Clinical History:

A 27-year-old man was driving a truck & trailer rig northbound on I- 15 when he lost control of the vehicle, leaving the roadway. He rolled into an embankment, overturning the vehicle. Police and paramedics arrived on the scene soon after and extricated him from the cab. He was transported to UUMC. Upon arrival, he was hypotensive and incoherent. Blood alcohol was 0.27 G/dl. He had fractures of the right humerus, right upper femur and lower left tibia. Peritoneal lavage revealed no evidence for abdominal hemorrhage. His condition was stabilized and he did well for 3 days, but then he became increasingly short of breath and died despite intubation and ventilatory support.

Image 1.1:

This H&E stained section is representative of all lung fields. Note the clear vacuoles in the small arteries. The vacuoles are left when the lipid has been removed in tissue processing.

Image 1.2:

This is an oil red O stain of the lung. The vacuoles seen on H&E now stain as red globules.

A frozen section was done, so the tissue did not go through routine processing. Thus, the oil red O stains the lipid in the vacuoles in the pulmonary vasculature.

Image 1.3:

This is an H&E stained section of a glomerulus. Note the clear vacuoles similar to those in the lung. The fat globules have been trapped in the glomerular capillaries.

Image 1.4:

The gross appearance of the brain is shown here. Note the petechial hemorrhages most prominent in white matter (so-called "brain purpura")

Questions:

1. What is the diagnosis?

   This is fat embolism syndrome.

2. What is the pathogenesis?

In this case, the trauma of fractures of long bones (which contain mostly fatty marrow) released fat globules into the circulation. These globules were trapped in the pulmonary vasculature.

3. What other conditions can produce this syndrome?

Fat embolism may also be seen with severe burn injuries and with extensive trauma to adipose tissue and to a fatty liver.

4. What is the legal limit for blood ethanol while driving?

0.08 gm%