Define Fat Embolism Syndrome. Describe its pathogenesis, clinical features, investigations and management.

Definition

Fat embolism syndrome (FES) is a clinical condition in which fat globules enter the circulation and lodge in the pulmonary and systemic capillaries, causing a characteristic triad of respiratory, cerebral and cutaneous features. It classically follows fractures of long bones and the pelvis (especially the femoral shaft) in young adults, typically 24–72 hours after injury.

Pathogenesis

Two theories are combined: the mechanical theory (marrow fat released from the fracture enters torn venous sinusoids and embolises to the lungs) and the biochemical theory (free fatty acids generated from these globules cause a toxic vasculitis and ARDS-like alveolar damage).

Clinical Features (gurd's Criteria)

Major criteria: respiratory insufficiency (tachypnoea, hypoxia, ARDS), cerebral involvement (confusion, drowsiness, restlessness) and a petechial rash (over the conjunctivae, axillae, neck and chest). Minor criteria include fever, tachycardia, retinal changes, fat in the urine/sputum, thrombocytopenia and a falling haematocrit. The petechial rash is the most specific sign.

Investigations

The diagnosis is clinical (Gurd's criteria); no single test is confirmatory. Supportive findings include hypoxaemia on arterial blood gas (a falling PaO₂ is often the earliest objective clue), thrombocytopenia and anaemia, patchy bilateral infiltrates on the chest radiograph (‘snowstorm’ appearance), and fat globules in the urine or sputum. A high index of suspicion in the at-risk patient is more valuable than any test.

Management

Treatment is largely preventive and supportive. Prevention: adequate resuscitation, early splintage and early operative stabilisation of long-bone fractures reduce the incidence. Supportive care is the mainstay — oxygen to maintain saturation, and ventilatory support (CPAP/mechanical ventilation) for respiratory failure, with fluid balance and general intensive care. Steroids have a debated prophylactic role. Most patients recover fully with timely supportive care.

Early fracture fixation reduces the incidence.

• Follows long-bone/pelvic fractures, 24–72 h later, in young adults.
• Triad: respiratory (hypoxia/ARDS), cerebral (confusion) and petechial rash.
• Gurd's criteria; petechiae are the most specific feature.
• Prevent with early fracture stabilisation; treat supportively with oxygen/ventilation.