Prevention of Venous Thromboembolism. part 6

The implementation of evidence-based and thoughtful prophylaxis strategies provides benefit to patients, and should also protect their caregivers and the hospitals providing care from legal liability. We recommend that every hospital develop a formal strategy that addresses the prevention of thromboembolic complications. This should generally be in the form of a written thromboprophylaxis policy, especially for high-risk groups.

1.4 Important issues related to studies of thromboprophylaxis

The appropriate interpretation of published information about thromboprophylaxis requires the consideration of a number of important issues.

1.4.1 Limitations of DVT screening methods

Each of the methods used to screen for DVT in clinical trials has its own limitations. Fibrinogen leg scanning, also called the fibrinogen uptake test (FUT), was used

Table 5—Levels of Thromboembolism Risk in Surgical Patients Without Prophylaxis extensively to detect subclinical DVT in many early prophylaxis trials.

Level of Risk Calf DVT, %





PE, %



Successful Prevention Strategies
Low risk

Minor surgery in patients < 40 yr with no additional risk factors

2 0.4 0.2 < 0.01 No specific prophylaxis; early and “aggressive” mobilization
Moderate risk

Minor surgery in patients with additional risk factors

Surgery in patients aged 40-60 yr with no additional risk factors

10-20 2-4 1-2 0.1-0.4 LDUH (q12h), LMWH (< 3,400 U daily), GCS, or IPC
High risk

Surgery in patients > 60 yr, or age 40-60 with additional risk factors (prior VTE, cancer, molecular hypercoagulability)

20-40 4-8 2-4 0.4-1.0 LDUH (q8h), LMWH (> 3,400 U daily), or IPC
Highest risk

Surgery in patients with multiple risk factors (age > 40 yr, cancer, prior VTE)

Hip or knee arthroplasty, HFS Major trauma; SCI

40-80 10-20 4-10 0.2-5 LMWH (> 3,400 U daily), fondaparinux, oral VKAs (INR, 2-3), or IPC/GCS + LDUH/ LMWH

Modified from Geerts et al.

The test is no longer available because of concerns about the potential for viral transmission with this human blood product. Furthermore, the FUT has been shown to lack both specificity and sensitivity for the detection of DVT, and is poorly correlated with major thromboembolic events. Impedance plethysmography also has been shown to have low accuracy in the screening of asymptomatic high-risk patients, and is no longer utilized.

Contrast venography has long been the diagnostic standard in thromboprophylaxis trials because of its high sensitivity for detecting DVT and the availability of hardcopy images for blinded study adjudication. Many pivotal, practice-changing prophylaxis trials have used venography as the primary outcome measure of efficacy.

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