An emergency involving the diagnosis and management of patients exposed to cyanide is a potential scenario for any healthcare facility. Cyanide exposure is associated with smoke inhalation, laboratory mishaps, industrial incidents, suicide attempts, and criminal activity. Cyanide is a chemical group that consists of one atom of carbon bound to one atom of nitrogen by three molecular bonds (C≡N). Inorganic cyanides (also know as cyanide salts) contain cyanide in the anion form (CN−) and are used in numerous industries, such as metallurgy, photographic developing, plastic manufacturing, fumigation, and mining. Common cyanide salts include sodium cyanide (NaCN) and potassium cyanide (KCN). Sodium salts react readily with water to form hydrogen cyanide. Organic compounds that have a cyano group bonded to an alkyl residue are called nitriles. For example, methyl cyanide is also known as acetonitrile (CH3CN). Hydrogen cyanide (HCN) is a colorless gas at standard temperature and pressure with a reported bitter odor. Cyanogen gas, a dimer of cyanide, reacts with water and breaks down into the cyanide anion.
Many plants, such as Manihot spp, Linum spp, Lotus spp, Prunus spp, Sorghum spp, and Phaseolus spp, contain cyanogenic glycosides.112 The Prunus species consisting of apricots, bitter almond, cherry, and peaches have pitted fruits containing the glucoside amygdalin. When ingested, amygdalin is biotransformed by intestinal β-d-glucosidase to glucose, aldehyde, and cyanide (Fig. 126–1). Laetrile, which contains amygdalin, has been inappropriately suggested to have antineoplastic properties. When laetrile is administered by intravenous (IV) infusion, amygdalin bypasses the necessary enzymes in the gastrointestinal (GI) tract to liberate cyanide and does not cause toxicity. However, when ingested, laetrile may cause cyanide poisoning.48 Despite data demonstrating its lack of utility in the treatment of cancer, laetrile is still available via the Internet.
Biotransformation of cyanogens (A) acetonitrile and (B) amygdalin to cyanide.
Cassava (Manihot esculenta) root is a major source of food for millions of people in the tropics. It is a hardy plant that can remain in the ground for up to 2 years and needs relatively little water to survive. Because the shelf life of a cassava root is very short after it is removed from the stem, cassava root must be processed and sent to market as soon as it is harvested. However, proper processing must occur to ensure the food's safety. Processed cassava is called Gari. Linamarin (2-hydroxyixo-buty-nitrite-β-D-glycoside) is the major cyanogenic glycoside in cassava roots. It is hydrolyzed to hydrogen cyanide and acetone in two steps during the processing of cassava roots.126 Whereas soaking peeled cassava in water for a single day releases approximately 45% of the cyanogens, soaking for 5 days causes 90% loss. If processing is inefficient, linamarin and cyanohydrin, the ...