Deep venous thrombosis (DVT) and pulmonary embolism (PE) are major causes of morbidity and mortality in the perioperative period (Figure 1). Despite the availability of effective prophylactic agents, most patients who are at significant risk for postoperative DVT do not receive appropriate preventive care. This article will review the etiology of perioperative DVT and PE, the pharmacology of common anticoagulant therapies, and the risks and benefits of various prophylactic regimens. This article will also review the safe and effective use of anticoagulant and mechanical therapies in the perioperative periods with regard to type of surgery: general, gynecologic, urologic, neurosurgical and orthopedic.

Risk Factors for Postoperative Deep Venous Thrombosis Reduced Blood Flow / Venous Stasis

Bed rest
Congestive heart failure
History of venous thrombosis
Proximal venous obstruction secondary to injury or mass
Venous insufficiency

Hypercoagulability

Antithrombin III resistance
Dysfibrinoginemia
Estrogen oral contraceptives
Factor V resistance
Homocystinuria
Inflammatory bowel disease
Lupus anticoagulant
Nephrotic syndrome
Paroxysmal nocturnal hemoglobinuria
Postoperative/posttrauma thrombosis
Protein C deficiency
Protein S deficiency

Vessel Injury

Surgery
Trauma
Vasculitis

Table 2. Incidence of Deep Venous Thrombosis
in Patients not Receiving DVT Prophylaxis General surgery, age < 40
General surgery, age > 40 or malignancy
Gynecologic surgery
Gynecologic surgery for malignancy
Urologic surgery
Urologic surgery for malignancy
Intracranial neurosurgery
Acute spinal cord injury
Orthopedic surgery, hip fracture
Orthopedic surgery, total hip arthroplasty
Orthopedic surgery, total knee arthroplasty 10-20%

Table 3. DVT and PE Prophylactic Agents and their Application

Low-dose unfractionated heparin
Adjusted dose unfractionated heparin
Low-molecular weight heparin

Dextran

Aspirin
Warfarin: low dose
Warfarin: variable dose
Elastic compression stockings
Intermittent pneumatic compression boots

Orthopedic Surgery
Patients undergoing major orthopedic procedures of the hip or knee represent a population at great risk for DVT and PE. In addition to the high incidences of DVT as outlined in Table 2, the risk of PE in those patients who do not receive DVT prophylaxis is approximately 5% with a 20% mortality. While early ambulation is effective in lowering the risk of a thromboembolic event, prophylactic anticoagulant therapy is also necessary in patients with hip fractures and in those undergoing hip and knee arthroplasty.

Conclusions

The prophylactic use of pharmacologic agents and/or mechanical devices for the prevention of deep venous thrombosis and pulmonary emboli has become standard care for the perioperative patient. It is hoped that this article provides a general understanding of the etiology and incidence of perioperative DVT, as well as the pharmacology, indications and risks of various prophylactic regimens. The information and recommendations contained in this article are not intended to dictate clinical practice, but rather to stimulate further reading on this topic.

B. Todd Sitzman, M.D., M.P.H.
B. Todd Sitzman, M.D., M.P.H. is with the Department of
Anesthesiology and Pain Management, Mayo Clinic Jacksonville