What are the causes and methods to reduce peri-shock pause in a patient undergoing cardiopulmonary resuscitation (CPR) with defibrillation?

Peri-Shock Pause: Causes and Reduction Strategies

Peri-shock pauses should be kept to an absolute minimum—ideally less than 10 seconds—as every 5-second increase in pause duration decreases survival to hospital discharge by approximately 14-18%. 1, 2

Understanding Peri-Shock Pause Components

Peri-shock pause consists of two distinct intervals that interrupt chest compressions around defibrillation 1:

• Preshock pause: Time required for rhythm assessment, defibrillator charging, and shock delivery 1
• Postshock pause: Time from shock delivery until resumption of chest compressions 1

Median preshock pauses typically range from 14-23 seconds, while postshock pauses range from similar durations in real-world resuscitations 3

Primary Causes of Prolonged Peri-Shock Pauses

Preshock Pause Contributors

• Rhythm analysis requiring cessation of compressions 1
• Manual defibrillator charging time while compressions are stopped 1
• Rescuer hesitation and lack of coordination between team members 1
• Safety checks before shock delivery 4

Postshock Pause Contributors

• Immediate rhythm and pulse checks after shock delivery 4
• Rescuer uncertainty about resuming compressions 1
• Poor team communication and coordination 1

Additional Pause Sources

In 36% of cardiac arrest cases, the longest pause is actually a non-shock pause (for ventilation, intubation, or IV access), and these patients have significantly lower survival (27% versus 44%) compared to those whose longest pause was peri-shock related 3

Evidence-Based Methods to Minimize Peri-Shock Pauses

Immediate Interventions (Strongest Evidence)

1. Resume Compressions Immediately Post-Shock

• Begin chest compressions immediately after shock delivery without checking rhythm or pulse 1
• This single intervention eliminates the postshock pause entirely 4
• Continue CPR for 2 minutes before the next rhythm check 1

2. Charge During Compressions

• Continue chest compressions while the defibrillator charges 1
• Modern defibrillator software enables rhythm interpretation and capacitor charging during ongoing compressions 1
• This reduces preshock pause to only the few seconds needed for safety clearance before shock delivery 5

3. Optimize Preshock Pause Duration

• Limit preshock pauses to no more than 10 seconds (strong recommendation) 1
• Each 5-second increase in preshock pause decreases shock success (OR 1.86 per 5 seconds) and survival 1, 2
• Preshock pauses ≥20 seconds reduce survival odds by 53% (OR 0.47) 2

Advanced Techniques

4. Artifact Filtering Technology (AFT)

• AFT allows visualization of underlying ECG rhythm during chest compressions 5
• Eliminates the need to pause for rhythm analysis 5
• In simulation studies, AFT increased chest compression fraction from 76.7% to 83.8% and reduced peri-shock pause from 7.4 to 5.3 seconds 5

5. Hands-On Defibrillation

• When combined with AFT, allows shock delivery without pausing compressions 5
• Requires sufficiently insulating gloves for the rescuer performing compressions 4
• Alternatively, mechanical chest compression devices can continue compressions during shock delivery 4
• This approach achieves 86.4% chest compression fraction and reduces peri-shock pause to 2.6 seconds 5

6. Earlier Rhythm Analysis

• Perform rhythm analysis at 1 minute post-shock rather than waiting until immediately before the next shock 6
• In 99.1% of cases, a shockable rhythm at 1 minute post-shock remained shockable at 2 minutes 6
• Caution: Three patients (0.9%) achieved ROSC between 1-2 minutes, so this strategy requires careful consideration 6

Team-Based Strategies

7. Enhance Rescuer Coordination

• Achieving short pauses requires awareness, focused training, and excellent team interplay 1
• Designate one rescuer to operate the defibrillator and announce charging status 1
• Practice coordinated transitions to minimize hesitation 1

8. Maintain High Chest Compression Fraction

• Target chest compression fraction of at least 60% (ideally higher) 1
• Total CPR time devoted to compressions strongly correlates with survival 1
• Monitor and provide real-time feedback on compression quality 1

Critical Pitfalls to Avoid

• Never perform immediate postshock rhythm or pulse checks—this is the most common cause of unnecessary postshock pauses 4
• Do not delay shock delivery for perfect pad positioning (e.g., avoiding pacemakers)—acceptable risk of device damage is far outweighed by survival benefit 7
• Avoid prolonged pauses for ventilation—limit interruptions to less than 10 seconds for 2 breaths in patients without advanced airway 1
• Do not allow rescuer fatigue to prolong pauses—rotate compressors every 2 minutes during rhythm checks 1

Practical Algorithm for Minimizing Peri-Shock Pause

1. During CPR cycle: Continue compressions while second rescuer prepares and charges defibrillator 1
2. Rhythm check: Pause compressions briefly (≤5 seconds) only to confirm shockable rhythm 1
3. Charging: Resume compressions immediately while defibrillator charges 1
4. Pre-shock: Stop compressions only for safety clearance (≤5 seconds) 1
5. Shock delivery: Deliver shock 1
6. Post-shock: Immediately resume compressions without rhythm/pulse check 1
7. Continue: Perform 2 minutes of high-quality CPR before next rhythm check 1

The evidence consistently demonstrates that preshock pauses have greater impact on survival than postshock pauses, though both should be minimized 1, 3, 2. Prolonged peri-shock pauses (≥40 seconds total) reduce survival odds by 46% compared to pauses <20 seconds 2.