Birmingham City Council

Deep Vein Thrombosis

What is DVT?

Aeroplane

Deep vein thrombosis (DVT) is the formation of a thrombosis (blood clot) within a deep vein, commonly in the thigh or calf. When the rhythm of circulation slows down due to illness, injury or inactivity, there is a tendency for blood to accumulate or 'pool'. A static pool of blood provides the ideal environment for clot formation. The clot can then either partially or completely block the flow of blood in the vessel.

What causes DVT?

Clots are a necessary form of injury repair. When a vessel is injured, platelets attach themselves to the wound and begin producing chemicals which attract more platelets. Special proteins known as clotting factors then signal the assembled platelets to form a clot. Chemicals released by the walls of the injured vessel set off a cascade of reactions intended to produce fibrin - a thread like protein that weaves itself through a clot to stabilise it. Usually a balance is maintained so that injuries and wounds are repaired without excess blood loss. DVT occurs when certain risk factors set off the cascade at the wrong time and place.


Who is at risk?

As inactivity slows down blood flow, anyone that remains relatively immobile for hours at a stretch can become a victim of DVT. It is sometimes referred to as 'economy class syndrome' because cheaper seats on planes have less legroom and therefore restrict movement. Yet DVT can be caused by a variety of reasons - injury to the vein following surgery or radiation therapy; or as a result of poor circulation due to heart disease or stroke. Whilst some people are not born with vital 'blood thinning' substances and are therefore always more susceptible to blood clots. Certain medicines such as the contraceptive pill and HRT can marginally increase the risk of developing DVT.

What precautions should be taken?

Avoiding prolonged immobility can prevent DVT, and if this is not possible, simple measures such as moving the lower limbs on a regular basis can make a difference. Regular exercise and not smoking can help greatly too. On aircraft, it is recommended that you get up and walk at least once every hour, and drink plenty of water to avoid dehydration.


What are the symptoms and effects?

Symptoms of DVT include pain, swelling, fever, rapid heartbeat, discolouration of the affected area, and skin that is warm to the touch. For those who develop DVT, hospitalisation and bed rest are initially necessary, as well as applying warm moist heat to the wound. If DVT is recognised and treated early it will usually resolve itself without complication. However, if left untreated it can cause severe complications which may be fatal. The most serious complication can be 'pulmonary embolism'. This is when a blood clot breaks free from a vein wall, travels to the lung and blocks an artery. Symptoms of pulmonary embolism can be shortness of breath, rapid pulse, sweating and sharp chest pain, and as it can be life threatening it requires immediate medical attention.

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