凍死の診断における血中尿素窒素およびクレアチニン測定の有用性

Abstract

Diagnosis of fatal hypothermia using biochemical markers from blood obtained post mortem has not been fully studied. The objective of this study was to investigate biochemical markers useful for diagnosis of fatal hypothermia. We investigated 573 cases that were autopsied within 72 hours of death in our laboratory between January 2015 and February 2018. Right cardiac blood, left cardiac blood and the femoral vein were used as blood sampling sites. Levels of troponin T, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen (BUN), creatinine (Cr), creatine kinase (CK), and CK-MB in the blood, and blood and urinary myoglobin (Mb) were measured. Mb staining of kidney specimens was also performed. Although BUN and Cr levels did not differ from their respective clinical reference values, very high levels of the other markers compared with their respective reference values were observed. BUN and Cr values did not differ among the right cardiac, left cardiac, and femoral vein blood. The BUN value of right cardiac blood in patients who died due to fatal hypothermia was significantly higher than that in patients who died due to burns, heart disease, suffocation, hemorrhagic shock, drowning, and trauma; however, the Cr value for fatal hypothermia was not different from that for other causes of death. Also, the BUN/Cr ratio was significantly higher for fatal hypothermia than for other causes of death. The positive rates of Mb staining in the kidney were as follows: fatal hypothermia, 75%; drowning, 56.7%; drug addiction, 53.3%; trauma, 51.4%; burning death, 47.4%; heart disease, 34.8%; and suffocation, 23.1%. In addition, the amount of urine in the urinary bladder was higher in cases of fatal hypothermia than that in cases of other causes of death. These results suggest that a high BUN value and high BUN/Cr ratio are useful for diagnosis of fatal hypothermia; the increase in BUN value may not be due to acute renal failure caused by rhabdomyolysis but may be due to a decrease in renal blood flow caused by extrarenal factors such as dehydration or circulatory failure.