Fat Embolism: A Central Nervous System Problem

Microvascular fat in the systemic circulation is a common postmortem finding in patients dying after trauma or cardiopulmonary bypass. The causative relationship between the microvascular fat and tissue inflammation, ischemia, and injury is unclear. Characteristic clinical lesions on magnetic resonance imaging and evidence in animal models suggest that focal cerebral edema may be associated with fat microemboli. This fat occludes cerebral vessels 5-15 microns in diameter, after passing through either the lung or filters in cardiopulmonary bypass circuits. Microvascular fat may directly cause the injury or may be a ‘second hit’ phenomenon, thus aggravating a pre-existing inflammatory reaction to injury, indirectly causing cerebral injury and adverse neurocognitive outcomes after cardiac surgery and trauma.