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Preventing blood clots

Advice on preventing blood clots at home or in hospital.

The formation of a blood clot or 'thrombus' inside a blood vessel is called thrombosis;  you may have heard the term DVT or deep vein thrombosis that most commonly occurs in the leg veins. 

A complication of developing a clot is it can break away from where it formed and travel to another part of the body, where it may become lodged in another blood vessel and restrict the blood flow.  When a clot travels it is known as an 'embolus' and when it gets stuck in another blood vessel it's called an 'embolism'; you may have heard the term PE or pulmonary embolism, which is a clot in the lungs.  VTE or venous thromboembolism is a term that includes both DVT and PE.

How can blood clots form?

There are two reasons that a clot might form

  1. Changes or damage to the blood vessels:  If there is pressure on a vein a clot can form.  Pressure on the vein might be caused by immobility, surgery or long distance travel.
  2. Problems with the blood:  Blood problems can be inherited, caused by drugs you are taking, acute illness (such as an infection, cancer, respiratory failure, heart failure), or pregnancy.  If you are dehydrated, the blood can get 'sticky' which can increase the risk of blood forming a clot.

Risk factors

There are a number of factors that can increase a person's chance of developing a blood clot.

  • Developing a clot in the past or having a family history of clots
  • Major surgery, particularly orthopaedic (bone) surgery
  • Major trauma or leg injury
  • Obesity
  • Aged over 60
  • Cancer or chemotherapy treatment
  • Acute illnesses  
  • Smoking
  • Being immobile
  • Pregnancy, some types of contraceptive pill or hormones
  • Faulty blood clotting e.g. thrombophilia

If you have to come in to hospital

When you are admitted to hospital, nurses and doctors will assess you to see if you are at risk of developing a clot and will repeat the assessment every 48 to 72 hours.  You might hear this referred to as a VTE assessment (VTE stands for venous thromboembolism - a clot in a vein).  If you are assessed to be at risk of developing a clot you will be offered the appropriate prevention.

Prevention can include one or all of the following:

  • An injection of heparin called Dalteparin (Fragmin)
  • Anti-embolism stockings, often called 'TEDS'
  • Leg pumps or 'flowtrons'

Preventing clots

To help prevent clots at home or after you have been in hospital

  • Walk around as much as possible or, if you are not very mobile, exercies you legs while you are in bed or sitting in a chair.
  • Drink plenty of fluids
  • If you are at risk, wear anti-embolism stockings when you are on long haul journeys

There are information leaflets available on admission and discharge from hospital.

Signs and symptoms of a clot

Typical symptoms of a deep vein thrombosis (DVT) include swelling, pain, tenderness in the calf and sometimes heat and redness when compared to the other leg.

The typical symptom of pulmonary embolism (PE) is shortness of breath.

There are other causes of painful swollen calves and difficulty in breathing.  If you are concerned contact your GP, visit NHS Direct or call on 0845 45 47 or in an emergency go Accident and Emergency.

For more information visit the page