Part 3: Defibrillation
Section snippets
Consensus on science
No prospective studies have evaluated the use of the precordial (chest) thump. In three case series (LOE 5)2, 3, 4 VF or pulseless VT was converted to a perfusing rhythm by a precordial thump. The likelihood of conversion of VF decreased rapidly with time (LOE 5).4 The conversion rate was higher for unstable or pulseless VT than for VF (LOE 5).2, 3, 4, 5, 6
Several observational studies indicated that an effective thump was delivered by a closed fist from a height of 5–40 cm (LOE 5).3, 4, 6, 7, 8
Consensus on science
A randomised trial of trained lay responders in public settings (LOE 2)22 and observational studies of CPR and defibrillation performed by trained professional responders in casinos (LOE 5)23 and lay responders in airports (LOE 5)24 and on commercial passenger aircraft (LOE 5)25, 26 showed that AED programmes are safe and feasible and significantly increase survival from out-of-hospital VF cardiac arrest if the emergency response plan is effectively implemented and sustained. In some studies
Position
No studies of cardiac arrest in humans have evaluated the effect of pad/paddle position on defibrillation success or survival rates. Most studies evaluated cardioversion (e.g. atrial fibrillation [AF]) or secondary end points (e.g. transthoracic impedance [TTI]).
Placement of paddles or electrode pads on the superior-anterior right chest and the inferior-lateral left chest were effective (paddles studied in AF, LOE 2;47 pads studied in AF, LOE 3;48 effect of pad position on TTI, LOE 349).
Waveform analysis
VF waveform analysis has the potential to improve the timing and effectiveness of defibrillation attempts; this should minimise interruptions in precordial compressions and reduce the number of unsuccessful high-energy shocks, which cause postresuscitation myocardial injury. The technology is advancing rapidly but is not yet available to assist rescuers.
Initial shock waveform and energy levels
Several related questions were reviewed. Outcome after defibrillation has been studied by many investigators. When evaluating these studies the reviewer must consider the setting (e.g. out-of-hospital versus in-hospital), the initial rhythm (e.g. VF/pulseless VT), the duration of arrests (e.g. out-of-hospital with typical EMS response interval versus electrophysiology study with 15-s arrest interval), and the specific outcome measured (e.g. termination of VF at 5 s).
Consensus on science
Only one small human clinical study (LOE 3)101 compared fixed energy with escalating energies using biphasic defibrillators. The study did not identify a clear benefit for either strategy.
Treatment recommendation
Nonescalating- and escalating-energy biphasic waveform defibrillation can be used safely and effectively to terminate VF of both short and long duration.
Consensus on science
No published human or animal studies compared a one-shock protocol with a three-stacked shock sequence for any outcome. The magnitude of success of initial or
Consensus on science
Collection of data from defibrillators enables a comparison of actual performance during cardiac arrests and training events. The results of three observational studies (LOE 5)117, 118, 119 suggest that the rate and depth of external cardiac compressions and ventilation rate were at variance with current guidelines.
Treatment recommendation
Monitor/defibrillators modified to enable collection of data on compression rate and depth and ventilation rate may be useful for monitoring and improving process and outcomes after
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