The role of defibrillation in resuscitation
In shockable rhythms, namely ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT), early shock delivery is the most effective causal intervention according to the ERC Guidelines 2025. At the same time, outcome depends on high-quality chest compressions with as few interruptions as possible. The principle for defibrillation during resuscitation is therefore: as early as possible, as safe as necessary and with as little hands-off time as possible.
The following sections summarise the key statements of the ALS chapter of the ERC Guidelines 2025. For device-specific parameters, they refer to the manufacturer's instructions and the guideline text.
Pad position on the defibrillator
Standard: anterolateral
The anterolateral position is the established standard for pad position on the defibrillator:
- Sternal pad: right parasternal, below the clavicle.
- Apical pad: left mid-axillary line, at the level of the V6 lead. The pad should be placed sufficiently laterally so that the myocardium lies within the current path. Placing it too far anteriorly is a common error.
- Self-adhesive pads have advantages over paddles: charging and shock delivery are possible without interrupting compressions until the shock, and the risk to the team is reduced.
Alternative: anteroposterior
The anteroposterior position is an equivalent option. One pad is placed left precordially and one posteriorly between the scapulae. According to ERC 2025, a change of vector from anterolateral to anteroposterior may be considered in shock-refractory VF. The evidence for this is limited. The specific approach follows the ERC guideline text and local protocols.
Practical aspects of placement
- Prepare the chest: dry the skin. If there is heavy chest hair, shave quickly if necessary, without delaying shock delivery.
- Transdermal patches: remove them and wipe the area.
- Implanted devices (pacemaker, ICD): do not place pads directly over the device. If necessary, switch to the anteroposterior position.
- Breast tissue: place the apical pad lateral to or below the breast tissue, not on it.
- Oxygen: remove open oxygen sources (mask, nasal cannula, disconnected bag) from the chest during shock delivery. A closed system via the tracheal tube or supraglottic airway device may remain connected.
Energy selection: device and guideline
General principle
Biphasic defibrillators use different waveforms depending on the manufacturer. The effective energy is therefore device-specific. For defibrillation in cardiac arrest:
- The manufacturer's instructions for the device in use and the current ERC 2025 guideline text are authoritative. Specific joule values are deliberately not given here.
- After an unsuccessful shock or refibrillation, an energy escalation may be considered if the device allows it. Details are given in the ERC Guidelines 2025 (ALS).
- Teams should know the energy settings of their own device before use, for example through device training or a pocket card.
Distinction from synchronised cardioversion
Defibrillation and synchronised cardioversion are easily confused in practice. Separate energy recommendations apply to tachycardias with a pulse and signs of instability (biphasic, first shock):
| Rhythm | 1st shock | Subsequent shocks |
|---|---|---|
| Atrial fibrillation | maximum device energy | maximum |
| Atrial flutter, paroxysmal SVT | 70–120 J | escalate stepwise |
| VT with a pulse | 120–150 J | consider escalation (fixed or escalating acceptable) |
Source: ERC 2025 ALS [1], GRC/ERC peri-arrest tachycardia algorithm [116]
Important safety points:
- Never synchronise in cardiac arrest. In VF, the device does not detect an R wave and will not deliver a shock. Synchronised mode must be switched off before every defibrillation.
- Conversely, some devices revert to asynchronous mode after a cardioversion shock. Synchronisation must therefore be checked again before every further synchronised shock [116].
- Polymorphic VT often cannot be synchronised. In this case, an unsynchronised shock at defibrillation energy is indicated. Unstable torsade de pointes is defibrillated [1, 116].
Shock delivery according to ERC 2025: the safe sequence
Shock delivery according to ERC 2025 follows the principle "brief interruption, safe shock, resume compressions immediately".
Step by step
- Continue compressions while the pads are applied.
- Rhythm analysis with a brief, announced pause.
- Shockable rhythm identified: resume compressions immediately and charge the defibrillator during ongoing compressions.
- Safety check while charging: oxygen away, nobody touches the patient, trolley or ventilation bag. The person delivering the shock gives a clear announcement, for example "Charging – everyone clear except compressions – oxygen away".
- Briefly stop compressions, confirm the rhythm, "Stand clear!", visual check, shock.
- Resume compressions immediately, without a pulse or rhythm check directly after the shock. The next analysis takes place at the end of the cycle according to the ALS algorithm.
- Abort and disarm if the rhythm proves non-shockable on confirmation. Then resume compressions immediately.
Minimising pauses in compressions
The pre- and post-shock pause should be as short as possible. Proven measures include:
- Charging during compressions rather than during the pause.
- Clear allocation of roles: team leader, defibrillation, compressions, airway.
- Pre-announced changes of the person performing compressions, combined with the analysis pause.
- No airway or vascular access procedures that require an additional pause.
- Using capnography as an indicator of ROSC instead of routine pauses for pulse checks.
Witnessed arrest on a monitor
In witnessed and monitored cardiac arrest with a defibrillator immediately available, for example in the cardiac catheterisation laboratory, the intensive care unit or the recovery room, the ERC Guidelines 2025 provide for up to three rapid successive shocks. For drug therapy, these three stacked shocks count as one shock [1].
Drugs in the context of shock counting
Antiarrhythmic drug administration is based on the total number of shocks in persistent or recurrent VF/pVT [1]:
| Timing | Drug | Dose (adults) |
|---|---|---|
| after the 3rd shock | Amiodarone | 300 mg i.v./i.o. |
| after the 5th shock | Amiodarone | 150 mg i.v./i.o. |
| Alternative if amiodarone is unavailable or as locally specified | Lidocaine | 100 mg, then 50 mg |
Adrenaline is given according to the ALS algorithm. Dose and timing should be taken from the current ERC Guidelines 2025. In cardiac arrest, there are no contraindications to amiodarone.
Children: amiodarone is given at 5 mg/kg i.v./i.o. (max. 300 mg) after the 3rd shock. The 2nd dose of 5 mg/kg (then max. 150 mg) follows after the 5th shock [2]. According to the product information, preparations containing benzyl alcohol are contraindicated in neonates, infants and children up to 3 years of age. Energy selection and pad size and position in children follow the ERC Guidelines 2025 Paediatric Life Support.
After successful defibrillation
After ROSC, an ABCDE assessment and a 12-lead ECG should follow immediately. In the presence of ST elevation, immediate coronary angiography is indicated [3]. The targets are:
- SpO₂ 94–98 %
- Normocapnia
- Systolic blood pressure > 100 mmHg or MAP > 60–65 mmHg
In recurrent or refractory arrhythmias after ROSC, electrolytes (K⁺, Mg²⁺) should be corrected and ischaemia treated. Antiarrhythmic drugs or cardioversion follow the tachycardia algorithm [3, 116]. The pads remain in place, as refibrillation may occur at any time.
Common sources of error
- Apical pad placed too far anteriorly or on breast tissue.
- Synchronised mode inadvertently active during cardiac arrest.
- Charging only during the compression pause, which prolongs hands-off time.
- Pulse or rhythm check directly after the shock instead of immediate compressions.
- Unclear communication before shock delivery and an open oxygen source on the chest.
- Incorrect shock counting, leading to incorrect timing of amiodarone administration.
Conclusion
Successful defibrillation during resuscitation rests on four points: correct pad position (anterolateral, alternatively anteroposterior), energy selection according to the manufacturer's instructions and the guideline, charging during ongoing compressions and a standardised, clearly communicated safety sequence. The evidence on shock-refractory VF, for example regarding change of vector, is limited. In these cases, the current ERC guideline text and local protocols are authoritative.
References
- Soar J, Böttiger BW et al. European Resuscitation Council Guidelines 2025 Adult Advanced Life Support. Resuscitation 2025;215 Suppl 1:110769 (Korrigendum 2026).
- Djakow J, Turner NM, Skellett S et al. European Resuscitation Council Guidelines 2025 Paediatric Life Support. Resuscitation 2025;215 Suppl 1:110767.
- Nolan JP, Sandroni C et al. European Resuscitation Council and European Society of Intensive Care Medicine Guidelines 2025 Post-Resuscitation Care. Resuscitation 2025 / Intensive Care Med 2025;51:2213–2288.
- Kurzfassung der Leitlinien des European Resuscitation Council 2025. Notfall Rettungsmed 2025.
- German Resuscitation Council (GRC) / European Resuscitation Council (ERC). Algorithmus Peri-Arrest-Tachykardien bei Erwachsenen, Leitlinien 2025 (deutsche Fassung). [116]
This article does not replace clinical judgement in the individual case or the current summary of product characteristics and guidelines.
