Q: Continuous intravenous (IV) lorazepam is frequently used in ICU. Propylene glycol (PG) is the carrier to administer IV lorazepam drip. Prolong use of IV lorazepam may cause propylene glycol toxicity. Which one test could predicts and correlate directly with PG toxicity?
Answer: Osmolal gap
Propylene glycol toxicity may occur with prolong administration of lorazepam or diazepam. It can cause arrhythmia, hemodynamic instability, lactic acidosis, seizure, coma, and eventually multi-system organ failure (MSOF). Propylene glycol causes hyperosmolarity and an anion gap metabolic acidosis. In case of any suspicion, osmolal gap correlates with PG concentrations and can be a reliable surrogate marker of PG toxicity. Treatment is to discontinue the infusion and, if life-threatening, emergent hemodialysis should be instituted.
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