Recommended Energy Levels for Three Stacked Shocks in Cardiac Arrest Life Support
For three stacked shocks in a Cardiac Arrest Life Support scenario, the recommended energy levels are 200 J, 200 J, and 360 J when using a monophasic defibrillator. 1
Energy Recommendations by Defibrillator Type
Monophasic Defibrillators
- Initial sequence should use energies of 200 J, 200 J, and 360 J for the three stacked shocks 1
- Subsequent shocks after the initial three-shock sequence should use 360 J 1
- If a coordinated rhythm appears briefly but then deteriorates, either continuing with 360 J or reverting to 200 J is acceptable 1
Biphasic Defibrillators
- For biphasic truncated exponential (BTE) waveforms: initial shock should be 150 J or greater 1
- For rectilinear biphasic (RLB) waveforms: initial shock should be 120 J or greater 1
- For subsequent biphasic shocks, the same initial energy level is acceptable, but it is reasonable to increase the energy level when possible 1
Implementation of Stacked Shocks
Timing and Sequence
- With modern defibrillators, charging times are sufficiently short for three shocks to be delivered within one minute 1
- Pulse checks should only be performed after a shock if the waveform changes to one compatible with cardiac output 1
- If ventricular fibrillation (VF) or ventricular tachycardia (VT) with identical waveform persists after the first shock, proceed immediately to the second shock without checking for a pulse 1
Technical Considerations
- Proper paddle placement is crucial: one paddle below the right clavicle in the mid-clavicular line and the other over the lower left ribs in the mid-anterior axillary line 1
- Ensure adequate contact with the chest wall and proper use of conductive gel to maximize current delivery 1
- In female patients, place the second paddle firmly on the chest wall just outside the position of the normal cardiac apex, avoiding breast tissue 1
Evolution of Defibrillation Protocols
Current vs. Historical Approaches
- Modern guidelines have shifted from the three stacked shocks approach to a single shock strategy followed by immediate CPR resumption 1
- This change was made to minimize interruptions to chest compressions and because of the greater efficacy of biphasic shocks 1
- However, research suggests that a stacked shock strategy may be superior to a single shock strategy for successful defibrillation and better resuscitation outcomes in treating ventricular fibrillation 2
Efficacy Considerations
- First-shock success rates with modern biphasic defibrillators range from 85-90% 1, 3
- Patients who fail to defibrillate on the first shock have significantly lower defibrillation efficacy on subsequent shocks (69% vs. 93%) 4
- Impedance typically changes minimally between consecutive shocks, decreasing by approximately 1-4% 4
Potential Complications and Considerations
- Higher energy shocks (320 J vs. 175 J) have been associated with a higher incidence of atrioventricular block after defibrillation (24% vs. 9%) 5
- Myocardial injury, both functionally and morphologically, may be greater with increasing energies 1
- Patients who survive typically require fewer shocks than those who do not (2.6 vs. 3.6 shocks) 5
Remember that while these energy recommendations are based on established guidelines, the most recent evidence suggests a trend toward single shock protocols in modern practice, with immediate resumption of chest compressions after the shock 1.