Mass tourism is booming and foreign travel in particular is steadily growing in popularity. This trend has been accompanied in recent years by a marked rise in the incidence of life-threatening traveller's thrombosis which can unexpectedly assail travellers previously in the best of health. A study conducted by Heathrow Airport has shown that every 5th sudden death following a long-distance flight is caused by pulmonary embolism secondary to traveller's thrombosis.
The main risk factors for developing traveller's thrombosis during long-distance flights are the cramped conditions of most aircraft, the resulting lack of exercise and the sitting position with the knees bent. Further thrombosis promoting factors are the hypoxia prevailing in aircraft, exsiccosis and the use of hypnotics to combat jet lag on transcontinental flights. With the aim of establishing prophylactic guidelines and improving the definition and differentiation of the clinical syndrome of traveller's thrombosis, the Austrian Air Passengers' Medical Service has set up the "Traveller's Thrombosis" data bank. Fifty-two patients have so far been included and their questionnaire data analyzed. These are the main results:
Contrary to previous opinion, not only elderly persons are especially predisposed to develop thrombosis during air, train or automobile journeys lasting several hours; 21% of the patients recorded in the data bank were not yet over the age of 40.
The high risk potential of traveller's thrombosis is demonstrated by the fact that more than one third of those affected suffered a pulmonary embolism, in two cases with fatal outcome (3.8%). Most patients (65.3%) developed an isolated deep venous thrombosis of the lower extremities. The mean latent period between the end of the journey and the onset of disease symptoms was 2.4 days (0-20 days).
Pre-existing risk factors could only be evaluated in 53.8% of the patients: in 11 cases these were venous diseases and in 17 cases other factors such as hormone treatment or hypnotic medication, nicotine abuse and recent surgery.
The results of the study were condensed into general guidelines at a consensus conference:
1. Traveller's thrombosis is a potential complication during journeys lasting several hours and can affect all adults regardless of age. The risk, however, increases with age.
2. The following criteria may be established for the diagnosis of traveller's thrombosis: absence of symptoms before starting the journey, in particular no thrombosis, predominantly sitting position for several hours, latent period until presence of the full clinical syndrome not more than two weeks.
3. The prophylaxis recommendations were graded to suit the different risk categories:
- For the slow risk group, which generally includes all adult travellers, behavioural measures such as standing up relatively often, performing leg exercises in the sitting position, isometric muscle contractions and generous fluid intake to combat dehydration.
- Travellers over the age of 40 who already have several risk factors (varicose veins, CVI, obesity, heart failure, pregnancy, oral contraceptives) comprise the intermediate risk group. In addition to the basic measures, these persons should wear calf-length stockings of compression class I to II.
- The high risk group, finally, comprises long-distance travellers with past thromboembolic events, overt malignancy, thrombophilia, plaster cast on one leg and postoperative state. High risk patients are recommended to have pharmacologic prophylaxis with low molecular weight heparin ( 1 x daily subcutaneously from the day of departure to the day of return).
(Source: vasomed 1996: 8: 336-340)
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