What medication is given immediately after defibrillating (defibrillation) a patient in cardiac arrest?

Medication Administration After Defibrillation in Cardiac Arrest

For shockable rhythms (VF/pVT), administer epinephrine 1 mg IV/IO after initial defibrillation attempts have failed, typically after the third shock, and continue every 3-5 minutes (or every second CPR cycle) thereafter. 1

Immediate Post-Shock Medication Protocol

For Shockable Rhythms (VF/pVT)

• Prioritize CPR and defibrillation first before any medication administration—these are your primary interventions for shockable rhythms 1

• Administer epinephrine 1 mg IV/IO after the third shock if the rhythm remains shockable or converts to a non-perfusing rhythm 1

• Continue epinephrine 1 mg every 3-5 minutes (operationally, every second CPR cycle after the initial dose) throughout the resuscitation 1, 2

• If shock-refractory VF/pVT persists (rhythm continues after ≥1 shocks), consider adding an antiarrhythmic:

  • Amiodarone 300 mg IV/IO as first-line antiarrhythmic, OR 1
  • Lidocaine 1-1.5 mg/kg IV/IO as an alternative to amiodarone 1
  • A second dose of amiodarone 150 mg may be given for recurrent or persistent VF/pVT 3

For Non-Shockable Rhythms (PEA/Asystole)

• Administer epinephrine 1 mg IV/IO as soon as feasible—do not delay for non-shockable rhythms 1

• Continue epinephrine 1 mg every 3-5 minutes throughout the resuscitation 1, 2

Critical Timing Considerations

The literature strongly supports earlier epinephrine administration for better outcomes, particularly in non-shockable rhythms. All 16 observational studies found higher rates of ROSC with earlier epinephrine (defined variably as <3, <5, or <10 minutes), though improvements in survival to discharge were inconsistent 1

• For shockable rhythms: Defibrillation takes priority; epinephrine comes after failed initial shocks 1

• For non-shockable rhythms: Give epinephrine immediately—all observational studies showed association between earlier administration and improved ROSC 1

Important Clinical Caveats

What Epinephrine Does and Doesn't Do

• Epinephrine increases ROSC and short-term survival through alpha-adrenergic vasoconstriction that improves coronary and cerebral perfusion pressure 1, 2, 4

• Epinephrine does NOT improve long-term survival with favorable neurological outcomes—this is consistently shown across multiple trials 5, 6, 4

• The drug increases both favorable AND unfavorable neurological outcomes because it increases overall survival, but many survivors have poor neurological function 1

Antiarrhythmic Limitations

• Neither amiodarone nor lidocaine improve long-term survival or neurological outcomes, despite improving ROSC and hospital admission rates 1, 6

• These medications are most beneficial in bystander-witnessed arrests, suggesting a time-dependent effect 1

• Do not delay CPR or defibrillation to establish vascular access for medication administration 1

Dosing Pitfalls to Avoid

• High-dose epinephrine (>1 mg) provides no benefit—multiple RCTs show increased ROSC but no improvement in survival to discharge or neurological outcomes 1, 4

• Vasopressin offers no advantage over epinephrine and should not be used as a substitute or addition 1

• Magnesium should not be routinely used for shock-refractory VF/pVT 1

Route of Administration

• IV access is preferred, but if unsuccessful, IO access is equally acceptable for all resuscitation medications 1

• Establishing vascular access should never compromise high-quality CPR or timely defibrillation 1