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 taking 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.
|“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)
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., 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.”19
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
High intensity INR 2.5-3.54
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.4,19,20 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 perioperative and/or postoperative bleeding.”20
While the current recommendations should be tailored towards the patients’ individual needs, dental professionals must consider the following dental implications when treating anticoagulated patients:
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