Who does this guideline apply to?

This guideline applies to adults who require advanced life support.

Who is the audience for this guideline?

This guideline is for health professionals and those who provide healthcare in environments where equipment and drugs are available.

Recommendations

The Australian and New Zealand Committee on Resuscitation (ANZCOR) make the following recommendations:

1. A defibrillation shock is delivered as soon as a defibrillator is available.
2. Paddles or pads are placed on the exposed chest in an anterior-lateral position or an anterior-posterior position.
3. In patients with an ICD or a permanent pacemaker the defibrillator pad/paddle is placed on the chest wall ideally at least 8 cm from the generator position.
4. Self-adhesive defibrillation pads are used for defibrillation.
5. Biphasic waveforms are used for defibrillation.
6. For Monophasic waveforms: the initial energy level for adults is set at maximum (usually 360 Joules) for all shocks.                  
7. For Biphasic waveforms: the default energy level for adults is set at 200J for all shocks. Other energy levels may be used providing there is relevant clinical data for a specific defibrillator that suggests that an alternative energy level provides adequate shock success (e.g. Usually greater than 90%).
8. If the first shock is not successful and the defibrillator is capable of delivering shocks of higher energy, it is reasonable to increase the energy to the maximum available for subsequent shocks.
9. A single shock strategy is used in patients in cardiac arrest requiring defibrillation for VF or pulseless VT.
10. The use of AEDs to facilitate early defibrillation in hospitals is reasonable, but services that introduce AEDs must be aware of the possible adverse impact of interruptions to CPR, especially in non-shockable rhythms.

A defibrillation shock when applied through the chest produces simultaneous depolarization of a mass of myocardial cells and may enable resumption of organised electrical activity.

A defibrillation shock is indicated for treating Ventricular Fibrillation (VF) and pulseless Ventricular Tachycardia (VT).

The likelihood of defibrillation success decreases with time until definitive treatment (i.e. defibrillation) is initiated.⁵ Interruptions to external cardiac compression (e.g. for rhythm assessment or pulse checks) should be minimised. However, good CPR may even increase the likelihood of defibrillation success.¹ The results of clinical studies assessing the usefulness of a strategy providing a period of CPR before defibrillation rather than a strategy providing immediate defibrillation are not consistent.

In two randomized controlled trials, a period of 1.5 to 3 minutes of CPR by EMS personnel before defibrillation did not improve return of spontaneous circulation (ROSC) or survival to hospital discharge in patients with out-of-hospital VF or pulseless VT, regardless of EMS response interval. One before and after study and another case series failed to demonstrate significant improvements in ROSC or survival to hospital discharge when a strategy of CPR before defibrillation (CPR first) was compared to a shock first strategy. In the Hayakawa study, the CPR first group showed a higher rate of favourable neurologic outcome 30 days and one year after cardiac arrest.

One randomized controlled trial and one clinical trial with historic controls comparing CPR first versus shock first also found no overall difference in outcomes.

However, in both studies, improvements in ROSC, survival to hospital discharge, neurologic outcome and one-year survival were observed in a subgroup of patients who received CPR first where the EMS response interval was greater than 4 to 5 minutes.²

Recommendation

ANZCOR suggest delivering a defibrillation shock as soon as a defibrillator is available [Class A; Consensus expert opinion].

There are no studies in patients with VF/pulseless VT comparing directly the effects of various positions of pad/paddle placement on defibrillation success and ROSC. Most studies evaluate cardioversion (e.g. AF) or secondary endpoints (e.g. transthoracic impedance). Eleven studies found all four positions (anterior-apex, anterior-posterior, anterior-left infrascapular, anterior right-infrascapular) to be equally effective in defibrillation (for VF/pulseless VT) or elective AF cardioversion success.

Four studies support the anterior-posterior position, one study supports the anterior-lateral position and one study supports the anterior-apex position.

Five studies found no effect of electrode position on transthoracic impedance. One study showed that pads/paddles should be placed under the breast tissue and two studies showed that hirsute males should be shaved before to application of pads. Of the 36 studies reviewed, only four examined biphasic waveforms that have gained widespread use.²

Recommendation

It is reasonable to place paddles or pads on the exposed chest in an anterior-lateral position. One paddle or pad is placed on the midaxilliary line over the 6th left intercostal space and the other on the right parasternal area over the 2nd intercostal space [Class A; LOE III-2].  Acceptable alternative positions are the anterior-posterior (for paddles and pads) and apex-posterior (for pads). In large-breasted individuals it is reasonable to place the left electrode pad (or paddle) lateral to or underneath the left breast, avoiding breast tissue. Consideration should be given to the rapid removal of excessive chest hair prior to the application of pads/paddles but emphasis must be on minimising delays in shock delivery ² [Class B; LOE IV].

One study has demonstrated that transthoracic impedance decreased and shock success increased with increasing pad size (from 8 to 12 cm). Ten other studies showed that larger pad/paddle sizes (8 to 12 cm diameter) lowered transthoracic impedance and that maximum pad/paddle size was limited by the chest wall size and anatomy. No data related to survival outcome were included in these studies.²

There is insufficient evidence to recommend a specific electrode size for optimal external defibrillation in adults. However, it is reasonable to use a pad size >8 cm² [Class B; Extrapolated evidence].

Evidence from one small, good quality retrospective control study in 1987 showed that self-adhesive pads were associated with a significantly improved rate of ROSC and hospital admission compared with hand-held paddles. Several studies have shown the practical benefits of pads over paddles for routine monitoring and defibrillation.²

One prospective study comparing pads and paddles found lower transthoracic impedance when paddles applied at an optimal force of 8 kg were compared with pads. In a cohort study in patients with atrial fibrillation (AF) the use of hand-held paddles placed in the anterior-posterior position increased the success rate of monophasic cardioversion compared with similarly placed self-adhesive electrodes for monophasic defibrillation. The overall cardioversion success rate for biphasic defibrillators was high (>95%) in all groups. In the majority of other studies, self-adhesive electrodes are associated with similarly high cardioversion success rates.²

Recommendation

ANZCOR recommend using self-adhesive defibrillation pads in preference to paddles for defibrillation [Class A; Expert consensus opinion]. They are safe and effective and offer advantages (e.g. facilitating pacing, charging during compressions, safety [including removing risk of fires]) over defibrillation paddles [Class A;LOE III-3, Extrapolated evidence].  If paddles are used, the application of firm pressure and conductive gel pads are recommended for maximum electrical contact. Care should be taken to ensure that pads or electrodes are applied in accordance with manufacturer’s instructions and are not in electrical contact with each other [Class A; Expert consensus opinion].

The composition of the conductive material of defibrillation electrodes influences transthoracic impedance. In terms of cardiac arrest outcomes, there is insufficient evidence to recommend a specific composition of the defibrillation electrode conductive material.⁶

In three randomized trials and four other human studies biphasic waveforms had higher shock success rates compared with monophasic defibrillation. Shock success is usually defined as termination of ventricular fibrillation (VF) 5 seconds after the shock.⁶ Another randomized study comparing transthoracic incremental monophasic with biphasic defibrillation for out-of-hospital pulseless VT/VF cardiac arrest found no differences in any outcome.  A single cohort study using the 2000 International Guidelines demonstrated better hospital discharge and neurologic survival with biphasic than with monophasic waveforms. However, there are confounding factors in that the intervals between the first and second shocks (of three stacked shocks) were shorter with the biphasic defibrillators.  There is no clinical evidence for superiority for any specific biphasic waveform over another.²

Recommendation

Biphasic waveforms are recommended to be used for defibrillation [Class A; Expert consensus opinion]. There is insufficient evidence to recommend any specific biphasic waveform. In the absence of biphasic defibrillators, monophasic defibrillators are acceptable [Class B; Expert consensus opinion].

One study showed no survival benefit from a protocol that included a single shock protocol compared to a three-shock protocol. Evidence from three pre-post design studies suggested significant survival benefit with a single shock defibrillation protocol compared with three stacked shock protocols. However, these studies included confounders related to pre-post design and the multiple interventions that were included as part of the defibrillation protocol. Another pre-post study, with fewer confounding factors, showed a significantly lower hands-off-ratio (ie, percentage of total CPR time when no compressions were provided) with the one-shock protocol but no statistical difference in survival.²

One observational study of fixed-dose biphasic defibrillation suggested higher defibrillation success with three shocks. The same paper also suggested that chest compressions immediately following a shock did not result in recurrence of VF. In contrast, another study showed earlier recurrence of VF when chest compressions were resumed immediately after the shock compared with delayed resumption of compressions. There was no difference in total incidence of recurrent VF or outcome. A single study demonstrated early termination of recurrent VF was associated with increased ROSC, but quality of CPR was poor and few patients achieved ROSC. Another study showed decreased survival when defibrillation for recurrent VF was, for a variety of reasons, delayed.²

One randomised controlled clinical trial has been published since 2010 comparing single versus stacked shocks and showed no difference in outcome.⁷

Priorities in resuscitation should include early assessment of the need for defibrillation, provision of CPR until a defibrillator is available, and minimization of interruptions in chest compressions. Rescuers can optimize the likelihood of defibrillation success by optimizing the performance of CPR, timing of shock delivery with respect to CPR, and the combination of waveform and energy levels. Rescuers can safely continue CPR while charging a manual defibrillator.⁸

Recommended shock protocol

It is recommended that a single shock strategy be used in patients in cardiac arrest requiring defibrillation for VF or pulseless VT [Class A; Expert consensus opinion]. When using this strategy, CPR should be resumed immediately following shock delivery and interruptions minimised  [Class A; LOE IV].

CPR should be continued during charging of the defibrillator, and CPR should not be interrupted until rhythm reanalysis is undertaken [Class A; Expert consensus opinion].

Be aware of electrical hazards in the presence of water, metal fixtures, oxygen and flammable substances. Warn of impending discharge by a “stand clear” command.

Check that the victim has a muscle response to the shock and there is ECG (electrocardiogram) evidence of shock delivery. If it does not appear that the shock has been delivered, consider that the “synchronise” mode of the defibrillator may be on or there may be a flat battery, lead fracture, charge dump etc.

If the attempt at defibrillation is unsuccessful:

• Recommence CPR with oxygen (follow algorithm in Guideline 11.2).
• Check paddle or electrode position.
• Check that there is adequate skin contact (clipping or shaving of body hair under the defibrillator paddle/pad may be required).
• Consider changing the defibrillator pads.

AED use should not be restricted to trained personnel. Allowing use of AEDs by individuals without prior formal training can be beneficial and may be life saving. Since even brief training improves performance (e.g. speed of use, correct pad placement), it is recommended that training in the use of AEDs be provided.

Implementation of AED programs in public settings should be based on the characteristics of published reports of successful programs in similar settings.⁹ Services that implement the use of AEDs must be aware of the possible adverse impact of interruptions to CPR, especially in non-shockable rhythms.⁴

Home AED use, for high-risk individuals who do not have an ICD, is safe and feasible and may be considered on an individual basis, but has not been shown to change overall survival rates.⁹

Because population (e.g. rates of witnessed arrest) and program (e.g. response time) characteristics affect survival, when implementing an AED program, community and program leaders should consider factors such as location, development of a team with a responsibility for monitoring and maintaining the devices, training and retraining programs for those who are likely to use the AED, coordination with the local EMS, and identification of a group of paid or volunteer individuals who are committed to using the AED for victims of arrest.⁹

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