Associated with Incidence of Trauma in Males (vs Females) (Orthopedics, 1996) [MEDLINE] (Am J Med Sci, 2008) [MEDLINE]
Age
Peak of Fat Embolism Incidence is Between 10-40 y/o
Associated with Incidence of Trauma in This Age Group
Etiology
Orthopedic (Common)
Long Bone Fracture
Epidemiology
Incidence of Fat Embolism Increases with Long Bone Fracture (Chest, 2021) [MEDLINE]
Incidence of Fat Embolism Increases with the Number of Fractures
Incidence of Fat Embolism with Multiple Fractures is Approximately (1.29%), as Compared to Incidence with Single Fracture (0.17%) (Am J Med Sci, 2008) [MEDLINE] (J Trauma, 2011) [MEDLINE]
Incidence of Fat Embolism Increases with Open (vs Closed) Fracture (Chest, 2021) [MEDLINE]
Delay in Time to Operation Increases the Risk of Fat Embolism (Chest, 2021) [MEDLINE]
Other Risk Factors for Fat Embolism Include Hypomagnesemia, Hyperphosphatemia, Hypoalbuminemia, and Blunt Traumatic Mechanism of Injury (Indian J Orthop, 2021) [MEDLINE]
Physiology
Subclinical Fat Emboli Routinely Occur During these Orthopedic Procedures (as Documented by Echocardiography and Pulmonary Artery Blood Samples)
In Dog Studies Using a Simulated Total Hip Replacement (Cemented Arthroplasty) Model, Fat Globules were Observed to Traverse the Pulmonary Circulation After Orthopedic Surgery (Being Found Intravascularly in the Brain, Heart, and Kidneys within 3 hrs), Despite the Absence of Any Intracardiac Shunt (Am J Resp Crit Care Med, 1994) [MEDLINE]
Interestingly, Solid Radiolabeled Microspheres (15 Microns in Diameter) Did Not Traverse the Pulmonary Circulation, Suggesting that the Deformability of Fat May Contribute to its Ability to Cross the Pulmonary Circulation
Pelvic Fracture
Epidemiology
XXXX
Fracture of Other Marrow-Containing Bones (Ribs, etc)
Trauma-Associated Fat Disruption from Bone Marrow or Adipose Tissue Subsequently Enters Torn Venules
Fat Embolism Sufficiently Explains the Respiratory Manifestations of Fat Embolism Syndrome Since Fat Globules Collect and Obstruct Pulmonary Capillaries
This May Resulting in Pulmonary Hypertension, Right Ventricular Failure, and Obstructive Shock
Circulating Fat Globules Have Prothrombotic Potential and May Trigger Platelet/Fibrin Aggregation, Resulting in Further Pulmonary Vascular Obstruction, Local Inflammation, Hemorrhage, and Edema
Mechanisms by Which Fat Emboli Enter the Systemic Arterial Circulation
Microembolism
Small Fat Emboli are Able to Pass from the Pulmonary Artery Through the Pulmonary Circulation to the Pulmonary Venous Circulation and Subsequently to the Left Side of the Heart
In the Absence of a Patent Foramen Ovale, Embolized Material Can Be Demonstrated in the Systemic Circulation
Paradoxical Embolism
Fat Emboli Pass Through a Patent Foramen Ovale or Other Anatomic Shunt Into the Arterial Circulation
Flaws with the Mechanical Theory
It Does Not Explain the 24-72 hr Interval Following the Inciting Insult Prior to Onset of the Symptoms of fat Embolism
It Does Not Explain Non-Traumatic Fat Embolism Syndrome
Biochemical Theory
Production of Toxic Intermediaries of Circulating Fat
Free Fatty Acids
Circulating Free Fatty Acids Levels are Moderately Elevated in Patients with Fractures
Circulating Free Fatty Acids are Severely Elevated (with Elevated Circulating Lipoprotein Lipase) in Non-Traumatic Animal Models of Fat Embolism Syndrome
Cytokines
High Levels of Phospholipase A2 and Inflammatory Cytokines (Tumor Necrosis Factor-α, Interleukin-1, and Interleukin-6) Can Be Found in Fat Embolism Syndrome
C-Reactive Protein
Elevated C-Reactive Protein is is Found in Fat Embolism Syndrome and is Likely Responsible for Lipid Agglutination, Resulting in Obstruction of Microvascular Blood Flow
Serum from Acutely Ill Patients Agglutinates Chylomicrons, Low Density Lipoproteins, and the Liposomes of Nutritional Fat Emulsions
Fat Emboli May Be Identified on Echocardiogram, as Flowing Hyperechoic Particles in the Inferior Vena Cava (Clin Pract Cases Emerg Med, 2021) [MEDLINE]
Swan-Ganz Catheter with Pulmonary Capillary Wedging is Not Routinely Used to Diagnose Fat Embolism
However, When a Swan-Ganz Catheter is Placed for Other Purposes, Fat Droplets May Occasionally Be Recovered from Blood Sampled at the Distal End of the Catheter
There is No Standard Criteria for Fat Analysis and Lack of Fat Does Exclude the Diagnosis of Fat Embolism
Bronchoscopy with Bronchoalveolar Lavage (BAL) (see Bronchoscopy)
Findings of Fat Droplets in Bronchoalveolar Lavage Fluid is Neither Sensitive Nor Specific for the Diagnosis of Fat Embolism
Fat Droplets May Also Be Present in Multiorgan Failure or Sepsis
Studies Performed in Patients with Trauma and the Acute Chest Syndrome of Sickle Cell Disease Suggest that Bronchoalveolar Lavage May Be Useful to Detect Fat Droplets (Ann Intern Med, 1990) [MEDLINE] (Blood, 1994) [MEDLINE] (Intensive Care Med, 1995) [MEDLINE] [MEDLINE] (Am J Respir Crit Care Med, 1996) [MEDLINE] (Intensive Care Med, 2006) [MEDLINE]
However, the Diagnostic Criteria Lack Standardization, and the Sensitivity/Specificity are Unknown (Similar Findings Can Be Demonstrated in Lipid Aspiration)
In a Trauma Study, Fat Embolism was Associated with a High Percentage (>30%) of Alveolar Macrophages Which Contain Lipid Inclusion Bodies (Intensive Care Med, 1995) [MEDLINE]
However, Some Patients with Non-Trauma Related Acute Respiratory Distress Syndrome (ARDS) Also Had Percentages of Alveolar Macrophages within This Range
Urine Sudan Fat Stain
Urine Sudan Fat Stain is Sensitive for the Presence of Fat, But Not Specific
Clinical Manifestations
General Comments
Onset of Symptoms
Symptoms May Occur Intraoperatively (During an Associated Procedure Where Fat Emboli May Occur), But More Commonly Occurs Gradually Around 12-72 hrs After the Inciting Event (Anaesthesia, 2001) [MEDLINE]
Diagnosis of Fat Embolism is Usually Clinical (J Bone Joint Surg, 1970)[MEDLINE]
However, Adjunctive Testing (Such as CT Pulmonary Artery Angiogram, Echocardiogram, etc) is Useful and Commonly Performed to Rule Out Other Diagnoses Which May Present Similarly to Fat Embolism
Pulmonary Hypertension with Right Ventricular Failure (Cor Pulmonale) (see Congestive Heart Failure)
Epidemiology
Acute Development of Pulmonary Hypertension with Right Ventricular Failure is Considered to Be a Component of the Classic Catastrophic “Fat Embolism Syndrome” (Anaesthesia, 2001) [MEDLINE] (Respir Med Case Rep, 2021) [MEDLINE]
Petechiae Occur in Up to 60% Cases (Anaesthesia, 2001) [MEDLINE]
Petechiae was Listed as Major Fat Embolism Criterion by Gurd (British Journal of Bone and Joint Surgery, 1974) [MEDLINE]
Physiology
Distribution May Be Explained by Fat Droplets Accumulating in the Aortic Arch Prior to Embolization to Nondependent Skin Via the Subclavian and Carotid Vessels (Anaesthesia, 2001) [MEDLINE]
Neurologic Signs (Confusion, Drowsiness, Coma) were Listed as Major Fat Embolism Criteria by Gurd (British Journal of Bone and Joint Surgery, 1974) [MEDLINE]
Physiology
Cerebral Fat Emboli May Occur Via Transit Through an Intact Pulmonary Arterial Circulation (Due to the Deformability of Fat Allowing it to Traverse These Vessels) or Via Transit Through a Patent Foramen Ovale (Am J Resp Crit Care Med, 1994) [MEDLINE] (Am Surg, 2022) [MEDLINE]
Cerebral Fat Embolism with Small Parenchymal Brain Infarcts
“Starfield” Pattern (on Diffusion-Weighted Imaging): diffuse punctate foci of restricted diffusion in bilateral white matter (predominantly in splenium of the corpus callosum and corticomedullary junction)
Correlates with the Degree of Clinical Neurologic Impairment
Respiratory Symptoms (Dyspnea, Tachypnoea, Bilateral Inspiratory Crepitations, Hemoptysis, Bilateral Infiltrates on Chest X-Ray) were Listed as Major Fat Embolism Criteria by Gurd (British Journal of Bone and Joint Surgery, 1974) [MEDLINE]
Fat Emboli May Be Identified on Echocardiogram, as Flowing Hyperechoic Particles in the Inferior Vena Cava (Clin Pract Cases Emerg Med, 2021) [MEDLINE]
Right Ventricular Hemodynamic Support with Inotropes, Pulmonary Vasodilators, and Mechanical Circulatory Support, etc May Be Necessary in Some Cases (Respir Med Case Rep, 2021) [MEDLINE]
Due to an Unclear Clinical Benefit and Defined Risk of Infection, Use of Corticosteroids (Hydrocortisone 100 mg TID intravenously or Methylprednisolone 1-1.5 mg/kg/Day) Should Be Carefully Considered (Surg Gynecol Obstet, 1966) [MEDLINE] (Surg Gynecol Obstet, 1971)[MEDLINE] (J Anesth, 2003) [MEDLINE]
Specific Treatment of Pulmonary Fat Embolism (with Acute Chest Syndrome) Associated with Sickle Cell Disease (see Sickle Cell Disease)
In Trauma Patients, the Presence of Fat Embolism Increases the Mortality Rate
In Trauma Patients, the In-Hospital Mortality Rate is 5.8% with Fat Embolism and 3.4% in Patients without Fat Embolism (P = 0.11) (Chest, 2021) [MEDLINE]
Mortality Rate
Mortality Rate Generally Ranges from 5-15% (Arch Emerg Med, 1991) [MEDLINE] (Anaesthesia, 2001) [MEDLINE] (Chest, 2021) [MEDLINE]
Some Studies Have Reported Mortality Rates as Low as 1.2% (Can J Surg, 2009) [MEDLINE]
When Death Occurs, it is Usually Due to Respiratory Failure, Refractory Shock, or Brain Death
References
General
Fat embolism: An aid to diagnosis. J Bone Joint Surg. 1970; 52B:732 [MEDLINE]
Do corticosteroids reduce the risk of fat embolism syndrome in patients with long-bone fractures? A meta-analysis. Can J Surg 2009; 52:386-393 [MEDLINE]
Cerebral fat embolism without intracardiac shunt: A novel presentation. J Emerg Trauma Shock. 2011 Apr;4(2):309-12 [MEDLINE]
Distinctive Acellular Lipid Emboli in Hemoglobin SC Disease following Bone Marrow Infarction with Parvovirus Infection. Case Rep Hematol. 2015;2015:328065. doi: 10.1155/2015/328065 [MEDLINE]
Cerebral fat embolism syndrome mimicking thrombotic thrombocytopenic purpura in a patient with hemoglobin SC disease. Am J Hematol. 2016 May;91(5):539-42. doi: 10.1002/ajh.24286 [MEDLINE]
Cerebral Fat Embolism in Hemoglobin SC Disease. Am J Med. 2017 May;130(5):e187-e189. doi: 10.1016/j.amjmed.2017.01.020 [MEDLINE]
Cerebral Fat Embolism via a Patent Foramen Ovale. Am Surg. 2022 Jul;88(7):1534-1536. doi: 10.1177/00031348221082270 [MEDLINE]
Fat embolism syndrome. Am J Med Sci. 2008 Dec;336(6):472-7 [MEDLINE]
Etiology
Fat embolism syndrome following bone marrow harvesting. Bone Marrow Transplant. 1991 Jun;7(6):485-6 [MEDLINE]
Transpulmonary systemic fat embolism. Studies in mongrel dogs after cemented arthroplasty. Am J Respir Crit Care Med. 1994 Nov;150(5 Pt 1):1416-22. doi: 10.1164/ajrccm.150.5.7952570. [MEDLINE]
Fat embolism syndrome. Am J Med Sci. 2008 Dec;336(6):472-7 [MEDLINE]
Incidence of pulmonary fat embolism at autopsy: an undiagnosed epidemic. J Trauma. 2011 Aug;71(2):312-5 [MEDLINE]
Fat embolism syndrome following percutaneous vertebroplasty: a case report. Spine J. 2014 Apr;14(4):e1-5 [MEDLINE]
Cerebral fat embolism syndrome following total knee replacement causing a devastating neurocognitive sequelae. Neurosciences (Riyadh). 2016 Jul;21(3):271-4 [MEDLINE]
Risk Factors of Fat Embolism Syndrome After Trauma: A Nested Case-Control Study With the Use of a Nationwide Trauma Registry in Japan. Chest. 2021;159(3):1064 [MEDLINE]
Risk Stratification Algorithm for Orthopedic Trauma Patients at Risk for Fat Embolism Syndrome. Indian J Orthop. 2021;55(4):879 [MEDLINE]
Diagnosis
Bronchoalveolar lavage for rapid diagnosis of the fat embolism syndrome in trauma patients. Ann Intern Med. 1990;113(8):583 [MEDLINE]
Pulmonary fat embolism: a distinct cause of severe acute chest syndrome in sickle cell anemia. Blood. 1994;83(11):3107 [MEDLINE]
Contribution of bronchoalveolar lavage to the diagnosis of posttraumatic pulmonary fat embolism. Intensive Care Med. 1995 Dec;21(12):973-80 [MEDLINE]
Bronchoalveolar lavage in adult sickle cell patients with acute chest syndrome: value for diagnostic assessment of fat embolism. Am J Respir Crit Care Med. 1996;153(5):1691 [MEDLINE]
Biochemical parameters of bronchoalveolar lavage fluid in fat embolism. Intensive Care Med. 2006;32(1):116. [MEDLINE]
The fat embolism syndrome. British Journal of Bone and Joint Surgery 1974; 56B: 408±16 [MEDLINE]
Fat embolism syndrome: Do the CT findings correlate with clinical course and severity of symptoms? A clinical-radiological study. Eur J Radiol. 2016 Feb;85(2):422-7 [MEDLINE]
Prevention
Do corticosteroids reduce the risk of fat embolism syndrome in patients with long-bone fractures? A meta-analysis. Can J Surg. 2009;52(5):386 [MEDLINE]
Treatment
The use of corticosteroids in the treatment of respiratory failure associated with massive fat embolism. Surg Gynecol Obstet. 1966;123(3):493 [MEDLINE]
Massive steroid therapy in severe fat embolism. Surg Gynecol Obstet. 1971;132(4):667 [MEDLINE]
Rapid improvement of respiratory symptoms associated with fat embolism by high-dose methylpredonisolone: a case report. J Anesth. 2003;17(3):186 [MEDLINE]
Supportive care of right ventricular failure due to fat embolism syndrome. Respir Med Case Rep. 2021 Aug 25;34:101499. doi: 10.1016/j.rmcr.2021.101499. eCollection 2021 [MEDLINE]
