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Antiarrhythmics in Cardiac Arrest

Question# 772

Previous Companion Document "Antiarrhythmic is indicated (if not previously maxed out) following the shock if the patient had been previously defibrillated or following a second defibrillation if none delivered previously."

Is there a reason this was removed and what is the expectation (i.e. can we administer after the 1st shock?


As per the ALS PCS, antiarrhythmics (amiodarone & lidocaine) are indicated for shockable rhythms (ventricular tachycardia & ventricular fibrillation) in a cardiac arrest. As long as other priorities are being met (CPR, early defibrillation, and epinephrine) there is no need to wait to administer antiarrhythmics.

For a patient who is successfully shocked out of VF/VT, but for whom arrest with VF/VT recurs, antiarrhythmics are indicated (if not already given), and can be given immediately after the shock. These rhythms are bad and recurrence can be controlled with these medications. There is no requirement to wait or to be in shock refractory (x3 defibrillations) to administer amiodarone/lidocaine. Additionally, "The primary objective of antiarrhythmic drug therapy is to facilitate successful defibrillation and to reduce the risk of recurrent arrhythmias, [especially when given early on]. In concert with shock delivery, antiarrhythmics can facilitate the restoration and maintenance of a spontaneous perfusing rhythm." (

If the patient has been successfully defibrillated, whether that be with a ROSC or less desirably into another rhythm such as PEA or asystole, there is no need to give antiarrhythmics as it would be contraindicated and the risks would outweigh the benefits. For example, administering a full dose amiodarone to someone with a pulse would be more harmful and could cause bradycardia and hypotension. If you recall, "Following the initial pulse check, subsequent pulse checks are indicated when a rhythm interpretation reveals a non-shockable rhythm (PEA or Asystole), or there are signs of life present" (Companion Document p. 28). The other risk is focusing on antiarrhythmics instead of early defibrillation and good quality CPR. These are the key principles when assessing risk/benefit. Remember, it’s all about the “why”, as opposed to protocolizing for all scenarios.

"While [antiarrhythmics] have theoretical benefits in selected situations, no medication has been shown to improve long-term survival in humans after cardiac arrest. Priorities are defibrillation, oxygenation and ventilation together with external cardiac compression." ( This is especially true when the paramedic witnesses a cardiac arrest. It would be reasonable to wait until the second analysis analysis (to see if the shock worked) to administer epinephrine/antiarrhythmics while focusing on effective CPR and early defibrillation, as it is possible these priorities convert the patient. The vast majority of the time if someone has a witnessed VT/VF arrest, and it is recognized and shocked quickly, they will convert.

The risk of administering epinephrine immediately after a witnessed VF/VT that is defibrillated is that the patient may now have a pulse. Epinephrine in a patient with a pulse carries a high risk of dysrhythmia, hypertension, and myocardial oxygen demand at a time of deficit. If the initial rhythm is PEA or asystole, epinephrine should be given as soon as possible, as the evidence supports this.

Remember, as per the Companion Document, "If the timing were to fall such that epinephrine and an antiarrhythmic were to be administered within the same CPR cycle, proceed, ensuring to provide a saline flush between the two medications." (p. 28)


Patient Care Standards:

Companion Document (p. 28)

ALS PCS Medical Cardiac Arrest Medical Directive



20 January 2024

ALSPCS Version




Please reference the MOST RECENT ALS PCS for updates and changes to these directives.