Factors that could influence the severity of post-traumatic lung fat embolism - a prospective histological study -

Each fracture of long or pelvic bones as well as large contusions of subcutaneous fat tissue cause releasing of fat globules that rapidly penetrate into circulation through the ruptured veins of the injured tissue, and reach the lung circulation [1,2]. During the first phase, fat emboli block the functional lung circulation by their mechanical effect in capillaries producing so called isolated post-traumatic lung fat embolism [3]. The surface layer of a fat embolus, which is practically in liquid state, behaves as a membrane of very high density, i.e., as it is under high pressure which obstruct the blood stream [4] that is finally stopped at the level of lung blood vessels with diameter of approximately 20 mu [5]. This pathophysiological mechanism produces cor pulmonale acutum, with poor pathological findings [8]. Nowadays, the post-mortem diagnosis of lung fat embolism is based on microscopical examination of tissue specimens, usually prepared with special histological staining (Sudan III) [9]. The grading of fat embolism according to Sevitt's criteria is generally accepted [10]. Taking of slices from apicoventral areas of the lungs has been recommended [11]. With longer outliving period, the total number of fat emboli in the lung circulation gradually decreases, due to their disintegration and resorption. It has been stated that fat globules completely disappear about 4-6 weeks after injury, and that they should not be searched for microscopically in this post-traumatic phase [11].