What is a blood clot?

When you are injured or have an operation, your blood naturally clots to help prevent you from losing too much blood. However, this also increases the risk of a blood clot forming inside a deep vein. This usually happens in your leg and is called a deep-vein thrombosis (DVT). You may not notice you have a DVT. However, a DVT usually causes pain, swelling, heat and redness.

A blood clot can sometimes move through your veins to your lungs. This is called a pulmonary embolism, which is serious and can even cause death.

DVT and pulmonary embolism are together referred to as venous thromboembolism.

The healthcare team will assess you and may recommend treatment to reduce your risk of developing a blood clot.

Am I at risk of developing a blood clot?

Moving around less than usual (such as when you are in hospital), illness and surgery can make your blood more prone to clotting inside a blood vessel.

You are at a much higher risk of developing a blood clot if one or more of the following applies to you:

• You have cancer.
• You are over 60 years old.
• You are obese (body mass index score is over 30).
• You are dehydrated.
• You smoke.
• You have a condition where your blood clots too easily (thrombophilia).
• You have heart or lung problems, a serious infection or an inflammatory condition.
• You have a family history of DVT.
• You use contraceptives or hormone replacement therapy (HRT) that contain oestrogen.
• You have varicose veins with phlebitis.
• You are pregnant or have given birth within the last 6 weeks.

Even if you do not have any of these risk factors, you have a higher risk of developing a blood clot if any of the following apply to you.

• You are going to be moving around less than usual for more than 3 days.
• You are going to be travelling for more than 4 hours.
• You are having surgery for an inflammatory or abdominal condition.
• You are having surgery that lasts for more than 90 minutes, or more than an hour if the surgery involves your pelvis or legs.

What treatments are available to prevent a blood clot?

There are simple, effective treatments available. It is important that you understand and carefully follow the instructions of the healthcare team.

Mechanical treatments

The healthcare team may recommend that you wear anti-embolism stockings (also called compression or TED stockings). These are tight stockings that make your blood move more quickly through your legs. The healthcare team will measure your legs to make sure you are given the right size and will show you how to use them.

Intermittent pneumatic compression devices inflate automatically at regular times to force the blood to move through your legs.

Stockings and compression devices can cause discomfort, blisters and ulceration. This usually happens only if they are not fitted correctly. The risk is higher if you have poor circulation in your legs.

If you develop any of these problems, or have had leg ulcers or pain in your calves, let the healthcare team know so that you can be assessed again.

There is also a risk of an allergic reaction to the materials. Let the healthcare team know if you have any allergies.

Medication

This involves giving you blood-thinning medication that reduces your blood’s ability to form clots.

Depending on your risk, the healthcare team may offer you medication given by injection just under your skin. You may be offered other oral (by mouth) medication.

If you are bleeding or at high risk of bleeding, the healthcare team will usually not recommend medication. However, the healthcare team will need to compare the risk of you bleeding too much with the risk of you developing a blood clot.

What can I do to help reduce my risk?

If you are able to, walk around as often as you can. If you need to stay in bed or in a chair, try to move your feet and legs. Do not cross your feet or legs.

Drink plenty of water to avoid dehydration. The healthcare team will advise how much and when you can drink.

If you smoke, stopping smoking may reduce your risk of developing a blood clot and will improve your long-term health.

Try to maintain a healthy weight. You have a higher risk of developing a blood clot if you are obese.

Most blood clots develop only after a patient has left hospital, so it is important that you continue to be as active as possible at home. Make sure you understand and carefully follow the instructions of the healthcare team if you have been given medication or need to wear special stockings.

If you develop pain, swelling or redness in your leg, or the veins near the surface of your leg appear larger than normal, you may have a DVT. Let your doctor know straight away.

If you become short of breath, feel pain in your chest or upper back, or if you cough up blood, you may have a pulmonary embolism. Call an ambulance or go immediately to your nearest Emergency department.

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