Venous thrombosis is a major cause of disability and death in all patient populations. Autopsy studies of hospitalized patients have demonstrated that massive pulmonary embolism (PE) is the cause of death in 5–10% of all hospital deaths and have suggested that two-thirds of all clinically important venous emboli are never recognized during life [1,2]. In a large multi-center study, 30,827 surgical patients were evaluated with respect to venous thromboembolism (VTE) risk and appropriate prophylaxis as recommended by the American College of Chest Physician (ACCP). This study showed that 19,842 surgical patients were considered at risk for VTE but only 11,613 (58.5%) received appropriate ACCP-recommended VTE prophylaxis . More recently, the Surgical Care Improvement Project selected the application of VTE prophylaxis as a nationally reported metric for preventing VTE . The purpose of this chapter is to review the pathophysiology of perioperative deep vein thrombosis (DVT), assess preoperative VTE risk and review the modalities of prophylaxis for preventing postoperative VTE in surgical patients.
The pathophysiologic changes of stasis, intimal injury, and hypercoagulability predispose surgical patients to the development of DVT or PE. The supine position on the operating room table, the anatomic position of the extremities for some surgical procedures, and the effect of anesthesia all contribute to stasis during surgery. Venographic contrast studies have shown that the supine position on the operating table decreases venous return [5,6]. In orthopedic, gynecologic, and urologic surgeries, the anatomic position of the body that provides the best surgical access to the operative site impairs adequate venous drainage during the procedure . For example, in total hip replacement and hip fracture repair, the flexion and adduction of the hip that is required for better anatomic access to the surgical field has been shown to impair venous return . Anesthesia causes peripheral venous vasodilation, which results in increased venous capacitance and decreased venous return during the operative procedure [8–10].