Antifreeze Poisoning in Humans – Signs and Symptoms

What is antifreeze?

Antifreeze is a also known as radiator fluid and is used to reduce the heat build up in car engines. Almost all antifreezes contain a compound called ethylene glycol, and some also contain methanol and/or isopropyl alcohol (isopropanol). Apart from antifreeze, ethylene glycol may also be found in brake fluid.

What is antifreeze poisoning?

Antifreeze poisoning is a fairly common occurrence with regards to poisoning – both accidental and intentional. Ingestion is the main path of entry into the body. Due to its sweet taste, antifreeze from leaking radiators or spilled bottles are quickly consumed by household pets (like dogs and cats). Infants who can access a poorly secured or open bottle of antifreeze may also be at risk of poisoning. Both these instances are accidental poisoning.

Antifreeze poisoning, like arsenic poisoning, is often implicated in deaths due to poisoning – either murder or suicide.  The sweet taste makes in fairly inconspicuous and if mixed with alcoholic drinks, it is easily missed. However, modern pathology and forensic science has made it easy for a case of antifreeze poisoning to be identified. New regulations in the United States have compelled antifreeze manufacturers to include bitter tasting additives to the final product.

Effects of Antifreeze Poisoning

The effects of antifreeze poisoning are not directly from ethylene glycol but rather as a result of the metabolites (breakdown products of ethylene glycol). Alcohol dehydrogenase (ADH), an enzyme in the liver and also found in the lining of the stomach, is responsible for the breakdown of ethylene glycol.

Ethylene glycol is sequentially metabolized into :

  • Glycoaldehyde
  • Glycolic acid (from glycoaldehyde)
  • Glycoxylic acid (from glycolic acid)
  • Oxalic acid (from glycoxylic acid)

Other additives like methanol and isopropanol are also broken down by ADH. Methanol is metabolized into formaldehyde and then into formic acid. Isopropanol is metabolized into acetone.

The effects of these metabolites affect multiple systems simultaneously. Some of the effects include :

  • Glycolic acid in the blood increases the pH of the blood (acidosis). This leads to hyperventilation as the blood tries expel carbon dioxide and increase the pH.
  • Oxalic acid may form oxalate crystals which bind with calcium in the kidney to form calcium-oxalate stones. These stones cause an obstruction for filtration and lead to renal insufficiency.
  • Formic acid damages the optic nerve leading to blindness.
  • Acetone depresses the activity of the central nervous system (CNS).

Signs and Symptoms of Antifreeze Poisoning

  • Nausea
  • Vomiting
  • Abdominal pain
  • Frequent and/or painful urination
  • Kidney pain and eventually kidney failure
  • Dizziness
  • Stupor similar to intoxication (drunkeness)
  • Shortness of breath (dyspnea)
  • Rapid breathing (tachypnea)
  • Diminished reflexes
  • Muscle spasms (cramps) and twitching
  • Partial or complete paralysis of certain body parts
  • Pancreatitis
  • Metabolic acidosis
  • Blindness
  • Seizures
  • Low levels of calcium (hypocalcemia), magnesium (hypomagnesemia) and a high level of potassium (hyperkalemia) in the blood, similar to fluoride poisoning.

Depending on the quantity of antifreeze consumed and whether prompt medical treatment is sought, antifreeze poisoning will lead to death.

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