Embolism

An embolus is any clump of material- a globule of fat, gas bubble or a clump of blood cells - that is carried in the bloodstream until it lodges in a vessel, blocking the flow of blood. An embolus originates in a different part of the body from the place where it actually blocks a vessel. A thrombus stays at the site where it originates, but a piece can break off to form an embolus, and venous thrombosis is particularly dangerous because of this possibility.

An air embolism - a bubble of air in the veins - can be fatal, since it is churned up with the blood in the venous circulation to form an air-lock in the heat and blood vessels. This may occur through, for example, a cut throat or through injection with a syringe, or if there are great changes in pressure such as when a deep-sea diver surface; too quickly (bubbles of nitrogen are set free throughout the tissues and blood, causing the 'bends'). Excruciating pain occurs in the muscles and joints, and death may result if the blood supply to essential organs is disrupted.

Many other forms of embolism may occur. Multiple fractures can push fat from the bone marrow into the blood­stream, and clumps of bacteria may break away from the original point of infection and get into the bloodstream.

The effect of an embolus depends on its location. For example, an embolus lodging in a blood vessel in the brain will cause a stroke, and if the blockage is in the lungs - a pulmonary embolism - sudden death can result.

Treatment

The best treatment for both thrombosis and embolism is prevention. Exercise after surgical operations helps to reduce the risk of venous thrombosis. People with arterio­sclerosis should avoid injuries to the arteries by knocks or crushing. In some cases the blood vessel can be opened and the blockage removed, or a bypass operation can be performed in which an artificial artery is used to allow blood to flow around the obstruction.