What Is Methanol Poisoning

Introduction 

Definition of methanol poisoning 

Methanol is a poisonous liquor that is utilized economically as a solvent, pesticide, and elective fuel source.  Poisoning can be characterized as any substance that is damaging when ingested, infused or consumed through the skin. Methanol poisoning is frequently caused by coincidental or purposeful ingestions and inadvertent plague poisonings due to refining and ageing mistakes and refreshment defilement.^1,2 Most methanol poisonings happen because of drinking refreshments polluted with methanol.  Methanol abuse has the second-highest mortality rate. 

Causes and sources of methanol poisoning 

The following list contains sources of methanol: 

Industrial and Household Products 

In industry, methanol is utilized as a modern solvent to assist with making inks, tars, glues, and colours. It is likewise utilized as a  solvent in the production of drugs and items like cholesterol, streptomycin, nutrients and chemicals. Also, household items that contain methanol incorporate windshield washer liquid, gas line liquid catalyst, carburettor cleaner, copier liquid, scents, food warming fuel, and different kinds of fills.^2,3 Methanol is also found in many edible fruits and veggies as well.⁴

Adulterated alcoholic beverages 

Methanol exists in less quantity in products containing alcohol, such as Beer and Wine, but when it is adulterated, it contains large concentrations of methanol, which ultimately leads to serious side effects. Also, it is present in spirits, which contain about 1500 mg/l of methanol.⁴

Accidental exposure 

People get exposed to methanol accidentally at workplaces. People can become intoxicated as methanol can be inhaled or dermally exposed during the varnishing of methanol-containing tanks. Also, when the youngsters/ children try different types of alcohol.⁴

Suicide attempts

Methanol poisoning can happen through ingestion, dermal assimilation, and inhalation. Methanol poisoning had the second highest mortality, and the most widely recognized form of ingestion is through drinking windshield washer liquid in suicide attempts. Methanol is also used as a substitute for ethanol.²

Metabolism of methanol into formaldehyde and formic acid 

• When ingested, methanol is consumed quickly through the GI Tract in under 10 minutes. The process of metabolization happens in the liver through sequential oxidation by enzymes such as alcohol dehydrogenase and aldehyde dehydrogenase. This process is initiated by the oxidation of methanol to formaldehyde by alcohol dehydrogenase, present within the gastric mucosa. Aldehyde dehydrogenase then oxidises formaldehyde to formic acid.^2,5
• Formic acid, a metabolite of formaldehyde, is then detoxified to CO2 and water before turning into formate.^2,5

Symptoms and clinical presentation 

The following symptoms are reported in patients with different levels of metabolic acidosis caused by metabolites of methanol within 1 hour and 72 hours following consumption. 

Early symptoms 

Within the first 12-24 hours, patients tend to experience nausea, vomiting and stomach pain. This is followed by hyperventilation and a decrease in neurological function, where your brain essentially slows down. 

Gastrointestinal distress 

Gastric symptoms:

Nausea, vomiting, absence of a craving (anorexia), serious stomach torment, gastrointestinal dying (drain), loose stools, liver capability irregularities, and inflamed pancreas (pancreatitis).¹

Visual and neurological symptoms 

Visual side effects related to retinal harmfulness: hazy vision, diminished visual sharpness, photophobia, "radiance vision” also inclined toward absolute loss of vision, and seldom eye torment. Visual assessment might uncover unusual discoveries. Fixed enlarged pupils are an indication of extreme ingestion of methanol.^1,2 Neurological symptoms are prominent, such as headache, dizziness, agitation, acute mania, amnesia, diminished level of awareness, including coma, and seizure.¹

Delayed effects

The most widely recognized long-lasting unfavourable effect following serious methanol poisoning is damage to the nerve from the eye to the brain  (optic neuropathy or decay). This damage results in visual impairment. This can also cause neurological symptoms such as trouble with motor functions such as moving.1 Without treatment, patients might go into a coma or have respiratory or circulatory deterioration, and even die.²

Diagnosis and differential diagnosis

Diagnosis involves identifying these symptoms. Another important part of diagnosis is obtaining a full medical history, including medications,or any medical conditions. Additionally, a toxic screen is required to confirm methanol poisoning.⁶

Clinical evaluation 

The underlying clinical assessment of any patient who is poisoned involves: 

The adjustment of the airway to allow the patient to breathe. Additional oxygen supply and intravenous fluids may also be administered to stabilize the patient. Getting a clinical history from the patient might be troublesome on occasion. Clinicians also assess the physical appearance of the patient’s eyes, examine the patient’s breath, and check vital signs such as temperature, heart rate, and respiratory rate. These vitals might indicate how the methanol was ingested.⁷

Laboratory tests: blood methanol levels 

The following tests should be done to evaluate the severity of methanol intoxication (CBC, BUN, creatinine levels, urinalysis, etc).

• Serum methanol level: Assessment of serum liquor level is significant in early long stretches of inebriation. Serum methanol level > 20 mg/dl shows serious methanol poisoning. 

• Serum formaldehyde or formic corrosive level: The presence of these is indicative of methanol poisoning.⁸
• Urinary formic corrosive level: Formic corrosive in urine is assessed by a gas chromatographic strategy. Proof of formic corrosive in urine  Confirms methanol poisoning.
• Blood gas examination in extreme cases  can reveal  serious metabolic acidosis with pH < 7.3
• Other organs are examined to determine the extent of methanol poisoning: Glucose level, liver capability tests, electrolytes, and ECG. X-beam chest is expected in patients.
• Examining electrolyte levels also helps confirm methanol poisoning .⁸

Differential diagnosis

It is based on two criteria: the cause (salicylates, acetaminophen, iron, carbon monoxide, cyanide and alcoholic ketoacidosis) and the probability of consuming another alcohol such as :  ethylene glycol, diethylene glycol, or toluene.²

Medical management and treatment 

Treatment of methanol poisoning includes the following.

Decontamination and supportive care 

The standard decontamination process includes: removing clothes exposed to ethanol, , rinsing eyes and washing surfaces that come in contact with methanol. A gastric lavage following ongoing ingestion (< 60 minutes) can be done to remove ingested methanol. Different techniques are utilized for this process, i.e. use of activated charcoal, whole bowel irrigation and GI decontamination. The following actions should be taken to improve the adverse effects:

• Sodium bicarbonate should be given to improve hyperkalemia and acidosis.
• Proper IV fluids should be administered to improve the urine output.⁹

Antidotes: ethanol and fomepizole 

• Fomepizole is given to counteract alcohol dehydrogenase and treat methanol poisoning.²
• Ethanol is also used to decrease the intoxication of methanol, but it is only utilized when the fomepizole is inaccessible. Although it is inexpensive, it has various side effects and can be toxic if given incorrectly; thus, patients who are treated with ethanol need to be closely monitored.²

Hemodialysis 

Hemodialysis clears methanol and its harmful metabolites from the blood. It is given if the patient's blood methanol level is more than 50 mg/dL has ingested a lot of methanol, is seriously acidotic, or is experiencing changes to their vision.¹⁰

Prevention and public awareness 

Doctors, medical caretakers, and drug specialists ought to perform a proactive part in teaching the general population about the legitimate stockpiling of synthetic compounds containing methanol, for example, windshield washer liquids. Further, individuals who work in an industry where methanol exhaust is produced ought to use legitimate defensive equipment to prevent the risk of ingestion or inhalation. If you suspect someone or yourself has ingested or inhaled methanol, quickly seek medical help.²

Summary

Methanol poisoning is a second cause of mortality and tends to occur accidentally. Ingestion of large amounts of methanol can affect vision and cause neurological defects. The severity of the side effects depends on the concentration consumed. After ingestion, it is metabolized in the liver and by different enzymes and gets converted into formaldehyde and formic acid, which is a toxic metabolite of methanole. Diagnosis requires a  proper examination and several laboratory tests.  Initial treatment includes supportive care to control the adverse side effects, after which a drug,  fomepizole, is given to control the formic acid concentration. If this drug cannot be used, a patient is given ethanol. The process of hemodialysis is done to eliminate the remaining toxins from the body. To prevent such poisoning, it is very important to increase public awareness regarding the storage and placement of methanol. Also, health safety guidelines should be maintained and followed.