Essence of this Article

Data indicate that several factors can increase the risk of venous thromboembolism (VTE) and if a patient has multiple risk factors, there is generally a cumulative impact. Surgery and immobilization are two prominent risk factors. Major orthopaedic surgery is associated with a high risk while general surgery is also associated with a risk of VTE. However, although VTE is often associated with recent trauma or surgery, 50–70% of symptomatic cases, as well as the majority of cases of fatal pulmonary embolism (PE), occur in medical patients.

Risk factors for venous thromboembolism

Modelling data indicate that multiple risk factors can increase the likelihood of VTE54

  • Surgery, especially major orthopaedic surgery involving the lower extremity and major surgery for cancer, is a prominent risk factor for the development of VTE
  • Immobilization, such as that experienced by many patients hospitalized for acute medical illnesses, is also a risk factor
  • If a patient has multiple risk factors, there is generally a cumulative impact on the risk of VTE

Major orthopaedic surgery

Major orthopaedic surgery, such as elective hip or knee replacement surgery and hip fracture surgery, is associated with a high risk of VTE:

  • The risk results from hypercoagulability caused by trauma and/or surgery57

In the absence of prophylaxis, the incidence of DVT (as assessed by venography):54

  • Ranges from 41% to 85% after elective hip or knee replacement surgery
  • Is as high as 60% after hip fracture surgery

Orthopaedic surgery patients may also have other predisposing risk factors for VTE, such as cancer, increased age and history of prior VTE.54

The risk of VTE after major orthopaedic surgery persists after hospital discharge

  • Patients who have had total hip replacement and no VTE assessment by venography at discharge continue to be at risk of late-onset VTE at least up to 35 days after surgery58

Other surgical patients

VTE risk in general and emergency surgery:59

  • The incidence of DVT in patients undergoing general surgery without thromboprophylaxis is 15–30%; the risk of pulmonary embolism (PE) in this same group is approximately 0.08%
  • Duration of hospitalization and type of surgery affect thrombosis risk, as do increasing age and other risk factors, such as cancer, prior VTE and obesity

VTE risk in laparoscopic surgery:59

  • The relative risk of VTE with laparoscopy versus open procedures has not yet been investigated in depth
  • Based on the pathophysiology of VTE, factors that may heighten the risk with laparoscopy are duration of the procedure, patient positioning (e.g. reverse Trendelenberg position for some procedures) and the injection of air into the peritoneum
  • Shorter hospital stays and more rapid postoperative mobilization would be expected to decrease the risk

VTE risk in major gynaecological, major open urological and neurological surgery.

  • Major gynaecological surgery poses a VTE risk that is similar to the risk involved in general abdominal surgery (15–40% without preventive therapy)54
  • Major open urological procedures confer significant risk, but transurethral procedures do not54
  • Venographic studies in patients undergoing neurosurgery show a rate of DVT of approximately 30%, with increased risks in cranial surgery compared with spinal surgery, in cases of malignant tumours compared to cases of benign tumours, and in patients with leg weakness60

Immobilized patients

Immobilization increases the risk of VTE61

  • Hospitalized medical patients are often immobile because of weakness, reduced alertness or nerve injury
  • Patients in critical care settings are often bedridden
  • Even in the absence of medical illness, lack of mobility can lead to venous stasis and VTE, as can occur during long-distance air travel61

Hospitalized patients often have multiple risk factors for VTE

  • Risk factors are generally cumulative62
  • All patients should be evaluated for their risk of VTE at the time of hospital admission
  • Evaluation should be repeated whenever there is a significant change in a patient’s clinical status

Learn more about VTE risk in immobilized patients

Although VTE is often associated with recent trauma or surgery, 50–70% of symptomatic cases, as well as the majority of cases of fatal PE, occur in medical (non-surgical, non­trauma) patients.54 Prospective studies show that hospitalized medical patients at risk of VTE who do not receive preventive anticoagulant therapy develop distal DVT in the calf in 10–15% of cases. The same studies revealed an incidence of proximal DVT of 2–5% and of PE of 0.3–1.5%.62

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