Antiarrhythmic Choice

Question#: 694

Question:

Amiodaron vs Lidocaine:

My service uses lidocaine and I've have been asked a few occasions, why it is that we don't carry amiodaron. I understand the previous ALS had "the presence of amiodaron" as a contraindication for lidocaine. What I'm wondering is whether RPPEO has a stance as to which medication you preferred for either tachydysrhythmias or cardiac arrest and whether the presence of one medication over the other may even influence a physicians decision during a patch i.e short distance from hospital, Order to wait for preferred antiarrhythmic

Answer:

As part of the ACLS algorithms, the administration of an antiarrhythmic (amiodarone or lidocaine) is routinely given during tachydysrhythmia and cardiac arrest management. Antiarrhythmics alter the ion permeability across the myocardial members, which stabilizes the ion channels and changes impulse conduction through the myocardium. Lidocaine works specifically on the sodium channel while amiodarone works primarily on the potassium channel, although the drug also affects beta receptors, sodium channels, and calcium channels.

While the algorithms and guidelines speak to its use, the evidence supporting it is limited. To start, when it comes to cardiac arrest, the AHA guidelines give it a classification of recommendations (COR) as 2b, meaning that the benefit is ³ risk (Usefulness/efficacy is less well established by evidence/opinion); and a level of evidence (LOE) of B-R, meaning that the data is derived from one or more randomized trials or meta-analysis of such studies.

Further, the AHA guidelines state that both “demonstrated improved survival to hospital admission but did not improve over- all survival to hospital discharge or survival with good neurological outcome. However, amiodarone and lidocaine each significantly improved survival to hospital discharge in a prespecified subgroup of patients with bystander- witnessed arrest, potentially arguing for a time-dependent benefit and a group for whom these drugs may be more useful.

Ultimately, the major trials comparing lidocaine to amiodarone suggests that either medication provides little survival benefit in refractory ventricular tachycardia (VT) or ventricular fibrillation (VF).

There is similar evidence for the management of hemodynamically stable wide-complex tachycardia. “Because of their longer duration of action, antiarrhythmic agents may also be useful to prevent recurrences of wide-complex tachy- cardia. Lidocaine is not included as a treatment option for undifferentiated wide-complex tachy- cardia because it is a relatively “narrow-spectrum” drug that is ineffective for SVT, probably because its kinetic properties are less effective for VT at hemodynamically tolerated rates than amiodarone, procainamide, or sotalol are. In contrast, amiodarone, procainamide, and sotalol are “broader spectrum” antiarrhythmics than lidocaine and can treat both SVT and VT, but they can cause hypotension.”

At the end of the day, the ‘Provincial Equipment Standard for Ontario Ambulances’ states that either amiodarone or lidocaine is carried, and it does not specify a preference. In line with that, the RPPEO Medical Team also does not have position as to which medication is preferred.

While their decisions won’t be influenced by which medication each ambulance service provider carries, they are scenarios where one would be medication would be preferred over the other. For example, when there is an overdose or concern about a prolonged QT, lidocaine is the preferred agent. When there is a question about SVT with aberrancy and traditional treatment (vagal/adenosine) has failed (and cardioversion isn’t indicated), or narrow complex tachycardias such as a-fib/flutter with RVR where rate/rhythm control is appropriate, then the preferred agent is amiodarone; though in these scenarios, a patch to BHP would be required.

References:
- 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care | Part 3: Adult Basic and Advanced Life
Support
- https://www.uptodate.com/contents/advanced-cardiac-life-support-acls-in-adults?source=history_widget
- https://www.nejm.org/doi/full/10.1056/nejmoa1514204
- https://pubmed.ncbi.nlm.nih.gov/28904070/
- https://thesgem.com/2016/10/sgem162-not-stayin-alive-more-often-with-amiodarone-or-lidocaine-in-ohca/