Prevalence of hydrogen cyanide and carboxyhaemoglobin in victims of smoke inhalation during enclosed-space fires: a combined toxicological risk

Background. Hydrogen cyanide (HCN) is one of the most toxic components of fire smoke, but insufficient attention is paid to its potential role as a cause of injury or death in victims (alive or dead) of enclosed-space fires. Objective. To analyse the prevalence of toxic HCN exposure in fire victims and factors that may influence its toxicity, particularly the co-presence of carbon monoxide (CO) and ethanol. Materials and methods. Blood samples from fire victims and persons rescued from fires were analysed. Results. A positive result for HCN (mean concentration 16.83 mg/l) was detected in blood samples from 169 of 285 fire-related deaths (59%). Ethanol was present in 91 (65%) of 139 samples with coincident presence of HCN and carboxyhaemoglobin (COHb). HCN (mean 4.0 mg/l) was also detected in 20 of 40 (50%) fire survivors. Discussion. The high prevalence of coincident CO and HCN in enclosed-space, fire-related deaths should alert clinicians to suspect toxic HCN exposure in all persons rescued from fire with signs and symptoms of respiratory distress. Conclusions. Medical procedures in persons rescued from enclosed-space fires, especially in the pre-hospital setting, should be augmented to cover the possibility of toxic HCN exposure, particularly in individuals who do not respond to standard supportive therapy. Likewise, post-mortem investigations should routinely include assays for HCN when determining probable cause of death.