Amiodarone for Refractory VFVT Arrest

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Amiodarone for Refractory VF/VT Arrest

• Louis Gonzales, LP, NREMT-P
• Dept. of EMS Technology, Temple College
• Prepared for the
• Clinical Research Team
• Williamson County EMS

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Prehospital Amiodarone use in refractory VF/VT
arrest?

• Clinical considerations
• Mechanisms of Action
• Historical Clinical Use Data
• Recent Clinical Trial Data
• AHA ACLS Proposals
• Adults vs. Pediatric patients
• Other
• Costs

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Significant Electropharmacologic Effects -
Summary1

• Effect IV Amiodarone
• Prolonged action potential duration
• Blockade of inactivated Sodium channels
• Slowed phase 4 depolarization in the SA node
• Calcium channel blockade
• AV Node effective refractory period ???
• Atrial effective refractory period ?
• Ventricle effective refractory period ?
• Noncompetitive blockade of ? and ? receptors
• Heart rate -/?
• ? ? increase or decrease effect
  present
• 1. The Role of Intravenous Amiodarone in the
  Management of Cardiac Arrhythmias. Annals of
  Internal Medicine, August 15, 1997. 127 294-303.

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Historical Clinical Use

• Developed as an antianginal agent
• Past Clinical Use
• Focused on oral use in non-arrest patients
• IV use trials also on non-arrest patients
• Recent Clinical Use
• Proven equivalent to others in SVTs but not cost
  effective
• As effective as Bretylium in unstable VT but with
  less hypotension

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Recent Clinical Trial Data

• 1989, Williams, et al
• Higher resuscitation rate when amiodarone used
  after 30 minutes of conventional ACLS
• 1997, Aseem, et al
• Amiodarone found to be effective and safe in
  hemodynamically stable unstable VT and
  effective in VF.

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Recent Clinical Trial Data

• 1999, Kudenchuk, et al
• First prehospital IV use of amiodarone
• Randomized, double-blind, placebo-controlled
• Study focused on refractory VF/VT
• Survival to hospital 44 in amiodarone group
  vs. 34 in placebo group
• No significant improvement in hospital discharge

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Adult vs Pediatric Use

• Very little Pediatric amiodarone use data exists
• Similar or no data exists for other peds
  anti-arrhythmic medications
• ARREST Trial by Kudenchuk did not include
  pediatric patients (lt8 yoa)
• Decisions made for ACLS will likely be adopted
  for peds VF/VT with changes to dosing

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Potential Adverse Effects

• Most Common from ARREST Trial
• Hypotension most common adverse effect
  (especially as IV bolus)
• Bradycardia
• Both effectively managed with sympathomimetics
  and/or vasopressors
• Phlebitis (? risk if drug conc gt 2mg/ml)

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Safety Efficacy

• Aseems 1997 evaluation
• Equivalent safety as compared to standard
  anti-arrhythmics
• Less hypotension as compared to standard
  anti-arrhythmics
• ARREST trial adverse effects manageable
• Comparative efficacy can not be evaluated
• Costs (not specific to WCEMS)
• 56 / 150 mg vial
• 80 / 300 mg vial

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Conclusions Recommendation

• Many EMS systems nationwide are already adopting
  amiodarone use based upon ARREST trial data
• The most likely AHA recommendation for Adult
  VF/VT arrest will be
• Amiodarone, Class IIA therapy, 300 mg IV bolus
  following initial 3 shocks and epinephrine
• Other antiarrhythmics, Class IIB therapies
• Pediatric use has not been decided

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References

• The Role of Intravenous Amiodarone in the
  Management of Cardiac Arrhythmias. Annals of
  Internal Medicine, August 15, 1997. 127
  294-303.
• Amiodarone for Resuscitation after
  Out-of-Hospital Cardiac Arrest Due to Ventricular
  Fibrillation. The New England Journal of
  Medicine, September 16, 1999. Volume 341, No.
  12.
• Drug Formulary, 15th edition, 1997-1998.
  University of Washington Medical Center, Seattle,
  WA.