IMPORTANCE OF CHAIN OF SURVIVAL

The term ‘chain of survival’ has been used to define the important links in the chain for the resuscitation process.¹⁰ The key links, which apply to both in- and out-of-hospital cardiac arrests, are: early recognition and the summoning of help, early basic life support (BLS), early access to defibrillation and early ALS, including postresuscitation care.¹⁰

RECENT CHANGES TO GUIDELINES

As a result of the science review published in 2005,¹² a number of important changes have been made to the guidelines for both basic and ALS.

In summary, the BLS changes include:

The ALS changes include:

These changes are discussed in more detail in the sections that follow.

COMMENCEMENT OF CPR

The use of a pulse check as a means of determining the need for external cardiac compressions was downplayed in the 2000 guidelines, largely as a result of the review of a number of papers suggesting that even experienced providers may have difficulty in accurately assessing the presence or absence of a pulse.¹⁸ This was again confirmed in the current guidelines, where it has been recommended that CPR be commenced if the victim has no signs of life (unconscious/unresponsive, not breathing normally and not moving).¹⁶ An appropriately trained ALS provider can check for a central pulse (e.g. carotid) for up to 10 seconds during this period of assessment for signs of life.

EXTERNAL CARDIAC COMPRESSION

MINIMISE INTERRUPTIONS TO COMPRESSIONS

Interruptions in chest compressions (‘hands-off time’) are common, often prolonged, and are associated with a decrease in coronary perfusion pressure and a deceased likelihood of defibrillation success.^20–22 These adverse effects commence within 10 seconds, but appear to be at least partially reversible with the recommencement of chest compressions.²³ It is recommended that CPR (initial breaths, then chest compressions) be commenced as soon as the victim is confirmed to have no signs of life. Pauses in compressions for rhythm recognition or specific interventions (such as ventilations, defibrillation or intubation) should be minimised.

COMPRESSION–VENTILATION RATIO

The minute ventilation requirements during cardiac arrest are less than that in the non-arrested state, so the respiratory rate can be decreased. To increase the number of compressions given per minute, minimise interruptions to chest compressions and simplify instruction for teaching and skills retention, a single compression-to-ventilation ratio of 30:2 is recommended for adult BLS before the airway is secured (irrespective of the number of rescuers).² The tidal breath should be delivered within 1 second, and the desired tidal volume to be delivered is one that results in a visible chest rise.²

MONITORING THE QUALITY OF CPR

A number of different techniques are available to monitor the quality of CPR, some of which are more applicable toALS. Simple monitoring techniques include observation of the rate, depth and positioning of chest compressions, the rate and depth of ventilation and palpation of central pulses. Additional monitoring techniques that can be used include end-tidal carbon dioxide (Table 17.1), mechanical devices (e.g. for monitoring the depth of compressions) and new monitor/defibrillators (e.g. for monitoring the depth and rate of compressions and ventilation). Feedback from these devices can improve the quality of CPR and should result in improved outcomes.²⁴

Table 17.1 Utility of end-tidal carbon dioxide (ETCO₂) monitoring during cardiac arrest²⁴

‘COMPRESSION-ONLY’ CPR

Increasing anxiety about the performance of mouth-to-mouth ventilation has required the consideration of an alternative approach to traditional bystander CPR. A number of animal studies have suggested that ventilation may not be necessary during the initial phase of resuscitation from an arrest of a cardiac cause (e.g. where VF was electrically induced).² Recent research in human out-of-hospital cardiac arrests suggests that outcomes are not worse and may actually be better if ventilation is not initially attempted,^25,26 although no studies have compared ‘compression-only’ CPR with the BLS protocols that are currently recommended. It is recommended that if rescuers are unable, not trained, or unwilling to perform mouth-to-mouth ventilation (rescue breathing) then they should perform ‘compression-only’ CPR.

DEFIBRILLATION

Defibrillation is no longer only the domain of ALS. BLS providers are now often taught how to use an automated external defibrillator (AED). ALS providers can use defibrillators in automated or manual modes. Defibrillation remains the definitive treatment for VF, and it requires an appropriate combination of defibrillator waveform and energy level. Recent research has emphasised the importance of the timing of defibrillation in relation to other interventions.

WAVEFORM FOR DEFIBRILLATION

No specific defibrillator waveform (either monophasic or biphasic) is consistently associated with a greater incidence of return of spontaneous circulation (ROSC) or increased hospital discharge rates from cardiac arrest due to VF.²⁹ Defibrillation with biphasic waveforms (either truncated exponential or rectilinear), using equal or lower energy levels, appears at least as effective for termination of VF as monophasic waveforms.^30,31

ENERGY LEVELS

Recommendations for energy levels to be used for defibrillation vary according to the type of defibrillator (and the specific waveform) that the rescuers are using. Previous recommendations regarding energy levels were based on studies using monophasic waveforms that demonstrated increased heart block with higher energy levels. Current recommendations are based on maximising the likelihood of the success of each shock. The recommended energy level for defibrillation in adults where monophasic defibrillators are used is 360 J for all shocks. When using biphasic waveforms, the energy level should be set at 200 J for all shocks, unless there are relevant clinical data for the specific defibrillator that suggest that an alternative energy level provides adequate shock success (e.g. > 90%). There is no consistent evidence (e.g. survival benefit) to suggest that an escalation of energy levels is required for subsequent shocks.^29,32

SINGLE-SHOCK TECHNIQUE

The use of a single-shock strategy for defibrillation is now recommended (i.e. deliver a single shock and then immediately commence CPR, rather than deliver up to three shocks in a sequence). This strategy has been proposed to decrease the interruptions to chest compressions which occur as a result of the repeated assessment of rhythm and signs of life that were inherent in the stacked-shock approach.²⁹ This protocol would be of particular benefit in scenarios where there is a significant time required for rhythm recognition and recharging of the defibrillator (i.e. > 10 seconds), such as with AEDs. The benefits of this strategy are clearly dependent on the quality of CPR, as the next shock will be delayed for at least 2 minutes while CPR is performed.

The Australian Resuscitation Council does however recommend the retention of a stacked-shock strategy (up to three shocks as necessary) in a specific circumstance: for the first defibrillation attempt in a witnessed arrest, where a manual defibrillator is immediately available, and the time required for rhythm recognition and charging of the defibrillator is short (e.g. < 10 seconds), resulting in delivery of the (up to) three shocks within 30 seconds. All subsequent shocks should be given using a single-shock strategy (see www.resus.org.au).

ADVANCED LIFE SUPPORT FLOWCHART

The recommended sequence of treatment to be followed is designated on the ALS flowchart of the Australian Resuscitation Council (www.resus.org.au; Figure 17.2). This is designed to be used as an aide-mémoire and a teaching tool.

Figure 17.2 Advanced life support flowchart.

(Reproduced from the Australian Resuscitation Council (www.resus.org.au), with permission.)