Fat embolism

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A fat embolism is a type of embolism in which the embolus consists of fatty material. They are often caused by physical trauma such as fracture of soft tissue trauma, and burns.

Video Fat embolism

Signs and symptoms

The severe form of this condition presents as acute pulmonary heart disease and respiratory failure. This may lead to death within a few hours of injury.Clinical fat embolism syndrome presents with tachycardia, tachypnea, elevated temperature, hypoxemia, hypercapnia, thrombocytopenia, and occasionally mild neurological symptoms.A petechial rash also called purpura that appears on the upper anterior portion of the body, including the chest, neck, upper arm, axilla, shoulder, oral mucosa and conjunctivae is considered to be a pathognomonic sign of fat embolism syndrome, however it appears late and often disappears within hours. It results from occlusion of dermal capillaries by fat, and increased capillary fragility.Central nervous system signs, including a change in level of consciousness, are not uncommon. They are usually nonspecific and have the features of diffuse encephalopathy: acute confusion, stupor, coma, rigidity (neurology), or convulsions. Cerebral edema contributes to the neurologic deterioration. Unlike emboli that arise from blood clots, fat emboli are small and multiple, and thus have widespread effects.

Fat embolism syndrome is distinct from the presence of fat emboli, symptoms usually occur 1-3 days after a traumatic injury and are predominantly pulmonary (shortness of breath, hypoxemia), neurological (agitation, delirium, or coma), dermatological (petechial rash), and haematological (anaemia, low platelets). The syndrome manifests more frequently in closed fractures of the pelvis or long bones. The petechial rash, which usually resolves in 5-7 days, is said to be pathognomonic for the syndrome, but only occurs in 20-50% of cases

Complications

Embolized fat travels through the venous system to the lungs and can occlude pulmonary capillaries, fat emboli may cause cor pulmonale if adequate compensatory pulmonary vasodilation does not occur.Circulating free fatty acids are directly toxic to pneumocytes and capillary endothelium in the lung, causing interstitial hemorrhage, edema and chemical pneumonitis.Complications from a fat embolism can be serious:

1. Pulmonary fat embolism: Obstruction causes sudden death.
2. Systemic fat embolism: These may get lodged in capillaries of organs like the brain, kidneys, or skin, causing minute hemorrhage and microinfarcts.

Maps Fat embolism

Cause

Fat emboli occur in almost 90% of all people with severe injuries to bones, although only 10% of these are symptomatic. The risk of fat embolism syndrome is thought to be reduced by early immobilization of fractures and especially by early operative correction. There is also some evidence that steroid prophylaxis of high-risk individuals reduces the incidence. The mortality rate of fat-embolism syndrome is approximately 10-20%.

Fat emboli can be either traumatic (resulting from fracture of long bones, accidents, or trauma to soft tissue) or non-traumatic (resulting from burns or fatty liver).

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Pathogenesis

The pathogenesis occurs due to both mechanical obstruction and biochemical injury, it is aggravated by local platelet and erythrocyte aggregation. The release of fatty acids from the fat globules also causes local toxic injury to endothelium, the vascular damage is aggravated by platelet activation and recruitment of granulocytes.Several mechanisms have been proposed to explain the pathogenesis of fat embolism:

1. Mechanical. Mobilisation of fluid fat following trauma to bone and soft tissue.
2. Emulsion instability. Fat embolus formed by aggregation of plasma lipids (chylomicrons and fatty acids) due to disturbances in emulsification of fat. Symptoms include fatty liver (hepatic steatosis).
3. Intravascular coagulation. May result from disseminated intravascular coagulation (DIC).
4. Toxic injury. Blood vessels injured by high plasma levels of free fatty acid, results in increased vascular permeability and consequently pulmonary edema.

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Diagnosis

The diagnosis of an individual suspected of having FES can be done via the following:

• Transesophageal echocardiography (TEE)
• Cytologic examination of urine,and blood
• Decreased hematocrit occurs within 1 to 2 days
• MRI (brain)
• chest X-ray may show pulmonary shadows
• Hypoxemia may occur in an individual with FES(PaO2 <60 mmHg)
• Doppler ultrasonography

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Treatment

Treatment for this condition entails the maintenance of intravascular volume. Additionally, the following can be done as a means of managing FES in an individual:

• Albumin can be used for volume resuscitation
• Long bone fractures should be attended to immediately (surgery)
• Mechanical ventilation

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See also

• Air embolism
• Cholesterol embolism
• Pulmonary embolism
• CT pulmonary angiogram

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References

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Further reading

• Shaikh, Nissar (2009). "Emergency management of fat embolism syndrome". Journal of Emergencies, Trauma and Shock. 2 (1): 29. doi:10.4103/0974-2700.44680. ISSN 0974-2700. Retrieved 26 November 2017. 
• Kwiatt, MichaelE; Seamon, MarkJ (2013). "Fat embolism syndrome". International Journal of Critical Illness and Injury Science. 3 (1): 64. doi:10.4103/2229-5151.109426. ISSN 2229-5151. Retrieved 26 November 2017. 

Source of the article : Wikipedia