Venous Thromboembolic Complications Following Air Travel: What's the Quantitative Risk? A Literature Review

Management of venous thromboembolism in athletes

Venous thromboembolism (VTE) is a common condition with high associated morbidity and mortality. Athletes have unique VTE risk factors compared with the general population, and may have a higher than anticipated risk of thrombosis. Anticoagulant treatment poses additional challenges in athletes, as these individuals usually wish to return to sporting activities without delay. In addition, those athletes who engage in contact sports may have bleeding complications with extended anticoagulation. In this paper, we discuss VTE risk factors in athletes, the impact of exertion on haemostasis, measures which could be adopted to mitigate VTE risks in these highly active individuals and options to deal with bleeding risks from anticoagulation during injury-prone sporting activities.

The effect of civil and military flights on coagulation, fibrinolysis and blood flow: insight from a rat model

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 more pronounced in the left vessel than in the right vessel (p = 0.006, Wilcoxon signed rank test). The extent of occlusion differed across exposure groups in the right, but not the left vessel (p = 0.002, p = 0.150, respectively, Kruskal-Wallis test). However, these differences did not correlate with the exposure conditions.

Conclusion

In the present rat model, no clear correlation between various hypobaric conditions and activation of coagulation was observed. The reduction in blood flow in the lower limb also occurred in the control group and was not related to the type of exposure.

Psoriatic and psoriatic arthritis patients with and without jet-lag: does it matter for disease severity scores? Insights and implications from a pilot, prospective study

Background: Jet-lag may affect air-travelers crossing at least two time-zones and has several health-care implications. It occurs when the human biological rhythms are out of synch with respect to the day-night cycle at the country destination. Its effect in psoriasis is missing. We aimed to evaluate the effect of Jet-lag in psoriatic patients' management. Methods: This is a prospective observational study that enrolled psoriatic patients that underwent a flight: patients who experienced jet-lag were compared to patients who did not experience jet-lag. Before the flight, a dermatologist recorded clinical and demographical data with particular attention to Psoriasis Area Severity Index (PASI) and Disease Activity in Psoriatic Arthritis (DAPSA). Patients performed Self-Administered Psoriasis Area Severity Index (SAPASI), the Dermatology Life Quality Index (DLQI) and the pruritus Visual Analog Scale (VAS) scores. After the flight, patients completed the SAPASI, DLQI and pruritus-VAS scores. Results: The sample recruited comprised of 70 psoriatic patients aged 42.4 ± 9.7 years (median 42.5 years). Thirty (42.9%) were males, mean BMI was 25.5 ± 2.2 kg/m2. Average disease duration was 15.2 ± 7.1 years, and 20 (28.6%) subjects had developed PsA. Average hours of flight were 5.4 ± 3.5 (median 3.5 h), with 34 (48.6%) subjects reporting jet-lag. At the multivariate regression analysis, the change in the SAPASI score resulted correlated with jet-lag (regression coefficient 1.63, p = .0092), as well the change in the DLQI score (regression coefficient = 1.73, p = .0009), but no change on the pruritus VAS scale was found. Conclusions: The present study suggests that jet-lag may influence disease severity and DLQI scores, but not itch in psoriatic patients.

In-Flight Medical Emergencies: A Review

IMPORTANCE

In-flight medical emergencies (IMEs) are common and occur in a complex environment with limited medical resources. Health care personnel are often asked to assist affected passengers and the flight team, and many have limited experience in this environment.

OBSERVATIONS

In-flight medical emergencies are estimated to occur in approximately 1 per 604 flights, or 24 to 130 IMEs per 1 million passengers. These events happen in a unique environment, with airplane cabin pressurization equivalent to an altitude of 5000 to 8000 ft during flight, exposing patients to a low partial pressure of oxygen and low humidity. Minimum requirements for emergency medical kit equipment in the United States include an automated external defibrillator; equipment to obtain a basic assessment, hemorrhage control, and initiation of an intravenous line; and medications to treat basic conditions. Other countries have different minimum medical kit standards, and individual airlines have expanded the contents of their medical kit. The most common IMEs involve syncope or near-syncope (32.7%) and gastrointestinal (14.8%), respiratory (10.1%), and cardiovascular (7.0%) symptoms. Diversion of the aircraft from landing at the scheduled destination to a different airport because of a medical emergency occurs in an estimated 4.4% (95% CI, 4.3%-4.6%) of IMEs. Protections for medical volunteers who respond to IMEs in the United States include a Good Samaritan provision of the Aviation Medical Assistance Act and components of the Montreal Convention, although the duty to respond and legal protections vary across countries. Medical volunteers should identify their background and skills, perform an assessment, and report findings to ground-based medical support personnel through the flight crew. Ground-based recommendations ultimately guide interventions on board.

CONCLUSIONS AND RELEVANCE

In-flight medical emergencies most commonly involve near-syncope and gastrointestinal, respiratory, and cardiovascular symptoms. Health care professionals can assist during these emergencies as part of a collaborative team involving the flight crew and ground-based physicians.

[Thromboembolic risk in repatriated patients with traumatic lower-limb injuries]

INTRODUCTION

Venous thromboembolism (VTE) is a public health problem. Medical repatriation of patients with traumatic lower-limb injuries is common. There are no specific recommendations for the prevention of deep vein thrombosis (DVT). The main objective was to determine the incidence of VTE in this high-risk population and to determine associated risk factors.

MATERIALS AND METHODS

This was a prospective study including patients repatriated to France following lower-limb trauma and hospital discharge. A physical examination and a venous ultrasound were systematically performed on arrival. Reasons for repatriation, methods of VTE prevention and risk factors for VTE were studied. The positive diagnosis of deep venous thrombosis (DVT) was done by Doppler ultrasound.

RESULTS

Fifty-two patients with lower-limb trauma were included. Six cases of DVT, four asymptomatic and two symptomatic with pulmonary embolisms were diagnosed. Two patients with asymptomatic DVT did not have preventive anticoagulation. No patient with preventive anticoagulation had symptomatic DVT. Smoking and the absence of preventive anticoagulation were significant risk factors for VTE.

DISCUSSION

Repatriation of patients with lower-limb trauma in discharge is associated with an increased risk of VTE. Preventive anticoagulation appears to be effective in preventing DVT. Systematic Doppler imaging can reveal asymptomatic DVT. Our study did not evaluate specifically the interest of venous compression associated to preventive anticoagulation for VTE prevention. Specific recommendations on VTE prevention during repatriation of patients with lower-limb trauma are needed.

CONCLUSION

Preventive anticoagulation should be systematically discussed during repatriation of patients with lower-limb trauma, in the absence of major bleeding risk. Due to the existence of asymptomatic DVT, venous Doppler ultrasound should also be systematically discussed despite the absence of official recommendations.

Etiopathogenesis, Prevention, and Treatment of Thromboembolism in Inflammatory Bowel Disease

The close relationship between inflammation and thrombosis affects the progression and severity of inflammatory bowel disease (IBD). The prevalence of venous thromboembolism (VTE) varies between 1% and 7% among patients with IBD. The VTE risk in patients with IBD is at least 3 times higher than that in the normal general population. The absolute risk is very high during hospitalization, active disease, and surgery. The IBD-related VTE occurs at younger ages and recurs more frequently. The development of thrombosis in IBD is due to the interaction of many hereditary and acquired risk factors. Each patient diagnosed with IBD should be evaluated for a personal and family history of thrombosis and for prothrombotic drug use. Although procoagulant factors are increased during the natural course of inflammation, natural anticoagulants and fibrinolytic activity are decreased. Although IBD is accepted as a prothrombotic condition, there is no treatment that can remove this risk from daily practice. Patient training is required to control important factors, such as long-term immobilization and smoking. Oral contraceptives and hormone replacement therapy should be avoided. Inducing permanent disease remission must be the key approach for the prevention of thrombosis. Low-molecular-weight heparin (LMWH) is the basis of prophylactic treatment, which reduces the thrombosis risk by 50%. Prophylaxis with LMWH should be administered to all patients with IBD hospitalized due to disease attack or surgery. Long-term or even life-long anticoagulation therapy should be planned if there is insufficient disease control, recurrent VTE attacks, positive thrombophilia tests, or thrombosis in vital veins.

Rediscussing Anticoagulation in Distal Deep Venous Thrombosis

BACKGROUND

Distal deep venous thrombosis (DVT) accounts for approximately half of all the cases of lower limb thrombosis. The impact and management of this condition is still controversial. This study aims to evaluate the incidence of pulmonary embolism (PE) in patients with distal DVT in comparison to proximal DVT and evaluate the correlation between DVT and PE extension.

METHODS

100 patients with acute lower limb DVT diagnosed with whole leg Doppler ultrasound from January 2006 to December 2014 were retrospectively analyzed. Active investigation for PE was carried out in all patients using multislice computed tomography angiography. Classification of DVT and PE was based on the proximal extension of the thrombus.

RESULTS

The overall incidence of PE in our sample patients was 72%. In the subgroup analysis, incidence of PE was equal in both the proximal and distal DVT groups (77%, p > 0.99). PE was detected in 43% of the patients with isolated calf vein thrombosis (ICVT). No statistical difference was observed between the distribution of lobar, segmental and subsegmental PE in the 3 DVT subgroups (p = 0.665); however, truncular PE was only observed in the proximal DVT group.

CONCLUSION

Distal DVT is associated with a high incidence of PE compared to proximal DVT. Distal DVT and ICVT can provoke PE with involvement of proximal vessels in the pulmonary arterial tree, even in asymptomatic patients. Our study arises discussion in the controversial debate regarding the need for routine anticoagulation in distal DVT.

Venous and arterial disease in inflammatory bowel disease

Awareness is increasing that risk of venous thromboembolism and development of atherosclerosis is elevated in patients with some chronic inflammatory diseases. This review aimed to examine the risk of vascular disease in patients with inflammatory bowel disease (IBD) and to identify potential pathogenic mechanisms and therapeutic approaches. An extensive literature search was conducted using MEDLINE database, Cochrane Library and international conference abstracts for studies pertaining to venous and arterial thromboembolism in adult IBD patients. There is a 1.1-3.6 fold risk of venothromboembolism in IBD, affecting 0.55-6.15% of patients. Risks are increased during a flare or with chronically active inflammation. Evidence is building that there may be a modestly increased risk of arterial disease overall, despite evidence that traditional risk factors may be reduced. Multiple pathogenic factors have been identified including endothelial dysfunction, inflammation-mediated calcium deposition in the media of arteries, hyperhomocysteinemia, platelet activation, and altered coagulation and fibrinolysis. The key to active and preventive therapy is to effectively treat inflammation. Recommendations for prophylaxis of venothromboembolism have followed guidelines where they exist and have been extrapolated from studies of other at-risk conditions, as have those for arterial disease, where screening for risk factors and actively treating abnormalities is encouraged. In conclusion, patients with IBD are at considerably increased risk of venothromboembolism and probably of arterial disease, in particular mesenteric ischemia and ischemic heart disease. Increased penetration of gaps between this knowledge and clinical therapeutic action to prevent thromboembolic events into IBD clinical practice is needed.

Knee-length graduated compression stockings for thromboprophylaxis in air travellers: A meta-analysis

OBJECTIVE

To systematically review the randomized controlled trials that have evaluated the efficacy of knee-length (KL) compression stockings for thromboprophylaxis in air travellers.

METHOD

After an electronic database search, the randomized controlled trials that studied passengers on long-haul flights were selected and analyzed to generate summative data.

RESULTS

Nine trials studying participants using KL stockings were analyzed. Forty-six of 1261 participants randomly assigned to the control group developed deep vein thrombosis (DVT), compared with two of 1237 participants (0.16%) in the KL stockings group. The weighted risk difference was -0.034, which indicated that the absolute difference was 3.4% in the incidence of DVT, in favour of KL stockings. The number needed to treat with KL stockings to avoid one case of DVT was 29.4. However, there was significant heterogeneity among trials. The RR for DVT was 0.08 in high-risk participants and 0.14 in low- to medium-risk participants.

CONCLUSION

KL stockings are effective for thromboprophylaxis in air travellers at low, medium and high risk of DVT. The use of KL stockings should form an important part of air traveller education on lowering the burden of DVT. The results of the present meta-analysis can be used to advise travellers on their risk of DVT and preventive strategies.

Lower extremity venous thrombosis in patients younger than 50 years of age

Aim

Lower extremity deep venous thrombosis in the young adult is uncommon and has not been well studied in the literature. The aim of this study is to define risk factors for deep venous thrombosis among patients younger than 50 years of age, to compare them with a control group, and to suggest recommendations for the management and treatment of venous thrombosis in this particular group of patients.

Methods

From January 2003 to January 2011, 66 consecutive Lebanese patients (29 males and 37 females) younger than 50 years, diagnosed in an academic tertiary-care center with lower extremity deep venous thrombosis by color flow duplex scan, were retrospectively reviewed. Their age varied between 21 and 50 years (mean 38.7 years). The control group included 217 patients (86 males and 131 females) older than 50 years (range: 50–96 years; mean 72.9 years).

Results

The most commonly reported risk factors in the younger age group were inherited thrombophilia (46.9% compared with 13.8% in the control group; P < 0.001), pregnancy (18.2% compared with 0.5%; P < 0.001), treatment with estrogen drugs (13.6% compared with 2.3%; P = 0.001), and family history of venous thromboembolism (9.1% compared with 3.8%; P = 0.084).

Conclusion

Inherited thrombophilia is the most commonly observed risk factor among patients younger than 50 years, with a prevalence of three times more than the control group. Young adults should be screened for thrombophilia even in the presence of transient acquired risk factors. Pregnancy and treatment with estrogen drugs essentially when associated with inherited thrombophilia represent a frequent cause of venous thrombosis among young female patients. Inferior vena cava abnormalities should be excluded in young patients with spontaneous proximal venous thrombosis especially when recurrent venous thrombosis or resistance to anticoagulation are observed.

Travel-related thromboembolism: mechanisms and avoidance

Evidence regarding the existence of travel-related venous thrombosis and pulmonary embolism is building. Research suggests that travel of all kinds increases the risk by two- to four-fold. Risks are not restricted to air travel alone. For travelers without any known risk factors, the risk of experiencing venous thromboembolism is likely to be very low. However, risks increase significantly in the presence of known risk factors, such as age over 60 years, thrombophilic disorders, varicose veins, history of thromboembolism, obesity, women taking oral contraceptives and travel duration over 12 h. A combination of one or more of these risk factors raises the probability of developing travel-related thromboembolism. Possible contributing factors, such as cramped sitting (with suppressed leg venous flow), moderate hypoxia, low humidity in the aircraft and dehydration, are discussed. Depending on the risk profile of individuals, the use of graduated compression stockings and/or pharmacological interventions (low-molecular-weight heparins are preferred) may be recommended.

Portable ultrasound for remote environments, part II: current indications

BACKGROUND

With recent advances in ultrasound technology, it is now possible to deploy lightweight portable imaging devices in the field. Techniques and studies initially developed for hospital use have been extrapolated out of the hospital setting in a wide variety of environments in an effort to increase diagnostic accuracy in austere or prehospital environments.

OBJECTIVES

This review summarizes current ultrasound applications used in out-of-hospital arenas and highlights existing evidence for such use. The diversity of applications and environments is organized by indication to better inform equipment selection as well as future directions for research and development.

DISCUSSION

Trauma evaluation, casualty triage, and assessment for pneumothorax, acute mountain sickness, and other applications have been studied by field medical teams. A wide range of outcomes have been reported, from alterations in patient care to determinations of accuracy compared to clinical judgment or other diagnostic modalities.

CONCLUSIONS

The use of lightweight portable ultrasound shows great promise in augmenting clinical assessment for field medical operations. Although some studies of diagnostic accuracy exist in this setting, further research focused on clinically relevant outcomes data is needed.

Medical issues associated with commercial flights

Almost 2 billion people travel aboard commercial airlines every year. Health-care providers and travellers need to be aware of the potential health risks associated with air travel. Environmental and physiological changes that occur during routine commercial flights lead to mild hypoxia and gas expansion, which can exacerbate chronic medical conditions or incite acute in-flight medical events. The association between venous thromboembolism and long-haul flights, cosmic-radiation exposure, jet lag, and cabin-air quality are growing health-care issues associated with air travel. In-flight medical events are increasingly frequent because a growing number of individuals with pre-existing medical conditions travel by air. Resources including basic and advanced medical kits, automated external defibrillators, and telemedical ground support are available onboard to assist flight crew and volunteering physicians in the management of in-flight medical emergencies.

Some chronobiological and physiological problems associated with long-distance journeys

Long-distance travel is becoming increasingly common. Whatever the means of transport, any long journey will be associated with "travel fatigue". The symptoms associated with this phenomenon result from a changed routine (particularly sleep lost and meals) and the general disruption caused by travel. Planning any trip well in advance will minimise many of these problems, but some factors are less easy to guard against. These problems include sitting in cramped and uncomfortable conditions and, with flights, the hypoxic environment in the cabin. After arrival at the destination in another country, there can be problems coping with the local language, alterations in food and different customs. If the flight has crossed the equator, then there is likely to be a change in season and natural lighting and, if it has crossed several time zones, there will also be the problem of "jet lag", caused by a transient desynchrony between the "body clock" and the new local time. Moreover, the new environment might differ from the place of departure with regard to ambient temperature and humidity, altitude, natural lighting (including ultraviolet radiation) and pollution. The traveller needs to be aware of these changes before setting off, so that appropriate preparations (clothing, for example) can be made.

Free tissue transfer and deep vein thrombosis

Reconstruction of the post-oncologic defect of the lower limb frequently requires free tissue transfer and these often extensive bone and soft tissue resections can occasionally be compounded by the presence of a deep venous thrombosis (DVT). We describe two patients in whom free tissue transfer was attempted, following extensive resection of a sarcoma in the thigh. Both patients had been diagnosed with DVT prior to surgery and received therapeutic low molecular weight heparin preoperatively. In the first patient, flap failure occurred due to venous congestion initially resulting from poor flow in the reconstructed femoral vein and then thrombosis and failure of the vascular reconstruction. In the second patient the superficial venous system was used for successful microvascular anastomosis leading to survival of the flap. Therefore, patients undergoing lower extremity free tissue transfer who are at high risk of DVT, or when there is a clinical suspicion of DVT, thorough preoperative assessment of the deep and superficial venous system is warranted for reconstruction planning.

Knee versus Thigh Length Graduated Compression Stockings for Prevention of Deep Venous Thrombosis: A Systematic Review

OBJECTIVE

Graduated compression stockings are a valuable means of thrombo-prophylaxis but it is unclear whether knee-length (KL) or thigh length (TL) stockings are more effective. The aim of this review was to systematically analyse randomised controlled trials that have evaluated stocking length and efficacy of thromboprophylaxis.

METHOD

A systematic review of the literature was undertaken. Clinical trials on hospitalised populations and passengers on long haul flights were selected according to specific criteria and analysed to generate summated data.

RESULTS

14 randomized control trials were analysed. Thirty six of 1568 (2.3%) participants randomised to KL stockings developed a deep venous thrombosis, compared with 79 of 1696 (5%) in the TL control/thigh length group. Substantial heterogeneity was observed amongst trials. KL stockings had a significant effect to reduce the incidence of DVT in long haul flight passengers, odds ration 0.08 (95%CI 0.03-0.22). In hospitalised patients KL stockings did not appear to be far worse than TL stockings, odds ratio 1.01 (95%CI 0.35-2.90). For combined passengers and patients, there was a benefit in favour of KL stockings, weighted odds ratio 0.45 (95% CI 0.30-0.68).

CONCLUSION

KL graduated stockings can be as effective as TL stockings for the prevention of DVT, whilst offering advantages in terms of patient compliance and cost.