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

INTRODUCTION 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 μ [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]. OBJECTIVES The aim of our work was to determine whether the age of injured, their gender, total severity of trauma, outliving period, and hypovole-mic shock that develops after injuring, may induce development of more severe forms of post-traumatic lung fat embolism. MATERIAL AND METHODS A prospective histological study was performed on the autopsy material of the Institute of Forensic Medicine in Belgrade. The analyzed sample consisted of individuals with injuries that might be a source of fat emboli (fractures of long bones, large contusions of subcutaneous fat tissue). The lung slices were systematically taken and stained with special fat staining (Sudan III). In each particular case, the grade of lung fat embolism was counted on the basis of microscopical appearance, according to Sevitt's criteria. The total severity of trauma was estimated by calculation of the Injury Severity Score (ISS) [13,14]. In no cases from the analyzed sample, the fat embolism was mentioned as either singular or plural cause of death. The obtained results were analyzed by means of ap