Differentiating Primary and Secondary Hypothermia in a Rat Model: The Role of Biochemical Markers in Postmortem Analysis

Postmortem biochemistry is a valuable tool in forensic investigations, providing insights into the tissue damage and organ dysfunction associated with death. This study aimed to identify biochemical markers that distinguish primary and secondary hypothermia. Twenty-one Wistar rats were allocated into three groups: the Control group (n = 7), which was exposed only to hypothermic conditions, the Alcohol + Hypothermia group (n = 7), and the Benzodiazepines + Hypothermia group (n = 7). The temperature metrics assessed included the normal core temperature, the post-ketamine (0.3 ml injection) core temperature, the immersion temperature, temperature at the onset of hypothermia, and temperature at death. Blood samples were collected from the thoracic aorta in EDTA vacuum tubes for biochemical analysis. The key biochemical parameters measured included the Total Protein (g/L), Albumin (g/L), Globulin (g/L), Albumin to Globulin Ratio, Alanine Aminotransferase (U/L), Alkaline Phosphatase (U/L), Cholesterol (mmol/L), Amylase (U/L), and Lipase (U/L), using an automated IDEXX (Netherlands) cell counter. Significant between-group differences were found for the total protein and globulin levels (p < 0.001 and p = 0.002, respectively), with post-hoc tests confirming differences between the alcohol and control, and benzodiazepine and control groups. The cholesterol levels were found to be significantly different through an omnibus test (p = 0.03), but post hoc tests did not confirm these differences on a statistically significant level. The amylase levels varied significantly across all groups (p < 0.001), with post hoc tests confirming significant differences among all pairs: alcohol vs. benzodiazepine (p = 0.002), alcohol vs. control (p = 0.003), and benzodiazepine vs. control (p < 0.001). The lipase levels showed significant differences in the omnibus test (p = 0.030), but there was no significance in the post hoc tests. Amylase emerged as the most significant parameter in our study, with reduced levels strongly associated with secondary hypothermia. These findings highlight the potential use of total protein, globulin, and amylase levels as biomarkers to differentiate between primary and secondary hypothermia in forensic contexts.