Hydrogen cyanide poisoning proves increasingly common in smoke-inhalation victims

By RICHARD ALCORTA, MD, FACEP

Emergency medical and fire-rescue professionals tend to equate cyanide poisoning with accidental or intentional ingestion. However, cyanide toxicity from smoke inhalation in a structural or an enclosed-space fire is the most likely cause of cyanide toxicity that EMS and fire professionals will encounter.

Hydrogen cyanide, the gaseous form of cyanide, is generated by the combustion of nitrogen- and carbon-containing substances, including wool, silk, cotton and paper, as well as synthetic substances, such as plastics and other polymers. Because of our extensive reliance on the polymer industry’s nitrogen- and carbon-containing products, these hydrogen cyanide substrates are ubiquitous in occupied structures. Hydrogen cyanide is likely to be produced under burning conditions of high temperature and low oxygen, both of which are characteristic of closed-space fires. An enclosed space serves as a container for the toxic gases in smoke, such as hydrogen cyanide.

Smoke inhalation-associated cyanide poisoning manifestations vary. In victims with low inhaled-cyanide concentrations or very recent exposure to moderate or high concentrations, manifestations may include faintness, flushing, anxiety, excitement, perspiration, vertigo, headache, drowsiness, tachypnea, dyspnea and tachycardia.

In victims with moderate or high concentrations, manifestations may include prostration, tremors, cardiac arrhythmia, convulsions, stupor, paralysis, coma, respiratory depression, respiratory arrest and cardiovascular collapse.

Firefighters and victims with smoke inhalation-associated cyanide poisoning often experience cognitive dysfunction and drowsiness that can impair the fight-or-flight response.

Treatment for hydrogen cyanide poisoning must be administered as quickly as possible after exposure. Therefore, presumptive diagnosis and empiric treatment prove necessary to save lives.

Prehospital management of acute cyanide poisoning in the smoke inhalation victim involves moving the victim from the source of exposure (while maintaining appropriate provider respiratory protection, SCBA), restoring or maintaining airway patency, administering 100% oxygen via non-rebreather mask or bag-valve mask technique, aggressive advanced airway management, including early intubation, providing cardiopulmonary support and stabilizing vital signs, including the use of trauma and burn management (Parkland formula). When clinically indicated, anticonvulsants (benzodiazpines) should be given for seizures, epinephrine and antiarrhythmics to stabilize cardiovascular function, and sodium bicarbonate to correct metabolic acidosis if known. Effective cyanide antidotes exist. However, a cyanide antidote appropriate for use in smoke-inhalation victims is not yet available in the United States.

Hydroxocobalamin, a precursor of vitamin B12, is being investigated for possible introduction in the United States to meet the need for an antidote that can be used safely on an empiric basis.

For now, the best course of prehospital intervention is the provision of rapid transport to a hospital ED or burn center where definitive treatment can be delivered.

Excerpted from Smoke Inhalation & Hydrogen Cyanide Poisoning, an editorial supplement to EMS1, Summer 2004. To download a PDF of the complete supplement, visit http://www.ems1.com/data/pdf/smoke-poisoning.pdf.