Diagnosis
Fat embolism syndrome
A rare life-threatening acute respiratory distress syndrome caused by release of fat droplets from the marrow as may occur following a long bone fracture.
Etiology
Causes [cth]
Traumatic: Long bone fracture (pelvis, femur), Burns, Cardiopulmonary bypass, Decompression sickness, organ transplant (lung, renal), bone marrow harvesting, liposuction, chest compressions, Bone marrow transplantation, liposuction, median sternotomy
Non-traumatic: Severe infection, Pancreatitis, Osteomyelitis, Bone tumor lysis, Osteonecrosis, Bone marrow necrosis, Steroid therapy, Inhalation anesthesia, Metabolic disorders, Sickle cell Hemoglobinopathy, collagen disease, diabetes mellitus, fatty liver disease, cardiopulmonary bypass, thalassemia
Patophysiology [uam][cth]
Fat embolizes to the lungs --> local release of lipase breaks fat down into free fatty acids and glycerol
Free fatty acids are toxic to endothelial cells --> inflammatory response --> vasogenic edema and hemorrhage
Fat globules in the blood circulation:
Mechanical obstruction
Vascular damage due to biochemical/toxic injury
Platelet activation (DIC)
Increased vascular permeability --> pulmonary edema
The classic clinical triad
Respiratory insufficiency (pulmonary fat embolism) --> dyspnea (95%)
Neurological impairment (systemic fat embolism) --> confusion (60%)
Skin rash (systemic fat embolism) --> Petechiae (33%)
Risk factors [nch]
Young age
Femur fracture
Obesity
Diabetes
Mortality: 11.8% [uam]
Epidemiology
Incidence per 100.000 [uam][tao][4vn]
Symptoms & findings
Symptoms
Anisocoria, Anuria, Aphasia, Apraxia, Burns, Coma, Confusion, Cyanosis, Decreased consciousness, Delirium, Dyspnea, Fever, Headache, Hemiplegia, Malaise, Nausea, Oliguria, Petechia, Restlessness, Seizure, Stupor, Tachycardia, Tachypnea, Visual disturbances, Weakness
Clinical findings
Anemia, Decreased Albumin, Decreased hematocrit, Elevated CRP, Elevated Lipase, Fat macroglobulinemia, Hypocalcemia, Hypocapnia, Hypoxemia, Lipiduria, Snow storm pattern, Thrombocytopenia
Anamneses
Localized findings
Approach
There are no reliably accurate diagnostic or imaging test. Rather, the diagnosis is primarily clinical. [7mn]
Blood gas
Chest X-ray
Cryostat
Urine analysis
Urine cytology
Ultrasound / echocardiography
Bronchoalveolar lavage
CT thorax
Magnetic resonance imaging
Diagnostic Criteria [cth]
2 major criteria or at least one major criteria and 4 minor criteria
Major Criteria
Petechial rash
Respiratory insufficiency
Cerebral involvement in non-head injury patients
Minor Criteria
Fever greater than 38.5 C
Tachycardia heart rate greater than 110 beats per minute
Retinal involvement
Jaundice
Renal signs
Anemia
Thrombocytopenia
High erythrocyte sedimentation rate
Fat macroglobulinemia
Treatment
Prevention: Early immobilization and fixation within 48 hours [nch]
Treatment is mainly supportive
Intravenous fluids
Respiratory support
Oxygen: maintain a high PaO2 level
Mechanical ventilation
Hydration
Corticosteroids?
Nutritional support/GI prophylaxis
Glucosecontrol
Sedation/paralysis
VTE prophylaxis
Hemodynamic monitoring
Control causes of sepsis
Prevent aspiration/pneumonia
Treat underlying injuries/organ dysfunction
Prone positioning
ECMO
Differential diagnoses
Acute respiratory distress syndrome, Air embolism, Amniotic fluid embolism, Brain tumor, Disseminated intravascular coagulation, Encephalitis, Heart failure, Immune thrombocytopenic purpura, Leukemia, Meningitis, Pneumonia, Pulmonary edema, Pulmonary embolism, Pulmonary hemorrhage, Thrombotic thrombocytopenic purpura
References
[1] Adeyinka A, Pierre L. Fat Embolism. [Updated 2022 Oct 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499885/
[2] Tsai SHL, Chen CH, Tischler EH, Kurian SJ, Lin TY, Su CY, Osgood GM, Mehmood A, Fu TS. Fat Embolism Syndrome and in-Hospital Mortality Rates According to Patient Age: A Large Nationwide Retrospective Study. Clin Epidemiol. 2022 Aug 19;14:985-996.
[3] Owattanapanich N, Lewis M, Biswas S, Benjamin ER, Demetriades D. Epidemiology and risk factors for fat embolism in isolated lower extremity long bone fractures. Eur J Trauma Emerg Surg. 2024 Apr 17.
[4] Bulger EM, Smith DG, Maier RV, Jurkovich GJ. Fat embolism syndrome. A 10-year review. Arch Surg. 1997 Apr;132(4):435-9.
[5] Tsai IT, Hsu CJ, Chen YH, Fong YC, Hsu HC, Tsai CH. Fat embolism syndrome in long bone fracture--clinical experience in a tertiary referral center in Taiwan. J Chin Med Assoc. 2010 Aug;73(8):407-10.
[6] Shaikh N, Mahmood Z, Ghuori SI, Chanda A, Ganaw A, Zeeshan Q, Ehfeda M, Mohamed Belkhair AO, Zubair M, Kazi ST, Momin U. Correlation of clinical parameters with imaging findings to confirm the diagnosis of fat embolism syndrome. Int J Burns Trauma. 2018 Oct 20;8(5):135-144.
[7] http://emedicine.medscape.com/article/460524 (2014-01-02); [Medscape]
[8] Sirbu O, Sorodoc V, Floria M, Statescu C, Sascau R, Lionte C, Petris OR, Haliga RE, Morariu PC, Tirnoveanu A, et al. Nontrombotic Pulmonary Embolism: Different Etiology, Same Significant Consequences. Journal of Personalized Medicine. 2023; 13(2):202.
[9] Jorens PG, Van Marck E, Snoeckx A, Parizel PM. Nonthrombotic pulmonary embolism. Eur Respir J. 2009 Aug;34(2):452-74.