Cardiac Arrest – the ALS algorithm and beyond

Authors: Samuel Jonathan Glover, James Raitt, Tim Wait, Rebekah Caseley / Editor: Swagat Mishra/ Codes: CC4, ResC8, RP1, RP3, RP5, SLO3 / Published: 10/10/2023

Disclaimer – always act within your own scope of practice and that of your institution.

The aim of this blog is to review management of adult medical cardiac arrests and look at interventions beyond the ALS algorithm.

Before going beyond the ALS algorithm, it would be negligent not to reinforce the absolute foundations of cardiac arrest management. There are four inescapable facts:

1. Preventing cardiac arrest is better than treating cardiac arrest
2. Early CPR, including bystander CPR in out-of-hospital cardiac arrest is of fundamental importance
3. Early defibrillation of shockable rhythms is paramount
4. After return of spontaneous circulation, high-quality post-resuscitation care gives the patient the best chance of achieving a good quality of life after cardiac arrest.

It can’t be reinforced enough that any additional interventions beyond the ALS algorithm must be in addition to the above rather than at the expense of it. First, we will ensure that each of the links of the chain of survival are being managed optimally.

Chain of survival section one: Preventing cardiac arrest

A large part of prevention of out of hospital cardiac arrests takes place in primary care, outpatient clinics and in inpatient wards, and is beyond the scope of this article.

Chain of Survival Section Two: Chest compressions

Again, starting with the fundamentals of ALS, chest compressions must be of high quality with minimal interruptions. Figure 2 demonstrates the effect of interruptions in CPR on coronary artery perfusion pressure¹.

The better the coronary perfusion pressure, the more likely the chance of Return Of Spontaneous Circulation (ROSC). There are various strategies to minimise “hands-off” time, such as pre-emptive palpation of pulses prior to stopping CPR for a rhythm check, such that if PEA is identified and there is no pulse CPR can be recommenced promptly. Some countries² advocate charging the defibrillator for every rhythm check and either delivering a shock or disarming the defibrillator depending on the rhythm so that there is only one pause in CPR to deliver a shock. The UK approach is two have two pauses; one to evaluate rhythm and a second only if required to provide defibrillation. Having this second pause means there are two “hands-off” pauses, but reduces the time between discontinuing CPR and delivery of a shock.

Mechanical chest compression devices, such as the LUCAS shown in figure 3, are commonly available to pre-hospital teams as well as in Emergency Departments.

Most of the potential benefits of a mechanical compression device are fairly apparent:

1. They don’t get tired
   • Anyone who has provided CPR knows how welcome it is for someone else to take over after your two minute cycle is complete. Alternating CPR providers every cycle can maintain effective chest compression for some time, but eventually CPR quality will deteriorate even despite this. The LUCAS has a battery life of 45 minutes and guarantees adequate force during this time.
2. They provide two additional pairs of hands
   • Manual CPR requires at least two staff members to alternate between cycles of compressions. Using a mechanical device frees up these two staff members to carry out other tasks. This is clearly of greater benefit in a smaller team compared to a situation with an excess of staff when a team-leader has more of a problem with crowd control.
3. They allow greater access to the patient
   • If one person is carrying out CPR and another is poised to take over, there is less space for other staff to carry out other activities around the trunk of the patient, such as securing IV access, administering drugs or carrying out ultrasound.
4. Shocks can be delivered during mechanical chest compression, which has two effects:
   • As figure 2 shows, perfusion pressure drops precipitously the moment CPR is discontinued. Delivering a shock while mechanical chest compression is ongoing ensures that there is optimum perfusion pressure at the moment of defibrillation. Theoretically, this increases the probability of successful defibrillation.
   • There is now only one pause in CPR (for the rhythm check) rather than two (the rhythm check and the delivery of a shock). This reduces “hands-off” time, reducing time that the brain and heart are not being perfused.

The potential downsides of mechanical compression devices are sometimes less apparent:

1. They interrupt CPR
   • To get a mechanical compression device started, CPR must be discontinued. A board is placed underneath the patient at the level of the lower half of the sternum before the device is clipped to either side of the board. Each of these steps result in either the complete cessation of CPR, or a reduction in the quality of CPR while they are being carried out. That said, a team that is familiar with the device can carry this out during a rhythm check with minimal interruption to CPR. A suggested approach is:
2. They don’t guarantee good quality CPR
   • A mechanical device can be misplaced, either too far up the chest, too low down or off the midline. This may go unnoticed by a team who are not familiar with the device. Even if the team-leader recognises the error, it does take more time to troubleshoot compared to a team-leader noticing that manual compressions are not in the correct site.

This video³ shows a good coordinated approach of lifting the patient up and sliding the LUCAS.

So, where do we stand on mechanical chest compression devices? A meta-analysis⁴ did not demonstrate any improvement in rates of ROSC, survival or survival with good neurological outcomes. The UK Resus council guidelines⁵ suggest “Consider mechanical chest compressions only if high-quality manual chest compression is not practical or compromises provider safety.”

As such, the decision to use them and the timing of their use should be on a case-by-case basis. If they are used, the following recommendations should be considered:

1. The chain of survival should be kept in mind when deciding on their use. Examples of critical interventions include application of defibrillation pads or treating a reversible cause of cardiac arrest such as decompression of a tension pneumothorax. Critical interventions should generally be prioritised ahead of applying a mechanical chest compression device.
2. A team which might use them should be familiar with their use
   • While they’re designed to be user-friendly, familiarity with them will ensure they can be applied in a timely fashion to the correct part of the chest, as well as early recognition of misplaced devices.
3. Broadly speaking, it is generally appropriate for the first couple of cycles of CPR to be manual before considering applying a device.

If electing to use a mechanical compression device, the disadvantages of the device can be mitigated with the suggested approach below:

• Prior to a rhythm check, ensure the device is prepared and has adequate charge
• Brief the team as to the plan and allocate roles
• At a rhythm check, have two staff members cross the patient’s arms over their chest and lift them forward
• Have another staff member position the back board appropriately
• Lower the patient on to the back board
• Have the members of staff who lifted the patient clip the device into place
• Commence mechanical CPR and ensure that the device is correctly positioned and delivering effective compressions.

Chain of survival section three: Defibrillation

The RCEM Learning podcast has discussed studies looking at optimal pad placement for transcutaneous pacing⁶ and for cardioverting atrial fibrillation⁷, but there appears to be equipoise between antero-lateral (figure 4) and the antero-posterior (figure 5) positions for defibrillation in shockable rhythms of cardiac arrest⁸.

Clearly, the antero-lateral position is going to be easier to apply without interrupting high-quality CPR. As such it is the most commonly used position for the initial rhythm check.

When applying pads, the vector of the current transmitted between the pads should be considered, and ensured that it passes through the heart. A common pitfall in the antero-lateral position is to apply the lateral pad too far anteriorly, resulting in the majority of the current not reaching the myocardium. Regardless of whether an antero-lateral or antero-posterior position is chosen, always ensure that a line drawn between the centre of the two pads (the vector) will go through the heart.

So, you’ve provided high quality ALS, recognised a shockable rhythm, delivered shocks through appropriately-placed pads with minimum interruptions to high-quality CPR and given adrenaline and amiodarone after the third shock. Your life support couldn’t have been any better…but the VF persists. Now what?

Dual sequential defibrillation (DSD), or the delivery of simultaneous shocks through antero-lateral and antero-posterior pads, was previously advocated as having benefit in refractory shockable rhythms. However, a recent RCT⁹ has shown that there is similar benefit from simply switching from one position to the other, known as vector change defibrillation. A number of organisations including the Resus Council (UK) recommend using vector change defibrillation in cases of refractory shockable rhythms. Co-ordinating vector change defibrillation requires careful co-ordination of the team, similar to application of a mechanical chest compression device. Application of the posterior pad is best carried out during a rhythm check, with one staff member required to placing the pad on the posterior chest wall and other staff members required to lift the patient forward.

If vector change is unsuccessful, it is controversial as to whether to attempt DSD. Arguments against DSD include:

• The UK Resus Council are quite explicit in advising “Do not use dual (double) sequential defibrillation for refractory VF outside of a research setting”⁵
• Defibrillators are not designed for DSD, and simultaneous shocks risk damaging the equipment
• A second defibrillator is required, which can distract from other resuscitation efforts.

Despite this, if all else (including vector change) has failed, some experts advocate attempting DSD in selected patients.

Chain of survival section four: Post-resuscitation care

Unfortunately, if ROSC is achieved there is no time for a celebratory lap of honour. Cardiac arrest with subsequent ROSC represents a global ischaemia-reperfusion insult which is superimposed on the original cause of the cardiac arrest. The resulting clinical picture is known as the post-cardiac arrest syndrome, and consists of four key elements:

1. Hypoxic brain injury
2. Post-arrest myocardial dysfunction
3. The systemic inflammatory response (with resulting vasoplegia)
4. Persistence of precipitating pathology

In the early stages of ROSC, careful attention should be paid to the primary survey.

Airway

• A definitive airway may be required, but if adequate oxygenation and ventilation is being provided without one then this is not the immediate priority

Breathing

• Initially, provide high flow oxygen.
• Once reliable oxygen saturation monitoring or arterial blood gases are available, this can be titrated down to target SpO2 94-98% or PaO2 10-13kPa to avoid the harmful effects of hyperoxia.
• End-tidal CO2 measurements should be monitored and normocapnoea targeted.
• Respiratory causes of cardiac arrest should be sought and addressed
• Rib fractures are not uncommon following CPR, and underlying pneumothorax should be considered. This is particularly important due to the risk of evolving tension pneumothorax under positive pressure ventilation.

Circulation

• A mean arterial pressure of ≥65mmHg is a reasonable initial target.
• Invasive arterial blood pressure monitoring may help to guide management.
• If invasive blood pressure monitoring is not available, non-invasive blood pressure should be measured frequently, with an automated NIBP cycle every 2-3 minutes.
• Haemodynamic management should be approached thoughtfully according to the clinical picture. Hypovolaemia is frequently present, either pre-existing or as a result of an evolving systemic inflammatory response, however this should not be assumed. Inopressor support is frequently required.
• A 12-lead ECG should be acquired, and an echocardiogram as soon as practicable.

Disability

• In post arrest patients who are immediately awake sedation is not required, but in patients requiring ongoing sedative infusion, short-acting agents such as propofol are favoured to aid neurological assessment.
• Seizures should be treated aggressively to prevent secondary neuronal injury
• Normoglycaemia should be maintained
• Therapeutic hypothermia has been replaced with targeted temperature management^11,12 favouring a normal temperature with avoidance of hyperthermia.

Beyond Advanced Life Support

The following are adjuncts to ALS and, as highlighted previously, should not get in the way of good quality ALS.

Airway management

A patent airway during CPR is clearly essential. The method through which a patent airway is achieved has not been shown to have any bearing on the efficacy of resuscitative efforts¹³. Whether a supraglottic airway or endotracheal tube is used should be assessed on a case-by-case basis, taking into account the likely cause of cardiac arrest and the skills of the team present. A supraglottic airway is much quicker to place and allows ALS to be established more efficiently. Guidelines suggest that endotracheal intubation should be reserved for teams or institutions with a high success rate for intubation¹⁴ (defined as >95% of intubations successful at first or second pass).

End-tidal CO₂ monitoring

This is advocated by the Resus Council to ensure that adequate ventilation is being achieved, as absent ETCO₂ trace suggests that ventilation is not successful (except in the case of monitoring failure).

In addition to confirming that ventilation is successful, higher readings of ETCO₂ are associated with higher probability of ROSC¹⁵, but lower values can be due to pulmonary embolism or poor quality CPR.

Ultrasound in cardiac arrest

This is covered in detail in another RCEMLearning module.

Advanced Invasive Strategies

Haemodynamic guided CPR

As previously emphasised, the key to improving survival in cardiac arrest is ensuring there is perfusion of the heart and the brain. In normal physiology, the heart perfuses in diastole. During ALS, the heart is perfused during the interval between compressions. Coronary perfusion pressure is calculated as diastolic blood pressure minus right atrial pressure. Higher coronary perfusion pressure during ALS has a strong association with likelihood of achieving ROSC¹⁶. From this, we can infer that raising a low diastolic blood pressure during ALS is likely to be beneficial.

Adrenaline improves diastolic blood pressure and therefore coronary perfusion pressure. However, at higher doses, adrenaline reduces cerebral perfusion. As such, some experts advocate for arterial line insertion during ALS in order to titrate doses of adrenaline to an individual patient. As ever, this should not come at the expense of the essential interventions (good quality CPR, early defibrillation and ensuring airway patency) but with sufficient pairs of skilled hands can be carried out in parallel with this. If an arterial line is to be sited during CPR, it makes sense to target a large vessel (the femoral artery) and be guided by ultrasound. Once in place, the arterial line will give moment-by-moment blood pressure monitoring, and an adrenaline infusion can be established and titrated to diastolic blood pressure targets. The optimum target is not known, but a diastolic blood pressure of 35mmHg has been advocated as a sensible target.

Additional benefits of an arterial line during advanced life support include:

1. Real-time feedback of CPR efficacy, with a low systolic blood pressure reading during chest compressions indicating and compressions are either of insufficient force or in an incorrect location
2. During rhythm checks, if organised electrical activity is seen on the monitor then an arterial line will give immediate feedback as to whether represents PEA or ROSC
3. Invasive BP monitoring allows for optimum post-resuscitation care from the moment ROSC is achieved.

Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA)

This involves accessing the femoral artery with a small inflatable balloon, as shown in figure 6.

In cardiac arrest, this balloon is typically inflated distal to the left subclavian artery and proximal to the coeliac trunk (zone 1). This has the effect of occluding arterial supply to the abdomen and lower limbs, increasing perfusion pressure to the myocardium and brain. It has been advocated in various circumstances:

1. Peri-arrest states due to subdiaphragmatic non-compressible haemorrhage, aiming to prevent cardiac arrest
2. As an alternative to resuscitative thoracotomy in PEA arrest due to subdiaphragmatic haemorrhage
3. In medical cardiac arrests, aiming to improve perfusion of the organs proximal to the occlusion (principally the heart and brain)¹⁷.

It is not currently advocated by the resus council and its use in cardiac arrest is largely confined to research studies – there are ongoing trials in Norway and the UK.

Veno-arterial Extracorporeal Membrane Oxygenation (VA-ECMO)

VA-ECMO is used on certain intensive care units for selected patients requiring mechanical circulatory support. It involves two large central cannulae; one for removing blood which is then pumped through an oxygenator and subsequently returned through the second catheter. In the context of cardiac arrest, it is commonly referred to as Extracorporeal CPR or E-CPR. In cardiac arrest, blood is generally taken from a catheter placed through the femoral vein and returned through a catheter in the femoral artery (as shown in figure 7). The main proposed benefit of this is maintaining cerebral and systemic oxygen delivery while the cause of cardiac arrest is being addressed. From a cardiac perspective, it can improve coronary perfusion pressure and cardiac oxygen delivery, but also increases afterload. ECMO can only be delivered in certain centres, so E-CPR can only be used if the local system allows it. It is generally reserved for patients who have a good chance of survival with good neurological outcome.

Evidence thus far has been mixed. One small RCT¹⁸ was stopped early after randomising only 19 patients due to evidence of benefit. A second RCT¹⁹ was stopped after 260 patients, with good neurological recovery in 32% of the e-CPR group compared to 22% of the control group. At face value these figures appear impressive, but a p-value of 0.09 led to the trial being terminated early in view of futility. A third RCT²⁰ showed greater probability of surviving to ICU admission in the e-CPR group, but no improvement in the primary endpoint of favourable neurological outcome at 30 days.  The success or failure of e-CPR depends on every step of the chain of survival, from bystander CPR to post-ROSC care. Of note, none of the studies were in the UK. There is a current trial looking at e-CPR for out-of-hospital cardiac arrest in the UK²¹.

Teamwork and leadership

There has rightly been a recent emphasis on teamwork, leadership and followership in Advanced Life Support courses, with evidence showing that teaching non-technical skills on ALS improves performance in a simulated setting²². While this is a large topic, the key areas in a cardiac arrest situation include:

• Allocating roles
  • The first step towards forming an effective team is identifying the team leader. This may have been identified beforehand, either at the start of the shift or upon receiving a pre-alert from pre-hospital teams that a cardiac arrest patient is imminently arriving.
  • If there isn’t a pre-determined leader then a leader should be established early and identified to the team. The team leader should remain “hands off” where possible and typically will assume a position at the foot of the bed.
  • Once cardiac arrest is confirmed, the first priority of the team leader is to ensure good quality CPR is initiated and defibrillation pads applied for a rhythm check as early as possible.
  • The team leader should allocate roles according to the experience of the team. These roles can change as the situation progresses or as more team members become available. For instance, anyone with ALS certification should be able to do basic airway techniques, but if someone with advanced airway skills arrives later then they could step in to manage the airway.
  • The team leader can also change during the cardiac arrest. This typically occurs for one of two reasons:
    • A more experienced team member arrives who is better suited to becoming team leader. If this is the case, a concise handover should be made and it should be made clear to the team who the new leader is.
    • The team leader is needed to carry out a task that nobody else in the team can carry out. For instance, if the team leader determines that point of care ultrasound would add benefit and is the only member of the team who can carry this out, they should recognise that taking on this task is likely to lead to them becoming task focused and losing situational awareness. As such, they could transiently delegate leadership to another member of staff while they perform this.
• Closed-loop communication
  • This is a three-step process of communication, summarised in figure 8, which ensures that all parties are aware that a message has been correctly received
    • Firstly, the person wishing to communicate information does so, ideally using the name of the person they are speaking to
      • “Richard, could you give 1mg intravenous adrenaline?”
    • Secondly, the recipient of the message confirms the information provided
      • “You want me to give 1mg intravenous adrenaline”
    • Thirdly, the initial person confirms that the message was received correctly, closing the loop
      • “Correct, thank you Richard”
  • On the face of it, closed-loop communication appears clunky, but it ensures that team members are on the same page and is far superior to a team leader simply announcing to the room “Can we give 1mg adrenaline, please?”
  • One closed loop can generate another. For instance, if the initial message was instead “Richard, could you give 1mg intravenous adrenaline and tell me when it’s given?” then after administering adrenaline Richard should open a second loop by telling the team leader it has been given.

• Stress management
  • Each member of the team might be at different levels of stress. This is often related to experience of similar situations in the past; a senior ED nurse is likely to be more comfortable in a cardiac arrest situation than a nurse who usually works in outpatients.
  • A team leader should conduct themselves in a way that aims to keep the rest of the team calm. Verbal communication should be clear and direct without being inflammatory. Team leaders should also be mindful of non-verbal communication, and ensure that they appear calm (at least outwardly!)
  • If, despite the team leader’s efforts, a team member is clearly distressed to the point of it having a negative impact on their performance, the team leader could either politely replace that team member with a less distressed colleague, or reallocate that team member to a less involved role.
• Sharing mental models
  • An effective team leader can process large amounts of information, some of which might not be available to all team members. For instance, somebody concentrating of securing IV access during a rhythm check might not be aware of what rhythm was identified.
  • At appropriate intervals, a team leader can summarise the situation to the team, for example “This 60 year old patient has been unwell for three days with vomiting on a background of chronic kidney disease. He has had one shock for VF and has not shown signs of life. His blood gas shows a potassium of 7.5. The likely cause of the arrest is hyperkalaemia, we’ve given calcium and Richard is drawing up insulin and dextrose. Does anyone else have any thoughts?”
  • Sharing a mental model has several effects
    • It ensures that all team members are aware of the relevant information
    • Can have a calming effect on the team, demonstrating that there is  team leader has a plan in place
    • It enables team members to make suggestions (“Should we think about giving some sodium bicarbonate?”)
• Cognitive offloading
  • Even the most experienced team leader will benefit from delegating tasks. In a large emergency department or trauma centre, there are generally enough (or too many?) willing assistants able to take on tasks. It is common to see staff members allocated roles such as scribe or timekeeper. However, in a smaller team this is not always possible. A variety of free Apps have been developed to assist in cognitive offloading, with the authors preferring tidyResus (available on the App Store) or iArrest (available on the Play Store). This keeps time and prompts for rhythm checks, and will logs rhythms, delivery of shocks and medications which can be documented in the patient notes at a convenient time.

Discontinuing resuscitation efforts

There is no one factor to guide when resuscitation should be discontinued. There are various causes of cardiac arrest where prolonged resuscitation efforts should be considered, such as hypothermia or toxicological causes of arrest. The case of Fabrice Muamba, a footballer who suffered a cardiac arrest while playing for Bolton Wanderers in 2013²³ and achieved ROSC and subsequent good neurological recovery after 78 minutes of CPR highlights the importance of the chain of survival and the possibility, in the right circumstances, of recovery with good neurological outcome after prolonged resuscitation.  Using the terms “no flow time” (no CPR delivered) and “low flow time” (CPR delivered), rather than the misleading term “downtime” gives a much more accurate picture of the cardiac arrest.

Factors which suggest the likelihood of successful resuscitation with good neurological outcome is less likely include:

• Premorbid factors
  • Increasing frailty
  • More comorbidities
• Resuscitation factors
  • Unwitnessed arrest
  • No bystander CPR
  • Non-shockable rhythm
  • No signs of life during CPR
  • Persistent cardiac arrest (in contrast to intermittent ROSC)

Summary

• Early effective CPR and early defibrillation remain the mainstay of treatment for cardiac arrest
• Efforts in addition to this should not compromise delivery of CPR and defibrillation
• If a shockable rhythm is refractory to shocks, change of pad position should be utilised
• Mechanical CPR can be considered, but has not been shown to be of benefit and is likely to be beneficial only in prolonged arrests or in teams with limited members of staff available.
• Post-resuscitation care should aim to maintain normal physiologic parameters and pre-empt haemodynamic deterioration due to the post cardiac arrest syndrome.
• Ultrasound is likely to be of value in skilled hands, but shouldn’t impair other efforts.
• REBOA and E-CPR are being studied and, depending on the outcomes of these studies, their use in cardiac arrest may become more common
• Discontinuing CPR should be a team decision and should not be as a result of one single factor.

Further information

• Cardiac Arrest Symposium Recording. Thames Valley Air Ambulance
• Cardiac Arrest Masterclass. The Resus Room.
• Cardiac Arrest in Special Circumstances: Anaphylaxis. RCEMLearning, 2020.
• Cardiac Arrest in Special Circumstances: Hypothermic Cardiac Arrest. RCEMLearning, 2018.

References

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2. Additional information page: ACT Ambulance Service C.O.A.C.H.E.D. cardiac arrest management method. May 2017.
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7. June 2022 podacst. RCEMLearning, 2022.
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17. Brede JR, Skulberg AK, et al. REBOARREST, resuscitative endovascular balloon occlusion of the aorta in non-traumatic out-of-hospital cardiac arrest: a study protocol for a randomised, parallel group, clinical multicentre trial. Trials 22, 511 (2021).
18. Yannopoulos D, Bartos J, et al. Advanced reperfusion strategies for patients with out-of-hospital cardiac arrest and refractory ventricular fibrillation (ARREST): a phase 2, single centrel, open-label, randomised controlled trial. Lancet. 2020 Dec; 396(10265):1807-1816.
19. Belohlavek J, Smalcova J, et al. Effect of Intra-arrest Transport, Extracorporeal Cardiopulmonary Resuscitation, and Immediate Invasive Assessment and Treatment on Functional Neurologic Outcome in Refractory Out-of-Hospital Cardiac Arrest: A Randomized Clinical Trial. JAMA. 2022 Feb 22;327(8):737-747.
20. Suverein MM, Thijs SR, et al. Early Extracorporeal CPR for Refractor Out-Of-Hospital Cardiac Arrest: The INCEPTION Trial. NEJM. 2023 Jan;388(4):299-309.
21. Harefield Hospital offers advanced CPR to out-of-hospital patients. BBC News [Internet]. 2023 Feb 21. [Accessed Sep 27 2023].
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23. Muamba discharged from hospital. BBC Sport [Internet]. [Accessed Sep 27 2023].