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The All American Garage Part 1: Toxic Alcohols & Hydrocarbons

Twistadmin Poison Alerts

image32Does anyone actually use their garage for their cars?  There *may* be room for a car among the bicycles, ladders, holiday decorations, hoses, tools and equipment, birdseed, paint cans, toys, car maintenance and lawn care products.  No one is pointing a finger, but some of the chemical products that are commonly found in a garage are potentially toxic if an exposure occurs.  It only takes a small amount of the wrong product to cause an issue. Refresh your knowledge about the top garage hazards as we move through summer, the national garage-cleaning season.

METHANOL & ETHYLENE GLYCOL

Antifreeze/engine coolants, brake fluid, windshield wiper fluid, and engine cleaner often contain these toxic solvents.  They behave similarly once ingested, but target different end-organs.  Because methanol is only half the molecular weight of ethylene glycol, it packs twice the punch in the same volume.  Early assessment and treatment, guided by proper laboratory monitoring, are the keystones to management.

Initial symptoms are similar to ethanol intoxication, but the metabolites are the true toxic danger.  Both agents are metabolized by alcohol dehydrogenase to fixed acids (Figure 1). These cannot be buffered away by bicarbonate, but must be renally excreted or removed by dialysis once they are formed.  As the acids accumulate they cause severe anion gap metabolic acidosis and specific organ damage to the kidney  (ethylene glycol), and retina (methanol).

Figure 1: Toxic Alcohol Metabolism

Antidotal treatment with either fomepizole (Antizol)  OR  beverage ethanol aims to stop toxic metabolism by inhibiting alcohol dehydrogenase.  This prevents generation of fixed acids and allows time for the parent substance to be excreted unchanged.  Fomepizole is preferred because it is easier to dose effectively and has no inherent toxicity of its own.  If fomepizole is not immediately available, ethanol can be started, but should be discontinued once fomepizole arrives.  The antidote does not reverse the metabolic acidosis and adverse effects, it only prevents additional metabolites from adding to the problem.

Other necessary care includes aggressive administration of sodium bicarbonate to temporarily buffer the acidotic pH.  Hemodialysis is often recommended to eliminate the metabolic acids, correct the pH, and accelerate the elimination of the parent molecules.

LOW VISCOSITY HYDROCARBONS

Hydrocarbons run the gamut in consistency from solids to liquids to gases.  Pulmonary aspiration is a mechanical hazard that is associated with liquid hydrocarbons having properties of low viscosity and high volatility, such as gasoline, tiki torch fuel, lamp oil, and lighter fluid.  Low viscosity translates into molecules slipping past each other more readily, so that a swallowed liquid travels faster than water and reaches the larynx before the epiglottis closes.

The liquid enters the lungs, spreading widely, volatilizing and occupying the airspace, and damaging delicate alveolar membranes.  Aspiration can occur during the initial ingestion and also during any subsequent emesis.

Classic hydrocarbon aspiration scenarios are adults siphoning gasoline and children drinking from a container of brightly-colored lamp oil.  Persistent coughing, gagging or choking within 30 minutes of ingestion raises suspicion of pulmonary aspiration, and warrants observation for clinical symptoms of pneumonitis.  The majority of hydrocarbon aspirations will show an infiltrate on chest x-ray within 4 hours of exposure, however, clinical symptoms of pneumonitis may be delayed up to 24 hours.

Treatment is symptomatic and supportive with oxygen and bronchodilators.  In general, corticosteroids are not beneficial for hydrocarbon aspiration pneumonitis and antibiotics are indicated if secondary bacterial infection occurs.

Patients without symptoms of aspiration can be observed at home.  If small amounts are ingested, symptoms may include nausea, vomiting, and persistent belching and can be treated with antacids and small sips of fluids.  Severe systemic effects are not expected unless large amounts are ingested.

With so many products stored in one place, exposures to garage hazards can be difficult to sort out.  Our advice to you is to call the Missouri Poison Center at 888-268-4195 at our private health care provider number.  Our specially trained nurses, pharmacists and medical toxicologist can provide you with the most up to date treatment advice.

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