What to do if you are poisoned by hydrogen cyanide

Many people work in chemical laboratories and are exposed to these chemicals for a long time. They naturally know what is toxic and what is not, so physical protection measures must be in place. They also have to wear masks to avoid inhalation. However, many people don’t know much when they come into contact with them for the first time, and they may be poisoned if they are not careful. It is necessary for us to understand what to do in the event of hydrogen cyanide poisoning?

Product Name

Hydrocyanic acid; Prussic acid; CAS: 74-90-8

Physical and chemical properties

It is a colorless liquid with a slight bitter almond odor, molecular formula CHN. Molecular weight: 27.03. Relative density 0.69. Melting point -14°C. Boiling point: 26°C. Flash point -17.8℃. Vapor density 0.94. Vapor pressure 101.31 kPa (760 mmHg, 25.8°C). The explosion limit of steam and air mixture is 6~41%. Soluble in water and ethanol; slightly soluble in ether. The aqueous solution is weakly acidic.

Entry route

Mainly poisoning by mouth or inhalation. The liquid can be absorbed through the skin and conjunctiva and cause poisoning.

Introduction to Toxicology

It can be absorbed into the human body through various routes. If a non-lethal dose is absorbed, part of it will be exhaled in its original form; most of the cyanide ions can be gradually released from the body's cytochrome oxidase or from the combination with methemoglobin, and under the action of thiocyanic acid in the body, they will combine with thiosulfate ions in the body and be converted into relatively inactive thiocyanate and excreted in the urine.

Toxicity data

Skin absorption of vapor 6760mg/m^3, 50 minutes, no symptoms; absorption occurs at a concentration of 1230mg/m^3. The olfactory threshold is 0.22-5.71 mg/m^3. At 20-40 mg/m^3, mild symptoms such as headache, nausea, vomiting, palpitations, etc. will appear after a few hours. IDLH:+50 ppm [R30]

Pathogenesis: It is mainly due to the combination of cyanide ions and trivalent iron in oxidative cytochrome oxidase, which blocks the electron transfer of trivalent iron during the oxidation process, making tissue cells unable to utilize oxygen and causing internal asphyxiation.

Clinical manifestations

It mainly causes suffocation in body tissues.

Acute poisoning progresses rapidly with no obvious incubation period. The condition is generally serious. After inhaling high concentrations of hydrogen cyanide or taking a large amount of hydrocyanic acid orally, the person will immediately fall into a coma, stop breathing, and die within a few minutes (sudden death). Severe cases but not sudden death: Early symptoms include eye and upper respiratory tract irritation for inhalers and an almond odor in the exhaled breath; oral ingestion causes a burning sensation in the mouth and throat, loose stools, and vomiting, with the vomitus smelling of almonds.

There are also headaches, dizziness, chest tightness, deeper and faster breathing, increased blood pressure, palpitations, increased pulse rate, and bright red skin and mucous membranes. Later, there was chest pressure, difficulty breathing, and confusion. This is followed by convulsions, coma, slowed breathing, low blood pressure, cyanosis, muscle relaxation throughout the body, respiratory arrest, weak and irregular pulse, cardiac arrest, and death. Venous blood is bright red.

Urinary thiocyanate levels may be elevated. People with mild symptoms may experience headache, dizziness, fatigue, chest tightness, difficulty breathing, palpitations, nausea, and vomiting. Contact of hydrocyanic acid with skin or eyes may cause burns. It can also be absorbed and cause poisoning. Diagnostic principles and differential diagnosis: mainly based on exposure history and clinical manifestations. In the early stage of poisoning, there is an almond odor in the exhaled breath or vomitus, and the skin, mucous membranes and venous blood are bright red, which is helpful for diagnosis, but cyanosis may occur in case of respiratory disorders.

The amount of thiocyanate in blood and urine can be used as an exposure indicator. It is affected by smoking and diet and should refer to local normal values. Poisoning occurs rapidly and a diagnosis cannot be made without waiting for test results. It should be differentiated from sudden death or coma caused by other reasons such as poisoning, cerebrovascular disease, myocardial infarction, etc.