r/pharmacology • u/nowlistenhereboy • Jun 14 '21

What is the reason why intravenous epinephrine must be diluted more than intramuscular in the setting of cardiac arrest?

Just curious what the physiological reason is that 1:1000 epinephrine is not to be used for cardiac arrest/active CPR.

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u/Mediocre_Doctor Jun 14 '21

I don't like this proportion nomenclature. It's better to state the concentration.

The 1 mg/mL epi has led to fatal med errors:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2826951/

During a day surgery ENT procedure, the surgeon requested local anesthetic for injection (specifically lidocaine 1% with epinephrine 1:100,000) and was handed a pre-drawn syringe. The surgeon injected the medication into the surgical site. Immediately afterward, the patient experienced a cardiac arrhythmia leading to cardiac arrest. Despite full resuscitation measures, the patient died.

Information gathered after the incident indicated that the syringe contained epinephrine 1 mg/mL (1:1,000) intended for topical use, rather than the local anesthetic for injection that was requested.

IIRC the patient recieved up to 30 mg of epinephrine.

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u/nowlistenhereboy Jun 14 '21

Yes but my question is specifically regarding patients who are already in cardiac arrest. It is explicitly stated in protocols that the more concentrated epi cannot be substituted for use in ACLS resuscitation.

My question is if there is an actual physiological reason why the higher concentrated epi would be contraindicated in a patient who already has no heartbeat and you are doing active CPR?