summary Fat Embolism Syndrome is an acute respiratory disorder caused by an inflammatory response to embolized fat globules that may enter the bloodstream as a result of acute long bone fractures or intramedullary instrumentation. Patients present with hypoxia, changes in mental status, and petechial rash. Diagnosis is made clinically with presence of hypoxemia (PaO2 < 60), CNS depression, petechial rash, and pulmonary edema. Treatment is focused on prevention with early stabilization of long bone fractures. Mechanical ventilation with high levels of PEEP is the recommended treatment for acute presentation. Epidemiology Incidence 3-4% with isolated long bone trauma 10-15% with polytrauma Etiology Pathophysiology fat and marrow elements are embolized into the bloodstream during acute long bone fractures intramedullary instrumentation intramedullary nailing hip & knee arthroplasty pathophysiology two theories regarding the causes of fat embolism include mechanical theory embolism is caused by droplets of bone marrow fat released into venous system biochemical theory lipoprotein lipase induces free fatty acid production with resultant hyperinflammatory response similar to ARDS Diagnosis Criteria Major (1) hypoxemia (PaO2 < 60) CNS depression (changes in mental status) petechial rash pulmonary edema Minor (4) tachycardia pyrexia retinal emboli fat in urine or sputum thrombocytopenia decreased HCT Additional PCO2 > 55 pH < 7.3 RR > 35 dyspnea anxiety Presentation History symptoms usually present within 24 hours of inciting event Symptoms patient complains of feeling "short of breath" patient appears confused Physical exam tachycardia tachypnea petechiae axillary region conjunctivae oral mucosa Studies ABG hypoxemia (PaO2 < 60 mmHg) Treatment Nonoperative mechanical ventilation with high levels of PEEP (positive end expiratory pressure) indications acute fat emboli syndrome Prevention early fracture stabilization indications early fracture stabilization (within 24 hours) of long bone fracture is most important factor in prevention of FES techniques to reduce the risk of fat emboli overreaming of the femoral canal during a TKA use of reamers with decreased shaft width reduces the risk during femoral reaming for intramedullary fixation use of external fixation for definitive fixation of long bone fractures in medically unstable patients decreases the risk Prognosis Fatal in up to 15% of patients