Deep vein thrombosis economy class syndrome

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

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.

Historical Perspective

• 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.

Pathophysiology

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:
  • Increased duration of the air flight
  • Several flights within a short period of time

Pr-Existing VTE Risk Factors

The risk of VTE among travellers 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
❑ Chemotherapy ❑ Chronic heart failure ❑ Respiratory failure ❑ Hormone replacement therapy ❑ Cancer ❑ Oral contraceptive pills ❑ Stroke ❑ Pregnancy ❑ Postpartum ❑ Prior history of VTE ❑ Thrombophilia	❑ Advanced age ❑ Laparoscopic surgery ❑ Prepartum ❑ Obesity ❑ Varicose veins

Pr-Existing VTE Triggers

The risk of VTE among travellers 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) ❑ Hip replacement surgery ❑ Knee replacement surgery ❑ Major general surgery ❑ Significant trauma ❑ Spinal cord injury	❑ Athroscopic knee surgery ❑ Central venous lines ❑ Chemotherapy	❑ Bed rest for more than 3 days ❑ Prolonged car or air travel ❑ Laparoscopic surgery ❑ Prepartum

Symptoms

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

Pulmonary Embolism

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
• Anxiety
• Coughing up blood
• Lightheadedness, or fainting

Prevention

CDC Information To Travelers

The CDC advises travelers with the following measures for the prevention of 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.

Does the patient has any of the following that increase the risk of VTE? ❑ Prior VTE episode ❑ Recent trauma ❑ Recent surgery ❑ Active cancer ❑ Advanced age ❑ Immobility ❑ Severe obesity ❑ Estrogen intake ❑ Thrombophilia

Yes

No

Recommend VTE preventive measures: ❑ Calf muscle exercise ❑ Frequent ambulation ❑ To sit in an aisle seat ❑ Graduated compression stockings below the knee (pressure: 15-30 mmHg) ❑ No pharmacological VTE prophylaxis

❑ No preventive measures are required

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)

Grade 2

"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 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). "

References

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