Fat Embolism

A certain degree of lung dysfunction occurs in all patients after long bone fractures, but clinically significant fat embolism syndrome develops in only 10% to 15% of these patients. Signs include hypoxia, tachycardia, mental status changes, and petechiae on the conjunctiva, axilla, or upper thorax. Fat globules in the urine are non-diagnostic, but lung infiltrates seen on chest radiograph confirm the presence of lung injury.^{[237] [238] [239]}

The pathophysiology of fat embolism represents capillary endothelial breakdown, causing pericapillary hemorrhagic exudates that are most apparent in the lungs and brain. Pulmonary edema and hypoxemia occur as a result of pulmonary exudates. Hypoxia and areas of cerebral edema may account for the various neurologic abnormalities seen.

The more severe cases of fat embolism involve fractures of the femur and tibia. Delays in fixation of bones and extensive reaming of the medullary canals contribute to perioperative morbidity^[240] and to the severity of fat embolism syndrome. Efforts to surgically correct fractures early and minimize trauma to the bone marrow lessen the degree of fat or bone marrow embolism. Patients with coexisting lung injury are at additional risk for fat embolism. Evidence suggests that fat may pass to the systemic circulation through a patent foramen ovale^{[76] [77]} or by transpulmonary passage.^[79] The chemical composition of the fat may even contribute to this process.^[241] For this reason, it is preferable to minimize pulmonary artery hypertension to reduce transpulmonary passage of fat and limit pulmonary endothelial transudation of fluid.

Treatment includes early recognition, oxygen administration, and judicious fluid management. Corticosteroids in large doses shortly after major trauma have been found to minimize the clinical presentation of fat embolism but are probably not necessary in most cases if oxygen therapy is administered. With appropriate fluid management, adequate ventilation, and the prevention of hypoxemia, the outcome is usually excellent.