"Long haul" flight and deep vein thrombosis: a model to help investigate the benefit of aspirin and below-knee compression stockings

Low molecular weight heparin and aspirin for prevention of deep vein thrombosisafter orthopaedic surgery: a systematic review and meta-analysis

To comprehensively evaluate the clinical effects of low molecular weight heparin (LMWH) and aspirin for deep vein thrombosis (DVT) patients after orthopaedic surgery. Studies comparing LMWH and aspirin were retrieved in multiple databases. Review Manager 5.0 was adopted for meta-analysis, sensitivity analysis and bias analysis. Finally, 4460 patients in 6 studies were included, and the eligibility criteria were finally met. The meta-analysis suggested that there was significant difference between LMWH and aspirin groups in DVT (RR = 0.58, 95%CI [0.39, 0.88], P = 0.01; P for heterogeneity = 0.45, I² = 0%). Postoperative bleeding between the two groups showed no difference (RR = 2.20, 95%CI [0.48, 10.09], P = 0.31; P for heterogeneity = 0.79, I² = 0%) This study shows that LMWH is a more effective therapy than aspirin for patients with DVT after orthopaedic surgery.

The association between seated immobility and local lower-limb venous coagulability in healthy adult volunteers: a simulation of prolonged travel immobility

This is the first study to examine the hypothesis that prolonged sitting is associated with procoagulant changes in the local lower-limb venous system. A comparison was made with upper-limb venous changes. Changes in markers of thrombin generation, fibrinolysis, endothelial perturbation and haemoconcentration were analysed as 10 healthy adult male participants sat for 8 h. The change in foot volume was estimated. Subjective venous thromboembolism assessment was undertaken hourly, along with 2-week and 4-week safety follow-up for clinical events. Expected increases in median prothrombin fragments 1 and 2, thrombin-antithrombin complex and D-dimer were not observed in either limb. An increase greater than 45% in the median tissue plasminogen activator and plasminogen activator-1 molar ratio (t-PA/PAI-1), and a decrease greater than 15% in median soluble thrombomodulin were noted in both limbs. Median haematocrit decreased minimally (1%) in the lower limbs, while the foot volume increased by 4%. Subjects experienced vague symptoms after 6 h of sitting, but none developed symptomatic venous thromboembolism. Upper and lower-limb changes in biomarkers did not correlate, except those in t-PA/PAI-1 ratio and plasminogen activator-1. Significant correlation was found between changes in the lower-limb t-PA/PAI-1 ratio and right foot volume. This study originally reveals that even in the lower limbs, prolonged daytime cramped sitting is not associated with significant procoagulant changes in healthy adult male volunteers, and confirms a previous observation that local lower-limb venous changes are not identically reflected in the upper limbs.

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.

Prolonged seated immobility-associated venous coagulability in a factor V Leiden heterozygote: a case-comparative study

Prolonged sitting and thrombophilia may compound the risk of venous thromboembolism. In order to investigate suspected local lower limb venous procoagulant changes associated with prolonged sitting-induced venous stasis in a man heterozygous for factor V Leiden (participant X), we qualitatively compared venous coagulability in lower and upper limb plasma in this participant and three other male Caucasians over 8 h of sitting. Of the four participants, participant X had the highest baseline values of prothrombin fragments 1 and 2, thrombin-antithrombin III complexes, tissue plasminogen activator, plasminogen activator inhibitor 1, D-dimer and soluble thrombomodulin. Over time, in participant X, venous prothrombin fragments 1 and 2, thrombin-antithrombin III complexes, and soluble thrombomodulin decreased in both limbs; D-dimer decreased in the lower limbs but increased in the upper limbs; the tissue plasminogen activator/plasminogen activator inhibitor 1 molar ratio increased in both limbs; and minimal changes were noted in haematocrit. A foot volume increase was associated with vague symptoms towards the end of the study. Overall, these changes were similar to those observed in other participants. It is concluded from this case comparison that prolonged sitting of 8 h duration under normal atmospheric conditions did not result in local, as well as systemic, procoagulant haemostatic responses in a heterozygote for factor V Leiden when compared with other healthy volunteers. However, this observed, possibly adaptive, response is more likely to be compromised in factor V Leiden subjects during continued or increased venous endothelial stress or in the presence of other venous thromboembolism risk factors.

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

OBJECTIVES

To quantify the risk of venous thromboembolism (VTE) following air travel and assess methods of prevention.

DESIGN

Review of literature.

METHODS

We reviewed Pubmed, Medline, Embase and Cochrane Databases for studies that have assessed the risk of VTE associated with air travel.

RESULTS

There is an association of VTE with air travel with pooled odds ratio of 1.59 (confidence interval 1.04-2.43) from three case control studies and relative risk of 2.93 (confidence interval 1.5-5.58) from two controlled cohort studies. The incidence of symptomatic pulmonary embolism (PE) is extremely low but there is substantial increase when the distance travelled is more than 5,000 miles (1.5 PE per million passengers) or time of flight is more than 8h duration (2.57 PE per million passengers). The quantitative risk of lower limb venous thrombosis in high-risk subjects is 5% per flight and 1.6% per flight for low risk subjects following long haul flights. All six randomised trials to test the below knee compression stockings with ankle pressures of 14-30 mmHg have shown reduction in lower limb venous thrombosis.

CONCLUSION

VTE is more common in those with additional risk factors when the risk is about 5% per air travel for long haul flights. Class I or II below knee compression stockings are effective in the prevention of lower limb venous thrombosis.

Graduated compression stockings as prophylaxis for flight-related venous thrombosis: systematic literature review

AIM

This paper reports a systematic review whose objective was to evaluate the effectiveness of graduated compression stockings as prophylaxis for flight-related venous thrombosis, including deep vein thrombosis and superficial venous thrombosis, after air travel in the general population.

BACKGROUND

Despite the extended history of the use of graduated compression stockings, their application to prevent flight-related thrombosis was not explored until flight-related thrombosis was perceived as a preventable illness. Even now, their effectiveness in preventing flight-related thrombosis remains unresolved.

METHODS

Generic terms including stocking/s, sock/s, or hosiery/hosieries were used to search a variety of electronic databases. Based on the selection criteria, decisions regarding inclusion and exclusion of primary studies were made. Using a meta-analysis software program, relative risk for the incidence of deep vein thrombosis, superficial venous thrombosis, and intention-to-treat analysis was calculated.

RESULTS

A total of nine randomized controlled trials were included. In the treatment group, two of 1237 participants developed deep vein thrombosis in comparison with 46 of 1245 in the control group. The weighted relative risk for deep vein thrombosis was 0.08, with fixed 95% confidence interval 0.03-0.23. In the treatment group, four of 826 participants developed superficial venous thrombosis in comparison with seven of 823 in the control group. The weighted relative risk for superficial venous thrombosis was 0.67. with fixed 95% confidence interval 0.24-1.87 (non-significant difference). Using intention-to-treat analysis, the risk for participants in the treatment group was 0.53 times as great as that for those in the control group.

CONCLUSIONS

This review demonstrates the effectiveness of medium compression pressure, below-knee graduated compression stockings in preventing flight-related deep vein thrombosis but not superficial venous thrombosis in low-medium- or high-risk participants.

Endovascular management of venous thrombotic diseases of the upper torso and extremities

Central venous thrombosis in the upper torso can be either primary, occurring as a result of longstanding extrinsic compression, or secondary, resulting from an acquired intrinsic occlusive disease or foreign body. As in lower extremity deep vein thrombosis (DVT), anticoagulation therapy is the mainstay of therapy in upper torso and upper extremity DVT. However, in the presence of severely symptomatic acute thrombosis, pharmacologic and/or mechanical thrombolytic therapy represent the main invasive form of therapy for these conditions. After clearance of the acute thrombotic component, definitive management in patients with underlying anatomic abnormalities can be undertaken. Primary subclavian axillary vein thrombosis caused by extrinsic obstruction at the thoracic outlet is treated with thrombolytic therapy and anticoagulation followed by surgical decompression, whereas secondary causes of central venous obstruction and thrombosis are usually amenable to endovascular treatment with balloon angioplasty and stent placement. Postoperative interval anticoagulation is usually recommended. In addition to clinical follow-up, imaging follow-up with duplex sonography or conventional venography is usually recommended to assess the presence of restenosis and/or residual compression.