Recognition of cardiac arrest, calling for help and starting bystander cardiopulmonary resuscitation (CPR) are the first and second links in the chain of survival (Nolan et al, 2006). Guidelines 2010 recommend deeper chest compressions (5–6 cm) at a faster rate (100–120 per minute), ensuring full recoil, with minimum interruption and with the same 30:2 compression to ventilation ratio. Studies show that the quality of CPR is a key determinant of outcome (Edelson et al, 2006; Christenson et al, 2009).
CPR
Despite much media hype, compression-only CPR is only effective for short periods in individuals who suffer a sudden primary cardiac arrest. Recent studies suggest conventional CPR has better overall outcomes (Ogawa et al, 2011). Ideally, laypeople should be trained to do both chest compressions and ventilations. Instruction in compression-only CPR should however be used by emergency telephone dispatchers to improve bystander CPR rates. Compression-only CPR is better than no CPR and individuals should be encouraged to do chest compressions if they cannot do ventilations. To improve bystander CPR rates, everybody should know CPR, so when training is opportunistic or time limited, even training in compression-only CPR is better than no training at all.
The American Heart Association (AHA) has recently published a statement on the importance of, and rationale for, teaching school children CPR and automated external defibrillator use (Cave et al, 2011). In the UK, the Resuscitation Council (UK) and the British Heart Foundation are also lobbying to have first aid skills including CPR as part of the school curriculum.
Training in resuscitation should emphasize that in an unconscious, unresponsive individual, occasional gasps (agonal breathing) are a sign of cardiac arrest. Gasping can continue or restart during CPR and can therefore also be mistaken for a return of spontaneous circulation (ROSC). Guidelines 2010 therefore recommends that laypeople continue CPR until expert help arrives (this usually means an ambulance crew) or the victim regains consciousness, moves purposefully and starts to breathe normally.
On arrival of emergency service personnel to a cardiac arrest that they had not witnessed, previous guidelines recommended 2 minutes of CPR before rhythm analysis and shock delivery if appropriate. Guidelines 2010 recommend that CPR is started whilst a defibrillator is prepared and attached but 2 minutes of CPR is not necessary before rhythm assessment and shock delivery if appropriate.
Recent studies have failed to show a benefit for a set period of CPR before shock delivery for cardiac arrest (Jacobs et al, 2005; Baker et al, 2008). The key priority is starting CPR and then minimizing interruptions in chest compressions for other interventions, i.e. to do as much as possible with chest compressions ongoing.
Defibrillation strategy
One of the major changes in Guidelines 2010 is the defibrillation strategy. The time between stopping chest compressions and delivering a shock is called the preshock pause. Every 5-second increase in the preshock pause halves the chances of successful defibrillation (Edelson et al, 2006).
In order to minimize the preshock pause, new guidelines for manual defibrillation recommend that there should be a short pause to assess the rhythm and confirm ventricular fibrillation or pulseless ventricular tachycardia (VF/VT).
Chest compressions should then continue whilst the defibrillator is charged. Everyone should then stand clear whilst the shock is delivered. Chest compressions should resume immediately after the shock.
‘One of the major changes is the defibrillation strategy. The new guidelines recommend that there should be a short pause to assess the rhythm and confirm ventricular fibrillation or pulseless ventricular tachycardia ’
The choice of airway
The choice of airway during CPR is controversial (Nolan and Soar, 2008). There are still no studies that show superiority for tracheal intubation or indeed any other airway device for use during cardiac arrest. Studies do however show that tracheal intubation attempts can be associated with prolonged interruptions in chest compressions and unrecognized oesophageal intubation (Nolan and Soar, 2008; Wang et al, 2009). The choice of airway device should therefore be based on the skills and experience of the rescuer.
The use of supraglottic airway devices (e.g. laryngeal mask airway) should be encouraged for rescuers who do not regularly perform tracheal intubation.
One important part of the new guidelines is the recommendation to use waveform capnography in additional to clinical signs to confirm tracheal tube placement and ventilations during cardiac arrest. This will have both cost and training implications. Waveform capnography gives a carbon dioxide trace as long as chest compressions are effective and blood flows through the lungs. If the waveform is completely flat during CPR in an individual who has recently suffered cardiac arrest, there is a high likelihood that the tracheal tube is misplaced. Also a sudden increase in end-tidal carbon dioxide during CPR may indicate ROSC (Pokorna et al, 2010).
Use and timing of drugs
Another controversial area is the use and timing of drugs in cardiac arrest. A recent Norwegian study that compared drug use with no drug use during advanced life support for out-of-hospital cardiac arrest failed to show a benefit for drug use (Olasveengen et al, 2009).
The PACA (placebo vs adrenaline in cardiac arrest) study from Australia (presented at the American Heart Association Resuscitation Science Symposium, Chicago, USA in November 2010) did however show improved ROSC rates with adrenaline use during out-of-hospital cardiac arrest. We must await the publication of the full study before coming to any detailed conclusions but these preliminary data seem to confirm that adrenaline increases rates of ROSC regardless of rhythm.
Adrenaline remains in the new guidelines but atropine and the use of the tracheal route for drugs is no longer included. If rapid intravenous access cannot be achieved, the intra-osseous route should be used. The use of adrenaline has been uncoupled from shock delivery during VF/VT arrest. For VF/VT the first dose of adrenaline is now given during CPR after the third shock. Amiodarone is also recommended during CPR after the third shock.
Termination of resuscitation rules
An area of care that requires further research is the use of termination of resuscitation rules by paramedics for victims who fail to respond to advanced life support measures. Although rules are available, these have not researched and validated in UK prehospital systems. For example, a North American decision-rule shows that resuscitation can be terminated at the scene by defibrillation-only emergency medical technicians, if the victim never has a shockable rhythm, the arrest is unwitnessed by the medical technicians and there is no ROSC at scene (Morrison et al, 2008). No such rules have been validated in the UK and existing Joint Royal Colleges Ambulance Liaison Committee (JRCALC) guidance should be used.
Post-cardiac arrest care
There are several important recommendations in the new guidelines for post-cardiac arrest care once ROSC is achieved. Many of these interventions can be started at the scene or during transport. One important new recommendation is the use of pulse oximetry to guide oxygen therapy after ROSC.
The use of 100% inspired oxygen is recommended during CPR but after ROSC the inspired oxygen concentration should be adjusted so the patient has an oxygen saturation of between 94–98%.
Both animal and human data suggest that high levels of oxygen in the blood (hyperoxaemia) as well as hypoxaemia after ROSC may be harmful (Kilgannon et al, 2010).
This may be challenging to implement out-of-hospital as many transport ventilators do not allow fine tuning of inspired oxygen concentration.
Therapeutic hypothermia for comatose patients after ROSC can be started out-of-hospital. A number of cooling techniques are available (e.g. cold intravenous fluid bolus, ice-packs, surface cooling devices, nasal cooling device) and the method used will depend on local factors.
Cardiac arrest victims with ROSC at scene should ideally be taken to a hospital that offers a comprehensive package of post cardiac arrest care that includes therapeutic hypothermia and percutaneous coronary intervention in order to improve outcomes (Soar and Packham, 2010). This includes bypassing closer hospitals if necessary. These systems already exist for other emergencies such as myocardial infarction, stroke and trauma and further work is needed to develop such systems of care for out-of-hospital cardiac arrest patients.
‘There are several important recommendations in the new guidelines for post-cardiac arrest care once ROSC is achieved’
Medical devices
A number of medical devices were discussed as part of the Guidelines 2010 process. These include prompt and feedback devices to improve chest compression quality, mechanical chest compression devices, the impedance threshold device (ITD) and the use of ultrasound to identify reversible causes of cardiac arrest. Although the use of these devices can be considered for certain circumstances, there were no recommendations for their routine use. Indeed a recent large study has shown no survival benefit from feedback devices for out-of-hospital cardiac arrest (Hostler et al, 2011). There is also little evidence supporting the use of mechanical chest compression devices and no recommendation for their routine use was made. A large study of the Autopulse has just been completed (Lerner et al, 2011). Although the results have not been formally published, the trial sponsor and manufacturer Zoll has made a statement that the Autopulse was equivalent to manual CPR (Zoll, 2011). There is also a large ongoing study of the LUCAS chest compression device (Perkins et al, 2010). The RESQ trial compared standard CPR with a combination of active compression-decompression (ACD) CPR and the ITD for outof-hospital cardiac arrest (Aufderheide et al, 2011). The ACD/ITD group had improved survival to both hospital discharge and at 90 days. Recent studies show that ultrasound scanning and echocardiography can be used by experienced operators to identify reversible causes of cardiac arrest (e.g. cardiac tamponade) in the out-of-hospital setting (Breitkreutz et al, 2010).
Conclusion
Finally, implementation of new guidelines and research findings can take some time (Berdowski et al, 2009). Several of the interventions recommended in Guidelines 2010 have already been in use in parts of the world and indeed by some ambulance services in the UK. One way of monitoring implementation and measuring outcomes is by having a national audit or registry. This would allow ambulance services to monitor their own outcomes and also benchmark against other organizations.
Such national registries already exist in other countries. For example, in North America, the resuscitation Outcomes Consortium (ROC) measures out-of-hospital cardiac arrest outcomes and supports clinical trials. Recent ROC data shows a wide variation in survival rates for out-of hospital cardiac arrest between different parts of North America (Nichol et al, 2008).
In the UK, the Resuscitation Council (UK) in collaboration with the Intensive Care National Audit and Research Centre (ICNARC) has just set up the National Cardiac Arrest Audit for in-hospital arrests. It is our view that a similar system would be beneficial to ensure good quality data and outcome measurement for outof-hospital cardiac arrests.
One challenge will be the need to collect accurate outcome data as the patients move between different healthcare settings. Improved measurement of resuscitation performance should improve delivery of care and outcomes for those who suffer out-of-hospital cardiac arrest.