f Post graduate mcqs and discussion : Fat embolism

Friday, March 23

Fat embolism

Most serious complications,  the essential features being occlusion of small vessels by fat globules.

Causes : fat globules may originate from bone marrow or adipose tissue.  Fat embolism is more common following severe injuries with multiple fractures and fracture of major bones . The pathogenesis of the syndrome is not clear but seems likely that two events occur :

(1 ) release of free fatty acids  ( by action of lipases on the neutral fat) , which induces a toxic vasculitis,  followed by platelets -fibrin thrombosis.

(2) actual obstruction of small pulmonary vessels by fat globules.

Consequences : symptoms are evident a day or so after the injury.  Presenting features are in the form of  two or more or less distinct type :

A. Cerebral type : the patients become drowsy,  restless,  and disoriented and gradually goes into state of coma.

B. Pulmonary type: tachypnoea and tachycardia are the most prominent features.

The other common features of fat embolism are petechial rashes, usually on the front of neck , anterior axillary folds , chest and conjuctiva . If untreated and sometimes despite treatment,  the patient develops respiratory failure and dies .

Diagnosis : in a case with multiple fractures,  early diagnosis may be possible by strong suspicion.  In addition to the classic clinical features,  signs of retinal artery emboli ( straited haemorrhages  and exudate ) may be present.  Sputum and urine may reveal the presence of fat globules.  X-rays of chest may show a  patchy pulmonary infiltration
( snow storm appearance ) . Blood po2 of less than 50 mm Hg may indicate impending respiratory failure.

Treatment : this consists of respiratory support,  heparinisation , intravenous low molecular Wight dextran and corticosteroids.  An intravenous 5 percent dextrose solutions with 5 percent alcohol helps in emulsification of fat globules.