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INTRODUCTION

Venous thromboembolism (VTE), which includes pulmonary embolism (PE) and deep venous thrombosis (DVT), is a serious and costly complication after surgery. It affects an estimated 300,000–600,000 individuals in the U.S. each year, causing considerable morbidity and mortality.1 Approximately 25% of VTE occur in patients who have been hospitalized for surgery, and this number will likely be higher if silent VTE is included. Sudden death may be the initial presentation in a quarter of the patients with PE, therefore prevention is the key.1 Other potential consequences of VTE include recurrence, postthrombotic syndrome, pulmonary hypertension, and right heart failure. Despite the availability of effective VTE prophylaxis, it remains underutilized in patients undergoing major surgical procedures.

All major surgeries increase the risk for development of VTE, but the extent of that risk varies greatly across different types of surgeries. Careful preoperative assessment of patients, focusing on their risk for VTE, can help guide postoperative prophylaxis. Evidence-based guidelines from different societies provide support in relation to the timing of initiation, duration, and choice of prophylaxis. This chapter will focus on risk assessment and prevention of VTE based on recent guidelines.

PATIENT-RELATED RISK FACTORS

Virchow's triad describes three underlying mechanisms for development of VTE – venous stasis, endothelial injury, and hypercoagulability. Patients undergoing surgery typically have several risk factors, such as immobility, malignancy, or prior VTE, that reflect these underlying processes. Table 6-1 provides a more extensive list of patient-related risk factors for VTE.

TABLE 6-1Patient and Surgery-Specific Risk Factors for VTE

SURGERY-RELATED RISK FACTORS

Although the risk for postoperative VTE increases with increasing number of patient-related risk factors, healthy patients are also at significant risk for VTE after certain surgical procedures. Major orthopedic surgeries are among the highest risk procedures for VTE. In general, major surgery refers to surgery lasting longer than 45 minutes, and prolonged surgery refers to operative time of 2 hours or more. Many surgery-related factors contribute to the risk of VTE in non-orthopedic patients including the extent and duration of surgery, intraoperative positioning, type of anesthesia, site of surgery, and postoperative mobility. Table 6-1 outlines these surgery-specific risk factors.

TOOLS TO ASSESS PERIOPERATIVE VTE RISK

There are a variety of score-based tools to assess risk of VTE in hospitalized patients. The Caprini model classifies surgical patients into ...

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