Thursday, July 10, 2008
Best Post of February, 2008: The mechanism of post-traumatic cerebral fat emboli not well understood
The next in my occasional “Best Post Of The Month” series is for February, 2008:
I was giving a lecture on the pathology of cerebrovascular disease today, and showed a picture from Robbins of a brain with a shower of fat emboli after fracture of long bones. A student asked what the mechanism would be, pointing out that it would be difficult for marrow fat to get from the venous system of the leg into the arterial circulation of the brain without going through the filter of the pulmonary capillary bed.
The etiology of fat emboli after trauma is not clear. According to an article by Butteriss et al. in the American Journal of Neuroradiology, microemboli may pass into the systemic circulation either via cardiac or intrapulmonary right-left shunts or directly through the pulmonary capillary bed. Apparently a study of orthopedic surgery in dogs has shown that fat globules of <5 µm can traverse the pulmonary micovasculature. One could imagine these globules coalescing in the brain and causing significant infarcts, I suppose.
Whatever the mechanism, I imagine air emboli introduced when inserting or pulling out a central line might form in a similar manner.
(Source: D.J.A. Butteriss et al., Reversible Cytotoxic Cerebral Edema in Cerebral Fat Embolism . American Journal of Neuroradiology 27:620-623, March 2006.)