Warfarin Sodium is a coumadin derivative listed in the drug class as an oral anticoagulant. It interferes with the liver’s synthesis of Vitamin K-dependent clotting factors; resulting in depletion of blood clotting factors II, VII, IX, and X. Its therapeutic effect is to prevent further development of the hemostatic plug; and it prevents new thromboembolic clot formation.15 Thrombosis is the formation of abnormal blood clots (termed thrombi) that develop within the vascular system. Thrombi are carried through the bloodstream (termed emboli) which can potentially occlude the lumen of an artery or a vein and shut down a vital organ. The following conditions increase the risk of a thromboembolic event: deep venous thrombophlebitis (inflammation of a vein); atrial fibrillation (rapid, random contractions of the atria); myocardial infarction (heart attack); mechanical heart valves (artificial heart valves); carotid artery disease; or peripheral vascular disease. Additionally, clots form because there is an existing hypercoaguable condition where by the blood has a tendency to clot more rapidly than normal, caused by either a blood vessel defect, clotting factor abnormality or an immunologic abnormality.5
When patients are on warfarin therapy to prevent thromboembolic events, they are monitored by the International Normalized Ratio (INR) laboratory test. The recommended INR therapeutic range for patents on “low-intensity” warfarin therapy is between 2.0 to 3.0, with a target goal of 2.5 INR. When patients are on “high-intensity” warfarin therapy, the INR range is between 2.5 to 3.5, with a target goal of 3.0 INR.2 Indications for placing patients in these ranges are determined by the severity of the thromboembolic condition.
|Table 3. Recommended Therapeutic Range for Warfarin Therapy2|
|“Low Intensity” Warfarin Therapy INR of 2.0 to 3.0, with a target of 2.5|
(5-7mg/day for 3-6 months)
|“High Intensity” Warfarin Therapy INR of 2.5 to 3.5, with a target of 3.0|
(7-10mg/day, long term)
- Prophylaxis of venous thrombosis (high risk surgery)
- Treatment of pulmonary embolism
- Prevention of systemic embolism
- Tissue heart valves in aortic or mitral position for the first 3 months
- Tissue valves with history of pulmonary embolism
- Tissue heart valves with atrial fibrillation
- Acute MI
- Atrial fibrillation
- Valvular heart disease
- Mitral valve prolapse with history of atrial fibrillation or embolism
- Mechanical prosthetic heart values
- Prevention of recurrent MI
- Treatment of thrombosis associated with antiphospholipid antibodies
Source: Little J, Falace D, Miller C, Rhodus N. Dental Management of the Medically Compromised Patient. 7th ed. (pg. 417)
Historically, anticoagulation profiles for patients were much higher. Thus, it was necessary to discontinue or alter the warfarin therapy to avoid the risk of an excessive bleed (hemorrhage) during and post invasive surgical and non-surgical procedures. Rationale for this practice: Since Coumadin has a slow onset of action and a half-life of 36 hours it requires complete withdrawal of the drug two to three days prior to the invasive procedure. Consequently, patients' coagulation profiles resulted in suboptimal therapeutic levels, and possibly, placed patients at risk for a thromboembolic event.
The current literature cautions dental practitioners not to discontinue warfarin therapy due to the risk of producing a thromboembolic event, increasing the morbidity and mortality risks for the patient. After a 2007 comprehensive and critical review of English-language, randomized clinical trials, by Aframanian et al.,18 as part of the World Workshop of Oral Medicine IV, the authors produced a “Class I” recommendation which was supported by scientific evidence and expert opinion: It is recommended that for patients who fall “within the therapeutic range of an INR of 3.5 or below, warfarin therapy need not be modified or altered for simple single dental extractions.” Aframanian et al. also concluded that the “more complicated and invasive oral surgical procedures”, coupled with a higher range of the INR (3.5 and greater), one should consult with the prescribing physician to consider bleeding management options. Hence, patients with an INR above the therapeutic range of 3.5 are at an “increased risk of prolonged bleeding.” 18
More specifically, the following clinical guidelines summarize dental management strategies for patients on Coumadin therapy who are anticoagulated in the “low intensity” and “high intensity” therapeutic ranges, and who are scheduled for various simple and complex surgical and non-surgical procedures:
Low intensity INR 2.0-3.04
- Consult with the patient's physician and obtain recent INR laboratory results prior to the invasive dental procedure.
- If the INR is between the range of 2.0-3.0:
- When performing most invasive non-surgical or simple surgical procedures, one can proceed if the INR is within therapeutic range 2.0-3.0. (Non-surgical invasive procedures can include subgingival debridement with slight to moderate inflammation.) Proceed with attention to control bleeding with standard local hemostatic measures.
- If the INR is greater than 2.5:
- When performing complex surgical procedures or subgingival debridement with severe inflammation, consult with the patient’s physician to allow the INR to drift down to a safe INR range between 2-2.5. Proceed with attention to control bleeding with standard local hemostatic measures.
- Considerations for transiently interrupting the anticoagulation therapy must be discussed with the patient’s physician.
High intensity INR 2.5-3.54
- Consult with the patient’s physician and obtain recent INR laboratory results prior to the invasive dental procedure.
- When performing non-surgical (subgingival debridement with sight to moderate inflammation) and simple surgical procedures maintain INR in the 2.5-3.5 range; proceed with attention to standard local hemostatic measures to limit and control bleeding.
- When performing complex surgical procedures or subgingival debridement with severe inflammation consult with the patient’s physician; it may be safe to proceed in the lower ranges of INR 2.5-3.0 with attention to local hemostatic measures. Considerations for transiently interrupting the anticoagulation therapy must be discussed with the patient's physician.
- Consider use of low molecular weight heparin preparations to bridge the patient through the invasive procedure as a substitute anticoagulant.
It can be concluded that most simple and routine invasive dental procedures can be safely performed when the INR is ≤ 3.0/3.5; and it is advised not to proceed when the INR value is out of range or when complex, surgical and non-surgical procedures are planned.4,18,19 When allowing for higher normal therapeutic ranges of INR during invasive dental procedures, consider operator experience. Under these conditions, it is prudent to consult with the patient’s supervising physician; obtain results of an INR laboratory test within 24 hours of the invasive dental procedure; and be prepared to use hemostatic measures to manage the expected clinical bleed for all planned dental procedures. Equally compelling and widely accepted, presented by authors Jeske and Suchko, is the fact that “the risk of experiencing a thromboembolism outweighs the risk of experiencing excessive postoperative bleeding.”19
While the current recommendations should be tailored towards the patients’ individual needs, dental professionals must consider the following dental implications when treating anticoagulated patients:
- Identify the fundamental cause of the bleeding disorder for which anticoagulation therapy is indicated.
- Consider operator experience with complex invasive dental procedures.
- Consider preexisting infection and or the degree of inflammation of the soft tissues.
- Consider the extensiveness of the invasive procedure, especially significant soft tissue and bone trauma.
- Consider bleeding management strategies and the availability of local hemostatic measures when the risk of a bleed is expected.
- Consider the probable risk of inducing a thromboembolic event when discontinuing or altering the anticoagulant drug; thus, resulting in coagulation profiles that are in the suboptimal therapeutic range.
- Implement a heightened awareness when treatment planning: consider the complexity of the invasive dental procedure; seek medical advice from the patient’s physician; and retrieve the results of the most recent INR test.4,20
Heparin: Managing dental patients on standard heparin and low molecular weight heparin (LMWH) is important when providers need to control bleeding during and following invasive dental procedures. Standard heparin itself is not considered an anticoagulant but serves as the catalyst that inhibits plasma thrombin as well as coagulation factors IX, X, XI, XII and plasmin; thus, preventing the conversion of fibrinogen to fibrin. LMWHs exert their potentiating anticoagulant effects more so on factor Xa.2
These drugs are used as a prophylaxis antithrombic agent and in the treatment of thromboembolic disorders. Treatment with standard heparin usually consists of IV infusions in a hospital setting which requires monitoring with the aPTT laboratory test. LMWH preparations are administered subcutaneously on an out-patient basis. Their dosage is calculated based on the patient's body weight and is given on an every 12-hour basis.2
When considering substituting LMWH preparations, dalteparin (Fragmin), for Coumadin when a dental surgical or nonsurgical procedure is planned, one must consult with the patient's physician to strictly and safely manage the medication schedules. The following short-term heparinization schedule is recommended: Coumadin is discontinued 4 days prior to the invasive dental procedure and Fragmin is started. During this 4-day period Fragmin is administered every 12 hours. An evening dose of Fragmin is administered on day 4; the invasive dental procedure is scheduled 12 hours after the evening dose of Fragmin. On the morning of the dental procedure Fragmin is held back. During the evening of the surgical procedure both Fragmin and Coumadin are resumed and continued until the INR is within the therapeutic range of 2.0-3.5. At this point, Coumadin is continued and Fragmin is discontinued.4