Current Concepts With DVT Prophylaxis
Warfarin may allow a patient to sustain anticoagulation for years if necessary but it is not without its pitfalls. Warfarin therapy requires frequent monitoring of the patient’s international normalized ratio (INR), which is a measure of a patient’s anticoagulation status. Due to the hepatic metabolism of warfarin, it has many potential drug interactions that may render a patient overtherapeutic or undertherapeutic. An over-therapeutic INR may place a patient at high risk for adverse events due to bleeding. An undertherapeutic INR will place the patient at risk for the development of thrombosis.
Another pitfall to the use of warfarin as prophylaxis is that the action of warfarin is delayed. Warfarin use may need to stop several days before surgery and may not be effective for several days after the initial dose. This may necessitate bridge therapy with either unfractionated or low molecular weight heparin.1
In light of the wide variety of treatment options and the limited data regarding DVT prophylaxis in foot and ankle surgery, there is still significant leeway regarding the decision of whether to administer prophylaxis to a patient prior to surgery. The surgeon and patient can best make this decision jointly after a thorough discussion of the risks and benefits.
If patients have modifiable risk factors (oral contraceptive use, smoking or obesity) for VTE prior to surgery, surgery may wait until the patient has had time to undertake risk modification. Immobility is another modifiable risk factor in many patients.
When possible, early weightbearing or early mobilization protocols have the potential to reduce the risk of VTE. In regard to patients who are immobilized at the ankle, one can still educate them about active motion of the digits. When patients must be immobilized after major hindfoot surgery, the threshold for DVT prophylaxis should likely be lower although there is still no definitive data to prove this. If a patient has multiple risk factors that cannot (or will not) be modified, one may initiate DVT prophylaxis.
Again, there is no specific data on the duration of prophylactic therapy in foot and ankle surgery, but what limited data exists suggests continuing prophylaxis until the patient is mobile. The method of prophylaxis remains at the discretion of the surgeon but should take into account the risks of therapy, the willingness of the patient to adhere with the given intervention and the effectiveness of the intervention.
While DVT remains rare in the world of foot and ankle surgery, it is a serious complication that requires surgeons to evaluate every patient’s risk factors. While prevention is the primary focus of this article and should be the primary focus of the surgeon, it is important to maintain a strong clinical suspicion in patients who have a clinical presentation consistent with DVT. Early diagnosis and treatment should be the standard that all clinicians hold themselves to when confronted with any form of VTE.
Dr. Key is in private practice at Connecticut Foot and Ankle Associates in Woodbridge, Conn. He is a Fellow of the American College of Foot and Ankle Surgeons and a Clinical Instructor in the Department of Orthopaedics and Rehabilitation at the Yale University School of Medicine.
Dr. Carelock is a Chief Resident at Yale-New Haven Hospital in New Haven, Conn.
Dr. Dux is a second-year resident at Yale-New Haven Hospital in New Haven, Conn.