Fire Victim Blood Cyanide Stability and the Development of a Cyanide Uptake Model

Abstract

In fire death cases, toxicological data from the victim(s) can provide the fire investigator with important scientific evidence to make a conclusive determination of the origin and cause of the fire. The overall goal of this research was to expand the "investigator's toolbox" by enhancing techniques available for the analysis of blood cyanide levels in fire victims. The first objective was to determine what factors cause cyanide to become unstable post-mortem. Based on a literature review, it was found that rate of transformation of cyanide in blood and tissue specimens is dependent on four criteria: initial sample concentration at time of death, length of time that sample remains in the cadaver after death, length of time that sample remains in storage before analysis, and sample preservation and storage temperature. Average decreases of sample cyanide concentrations within typical time periods of autopsy and toxicological analysis showed an approximate maximum decrease of 60% in blood. The second objective was to establish a method to reduce the instability in post-mortem samples containing cyanide. Sodium fluoride was added to samples from fire victims to evaluate its stabilizing abilities. Testing showed a statistically significant difference between blood cyanide concentrations in treated and control samples observed between 25-30 days. Based on the findings of this study, it is recommended that 2% sodium fluoride be added to blood samples from fire victims to reduce potential instability due to bacteriological activity. The final objective was to develop a basic relationship between cyanide blood concentration and exposure dose. Rats were exposed until death to hydrogen cyanide ranging in concentration from 200 ppm to 1000 ppm. Blood cyanide concentrations ranged from 0.88 mg/L to 3.98 mg/L immediately after death and times of death ranged from 6 minutes to 83 minutes. A physiologically-based, mathematical model was developed based on the collected, respiratory data. This model provides a relationship between blood cyanide concentration, hydrogen cyanide exposure concentration, respiratory minute volume, animal mass, clearing time, fraction of cyanide in the blood, and time of death.