Deep vein thrombosis economy class syndrome
Deep Vein Thrombosis Microchapters
Deep vein thrombosis economy class syndrome On the Web
Economy class syndrome is the occurrence of venous thromboembolism (VTE) among air travelers. VTE consists of deep vein thrombosis (DVT), pulmonary embolism (PE), or both. DVT occurs when a deep vein is partially or completely blocked by a blood clot, most commonly in the legs. The clot may break off and travel to the vessels in the lung, causing a life-threatening PE.
- VTE associated with air travel was first described in the early 1950s.
- The term was first coined in the late 1980s when it turned out that people who had traveled long distances by plane were at an increased risk for thrombosis, especially deep venous thrombosis and its main complication, pulmonary embolism. Although all these diseases had been recognised for a long time, the possibility of litigation against airline companies brought them into the limelight when this "syndrome" was reported.
- The WHO Research Into Global Hazards of Travel (WRIGHT) project, which was set up on 21 June 2001, is a comprehensive research programme developed by the WRIGHT group under the auspices of the World Health Organization. The project consists of a series of research studies to fill the key information gaps in available knowledge on the suspected link between air travel and venous thrombosis. The studies which cover epidemiological, clinical and physiological areas, will provide key information on VTE and air travel. The objectives of the WRIGHT (WHO Research Into Global Hazards of Travel) project were to confirm that the risk of VTE is increased by air travel and to determine the magnitude of risk, the effect of other factors on the risk and to study the effect of preventive measures on risk.
The mechanism for thrombosis in travelers is probably due to a combination of immobilization, dehydration and per-existing underlying VTE risk factors. Patients with diseases that predispose them for thrombosis, such as antiphospholipid syndrome or cancer, are probably at a much greater risk. The highest risk groups include the elderly, pregnant women, those suffering serious medical conditions such as cancer and those with recent orthopedic surgery (legs or knees).
Risk Factors and Triggers
Travel Related Factors
- Most information about blood clots and long-distance travel comes from information that has been gathered about air travel. However, anyone traveling more than four hours, whether by air, car, bus, or train, can be at risk for blood clots.
- Air flight related factors that increase the risk of VTE are:
Preexisting VTE Risk Factors
The risk of VTE among travelers is higher among subjects who have risk factors for VTE. Please note that the word risk factors refers to those epidemiologic and genetic variables that expose someone to a higher risk of developing venous thrombosis, whereas the word triggers refer to those factors in the patients immediate history or environment that may have lead to the occurrence of the venous thrombosis. Shown below is a list of predisposing factors to VTE. The risk factors are classified as moderate or weak depending on how strongly they predispose for a VTE.
|Moderate risk factors||Weak risk factors|
||❑ Advanced age |
Preexisting VTE Triggers
The risk of VTE among travelers is higher among subjects who have triggers for VTE. Please note that the word risk factors refers to those epidemiologic and genetic variables that expose someone to a higher risk of developing venous thrombosis, whereas the word triggers refer to those factors in the patients immediate history or environment that may have lead to the occurrence of the venous thrombosis. Shown below is a list of triggers of VTE. The triggers are classified as strong, moderate, or weak depending on how strongly they predispose for a VTE.
|Strong triggers||Moderate triggers||Weak triggers|
|❑ Bone fracture (hip or leg)
||❑ Athroscopic knee surgery
||❑ Bed rest for more than 3 days |
❑ Prolonged car or air travel
Epidemiology and Demographics
- The annual incidence of VTE in the general population has been estimated at 0.1% but is higher in subpopulations with risk factors for VTE. The actual incidence of travel-related VTE is difficult to determine, since there is no consensus on the definition of travel-related VTE, particularly in regards to duration of travel and time window after travel. Estimates of travel-related VTE incidence vary because of differences between studies in duration of travel, measured outcome, time window after the flight, and the populations studied.
- In general, the overall incidence of travel-related VTE is low. Two studies reported that the absolute risk of VTE for flights >4 hours is 1 in 4,656 flights and 1 in 6,000 flights. People who travel on long-distance flights are generally healthier and therefore are at lower risk for VTE than the general population. Five prospective studies that assessed the incidence of DVT among travelers at low to intermediate risk for VTE after travel >8 hours yielded an overall incidence of VTE of 0.5%, while the incidence of symptomatic VTE was 0.3%.
- Numerous studies have examined the association between travel, particularly air travel, and VTE. However, these studies had differences in methods. Outcomes ranged from asymptomatic DVT to symptomatic DVT/PE to severe or fatal PE. Asymptomatic DVT is estimated to be 5- to 20-fold more common than symptomatic events. Definitions of long-distance travel ranged from flight duration >3 hours to >10 hours (most >4 hours). The time window until illness after the flight ranged from hours after landing to ≥8 weeks (most 4 weeks).
- Published studies have yielded varying results; some studies found that long-distance travel increased the risk of VTE, and others either found no definitive evidence that it increased the risk of VTE or found that it increased the risk only if ≥1 additional risk factors were present. Most studies found long-distance air travel to be a weak risk factor for VTE, and most VTE occurred as asymptomatic DVT of uncertain clinical significance in passengers with additional preexisting risk factors.
- Long-distance air travel may increase the risk of VTE by 2- to 4-fold. A similar increase in risk is also seen with other modes of travel, such as car, bus, or train, implying that the increase in risk is caused mainly by prolonged limited mobility rather than by the cabin environment. The risk is the same for economy-class and business-class travel. The risk increases with increasing travel duration and with preexisting risk factors. The risk decreases with time after air travel; most air travel–related VTE occurs within the first 1–2 weeks after the flight and returns to baseline by 8 weeks.
Deep Vein Thrombosis
About half of people with DVT have no symptoms at all. The following are the most common symptoms of DVT that occur in the affected part of the body (usually the leg or arm):
- Swelling of your leg or arm
- Pain or tenderness that can not be explained
- Skin that is warm to the touch
- Redness of the skin
PE can be present without any symptoms of a DVT. Symptoms of a PE can include:
- Difficulty breathing
- Faster than normal or irregular heartbeat
- Chest pain or discomfort, which usually worsens with a deep breath or coughing
- Coughing up blood
- Lightheadedness, or fainting
CDC Information To Travelers
The CDC advises travelers to take the following measures to prevent VTE:
- Know what to look for. Be alert to the signs and symptoms of blood clots.
- Talk with your doctor if you think you may be at risk for blood clots. If you have had a previous blood clot, or if a family member has a history of blood clots or an inherited clotting disorder, talk with your doctor to learn more about your individual risks.
- Move your legs frequently when on long trips and exercise your calf muscles to improve the flow of blood. If you’ve been sitting for a long time, take a break to stretch your legs. Extend your legs straight out and flex your ankles (pulling your toes toward you). Some airlines suggest pulling each knee up toward the chest and holding it there with your hands on your lower leg for 15 seconds, and repeat up to 10 times. These types of activities help to improve the flow of blood in your legs.
- If you are at risk, talk with your doctor to learn more about how to prevent blood clots. For example, some people may benefit by wearing graduated compression stockings.
- If you are on blood thinners, also known as anticoagulants, be sure to follow your doctor’s recommendations on medication use.
Indications for Preventive Measures
Shown below is an algorithm for the indications of preventive measure for VTE among subjects undergoing a long travel.
Recommend VTE preventive measures:
❑ Calf muscle exercise (Grade 2, level of evidence C)
❑ Frequent ambulation (Grade 2, level of evidence C)
❑ To sit in an aisle seat (Grade 2, level of evidence C)
❑ Graduated compression stockings below the knee, pressure: 15-30 mmHg (Grade 2, level of evidence C)
❑ No pharmacological VTE prophylaxis (Grade 2, level of evidence C)
|❑ No preventive measures are required |
(Grade 2, level of evidence C)
2012 American College of Chest Physicians Evidence-Based Clinical Practice Guidelines: Recommendations for Prevention of VTE in Nonsurgical Patients (DO NOT EDIT)
Recommendations for Thromboprophylaxis during Long-Distance Travel (DO NOT EDIT)
|"1. For long-distance travelers at increased risk of VTE (including previous VTE, recent surgery or trauma, active malignancy, pregnancy, estrogen use, advanced age, limited mobility, severe obesity, or known thrombophilic disorder), we suggest frequent ambulation, calf muscle exercise, or sitting in an aisle seat if feasible (Level of evidence C). "|
|"2. For long-distance travelers at increased risk of VTE (including previous VTE, recent surgery or trauma, active malignancy, pregnancy, estrogen use, advanced age, limited mobility, severe obesity, or known thrombophilic disorder), we suggest use of properly fitted, below-knee graduated compression stockings (GCS) providing 15 to 30 mmHg of pressure at the ankle during travel (Level of evidence C). For all other long-distance travelers, we suggest against the use of GCS (Level of evidence C). "|
|"3. For long-distance travelers, we suggest against the use of aspirin or anticoagulants to prevent VTE (Level of evidence C). "|
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