Cyanide poisoning

A cyanide poisoning , Zyankalivergiftung or cyanide poisoning is a poisoning with cyanides or hydrogen cyanide ( Hydrocyanic acid ). The cyanides include the salts of hydrocyanic acid and organic cyanides in which the cyano group (–C≡N) is bound to an organic radical ( nitrile ). Hydrocyanic acid and cyanide salts are very toxic, while organic cyanides are less toxic. The cyanide ion has a toxic effect. This binds to the iron atom of the mitochondrial cytochrome c oxidase , thereby blocking the enzyme. This stops the cell breathingon what ultimately leads to an " inner suffocation ".

Poisoning with these substances can occur in the industrial and commercial sector as accidents, but also in the private sector as a result of intentional poisoning in the case of murder and suicide. The poison can either be absorbed through the lungs as gaseous hydrocyanic acid (inhalation of cyanide-containing smoke), in liquid form (biting into a hydrocyanic acid capsule in the mouth), or orally as salt (swallowing potassium cyanide ). Toxic absorption through the skin is also possible.

Poisoning

Prussic acid

Hydrocyanic acid ( hydrogen cyanide ) is dangerous to handle because of its low boiling point of 25.7 ° C, especially in liquid form. Hydrocyanic acid has a high vapor pressure even at room temperature and is accordingly highly volatile . Hydrocyanic acid forms explosive mixtures with air in concentrations above 5.6%. While the characteristic bitter almond odor is perceived by the majority of people, 30 to 40% cannot recognize the typical odor of hydrocyanic acid at all for genetic reasons. Poisoning can therefore easily occur through inhalation ( inhalation ). Special safety measures must therefore be taken when handling hydrogen cyanide. Hydrocyanic acid diffuses very easily through the cell membrane. As a very weak acid, 98% of it is dissolved in water in undissociated form.

If a lethal dose of gaseous hydrogen cyanide is inhaled or liquid hydrogen cyanide is introduced into the mouth, unconsciousness occurs immediately and death occurs within seconds (from 2–3 breaths), as the lipophilic hydrogen cyanide molecule can be absorbed very quickly via the lungs and mucous membranes . In the event of a suicide, acidic solutions are often added to potassium cyanide and thereby converted into hydrocyanic acid before ingestion. This acidified solution containing hydric acid is then brought into the oral cavity. For rescue workers and first aiders, there is an acute risk of death if they come into contact with an acidified solution of potassium cyanide during resuscitation attempts.

Unintentional poisoning with gaseous hydrogen cyanide can occur in the commercial sector through inhalation of hydrogen cyanide during electroplating or pest control and in laboratories. Flue gases can also contain large amounts of hydrocyanic acid if nitrogen-containing compounds such as feathers, wool and plastics (e.g. polyacrylonitrile, polyurethane foam) are not completely burned.

Due to the rapid onset of effects in the case of hydrogen cyanide poisoning, there was speculation about the death of Adolf Hitler regarding his ability to act. It was questionable whether he was still able to pull the trigger of a pistol and shoot himself in the temporal lobe after biting into a cyanide capsule.

Toxicity of hydrogen cyanide

Hydrocyanic acid can be absorbed through direct ingestion, through the airways or through the skin. Hydrocyanic acid is extremely toxic, as little as 1–2 mg of hydrogen cyanide per kg of body mass are fatal.

Concentration in air ( ppm )	Effects
2-4	Perception limit through smell
10	PEL exposure limit
20-40	Mild symptoms after several hours
45-54	Tolerable for 30 to 60 minutes without immediate or subsequent damage
100-200	Fatal after 30 to 60 minutes
300	Immediately fatal (without first aid )

Salts of hydrogen cyanide

If the salts of hydrocyanic acid (such as potassium cyanide) are swallowed, death only occurs after a few minutes (15 min to 1 hour), since the cyanide ion must first be converted into resorbable hydrocyanic acid by means of a protonation reaction. Death occurs with acute shortness of breath, headache, nausea and cramps due to respiratory paralysis.

Organic cyanides

Organic cyanides are contained in cyanogenic food plants ( bitter almond , cassava tubers ) - mostly as cyanogenic glycosides . The lethal dose is about 60-80 bitter almonds for an adult and about 10 bitter almonds for a child.

Mechanism of cyanide poisoning

The cyanide ion is toxic. It is either absorbed orally as HCN through the lungs or as cyanide and then converted to HCN in the stomach by gastric acid. The HCN gets into the cell and the mitochondria. There it inhibits the respiratory chain so that the oxygen is no longer processed by the cell (ATP depletion, internal asphyxiation , lactic acidosis).

The primary toxicity is the blockage of oxygen - binding site in the respiratory chain of body cells . The blockage is effected by a chemical bond of the cyanide to the Fe ³⁺ ion of the heme a ₃ - cofactor in the cytochrome c oxidase in the mitochondrion , which is unable to activate for energy resulted in the oxygen. Since the oxygen cannot be used by the cells, the venous blood is still enriched with oxygen. A light red coloration of the skin is therefore a typical sign of cyanide poisoning despite pronounced shortness of breath. The body reacts to the supposed lack of oxygen by increasing the breathing rate, which may further increase the absorption of gaseous hydrogen cyanide. Eventually the cells die from a lack of ATP .

The cyanide is relatively weakly bound to the Fe ²⁺ ion of the hemoglobin, so that inactivation of the hemoglobin plays a subordinate role in the event of poisoning with cyanides.

Symptoms of poisoning

Typical symptoms of poisoning are shortness of breath , bitter almond odor in the exhaled air, irritation of the mucous membranes , reddening of the conjunctiva , disorientation, headache , dizziness , vomiting , cramps , fainting , pink skin color.

A lack of cyanosis in spite of shortness of breath and the simultaneous smell of bitter almonds are signs of cyanide poisoning. In the event of death from hydrocyanic acid, the skin turns light red. Likewise are corpse spots like at a carbon monoxide bright red poisoning. The light red color is caused by the fact that the venous blood is still saturated with oxygen, as this could not be used by the cells due to the blockage of internal breathing. In the event of poisoning with high concentrations, the light red color of the skin may not appear.

In the case of inhalative poisoning with very high concentrations, hyperventilation, respiratory arrest, unconsciousness occur after a few seconds and cardiac arrest within a few minutes.

therapy

Boxes with detoxifying agents in the medical supplies store of the Cologne fire brigade . It contains: sodium thiosulphate 10%, 4-DMAP and toluidine blue

detoxification

The body's own detoxification of small amounts takes place quickly through the coupling of cyanide to sulfur in the liver (liver enzyme is rhodanase ) to form rhodanide , which is then excreted. The body's own detoxification capacity is 0.1–1 mg / (kg * h). In order to accelerate the body's own detoxification, larger amounts of sulfur are administered (intravenous administration of sodium thiosulphate or S-Hydril ).

Antidote

The body's own detoxification is not sufficient in the case of acute poisoning, which is why the administration of 4-DMAP converts approximately one third of the Fe ^{2+ in} hemoglobin into Fe ³⁺ . The converted Fe ³⁺ ( methemoglobin ) binds the cyanide ion more strongly, so that less and less cyanide is bound to the cytochrome in the mitochondria and this is instead coupled to the methemoglobin, thereby releasing the blockage of internal respiration. Measured against the total hemoglobin , a small amount of methemoglobin formation is sufficient to bind a large part of the cyanide ions. The effectiveness of this antidote depends on the concentration of hemoglobin in the blood . In the case of fire gas inhalation, it is essential to ensure that, due to the simultaneous presence of carbon monoxide poisoning, larger amounts of hemoglobin are already bound and can no longer transport oxygen. This poses a great risk of fatal hypoxia in the treatment that converts up to a third of the hemoglobin . 4-DMAP is therefore only the second choice, since 4-DMAP itself can lead to poisoning if overdosed. It should only be used if the diagnosis of cyanide poisoning is confirmed. 4-DMAP is contraindicated in cyanide smoke poisoning because it aggravates the co-existing carbon monoxide intoxication.

As a further measure, isoamyl nitrite could be administered for inhalation, which also causes methaemoglobin formation; this measure should be used with caution because of the risk of a sharp drop in blood pressure. In Germany there is no preparation with this active ingredient on the market; other NO donors such as glycerol trinitrate cause only a very low level of methaemoglobin formation and are not suitable as antidotes.

Treatment of cyanide poisoning without methaemoglobin formation is possible by administering hydroxycobalamin (trade name: Cyanokit approved in the EU since 2007). The drug can be administered without prior checking for carbon monoxide poisoning and is therefore particularly suitable for emergency use after fires with smoke inhalation. The mechanism of detoxification works through the strong coordination of the cyanide on the central cobalt ion of the cobalamine and the subsequent excretion of the complex in the urine. The use of hydroxycobalamin has a good risk-benefit ratio and should therefore be administered in suspected cases. This antidote has not yet been officially approved in Germany; it has been used on a trial basis in individual regions (such as the Munich fire service ). Cases are also known in which kelocyanor was used as an effective antidote, also by binding cyanide ions.

Others

• Wherein as gentian murder passed through the media attempted suicide with manslaughter cyanide a Enzianschnaps had been added.
• In the gas chambers of the National Socialist concentration camps , the hydrocyanic acid-containing preparation Zyklon B from Degesch was used for mass killing .
• When the explosion in Tianjin on August 12, 2015, a warehouse with several hundred tons of sodium cyanide was destroyed and the poison was released.
• In the film “ Four Women and a Murder ” the murderer tries to poison the leading actress and hobby detective “ Miss Marple ”, who is on his trail, with cyanide. However, this fails.

Individual evidence

1. ↑ ^{a b c} Franz-Xaver Reichl, Jochen Benecke: Pocket Atlas of Toxicology. Year ?, p. 134.
2. ↑ Entry on nitriles. In: Römpp Online . Georg Thieme Verlag, accessed on December 19, 2013.
3. ^ Fatal poison attack on BASF employees. In: Chemistry in Everyday Life. 2006.
4. ↑ Entry on hydrocyanic acid intoxication in Flexikon , a wiki from DocCheck , accessed on November 26, 2015.
5. ↑ ^{a b Ability to} act in the case of fatal oral poisoning with cyano compounds. In: Forensic Medicine. (1999) 9, pp. 56-61.
6. ^ GR Maxwell et al. In: Journal of Hazardous Materials. 142 (2007), pp. 677-684.
7. ^ Franz-Xaver Reichl, Jochen Benecke: Pocket Atlas of Toxicology. Year ?, p. 135.
8. ^ Richard C. Dart: Hydroxocobalamin for Acute Cyanide Poisoning: New Data from Preclinical and Clinical Studies. In: New Results from the Prehospital Emergency Setting. 2006, Vol. 44, No. s1.
9. ↑ Indication of hydroxycobalamin in cyanide poisoning from clinic and research 2013
10. ↑ Facts About Cyanide Poisoning. Merck Magazine, accessed February 26, 2014 . 
11. ↑ B. Hillman, KD Bardhan, JTB Bain: The use of dicobalt edetate (Kelocyanor) in cyanide poisoning. In: Postgrad Med J. Mar 1974; 50 (581), pp. 171-174. PMC 2495530 (free full text)
12. ^ Helmut Schubothe: Poisonings. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition ibid 1961, pp. 1195-1217, here: pp. 1209 f. ( Hydrocyanic acid poisoning ).
13. ^ Sodium cyanide the poison over Tianjin , n-tv from August 16, 2015
14. ↑ Sodium Cyanide - The Devil's Stuff That Poisons Tianjin , Die Welt, August 15, 2015

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