Pertinent Pointers On DVT Prophylaxis

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Continuing Education Course #151—April 2007

I am pleased to introduce the latest article, “Pertinent Pointers On DVT Prophylaxis,” in our CE series. This series, brought to you by the North American Center for Continuing Medical Education (NACCME), consists of complimentary CE activities that qualify for one continuing education contact hour (.1 CEU). Readers will not be required to pay a processing fee for this course.
Given the potentially grave complication of deep vein thrombosis (DVT), it is vital to have a strong understanding of the orthopedic literature on the subject. Accordingly, Mario Ponticello, DPM, and John Steinberg, DPM, assess the available studies, review key risk classifications and offer other pertinent insights on the use of DVT prophylaxis.
At the end of this article, you’ll find a nine-question exam. Please mark your responses on the enclosed postcard and return it to NACCME. This course will be posted on Podiatry Today’s Web site (www.podiatrytoday.com) roughly one month after the publication date. I hope this CE series contributes to your clinical skills.

Sincerely,

Jeff A. Hall
Executive Editor
Podiatry Today

INSTRUCTIONS: Physicians may receive one continuing education contact hour (.1 CEU) by reading the article on pg. 84 and successfully answering the questions on pg. 90. Use the enclosed card provided to submit your answers or log on to www.podiatrytoday.com and respond via fax to (610) 560-0502.
ACCREDITATION: NACCME is approved by the Council on Podiatric Medical Education as a sponsor of continuing education in podiatric medicine.
DESIGNATION: This activity is approved for 1 continuing education contact hour or .1 CEU.
DISCLOSURE POLICY: All faculty participating in Continuing Education programs sponsored by NACCME are expected to disclose to the audience any real or apparent conflicts of interest related to the content of their presentation.
DISCLOSURE STATEMENTS: Drs. Ponticello and Steinberg have disclosed that they have no significant financial relationship with any organization that could be perceived as a real or apparent conflict of interest in the context of the subject of their presentation.
GRADING: Answers to the CE exam will be graded by NACCME. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam.
TARGET AUDIENCE: Podiatrists
RELEASE DATE: April 2007
EXPIRATION DATE: April 30, 2008
LEARNING OBJECTIVES: At the conclusion of this activity, participants should be able to:
• cite current statistics on the number of annual cases in which patients have a combination of DVT and pulmonary embolism (PE);
• discuss possible causes for DVT;
• describe potential risk factors for DVT;
• review study findings on the use of enoxaparin sodium, ardeparin and dalteparin for DVT prophylaxis;
• discuss the guidelines for antithrombotic prophylaxis; and
• list preventive strategies for patients at low risk, moderate risk, high risk and highest risk for VTE.

Sponsored by the North American Center for Continuing Medical Education.

With deep vein thrombosis, there is a triad of hypercoagulability, venous stasis and endothelial damage.  (Photo courtesy of Allen B. Grossman, DPM, and Matt Sowa, DPM)
Risk Factors For DVT In Patients Who Undergo Orthopedic Surgery
THRIFT-II Guidelines On DVT Risk Classification
A Guide To VTE Risk And Key Prevention Strategies
90
Author(s): 
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

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