Recent findings and recommendations

A review of recent literature suggests a weak association between long-distance travel (more than 8 hrs) and the development of asymptomatic venous thromboembolism (VTE). The risk is largely confined to asymptomatic calf vein thrombosis in passengers with additional predisposing factors for VTE (Chee and Watson, 2005). The frequency of symptomatic VTE has been calculated variously from 0.05% (Philbrick et al., 2007) to 1.0% (Hughes et al., 2003) and the thrombosis rate amongst arriving passengers peaks during the first week and is no longer apparent after 2 weeks (Gallus, 2005). The risk of VTE in patients with additional predisposing factors (previous VTE, recent surgery, cancer, obesity, etc) is likely to be around 5% (Aryal and Al-Khaffaf, 2006).

The risk of pulmonary embolism (PE) is very small and estimates vary between 0.5 events per million passengers (Chee and Watson, 2005) for both symptomatic and fatal PE and 2.57 events per million for travel duration exceeding 8hrs for all PE events (Hertzberg et al., 2003).

The contribution to the risk of VTE made by various travel-related factors (e.g. stasis, dehydration including alcohol consumption, cramped seats and hypobaric hypoxia) is yet to be proved but, given the plausible risk-free benefit, most airlines advise passengers to maintain adequate hydration and to take regular in-flight exercise. There is no evidence for blanket use of thromboprophylaxis such as stockings and/or drugs. However, passengers may have already made up their minds on this issue: Hughes et al (2003) found that over half the 878 participants in the NZATT study had taken aspirin and 44% had used stockings. Surprisingly, there is very little good data on the usefulness of aspirin for travel-related VTE prophylaxis. Indeed, the latest American College of Chest Physicians guidelines advise against the use of aspirin alone as prophylaxis against travel-related VTE in any patient group. However, passengers in whom additional risk factors for VTE are present, may benefit from thromboprophylaxis in the form of below-knee graduated compression stockings (providing 15-30 mmHg at the ankle). Prophylactic doses of low-molecular-weight heparin may also be considered. As already indicated, the use of aspirin is NOT recommended and the most important preventative actions are avoiding dehydration and frequently exercising leg muscles (Philbrick et al., 2007).