We went through an interesting case of a middle aged man found unconscious on the street, who was found to have a large anion and osmolar gap, and was ultimately found to have ethylene glycol toxicity. Along the way, we reviewed several important points:

  1. The importance of getting EKGs on anyone suspected of a toxic ingestion, as it can give you tons of valuable information and can help you diagnostically and therapeutically. You can and should trend EKGs to look for dynamic changes in QRS, QT and ST intervals!
    1. For example: terminal R wave in aVR –> very suggestive of TCA toxicityScreen Shot 2017-07-10 at 11.25.51 AM.pngScreen Shot 2017-07-10 at 11.37.26 AM.png
      Normal aVR
    2. QRS width in TCA poisoning is correlated with badness: QRS >100 is predictive of seizures, and >160 predictive of ventricular arrhythmias. You can and should trend QRS duration on serial EKGs to watch it shrink as you administer sodium bicarbonate!
  2. Toxic alcohols can create an anion and osmolar gap (EXCEPT isopropyl alcohol)

Screen Shot 2017-07-10 at 11.24.33 AM

Remember that sOsm and the anion gap can vary depending on when they’re drawn after the ingestion!

Screen Shot 2017-07-10 at 11.33.17 AM

Lastly, a note about the UDS

1. The ‘level 1’ drug screen (aka DA9) tests for many common drugs: amphetamines, benzos, cocaine, opiates, PCP, THC, methadone, barbiturates, and alcohol. Within those classes, certain drugs may not be tested for (for ex: fentanyl isn’t routinely tested for under opiates). Toxic alcohols are a send out.

2. If you’re looking for a specific drug, ask for a level 2 screen, which tests the sample against a library of 400-500 drugs. You have to have a specific drug(s) in mind- this isn’t just an automatic screen against every compound that wasn’t tested in the level 1!



  1. Yates, C. and Manini, A. 2012. Utility of the Electrocardiogram in Drug Overdose and Poisoning: Theoretical Considerations and Clinical Implications. Current Cardiology Reviews. 8, 2 (2012), 137–151.
  2. Kraut JAXing SX. Approach to the evaluation of a patient with an increased serum osmolal gap and high-anion-gap metabolic acidosis. Am J Kidney Dis 2011;58:480-484
  3. Burns, E. Tricyclic overdose (Sodium-channel blocker toxicity). Life in the Fast Lane. https://lifeinthefastlane.com/ecg-library/basics/tca-overdose/. Accessed July 2017.