Pertinent Pointers On DVT Prophylaxis

By Mario Ponticello, DPM, and John Steinberg, DPM

The incorporation of an evidence-based approach in modern medicine is in line with Einstein’s comment that “The important thing is not to stop questioning.” The evolution of evidence-based medicine requires curiosity and a hunger for knowledge. Often, searching for answers only raises more questions and this is certainly the case with deep vein thrombosis (DVT). Research in the area of DVT has resulted in a wealth of knowledge in the medical and general surgical arenas. Unfortunately, little has been written about DVT within the podiatric literature. Orthopedic writings on DVT prophylaxis focus extensively on hip and knee arthroplasty since researchers reported that total hip and knee arthroplasty (THA and TKA) patients have a 70 percent risk of developing DVT postoperatively.1 In regard to DVT, there are some key questions to answer. • What is the cause of a DVT in the perioperative patient? • What is the incidence of DVTs in the foot and ankle patient? • What does the literature say in regard to the timing of initiating prophylaxis? In addition to understanding the current guidelines as they relate to the orthopedic population, clinicians should also be aware of risk stratification schemes. Understanding The Potential Impact Of DVT Deep vein thrombosis is a major complication that can occur after surgical intervention and several possible sequelae may result.2 The patient may experience chronic pain, swelling, skin ulceration secondary to post-phlebitic syndrome and pulmonary embolism (PE). Every year, an estimated one in 1,000 people in the general population will experience DVT and the risk increases proportionally with patient age. Every year, 500,000 cases of DVT and PE occur with a preponderance of the PEs (70 percent) being diagnosed post-mortem.3 Likewise, approximately 70 percent of patients symptomatic from a concurrent PE are dead within the first hour of symptom onset.1 Researchers say the use of appropriate thromboprophylaxis could prevent approximately 20,000 to 30,000 deaths in the United States alone.4 As one can see, the magnitude of these sequelae ranges from localized lower extremity symptoms to a life-threatening event. What Causes DVT In The Perioperative Patient? The exact sequence leading to DVT formation is unknown. In 1859, Virchow derived his famous triad regarding DVT formation and he observed the following causes: blood stasis, changes in vessel wall continuity and hypercoagulability.5 In the operative setting, a DVT may result from venous stasis, an acquired hypercoagulable state with inhibition of the fibrinolytic system, endothelial injury, limb position and tourniquet use.1 In the presence of endothelial injury, subendothelial ligands become exposed and eventually activation of integrins occurs. The clotting cascade continues and results in clot formation.5 Stasis of blood is what most commonly precipitates venous thrombosis.6,7 The incidence of DVT in hospitalized patients falls as patients begin to walk, supporting the idea that immobility and stasis precipitate DVT.5,8 Blood stasis has also been linked to endothelial damage. Evidence indicates that stasis can result in hemoglobin desaturation, leading to a hypoxic insult to the endothelium.9 Since the endothelium is primarily oxygenated and perfused directly by the blood in the vessel lumen, hypoxia can result in various cellular responses depending on the degree and duration of the hypoxia. This ischemia activates endothelial cells and a protein linked to leukocyte infiltration, inflammation and thrombosis in thrombophlebitis.5,10 It is a common belief that tourniquets cause stasis or vessel injury, and result in an increased risk of DVT formation. However, in an age-matched venography study examining the operative side with tourniquet, the operative side without tourniquet and control legs without tourniquet and operation, DVTs were similarly present in the operative extremities with and without tourniquets.11 In fact, the control group had a higher DVT incidence.

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