Challenging the rationale of three sequential shocks for defibrillation

Area of Science:

• Emergency Medicine
• Cardiology
• Physiology

Background:

• Current cardiopulmonary resuscitation (CPR) guidelines allow up to three sequential shocks for persistent ventricular fibrillation (VF).
• The efficacy of repeated defibrillation attempts within a single sequence is not fully understood.
• Hypothesis: Time delays for rhythm analysis and capacitor charging reduce the success rate of subsequent shocks.

Purpose of the Study:

• To evaluate the success rates of sequential defibrillation shocks (first, second, and third) in a porcine model.
• To determine if physiological parameters predict successful defibrillation.
• To inform CPR guidelines regarding the optimal number of shocks before resuming chest compressions.

Main Methods:

• Ventricular fibrillation (VF) was induced in 60 domestic pigs and left untreated for 7 minutes.
• One minute of CPR (chest compressions and ventilation) was administered.
• Up to three sequential electrical shocks were delivered for defibrillation.
• Restoration of spontaneous circulation (ROSC) was the primary endpoint.
• Coronary perfusion pressure (CPP) and end-tidal CO2 (ETCO2) were monitored.

Main Results:

• 80% of animals achieved ROSC after the first shock (48/60).
• Success rates decreased significantly with subsequent shocks: 15% (9/60) after the second shock and 5% (3/60) after the third shock.
• Predictive physiological criteria for ROSC (CPP > 12 mmHg, ETCO2 > 11 mmHg) were not met after the second shock.

Conclusions:

• The findings support limiting defibrillation sequences to one or two shocks.
• Resuming chest compressions after a limited number of shocks may be necessary to improve physiological parameters (CPP, ETCO2).
• This approach could enhance the effectiveness of subsequent defibrillation attempts and improve overall resuscitation outcomes.