A case of drowning lacking typical autopsy findings of carbon monoxide poisoning despite the high CO concentration

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Carbon monoxide (CO) is the leading cause of poisoning death in Japan [1, 2]. In a forensic autopsy, the measurement of blood carboxyhemoglobin (CO-Hb) is important to determine the cause of death of victims of fire, suicide, and/ or accident. Moreover, CO-Hb measurement is important in the examination of victims of large-scale disasters, such as forest fires [3]. We present here one case in which a routine CO analysis was helpful in determining the circumstances related to the cause of death. The victim was found in a bathtub with no characteristic findings of CO poisoning. The detection of a high level of CO-Hb at autopsy led to a reinvestigation by the police and prevented a secondary incident in which a member of the victim’s family could have succumbed to CO poisoning. A woman aged in her fifties (156 cm tall and 45.9 kg body weight) was found dead in a bathroom of her home. The victim was sitting in the bathtub with her face under water. Her family called an ambulance, but postmortem rigidity was observed by the emergency personnel upon arrival. The victim was a smoker but not a drinker and did not have any past history of disease. About 12 h after the woman’s death, an autopsy was performed. Although no signs of external trauma were present, the sclera and palpebral conjunctivae showed some petechiae. Any findings suggesting putrefaction were not recognized. Magenta lividity was noted on the victim’s back but faded under finger pressure. The internal examinations revealed that the heart weighed 414 g and was slightly hypertrophic, containing 150 ml of dark-red blood without coagulum. Marked atherosclerosis in the aorta and coronary arteries was observed. Aspirated liquid was in the upper airways, and the lungs were over-distended. The lungs were congested and edematous; the right and left lungs weighed 550 and 420 g, respectively. The other viscera showed signs of flaccid congestion. Histologically, acute lung emphysema with lacerations of the septa, capillary congestion, and moderate intraalveolar edema were observed. Based on circumstantial details, autopsy, histology, and toxicological findings, drowning was considered the most probable cause of death. A drug screening test using a Triage DOA plus TCA (Biosite Diagnostic, San Diego, CA, USA) panel was negative. Postmortem blood samples were collected for subsequent investigation. CO-Hb was measured using the AVOXimeter 4000 (AVOX; International Technidyne, NJ, USA) [4], which yields results within 10 s. The CO-Hb level, as measured using AVOX, was 57.2 % in the right cardiac blood and 55.9 % in the left cardiac blood. CO-Hb was also measured by the conventional double-wavelength (or spectrophotometric) method [5]. It was 55.7 % in the right and left cardiac blood. Quantitation of ethanol was performed using headspace gas chromatography, according to our previous method [6], with slight modifications. No blood ethanol was detected. A reinvestigation of the scene was conducted about 1 week after the victim’s autopsy. The victim had been J. Fujihara H. Takeshita (&) Department of Legal Medicine, Shimane University School of Medicine, Izumo 693-8501, Japan e-mail: htakeshi@med.shimane-u.ac.jp