Pulmonary fat embolism

Pulmonary fat embolism is a specific sub type of pulmonary embolism. The embolic particles are composed of fat.

Pathology

It usually occurs in the context of a long bone fracture and matmay occur in 1-3% of patients with simple tibial or femoral fractures and up to 20% of individuals with more severe trauma. Other less common causes include:

• haemoglobinopathy
• major burns
• pancreatitis
• overwhelming infection
• tumours
• blood transfusion liposuction 

The exact mechanism is not entirely clear but presumably occurs fro,from one of two methods. The first is the production of free fatty acids, which initiates a toxic reaction in the endothelium. This process is further complicated by accumulation of neutrophils and other inflammatory cells, which cause damage to vasculature. The other mechanism is a mechanical obstruction of the pulmonary vasculature by fat globules, aggregates of red blood cells and platelets.

Markers

Urine analysis for fat globules may be useful in the setting of large pulmonary fat embolism.

Radiographic features

Plain radiograph

Non specific but can resemble those in acute respiratory distress syndrome from any cause, and consist of widespread homogeneous and heterogeneous areas of increased opacity. A normal heart size and the absence of other features of cardiogenic oedema (septal lines, pleural effusion, and pulmonary venous hypertension may aid differentiation from noncardiogenic pulmonary oedema).

CT

Commonly reported findings include (each non specific on their own):

• areas of consolidation
• ground-glass opacities: can occur with a geographic distribution and or in association with interlobular septal thickening ⁷
• small (<1 cm) nodules of various sizes: presumed to represent alveolar oedema or haemorrhage secondary to the fat embolism syndrome ^5,6

Filling defects in pulmonary arteries are rarely described in non fulminant syndromes.

Treatment and prognosis

Treatment options include maintaining good arterial oxygenation and maintenance of intravascular volume. Albumin has sometimes been recommended for volume resuscitation in addition to balanced electrolyte solution as it can bins with the fatty acids and in turn may decrease the extent of lung injury ⁸. Mechanical ventilation and PEEP may be required in certain cases. The prognosis is variable.

See also

• fat embolism syndrome