Cyanide poisoning

What is it?	A dangerous poisoning from cyanide compounds
Common symptoms	Headache, dizziness, fast heart rate, shortness of breath
Where it can happen	House fires, metal polishing, some insecticides, eating certain seeds
How doctors treat it	Decontamination, oxygen, special medicine hydroxocobalamin

Cyanide poisoning is when a person is harmed by breathing in, eating, or touching certain dangerous chemicals called cyanides. Early signs include headache, dizziness, fast heart rate, trouble breathing, and vomiting. These symptoms can become serious quickly.

Toxic cyanide compounds include hydrogen cyanide gas and cyanide salts such as potassium cyanide. People can be exposed to cyanide by breathing in smoke from a house fire, working in places where metal polishing happens, using some insecticides, or eating certain seeds like those from apples and apricots. Cyanide interferes with how the body’s cells use oxygen, making it very dangerous.

Doctors may suspect cyanide poisoning in someone who was in a house fire and is not fully conscious, has low blood pressure, or has high levels of lactic acid in the blood. Treatment includes moving the person away from the source, giving them pure oxygen, and using special medicines to help the body get rid of the poison.

Signs and symptoms

If someone breathes in hydrogen cyanide, they may feel very dizzy, get headaches, or have trouble breathing. If there is a lot of cyanide, they could lose consciousness fast, have seizures, and their heart might stop.

If someone is exposed to smaller amounts of cyanide over a long time, like from eating certain foods not prepared properly, they might get weaker, have trouble moving, or have problems with their thyroid or kidneys.

Causes

Cyanide poisoning can happen if someone swallows cyanide salts, drinks a liquid called prussic acid, or breathes in a gas called hydrogen cyanide. This gas can come from special containers used for things like pesticide or insecticide, or from mixing certain chemicals during a fire.

Removal of cyanide poison from cassava in Nigeria

Cyanide can also be found in tobacco smoke, some seeds like almonds and apricots, and foods such as cassava and bamboo shoots.

Mechanism

Cyanide stops cells from using oxygen, which can be very dangerous. It works by attaching to a special part inside cells, stopping it from doing its job. This prevents cells from making the energy they need.

One way to help someone who has been harmed by cyanide is by using a substance called nitrite. This changes a part of the blood so it can grab onto the cyanide instead of the cells, helping to protect them. Even though this method changes how much oxygen the blood can carry, it can still help save a person’s life.

Diagnosis

If a person has cyanide poisoning, their body can't use oxygen properly. This can cause a buildup of a substance called lactate in the blood. If the lactate level is very high, it might be a sign of cyanide poisoning.

Doctors can test for cyanide using special tests. Some tests look for color changes, but these can sometimes be wrong. Other tests use machines to find cyanide or its breakdown products in the blood. Because cyanide leaves the body quickly, doctors often look for a substance called thiocyanate to see if someone was exposed to cyanide.

Treatment

If someone breathes in hydrogen cyanide gas, they should take off their outer clothing and wash their hair. If they touch liquids or powders, they need a full cleaning.

There are several ways to treat cyanide poisoning. These include giving oxygen and using special medicines like sodium thiosulfate. Other treatments can be given by breathing in or through a vein, such as amyl nitrite, sodium nitrite, and sodium thiosulfate. Hydroxocobalamin is also used in the United States. Some treatments help change cyanide into something less harmful. Different countries may use different treatments depending on what they have and what their health experts recommend.

Agent	Description
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. Treatment with nitrites is not innocuous as methemoglobin cannot carry oxygen, and severe methemoglobinemia may need to be treated in turn with methylene blue.
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.
Hydroxocobalamin	Hydroxocobalamin, a form (or vitamer) of vitamin B₁₂ made by bacteria, and sometimes denoted vitamin B_12a, is used to bind cyanide to form the harmless cyanocobalamin form of vitamin B₁₂.
4-Dimethylaminophenol	4-Dimethylaminophenol (4-DMAP) has been proposed 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.
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. 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. 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.) 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.
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).

History

Fires

The República Cromañón nightclub fire started in Buenos Aires, Argentina on 30 December 2004. Many people were hurt, and some sadly passed away from breathing in harmful gases, including carbon monoxide. After the fire, tests showed very high levels of a poisonous gas called cyanide in the air.

On 27 January 2013, a fire at the Kiss nightclub in the city of Santa Maria, in the south of Brazil, caused many people to get sick from poisonous gases. By March 2013, over 245 people had sadly passed away.

Gas chambers

Research on a poisonous gas called hydrogen cyanide helped scientists understand how such gases could be very dangerous. In early 1942, a substance called Zyklon B, which contains hydrogen cyanide, was used by Nazi Germany in places called extermination camps during the Holocaust. This terrible event led to the loss of many lives, especially among Jews.

Hydrogen cyanide gas has also been used in some places for judicial execution in parts of the United States. This was done by mixing potassium cyanide or sodium cyanide with sulfuric acid to create the gas.

Mining and industrial

There have been some sad incidents where cyanide spilled in places like Avellaneda, Argentina, and Baia Mare, Romania. These spills hurt people and the environment.

Murder

There have been terrible cases where people were harmed using cyanide. For example, in 1845, John Tawell became one of the first people arrested using new communication technology. In 1982, the Chicago Tylenol murders happened when someone put cyanide in medicine bottles, hurting many people.

Warfare or terrorism

In 1988, many people sadly passed away in the Halabja massacre due to poisonous gases, and hydrogen cyanide was a suspected cause. In 1995, a plan by the Aum Shinrikyo cult to release cyanide gas in a Tokyo subway station was discovered before it could happen. In 2003, there were reports that Al Qaeda planned to release cyanide gas in the New York City Subway, but this attack did not go forward.

Research

Cobinamide is a special compound that helps make an important substance in our bodies. It can bind to a dangerous chemical called cyanide more strongly than another compound, cobalamin. This means it might be useful for treating people who have been exposed to cyanide in an emergency.

Cyanide poisoning