Embolism, fat: A process by which fat tissue passes into the bloodstream and lodges within a blood vessel. In general, an embolus is something that travels through the bloodstream, lodges in a blood vessel, and blocks it. A fat embolus is a fat particle or droplet that travels through the circulation and eventually blocks a blood vessel. Fat emboli tend to be small and multiple, causing numerous signs and symptoms.

Up to 90% of cases are associated with trauma, and fracture of or surgery on a large bone, such as the femur bone of the thigh. As a result of the broken bone, the bone marrow fat escapes into the bloodstream. Alternatively, fat embolism can also arise from with parenteral lipid infusion (a form of nutritional supplementation), pancreatitis, burns, childbirth, and other conditions. Although release of bone marrow fat into the circulation may be a cause, fat embolism may arise due to conditions such as widespread trauma or diseases that alter lipid metabolism in the body.

Typically, fat embolism occurs suddenly 12-36 hours after an injury. Symptoms and signs depend on the specific location of the blocked arteries. Signs and symptoms of fat embolus include central nervous system dysfunction that may progress to coma or death, irregularities in the heartbeat, respiratory distress, and fever. Anemia and thrombocytopenia (low platelet count) are common. Commonly, small hemorrhages are seen on the neck, shoulders, armpits, and conjunctiva.

The mortality (death) rate is 10%-20%. The elderly and those with underlying medical conditions or poor health have worse outcomes.