Deep venous thrombosis (DVT) is a common problem in trauma patients. Many trauma centers have developed practice guidelines for beginning mechanical or chemoprophylactic measures as soon as practical in patients at risk. Some believe that below-knee and above-knee DVT are different, with those located below the knee posing a lower risk for propagation and pulmonary embolism. As always, we need to know, is it true?

The group at Oregon Health and Science University performed a retrospective review of six years of their experience with lower extremity DVT. They identified 308 patients who developed this complication and noted the following interesting findings:

• Two thirds developed below-knee DVT, one third above-knee
• Overall rate of pulmonary embolism (PE) was about 4% overall
• PE occurred with equal frequency in below-knee vs above-knee DVT
• The rate at which DVT resolved was no different in patients receiving prophylactic doses of enoxaparin vs therapeutic dosing
• Below-knee DVT did not resolve faster than above-knee. Thus they are not more likely to resolve spontaneously

The point of looking for and giving enoxaparin and similar drugs in trauma patients is to avoid DVT, limit it’s progression, and prevent PE. This study showed that there really is no difference between below-knee and above-knee DVT, and that they should be treated similarly. Unfortunately, it also showed that prophylactic and therapeutic management worked equally as well. This is probably due to the fact that there are major differences across various types of trauma patients and that we still don’t know how to calculate the right dose of enoxaparin. However, we do have some tools to help us make a better guess. 

Bottom line: Trauma patients with any lower extremity DVT need to be treated, and enoxaparin is a common way to do this. Below-knee vs above-knee does not matter. If enoxaparin is used, just selecting a therapeutic dose (e.g. 1mg/kg bid) is not enough. Monitoring with anti-factor Xa levels or thromboelastogram (TEG) may help optimize effectiveness and reduce risk of PE.

Related posts:

• Does interrupting DVT prophylaxis increase risk?
• DVT caused by microparticles?
• Enoxaparin and pregnancy

Reference: The effects of location and low-molecular-weight heparin administration on deep vein thrombosis outcomes in trauma patients. J Trauma 74(2):476-481, 2013.