Can an aspirin a day keep the blood clots away?
The subject of deep vein thrombosis (DVT) prophylaxis is usually associated with postoperative immobilization or prolonged immobilization in the management of injuries such as fractures or tendon ruptures.
The necessity for DVT prophylaxis, particularly in the podiatry patient, remains unclear. No level I studies exist to direct a standard of care for the average patient with regard to DVT prophylaxis. Obviously, the risks of failing to administer DVT prophylaxis include thrombophlebitis, pulmonary embolism and death. Conversely, DVT prophylaxis may be associated with postoperative bleeding complications and less commonly with heparin-induced thrombocytopenia.1
There is a paucity of literature regarding the need for prophylaxis in the podiatry patient. Specific protocols and guidelines do not exist for the treatment of the patient undergoing immobilization following foot and ankle surgery or in the treatment of foot and ankle injuries. Neither the American Podiatric Medical Association nor the American College of Foot and Ankle Surgeons has offered recommendations or protocols regarding this matter.
The use of DVT prophylaxis for foot and ankle surgery is controversial. In general, physicians cite guidelines developed for total hip replacement, hip fracture or total knee joint replacement.1 However, a substantial difference exists among hip fracture repair, hip replacement, knee replacement surgery and foot and ankle surgery.
In a meta-review of studies focusing on a total of 6,460 patients, Budny noted patients undergoing foot and ankle surgery had a DVT incidence of 0.84 percent and a pulmonary embolus incidence of 0.34 percent.2 This could represent an extremely low incidence of thromboembolism and the author questioned the need for DVT prophylaxis in the podiatry patient.
Radl and colleagues found no association of DVT with foot and ankle surgery relative to body mass index (BMI) or body weight, duration of surgery, nicotine use or concurrent hormone replacement medications.3 In a review of 2,733 patients undergoing foot and ankle surgery, Mizel and coworkers noted a 0.22 percent incidence of DVT and a 0.15 percent incidence of pulmonary embolism.4 They concluded that prophylaxis for foot surgery was not warranted.4 Reviewing the incidence of DVT and pulmonary embolism in foot surgery, multiple authors, including Wukich, Solis and their respective coauthors, shared Mizel’s opinion.5,6 Other studies have suggested that routine DVT prophylaxis is not indicated in foot surgery although one should calculate the risk of each patient for the presence of multiple predisposing risk factors.3,7-9
The literature does not support the suggestion that DVT prophylaxis is indicated in the treatment of lower extremity fracture management or in association with Achilles tendon rupture and immobilization. Stanton examined 1,174 patients with Achilles tendon ruptures, who received no anticoagulant during treatment.10 The overall rate of DVT was small at 0.43 percent and the rate of pulmonary embolism was 0.34 percent. There was no significant difference between surgical and non-surgical management of the Achilles tendon ruptures or the age of the patient. Similarly, neither age nor BMI influenced the incidence of thromboembolic episodes.
With regard to trauma, research has demonstrated that the overall incidence of DVT increases with more proximal fracture location and decreases with more distal fracture locations. For example, researchers have associated tibial plateau fractures with a 43 percent incidence of DVT, a 22 percent incidence of tibial shaft fractures and a 13 percent incidence of tibial plafond injuries.11-14 When it comes to the treatment of tibial fractures, studies have demonstrated that advanced age and obesity are potential risk factors.11-14
Felcher and colleagues found a DVT incidence of 0.30 percent, and concluded that routine prophylaxis for DVT was not indicated in the average patient.15 However, these authors did suggest that one should consider prophylaxis if two or more risk factors were present. These risk factors included prior DVT history, obesity, the use of hormone replacement therapy or the use of birth control pills.
Nevertheless, the overall weight of the literature argues against the use of DVT prophylaxis for foot surgery. In a survey of British orthopedic foot and ankle surgeons, reviewing 35,000 surgeries performed in 2010, the incidence of DVT was 0.6 percent, the incidence of pulmonary embolism was 0.1 percent and the incidence of fatal pulmonary embolism was 0.2 percent.16 The authors concluded that of the 10,000 individuals who received prophylaxis, only one fatal pulmonary embolism was prevented. Following ankle fractures, this study demonstrated a DVT incidence of 0.12 percent and a pulmonary embolism incidence of 0.7 percent. After first metatarsal osteotomies, there was a DVT incidence of 0.1 percent and an pulmonary embolism incidence of 0.2 percent. After hindfoot fusion surgery, the study found a DVT incidence of 0.3 percent and a 0.11 percent incidence of pulmonary embolism. After total ankle replacement, there was a 0.06 incidence of DVT.
Jameson and coworkers also concluded that venous thromboembolism is rare following foot and ankle surgery, and that fracture patients were at the highest risk in this category.17 The authors concluded that no evidence exists to suggest that prophylaxis reduces the risk of DVT in foot and ankle surgery, and that prophylaxis is not required.
Griffiths and Stanton summarized the need for DVT prophylaxis in foot and ankle surgery.10 As they stated, "the pressure to prescribe chemical prophylaxis postoperatively for all orthopedic patients undergoing elective procedures, including foot and ankle surgery, is increasing ... the risk of clinically significant thromboembolic disease is so low in elective foot and ankle surgery however, that chemical prophylaxis is not indicated, regardless of patient risk factors.”
I have had the opportunity over the years to evaluate a number of malpractice cases in which patients sustained fatal pulmonary embolic disease following foot and ankle surgery. Although researchers currently argue strongly against the need for DVT prophylaxis, when such an event occurs, particularly a fatal pulmonary embolism, it is a tragedy for patients and their family, none of whom anticipated death following an elective foot procedure.
At times, one should consider the need for DVT prophylaxis. For example, in one case, a patient with a known history of factor V Leiden mutation had a tarsal tunnel decompression. The patient did not receive prophylaxis and suffered a devastating pulmonary embolism. In another case, a patient with a familial history of coagulopathy, in which a brother and father suffered from DVT, did not receive prophylaxis and the immobilization following surgery resulted in a stable pulmonary embolism. In another case, a patient with a history of recurrent lower extremity DVT underwent foot surgery, and was immobilized without prophylaxis, resulting in a fatal pulmonary embolism.
Conversely, when such incidents occur, plaintiff attorneys and unscrupulous expert witnesses seize the opportunity to "cash in" on such unfortunate happenings. For example, in one case, a healthy 33-year-old woman had a punch biopsy of the hallux interphalangeal joint for a lesion, which the physician diagnosed as an early, noninvasive melanoma. The surgeon performed an elliptical excision of the margins of the lesion at the level of the hallux interphalangeal joint. Two weeks later, the patient died of a fatal pulmonary embolism. The patient had no pertinent medical history nor was there any family history of coagulation disorders. The patient was taking drospirenone (Yasmin, Bayer), a medication known to be associated with DVT and pulmonary embolism.
Nevertheless, a podiatry “expert” testified that the patient should have had DVT prophylaxis because of the following factors.
• Cancer is a known risk factor for DVT. (Actually, large tumors produced from coagulation factors compress major venous structures).
• The surgery occurred with an ankle tourniquet (there is no evidence that a tourniquet applied for 15 minutes increases the risk of DVT).
• The patient was of German heritage and although this was not diagnosed, he was genetically predisposed to factor V Leiden mutation (there was no family history).
• The patient was immobilized (she was not supposed to walk as much for her immediate postoperative period in order to reduce scarring across the hallux interphalangeal joint).
The case resulted in a rather large settlement by the insurance carrier.
Many podiatrists are reluctant to engage in the use of injectable or oral anticoagulant therapies. However, recent changes in acceptable therapies allow the podiatric physician to provide reasonable anticoagulation prophylaxis although the aforementioned literature argues strongly against the need for such prophylaxis.
Elevation and early ambulation following surgery have long been known to decrease the incidence of DVT by 50 percent and represent a convenient means to attempt to prevent DVT.18 In addition, there has been a recent change in the acceptability of utilizing aspirin for DVT prophylaxis.19,20 Earlier literature suggested that aspirin, although providing some venous thromboembolism (VTE) protection, was inferior in efficacy in comparison to other prophylactic measures and one should not use it alone. In addition, postoperative bleeding was potentially problematic with the use of aspirin.19,20
However, recent American Academy of Orthopaedic Surgeons (AAOS) guidelines include the use of aspirin, as well as compression therapy, as acceptable alternatives to the use of anticoagulants in patients without high risk factors for DVT.21-23 Research has noted that administering aspirin at a dosage of 160 mg per day for DVT prophylaxis before total hip replacement and hip fracture surgery decreases DVT risk by 30 percent and pulmonary embolism risk by 40 percent.21-23 Although less effective than traditional anticoagulants, studies have noted that the combination of aspirin with compression therapy to the legs is an effective means for DVT prophylaxis.21-23 Aspirin certainly would represent a convenient means by which the podiatric physician could protect patient health, particularly when one combines it with early ambulation, range of motion or compression therapy.
In general, the alternatives to aspirin, early ambulation and compression therapy are less attractive to the podiatric physician and surgeon. For example, one can utilize the oral anticoagulant warfarin (Coumadin, Bristol-Myers Squibb) to inhibit vitamin K interaction with factors II, IV, IX and X. However, the use of these medications requires 36 to 72 hours for stable loading and continuous laboratory monitoring to maintain an optimal international normalized ratio between 2 and 3. One generally administers warfarin as a 7.5 mg dose 24 to 40 hours preoperatively or administers it as a 5 mg dosage the evening before surgery.
Recall that in addition to the laboratory monitoring, warfarin has a long onset of action and is affected by genetic as well as multiple environmental factors including drug and dietary factors. As a result, the patient response to warfarin is variable. One advantage to the use of warfarin is that one can reverse hemorrhagic complications with the administration of vitamin K.
Other oral alternatives currently in common use include rivaroxaban (Xarelto, Janssen Pharmaceuticals), a factor Xa inhibitor associated with significant reduction in symptomatic venous thromboembolism episodes with hip replacement and knee replacement surgery. One may also use oral dabigatran (Pradaxa, Boehringer Ingelheim) for the same purpose. These medications have the advantage of not requiring laboratory monitoring. The disadvantages of these medications include difficulty in reversing hemorrhagic complications, and the fact that they are not approved for general DVT prophylaxis and have received study primarily for major orthopedic surgery in which research has demonstrated efficacy.24
Injectable medications for DVT prophylaxis most commonly employ a low molecular weight heparin. The low molecular weight heparin is contained to the antithrombin III binding site and does not require monitoring. In addition, they are more bioavailable than fractionated heparin.
A variety of low molecular weight injectable heparins are available. These modalities include enoxaparin (Lovenox, Sanofi Aventis), dalteparin (Fragmin, Eisai), danaparoid (Orgaran, Merck), nadroparin (Fraxiparine, GlaxoSmithKline), ardeparin (Normiflo, Pfizer) and tinzaparin (Innohep, Leo Pharmaceutical Products).
Generally, patients start on these agents 12 to 24 hours following surgery, taking them by subcutaneous injection. More recently, researchers have demonstrated that administration of fondaparinux sodium (Atrixa, GlaxoSmithKline) as a 2.5 mg subcutaneous injection is more effective than some of the low molecular weight alternatives.25 One administers the medication six to eight hours following surgery as a once daily injection. Hemorrhagic complications, however, may be more common with the use of this medication in foot and ankle surgery.
There is little evidence-based medicine to support the use of DVT prophylaxis with foot and ankle surgery, or in the patient immobilized for the treatment of lower extremity pathology. The standard of care does not require DVT prophylaxis following foot or ankle surgery as studies have demonstrated no proven benefit. In addition, risks of complications, such as excessive bleeding or heparin-induced thrombocytopenia, do exist. The medical literature does not support the routine use of anticoagulation in foot and ankle surgery. Neither the American Podiatric Medical Association nor the American College of Foot and Ankle Surgeons offer guidelines suggesting the use of routine DVT prophylaxis.
Although this was not enthusiastically supported initially, the use of low-dose aspirin together with compression stockings and early mobilization would represent a convenient means by which to offer prophylaxis for the average patient who is to be immobilized.
Preoperative documentation should demonstrate that one questioned the patient for any personal or family history of coagulation disorders, or history of thromboembolic disease. If one determines the patient to be of a “higher risk category” and if he or she presents with multiple factors associated with increased risk of DVT, one can consider more traditional DVT prophylaxis.
Finally, in the evaluation of patients following surgery or who are immobilized for other reasons, the office documentation should indicate assessment for possible signs or symptoms of DVT. For example, the note might indicate no chest pain, orthopnea, dyspnea, cough, wheezing or hemoptysis. One should also check and note the absence of leg or calf pain or tenderness. The note might also indicate negative Homans’ and Pratt’s signs.
The occurrence of a fatal pulmonary embolism following elective or non-elective foot or ankle surgery, or in association with prolonged immobilization, is of course a tragedy. In hindsight, one might question the need for DVT prophylaxis in these patients. Furthermore, the failure to examine a patient for signs and symptoms suggestive of DVT may also be problematic.
Consider the utilization of aspirin in combination with early mobilization and compression therapy when appropriate.
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