Estimation of postmortem interval from human pericardial fluid electrolytes concentrations in Chandigarh zone of India: Log transformed linear regression model

Estimation of postmortem interval from changes in postmortem pericardial fluid electrolytes concentration is the topic of discussion in the study. Querido [Querido D. Double logarithmic, linear relationship between plasma sodium/potassium concentration ratio and postmortem interval during the 6–96 h postmortem period in rats. Forensic Sci Int 1990;44:125–34; Querido D. Linearization of the relationship between postmortem plasma chloride concentration and postmortem interval in rats. Forensic Sci Int 1990;45:117–27] and Singh et al. [Singh D, Prashad R, Parkash C, Bansal YS, Sharma SK, Pandey AN. Linearization of relationship between serum sodium, potassium concentration, their ratio and time since deaths in Chandigarh zone of north west India. Forensic Sci Int 2002;130:107; Singh D, Prashad R, Parkash C, Sharma SK, Pandey AN. Double logarithmic linear relationship between plasma chloride concentration and time since death in humans in Chandigarh zone of north west India. Legal Med 2003;5:49–54] had demonstrated a highly significant double logarithmic linear relationship between the time since death and the plasma sodium/potassium ratio as well as with plasma chloride concentration in Wistar rats and human, respectively. In view of these facts, the present study was carried out to substantiate this propensity in this transcellular extension of blood plasma. Electrolytes analysis in postmortem pericardial fluid obtained from 311 subjects revealed that correlation of time since deaths with potassium, sodium/potassium ratio and phosphorus was highly significant (p < 0.001) during 2.5–58 h of deaths. Not withstanding, time since death although modulated by ambient temperature could be predicted by log transformed multiple regression equation derived from the combination of potassium, chloride and phosphorus electrolytes concentration with standard error (SE) of prediction (in log hours) of 0.1840 h and by double logarithmic model with SE (in log hours) of 0.1959, 0.2068 and 0.2088 h from potassium, sodium/potassium ratio and phosphorus electrolytes, respectively.