Cyanide poison | |
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Other names | Cyanide toxicity, hydrocyanic acid poison [1] |
Cyanide ion | |
Specialty | Toxicology, critical care medicine |
Symptoms | Early: headache, dizziness, fast heart rate, shortness of breath, vomiting [2] Later: seizures, slow heart rate, low blood pressure, loss of consciousness, cardiac arrest [2] |
Usual onset | Few minutes [2] [3] |
Causes | Cyanide compounds [4] |
Risk factors | House fire, metal polishing, certain insecticides, eating seeds such as from almonds [2] [3] [5] |
Diagnostic method | Based on symptoms, high blood lactate [2] |
Treatment | Decontamination, supportive care (100% oxygen), hydroxocobalamin [2] [3] [6] |
Cyanide poisoning is poisoning that results from exposure to any of a number of forms of cyanide. [4] Early symptoms include headache, dizziness, fast heart rate, shortness of breath, and vomiting. [2] This phase may then be followed by seizures, slow heart rate, low blood pressure, loss of consciousness, and cardiac arrest. [2] Onset of symptoms usually occurs within a few minutes. [2] [3] Some survivors have long-term neurological problems. [2]
Toxic cyanide-containing compounds include hydrogen cyanide gas and a number of cyanide salts. [2] Poisoning is relatively common following breathing in smoke from a house fire. [2] Other potential routes of exposure include workplaces involved in metal polishing, certain insecticides, the medication sodium nitroprusside, and certain seeds such as those of apples and apricots. [3] [7] [8] Liquid forms of cyanide can be absorbed through the skin. [9] Cyanide ions interfere with cellular respiration, resulting in the body's tissues being unable to use oxygen. [2]
Diagnosis is often difficult. [2] It may be suspected in a person following a house fire who has a decreased level of consciousness, low blood pressure, or high lactic acid. [2] Blood levels of cyanide can be measured but take time. [2] Levels of 0.5–1 mg/L are mild, 1–2 mg/L are moderate, 2–3 mg/L are severe, and greater than 3 mg/L generally result in death. [2]
If exposure is suspected, the person should be removed from the source of the exposure and decontaminated. [3] Treatment involves supportive care and giving the person 100% oxygen. [2] [3] Hydroxocobalamin (vitamin B12a) appears to be useful as an antidote and is generally first-line. [2] [6] Sodium thiosulphate may also be given. [2] Historically, cyanide has been used for mass suicide and it was used for genocide by the Nazis. [3] [10]
If hydrogen cyanide is inhaled, it can cause a coma with seizures, apnea, and cardiac arrest, with death following in a matter of seconds. At lower doses, loss of consciousness may be preceded by general weakness, dizziness, headaches, vertigo, confusion, and perceived difficulty in breathing. At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the person progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest. A cherry red skin color that darkens may be present as the result of increased venous hemoglobin oxygen saturation. Despite the similar name, cyanide does not directly cause cyanosis. [11] A fatal dose for humans can be as low as 1.5 mg/kg body weight. [12] Other sources claim a lethal dose is 1–3 mg per kg body weight for vertebrates. [13]
Exposure to lower levels of cyanide over a long period (e.g., after use of improperly processed cassava roots; cassava is a staple food in various parts of West Africa) results in increased blood cyanide levels, which can result in weakness and a variety of symptoms, including permanent paralysis, nervous lesions, [14] [15] [16] hypothyroidism, [15] and miscarriages. [17] [18] Other effects include mild liver and kidney damage. [19] [20]
Cyanide poisoning can result from the ingestion of cyanide salts, imbibing pure liquid prussic acid, skin absorption of prussic acid, intravenous infusion of nitroprusside for hypertensive crisis, [8] or the inhalation of hydrogen cyanide gas. The last typically occurs through one of three mechanisms:
As potential contributing factors, cyanide is present in:
As a potential harm-reduction factor, Vitamin B12, in the form of hydroxocobalamin (also spelled hydroxycobalamin), might reduce the negative effects of chronic exposure; whereas, a deficiency might worsen negative health effects following exposure to cyanide. [24]
Cyanide is a potent cytochrome c oxidase (COX, a.k.a. Complex IV) inhibitor, causing asphyxiation of cells. As such, cyanide poisoning is a form of histotoxic hypoxia, because it interferes with the ability of cells to take or use oxygen via oxidative phosphorylation. [25] : 1475
Specifically, cyanide binds to the heme a3-CuB binuclear center of COX [26] (and thus is a non-competitive inhibitor of it). This prevents electrons passing through COX from being transferred to O2, which not only blocks the mitochondrial electron transport chain, it also interferes with the pumping of a proton out of the mitochondrial matrix which would otherwise occur at this stage. Therefore, cyanide interferes not only with aerobic respiration but also with the ATP synthesis pathway it facilitates, owing to the close relationship between those two processes. [27] : 705
One antidote for cyanide poisoning, nitrite (i.e., via amyl nitrite), works by converting ferrohemoglobin to ferrihemoglobin, which can then compete with COX for free cyanide (as the cyanide will bind to the iron in its heme groups instead). Ferrihemoglobin cannot carry oxygen, but the amount of ferrihemoglobin that can be formed without impairing oxygen transport is much greater than the amount of COX in the body. [25] : 1475
Cyanide is a broad-spectrum poison because the reaction it inhibits is essential to aerobic metabolism; COX is found in many forms of life. [28] However, susceptibility to cyanide is far from uniform across affected species; for instance, plants have an alternative electron transfer pathway available that passes electrons directly from ubiquinone to O2, which confers cyanide resistance by bypassing COX. [27] : 704
Lactate is produced by anaerobic glycolysis when oxygen concentration becomes too low for the normal aerobic respiration pathway. Cyanide poisoning inhibits aerobic respiration and therefore increases anaerobic glycolysis which causes a rise of lactate in the plasma. A lactate concentration above 10 mmol per liter is an indicator of cyanide poisoning, as defined by the presence of a blood cyanide concentration above 40 μmol per liter. Lactate levels greater than 6 mmol/L after reported or strongly suspected pure cyanide poisoning, such as cyanide-containing smoke exposure, suggests significant cyanide exposure. [29] However, lactate alone is not diagnostic of cyanide poisoning because lactosis is also triggered by many other things, including mitochondrial dysfunction. [30]
Methods of detection include colorimetric assays such as the Prussian blue test, the pyridine-barbiturate assay, also known as the "Conway diffusion method" [31] and the taurine fluorescence-HPLC but like all colorimetric assays these are prone to false positives. Lipid peroxidation resulting in "TBARS", an artifact of heart attack produces dialdehydes that cross-react with the pyridine-barbiturate assay. Meanwhile, the taurine-fluorescence-HPLC assay used for cyanide detection is identical to the assay used to detect glutathione in spinal fluid.
Cyanide and thiocyanate assays have been run with mass spectrometry (LC/MS/MS), which are considered specific tests. Since cyanide has a short half-life, the main metabolite, thiocyanate is typically measured to determine exposure.
Decontamination of people exposed to hydrogen cyanide gas only requires removal of the outer clothing and the washing of their hair. [9] Those exposed to liquids or powders generally require full decontamination. [9]
The International Programme on Chemical Safety issued a survey (IPCS/CEC Evaluation of Antidotes Series) that lists the following antidotal agents and their effects: oxygen, sodium thiosulfate, amyl nitrite, sodium nitrite, 4-dimethylaminophenol, hydroxocobalamin, and dicobalt edetate ('Kelocyanor'), as well as several others. [32] Another commonly-recommended antidote is 'solutions A and B' (a solution of ferrous sulfate in aqueous citric acid, and aqueous sodium carbonate, respectively).
The United States standard cyanide antidote kit first uses a small inhaled dose of amyl nitrite, followed by intravenous sodium nitrite, followed by intravenous sodium thiosulfate. [33] Hydroxocobalamin was approved for use in the US in late 2006 [34] and is available in Cyanokit antidote kits. [35] Sulfanegen TEA, which could be delivered to the body through an intra-muscular (IM) injection, detoxifies cyanide and converts the cyanide into thiocyanate, a less toxic substance. [36] Alternative methods of treating cyanide intoxication are used in other countries.
The Irish Health Service Executive (HSE) has recommended against the use of solutions A and B because of their limited shelf life, potential to cause iron poisoning, and limited applicability (effective only in cases of cyanide ingestion, whereas the main modes of poisoning are inhalation and skin contact). The HSE has also questioned the usefulness of amyl nitrite due to storage/availability problems, risk of abuse, and lack of evidence of significant benefits. It also states that the availability of kelocyanor at the workplace may mislead doctors into treating a patient for cyanide poisoning when this is an erroneous diagnosis. The HSE no longer recommends a particular cyanide antidote. [37]
Agent | Description |
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Nitrites | The nitrites oxidize some of the hemoglobin's iron from the ferrous state to the ferric state, converting the hemoglobin into methemoglobin. Cyanide binds avidly to methemoglobin, forming cyanmethemoglobin, thus releasing cyanide from cytochrome oxidase. [38] Treatment with nitrites is not innocuous as methemoglobin cannot carry oxygen, and severe methemoglobinemia may need to be treated in turn with methylene blue. [note 1] |
Thiosulfate | The evidence for sodium thiosulfate's use is based on animal studies and case reports: the small quantities of cyanide present in dietary sources and in cigarette smoke are normally metabolized to relatively harmless thiocyanate by the mitochondrial enzyme rhodanese (thiosulfate cyanide sulfurtransferase), which uses thiosulfate as a substrate. However, this reaction occurs too slowly in the body for thiosulfate to be adequate by itself in acute cyanide poisoning. Thiosulfate must therefore be used in combination with nitrites. [38] |
Hydroxocobalamin | Hydroxocobalamin, a form (or vitamer) of vitamin B12 made by bacteria, and sometimes denoted vitamin B12a, is used to bind cyanide to form the harmless cyanocobalamin form of vitamin B12. |
4-Dimethylaminophenol | 4-Dimethylaminophenol (4-DMAP) has been proposed[ by whom? ] in Germany as a more rapid antidote than nitrites with (reportedly) lower toxicity. 4-DMAP is used currently by the German military and by the civilian population. In humans, intravenous injection of 3 mg/kg of 4-DMAP produces 35 percent methemoglobin levels within 1 minute. Reportedly, 4-DMAP is part of the US Cyanokit, while it is not part of the German Cyanokit due to side effects (e. g. hemolysis). |
Dicobalt edetate | Cobalt ions, being chemically similar to iron ions, can also bind cyanide. One current cobalt-based antidote available in Europe is dicobalt edetate or dicobalt-EDTA, sold as Kelocyanor. This agent chelates cyanide as the cobalticyanide. This drug provides an antidote effect more quickly than formation of methemoglobin, but a clear superiority to methemoglobin formation has not been demonstrated. Cobalt complexes are quite toxic, and there have been accidents reported in the UK where patients have been given dicobalt-EDTA by mistake based on a false diagnosis of cyanide poisoning. Because of its side effects, it should be reserved only for patients with the most severe degree of exposure to cyanide; otherwise, nitrite/thiosulfate is preferred. [41] |
Glucose | Evidence from animal experiments suggests that coadministration of glucose protects against cobalt toxicity associated with the antidote agent dicobalt edetate. For this reason, glucose is often administered alongside this agent (e.g. in the formulation 'Kelocyanor'). It has also been anecdotally suggested that glucose is itself an effective counteragent to cyanide, reacting with it to form less toxic compounds that can be eliminated by the body. One theory on the apparent immunity of Grigori Rasputin to cyanide was that his killers put the poison in sweet pastries and madeira wine, both of which are rich in sugar; thus, Rasputin would have been administered the poison together with massive quantities of antidote. One study found a reduction in cyanide toxicity in mice when the cyanide was first mixed with glucose. [42] However, as yet glucose on its own is not an officially acknowledged antidote to cyanide poisoning. |
3-Mercaptopyruvate prodrugs | The most widely studied cyanide-metabolizing pathway involves utilization of thiosulfate by the enzyme rhodanese, as stated above. In humans, however, rhodanese is concentrated in the kidneys (0.96 units/mg protein) and liver (0.15 u/mg), with concentrations in lung, brain, muscle and stomach not exceeding 0.03 U/ml. [43] In all these tissues, it is found in the mitochondrial matrix, a site of low accessibility for ionized, inorganic species, such as thiosulfate. This compartmentalization of rhodanese in mammalian tissues leaves major targets of cyanide lethality, namely, the heart and central nervous system, unprotected. Rhodanese is also found in red blood cells, but its relative importance has not been clarified. [44] [45] ) A different cyanide-metabolizing pathway, 3-mercaptopyruvate sulfurtransferase (3-MPST, EC 2.8.1.2), which is more widely distributed in mammalian tissues than rhodanese, is being explored. 3-MPST converts cyanide to thiocyanate, using the cysteine catabolite, 3-mercaptopyruvate (3-MP). However, 3-MP is extremely unstable chemically. Therefore, a prodrug, sulfanegen sodium (2,5-dihydroxy-1,4-dithiane-2,5-dicarboxylic acid disodium salt), which hydrolyzes into 2 molecules of 3-MP after being administered orally or parenterally, is being evaluated in animal models. [46] [47] |
Oxygen therapy | Oxygen therapy is not a cure in its own right. However, the human liver is capable of metabolizing cyanide quickly in low doses (smokers breathe in hydrogen cyanide, but it is such a small amount and metabolized so fast that it does not accumulate). |
The República Cromañón nightclub fire broke out in Buenos Aires, Argentina on 30 December 2004, killing 194 people and leaving at least 1,492 injured. Most of the victims died from inhaling poisonous gases, including carbon monoxide. After the fire, the technical institution INTI found that the level of toxicity due to the materials and volume of the building was 225 ppm of cyanide in the air. A lethal dose for rats is between 150 ppm and 220 ppm, meaning the air in the building was highly toxic.
On 27 January 2013, a fire at the Kiss nightclub in the city of Santa Maria, in the south of Brazil, caused the poisoning of hundreds of young people by cyanide released by the combustion of soundproofing foam made with polyurethane. By March 2013, 245 fatalities were confirmed. [48] [49] [ when? ]
Research of hydrogen cyanide by chemists Carl Wilhelm Scheele and Claude Bernard would become central to understanding the lethality of future gas chambers. [50] In early 1942, Zyklon B, which contains hydrogen cyanide, emerged as the preferred killing tool of Nazi Germany for use in extermination camps during the Holocaust. [51] The chemical was used to murder roughly one million people in gas chambers installed in extermination camps at Auschwitz-Birkenau, Majdanek, and elsewhere. [52] Most of the people who were murdered were Jews, and by far the majority of these murders took place at Auschwitz. [53] [54] [a] The constituents of Zyklon B were manufactured by several companies under licenses for Degesch, a corporation co-owned by IG Farben, Degussa and Th. Goldschmidt AG. It was sold to the German Army and the Schutzstaffel (SS) by the distributors Heli and Testa, with Heli supplying it to concentration camps at Mauthausen, Dachau, and Buchenwald and Testa to Auschwitz and Majdanek. [56] Camps also occasionally bought Zyklon B directly from the manufacturers. [57] Of the 729 tonnes of Zyklon B sold in Germany in 1942–44, 56 tonnes (about eight percent of domestic sales) were sold to concentration camps. [58] Auschwitz received 23.8 tonnes, of which six tonnes were used for fumigation. The remainder was used in the gas chambers or lost to spoilage (the product had a stated shelf life of only three months). [59] Testa conducted fumigations for the Wehrmacht and supplied them with Zyklon B. They also offered courses to the SS in the safe handling and use of the material for fumigation purposes. [60] In April 1941, the German agriculture and interior ministries designated the SS as an authorized applier of the chemical, and thus they were able to use it without any further training or governmental oversight. [61]
Hydrogen cyanide gas has been used for judicial execution in some states of the United States, where cyanide was generated by reaction between potassium cyanide (or sodium cyanide [62] [63] ) dropped into a compartment containing sulfuric acid, directly below the chair in the gas chamber. [64]
Cyanide salts are sometimes used as fast-acting suicide devices. Cyanide reacts at a higher level with high stomach acidity.
Cobinamide is the final compound in the biosynthesis of cobalamin. It has greater affinity for the cyanide than cobalamin itself, which suggests that it could be a better option for emergency treatment. [89]
Amyl nitrite is a chemical compound with the formula C5H11ONO. A variety of isomers are known, but they all feature an amyl group attached to the nitrite functional group. The alkyl group (the amyl in this case) is unreactive and the chemical and biological properties are mainly due to the nitrite group. Like other alkyl nitrites, amyl nitrite is bioactive in mammals, being a vasodilator, which is the basis of its use as a prescription medicine. As an inhalant, it also has a psychoactive effect, which has led to its recreational use, with its smell being described as that of old socks or dirty feet. It was first documented in 1844 and came into medical use in 1867.
In chemistry, cyanide is a chemical compound that contains a C≡N functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.
Hydrogen cyanide is a chemical compound with the formula HCN and structural formula H−C≡N. It is a highly toxic and flammable liquid that boils slightly above room temperature, at 25.6 °C (78.1 °F). HCN is produced on an industrial scale and is a highly valued precursor to many chemical compounds ranging from polymers to pharmaceuticals. Large-scale applications are for the production of potassium cyanide and adiponitrile, used in mining and plastics, respectively. It is more toxic than solid cyanide compounds due to its volatile nature. A solution of hydrogen cyanide in water, represented as HCN, is called hydrocyanic acid. The salts of the cyanide anion are known as cyanides.
A poison is any chemical substance that is harmful or lethal to living organisms. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broad sense.
Acetonitrile, often abbreviated MeCN, is the chemical compound with the formula CH3CN and structure H3C−C≡N. This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture. It is used as a polar aprotic solvent in organic synthesis and in the purification of butadiene. The N≡C−C skeleton is linear with a short C≡N distance of 1.16 Å.
Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.
Methylthioninium chloride, commonly called methylene blue, is a salt used as a dye and as a medication. As a medication, it is mainly used to treat methemoglobinemia by chemically reducing the ferric iron in hemoglobin to ferrous iron. Specifically, it is used to treat methemoglobin levels that are greater than 30% or in which there are symptoms despite oxygen therapy. It has previously been used for treating cyanide poisoning and urinary tract infections, but this use is no longer recommended.
The nitrite ion has the chemical formula NO−
2. Nitrite is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also refers to organic compounds having the –ONO group, which are esters of nitrous acid.
Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite salt. It is a precursor to a variety of organic compounds, such as pharmaceuticals, dyes, and pesticides, but it is probably best known as a food additive used in processed meats and in fish products.
Potassium cyanide is a compound with the formula KCN. It is a colorless salt, similar in appearance to sugar, that is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewellery for chemical gilding and buffing. Potassium cyanide is highly toxic, and a dose of 200 to 300 milligrams will kill nearly any human.
Methemoglobin (British: methaemoglobin, shortened MetHb) (pronounced "met-hemoglobin") is a hemoglobin in the form of metalloprotein, in which the iron in the heme group is in the Fe3+ (ferric) state, not the Fe2+ (ferrous) of normal hemoglobin. Sometimes, it is also referred to as ferrihemoglobin. Methemoglobin cannot bind oxygen, which means it cannot carry oxygen to tissues. It is bluish chocolate-brown in color. In human blood a trace amount of methemoglobin is normally produced spontaneously, but when present in excess the blood becomes abnormally dark bluish brown. The NADH-dependent enzyme methemoglobin reductase (a type of diaphorase) is responsible for converting methemoglobin back to hemoglobin.
Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "rat poison", rodenticides are also used to kill mice, woodchucks, chipmunks, porcupines, nutria, beavers, and voles. Despite the crucial roles that rodents play in nature, there are times when they need to be controlled.
A blood agent is a toxic chemical agent that affects the body by being absorbed into the blood. Blood agents are fast-acting, potentially lethal poisons that typically manifest at room temperature as volatile colorless gases with a faint odor. They are either cyanide- or arsenic-based.
Sodium azide is an inorganic compound with the formula NaN3. This colorless salt is the gas-forming component in some car airbag systems. It is used for the preparation of other azide compounds. It is an ionic substance, is highly soluble in water, and is acutely poisonous.
Poppers is a slang term referring to recreational drugs belonging to the alkyl nitrite family of chemical compounds. When fumes from these substances are inhaled, they act as potent vasodilators, producing mild euphoria, warmth, and dizziness. Most effects have a rapid onset and are short-acting. Its recreational use is believed to be potentially dangerous for people with heart problems, anaemia, or glaucoma. Reported adverse effects include fainting, retinal toxicity, and vision loss.
Histotoxic hypoxia is the inability of cells to take up or use oxygen from the bloodstream, despite physiologically normal delivery of oxygen to such cells and tissues. Histotoxic hypoxia results from tissue poisoning, such as that caused by cyanide and certain other poisons like hydrogen sulfide.
Ethylene glycol poisoning is poisoning caused by drinking ethylene glycol. Early symptoms include intoxication, vomiting and abdominal pain. Later symptoms may include a decreased level of consciousness, headache, and seizures. Long term outcomes may include kidney failure and brain damage. Toxicity and death may occur after drinking even in a small amount as ethylene glycol is more toxic than other diols.
Methanol toxicity is poisoning from methanol, characteristically via ingestion. Symptoms may include a decreased level of consciousness, poor or no coordination, vomiting, abdominal pain, and a specific smell on the breath. Decreased vision may start as early as twelve hours after exposure. Long-term outcomes may include blindness and kidney failure. Blindness may occur after drinking as little as 10 mL; death may occur after drinking quantities over 15 mL.
Poisoning is the harmful effect which occurs when toxic substances are introduced into the body. The term "poisoning" is a derivative of poison, a term describing any chemical substance that may harm or kill a living organism upon ingestion. Poisoning can be brought on by swallowing, inhaling, injecting or absorbing toxins through the skin. Toxicology is the practice and study of symptoms, mechanisms, diagnoses, and treatments correlated to poisoning.
Sodium thiosulfate, also spelled sodium thiosulphate, is used as a medication to treat cyanide poisoning, pityriasis versicolor, and to decrease side effects from cisplatin. For cyanide poisoning, it is often used after the medication sodium nitrite and is typically only recommended for severe cases. It is either given by injection into a vein or applied to the skin.
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