What is the management approach for shockable and non-shockable rhythms in cardiac arrest?

Management of Shockable and Non-Shockable Rhythms in Cardiac Arrest

For shockable rhythms (VF/pulseless VT), deliver one shock immediately followed by 2 minutes of high-quality CPR starting with chest compressions, while for non-shockable rhythms (asystole/PEA), begin immediate CPR with early epinephrine administration and no defibrillation. 1

Shockable Rhythms (Ventricular Fibrillation/Pulseless Ventricular Tachycardia)

Initial Management

• Deliver one shock (2 J/kg for pediatrics, standard dose for adults) as quickly as possible and immediately resume CPR beginning with chest compressions. 1
• Minimize interruptions between chest compressions and shock delivery, and between shock delivery and resumption of compressions. 1
• Continue CPR for exactly 2 minutes before checking rhythm again. 1

Subsequent Shocks

• After 2 minutes of CPR, check rhythm and recharge defibrillator to higher dose (4 J/kg for pediatrics, maximum 10 J/kg or adult dose). 1
• If shockable rhythm persists, deliver another shock and immediately resume chest compressions. 1
• Do not deliver stacked shocks—one shock per 2-minute CPR cycle is the standard. 1

Medication Administration

• Administer epinephrine 1 mg IV/IO after the third shock if the patient remains unresponsive. 1
• Give amiodarone 300 mg IV/IO (or lidocaine if amiodarone unavailable) after the third shock while continuing CPR. 1
• Repeat epinephrine every 3-5 minutes during ongoing resuscitation. 1

Critical Pitfall

If defibrillation fails to eliminate VF, the incremental benefit of another immediate shock is low—resumption of CPR provides greater value than stacked shocks. 1 CPR provides coronary perfusion that increases likelihood of successful defibrillation with subsequent shocks. 1

Non-Shockable Rhythms (Asystole/Pulseless Electrical Activity)

Initial Management

• Begin high-quality CPR immediately—do not attempt defibrillation. 1
• Administer epinephrine 1 mg IV/IO as soon as possible, ideally within the first cycle of CPR. 1, 2
• Repeat epinephrine every 3-5 minutes throughout resuscitation. 1

Evidence for Early Epinephrine

Early epinephrine administration in non-shockable rhythms is associated with better survival with functional outcomes. 2 This differs from shockable rhythms where evidence for epinephrine benefit is less clear. 2

Rhythm Conversion Considerations

• Conversion from non-shockable to shockable rhythm during resuscitation is associated with improved survival, particularly for initial asystole. 3, 4
• For asystolic patients who convert to shockable rhythms, adjusted odds ratios for survival to discharge are 3.78 and for favorable neurological outcome are 4.15. 3
• For PEA patients, conversion to shockable rhythms does not show the same survival benefit (adjusted OR 1.12 for survival). 3
• Continue advanced resuscitation efforts if conversion to shockable rhythm occurs, as this indicates potential for recovery. 4

Universal CPR Quality Standards (Both Rhythm Types)

Compression Technique

• Push hard: minimum depth of 5 cm (2 inches) in adults. 5
• Push fast: rate of 100-120 compressions per minute. 5
• Allow complete chest recoil after each compression. 5
• Minimize interruptions—maintain chest compression fraction >80%. 5, 6

Ventilation Strategy

• Use 30:2 compression-to-ventilation ratio for single rescuer (15:2 for pediatrics with 2 rescuers). 1, 5
• Once advanced airway is placed, provide continuous compressions at 100-120/minute with 1 breath every 6-8 seconds (8-10 breaths/minute). 1, 5
• Avoid excessive ventilation, which reduces coronary perfusion pressure. 5

Monitoring During CPR

• Use ETCO₂ monitoring and arterial blood pressure (if available) to assess CPR effectiveness. 1
• ETCO₂ values of 15-33 mm Hg during CPR indicate adequate compressions. 1

Post-Resuscitation Care

Temperature Management

• Prevent fever in all patients unresponsive to verbal commands after ROSC. 1
• Target temperature range of 32-36°C is reasonable, with the 2024 guidelines expanding the acceptable range based on TTM2 trial data. 1
• Most trial data comes from patients with shockable rhythms and primary cardiac causes—applicability to non-shockable rhythms and non-cardiac causes remains uncertain. 1

Prognostic Considerations

Initial Rhythm Impact

• Initial shockable rhythms have dramatically better outcomes than non-shockable rhythms (40% vs 5% favorable neurological survival in refractory cardiac arrest). 7
• Even with ECPR availability, non-shockable initial rhythms carry poor prognosis (8% favorable survival with invasive approach vs 49% for shockable rhythms). 7
• Out-of-hospital cardiac arrest overall survival averages 10.4% to hospital discharge with 8.2% achieving good functional status. 6