Hydrocarbons are organic compounds consisting of carbon and hydrogen atoms.
There are three basic structural forms of hydrocarbons:
Two aromatic hydrocarbons that are commonly abused for their euphoric effect include toluene (methylbenzene) and benzene. Toluene is a colorless, clear liquid that has a sweet, distinct smell. It is insoluble in water but soluble in nonpolar compounds. It is widely used as a raw material in the production of organic compounds such as benzene. Toluene and benzene can be found in products such as gasoline, nail polish, hair dye, acrylic spray paint, airplane glue, plastic cement, cleaning products, and paint thinners. Toluene and/or benzene exposure, whether environmental, accidental or intentional, can cause toxicity throughout the body, specifically affecting the pulmonary system, central and peripheral nervous system, gastrointestinal, cardiovascular, renal, hepatic, dermal, and hematological systems. The hallmark complications of toluene toxicity are renal tubular acidosis and hypokalemic paralysis. Benzene is known to cause hematological disorders. Rarely, both can result in death.
Exposure to hydrocarbons is common because these substances are readily found in products like kerosene, gasoline, household cleansers, furniture polish, turpentine and many paint products. Some of the more toxic hydrocarbons are those derived from oil products like gasoline and kerosene. In most cases, exposure to hydrocarbons is accidental. These products may be inhaled, accidentally ingested or may be absorbed from the skin. Children are at the highest risk of death chiefly because of accidental ingestion. The next most common complication is aspiration pneumonitis, followed by CNS and cardiac complications
The effects of toluene and benzene toxicity is usually acquired through inhalation.
Inhalation occurs by three different methods:
Toluene is the most widely abused inhaled volatile drug. Abusers who seek its euphoric effect are typically teenagers and younger adults. According to the Toxic Exposure Surveillance System of the American Association of Poison Control Systems, 54% of the abusers of inhaled volatile substances were teenagers age 13 to 19 years old, and 15% were children aged 6 to 12 years old. In addition, there is a higher incidence of volatile substance abuse in states with larger rural populations and in lower socioeconomic groups.
The toxic potential of hydrocarbons depends on the following:
Toluene and benzene are highly volatile aromatic hydrocarbons with a usual route of exposure in the form of inhalation. Inhalation of an aromatic hydrocarbon can result in systemic absorption and the potential for significant toxicity.
All hydrocarbons, including toluene and benzene, can cause chemical pneumonitis by direct contact with the pulmonary parenchyma and destroying alveolar and capillary membranes. This results in vascular permeability and edema.
All hydrocarbons can cause life-threatening dysrhythmias, such as ventricular tachycardia and ventricular fibrillation.
Central Nervous System Toxicity
Toluene causes euphoria followed by depression.
Renal and Metabolic Toxicities
Toluene specifically causes renal tubular acidosis. The typical metabolic profile is a normal anion gap hyperchloremic acidosis with hypokalemia and a urine pH of 5.5. Toluene’s metabolites, hippuric acid and benzoic acid, are possibly the cause for an elevated anion gap metabolic acidosis. In addition, toluene also causes hypokalemia leading to muscle weakness and if low enough, muscle paralysis. Rhabdomyolysis is a common complication.
Exposure to benzene is associated with an increased incidence of hematologic disorders, such as aplastic anemia, acute myelogenous leukemia, and multiple myeloma.
Toluene is inhaled via the lungs and distributed widely throughout the body, specifically adipose tissue, brain, liver, and kidneys. The liver converts toluene into organic acids. Toluene is metabolized by the cytochrome P-450 system. The end products include benzoic acid and hippuric acid. Hippuric acid is excreted by the kidney. Some toluene is excreted unchanged in expired air and urine.
Benzene is absorbed in the body through inhalation, skin exposure, and ingestion. It is rapidly metabolized in the liver, becomes water soluble, and is excreted by the kidneys within 48 hours. Benzene itself is non-toxic, but its metabolites form in the liver, specifically benzoquinone and malonaldehyde, have bone marrow toxicity.
While taking the history, try to obtain the following information:
Physical Exam for Hydrocarbon Exposure
After exposure to hydrocarbons, any of the following can be present:
Central nervous system
Specific for toluene
Specific for benzene
There are no specific hydrocarbon tests in standard use when evaluating suspected hydrocarbon intoxication.
When evaluating these patients, initial actions include:
Laboratory tests include:
Radiographic tests include:
When treating these patients, the following actions should be taken:
Contact a medical toxicologist or regional poison control center for all symptomatic and asymptomatic exposures to aromatic hydrocarbons or hydrocarbons with toxic additives.
Further observation or hospitalization is required for patients with symptomatic hydrocarbon exposure.
For toluene, the patient should be admitted to correct renal tubular acidosis, hypokalemia, and/or rhabdomyolysis.
For benzene, consult hematologist/oncologist for further evaluation of hematological abnormality.
The management of toluene toxicity is by an interprofessional team that consists of an emergency department physician, internist, hematologist, toxicologist, and poison control. These patients may develop multiorgan failure and rapid management is vital. The care of these patients is supportive with hydration, blood transfusion and reversal of any electrolyte imbalance. The prognosis of these patients is guarded; in the long term exposure to these aromatic compounds increases the risk of certain leukemias and multiple myeloma. (Level V)
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