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Cyanide poisoning is rare but highly lethal. Cyanide exposure can occur during residential fire (most common source of exposure) where combustion of synthetic materials (i.e. plastic and polyurethane) releases cyanide gas as well as other toxic gases, including carbon monoxide. Although carbon monoxide poisoning can be readily identified by CO-Hb level using CO-oximetry, serum/blood cyanide level is not readily available for acute management.
However, elevated lactate level (> 10 mmol/L ) has shown to be highly correlated with toxic level of cyanide (40 micromol/L or 1 mg/L) in smoke inhalation victims (Baude FJ et al. N Engl J Med 1991;325:1761-6).
- Sensitivity: 87%
- Specificity: 94%
- Positive predictive value: 95%
Bottom line: when managing smoke inhalation victims, think about cyanide poisoning in addition to carbon monoxide poisoning and check the lactate level. Lactate > 10 mmol/L is suggestive of cyanide poisoning and should be treated with hydroxocobalamin.
References
Baude FJ et al. Elevated blood cyanide concentrations in victims of smoke inhalation N Engl J Med 1991;325:1761-6