The fat embolism syndrome.

The clinical fat embolism syndrome consisting of progressive pulmonary insufficiency, cerebral disfunction, and petechiae is rare. Following severe skeletal trauma, fat droplets appear in the circulating blood and embolize the capillaries of the lungs and other organs. Whether fat droplets are of mechanical or chemical origin remains controversial. These fat droplets cause mechanical occlusion of lung capillaries followed by chemical changes associated with hydrolysis of the neutral fat to free fatty acids. The free fatty acids produce a toxic and inflammatory reaction resulting in pulmonary edema, hemorrhage, and microatelectasis. The clinical and radiographic abnormalities appear after an initial latent period of 12 to 72 hours. The chest radiographic findings are nonspecific and consist of bilateral patchy or diffuse alveolar and interstitial lung densities. With aggressive management the survival has markedly improved, and mortality is now rare.