Overdoses with antifreeze or other ethylene glycol products.

Antifreeze or Windshield Washer Fluid Overdose

Have you experienced a patient with an Ethylene Glycol or Methanol overdose in your practice?  Perhaps a young child drinks some antifreeze, or someone drinks a bit of windshield washer fluid.  Was it accidental or was it an intentional suicide attempt?  Either way, it doesn't happen all that frequently, but will kill a patient fast.  I've seen two of these in my 24 year career and with rapid and accurate treatment, there have been good outcomes.

Pathophysiology

Ethylene Glycol Metabolization

What happens with these patients?  Your patient ingests some antifreeze in a suicide attempt.  Antifreeze and windshield washer fluid contains Ethylene Glycol.  This is the bad stuff that will kill you fast if we don't realize the severity of this true medical emergency.  Ethylene glycol (C2H6O2) is an odorless, colorless, and sweet-tasting syrupy substance. There are three presentations depending on time after ingestion. 

1. 30 minutes to 12 hours after ingestion the patient will present like they have acute alcohol intoxication.  In addition to appearing drunk, they may have nausea and vomiting, excessive thirst and urination. Providers and caregivers may not know of ingestion and miss this diagnosis unless the patient or family member is forthcoming and advises us of the substance ingested.
2. 12 hours to 36 hours after ingestion, the appearance of alcohol intoxication has subsided, but the poisoning continues as the body begins to metabolize the ethylene glycol into other organic acids.  Tachycardia, tachypnea, dehydration, hypertension, and metabolic acidosis are evident during this time frame.
3. 24 hours to 72 hours the patient experiences renal failure due to the formation of calcium oxalate crystals in the kidneys.  This is no joke, hemodialysis is necessary, sometimes for months.  Severe lethargy, coma, depression, vomiting, seizures, drooling, and anorexia occur during this phase.  Some lab findings will be RBCs, and protein will be in the UA.  Serum Hyperkalemia and low urine output can be present.  The patient may complain of low back pain.

The toxic dose of pure (100%) ethylene glycol is generally accepted to be 0.1mL per kilogram as the threshold for medical treatment of ingestion.  Most automotive ethylene glycol products contain 50% ethylene glycol.  This means for a 75kg adult, 15mL or 1 tablespoon can kill you, for an average 20kg child, its less than a teaspoon.

Diagnosis

So how do we diagnose this overdose?  First we need to know about the ingestion.  Patients may tell us what they ingested, but in the overdose of an uncooperative patient and/or child, it may take a bit of detective work to figure out what has happened.  The clinical symptoms that present are non-specific and may be treated while the underlying poisoning goes untreated.  The best test for this is direct measurement of ethylene glycol, but most hospitals do not have gas chromatography.  The next best indicator that ethylene glycol poisoning is going on is the osmolal gap.  The osmolal gap is measured by determining the actual serum osmolality, then calculating the predicted osmolality based on the patients sodium, glucose, BUN, and any alcohol (ethanol) thats has been consumed.  A large gap will support a theory that ethylene glycol poisoning has occurred, but remember that as the body metabolized the substance, this may not be accurate or other disease processes may also have an abnormal gap. One little tip is that some antifreeze is tinted with fluorescein, the same stuff we use to find corneal abrasions.  Pull out that blue light (woods light) and look around the mouth, emesis, or urine for the fluorescence.

Treatment

Stabilize

If the patient presents within 60 minutes of ingestion, you should consider gastric lavage and nasogastric suction, but the chemical is rapidly absorbed.  Activated Charcoal doesn't help as charcoal doesn't absorb the glycols.  Initial stabilization is important early on, intubate if necessary, treat acidosis cautiously with Bicarb.  If the patient is having seizures, treat with benzos.  Stabilize.  

Antidotes

Once your patient is stable, you really need to involve the Poison Control Center (800)222-1222 as they will have toxicologists available to help make recommendations of care and treatment.  They will also know the location of a lab near you capable of running the ethylene glycol blood levels.  This is important in care of these patients.  Next you need need the antidote.  Ethylene glycol has two antidotes, ethanol and fomepizole. These prevent the metabolism of ethylene glycol to glycolic acid and oxalic acid. 

Ethanol is easy to administer (oral and IV) and many patients have ingested some before presenting for care, this may save their life. Pharmaceutical grade ethanol comes in 5% to 10% preparations and can be given IV; whereas oral ethanol is given in the form of whiskey, bourbon, or vodka.  

Fomepizole is the treatment of choice, but costs around $1000 per gram (and doesn't cause intoxication).  Fomepizole seems to be the drug of choice when treating ethylene glycol and Methanol toxicity and is given 15mg/kg initially, then 10mg/kg until the 48 hour mark, then 15mg/kg again.  Please be aware that fomepizole is dialyzable and special dosing regimens are to be followed when hemodialysis is started.

Hemodialysis

Hemodialysis is highly effective and should be started as soon as possible to remove unmetabolized ethylene glycol and its metabolites from the blood, and should be started as soon as possible in these patients.  Depending on blood levels multiple treatments may be indicated.

Outcomes

Typically if a patient is treated and survives, a full recovery can be expected.  Hemodialysis may be required temporarily in the case of acute renal failure.  Some cases of chronic kidney failure have been reported and require lifelong hemodialysis and/or kidney transplantation.  Patients that present late after ingestion and are comatose, have severe acidosis, hyperkalemia, and seizures predictably have poor outcomes.  After initial stabilization and treatment, please do not forget to consult psychology to treat the underlying cause of the overdose and ensure that the patient is not suicidal.