methanol poisoning
Introduction
Introduction to methanol poisoning Methanol is one of the main components of industrial alcohol. Volatile, flammable. Ingestion of 5 to 10 ml of methanol can cause poisoning, and 30 ml can cause death. Divided into acute poisoning and chronic poisoning. Acute poisoning causes systemic diseases characterized by central nervous system, eyelid damage and metabolic acidosis. Chronic poisoning can occur vision loss, visual field defects, optic atrophy. basic knowledge The proportion of illness: 0.003% Susceptible people: no specific population Mode of infection: non-infectious Complications: acute pancreatitis arrhythmia
Cause
Causes of methanol poisoning
Methanol is absorbed through the respiratory tract and digestive tract, and the skin can also be partially absorbed. It is distributed in cerebrospinal fluid, blood, bile and urine. The content is extremely high, and the lowest in bone marrow and adipose tissue. The oxidation and excretion of methanol in the body are slow, so there is obvious accumulation. The main toxicity mechanism of methanol is:
1 has an anesthetic effect on the nervous system.
2 methanol dehydrogenase action, metabolic conversion to formaldehyde, formic acid, inhibition of certain oxidase systems, causing aerobic metabolic disorders, accumulation of lactic acid and other organic acids in the body, causing acidosis.
3 due to methanol and its metabolite formaldehyde, formic acid in the aqueous humor and eye tissue content is high, causing metabolic disorders of the retina, easily lead to retinal cells, optic nerve damage and optic nerve demyelination.
Prevention
Methanol poisoning prevention
The production process of manufacturing and application of methanol should be closed, and equipment maintenance should be carried out regularly to prevent running, running, dripping and leaking. When packaging and transporting, personal protection should be strengthened to prevent the container from rupturing or leaking. In addition, it is necessary to strictly maintain the system and prevent misuse of methanol as an alcoholic beverage. Obvious neurological diseases, organic psychosis, retinal and optic neuropathy should be classified as occupational contraindications.
Complication
Methanol poisoning complications Complications Acute pancreatitis arrhythmia
Acute poisoning can be complicated by acute pancreatitis, arrhythmia, elevated transaminases and renal dysfunction. Chronic poisoning can be associated with neurasthenia syndrome and autonomic dysfunction.
Symptom
Symptoms of Methanol Poisoning Common Symptoms: Dizziness, Optic Nerve Nipple, Pale Disability, Ambiguity, Optic Nerve Atrophy, Diplopia, Visual Field, Loss, Loss, Sleep, Debilitation
Acute poisoning is mainly caused by inhalation of methanol vapor or misuse of ethanol. The incubation period is 8 to 36 hours. The early stage of poisoning is drunken, dizziness, headache, fatigue, blurred vision and insomnia, severe convulsions, confusion, and coma. Wait, even death, eyes can have pain, double vision, even blindness, fundus examination of retinal congestion, bleeding, optic nerve head pale and optic atrophy, etc., blood methanol, formic acid increased, individual liver, kidney damage, carbon dioxide binding, Blood gas analysis showed changes in pH, SB reduction, and decreased BE negative value. Chronic poisoning may result in vision loss, visual field defects, optic atrophy, and neurasthenia syndrome and autonomic dysfunction.
Examine
Methanol poisoning inspection
Laboratory tests for severe methanol poisoning generally include: blood methanol and formic acid determination; blood gas analysis; serum electrolyte and amylase determination, blood, urine routine; liver and kidney function and electrocardiogram, brain CT examination.
(1) Determination of blood methanol and formic acid; can help to confirm the diagnosis and guide treatment, and should be determined multiple times when conditions permit. The blood methanol concentration (0.5 mg/L) and the formic acid concentration of non-occupational contacts were 0.07-0.4 mmol/L (3-19 mg/L). When the blood methanol concentration is >6.20mmol/L (200mg/L), central nervous system symptoms may occur; when the concentration is >31.0 mmol/L (1000 mg/L), ocular symptoms may occur. The blood methanol concentration of untreated patients was as high as 46.5~62.0mmol/L (1500~2000mg/L). When the blood formate concentration is >4.34mmol/L (200mg/L), there are many eye damage and acidosis. Due to the different blood collection time, individual differences and the effects of simultaneous intake of ethanol, the above dose-effect relationship is only for reference during diagnosis.
(2) Determination of urinary methanol and formic acid: It is mainly used for biological monitoring of occupational exposure workers, and can also be used as a reference indicator for poisoning diagnosis. The United States ACGIH recommended that the work class does not have urinary methanol 0.47mmol / L (15mg / L) as the biological exposure limit of methanol workers.
(3) Blood gas analysis or carbon dioxide binding force measurement: used to monitor acidosis and determine the severity of the disease. It is best to measure the arterial blood pH and perform blood gas analysis in a conditional unit. In the case of serum bicarbonate L, the blood methanol concentration is mostly >15.6 mmol/L (500 mg/L).
(4) Other tests: When severe poisoning occurs, the average volume of white blood cells and red blood cells increases, the latter is caused by poisoning caused by red blood cells; serum amylase can be increased in oral poisoning patients, liver and kidney function abnormalities in a few patients, and muscle redness in individual patients Proteinuria.
(5) CT examination: It has become an important means for diagnosing acute methanol toxic encephalopathy, and can help to judge the condition and after-sales. Brain CT examination of severely poisoned patients showed a decrease in white matter and basal ganglia density. The decrease in the symmetry density of the lenticular nucleus suggests a softening lesion of the lenticular nucleus, which can occur as early as 3 days after the disease.
Diagnosis
Diagnosis and identification of methanol poisoning
According to the history of exposure, clinical manifestations and laboratory tests, the diagnosis of acute poisoning can be made after the exclusion of other similar diseases. A typical clinical procedure is preceded by central nervous system depression followed by metabolic acidosis, ocular damage, and progressive brain parenchymal damage. Oral poisoning patients have obvious gastrointestinal symptoms, respiratory symptoms can occur in inhaled poisoning. Patients with clear complaints and clear consciousness, such as laboratory tests found acidosis, strongly suggest the possibility of methanol poisoning. For patients with unconscious coma and acidosis, blood glucose measurement and brain CT examination should be performed as soon as possible after the exclusion of diabetes. Because of the vision loss caused by methanol, there are many changes in the fundus and/or visual field. Therefore, only a comprehensive analysis of the patient's complaint and eye examination (pupil, fundus and visual field) can make a more accurate judgment.
According to the "Diagnostic Criteria and Handling Principles of Occupational Acute Methylation Poisoning" (GBl6373-1996), after a short-term exposure to a large amount of methanol, one of the following clinical manifestations may be diagnosed as mild acute poisoning: 1 mild disturbance of consciousness; The nipple is congested, and the visual field examination has a central or paracentral dark spot; 2 mild metabolic acidosis. When one of the following clinical manifestations can be diagnosed as severe acute poisoning: 1 moderate and severe disturbance of consciousness; 2 sharp decline in visual acuity or even blindness, papilledema and even peripheral retinal edema, advanced into optic atrophy; 2 severe metabolic acidosis.
Diseases requiring differential diagnosis include acute methyl chloride poisoning, acute isopropanol poisoning, diabetic ketoacidosis, pancreatitis, meningitis, and subarachnoid hemorrhage. In the early stage of methanol poisoning, it is easily misdiagnosed as upper respiratory tract infection or acute gastroenteritis. In addition, it is necessary to distinguish from the symptoms of excessive drinking.
For long-term contacts, regular medical school visits, including ophthalmology (eye, vision and visual field) examinations.
