Deep vein thrombosis

How can it be prevented?

Once you have been treated for DVT, you can help prevent further clots from forming by the following measures:

• avoid knee socks or hosiery that might limit blood flow through the leg
  
• do not cross ankles or legs while sitting or lying
  
• avoid prolonged sitting or standing in one position
  
• while resting, keep moving your legs, and bending your ankles and toes.
  
• drink plenty of water during the flight, and avoid alcohol, to ensure you do not become dehydrated.

Anticoagulants may be prescribed as a preventive measure for high risk people or people undergoing high risk surgical procedures. Minimize immobility of the legs during long plane trips or car trips.

What is deep vein thrombosis?

Deep vein thrombosis (DVT) refers to the formation of a blood clot or thrombus within a vein commonly in the thigh or calf. The blood clot can either partially or completely block the flow of blood in the vein.

What are the causes?

DVT affects mainly the veins in the lower leg and the thigh. It involves the formation of a clot (thrombus) in the larger veins of the area. This thrombus may interfere with circulation or it may break off and travel through the blood stream (embolize). The embolus thus created can lodge in the brain, lungs, heart, or other area, causing severe damage to that organ.

Risk factors that may cause DVT include prolonged sitting, bed rest or immobilization (such as on a long plane or car trips), recent surgery or injury (especially hip, knee or gynaecological surgery), a fracture, childbirth within the last 6 months and the use of medications such as oestrogen and birth control pills. DVT is more common in the elderly and the overweight, but healthy young people can develop it as well. Although anyone can develop DVT on a flight, certain people are more vulnerable, including pregnant women, people who are overweight, those whose feet don't reach the floor, smokers and those with coronary artery diseases and certain blood conditions.

What are the symptoms?

The symptoms of deep vein thrombosis include:

• leg pain or tenderness in one leg only
  
• swelling (oedema) of only one leg
  
• increased warmth
  
• changes in skin colour, redness

The most common, serious complication of DVT is pulmonary embolism, where a blood clot breaks free from a vein wall, travels to the lung and blocks an artery. Pulmonary embolism can be life - threatening and needs immediate medical attention. DVT can also cause a miscarriage or stillbirth if a blood clot breaks free and lodges in an artery in the placenta, reducing the oxygen supply to the fetus.

How is it diagnosed?

If a clot is suspected, the doctor will perform a complete physical examination and take the patient’s medical history. A sharp pain when the foot is flexed upwards may indicate the presence of a blood clot in the leg. Other tests may also be conducted, including:

• an ultrasound scan of the leg
  
• X-rays of the veins after dye is injected into a foot vein – this allows the doctor to see how the blood is flowing
  
• tests that measure the body's blood clotting mechanism (these are usually used to check patients at high risk of DVT rather than for diagnosis).

What is the treatment?

Treatment of DVTs is intended to prevent the development of a pulmonary embolus and to prevent recurrent DVT.

The standard treatment has been a medication called heparin that prevents clot formation. This is given through the vein. This results in relatively immediate anticoagulation and treatment of the clot.  Along with heparin an oral medication called warfarin is given.  The warfarin is usually continued for approximately six months.  In almost all circumstances warfarin should not be initiated until heparin has been started.

Because heparin is given as a continuous intravenous infusion, it requires hospitalisation.  However, newer forms of heparin, known as low molecular weight heparin (usually enoxaparin) can be used in some circumstances.  This heparin can be given by injection once or twice a day and, thus, can shorten or eliminate the need for hospitalisation.

If deep vein thrombosis is recognised early and treated properly, it will usually resolve itself without complication. If left untreated, however, it can cause severe complications, which may be fatal.