Chemical asphyxiants other than carbon monoxide: hydrogen sulfide and cyanide. Hydrogen sulfide: the knockdown effect, cytochrome oxidase inhibition, carotid body stimulation and respiratory arrest, nitrite treatment, and long-term neurologic sequelae. Cyanide: cellular mechanism of toxicity, lactic acidosis and elevated venous oxygen saturation, retinal arterialization, antidotes (hydroxocobalamin, sodium thiosulfate, nitrites), fire-gas exposure, and the bitter almond odor.
Because direct blood cyanide levels are rarely available in time to guide the emergency management of a poisoned worker, which laboratory biomarker is used to assess the severity of the exposure?