Travel Increases Risk of Deep-Vein Thrombosis
By Sally Beattie, MS, RN, CS, GNP
Summary—The risk of developing venous thromboembolic disease (VTED) in association with travel has been described and discussed via case studies for more than half a century. Case-controlled data have been lacking, however, making it difficult for clinicians to identify patients who might be at risk but who do not possess a pre-existing condition or concomitant disease that might predispose to such an occurrence. A recent group of investigators sought to confirm the relationship between travel and risk of VTED via a case-controlled study and to determine the main features of post-travel VTED.1 A history of journeys lasting more than four hours, regardless of means, appears to be an independent risk for developing VTED. Post-travel VTEDs were not confined to a specific location, nor did they involve any particular predisposition. Primary care providers need to discuss preventive measures with all patients, even those planning short journeys.
The association between long journeys and the occurrence of deep-vein thrombosis (DVT) and/or pulmonary embolus (PE) became suspect after the relationship of venous stasis to venous clot formation was described in 1856. In 1940, studies established a link between the sitting position and risk of developing a DVT and/or PE.2,3 Subsequently, case reports and retrospective studies appeared in the literature describing the occurrence of DVT and PE following prolonged travel. This type of data poses inherent limitations in addressing critical questions about the entity and in making generalizations applicable to a broad population. A group of French investigators sought to clarify the issues by conducting a case-controlled study to determine if travel represents a risk factor for VTED and the principal characteristics, (e.g. type, duration) if any, of travel related to the onset of VTED.1
Study Methodology
From July 1992 to August 1995, 160 adult patients (age 65.3 ± 17.0) admitted consecutively at one hospital for VTED completed a 300-item questionnaire. Special attention was paid to all known risks or suspected risk factors, and in particular to recent travel. All journeys made during the previous four weeks, by whatever means and lasting longer than four hours were considered. Twelve questions dealt specifically with a previous history of travel (reason, means of transport, distance, and duration). In addition, questions were asked about the circumstances or pre-existing conditions that may have favored and induced the DVT, as well as investigations into unknown causes (See table, below, showing circumstances that predispose for VDT associated with travel.) To avoid distortions due to questionable recollection, the questions were asked two times: during the first few days after hospitalization and before discharge. An age-matched control group (n=160), hospitalized concurrently for a first event other than VTED, completed the same questionnaire. Selection bias in this group was averted by excluding those with severe disease that may have resulted in limited mobility as well as those on anticoagulant or antiplatelet therapy.
Study Results
Seventy-nine study group patients experienced VTED under well-defined circumstances such as prolonged bed rest, known cancer, or during a post-surgery period. No predisposing circumstance was found in the remaining 81 patients. A recent journey had been undertaken in 24.5% (39) of the study cases: nine by plane, 28 by car, and two by train for a total mean travel time of 5.7 ± 2.1 hours. In the control group, a recently completed journey was found in 7.5% (12) of cases. Among the 39 study patients hospitalized for VTED who reported recent travel, no other etiologic circumstance or concomitant disease was found in 75% (29 of 39) of the cases. Finally, there was no difference in venous clot site between the right and left lower extremity, nor was there any difference in clot site between the study and control groups of patients with DVT.
Based on these results, the investigators concluded that travel lasting at least four hours, regardless of means, represents a risk factor for the development of VTED. They acknowledged that their results represented a relatively high rate of post-travel DVT compared to previous reports in the literature and cited the proximity of their hospital to a large airport populated with tourists as a potentially contributing factor. In addition, the previously reported 3-17% incidence of travel-related DVTs was cited in retrospective studies without the benefit of sufficient and detailed investigations, and often journeys responsible for DVT formation exceeded 10 hours.4,5
Table 2. Compliance with AMI Quality Indicators by Geographic Region | ||
| Quality Indicators | Lowest | Highest |
| Aspirin prescribed during hospitalization | South Central, Southeast | Most regions |
| Aspirin prescribed at hospital discharge | Very few areas | Northeast, North Central, Mountain |
| Reperfusion using thrombolytics or primary PTCA during first 12 hours of hospitalization | South Central, Mid-Atlantic | Scattered areas |
| Beta-blocking agents prescribed at hospital discharge | South Central, Southeast | Northeast, North Central |
| ACE inhibitors prescribed at hospital discharge | No pattern | No pattern |
| CCB agents withheld at hospital discharge for patients with poor left ventricular function | No pattern | No pattern |
| Smoking cessation advice given to current cigarette smokers | South Central, Southeast | Alaska, Mountain states |
Practice Implications
Primary health care providers are well aware of the need to educate patients with a known risk for DVT and/or PE to avoid prolonged periods of sitting and immobility. However, this study suggests that journeys longer than four hours may, by themselves, constitute a risk for the development of DVT in otherwise healthy individuals. Studies dealing with the epidemiology of DVET have reported an increase in unexplained or "idiopathic" DVT and/or PE that may be understood, in part, by the increase in travel in modern Western society. Until further investigation into this phenomenon provides a specific risk profile for the development of DVET associated with travel, clinicians need to discuss venous stasis and its prevention with all adult patients planning journeys involving prolonged sitting and immobility, including:6-7
• frequent ankle flexion and extension;
• frequent changing of position;
• periodic standing and ambulation;
• and adequate hydration.
References
1. Ferrari E, Chevallier T, Chapelier A, Baudouy M. Travel as a risk factor for venous thromboembolic disease. Chest 1999;115:440-444.
2. Virchow R. Gesammelte abhandlungen zur wissenschaftlischen. In: Meidinger, ed. Medicine. Frankfurt, Germany: 1856, p. 227.
3. Simpson K. Shelter deaths from pulmonary embolism. Lancet 1940;2:744.
4. Homans J. Thrombosis of the deep leg veins due to prolonged sitting. N Engl J Med 1954;250:148-149.
5. Beighton PH, Richards PR. Cardiovascular disease in air travelers. Br Heart J 1968;30:367-372.
6. Ferrari E, Baudouy M, Cerboni P, et al. Epidemiology of pulmonary embolism: Results of a French registry. Eur Heart J 1997;18:685-691.
7. Prandoni P, Lensing AW, Buller HR, et al. Deep vein thrombosis and the incidence of subsequent sympto - matic cancer. N Engl J Med 1992;327:1128-1133.
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