Chest radiography may show rib fractures or pulmonary contusion. However, approximately a third of patients who develop fat embolism syndrome have additional radiographic changes most often characterized by diffuse parenchymal infiltrates ( Fig 2). Unfortunately, these signs bear little relationship to disease severity or even blood gas parameters. Although not diagnostic, serial chest radiographs are advised and, combined with other investigations, provide useful guidance for diagnosis and the effects of injury.
Fig. 2 Two chest radiographs of a case of fat embolism syndrome: (a) a normal film taken after admission; (b) a film taken 18 h later showing diffuse pulmonary infiltrates consistent with a diagnosis of fat embolism syndrome.
Since neurological features take many forms, there should be early recourse to CT. This may allow exclusion of direct intracranial injury as a confounding factor. CT may also reveal cerebral edema which, while not specific for fat embolism syndrome, is supportive evidence of the diagnosis and demands appropriate treatment.
Magnetic resonance imaging may be more specific for fat embolization of the brain and often shows demyelinating lesions ( Scgpa ef a/ 1994). The prognosis for neurological recovery remains good and appears to be unrelated to the nature of the original neurological signs.
The following, while not diagnostic, may provide supportive evidence.
1. Thrombocytopenia (< 150 000/mm3), which may be accompanied by a drop in hemoglobin, may occur.
2. Coagulation derangements range from minor abnormalities to DIC.
3. Lipase may be elevated in association with fat embolism and fat embolism syndrome, but is non-specific. The same is true of lipuria and fat droplets in the sputum.
4. Electrocardiographic changes, usually of right heart strain, occur in up to 75 per cent of patients with fat embolism syndrome, but are non-specific.
5. Staining of tracheal aspirate for fat and, more recently, staining of bronchoalveolar lavage fluid for fat-laden cells are recommended, but there is lack of specificity with these techniques.
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