Fat Embolism Syndrome (FES)

1. Introduction

Fat Embolism Syndrome (FES) is a life-threatening complication caused by fat globules entering the circulation and leading to multiorgan dysfunction, primarily affecting the lungs, brain, and skin. It is most commonly seen after long bone fractures (femur, tibia, pelvis), orthopedic surgeries, and trauma. Anesthesiologists must be vigilant as FES can cause sudden hypoxia, neurological deterioration, and cardiovascular instability in perioperative and critically ill patients.

2. Pathophysiology of Fat Embolism Syndrome

 Mechanical Theory

• Trauma/fracture → Bone marrow fat enters venous system

• Fat emboli obstruct pulmonary capillaries, causing:

• Pulmonary hypertension → Hypoxia

• Right heart strain → RV failure

• Systemic embolization → Microvascular occlusion in brain, kidneys, retina

 Biochemical Theory

• Fat undergoes lipolysis → Releases free fatty acids (FFA)

• FFA causes endothelial damage → Capillary leak syndrome

• Leads to pulmonary edema, ARDS, and systemic inflammation

3. Causes & Risk Factors of FES

 High-Risk Conditions

Condition	Risk
Long bone fractures (femur, tibia, pelvis)	Highest risk
Polytrauma, crush injury	High risk
Orthopedic surgery (intramedullary nailing, hip replacement)	Risk of embolization
Burns, fat grafting, liposuction	Rare but possible
Bone marrow transplantation	Fat mobilization

 Additional Risk Factors

• Young adults (more marrow fat in long bones)

• Hypovolemia (enhances fat embolization)

• Intramedullary instrumentation (reaming increases emboli release)

4. Clinical Features of FES

Classic triad of FES:

1. Pulmonary Symptoms (Hypoxia, ARDS, Tachypnea)

2. Neurological Symptoms (Confusion, Seizures, Coma)

3. Petechial Rash (Chest, axilla, conjunctiva)

 Pulmonary Manifestations (Most Common) – Seen in 75% Cases

Symptom	Mechanism
Hypoxia, Dyspnea, Tachypnea	Fat emboli in pulmonary capillaries → ARDS
Pulmonary Edema	Capillary leak due to free fatty acids
Respiratory Failure	Severe ARDS → Need for mechanical ventilation

 Neurological Manifestations

Symptom	Mechanism
Confusion, Agitation, Drowsiness	Cerebral fat emboli → Microvascular occlusion
Seizures, Coma	Severe embolization → Hypoxic brain injury

 Cutaneous Manifestations

Symptom	Mechanism
Petechial Rash (Chest, axilla, conjunctiva)	Fat emboli in dermal capillaries
Subconjunctival hemorrhage	Microvascular occlusion

 Other Features

• Tachycardia, hypotension (right heart strain)

• Fever, leukocytosis (inflammatory response)

• Retinal fat emboli (“Purtscher’s Retinopathy”)

5. Diagnosis of Fat Embolism Syndrome(Gurd’s & Wilson’s Criteria),Diagnosis: FES is confirmed if 1 major + 4 minor criteria are present.

Major Criteria:

✅ Respiratory distress (PaO₂ <60 mmHg, ARDS)

✅ Neurological dysfunction (confusion, coma)

✅ Petechial rash

Minor Criteria:

✅ Tachycardia (>120 bpm)

✅ Fever (>38.5°C)

✅ Fat globules in

✅ Fat globules in urine or sputum

✅ Retinal changes (Purtscher’s Retinopathy)

✅ Thrombocytopenia, anemia, elevated ESR

Laboratory Findings

Test	Findings in FES
Arterial Blood Gas (ABG)	Hypoxemia (PaO₂ <60 mmHg)
Chest X-ray	Bilateral infiltrates (ARDS-like)
CT Chest	Ground-glass opacities (Fat emboli in lungs)
MRI Brain (T2/FLAIR)	“Starfield” pattern – multiple emboli
CBC	Anemia, thrombocytopenia
Serum Lipase	Increased (due to fat metabolism)
Fat Staining (Urine, Sputum, BAL)	Sudan Black or Oil Red O positive fat globules

6. Anesthetic Considerations in Fat Embolism Syndrome

 Preoperative Management

✅ Identify High-Risk Patients: Fractures, Polytrauma, Liposuction, Orthopedic Surgeries

✅ Early Fracture Fixation: Reduces embolization risk

✅ Fluid Resuscitation: Prevents hypovolemia-induced fat embolization

✅ Steroids: May reduce inflammation (controversial)

Intraoperative Management

Aspect	Anesthetic Considerations
Induction	RSI if patient is critically ill, avoid hypoxia
Airway Management	Early intubation in severe cases
Ventilation	Lung-protective strategy (Low TV, PEEP) to prevent ARDS
FiO₂	Maintain SpO₂ > 92%
Circulation	Maintain MAP > 65 mmHg with fluids and vasopressors
Positioning	Supine to avoid embolization to systemic circulation
Monitoring	Invasive BP, ETCO₂, TEE (if available)

Anesthesia Choice:

• TIVA vs Volatile Agents: Both are acceptable, but propofol-based TIVA may be preferred for its anti-inflammatory effects.

• Neuromuscular Blockers: Use based on surgical need (avoid histamine-releasing agents like atracurium).

Postoperative Management

✅ ICU Admission for severe cases

✅ Mechanical Ventilation for ARDS

✅ DVT Prophylaxis (LMWH)

✅ Supportive Care (Fluids, Steroids, PEEP, Vasopressors)