Fat Embolism Syndrome (FES)

Fat embolism syndrome:
a) Pathophysiology. [3]
b) Clinical features and diagnosis. [3]
c) Management of fat embolism in a case of closed fracture shaft femur. [4]


[Dfn: It is an inflammatory response to embolic fat macroglobules passing into the small vessels of the lungs & other organs producing endothelial damage which results into respiratory complications, cerebral dysfunction & petechial rashes.]

a) Pathophysiology:

Fat globules, released from the primary organ(s), enter the microcirculation & damage the capillary beds causing the microcirculatory hemostasis in the following organs:

  • Brain
  • Skin
  • Eyes
  • Heart

Two main theories for the development of FES:

  1. Mechanical Theory (Gassling et al):  Initial Symptoms, by mechanical occlusion of multiple blood vessels with fat globules (Triglyceride particles occlude the microvessels of lungs & other tissues)-
    Release of large fat droplets into the venous system ⇒ reached the pulmonary capillary bed ⇒ travel to the brain via the A-V shunt (deformable fat droplets can transverse the pulmonary vasculature)
    Pathophysiological changes–

     

    • Elevated pulmonary artery pressure
    • Impairment of oxygen exchange from ventilation-perfusion mismatch
    • Systemic effects on end-organs such as the brain, kidney, and skin.
  2. Biochemical Theory (Baker et al): Late Presentation,
    Precipitating event (traumatic or nontraumatic) ⇒ Hormonal change in the body system ⇒ release of free fatty acid (FFA) & chylomicrons, a result of hydrolysis of fat (by Pneumocyte Lipases) into more irritating/inflammatory toxic ‘free fatty acids‘ which migrate to other organs & tissues (Systemic circulation) ⇒ Multiple organ dysfunction syndromes.

b) Clinical Features & Diagnosis:

Clinical Features:  Symptoms and Signs

  • Symptoms: 
    • Pain related to bone fracture
    • Nausea
    • General weakness
    • Malaise
    • Difficulty breathing
    • Headache
  • Signs: 
    • Respiratory:
      -Tachypnea
      -Tachycardia
      -Diaphoresis
    • Central nervous system:
      -Agitation from hypoxia
      -Restlessness
      -Change in mental status
      -Seizure
      -Coma
    • Skin:
      -Petechial rash
    • Eye:
      -Retinal hemorrhage

Diagnosis: Diagnosis of fat embolism syndrome can be particularly challenging. There are several diagnostic criteria-

Gerd’s Criteria–

MAJOR (M): 

  1. Respiratory Insufficiency
  2. Cerebral Involvement
  3. Petechial Rashes

MINOR (m): 

  1. Pyrexia (>39.40C)
  2. Tachycardia (>120/min)
  3. Retinal Changes
  4. Renal Changes- oliguria, anuria
  5. Hepatic Changes(Jaundice)

LABORATORY FEATURES (L):

  1. Fat Macroglobulinemia
  2. Anaemia (decreased Haematocrit)
  3. Thrombocytopenia
  4. Increased ESR

Diagnosis: – 1M+4m+1L

Schoenfeld Criteria-quantitative means for the diagnosis of fat embolism syndrome:

Diagnosis: – cumulative score >5 is required.

  • 5 points – petechiae rash
  • 4 points – diffuse infiltrate on x-ray
  • 3 points – hypoxemia
  • 1 point (for each) – fever, tachycardia, confusion

Lindeque Criteria: not used frequently.

INVESTIGATION: 

  1. Cytological Examination of Urine, Blood, Sputum, BAL (bronchoalveolar lavage)- detect Fat globules.
  2. Chest Xray- “Snowstorm Appearance ” (B/L Fluffy appearance)
  3. Blood Gas Analysis- paO2 <60mm Hg
  4. Thrombocytopenia
  5. Decreased Hematocrit
  6. Increased Lipase
  7. Brain MRI- foci of vasogenic oedema in a random (i.e. embolic) distribution; A “starfield” pattern may be seen on DW imaging.

MANAGEMENT: 

c) Management of fat embolism in a case of closed fracture shaft femur:

—Prevention of Fat Embolism in Closed femur fracture:

  • Early fixation of fracture femur
  • During fixation of the femur fracture, care must be taken to limit the intramedullary pressure, (a high pressure is associated with an increased amount of fat emboli entering the systemic circulation).

  • Some techniques in orthopedic surgery to reduce embolization include: (not proven)

    • Lavage of bone marrow prior to fixation
    • Venting of the femoral bone
    • Drilling of small holes in the cortex of the bone to lower intramedullary pressure
  • Monitoring of the pt. for developing symptoms of FES for early intervention.
  • screening for symptoms of FES in the pre-operative work-up, prior to definitive fixation of major fractures.

—Treatment Fat Embolism Syndrome in Closed femur fracture:
The mainstay treatment once a patient develops fat embolism syndrome is Supportive & Symptomatic. 


Goals of Supportive Care-

  • Provision of adequate oxygenation & ventilation
  • Maintenance of adequate hemodynamic stability
  • Transfusion of packed RBC to improve oxygen delivery if indicated
  • Prophylaxis of DVT with a SCD (sequential compression device)
  • Adequate nutrition & hydration

Treatment includes: –

  • Ensuring good Arterial Oxygenation.
  • High flow O2 to be given.
  • Restriction of fluid intake + Use of Diuretics- minimize fluid accumulation in lungs (in case of pulmonary oedema)
  • Volume resuscitation with Albumin & Balanced Electrolyte Solution – Albumin restores blood volume; binds ‘free fatty acids’ & decreases the extent of lung injury.
  • Mechanical Ventilation & PEEP (Post End Expiratory Pressure).

  • Cerebral edema if present might require-

    • Mannitol
    • Hypertonic salin
    • Intracranial pressure monitors

 

Also see: 

Causes/Etiology: 

Differential Diagnosis:

Classification:

FES vs CEREBRAL INJURY:

 

 

Read more:  Fat embolism (FE) and fat embolism syndrome (FES):https://www.ncbi.nlm.nih.gov/books/NBK499885/

 

 

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