MED-5. An unusual cause of poisoning.
The ingestion of excessive amounts of medication can cause toxicity
from both the active drug and the inactive ingredients. A careful
analysis of laboratory abnormalities should suggest the diagnosis.
Recently, a 32-year-old female presented to the Emergency Department
with the chief complaint of not wanting to live. Her family reported
that she may have swallowed up to 300 tablets of Tylenol. Her physical
exam was unremarkable, and her mental status was unchanged from
baseline. Initial laboratory values were significant for bicarbonate
level of 23 mmol/L, anion gap of 13, glucose 137 mg/dl, and
acetaminophen level of 719 [micro]g/ml. Within 2 hours, she became
obtunded and she was intubated for airway protection. Four hours later,
an arterial blood gas revealed a metabolic acidosis with a pH of 7.13
and pC[O.sub.2] of 31 mm/Hg. Her bicarbonate level decreased to 6
mmol/L, glucose increased to 437 mg/dl, and lactic acid was elevated at
10 mmol/L. Both the anion gap and osmolar gap were increased, and
propylene glycol was measured at 40 mg/dl. The cause of her lactic
acidosis, hyperglycemia, and hyperosmolarity was determined to be
propylene glycol poisoning. Propylene glycol, a relatively non-toxic
alcohol, is one of the most commonly used vehicles in hydrophobic
compounds. It is used as a preservative in many different medication
tablets and in certain benzodiazepine and anti-convulsant intravenous
solutions. It is also found in household cleaners, hair products, and
skin lotions. When administered in very large quantities, it can cause
lactic acidosis, hyperglycemia, and increased serum osmolarity.
Potentially fatal effects include stupor, seizures, and brady-asystolic
arrests. Though it may produce striking lab abnormalities, deaths
attributed to oral ingestion of propylene glycol have not been reported.
Alan Redding, MD. Medical University of South Carolina, Charleston,