Preventing Venous Thrombosis (blood clots)

What is a venous thrombosis?

A blood clot within a vein is known as a venous thrombosis, and the most common type of venous thrombosis is a deep vein thrombosis (DVT) in the leg.

When this happens, if the DVT blocks all the blood vessel then all the tissues drained by the vein can become swollen and painful due to the blood being unable to escape.

A major concern is that someone with a DVT may develop a pulmonary embolism.

This is where part of the clot (an embolus) may break off, travel up the body and through the heart to the lungs, blocking an artery. This can cause breathlessness and chest pain.

This is a potentially life-threatening condition and up to one in ten people who suffer a serious pulmonary embolism will die if it is not treated.

Who is at risk?

Just being unwell and in hospital leads to an increase in the risk of deep vein thrombosis, or a blood clot, usually in the deep veins of the leg. This may be due to the fact that you are not mobilising as much as normal.

The risk is higher if you’re having cranial / spinal surgery or have reduced mobility in critical care. Patients who become unwell and less active than normal are also at risk.

Although a deep vein thrombosis (DVT) may cause swelling and discomfort at the time, more than half are clinically ‘silent’ and there may be no obvious symptoms.

In the longer term, the DVT can also lead to post-phlebitic syndrome – swelling, pain, dermatitis, cellulitis, varicose veins, pigmentation of the skin and eventually chronic ulceration of the lower leg.

Prevention of a DVT, pulmonary embolism and post-phlebitic syndrome in hospital can be simple and very straightforward. 

How can you reduce the risk of venous thromboembolism in hospital?

On admission all patients will be risk assessed and given appropriate prevention if necessary – this is called Thromboprophylaxis.

The risk of DVT does vary enormously. For example, if you are admitted as a day case for a minor operation under local anaesthetic, then the risk is reduced.

The standard method we use for risk assessment is for a nurse or junior doctor to use a scoring system where risk factors can be checked. The risk factors include (amongst others):

• Are you over the age of 60?
• Do you, or do any members of your family, have a previous history of DVT or thrombosis?
• Are you overweight, or have you previously had cancer?
• Heart problems, lung problems or an inflammatory bowel or joint problem?
• Are being given a general anaesthetic or having an abdominal operation or hip of leg surgery?
• Is there any reason not to give you thromboprophylaxis such as a low platelet count, you are already on anticoagulants or you have a bleeding or clotting disorder?

Depending on the answers given, our hospital policy is to use the following (either on their own or as a combination):

• Compression stockings.
• Inflatable sleeves.
• Blood thinning injections (e.g dalteparin (Fragmin®) or enoxaparin (Clexane®))

Compression stockings are elasticated and increase blood flow in your legs. You will need to be measured to ensure they fit correctly. The stockings should be removed at least daily to allow for bathing and to check the skin.

You should not however wear them if you have dermatitis, gangrene, leg ulcers, cellulitis, known allergies to stockings, gout, recent skin grafts, nerve or circulation problems in your legs or leg swelling (oedema) or deformity.

The team may ask you to wear inflatable sleeves around your calf or on your feet; these inflate at regular intervals to increase the blood flow.

The use of blood thinning injections is common and most people do not have any problems. However, like many medications it may sometimes cause side effects.

The most common of these include pain, skin rashes and/or minor bruising at the site of your injection.

If you feel that you do not want this treatment or if you feel that you have a risk factor that has been overlooked, (and the prevention strategy is inadequate) please discuss with your doctor or nurse as soon as possible

Other things which may be useful to prevent DVT during your hospital stay include:

• Stay as mobile as your condition or pain allows.
• If you are confined to bed you will be encouraged to do leg exercises.
• Drinking fluids regularly or as directed by the nursing staff so you do not become dehydrated

What will happen when I am discharged from hospital?

Most people have the injections discontinued and stop using the stockings once they are fit and ready for discharge.

Some patients however may need to continue with either the blood thinning injections and/or the stockings.

If this is the case your ward team will inform you of this and make any necessary arrangements for this (e.g. teach you or your carer how to administer the injections or wear the stockings, arrange for District Nurses to give the injections etc).

Following discharge you should be aware of the risk of developing blood clots especially in the first few weeks.

Symptoms of deep vein thrombosis

Unfortunately 80% of people with DVT may not have any obvious symptoms at all. The most common symptoms include pain, tenderness and swelling of the leg, usually in the calf. Discolouration of the leg is less common. If thrombosis occurs in the thigh veins,the whole leg may be swollen.

Symptoms of pulmonary embolism

The main symptoms of pulmonary embolism are shortness of breath and chest pain.

Occasionally patients may become clammy and have unexpected dizzy or panicky episodes; with or without a persistent cough.

If you develop any sign or symptoms of a blood clot at home, then seek medical attention immediately. Contact NHS 111; go to a walk in centre or the Accident and Emergency department.

It is advisable to avoid long distance travel (longer than three hours) for four weeks after surgery, as this can increase your chances of developing a DVT.