Venous thromboembolism counseling & advice for travelers

Venous thromboembolism Microchapters
Patient Information Deep vein thrombosis Pulmonary embolism
Overview
Classification
Epidemiology
Risk Factors
Diagnosis
Treatment Deep Vein Thrombosis Pulmonary Embolism
Prevention

Editors-in-Chief: C. Michael Gibson, M.S., M.D. Associate Editor-In-Chief: Ujjwal Rastogi, MBBS [1]

Overview

Venous thromboembolism (VTE) consists of 2 related conditions: 1) deep vein thrombosis (DVT) and 2) pulmonary embolism (PE). 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. Previous studies have shown a 2- to 4-fold increased risk of VTE after air travel.

Risk Factors

The risk of venous thrombosis and air travel was examined in the WRIGHT (World Health Organization Research Into Global Hazards of Travel) project. Several factors have been associated with an increased risk for developing VTE:

Risk factors for developing VTE include:

Recent major surgery

Paralytic spinal cord injury

Multiple trauma

Malignancy

Congestive heart failure or respiratory failure

Hormone replacement therapy, oral contraceptive

Previous venous thromboembolism

Inherited hypercoagulable condition

Acquired hypercoagulable condition

Pregnancy

Age >40 years

Obesity

Immobility

Male gender

A retrospective cohort study shows that the risk of VTE increased with flight duration and with the number of times the employee flew during an 8-week period; the risk of VTE tripled in employees who went on 5 or more long-haul (>4 hours) flights. Each extra flight increased the risk of VTE 1.4-fold. The risk of VTE was highest in the first 2 weeks after a long-haul flight and gradually decreased to baseline after 8 weeks.

Incidence

A recent meta-analysis investigating the association between travel and VTE found a 2-fold higher risk for VTE in travelers compared with nontravelers. Significant variability was noted in the outcomes of the studies included in the review. This variability was directly related to the method used to select the comparison group in each study. When studies that used people referred for VTE evaluation as comparisons were excluded from the meta-analysis, the remaining studies showed a 3-fold higher risk of VTE associated with travel. The risk for VTE increased with travel duration. Each 2-hour increase in travel duration resulted in an 18% higher risk for VTE.

A retrospective cohort study done with 2,499 healthy Dutch commercial pilots showed the incidence of VTE to be 0.3 per 1,000 person-years.When the data were adjusted for age and sex, the rate was not different from that in the general Dutch population.

The second study was among 8,755 employees of several international companies and organizations. The overall incidence of VTE after air travel was 1.4 per 1,000 person-years. The incidence of VTE within 8 weeks of a long-haul flight (>4 hours) was 3.2 per 1,000 person-years compared with an incidence of 1.0 per 1,000 person-years in employees who did not fly. The absolute risk of VTE per flight more than 4 hours was 1 per 4,656 flights. Incidence was also higher in employees with a BMI more than 25 kg/m2 and those with height less than 1.65 m (5 ft 5 in) or more than 1.85 m (6 ft 1 in).

Both these studies were performed among populations that were younger (mean age 35–40 years) and healthier than the general population and are not, therefore, generalizable to a higher-risk population.

Diagnosis

Symptoms

Symptoms of DVT include swelling, redness, pain, or tenderness and increased warmth over the skin. It may be difficult to distinguish from muscle strain, injury, or skin infection. Prospective studies have shown that many leg DVTs are asymptomatic; therefore, the first symptoms may be due to a PE.

Symptoms of PE range from mild and nonspecific to acute, resembling heart attack or stroke. Once a clot has traveled to the lungs, common symptoms of PE are chest pain and shortness of breath. Other symptoms include dizziness, fainting, anxiety, and malaise. PE can occur in the absence of overt signs of DVT.

Treatment

Preventive measures for travelers

Several randomized controlled trials have been performed to assess the effect of prophylactic measures on VTE risk after air travel. All studies examined the risk of asymptomatic DVT in travelers making flights ≥7 hours. All travelers were encouraged to do regular exercises and to drink nonalcoholic beverages during the flight. DVT was diagnosed by venous ultrasound from 90 minutes to 48 hours after the flight. Interventions that were studied include compression stockings, aspirin, low-molecular weight heparin, and various natural extracts with anticoagulant properties. Compression stockings (10–20 mm Hg and 20–30 mm Hg) were shown to significantly reduce the risk of asymptomatic DVT; however, 4 travelers wearing compression stockings in one study developed superficial thrombophlebitis. Symptomatic DVT and PE were not observed in any of the travelers enrolled in the studies.