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

Flight Related Factors

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

Pr-Existing VTE Risk Factors

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

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

Prevention

Prevention consists of adequate hydration(drinking, abstaining from alcoholic beverages and caffeine), moving around and calf muscle exercises. In patients with a known predisposition for thrombosis, aspirin is often prescribed, as this acts as a mild anticoagulant. Severe risk for thrombosis can prompt a physician to prescribe injections with low molecular weight heparin (LMWH), a form of prophylaxis already in common use in hospital patients.

There is clinical evidence to suggest that wearing compression socks whilst traveling also reduces the incidence of thrombosis in people on long haul flights. A randomised study in 2001 compared two sets of long haul airline passengers, one set wore MediUK mediven travel compression hosiery the others did not. The passengers were all scanned and blood tested to check for the incidence of DVT. The results showed that asymptomatic DVT occurred in 10% of the passengers who did not wear compression socks. The group wearing compression had no DVTs. The authors concluded that wearing elastic compression hosiery reduces the incidence of DVT in long haul airline passengers.

Prevention

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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