Deep Vein Thrombosis And Air Travel

Deep Vein Thrombosis And Air Travel Courtesy of Sunday Leader

Inner lining of all veins including the major deep veins have  smooth surface, and a valvular mechanism to help  venous (blue) blood that returns to the lungs for re-oxygenation to travel unhampered. With ageing plaques are formed in arteries, which obstructs the flow of oxygenated blood as in coronary artery disease. Such plaques never occur in veins under normal situation.

Formation of clots in normal deep veins is called ‘Phlebo-thrombosis’ as opposed to clot formation in inflamed veins, called ‘Thrombo-plebitis’. Here being discussed on Phlebo-thrombosis or commonly called ‘Deep Vein Thrombosis’ (DVT).

How do you get clots in healthy veins?

Deep vein thrombosis (DVT) is the formation of clots in veins under certain situations, predominantly in the leg. Clots are formed when the blood thickens and clumps together.This could happen when the peripheral calf muscles become inactive due to prolonged sitting down in one position as travelling on a plane, or more commonly in a debilitated condition you lie in sleeping position for prolonged periods, as also common during long operations and during the post-operative aftercare period. During pregnancy women can get deep vein thrombosis during the last term of pregnancy.

During operations preventive measure are frequently taken when people, particularly the elderly and the obese undergo surgical operations where the electrical muscle massage pads are used. Travel by any mode of transport, due to immobility of the lower limbs for long journeys are one of the commonest causes of DVT, though the incidence is rare.

The danger is that these clots being formed in undamaged deep veins can move along with the returning venous blood and cause pulmonary embolism (PE). The word embolus is used to define a moving blood clot, or any material through blood vessels, such as plaque dislodging in arteries during angiograms or Transient Ischemic Attacks (TIA).

In Thrombo-phlebitis the blood clots formed do not travel, and there is no danger of Pulmonary Embolism. The commonest symptom of Pulmonary Embolism (PE) is sharp chest pain with or without breathlessness. If the circulating clot is large it would be life threatening.

Each year in Australia there are up to 400 deaths from pulmonary embolism (PE) and of these only a small appear to be associated with air travel. However, it was the publicity surrounding two unexpected deaths from Pulmonary Embolism — a blood clot travelling from the legs to the lungs — after long-haul air travel in 2000 that sparked renewed interest in the issue and much public debate.

Some pre-disposing factors include smoking, age, obesity and pregnancy. Use of oral contraceptive pill and hormone replacement therapy among post-menopausal women is another cause for concern. Other causes are cancer, lower limb injuries or surgery, family history of DVT and previous history of thrombosis or embolism.

The Australian Society of Thrombosis and Haemostasis recommends the following to avoid DVT:

  • Drink plenty of (non-alcoholic) fluids during flights
  • Regularly mobilise the ankles and massage the calves
  • Wear loose, non-restrictive clothing
  • Avoid excessive movement around the cabin, as the risk of injury from turbulence may outweigh the benefit of exercise.
  • Be vigilant for the symptoms of DVT, in particular pain in the calves, during and for up to a month after long flights. If symptoms occur, seek medical advice without delay.

Most airlines demonstrate on sky screen the type of ankle exercises you should do regularly whilst sitting down for long hours on a plane. The movements make the peripheral calf muscles to freely pump the venous blood towards the heart. These exercises must be carried out frequently by all long distance travellers. Deep Vein Thrombosis is very rare among the Asians, but the demonstrated exercises should be done frequently on flights by all travellers.

(The body has two blood pumping machines, one is the heart and the second pump is in the periphery – the calf muscles)

Economy Class Syndrome

Cramped seating in the cabin, prolonged inactivity caused by inadequate space may slow down the venous upward blood flow, producing swelling (oedema) around the ankles. This swelling could be due to lymphatic stasis in the lower limbs due to the same cramped seating positions.

Low cabin pressure, low humidity has a dehydrating effect that concentrates the blood making it sluggish. Alcohol makes you more dehydrated and ads as a minor factor for clot formation

DVT is rare among business class passengers.

Symptoms of DVT

The symptoms first appear locally on the lower limbs, especially in the area of calf muscles. Pain and tenderness in the affected leg are the commonest symptoms, especially on movement at the ankle.
In some cases DVT does not give rise to any symptoms. Swelling around the ankle region may appear subsequently, and the area of the skin will be warm and red in colour. The redness is not visible among the dark Asians.

Prevention

General preventive strategies for developing DVT include lifestyle factors. Keeping a steady healthy weight is important. This could be achieved by exercising and proper dieting.
Sri Lankan ladies after a certain age give up keeping slim and most never exercise. In spite of these factors, fortunately, DVT is rare among the Sri Lankan ladies.

Treatment

If you experience calf pain and tenderness when you are ravelling by a plane, promptly call a flight attendant and request for a crepe bandage. This should be wrapped from bottom, starting at the ankle right up to the knee area quite firmly. This compression required to prevent clot travelling.

Drink plenty of water, abstain from alcohol consumption.

As soon as you land, see a doctor who’ll order an ultra-sound (duplex ultrasound)to confirm. If the doctor is not satisfied with negative results, he may order a venogram.

Venogram uses an X-ray image to tract the distribution of a special dye injected into the vein at the ankle.
If symptoms are severe with difficulty in walking you may need hospitalisation. Intravenous drugs such as heparin will be given through drip to dissolve the clots.

Rare cases surgery may be required if there is no improvement.

According to the www.airhealth.org  3-5% of air travellers will develop clots. Most experts do not agree that clots are formed direct due to air travel.  In the absence of large-scale studies, some airlines’ authorities feel there is no scientific basis to warrant thrombosis prevention on flights. Ironically, most airlines include extensive instructions in flight magazines on how to avoid DVT during flight.  However, the apparent increase in risk has prompted some afflicted travellers to site the Warsaw Convention of 1929, which holds airlines liable for damages when passengers are injured by an accident, as grounds to file negligence claims against the carriers.  The debate is whether a blood clot is a preventable event, or an individualized reaction to normal flight operations.

By Dr Harold Gunatillake
Health Writer

Courtesy of Sunday Leader


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