. Other antiplatelet agents such as clopidrogel act by inhibiting the binding of adenosine diphosphate to a platelet receptor that ordinarily mediates platelet aggregation. Antiplatelet drugs are used in the primary prevention of coronary thrombosis and secondary prevention of thromboembolic events in patients with a history of unstable angina, stroke and coronary thrombosis (Jeske & Suchko, 2003). Low-molecular-weight heparins or LMWHs, such as enoxaparin, dalteparin and ardeparin have a high bioavailability (95%) and can be self-administered by the patient. Because of the higher bioavailability of LMWH, continuous PT and INR testing is unnecessary as in the case of warfarin. These have replaced the old practise of “heparin windows” where a patient at higher risk of thromboembolism who needed maxillofacial surgery, was admitted 4 days before surgery, warfarin discontinued, unfractionated heparin administered in multiple doses with INR checking, surgery performed on fifth day and warfarin reinstated post-operatively (Jeske & Suchko, 2003). Patients with prosthetic heart valves requiring outpatient oral surgery are the only group of patients for whom LMWHs are not recommended (Webster & Wilde, 2000).
Potentially invasive procedures in primary care setting (Perry et al, 2007)Potentially invasive procedures performed in primary care would include: endodontics [root canal treatment beyond apex], local anaesthesia [infiltrations, inferior alveolar nerve block, mandibular blocks], extractions [single and multiple], minor oral surgery, periodontal surgery, biopsies, sub-gingival scaling.
Risk of bleeding in anti-coagulated patients undergoing oral surgeryMany of the early reports of haemorrhage associated with dental surgery predated the standardisation of oral anticoagulant control by means of the INR (Jeske & Suchko, 2003). In a study by Devani and colleagues (1998), no significant delayed bleeding was encountered in the vast majority of patients whose warfarin was not stopped prior to oral surgery. Local measures were instituted mainly surgicel packing. Devani et al (1998) concluded that due to the difficulty in predicting the drop in the INR value in any given patient, the risk of experiencing a thromboembolism outweighs the risk of experiencing excessive postoperative bleeding. Wahl’s (1998) review of 26 papers comprising 2,014 dental surgical procedures in 774 patients receiving continuous warfarin therapy (including patients with INR 4) showed
that 98% of patients had no serious bleeding problems. Similar results were obtained with patients on 100 milligrams of aspirin daily (Ardekian et al, 2000). In short, the risk of significant bleeding in patients on oral anticoagulants with a stable INR in the therapeutic range 2-4 is low. An appreciation of the surgical skills of primary care dentists and the difficulty of surgery, particularly when INR levels approach 4, is also important when assessing the risk of bleeding. Individuals in whom the INR is unstable should be discussed with their anticoagulation team (Perry et al, 2007).
The risk of thrombosis if anticoagulants are withdrawn The risk of thrombosis associated with temporarily discontinuing anticoagulants prior to dental surgery is small but potentially fatal (Perry et al, 2007). In the review of Wahl (1998) 5/493 (1%) patients undergoing 542 dental procedures and in whom anticoagulants were withdrawn specifically for surgery, had serious embolic complications of which four were fatal. Anticoagulants and prophylactic antibioticsPatients undergoing dental surgery on warfarin (with prosthetic heart valves) may be prescribed antibiotics to prevent endocarditis. A single dose of an antibiotic is unlikely to have any significant effect upon the INR. Recommendations by the British Guideline group (Perry et al, 2007) for patients stably anti-coagulated on warfarin (INR 2-4) and who are prescribed a single dose of antibiotics as prophylaxis against endocarditis, is that there is no necessity to alter the dose of anticoagulants.
Local haemostatic measures In patients undergoing dental extractions, bleeding may be minimised by the use of oxidised cellulose (Surgicel) or collagen sponges and sutures or with 5% tranexamic acid mouthwashes used four times a day for 2 days. Tranexamic acid is not readily available in the primary care dental setting (Perry et al, 2007).
When should the INR be measured before a dental procedure? In patients receiving long-term anticoagulant therapy and who are stably anti-coagulated on warfarin an INR check 72 hours prior to surgery is recommended. This allows sufficient time for dose modification if necessary to ensure a safe INR (2-4) on the day of dental surgery (Perry et al, 2007). INR should also be checked prior to receiving an inferior alveolar nerve block as there is anecdotal risk of haematoma and airway compromise. Anti-inflammatory drugs in patients receiving warfarin and undergoing dental surgeryNSAIDS are avoided because of their anti-platelet action and the risk of over-coagulation and haemorrhage. It may be safer to prescribe opiod paracetamol combinations (Perry et al, 2007)ConclusionsIt is important not to stop antithrombotic medication for the purpose of minor oral surgery in a primary care setting. The risk of thromboembolic events and death far outweighs the risk of post-operative bleeding. Preoperative assessment, careful surgery and local haemostasis should be the guidelines for management of such patients.
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