There are many chemical substances that can cause loss of consciousness in a short period of time. Here are some common examples: - **Anesthetics** - **Ether**: It is a classic general anesthetic. It has a good anesthetic effect and can quickly suppress the central nervous system, causing people to lose consciousness in a short period of time. However, ether is flammable and explosive, and there are certain risks when using it. - **Chloroform (trichloromethane)**: It was once used as an anesthetic. It can inhibit the brain and cause loss of consciousness. However, chloroform is highly toxic to the liver and kidneys and is now rarely used in clinical anesthesia. - **Sedatives** - **Barbiturates**: Such as sodium thiopental, which can quickly pass through the blood-brain barrier after intravenous injection, inhibit the cerebral cortex, and cause loss of consciousness. It is often used to induce anesthesia. However, overdose of this type of drug may cause severe adverse reactions such as respiratory depression. - **Benzodiazepines**: Like midazolam, they have the characteristics of fast onset and high safety. By acting on the benzodiazepine receptors of the central nervous system, it enhances the inhibitory effect of gamma-aminobutyric acid (GABA), allowing the patient to quickly enter a sedated state and then lose consciousness. It is often used for anesthesia induction, ICU sedation, etc. - **Inhaled drugs** - **Laughing gas (nitrous oxide)**: After inhalation at a certain concentration, it can cause a short-term euphoria, followed by gradual confusion and loss of consciousness. It was originally an anesthetic gas commonly used in dentistry and surgery, but if abused in a non-medical environment, it will cause harm to the human body. - **Halofathane**: It is an inhaled general anesthetic that can quickly cause central nervous system depression and lead to loss of consciousness. However, halothane may cause adverse reactions such as liver damage and arrhythmia, and its use is subject to certain restrictions. - **Others** - **Carbon monoxide**: It has a much higher affinity with hemoglobin than oxygen. After entering the human body, it will bind to hemoglobin to form carboxyhemoglobin, which makes hemoglobin lose its ability to carry oxygen and causes hypoxia in tissues and organs. The brain is most sensitive to hypoxia. Inhaling high concentrations of carbon monoxide in a short period of time can cause symptoms such as headache, dizziness, fatigue, nausea, and vomiting. In severe cases, it can quickly lead to loss of consciousness and even endanger life. - **Cyanide**: Such as hydrogen cyanide, sodium cyanide, etc. After cyanide enters the human body, it will quickly inhibit the activity of cell respiratory enzymes, making cells unable to use oxygen for respiration, leading to tissue cell hypoxia. The central nervous system is most sensitive to hypoxia. Exposure to high concentrations of cyanide in a short period of time can cause people to quickly experience symptoms such as loss of consciousness, convulsions, and respiratory arrest, with an extremely high mortality rate.