News Feature: Giving advice on traveller’s thrombosis

In light of recent media coverage of traveller’s thrombosis, commonly termed “economy class syndrome”, this news feature aims to provide pharmacists with practical advice to give customers before a flight. A study linking air travel with deep vein thrombosis is expected to be published in the next couple of weeks, so media coverage is likely to increase. Clare Bellingham reports

It has been known for many years that immobilisation can lead to the development of deep vein thrombosis (DVT). However, until a number of recent highly publicised deaths, the public was largely unaware that air travel could increase the risk of developing DVT. Although research in the area has produced conflicting results, it is generally believed that air travel can increase the risk of developing DVT if only because it increases factors, such as immobilisation and dehydration, which can increase risk of developing DVT.

At the end of last year, a House of Lords report by the Select Committee on Science and Technology recommended that further research in the area be carried out as soon as possible. It said that no authoritative data were available but gave precautionary advice concerning air travel and DVT (see PJ, December 2, 2000, p811).

Within the next month, Mr John Scurr (consultant vascular surgeon, Middlesex hospital, University College London Hospitals NHS trust) is expected to publish the results of a trial in the Lancet examining the link between DVT and air travel. He told The Journal on January 23 that the study will show a conclusive link between DVT and flying.

In more general terms, Mr Scurr said that the blood oscillates between a fine balance of bleeding and clotting. Flying pushes this balance in favour of clotting. While for the majority of passengers this did not cause a problem, it could for some groups, including older passengers and those with coexisting diseases. The real problem was that people with genetic predispositions could not be identified and such defects probably accounted for the small number of cases of DVT in young people.

Personal and environmental factors can increase the risk of developing DVT. These factors are covered in Panel 1. It is important to remember that even if people have no apparent risk factors they are not immune from the possibility of developing DVT. Therefore, all travellers should take some basic precautions against DVT and those with known risk factors should take additional ones. Advice for travellers is summarised in Panel 2.

Mr Scurr says that people with co-existing illness or who are taking a large number of medicines should be referred to their general practitioners or airline travel doctors for specialist advice prior to travelling.

General advice

All travellers should take some basic precautions against developing DVT. This includes simple exercise and keeping well hydrated. Some airlines are now including this type of advice in in-flight magazines. British Airways is issuing a leaflet with tickets to passengers which recommends standing up, stretching the arms and legs every couple of hours and taking a brief walk around the cabin when possible. The airline Qantas includes diagrams of exercises, which it says may be effective at increasing the body’s circulation, on its website (www.qantas.com.au). The exercises include circling the ankles, pumping the feet, lifting the knees and neck and shoulder rolls.

Dehydration increases blood viscosity and so is a risk factor for developing DVT. It is easy to become dehydrated on aeroplanes because of the low humidity in cabins and because of eating and drinking patterns people often adopt when flying. To avoid dehydration, travellers should be advised to drink plenty of water and to minimise intake of alcohol, caffeinated drinks and salty snacks.

Pre-flight aspirin

The use of pre-flight aspirin is a contentious issue. Aspirin is not licensed for preventing travel-related DVT and pharmacists have raised concerns about selling it for an unlicensed indication.

However, many experts have advocated its use. The House of Lords report recommends the use of pre-flight aspirin for people at moderate risk of developing DVT, including people who take the contraceptive pill or hormone replacement therapy.

Mr Scurr also recommends the use of pre-flight aspirin. He told The Journal that aspirin’s antiplatelet effect had been known about for a long time and it had been given to patients for cardiovascular purposes for years. The lack of clinical trial evidence for aspirin for prevention of travel-related DVT meant that it was unclear exactly what dose should be used. Mr Scurr said that the dose should be between 75 and 150mg and that he usually recommended a dose of 150mg.

Mr Scurr added that he believed that aspirin should be licensed for this purpose (although the lack of clinical data was a problem) and hoped that the Royal Pharmaceutical Society would endorse its use.

A spokeswoman for the Medicines Control Agency told The Journal on January 23: “The advice to give low dose aspirin (75/100mg) for airline travel would be a professional one and would be the responsibility of the advising pharmacist.” However, the MCA cautions that DVT is an unlicensed indication and that aspirin should be used with caution in many patient groups including those with an active peptic ulcer, asthma or on anticoagulation therapy.

Mrs Sue Sharpe (director of professional standards, Royal Pharmaceutical Society) told The Journal on January 24: “The MCA should consider adding this [indication for preventing DVT] to the licensed indications, after full scrutiny, which is the legal procedure for ensuring safety set down in the Medicines Act.” She added: “We note the MCA’s views that this is a professional decision for pharmacists to make. Until there is an amendment to the marketing authority, pharmacists would be supplying the product outside its licensed indications, and should make a professional decision whether to do so.”

Compression hosiery

The House of Lords report recommended that people at risk of developing DVT consider wearing compression hosiery when flying. However, no advice was given with regards to the type of stocking.

Mr Stephen Barker (consultant vascular surgeon, Middlesex hospital, University College London Hospitals NHS trust) is developing stockings designed for travel use. He told The Journal on January 22 that they differ from currently marketed compression hosiery in two ways. The main difference is that they have a consistent pressure profile which fits 85 per cent of the population, based on 1,000 limb measurements. Second, the stockings are dark blue, a more appealing colour than many of the stockings currently available. The stockings are a below-the-knee fitting as opposed to full length. Mr Barker said that a below-the-knee fitting was adequate for preventing travel DVT and that it was also much more practical than full length stockings.

Mr Barker’s stockings offer the equivalent of class I compression. He said that pharmacists could supply customers with class I below-the-knee stockings to prevent DVT on flights providing that they were properly fitted. Class II stockings gave an unnecessary amount of compression. However, he stressed the importance of making sure that existing types of stockings were properly fitted. He added that support tights, as opposed to proper compression hosiery, would not be beneficial.

Mr Barker hoped that airlines would liaise with him over making his stockings available in aeroplanes. They had been designed with the thought that they could be available “in the back of the seat” for everyone to put on when they boarded the aeroplane. A small and large size would be available for people who fell outside the 85 per cent of the population that the main stocking fitted. Mr Barker believes that the stockings could be made available in a few months but, as yet, no airline had taken them on. He added that if they did become available for retail, pharmacies would be a place at which they could be sold.

In terms of suitability of stockings, he said that there were very few people for whom stockings would be contra-
indicated. People with arterial pathogenesis should not use compression hosiery. In addition, people were occasionally allergic to the components of stockings; this could be overcome by wearing a cotton inner sock.

Mr Barker said that if pharmacists would like further advice on the use of compression hosiery for preventing travel related DVT, they could contact him at the Middlesex hospital by telephoning his secretary (tel 020 7813 9972).

Mr Scurr is also carrying out a study looking at the type of stockings that should be used to prevent DVT. He is expecting the results within the next few months.

Drug treatment

Mr Barker added his support to the use of pre-flight aspirin. He recommended the same dose as Mr Scurr, saying that all adults should take half a tablet (300mg) two hours before a flight, unless they were intolerant to aspirin. One dose was sufficient for all flight durations. People with known aspirin intolerance should ask their general practitioner for clopidogrel, he suggested, adding that while unproven for use in preventing flight-related DVT, it seemed sensible.

There has been some suggestion that heparin might be used in very high risk individuals as prophylaxis against DVT. Mr Barker thought that this use of heparin was less suitable because of the practicalities of patients administering it by injection just before a flight.

Role for pharmacists

Pharmacists are ideally placed to offer advice on traveller’s thrombosis. Advice on how to prevent traveller’s thrombosis can be easily given when selling sun care products, malaria prophylaxis or travel sickness tablets. A case study is given in Panel 3. Encouraging travellers to take simple measures such as increasing fluid intake and regular movement may help to prevent similar tragedies.

Mrs Bellingham is on the staff of The Pharmaceutical Journal

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