Fat embolism syndrome

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Fat emboli
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Fat embolism syndrome
Other namesFat embolism
Supportive care[4]
Prognosis10% risk of death[2]
FrequencyRare[4]

Fat embolism syndrome occurs when

decreased level of consciousness, and shortness of breath.[1] Other symptoms may include fever and decreased urine output.[2] The risk of death is about 10%.[2]

Fat embolism most commonly occurs as a result of

bone marrow transplant, and liposuction.[3][2] The underlying mechanism involves widespread inflammation.[3] Diagnosis is based on symptoms.[2]

Treatment is mostly

intravenous fluids, albumin, and mechanical ventilation.[2] While small amounts of fat commonly occur in the blood after a bone fracture,[3] fat embolism syndrome is rare.[4] The condition was first diagnosed in 1862 by Zenker.[1]

Signs and symptoms

Symptoms of fat embolism syndrome (FES) can start from 12 hours to 3 days after diagnosis of the underlying clinical disease. The three most characteristic features are: respiratory distress, neurological features, and skin

petechiae.[5] Respiratory distress (present in 75% of the cases) can vary from mild distress which requires supplemental oxygen to severe distress which requires mechanical ventilation. For neurologic features, those who have FES may become lethargic, restless, with a drop in Glasgow Coma Scale (GCS) due to cerebral oedema rather than cerebral ischaemia. Therefore, neurological signs are not lateralised to one side of the body. In the severe form of cerebral edema, a person may become unresponsive. Petechiae rash usually happens in 50% of the patients. Such skin manifestation is temporary and can disappear within one day.[6] The fat embolism syndrome can be divided into three types:[5]

Causes

Orthopaedic injuries, especially fractures of the long bones, are the most common cause of fat embolism syndrome (FES). The rates of fat embolism in long bone fractures vary from 1% to 30%. The mortality rate of fat-embolism syndrome is approximately 10–20%.[7] However, fat globules have been detected in 67% of those with orthopaedic trauma and can reach as high as 95% if the blood is sampled near the fracture site. As the early operative fixation of long bone fractures became a common practice, the incidence of FES has been reduced to between 0.9% and 11%.[6]

Osteomyelitis

Other rare causes of fat embolism syndrome are:[7][6]

  • Severe burns
  • Liver injury
  • Closed chest cardiac massage (during cardiopulmonary resuscitation)
  • Bone marrow transplantation
  • Liposuction
  • Parenteral lipid infusion
  • Decompression sickness
  • Extracorporeal circulation
  • Acute haemorrhagic pancreatitis
  • Alcoholic liver disease
  • Prolonged corticosteriod therapy
  • Sickle cell disease
  • Carbon tetrachloride poisoning
  • Osteomyelitis

Pathophysiology

Histopathology of a pulmonary artery with fat embolism (seen as multiple empty globular spaces on this H&E stain since its processing dissolves fat). There is a bone marrow fragment in the middle, and multiple single hematopoietic cells in the blood, being evidence of fracture as the source of the embolism.

Once fat emboli enter the blood circulation, they can lodge at various sites of the body, most commonly in the lungs (up to 75% of cases). However, it can also enter the brain, skin, eyes, kidneys, liver, and heart circulation, causing capillary damage, and subsequently cause organ damage in these areas. There are two theories that describe the formation of a fat embolus:[6]

Diagnosis

Separator for hematocrit

Fat embolism is presence of fat particles in the micro-circulation of the body. Meanwhile, fat embolism syndrome is the clinical manifestation as the result of fat particles lodging in the body micro-circulation.[6] There are three major diagnostic criteria proposed for fat embolism syndrome, however, none of them are validated and accepted universally.[6] However, Gurd and Wilson's criteria for fat embolism become more commonly used when compared to the other two diagnostic criteria.[9]

Gurd and Wilson's criteria

Major criteria[6][7][9]

  • Axillary or subconjunctival petechiae
  • Hypoxaemia PaO2 <60 mm Hg, FIO2 = 0.4
  • Central nervous system depression disproportionate to hypoxaemia
  • Pulmonary oedema

Minor criteria[6][7][9]

  • Tachycardia more than 110 beats per minute
  • Pyrexia more than 38.5 °C
  • Fat globules present in urine
  • Changes in renal function (reduced urine output)
  • Drop in
    haemoglobin
    values (more than 20% of the value upon admission)
  • Drop in
    haematocrit
    values
  • Drop in platelet values (more than 50% of the value upon admission)
  • Increasing erythrocyte sedimentation rate (ESR) (greater than 71 mm per hour)
  • Fat globules present in the sputum
  • Emboli present in the retina on fundoscopy

A least two positive major criteria plus one minor criteria or four positive minor criteria are suggestive of fat embolism syndrome.[6] Fat embolism syndrome is a clinical diagnosis. There are no laboratory tests sensitive or specific enough to diagnose FES. Such laboratory tests are only used to support the clinical diagnosis only.[7] Chest X-ray may show diffuse interstitial infiltrates while chest CT scan will show diffuse vascular congestion and pulmonary oedema. Bronchoalveolar lavage has been proposed to look for fat droplets in alveolar macrophages however it is time-consuming and is not specific to fat embolism syndrome. Looking for fat globules in sputum and urine is also not specific enough to diagnose FES.[6]

Prevention

For those treated conservatively with immobilisation of long bone fractures, the incidence of FES is 22%. Early operative fixation of long bone fractures can reduce the incidence of FES especially with the usage of internal fixation devices. Patients undergoing urgent fixation of long bone fractures has a rate of 7% of acute respiratory distress syndrome (ARDS) when compared to those undergoing fixation after 24 hours (39% with ARDS). However, movement of the fracture ends of the long bones during the operative fixation can cause transient increase of fat emboli in the blood circulation. Cytokines are persistently elevated if the long bone fractures is treated conservatively using immobilisation. The cytokine levels would return to normal after operative fixation. Although ream nailing increases pressure in the medullary cavity of the long bones, it does not increase the rates of FES. Other methods such as drilling of holes in the bony cortex, lavaging bone marrow prior to fixation, and the use of tourniquets to prevent embolisation have not been shown to reduce the rates of FES.[6]

Corticosteroid therapy such as methylprednisolone (6 to 90 mg/kg) has been proposed for the treatment of FES, however, it is controversial. Corticosteroid can be used to limit free fatty acid levels, stabilising membranes, and inhibit leukocyte aggregation. A meta-analysis conducted in 2009 reported prophylactic corticosteroids can reduce the risk of FES by 77%. However, there is no difference in mortality, infection, and avascular necrosis when compared to the control group. However, a randomised trial conducted in 2004 reported no differences in FES incidence when comparing treatment with the control group.[6] Administration of corticosteroids for 2 to 3 days is not associated with increased rates of infection.[5] However, there is insufficient data to support the use of methyprednisolone once FES is established.[5]

Heparin has been used in the prevention of venous thrombosis in post-operative patients; however its regular use in those with FES has been contraindicated due to increase risk of bleeding in those with polytrauma.[5] Placement of inferior vena cava filters has been proposed to reduce the amount of emboli going into the lung vascular system, however, this method has not been studied in detail.[6]

Treatment

Serum albumin

Once FES develops, the person should be admitted into

Glasgow coma scale (GCS) charting is required to assess the neurological progression of a person with FES. A placement of intracranial pressure monitor may be helpful to direct the treatment of cerebral odema.[6]

History

In 1861, Zenker first reported on the autopsy findings of fat droplets found in the lungs of a railway worker who died due to severe thoraco-abdominal crush injury. In 1873, Bergmann diagnosed fat embolism clinically in a patient with fractured femur. In 1970, Gurd defined the characteristics of this phenomenon.[7] Gurd later modified the fat embolism criteria together with Wilson, thus producing Gurd and Wilson's criteria for fat embolism syndrome in 1974.[7] In 1983, Schonfeld suggested a scoring system for the diagnosis of fat embolism syndrome. In 1987, Lindeque proposed another scoring system that diagnose fat embolism syndrome by using respiratory changes alone. However, none of them have become universally accepted in the medical community.[6]

In 1978, Formula One racing driver Ronnie Peterson died from FES, after sustaining multiple fractures in a racing accident.

In 2015, Singaporean couple Pua Hak Chuan and Tan Hui Zhen were charged with the abuse and

murder of Annie Ee Yu Lian, who died due to multiple physical abuses which lasted for eight months before her death. The cause of death was revealed to be acute fat embolism, which resulted from the blunt force impact caused by the beatings, which led to the fatty tissue entering the bloodstream and eventually entering the blood vessels in the lungs, which led to a blockage and cut off the circulation of oxygenated blood and led to Ee's death by respiratory and cardiac failure. Two years later, for reduced charges of voluntarily causing grievous hurt with a weapon, Tan was sentenced to 16 years and six months in jail while Pua received 14 years' imprisonment and 14 strokes of the cane.[10][11]

References

  1. ^
    PMID 19825491
    .
  2. ^ a b c d e f g h i Laurence, Knott (19 February 2014). "Fat embolism syndrome". patient.info. Retrieved 14 March 2018.
  3. ^
    PMID 29763060
    .
  4. ^
    S2CID 51969468
    .
  5. ^
    PMID 23661916
    .
  6. ^
    PMID 23724388
    .
  7. ^
    S2CID 8190157
    .
  8. ISSN 1743-1816
    .
  9. ^
    PMID 18702388
    . Retrieved 14 March 2018. Diagnosis is usually made on the basis of clinical findings but biochemical changes may be of value. The most commonly used set of major and minor diagnostic criteria are those published by Gurd (See Table 2 ).
  10. ^ "14, 16.5 years' jail for couple who tortured tenant to death". Today. Singapore. 1 December 2017. Retrieved 20 April 2022.
  11. ^ "AGC replies to questions raised by the public". The Straits Times. Singapore. 19 December 2017. Retrieved 20 April 2022.

Further reading

External links

Scholia has a topic profile for Fat embolism syndrome.
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