Travel and venous thrombosis: a systematic review

Abstract

In the past decade, numerous publications on the association between venous thrombosis (VT) and travel have been published. Relative and absolute risks of VT after travel, and particularly after travel by air, have been studied in case-control and observational follow-up studies, whereas the effect of prophylaxis has been studied through intervention trials of asymptomatic clots. The mechanism responsible for the association between travel and VT was addressed in pathophysiologic studies. Here, we systematically reviewed the epidemiologic and pathophysiologic studies about the association between travel and VT. We conclude that long-distance travel increases the risk of VT approximately two to fourfold. The absolute risk of a symptomatic event within 4 weeks of flights longer than 4 h is 1 ⁄ 4600 flights. The risk of severe pulmonary embolism (PE) occurring immediately after air travel increases with duration of travel, up to 4.8 per million in flights longer than 12 h. The mechanism responsible for the increased risk of VT after (air) travel has insufficiently been studied to draw solid conclusions, but one controlled-study showed evidence for an additional mechanism to immobilization that could lead to coagulation activation after air travel.

Prevention of VTE in Nonsurgical Patients

“…A dose-response relationship was identifi ed, with an 18% higher risk of VTE for each 2-h increase in travel duration. 122,123 However, the overall absolute incidence of a symptomatic VTE in the month following a fl ight . 4 h is 1 in 4,600 fl ights, 124 with a reported incidence of asymptomatic VTE on arrival from a trip ranging from 0% to 1.5%.…”

“…4 h is 1 in 4,600 fl ights, 124 with a reported incidence of asymptomatic VTE on arrival from a trip ranging from 0% to 1.5%. 123 The incidence varies by the type and duration of travel and by individual risk factors. [125][126][127] Thrombosis risk also appears to be increased for travel by car, bus, or train.…”

“…8 to 10 h [125][126][127][128][131][132][133] and is increased in the presence of VTE risk factors such as recent surgery. 123 For those on fl ights . 4 h, immobility during the fl ight and window seating (especially for obese persons) also increase the risk of VTE.…”

Relation between Air Travel and Venous Thromboembolism

“…Severe cases of PE immediately after a flight are rare, especially in flights taking less than eight hours (45) . In flights lasting more than twelvehours, therate is estimated at five per million (46) . Notable in this study is the fact that; not all cases of PE occur as a result of travel.…”

“…Notable in this study is the fact that; not all cases of PE occur as a result of travel. If the condition has to be associated with travel, it must have occurred up to eight weeks after the travel (46) . In eleven case controlled studies, it has been reported that the risk of VTE cases related to travel is more evident in individuals with preexisting risk factors (6,19,24,26,34,44,51,57,58,64,82) .…”