Briefly describe methanol poisoning and first aid measures?

Alcohols primarily act on the nervous system, having significant effects that can lead to brain edema. The **concentration of methanol is close to that of LC, hence it poses a greater risk. It has a specific selective effect on the optic nerve and retina, easily causing optic atrophy and leading to blindness in both eyes. Methanol vapor has a strong irritating effect on the respiratory mucosa. The toxicity of methanol is related to the accumulation of its metabolites, formaldehyde and formic acid. It was previously believed that the toxic effects were mainly caused by formaldehyde, which can inhibit the oxidative phosphorylation process in the retina, preventing the synthesis of ATP within the cells; this leads to cell degeneration and ultimately to optic atrophy. Recent studies have shown that formaldehyde is rapidly metabolized into formic acid, and the metabolic acidosis and eye damage caused by acute poisoning are primarily related to the level of formic acid. Methanol inhibits certain oxidase systems in the body, preventing the aerobic breakdown of sugars; this leads to the accumulation of lactate and other organic acids as well as formic acid, thereby causing acidosis. The patient should be immediately removed from the area and have their contaminated clothing removed. For those who ingested it orally, gastric lavage with 1% sodium bicarbonate is performed, along with magnesium sulfate enemas as a laxative. Remove the absorbed methanol from the body. Dialysis therapy: In cases of severe poisoning, hemodialysis or peritoneal dialysis should be initiated as early as possible to alleviate the symptoms of poisoning, save the patient’s life, and reduce complications. The indications for hemodialysis therapy are: ① Blood methanol level >15.6 mmol/L; or formic acid level >4.34 mmol/L; ② Severe metabolic acidosis; ③ Severe visual impairment or papilloretinal edema. Antidote: Ethanol is an antidote for methanol poisoning; its use can prevent the oxidation of methanol and facilitate its elimination from the body. A 5% ethanol solution was prepared using 10% glucose solution, and it was administered via slow intravenous infusion. There is limited clinical experience in the domestic market. Correcting acidosis: Based on blood gas analysis or carbon dioxide combining power measurements, as well as clinical symptoms, sodium bicarbonate solution or sodium lactate solution should be administered promptly. Supportive and symptomatic treatment: Actively prevent and treat cerebral edema according to the condition, reduce intracranial pressure, improve blood circulation in the retina, and prevent optic nerve damage. Maintain respiratory and circulatory functions, and preserve electrolyte balance. Administer large amounts of B vitamins. It has been suggested that formate and 4-methylpyrazole (4MP) can be used to treat methanol poisoning; this has been proven in experimental studies on monkeys, but it has not yet been applied in clinical practice.

The toxic effects of methanol on the human body are caused by methanol and its metabolites, formaldehyde and formic acid, and are characterized primarily by damage to the central nervous system, eye damage, and metabolic acidosis. Methanol itself has **effects** and exhibits direct toxicity toward nerve cells ； Formic acid damages the optic disc and optic nerve, leading to papilledema, demyelination of the optic nerve, and optic nerve damage ； Methanol interferes with the metabolism of certain oxidases in the body, leading to the accumulation of lactic acid and other organic acids. The formation of formic acid, a metabolite of methanol, results in metabolic acidosis. First aid measures: (1) For those poisoned orally, induce vomiting or perform gastric lavage depending on the severity of the condition. Those poisoned by inhalation or transdermal absorption should be immediately removed from the scene, have their contaminated clothing removed, and have their affected skin cleaned. 　　(2) Patients with severe poisoning should be treated with hemodialysis or peritoneal dialysis as early as possible to remove the absorbed methanol and its metabolites. 　　(3) Sodium bicarbonate solution is administered based on the results of blood gas analysis or carbon dioxide combining capacity, as well as clinical symptoms, to correct acidosis. 　　(4) Oral ethanol. Alternatively, ethanol can be mixed in a 5% glucose solution to create a 10% concentration for intravenous infusion, thereby maintaining the ethanol level in the blood at 21.7–32.6 mmol/L. This treatment can be continued for several days in cases of severe poisoning. It has also been suggested that folic acid can be administered intravenously at a dose of 50 mg per time, every 4 hours, for several days. 　　

Occupational methanol poisoning is caused by inhaling methanol vapor during production. Abroad, accidental ingestion of alcohol or beverages containing methanol is the main cause of acute methanol poisoning. In recent years, there have also been several cases in China of poisoning resulting from accidental consumption of alcohol containing methanol. Route of entry: It is primarily absorbed through the respiratory tract and gastrointestinal tract, with partial absorption also possible through the skin. First aid measures: 1. The patient should be immediately moved away from the scene and have their contaminated clothing removed. Those who ingested it orally were given gastric lavage with 1% sodium bicarbonate and laxation with magnesium sulfate. 2. Remove the absorbed methanol from the body. Dialysis therapy: In cases of severe poisoning, hemodialysis or peritoneal dialysis should be initiated as early as possible to alleviate the symptoms of poisoning, save the patient’s life, and reduce complications. Indications for hemodialysis therapy are: ① Blood methanol level >15.6 mmol/L; or formic acid level >4.34 mmol/L; ② Severe metabolic acidosis; ③ Severe visual impairment or papilloretinal edema. Antidote: Ethanol is an antidote for methanol poisoning; its use prevents the oxidation of methanol and facilitates its elimination from the body. A 5% ethanol solution was prepared using 10% glucose solution, and it was administered by slow intravenous infusion. There is limited clinical experience in the domestic market. Correction of acidosis: Based on blood gas analysis or carbon dioxide combining power measurements, as well as clinical symptoms, sodium bicarbonate solution or sodium lactate solution should be administered as early as possible. Supportive and symptomatic treatment: Actively prevent and treat cerebral edema according to the condition, reduce intracranial pressure, improve blood circulation in the retina, and prevent optic nerve damage. Maintain respiratory and circulatory functions, and preserve electrolyte balance. Administer large amounts of B vitamins.

Routes of exposure: inhalation, ingestion, skin contact. Health hazards: It has an **effect on the central nervous system ； It has a specific selective effect on the optic nerve and retina, leading to lesions ； It can cause metabolic acidosis. Acute poisoning: Short-term inhalation of large amounts causes mild irritation of the eyes and upper respiratory tract (oral ingestion leads to gastrointestinal irritation) ； After a period of incubation, headaches, dizziness, fatigue, vertigo, a feeling of being drunk, confusion, delirium, and even coma may occur. Optic nerve and retinal lesions can cause blurred vision, double vision, and in severe cases, blindness. In metabolic acidosis, there is a decrease in carbon dioxide combining capacity and accelerated breathing, among other symptoms. Chronic effects: neurasthenic syndrome, autonomic nervous system dysfunction, mucosal irritation, decreased vision, etc. The skin develops degreasing, dermatitis, and other issues. First aid measures: Skin contact: Remove contaminated clothing and thoroughly wash the skin with soapy water and clean water. Eye contact: Lift the eyelids and rinse with flowing water or saline. Seek medical attention. Inhalation: Quickly move to an area with fresh air. Keep the airway clear. If there is difficulty breathing, administer oxygen. If breathing stops, perform artificial respiration immediately. Seek medical attention. Ingestion: Drink plenty of warm water, induce vomiting, and wash the stomach with water or a 1% sodium thiosulfate solution. Seek medical attention.