Carbon monoxide (CO) and hydrogen cyanide (HCN) are two of the main gases causing injury and death from smoke inhalation in fire victims. During the first phase of a fire, and prior to depletion of oxygen reserves and subsequent production of CO, formation of HCN from the thermal breakdown of nitrogen-containing materials may be the primary cause of lethal poisoning in an enclosed-space fire.
A recent, retrospective, observational study from Poland assessed the prevalence of toxic HCN exposure in victims of enclosed-space fires.
Important findings:
Of the 285 patients who died, 169 (59%) had detectable cyanide blood levels. 82% also had elevated carboxyhemoglobin (COHb) levels.
Of the 40 patients who survived, 20 (50%) had detectable cyanide blood levels. All 20 had elevated COHb levels.
Conclusion: The high prevalence of coincident HCN concentrations and COHb levels in victims of enclosed-space fires emphasises the need to suspect HCN as a co-toxin in all persons rescued from fire who show signs and symptoms of respiratory distress.
References
Grabowska T, et al. Prevalence of hydrogen cyanide and carboxyhaemoglobin in victims of smoke inhalation during enclosed-space fires: a combined toxicological risk. Clin Toxicol 2012;50:759-63.
