FAT EMBOLISM SYNDROME

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.

Pathophysiology: 2 Theories-

  1. Mechanical Theory:  Initial Symptoms, by mechanical occlusion of multiple blood vessels with fat globules (Triglyceride particles occlude the microvessels of lungs & other tissues)
  2. Biochemical Theory: Late Presentation, 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).

Causes/Etiology: 

  • Fractures- long bone fractures; Pelvic fractures; Polytrauma
  • Orthopaedic Procedures
  • Massive Soft tissue Injury
  • Severe Burns
  • Bone Marrow Biopsy
  • Bone marrow harvesting & transplant
  • Non-traumatic causes-
    -Liposuction
    -Sickle Cell Disease
    -Bone tumour Lysis
    -Fatty Liver
    -Prolonged Corticosteroid Therapy
    -Osteomyelitis
    -Acute Pancreatitis
    -Lipid Infusion
    -Cyclosporine A solvent

             

Differential Diagnosis:

  • Bronchopneumonia
  • Pulmonary Embolism
  • Septicemia
  • Head Injury
  • Diabetic Coma
  • Shock

DIAGNOSIS:

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

INVESTIGATION: 

  1. Cytological Examination of Urine, Blood, Sputum, BAL (bronchoalveolar lavage)- detect Fat globules.
  2. Chest Xray-  “Snow Storm 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.

Classification:

Sevitt Classification of FES (Fat Embolism Syndrome)- 3 types

  1. Subclinical FES:
    -Fat emboli present in blood & Lungs,
    -No clinical signs/symptoms
  2. Non-Fulminant FES:
    -Respiratory Insufficiency,
    -Cerebral changes,
    -Petechie,
    -Laboratory changes.
  3. Fulminant FES:
    -rare,
    -develops within hours,
    -Respiratory failure,
    -Altered Mental status.

FES vs CEREBRAL INJURY:

 

MANAGEMENT: Supportive & Symptomatic

  • Ensuring good Arterial Oxygenation.
  • High flow O2 to be given.
  • Restriction of fluid intake + Use of Diuretics- minimize fluid accumulation in lungs.
  • 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).
Related articles: Fat embolism (FE) and fat embolism syndrome (FES):https://www.ncbi.nlm.nih.gov/books/NBK499885/