In recent months there has been a huge upsurge of articles in the press on Deep Vein Thrombosis in travellers. This subject was sparked off by the death of a young woman in October last year from a clot in the lungs shortly after she had completed a journey from Sydney to London.

The dramatic term "economy class syndrome" was coined 24 years ago and caught on in both medical and lay press but it is an unfortunate misnomer and "travellers thrombosis" is a more accurate description of the association between long distance travel and the possibility of deep vein thrombosis.

Deep Vein Thrombosis (DVT) refers to the formation of a clot or thrombosis in the deep veins of the calf or other non superficial vein. The symptoms can vary from a mildly uncomfortable ache and swelling to nothing at all. The real worry about DVT is that in a small number of people a piece of the clot can break off and travel in the circulation to the lungs - the medical term is pulmonary embolism - with a reaction that is sometimes fatal.

As long ago as 1940 one of England’s greatest forensic scientists Dr Keith Simpson recorded an increase in cases of pulmonary embolism in people who had sat for a long time in air raid shelters during the London Blitz. He attributed this to people sitting immobile in a cramped position for long periods. Certainly such a description can apply to modern passengers on long haul flights where, to quote Stacy Greg writing in the Sunday Times "aircrafts serve as a flying cattle-pen for the cramped, miserable masses…" and indeed applies just as much to long road or rail journeys.

While some Australian newspaper articles have referred to a projected local meeting to review the evidence, the British House of Lords has already tabled a full and extensive report from a Select Committee chaired by Baroness Wilcox in November last. Significantly in the summary to the report the Committee commented "while we acknowledged the possibility that there might be some gaps in knowledge, we were surprised to find that there were so many. In the absence of accessible and authoritative information, it is not surprising that rumour and speculation thrive." They urged that rigorous studies be carried out as soon as possible to allow a more scientific approach to the issue. The Aerospace Medical Association
has responded to the call and prospective studies are planned. Thai authorities have announced that they are conducting studies. No doubt there are, and will be, others.

THE PROBLEM: Is the relationship Causal or Casual? If travelling is causal, how much does it contribute to the development of DVT.

DVT is not a rare condition. Up to 20% of the population is thought to have conditions within the circulation which would make clot formation easy, and the underlying incidence of DVT in the population as a whole increases with increasing age, averaging an overall rate of around 1 in 10 000 people per year.
To quote once again from the Wilcox report: ‘The fundamental question yet to be answered is whether this number [of travellers who get thrombosis] is greater than the number from an equivalent population who would have developed DVT if they had not recently flown’. An editorial review in the British Medical Journal stated as recently as 27 January this year: "current evidence indicates that any association between symptomatic deep vein thrombosis and air flights is weak and its incidence much less than the impression given by the recent publicity."

Nevertheless the publicity cannot be ignored - many passengers are worried that long distance travel can be dangerous, coroners’ reports from areas near Heathrow in England and Nerita in Japan imply that this is true, many vascular surgeons seem to be convinced and the theoretical reasons why long haul travel could predispose to clot formation make sense.

WHAT SHOULD TRAVELLERS MAKE OF THE CURRENT DISCUSSION?

In the first place it must be emphasised that what is thought to be the main underlying cause for DVT is prolonged immobility in the sitting position, so long haul bus or train travel is as much a risk as plane travel. Undoubtedly there are medical conditions which predispose to clot formation and nothing replaces pre-travel medical advice.

The Wilcox Committee makes logical recommendations classifying travellers into four groups:

1. Those with no known predisposing factors

• Move around as much as possible


• Exercise calf muscles whilst seated with half hourly flexing and rotating of ankles


• Avoid excessive alcohol and caffeine containing drinks, both before and during the flight


• Drink only water or juices when thirsty

2. Those at minor risk (aged over 40, very tall, obese, extensive varicose veins, recent minor leg surgery or minor body surgery, previous or current leg swelling from any cause)

• As above plus


• Take only short periods of sleep, unless you can lie down


• Avoid sleeping pills


• Consider wearing support stockings

3. Those at moderate risk (recent heart disease, pregnant or on any hormone medication, recent major leg injury or leg surgery, family history of DVT)

• As above plus


• Take professional advice about risk involved


• Take professional advice about the need to wear compression stockings

4. Those at substantial risk (previous DVT, known clotting tendency, recent
major surgery, current malignant disease, paralyzed lower limbs)

• All the above plus low molecular weight heparin injections.

A WORD OR TWO ON ASPIRIN

Many travellers are already taking aspirin in an attempt to prevent thrombosis. A couple of studies have been published that showed a very small advantage in taking aspirin after hip replacement surgery - a totally different group of patients from the average traveller. If this group of patients at high risk showed such a small decrease in incidence of DVT one would expect the effect in travellers to be minute. Taking aspirin could lead to a false sense of security ie that you would think you are doing something to prevent thrombosis when in fact you are probably doing nothing. Aspirin could increase any tendency to nose bleeding at altitude and of course must not be used in the presence of any digestive disorders. Additionally, as aspirin is an anti-inflammatory it may mask the symptoms of a DVT and subsequently result in a delayed diagnosis. Those that fit into higher risk categories will do better to get advice on compression stockings or the possibility of heparin injections.

COMPRESSION STOCKINGS

Proper compression stockings are designed to transmit graduated pressure and should be individually fitted. If this is not possible they can be ordered if the suppliers are given height and weight measurements. They are not cheap but the expense is small in the total context of travel expenses and in high risk cases could be the difference between health and illness. In those who are troubled by ankle and foot swelling after air journeys they can make travel much more comfortable.

Further information may be obtained by visiting one of the Travel Doctor Clinics around Australia or overseas. In Australia a booking may be made on 1300 65 88 44.