Air travel and thrombosis.

The current literature suggests a weak association between long-distance travel and the development of asymptomatic venous thromboembolism (VTE). Most of the data available relate to air travel and suggest that the risk is largely confined to asymptomatic calf vein thrombosis in passengers with additional risk factors for VTE, travelling for more than 8 h. The risk of both symptomatic and fatal pulmonary embolism (PE) is very small. The causal role of travel-related factors (e.g. stasis, dehydration, cramped seats and hypobaric hypoxia) is not yet proved but, given the plausible risk-free benefit, all passengers should be advised to maintain adequate hydration and exercise. There is currently no evidence for 'routine' thromboprophylaxis using stockings or drugs. In passengers with additional risk factors for VTE, thromboprophylaxis in the form of below-knee graduated compression stockings (providing 15-30 mmHg at the ankle) and/or prophylactic dose low-molecular-weight heparin may be considered. The evidence does not support the use of aspirin, which is associated with a significant rate of adverse gastrointestinal effects.