Postmortem pulmonary CT in hypothermia
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ORIGINAL PAPER
Postmortem pulmonary CT in hypothermia Wolf Schweitzer • Michael Thali • Giannina Giugni Sebastian Winklhofer
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Accepted: 4 September 2014 / Published online: 19 October 2014 Springer Science+Business Media New York 2014
Abstract Fatal hypothermia has been associated with pulmonary edema. With postmortem full body computed tomography scanning (PMCT), the lungs can also be examined for CT attenuation. In fatal hypothermia cases low CT attenuation appeared to prevail in the lungs. We compared 14 cases of fatal hypothermia with an age-sex matched control group. Additionally, 4 cases of carbon monoxide (CO) poisoning were examined. Furthermore, 10 test cases were examined to test predictability based on PMCT. Two readers measured CT attenuation on four different axial slices across the lungs (blinded to case group and other reader’s results). Hypothermia was associated with statistically significantly lower lung PMCT attenuation and lower lung weights than controls, and there was a dose–effect relationship at an environmental temperature cutoff of 2 C. CO poisoning yielded low pulmonary attenuation but higher lung weights. General model based prediction yielded a 94 % probability for fatal hypothermia deaths and a 21 % probability for non-hypothermia deaths in the test group. Increased breathing rate is known to accompany both CO poisoning and hypothermia, so this could partly explain the low PMCT lung attenuation due to an oxygen dissociation curve left shift. A more marked distension in fatal hypothermia, compared to CO poisoning, indicates that further, possibly different mechanisms, are involved in these cases. Increased dead space and W. Schweitzer (&) M. Thali G. Giugni Institute of Forensic Medicine, University of Zu¨rich, Winterthurerstr. 190, 8057 Zurich, Switzerland e-mail: [email protected] S. Winklhofer Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Raemistrasse 100, 8091 Zurich, Switzerland
increased stiffness to deflation (but not inflation) appear to be effects of inhaling cold air (but not CO) that may explain the difference in low PMCT attenuation seen in hypothermia cases. Keywords Computed tomography Hypothermia Postmortem Pulmonary emphysema
Introduction The diagnosis of fatal hypothermia is based on a number of hypothermia-associated observations as well as on exclusion [1, 2]. On external inspection, the bright red discoloration of livor mortis, red to purple, or pink to brownishpink discoloration over the skin of extensor surfaces such as around the elbows or knees, as well as circumstantial indicators such as low environmental temperature or paradoxical undressing may indicate fatal hypothermia. At autopsy, bright red blood, Wischnewski erosions of the gastric mucosa [3], hemorrhage in the psoas muscle and acute pancreatic necrosis are typical [4, 5] but not specific [6] findings. Chemical test results that support the assumption of a prolonged agonal phase in fatal hypothermia include ketonuria [7]. Postmortem full body compu
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