August 3, 2026

Good morning,

This month we will be focusing on the prehospital management of the poisoned patient. A key component that needs to occur for any potentially poisoned patient, no matter what was ingested, is a 12-lead EKG. Today we will review one of the key things to look for on the EKG, sodium (Na) channel poisoning, and how to treat it. 

The effect of Na channel poisoning on the heart

Drugs that have this effect will bind to Na channels in the heart and prevent them from working, too. The effect of this on the heart is slower conduction between heart cells. The effect on the EKG is that the QRS widens, eventually having a sine wave appearance. If too many channels get blocked, the heart cannot conduct any electricity and goes into asystole. A wide QRS in the setting of acute overdose should be considered sodium channel poisoning until proven otherwise. This EKG depicts the sine wave appearance of a severe Na channel poisoning.

A key clue that you are dealing with an Na channel poison and not ventricular tachycardia is that there will be a tall terminal R wave in aVR. This is a wide and tall R wave with the R component being the final part of the QRS. This sign clinches that you are dealing with an Na channel poison and not ventricular tachycardia. An example of this finding is in the picture below. 

Common examples of Na channel poisons

What types of drugs classically cause Na channel poisoning? Some examples include carbamazepine, cyclic antidepressants (TCAs), diphenhydramine (Benadryl), propranolol, and hydroxychloroquine, among many others. It does not matter what drug caused the Na channel poisoning; all are managed the exact same way! 

Treatment for sodium channel poisoning

Sodium bicarb: We can treat the sodium channel poison by giving the patient more sodium. The bicarb component just happens to be along for the ride. The effect is that more sodium will make it through the channels despite some not working. The effect on the EKG will be that the QRS will shorten. The best part is that this effect is immediate. If the QRS narrows right after pushing sodium bicarb, you both diagnosed and treated Na channel poisoning at the same time. Here is how to manage in the field: 

• QRS > 120ms + acute OD → give sodium bicarb 

• This assumes normal QRS at baseline 

• Note: most patients will be young and likely have normal baseline QRS 

• When in doubt, give the sodium bicarb 

• Dose: 1-2 mEq/kg sodium bicarb 

• 70kg person → 1-2 amps slow IV push 

• Goal: QRS < 120ms 

• If first dose is not effective, consult online medical command for order of additional sodium bicarb

Na channel poisoning is one of the most life-threatening effects of overdoses. OD + prolonged QRS = sodium bicarb!

Be safe and keep up the awesome work! 

Jordan Singer, MD

Images sourced from https://litfl.com/.