section name header

General Reference

Nejm 1993;329:926, 961; 1967;276:1192

Pathophys and Cause

Cause:Fat globules, from bony fractures, via the circulation to the pulmonary arteries and other vessels? Often seen w total hip replacement (94%—Clin Orthoped Related Res 1999;355:23)

Pathophys:Fat from marrow or from tissue enter veins to inferior vena cava, or enter the lymphatics and from there go to the thoracic duct via the superior vena cava to the lungs and beyond to the systemic circulation; there the fat emboli are broken down by lipoprotein lipase into triglycerides and free fatty acids, which are toxic molecules

Epidemiology

Symptomatic emboli in 3% of all femoral shaft trauma; they are the cause of death in 5% of all trauma deaths; but 90% of emboli cause no sx or are undetected

Signs and Symptoms

Sx:24-48 h latent period after femoral, pelvic, tibial, humeral, or other trauma; then nonlateralizing CNS sx’s of confusion/acute brain syndrome; dyspnea and respiratory distress

Si:Fever; tachycardia; skin petechiae (85%), mantle distribution over chest, neck, and conjunctiva; cyanosis; confusion

Course

of those with sx, 10-20% mortality if no coma; 85% mortality if coma present

Complications

Adult respiratory distress syndrome (Acute Respiratory Distress Syndrome (Shock Lung))

Lab and Xray

Lab:

Chem:Lipase elevated in 3-5 d, peaks at 5-8 d

Hem:Thrombocytopenia

Noninv:Transesophageal cardiac echo shows emboli themselves during fx repair (Clin Orthoped Related Res 1999;355:23)

Path:Bx of petechiae or kidney show fat in capillaries with platelets about them; use frozen section, which avoids formalin dissolution of the fat. Sputum stained for fat, 80% false negative; bronchial lavage shows intracellular fat in >33% of cells (8/8 patients—Ann IM 1990;113:583)

Urine:Fat stain positive in 60% with acid-washed glass

Xray:

Chest shows bilateral fluffy infiltrates, ARDS

Lung scans show mismatched V/Q defects

Treatment

Rx:

Methylprednisolone 1+ mg/kg q 6 h × 3 d at first si in likely patient; prevents without complications (Ann IM 1983;99:439)

Supportive rx of ARDS (Acute Respiratory Distress Syndrome (Shock Lung))