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, SC.