Hypoxia–reoxygenation contributes to increased frequency of venous thromboembolism in air travellers (original) (raw)
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British Journal of Haematology, 2005
The current literature suggests a weak association between longdistance 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.
Journal of Travel Medicine, 2006
Air travel is associated with a risk of deep vein thrombosis and pulmonary embolism, which may be fatal. The exact incidence of thromboembolism in relation to air travel is uncertain, though it has been estimated that at least 5% of all cases of deep venous thrombosis may be linked to air travel. The term "economy class syndrome" has been coined to describe the phenomenon, and this also emphasizes the role of impairment of venous circulation due to prolonged immobility in a cramped position, in the pathogenesis of the thrombosis. A number of risk factors specific to air travel are recognized, including immobility (leading to stasis in the lower limbs and hemoconcentration), compression of the popliteal vein by the edge of the seat, and dehydration. However, inherited hematological abnormalities may also predispose to thrombosis. This article reviews the pathophysiology of venous thrombosis, and gives advice on prevention as well as guidelines on the management of established thromboembolism.
Changes in blood coagulation of arm and leg veins during a simulated long-haul flight
Thrombosis Research, 2007
Introduction: Long-haul flights are associated with an increased incidence for venous thromboembolic events. At present, markers of coagulation and fibrinolysis were only analyzed from arm veins after long distance travel. Respective data from leg veins are missing. Materials and methods: Here, we measured these parameters in healthy volunteers (n = 12) before and after 10 h sitting in modern aircraft chairs under normobaric hypoxia (corresponding to 2400 m altitude). Blood was collected from arm and leg veins before, immediately after and 1 day after sitting in the hypoxic chamber. Results: We did not find any evidence for a significant intravasal thrombin and fibrin formation and a changed fibrinolytic activity, neither in arm nor in leg vein blood. TAT, PAP, and PAI-1 remained unchanged, and the increases of F1 + 2 in arm veins and of d-dimer in leg veins were within the upper reference limits. Moreover, there was no evidence of activation of coagulation as measured by thrombelastography 0049-3848/$ -see front matter D
European Journal of Vascular and Endovascular Surgery, 2006
This review concluded that venous thromboembolism and oedema on long haul flights seem to be reduced with the use of class I and II below-knee graduated compression stockings. Aspirin is not useful, but low molecular weight heparin and profibrinolytics may be; further research is required. It is difficult to properly assess the reliability of this conclusion from the information presented. Authors' objectives To quantify the risk of venous thromboembolism (VTE) following air travel, and to assess the methods of preventing VTE following long haul flights. This summary focuses on the second objective. Searching PubMed, MEDLINE, EMBASE and the Cochrane Library were searched up to November 2004 for English language papers; the search terms were reported. The reference lists of major articles were also checked. Study selection Study designs of evaluations included in the review Randomised controlled trials (RCTs), controlled cohort studies, case-control studies and incidence studies were eligible for inclusion. Specific interventions included in the review Inclusion criteria for the interventions were not specified. The included studies assessed graduated below-knee compression stockings (ranging from 14 to 30 mmHg), low molecular weight heparin (LMWH), aspirin (400 mg once daily for 3 days) and the profibrinolytic agent pinokinase. The comparators were not specified but appeared to be no intervention. Participants included in the review Studies of people who had flown on a long haul flight (more than 6 to 7 hours' duration inside the plane without transit or stopover) were eligible for inclusion. The included studies focused on individuals who were asymptomatic, or at high risk or low-to-medium risk for VTE. Outcomes assessed in the review VTE was the outcome of interest. It was defined as thrombosis of deep, superficial or muscle veins of the lower limbs and pulmonary embolism. Thrombosis of the cerebral and subclavian veins was excluded. All of the included studies used duplex scan to assess the presence of VTE. How were decisions on the relevance of primary studies made? The authors did not state how the papers were selected for the review, or how many reviewers performed the selection. Assessment of study quality The authors did not state that they assessed validity. Data extraction The authors did not state how the data were extracted for the review, or how many reviewers performed the extraction.
Venous Thromboembolism in the Era of Air Travel
Contemporary Cardiology, 2007
The relationship between pulmonary embolism (PE) and air travel remained questionable for a long time, despite the increasing number of passengers on long-distance flights suffering from PE. It was proposed by some authors that the observed occurrence of PE in some individuals after air travel was caused by chance alone. We recently reviewed all documented cases of PE requiting medical care upon arrival at Roissy-Charlesde-Galle, the busiest airport in France. All patients requiring medical care and transport to a hospital because of suspected PE were included, if the diagnosis of PE was confirmed. Between November 1993 and December 2000, 56 patients with confirmed PE were included. All patients had traveled at least 4000 km. The incience of PE increased with the distance traveled, and the risk of PE increased as much as 11-fold after 5000 km. The total incidence of PE reached 4.8 cases per million passengers who traveled distances longer than 7500 km. A similar incidence of PE was found in a cohort of patients arriving at Madrid airport. As the role of other predisposing (risk) factors remains uncertain, the risk of suffering PE cannot be directly determined for each passenger. We therefore believe that risk assessment with regard to air-travel-related PE should take into account the usual predisposing conditions for PE in the general population. Given the risk associated with long-duration air travel, prophylactic measures should always be considered. Behavioral and mechanical prophylaxis, including use of graduated compression stockings and minor physical activity, are currently recommended, because they are safe, easy to apply, and inexpensive. Pharmacological prophylaxis also has been discussed.
Deep vein thrombosis and air travel: record linkage study
BMJ, 2003
Objective To investigate the time relations between long haul air travel and venous thromboembolism. Design Record linkage study using the case crossover approach. Setting Western Australia. Participants 5408 patients admitted to hospital with venous thromboembolism and matched with data for arrivals of international flights during 1981-99. Results The risk of venous thromboembolism is increased for only two weeks after a long haul flight; 46 Australian citizens and 200 non-Australian citizens had an episode of venous thromboembolism during this so called hazard period. The relative risk during this period for Australian citizens was 4.17 (95% confidence interval, 2.94 to 5.40), with 76% of cases (n = 35) attributable to the preceding flight. A "healthy traveller" effect was observed, particularly for Australian citizens. Conclusions The annual risk of venous thromboembolism is increased by 12% if one long haul flight is taken yearly. The average risk of death from flight related venous thromboembolism is small compared with that from motor vehicle crashes and injuries at work. The individual risk of death from flight related venous thromboembolism for people with certain pre-existing medical conditions is, however, likely to be greater than the average risk of 1 per 2 million for passengers arriving from a flight. Airlines and health authorities should continue to advise passengers on how to minimise risk.
Risk of Venous Thromboembolism After Air Travel
Archives of internal medicine, 2003
Background: Conflicting data are available on air travel as a risk factor for venous thromboembolism. To our knowledge, there are no studies investigating whether individuals with thrombophilia and those taking oral contraceptives are more likely to develop venous thromboembolism during flights than those without these risk factors. Participants and Methods: The study sample consisted of 210 patients with venous thromboembolism and 210 healthy controls. DNA analysis for mutations in factor V and prothrombin genes and plasma measurements of antithrombin, protein C, protein S, total homocysteine levels, and antiphsopholipid antibodies were performed. Results: In the month preceding thrombosis for patients, or the visit for controls, air travel was reported by 31 patients (15%) and 16 controls (8%), with an oddsratio of 2.1 (95% confidence interval, 1.1-4.0).
The association between air travel and deep vein thrombosis: Systematic review & meta-analysis
BMC Cardiovascular Disorders, 2004
Background Air travel has been linked with the development of deep vein thrombosis (DVT) since the 1950s with a number of plausible explanations put forward for causation. No systematic review of the literature exploring this association has previously been published. Methods A comprehensive search was undertaken (Data bases searched were: MEDLINE, EMBASE, Cochrane Library) for studies that estimated both the incidence and the risk of DVT in air travellers relative to non-air travellers. Results In total 254 studies were identified but only six incidence studies and four risk studies met inclusion criteria justifying their use in a systematic review. Incidence of symptomatic DVT ranged from (0%) in one study to (0.28%) which was reported in pilots over ten years. The incidence of asymptomatic DVT ranged from (0%) to (10.34%). Pooled odds ratios for the two case control studies examining the risk of DVT following air travel were 1.11 (95% CI: 0.64–1.94). Pooled odds ratios for all models of travel including two studies of prolonged air travel (more than three hours) were 1.70 (95% CI: 0.89–3.22). Conclusion We found no definitive evidence that prolonged (more than 3-hours) travel including air travel, increases the risk of DVT. There is evidence to suggest that flights of eight hours or more increase the risk of DVT if additional risk factors exist.
South African medical journal = Suid-Afrikaanse tydskrif vir geneeskunde, 2003
BACKGROUND As many as 10% of airline passengers travelling without prophylaxis for long distances may develop a venous thrombosis. There is, however, no evidence that economy class travellers are at increased risk of thrombosis. OBJECTIVES A suitably powered prospective study, based on the incidence of deep-vein thrombosis (DVT) reported in previous studies on long-haul flights, was designed to determine the incidence of positive venous duplex scans and D-dimer elevations in low and intermediate-risk passengers, comparing passengers travelling in business and economy class. PATIENTS/METHODS Eight hundred and ninety-nine passengers were recruited (180 travelling business class and 719 travelling economy). D-dimers were measured before and after the flight. A value greater than 500 ng/ml was accepted as abnormal. A thrombophilia screen was conducted which included the factor V Leiden mutation, the prothombin 20210A mutation, protein C and S levels, antithrombin levels, and anticardiol...
Thrombosis Journal
Background Air travel thrombosis continues to be a controversial topic. Exposure to hypoxia and hypobaric conditions during air travel is assumed a risk factor. The aim of this study is to explore changes in parameters of coagulation, fibrinolysis and blood flow in a rat model of exposure to hypobaric conditions that imitate commercial and combat flights. Methods Sixty Sprague-Dawley male rats, aged 10 weeks, were divided into 5 groups according to the type and duration of exposure to hypobaric conditions. The exposure conditions were 609 m and 7620 m for 2 and 12 h duration. Blood count, thrombin– antithrombin complex, D-dimer, interleukin-1 and interleukin-6 were analyzed. All rats went through flight angiography MRI at day 13-post exposure. Results No effect of the various exposure conditions was observed on coagulation, fibrinolytic system, IL-1 or IL-6. MRI angiography showed blood flow reduction in lower limb to less than 30% in 50% of the rats. The reduction in blood flow was...