Air Embolism

Description

Air embolism occurs when a bubble of air is introduced into the vascular system and obstructs a blood vessel. As little as 100 mL of air introduced rapidly into a vein, may be fatal. The air circulates via the venous system to the right atrium, and right ventricle. This leads to outflow obstruction from the ventricle into the pulmonary system, causing circulatory collapse.

In patients who have any degree of right to left shunting within the heart, (up to 10 per cent of patients in some settings) air can be pumped directly from the venous system (right heart) to the arterial system (left heart). Extremely small amounts of air can cause a stroke if subsequently circulated into the cerebral arterial system.

Air embolism may occur when air is introduced into a blood bag, particularly if it is being transfused under pressure. However, most reported cases associated with blood transfusion occur in association with cell salvage devices, usually because of failure to follow manufacturer's instructions.

The incidence of air embolism associated with conventional transfusion is unknown, but rare. One study showed that the frequency of fatal air embolism after re-administration of recovered blood was approximately 1:30,000-1:38,000 patients transfused.