Embolism

An embolism occurs when a foreign body, such as a blood clot or an air bubble, travels through the bloodstream before becoming lodged in a blood vessel and blocking the flow of blood.

The body uses blood to transport oxygen around the body. All of the body’s tissues and organs need oxygen in order to function properly. If an embolism blocks the blood supply to a major organ, such as the lungs, brain or heart, the organ will fail. Organ failure is a medical emergency.

Foreign bodies

‘Foreign body’ is a term that is used to describe any sort of object or substance that should not usually be present in your blood. Examples of foreign bodies that can cause embolisms are outlined below.

Blood clots

Your blood contains natural clotting agents, which help to prevent excessive bleeding when you cut yourself. Once the wound has stopped bleeding, the blood clotting agents dissolve the clot.

Certain health conditions, such as high blood pressure (hypertension) or heart disease, can cause blood clots to form even where there is no bleeding. These clots do not dissolve as they should, but can travel through the bloodstream and cause an embolism.

The medical name for a blood clot is ‘thrombosis’. See Useful links for more information about thrombosis.

Fat

If one of the long bones of the skeleton, such as a thigh bone (femur), is fractured, fat particles contained within the bone may be released into the bloodstream.

Fat embolisms can also occur after severe burns, or as a complication of surgery.

Air

Bubbles of air and other gases can sometimes enter the blood stream and cause embolisms.

Air embolisms can be a particular risk for deep sea divers who surface too quickly. The rapid changes in pressure as they swim to the surface cause bubbles of nitrogen to push into their bloodstream. This is commonly known as ‘the bends’.

See Useful links for more information about air embolisms.

Cholesterol

In people who have extensive atherosclerosis (narrowing of the arteries caused by a build-up of cholesterol), small pieces of cholesterol can sometimes break away from the side of a blood vessel and cause an embolism.

See Useful links for more information about atherosclerosis.

Types of embolism

Embolisms are usually categorised by where they occur in the body. Some common types of embolism are described below.

Cerebral embolism

Cerebral embolisms are caused when a foreign body, usually a blood clot, blocks the supply of blood to the brain.

Cerebral embolisms are the leading cause of stroke. See Useful links for more information about strokes.

Pulmonary embolism

Pulmonary embolisms occur when a foreign body, usually a blood clot, blocks the supply of blood to the lungs. This is a serious condition, which can be life threatening.

A pulmonary embolism develops when the blood clot travels from your leg up into your lungs.

Deep vein thrombosis (DVT) is one of the major risk factors for pulmonary embolism. A DVT occurs when a blood clot forms in one of the veins in your leg.

See Useful links for more information about DVT and pulmonary embolisms.

Treating embolisms

How an embolism is treated will depend on:

• which type of embolism it is,
• how big it is, and
• where in the body it is located.

Obstructions such as a pulmonary embolism need emergency medical treatment.

Surgery to remove an embolism is called an embolectomy. During surgery, a cut (incision) is made in the affected artery, and the embolism is sucked out (aspiration).

If the embolism is caused by a blood clot and it is not causing emergency symptoms, medication may be used to dissolve the clot. Anticoagulant (blood thinning) medication will also be used to stop more clots forming.

People with heart conditions may also be prescribed an anticoagulant to help prevent clots forming.

Embolisms that are caused by an air bubble are usually treated in a hyperbaric chamber. In a hyperbaric chamber, the air pressure is higher than normal in order to reduce the size of the bubble(s) in the affected person’s body.

As the air bubbles are mainly made up of nitrogen, people with the bends may also be given pure oxygen to breathe in order to force the nitrogen out of their body.