Thrombosis PDF Print E-mail

Immobility, circulatory problems and Deep Vein Thrombosis (DVT)

Contraction of muscles is an important factor in helping to keep blood flowing
through the veins, particularly in the legs. Prolonged immobility, especially when
seated, can lead to pooling of blood in the legs, which in turn may cause swelling,
stiffness, and discomfort.
It is known that immobility is one of the factors that may lead to the development
of a blood clot in a deep vein, so-called “deep vein thrombosis”, or DVT. Research
has shown that DVT can occur as a result of prolonged immobility, for instance
during long distance travel, whether by car, bus, train or air. The World Health
Organization (WHO) has set up a major research study to find out if there are
any factors that might lead to the risk of DVT being higher for air travel than for
other causes of immobility.

In most cases of DVT, the clots are small and do not cause any symptoms. The
body is able to gradually break down the clot and there are no long-term effects.
Larger clots may cause symptoms such as swelling of the leg, tenderness, soreness
and pain. Occasionally a piece of the clot may break off and travel with the
bloodstream to become lodged in the lungs. This is known as pulmonary
embolism and may cause chest pain, shortness of breath and, in severe cases,
sudden death. This can occur many hours or even days after the formation of
the clot.
The risk of developing DVT when travelling is very small unless one or more
other risk factors are present. These include:

  • Previous DVT or pulmonary embolism
  • History of DVT or pulmonary embolism in a close family member
  • Use of oestrogen therapy–oral contraceptives (“the Pill”) or hormone replacement therapy (HRT)
  • Pregnancy
  • Recent surgery or trauma, particularly to the abdomen, pelvic region or legs
  • Cancer
  • Some inherited blood-clotting abnormalities.

 

Precautions

The risk of a passenger who does not have any of the risk factors above developing
DVT as a consequence of flying is small and the benefits of most precautionary
measures in such passengers are unproven and some might even result in harm.
Some common-sense advice for such passengers is given below.

Moving around the cabin during long flights will help to reduce any period of
prolonged immobility. However, this may not always be possible and any
potential health benefits must be balanced against the risk of injury that could
occur if the aircraft encounters sudden and unexpected turbulence. A sensible
compromise is to walk around in the cabin, e.g. go to the bathroom, once every
2–3 hours. Many airlines also provide helpful advice on exercises that can be
carried out in the seat during flight. It is thought that exercise of the calf muscles
can stimulate the circulation, reduce discomfort, fatigue and stiffness, and it may
reduce the risk of developing DVT. Hand luggage should not be placed where it
restricts movement of the legs and feet, and clothing should be loose and
comfortable.

Wearing properly fitted graduated compression stockings may be helpful. These
compress the calf muscles and improve the flow of blood in the deep veins. They
may also help prevent the swollen ankles that are quite common on long flights.
However, they need to be the correct size to be effective and passengers should
therefore ask their doctor or a travel medicine clinic which type would be
appropriate for them.

In view of the clear risk of significant side effects and absence of clear evidence
of benefit, passengers are advised not to use aspirin just for the prevention of
travel-related DVT.

Those travellers who are at most risk of developing DVT may be prescribed
specific treatments, such as injections of heparin. Cabin crew are not trained to
give injections and travellers who have been prescribed these must either be taught
to give the injections themselves or make other arrangements to have them given
by a qualified person.

 

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