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As we were all taught in med school, long-distance flights, or even a long car trip, greatly increase your risk for deep venous thrombosis and pulmonary embolism ... right? (I feel like I've answered about 8 board questions featuring this scenario.) The CDC even has a whole page of guidelines detailing the travel-DVT-risk-connection and the data behind it.
Trouble is, it's not true, according to the most complete analysis of the evidence.
The ACCP released its latest edition of its authoritative Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in the February CHEST.
As guideline panel chair Gordon Guyatt explains on KevinMD, after they exhaustively examined the available studies on travel and DVT / pulmonary embolism, they concluded:
The risk of DVT in most long-distance travel is extremely low, and for most people, not worth any other intervention other than moving around periodically.
People at increased risk for DVT / PE should get up frequently, and should also do calf muscle exercises, sit in aisle seats if they can, and consider wearing below-the-knee compression stockings, the experts say. Who are at increased DVT-PE risk? Guyatt et al suggest the following groups of patients should take the increased-activity measures:
- Previous DVT/pulmonary embolism or known thrombophilic disorder
- Recent surgery or trauma
- Advanced age
- Estrogen use, including oral contraceptives
- Severe obesity
There was some rumor and innuendo in the past (from the LONFLIT studies, detailed on the CDC's page linked above) that aspirin or low-molecular weight heparin should be considered for people at elevated DVT-PE risk on long flights. Pshaw, say the authors of the new guidelines.
Clinical Takeaway: On long plane flights, even people with prior DVT-PE or a known hypercoaguable state need to do nothing more than frequent leg stretches, occasional in-flight walking, and calf muscle exercises to reduce their risk.