Fat embolism

Related Subjects: | Air Embolism | Fat Embolism

🛑 Fat Embolism Syndrome (FES) usually appears 24–72 h after trauma or orthopaedic surgery. Think FES in any patient with recent long-bone/pelvic fractures who develops the triad: 🫁 hypoxemia + 🧠 neurological change + 🔴 petechial rash. Diagnosis is clinical-there is no single confirmatory test.

🧬 Pathophysiology (why it happens)

• Mechanical: Marrow fat enters venous blood after long-bone/pelvic injury → microembolization of lung/brain capillaries.
• Biochemical: Lipase liberates free fatty acids ➜ endothelial injury, capillary leak, inflammation (ARDS-like picture).
• Onset typically 24–72 h. Rash often appears 12–36 h and fades within 24–48 h. ⏱️

⚠️ Causes & Risk

• Long-bone (esp. femur) & pelvic fractures; intramedullary reaming/nailing; multiple trauma.
• Others: orthopaedic surgery, pancreatitis, sickle crisis, severe burns, liposuction, decompression sickness, IV lipid infusion, bone marrow biopsy.
• Higher risk: Multiple fractures, delayed fixation, extensive soft-tissue injury, older age. 👵🧓

🩺 Clinical Features (classic triad)

• Respiratory: Dyspnoea, tachypnoea, hypoxemia → non-cardiogenic pulmonary oedema/ARDS. 🫁
• Neurologic: Confusion, agitation, delirium, seizures, coma (often fluctuating). 🧠
• Cutaneous: Non-dependent petechiae on chest, axillae, shoulders, conjunctivae (transient but distinctive). 🔴
• Ocular: Purtscher(-like) retinopathy (cotton-wool spots, retinal haemorrhages). 👁️

🧪 Diagnosis (clinical; exclude mimics)

• Labs: Hypoxemia; thrombocytopenia; anaemia; ↑ESR; ↓fibrinogen possible. Fat globules in urine/BAL are non-specific.
• ABG: PaO₂/FiO₂ (P/F) <300 suggests lung injury; use SpO₂/FiO₂ index if ABG unavailable.
• CXR: Diffuse bilateral infiltrates (ARDS pattern). CT chest: Patchy ground-glass/centrilobular nodules.
• MRI brain (if neuro signs): DWI “starfield” pattern (innumerable punctate lesions). 🌌

📏 Common Diagnostic Criteria (guides-not definitive)

🧠 Differential Diagnosis (don’t miss these)

• Pulmonary embolism, aspiration pneumonitis/pneumonia, pulmonary contusion, TRALI, cardiogenic pulmonary oedema, ARDS from sepsis.
• TBI, hypoglycaemia, electrolyte derangement, sedative/opioid effect for neurological changes.
• Meningitis/encephalitis if fever + focal signs.

🛠️ Management (supportive is key)

• Oxygen/Ventilation: ARDSnet strategy; consider prone positioning and inhaled pulmonary vasodilators for refractory hypoxemia.
• Hemodynamics: Avoid fluid overload; vasopressors for MAP ≥65 mmHg.
• Early fracture fixation: Prefer early, gentle handling/venting techniques during intramedullary nailing to reduce embolic load. 🦴
• Anticoagulation: No role to treat FES itself; use standard VTE prophylaxis unless contraindicated.
• Steroids: Evidence mixed-may reduce hypoxemia incidence in high-risk trauma but no clear mortality benefit. Not routine; consider case-by-case with ICU/ortho input. 💊
• Neuro care: Prevent secondary injury-oxygenation, normocapnia, avoid hypotension/hyperthermia; head-of-bed ↑30°. 🧠
• Rescue: ECMO in select refractory ARDS. 🫀
• Antibiotics: Not indicated unless infection suspected. 🦠
• Rehab & nutrition: Early PT/OT once stable; adequate protein/calories. 🍽️

🛡️ Prevention

• Prompt immobilization and early definitive fixation of long-bone fractures.
• Gentle fracture manipulation; consider canal venting/reaming techniques to lower intramedullary pressures.
• Optimize pain control and oxygenation; avoid unnecessary delays to theatre. ⏳

📈 Prognosis

• Most improve with early recognition and supportive care; severe cases can have 10–15% mortality.
• Respiratory failure typically peaks by day 2–3; neuro symptoms may persist days–weeks but often resolve.

🧾 Useful Pearls

• Rash absent ≠ rule-out FES (present in ~1/3–1/2).
• Thrombocytopenia + hypoxemia post-fracture should trigger FES consideration even without rash.
• “Starfield” MRI pattern supports diagnosis but is not mandatory for treatment decisions.

📚 References

• Fat Embolism Syndrome – review (open access)

Cases - Fat Embolism Syndrome (FES)

• Case 1: A 24-year-old man sustains a closed femoral shaft fracture after a motorbike crash. Initially stable, but 36 hours later he becomes acutely breathless with SpO₂ 85% on air, confused (GCS 13), and develops a petechial rash over his chest and conjunctiva.
  Management: High-flow oxygen, cautious IV fluids, and transfer to HDU. Fracture stabilisation performed urgently. Supportive care with DVT prophylaxis. Outcome: Over 5 days his respiratory and neurological status improve. He is discharged after 10 days with no lasting deficits.
• Case 2: A 70-year-old woman with osteoporosis fractures her pelvis after a fall. On day 2 she deteriorates with tachypnoea, hypoxia, and reduced GCS. She has widespread petechiae over her axillae and upper arms. Chest X-ray shows diffuse bilateral infiltrates.
  Management: Intubated and mechanically ventilated for severe hypoxaemia. Given cautious fluids, broad supportive ICU care, and fracture fixation after stabilisation. Outcome: Prolonged ICU stay complicated by pneumonia. Eventually weaned off ventilator after 3 weeks, but discharged with mild cognitive impairment and reduced exercise tolerance.

Teaching Commentary 🧑‍⚕️

FES is a systemic inflammatory response triggered by fat globules entering the bloodstream, usually after long-bone or pelvic fractures. Classic triad: respiratory distress, neurological changes, petechial rash. Case 1 demonstrates the typical timing (24–72 hrs post-injury) in a young trauma patient, with full recovery on supportive therapy. Case 2 shows more severe disease in an elderly, frail patient where outcomes are poorer. There is no specific antidote: management is supportive - oxygen, fluids, ventilation, and early fracture fixation. Corticosteroids are sometimes discussed but remain controversial in routine use.