Empiric Management of Cyanide Toxicity Associated with Smoke Inhalation

Abstract

Enclosed-space smoke inhalation is the fifth most common cause of all unintentional injury deaths in the United States. Increasingly, cyanide has been recognized as a significant toxicant in many cases of smoke inhalation. However, it cannot be emergently verified. Failure to recognize the possibility of cyanide toxicity may result in inadequate treatment. Findings suggestive cyanide toxicity include: (1) a history of an enclosed-space fire scene in which smoke inhalation was likely; (2) the presence of oropharyngeal soot or carbonaceous expectorations; (3) any alteration of the level of consciousness, and particularly, otherwise inexplicable hypotension (systolic blood pressure ≤90 mmHg in adults). Prehospital studies have demonstrated the feasibility and safety of empiric treatment with hydroxocobalamin for patients with suspected smoke inhalation cyanide toxicity. Although United States Food and Drug Administration (FDA)-approved since 2006, the lack of efficacy data has stymied the routine use of this potentially lifesaving antidote. Based on a literature review and on-site observation of the Paris Fire Brigade, emergency management protocols to guide empiric and early hydroxocobalamin administration in smoke inhalation victims with high-risk presentations are proposed.

Case Files of the University of Massachusetts Toxicology Fellowship: Does This Smoke Inhalation Victim Require Treatment with Cyanide Antidote?

“…In 2011, O'Brien et al published an excellent review of cyanide toxicity, with a proposed algorithm on the empiric management of cyanide toxicity in the pre-hospital setting [10]. In their work, they divided patients into four categories: mild, moderate, and severe smoke inhalation, and cardiac arrest.…”

Smoke inhalation injury during enclosed-space fires: an update

“…Therefore, profound lactic acidosis occurs, death occurring within minutes after exposure to large doses. ( 3 , 4 , 40 ) …”

“…( 3 ) Therefore, a blood sample should be obtained as early as possible, even while still at the scene of the accident, and treatment should be initiated before laboratory test results are known, the results being released within 2 h, on average. …”

“…( 3 , 4 ) A small case series of patients with HCN poisoning unrelated to smoke inhalation showed that serum lactate levels above 8 mmol/L have a sensitivity of 94%, a specificity of 74%, a positive predictive value of 98%, and a negative predictive value of 98% for predicting serum HCN levels > 1 mg/L. ( 41 ) A reduced arterial-venous O 2 difference is also observed, being generally lower than 10 mmHg, which explains the absence of cyanosis.…”

“…During a fire, the concentration of oxygen (O 2 ) typically drops to 10-15%, at which point death from asphyxia occurs. ( 2 , 3 ) Between 60% and 80% of all sudden deaths occurring at the scene of a fire are attributed to smoke inhalation. ( 4 ) The classic scenario is an enclosed-space fire, with loss of consciousness in the presence of facial burns or large TBSA burns.…”