Cyanide poisoning mechanism

Sodium nitrite (NaNOg) is used by emergency medical personnel as an antidote for cyanide poisoning (for this purpose, it must be administered immediately). Based on the discussion of cyanide poisoning in Section 21.10, suggest a mechanism for the life-saving effect of sodium nitrite. 

Although its mode is uncertain, sodium nitroprusside (SNP) is one of the most valuable vasodilators. Its use in clinical practice is suspect as the cyano-ligands render cyanide poisoning a possibility. However for ex vivo experiments this consideration is less important but the possibility of some biological action due to these ions remains. The mechanism by which SNP acts as a vasodilator is not fully understood. With the discovery of a physiological role for NO there has been renewed interest in mechanistic studies of reactions involving SNP and a re-examination of studies of SNP undertaken before 1987. So far, only one simple reaction leading to the release... 

Acute poisoning only occurs when the detoxification mechanism is overwhelmed. This reaction is enhanced by giving sodium thiosulfate and sodium nitrate intravenously as 20% solutions in a 3 1 ratio, which is a recommended antidote for acute cyanide poisoning. It is the thiocyanate metabolite that causes chronic disease when cyanide forage is ingested over an extended period. 

Thankfully, the body has a detoxication system for cyanide, presumably because of the presence of naturally occurring cyanides in plants. This defence mechanism, however, can be easily overwhelmed and fatalities do occur (see p. 220). If someone working with a cyanide is found frothing a little around the mouth, an unusually brighter red colour than normal, and smelling of bitter almonds (a bit like marzipan), all is not lost, however. If they are still ahve, there is hope, for there are several antidotes and treatments for cyanide poisoning. Unfortunately, not everyone can smell cyanide as there appears to be a genetic deficiency in some people which means that they cannot detect it by its smell. 

Patients who are critical and do not satisfactorily respond to supportive therapy should be administered specific cyanide antidotes as outlined in Table 19.5. Cyanide antidotes have been classified into three main groups based on their mechanism of action (1) methemoglobin inducers, (2) sulfur donors, and (3) cobalt compounds. The definitive treatment of cyanide poisoning differs in various countries due to different medical practices and guidelines. The safety... 

Beasiey DM, Giass Wi Cyanide poisoning pathophysioiogy and treatment recommendations. Occup Med (Lend) 1998 48(7) 427-431. [PMiD 10024740] (Review of the mechanism ot toxicity of cyanide and the ratiohaie for treafmehf opfiohs.)... 

A 92-year-old African-American woman suffered from smoke inhalation during a house fire. The patient was transferred from a cross-town hospital to receive hyperbaric oxygen (HBO) therapy for carbon monoxide intoxication. Before arrival she was sedated, intubated, and administered with 5g hydroxocobalamin intravenously for suspected cyanide poisoning. In the emergency department (ED) a Foley s catheter was placed and, upon inspection, her urine was tinted a deep red colour. She received prompt HBO treatment and was transferred to the intensive care unit (ICU). Despite mechanical ventilation, HBO therapy and treatment for cyanide toxicity, the patient suffered cardiopulmonary arrest while in the ICU and died days later. 

Poison Treatment As discussed previously, methemoglobin binds well and competes with cytochrome oxidase for cyanide ions. Consequently, the antidote developed for cyanide poisoning involves increasing the formation of methemoglobin in the blood, by inhalation of amyl nitrate vapor (Chen 1952). Antidote kits contain amyl nitrate ampoules. To administer the antidote, the ampoule is broken in a cloth such as a handkerchief and held close to the victim s nose while artificial respiration is being conducted. Resuscitation by mouth is not recommended a mechanical resuscitator should be used instead. If the victim does not respond to the amyl nitrate treatment, a medical professional would then increase the methemoglobin production by intravenous injection of sodium nitrate followed by administration of thiosulfate to increase the activity of the rhodanese enzyme. 

There are a number of grim anecdotes about him in wartime thus, at that time he always carried a cyanide capsule for the eventuality of his capture, and when a fellow professor asked him to find him one too, he responded This poison is for professors of chemistry only. You, as a professor of mechanics, will have to use the rope . 

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