The concern of a terrorist attack using
cyanide, as well as the gradual awareness of
cyanide poisoning in fire victims, has resulted in a renewed interest in the diagnosis and treatment of
cyanide poisoning. The formerly academic presentation of
cyanide poisoning must be replaced by more useful knowledge, which will allow emergency physicians and rescue workers to strongly suspect
cyanide poisoning at the scene. Human
cyanide poisonings may result from exposure to
cyanide, its
salts, or cyanogenic compounds, while residential fires are the most common condition of exposure. In fire victims, recognition of the
cyanide toxidrome has been hampered by the short half-life in blood and poor stability of
cyanide. In contrast,
carboxyhemoglobin, as a marker of
carbon monoxide poisoning, is easily measured and long-lasting. No evidence supports the assumption of the arbitrary fixed lethal thresholds of 50% for
carboxyhemoglobin, and 3 mg/L for
cyanide, in fire victims. Preliminary data, drawn when comparing pure
carbon monoxide and pure
cyanide poisonings, suggest that a
cyanide toxidrome can be defined considering signs and symptoms induced by
cyanide and
carbon monoxide, respectively. Prospective studies in fire victims may provide value in clarifying signs and symptoms related to both toxicants.
Cyanide can induce a life-threatening
poisoning from which a full recovery is possible. A number of experimentally efficient antidotes to
cyanide exist, whose clinical use has been hampered due to serious side effects. The availability of potentially safer antidotes unveils the possibility of their value as first-line treatment, even in a complex clinical situation, where diagnosis is rapid and presumptive.