Potential for error when assessing blood cyanide concentrations in fire victims

Area of Science:

• Forensic Toxicology
• Environmental Health
• Chemical Pathology

Background:

• Blood cyanide concentrations are crucial for assessing toxicity in fire victims.
• High carboxyhemoglobin (COHb) saturation is common in fire fatalities.
• The influence of methemoglobinemia and postmortem interval on blood cyanide levels requires investigation.

Purpose of the Study:

• To investigate the toxicologic significance of blood cyanide concentrations in fire victims.
• To evaluate the impact of methemoglobinemia and postmortem interval on cyanide levels.
• To determine the stability of blood cyanide over time under varying conditions.

Main Methods:

• Analysis of blood samples from human fire victims using headspace gas chromatography.
• An animal model (rabbits) was used to study the effects of induced methemoglobinemia on cyanide levels.
• Blood cyanide stability was assessed under different postmortem storage temperatures and durations.

Main Results:

• Human fire victims showed a wide range of blood cyanide concentrations (0-11.9 mg/L) and COHb saturation (24.9-84.2%).
• Rabbits with induced methemoglobinemia had significantly higher initial blood cyanide concentrations (47.4 mg/L) compared to controls (3.56 mg/L).
• Blood cyanide levels decreased significantly over time, with rapid degradation observed at higher temperatures, showing ~85% and ~46% reduction within 24h in methemoglobinemic and control groups, respectively.

Conclusions:

• Blood cyanide concentrations in fire victims are highly variable and decrease substantially postmortem.
• Methemoglobinemia influences initial cyanide levels, but its effect diminishes with postmortem degradation.
• Evaluating cyanide toxicity in fire victims solely based on postmortem blood concentrations is unreliable due to rapid degradation and variability.