The mechanism of propylene glycol toxicity is unclear.1, 2 No convincing in vivo evidence exists to blame either byproducts or direct cytotoxicity by propylene glycol.1, 2 Accumulation of propylene glycol leads to increased osmolality and lactic acidosis, which in turn causes hyperosmolality and high anion gap metabolic acidosis. Studies have shown accumulation of propylene glycol in patients who have received a high-dose lorazepam infusion for as little as 48 hours.2 AKI in propylene glycol toxicity has been suggested to be caused by proximal tubular injury.6
The patient presented here developed both high and normal anion gap metabolic acidosis (Table 1). While the high anion gap metabolic acidosis was probably secondary to lactic acidosis, the normal anion gap metabolic acidosis might be attributable to the prolonged intravenous fluid infusion or to an inability of the kidneys to regenerate bicarbonate because of the proximal tubular injury.
Severe thiamine deficiency can also lead to lactic acidosis.7 Although the patient's thiamine level was not checked, he was receiving thiamine supplements during hospitalization.