What is anti-freeze poisoning?
Anti-freeze refers to the liquid coolant used in automotive engines. It is also known as radiator fluid. The active compound in most anti-freeze liquids is ethylene glycol. Some anti-freeze liquids may also contain methanol and isopropanol. Anti-freeze poisoning occurs when a person accidently or deliberately ingests anti-freeze coolant liquid containing ethylene glycol, which is toxic to the body.
Ethylene glycol is a colorless, odorless, and non-volatile liquid with a sweet taste. This sweet taste often entices children and animals to consume it accidently. New regulations in the United States now compel manufacturers of anti-freeze to add some bitter-tasting additives (example, denatonium benzoate) to anti-freeze liquids in order to mask the sweet taste of ethylene glycol and deter its consumption.
Apart from accidental deaths, anti-freeze poisoning is also implicated in many cases of deaths caused by acts of murder or suicide. Due to its physical properties, ethylene glycol mixes with various drinks easily and is difficult to detect by odor, smell or taste. However, forensic pathology tests are available to detect cases of anti-freeze poisoning. In addition to anti-freeze automotive coolants, ethylene glycol is also found in brake fluids.
What are the symptoms of anti-freeze poisoning?
There are a multitude of signs and symptoms that accompany anti-freeze poisoning. These include: Nausea, vomiting, abdominal pain, frequent and painful urination, kidney failure, dizziness, stupor, shortness of breath, rapid breathing, diminished reflexes, muscular cramps, paralysis, metabolic acidosis, blindness, seizures, mineral imbalance caused by hypocalcemia, hypomagnesemia and hyperkalemia, and death.
The above mentioned signs and symptoms usually develop in three stages:
- Stage I: This occurs between 30 minutes to 12 hours after consumption of anti-freeze. Gastrointestinal and neurological symptoms predominate in this phase and the effects are similar to that of excessive alcohol consumption.
- Stage II: This occurs between 12 to 36 hours after consumption of anti-freeze. In this stage, the signs of alcohol poisoning seem to resolve. However, cardiovascular damage and metabolic acidosis continue unabated. Most of the deaths due to anti-freeze poisoning occur during this stage.
- Stage III: This occurs between 24 to 72 hours after consumption of anti-freeze. Kidney failure is the main effect at this stage.
It is important to note that not all victims of anti-freeze poisoning go through all the three stages.
What are the causes of anti-freeze poisoning?
By itself, ethylene glycol does not cause the deleterious effects of anti-freeze poisoning. The signs and symptoms of anti-freeze poisoning are caused by the metabolites produced by the breakdown of ethylene glycol. Ethylene glycol is metabolized by the enzyme alcohol dehydrogenase that resides in the liver cells and in the lining of the stomach. Sequential metabolism of ethylene glycol results in the production of glycoaldehyde, glycocolic acid, glycoxylic acid, and oxalic acid.
In addition to ethylene glycol, alcohol dehydrogenase also metabolizes other common additives like methanol and isopropanol. Methanol gets sequentially metabolized into formaldehyde and formic acid. Isopropanol metabolism produces acetone. All these breakdown products of the main components of anti-freeze affect multiple organ systems in the body and cause toxicity. For example, glycolic acid lowers the pH of the blood. Low blood pH causes the affected person to hyperventilate in an effort to get rid of excess carbon dioxide and restore normal blood pH.
Oxalic acid crystals form kidney stones by combining with calcium. This leads to progressive kidney failure. Formic acid causes blindness by damaging the optic nerve. Acetone has a general depressive effect on the central nervous system.
What are the effects of anti-freeze poisoning?
As mentioned above, accumulation of breakdown products of ethylene glycol, methanol and isopropanol causes many deleterious effects across multiple organ systems in the body. This can ultimately prove fatal if not treated promptly. The following are the vital organ systems affected by anti-freeze poisoning:
- Urinary system: Kidney damage due to formation of calcium oxalate crystals is a major effect of anti-freeze toxicity. Urine output is reduced considerably, even to the extent of no urine excretion. Blood may also be seen in urine that is produced. After kidney damage occurs, the prognosis of the patient is not very good.
- Cardiovascular system: Rapid heart rate and low blood pressure are also seen in cases of anti-freeze poisoning.
- Nervous system: A variety of toxicity symptoms in anti-freeze poisoning are associated with the central nervous system. Fatigue, headache, stupor, slurred speech, dizziness, unstable walk, convulsions, and coma can occur. Brain damage that occurs due to anti-freeze poisoning is mostly permanent.
- Visual system: Blindness is the most severe effect of anti-freeze poisoning on the visual system. It is also mostly permanent.
- Respiratory system: Metabolic acidosis that occurs in anti-freeze poisoning results in a drastic change in the blood pH and multiple organ failures. This triggers rapid breathing in order to wash out excess carbon dioxide from the blood. Cessation of breathing may also occur.
What is the treatment for anti-freeze poisoning?
Anti-freeze poisoning is an emergency condition that requires immediate treatment to prevent lethality. CPR and first aid should be provided in case of cardiac arrest. Home remedies should not be tried since they would waste precious time that could mean the difference between life and death. Ethylene glycol poisoning can result in death within 24 hours. Methanol is also extremely toxic and the chances of survival depend on the amount of toxin consumed and the rapidity with which treatment is undertaken.
In the emergency room, the vital signs of the patients would be monitored continuously. These include temperature, pulse, blood pressure and breathing rate. Urine and blood tests would also be conducted to analyze the presence of toxic metabolites. Removal of toxins may require hemodialysis and gastric lavage, which involves passing a tube into the stomach in order to wash out the contents of the stomach. Antidotes such as ethanol will be given to prevent the accumulation of toxins. The antidotes work by blocking the alcohol dehydrogenase enzyme responsible for metabolizing ethylene glycol. This halts the progression of poisoning.
Regardless of these measures, death can result from anti-freeze poisoning if the treatment begins late. The prognosis becomes worse after the kidneys fail. Even when the patient survives, the kidney functions may remain impaired. In addition, any brain damage or loss of vision that occurred due to anti-freeze toxicity is usually permanent. When the treatment begins soon after poisoning, the prognosis is usually good and full recovery is possible.