A flowchart for the initial evaluation of the collapsed patient is shown in Figure 1.1.1. It includes checking for danger, assessing responsiveness, then opening the airway, giving breaths and cardiac compressions, and attaching an automated defibrillator as soon as possible. This is known as the ‘DR ABCD’ approach. CPR is continued until qualified personnel arrive or signs of life return.⁶

Fig. 1.1.1 Basic life support (BLS) flowchart algorithm.

The process commences with the recognition that a patient has collapsed and is unresponsive. The initial steps are as follows.

Check for dangers

As the patient is approached, the bystander should immediately consider any dangers that may be associated with the collapse of the patient. For example, the patient may have been electrocuted and there could be injuries to bystanders if the power source is not switched off prior to patient contact.

There may be a significant danger from collision with a passing vehicle in the case of a motor-vehicle accident where a patient is unconscious, as well as the potential risk of fire. Therefore, unless they are trapped, unconscious patients should be carefully removed from the vehicle prior to the arrival of emergency medical services, taking care to minimize movement of the neck unless they are trapped. It is considered that the risk of injury from fire or explosion exceeds the risk of moving an unconscious patient prior to immobilization of the cervical spine with a neck collar.

In the case of a patient who has collapsed in a confined space, the possibility of poisoning with a toxic gas such as carbon monoxide should be considered. Do not enter the scene until it can be made safe by emergency services, usually the fire brigade.

Finally, in current times of potential terrorist attack, if multiple victims are present, consider the possibility of the use of a chemical agent such as an organophosphate causing collapse and cardiac arrest. In this setting bystanders should immediately leave the area and await the arrival of EMS and a specialist hazardous agent team.

Check for response

The patient who has collapsed must be rapidly assessed to determine whether there is unconsciousness, indicating possible cardiac arrest. This is assessed by a gentle ‘shake and shout’ and observation of the patient’s response.

Suspect cardiac arrest if the patient is unresponsive to the ‘shake and shout’, and immediately telephone the emergency medical services (‘call first’). Alternatively, if the collapse is due to suspected airway obstruction (choking) or inadequate ventilation (drowning, hanging etc.), then commence resuscitation focusing on the airway for approximately 1 minute before calling the emergency medical services (‘call fast’).

Airway and breathing

Make an assessment of the airway and breathing if a patient has collapsed and is apparently unconscious.^3,⁴ Place the patient supine, check the airway by visual inspection, and open the airway with a head-tilt and/or a chin-lift manoeuvre.

Adequate respiration is assessed by visually inspecting the movement of the chest wall and listening for upper airway sounds. Occasional deep (agonal) respirations may continue for some minutes after the initial collapse in cases of cardiac arrest. These respirations are often mistaken for adequate breathing by untrained bystanders.

Cardiopulmonary resuscitation (CPR) will be required if the patient is found to have inadequate or absent breathing on initial assessment. On the other hand, when the initial assessment of an unconscious patient reveals adequate respiration, turn the victim on his/her side and maintain in the semi-prone recovery position. Make constant checks to ensure continued respiration while awaiting the arrival of the EMS.

Circulation

It was traditionally recommended that a bystander should attempt to palpate a pulse in order to diagnose cardiac arrest and, if absent, commence external cardiac compressions (ECC). It is now currently recommended that untrained bystanders do not attempt to palpate for a pulse,⁵ as there is good evidence that the pulse check is inaccurate in this setting.⁷ Therefore, cardiac arrest may instead be presumed if breathing is absent, and is highly likely if breathing is inadequate.

Management

Airway obstruction

Make a careful sweep with a finger if inspection of the airway reveals visible foreign material or vomitus in the upper airway. Take particular care not to be bitten, not to cause pharyngeal trauma, and not to propel material down into the lower airway.

There are a number of manoeuvres proposed to clear the airway if it is completely obstructed by a foreign body. In many countries abdominal thrusts (the Heimlich manoeuvre) are endorsed as the technique of choice. However, this technique is associated with potential complications such as intra-abdominal injury. In Australia the recommended techniques for clearing an airway that is obstructed by a foreign body are back blows and/or chest thrusts. As there is insufficient evidence to recommend one treatment over another, it is recommended that each be tried in succession until the obstruction is relieved.

Cardiopulmonary resuscitation (CPR)

The bystander should immediately commence cardiopulmonary resuscitation (CPR) if cardiac arrest is diagnosed and the EMS has been summoned, using both expired air resuscitation (EAR) and ECC until a defibrillator arrives.⁶

Expired air resuscitation (EAR) or ‘rescue breathing’

Since the first description in 1958, EAR has become the standard in BLS for patients who have absent or inadequate respirations. It is now more often referred to as ‘rescue breathing’. Two breaths should be delivered initially, followed by chest compressions (see later). Subsequently, deliver two breaths for every 30 chest compressions. However, there is often considerable reluctance by bystanders to perform EAR owing to the perceived difficulty of the procedure, the possibility of cross-infection and its disagreeable aesthetics.

Bystander ECC without EAR

Animal models show that some ventilation occurs during chest compressions, and it has been proposed that EAR may be withheld in adult patients who have a witnessed out-of-hospital cardiac arrest. A recent Japanese observational study (SOS-KANTO) compared the outcome of adult patients with a witnessed out-of-hospital cardiac arrest who received ECC only by bystanders with that of patients who received both EAR and ECC ‘conventional CPR’, as well as patients who received no bystander CPR.⁸ There was a favourable neurological outcome in 6.2% of patients who received ECC only, compared to a 3.1% favourable neurological outcome in the patients who received EAR plus ECC (P = 0.0195). Only 2.2% of patients who received no bystander CPR had a favourable neurological outcome. Therefore, a strong case may be made that bystanders perform only ECC and not EAR.⁹ However, this recommendation has not currently been endorsed by the Australian Resuscitation Council (ARC).

Simple airway adjuncts in medical facilities

Simple airway equipment may be used as an alternative to EAR when cardiac arrest occurs in a medical facility, such as mouth-to-mask ventilation and bag/valve/mask ventilation, with or without an oropharyngeal Guedel airway. This equipment has the advantage that there is often familiarity and no risk of cross-infection, although prior training in the use of these devices is required.

Whatever technique of assisted ventilation is used, an adequate tidal volume is assessed by the rise of the victim’s chest, and by listening and feeling for air being exhaled from the patient’s mouth. Also observe whether there is any distension of the stomach. Cease chest compressions briefly to allow ventilation in the absence of an advanced airway device such as an endotracheal tube.

The use of supplemental oxygen is increasingly considered part of BLS airway and breathing management. Although there are few data on outcome, it is intuitive that supplemental oxygen during CPR would increase the oxygen content of the blood and hence oxygen delivery to the brain and heart.

External cardiac compressions (ECC)

Place the patient supine on a firm surface such as a backboard, firm mattress or even the floor to optimize the effectiveness of chest compressions. Perform compressions that allow equal time for the compression and relaxation phases, with compression being approximately 50% of the cycle. Depress the lower sternum at least 4–5 cm in the adult, with complete recoil of the chest after each compression. Perform ECC at a rate of 100 compressions per minute, to ensure the delivery of a minimum of about 80 compressions per minute when accounting for the period spent on ventilations.⁵ Recommendations are essentially to ‘push hard, push fast, allow complete release and minimize interruptions’.

‘Thoracic pump’ mechanism

There is still debate as to whether ECC generates blood flow via a ‘cardiac pump’ mechanism or a ‘thoracic pump’ mechanism. The thoracic pump theory is supported by transthoracic echocardiography performed during CPR demonstrating that the cardiac valves remain open during the relaxation phase of ECC. Also, forceful coughing during CPR has been observed to result in sufficient blood flow to maintain consciousness. The changes in intrathoracic pressure are presumed to lead to forward blood flow, with valves in the venous system preventing back flow.

‘Cardiac pump’ mechanism

However, more recent studies of transoesophageal echocardiography during ECC in humans found that during the compression phase the left ventricle is compressed, the mitral valve remains closed, and the aortic valve opens only at the end of compression. During the relaxation phase the mitral valve opens and the left ventricle fills. These findings suggest that blood flows during ECC as a result of cardiac compression.

Whatever the predominant mechanism of blood flow, ECC results in only about 20% of cardiac output in the adult, mainly owing to the relative rigidity of the chest wall. Consequently, there is a progressive metabolic acidosis due to inadequate oxygen delivery during CPR. Few adults survive a cardiac arrest when ECC has been given for more than 30 minutes. Thus, most EMS allow paramedics to cease resuscitation if a patient in cardiac arrest has failed to respond to CPR and advanced life support measures after 30 minutes, provided there are no extraordinary circumstances such as hypothermia or drug overdose. See also Ch. 1.2on Advanced Life Support.

Defibrillation

Semi-automatic external defibrillation (SAED)

The semi-automatic external defibrillation (SAED) is now considered part of BLS. SAED devices are extremely accurate in diagnosing ventricular fibrillation or ventricular tachycardia, and are relatively simple for bystanders to use with minimal training. After switching the device on and applying the pads, the SAED will request confirmation of coma and absent respirations, and advise the bystander to ‘stand clear’. The bystander is then advised to manually press a button to deliver a shock.

Most SAEDs have an algorithm that initially requests the delivery of three countershocks if ventricular fibrillation persists. As the recent ILCOR guidelines now recommend a single shock followed by 1 minute of CPR (except when using a manual defibrillator at a witnessed arrest), it is expected that SAEDs will progressively have their electronics upgraded to follow the new recommendations.²

Non-medical personnel and the SAED

Other first responders

A range of situations is proposed where non-medical personnel might use a SAED. Thus, the SAED may be used by first responders such as fire services, who co-respond with ambulance services. In Canada, the state of Ontario implemented an extensive programme to introduce rapid defibrillation across the state.¹⁰ The use of fire department first responders resulted in 92.5% of cardiac arrest patients being defibrillated in under 8 minutes, compared to 76.7% under the previous system (P<0.001). Survival to hospital discharge improved from 3.9% (183/4690 patients) to 5.2% (85/1614 patients) (P = 0.03). This study demonstrates that an inexpensive, multifaceted, optimized systems approach to rapid defibrillation can lead to significant improvements in survival after cardiac arrest.

A study of a fire-service first-responder programme in Melbourne, Australia, found that the time to defibrillation was reduced from a mean of 7.1 minutes for ambulance services to 6.0 minutes for a combined approach.¹¹ However, this study was not powered to assess the impact on patient outcome.

Public area SAED

Alternatively, the SAED may be placed in a public area for use by designated personnel, such as security staff who undergo a short training programme. This approach has been shown to be effective in places with large at-risk populations, such as casinos.¹²

Public-access SAED

The SAED may be placed in a public area for use by personnel with no previous training at all in their use. At Chicago airport defibrillators were placed in strategic locations, with signs advising on their correct use.¹³ Over a 2-year period there were 21 patients with cardiac arrest, of whom 18 had an initial rhythm of ventricular fibrillation. A defibrillator was applied by a ‘good Samaritan’ bystander in 14 of these 18 patients and 11 were successfully resuscitated. Ten patients were alive and well 1 year later.

Shopping centres and apartment buildings

In a larger study,¹⁴ SAEDs were placed in 993 sites such as shopping centres and apartment buildings. More patients survived to hospital discharge when the units were assigned to volunteers trained in CPR plus using an AED (30 survivors among 128 arrests) than when the units were assigned to have volunteers trained in CPR only (15 among 107; P = 0.03). However, as most cardiac arrests occur at home or when ‘out and about’, the widespread implementation of this approach to all public areas would be costly and result in relatively few lives saved.¹⁵

Home SAED

Finally, a SAED may be placed in the home of a patient who is at increased risk of sudden cardiac arrest, for use by a relative who might witness the event. However, a recent study that enrolled 7001 patients concluded that survival rates from sudden cardiac arrest at home were not increased when a defibrillator was available in the home. ¹⁶

Implantable defibrillator insertion

Clearly, patients at highest immediate risk of unexpected cardiac arrest should have an implantable defibrillator inserted. Although most patients with an implanted defibrillator remain conscious during defibrillation, CPR should be commenced if the patient fails to respond to the device’s countershocks and becomes comatose. In such cases, intermittent firing of the implanted defibrillator presents no additional risk to the bystanders or medical personnel.

BLS summary

Basic life support for a patient with sudden cardiac arrest has been described in terms of a ‘Chain of Survival’. This includes recognition of cardiac arrest, a call to emergency medical services, the performance of cardiopulmonary resuscitation and, when available, early defibrillation using a semi-automatic external defibrillator.

Changes to BLS

The main recent change to basic life support is the so-called DR ABCD approach: the performance of chest compressions at a rate of 100 per minute, with 30 compressions followed by two ventilations, or ‘30:2’, with no pause to determine the presence or absence of a pulse.¹⁶ The exceptions to this are resuscitation of the newborn (use a 3:1 ratio of 90 compressions and 30 inflations to achieve 120 ‘events’ per minute); and endotracheally intubated victims (use a ratio of 15:1 in adults and 15:2 in children). Also pulse checks and recovery checks are no longer performed, and CPR is only interrupted when signs of a return of spontaneous circulation are present.¹⁷

BLS controversies

• External cardiac compressions without expired air resuscitation/rescue breathing

• How external cardiac compressions cause blood to circulate

• The role of public access SAEDs, with or without first-responder training

References

1 Cummins RO, Ornato JP, Thies WH, Pepe PE. Improving survival from sudden cardiac arrest: The ‘chain of survival’ concept. A statement for health professionals from the advanced cardiac life-support subcommittee and the emergency cardiac care committee, American Heart Association. Circulation. 1991;83:1832-1847.

2 International Liaison Committee on Resuscitation 2005. International consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. Resuscitation. 2005;67:181-341.

3 Australian Resuscitation Council. Airway: Australian Resuscitation Council Guideline 2006. Emergency Medicine Australasia. 2006;18:325-327.

4 Australian Resuscitation Council. Breathing: Australian Resuscitation Council Guideline 2006. Emergency Medicine Australasia. 2006;18:328-329.

5 Australian Resuscitation Council. Compressions: Australian Resuscitation Council Guideline 2006. Emergency Medicine Australasia. 2006;18:330-331.

6 Australian Resuscitation Council. Cardiopulmonary resuscitation: Australian Resuscitation Council Guideline 2006. Emergency Medicine Australasia. 2006;18:332-334.

7 Bahr J, Klingler H, Panzer W, et al. Skills of lay people in checking the carotid pulse. Resuscitation. 1997;35:23-26.

8 SOS-KANTO study group. Cardiopulmonary resuscitation by bystanders with chest compression only (SOS-KANTO): an observational study. Lancet. 2007;369:920-926.

9 Ewy GA. Cardiac arrest – guideline changes urgently needed. Lancet. 2007;369:882-884.

10 Stiell IG, Wells GA, Field BJ, et al. Improved out-of-hospital cardiac arrest survival through the inexpensive optimization of an existing defibrillation program. Journal of the American Medical Association. 1999;281:1175-1181.

11 Smith KL, McNeill JJ. Emergency Medical Response Steering Committee. Cardiac arrests treated by ambulance paramedics and fire fighters. Medical Journal of Australia. 2002;177:305-309.

12 Valenzuela T, Roe TJ, Nichol G, et al. Outcomes of rapid defibrillation by security officers after cardiac arrests in casinos. New England Journal of Medicine. 2000;343:1206-1209.

13 Caffrey SL, Willoughby PJ, Pepe PE, Becker LB. Public use of automated external defibrillators. New England Journal of Medicine. 2002;347:1242-1247.

14 Hallstrom AP, Ornato JP, Weisfeldt M, et al. Public-access defibrillation and survival after out-of-hospital cardiac arrest. New England Journal of Medicine. 2004;351:637-646.

15 Pell JP, Sirel JM, Marsden AK, et al. Potential impact of public access defibrillators on survival after out of hospital cardiopulmonary arrest: retrospective cohort study. British Medical Journal. 2002;325:515-520.

16 Bardy GH, Lee KL, Mark DB, et al. Home use of automated external defibrillators for sudden cardiac arrest. New England Journal of Medicine. 2008;358:1793-1804.

17 Wasserthiel J. Australian Resuscitation Guidelines: Applying the evidence and simplifying the process. Emergency Medicine Australasia. 2006;18:317-321.

1.2 Advanced life support

John E. Maguire

Introduction

The patient in cardiac arrest is the most time-critical medical crisis an emergency physician manages. The interventions of basic life support (BLS) and advanced life support (ALS) have the greatest probability of success when applied immediately, but become less effective with the passage of time, and after only a short interval without treatment are ineffectual.

Larsen et al., in 1993, calculated the time intervals from collapse to the initiation of BLS, defibrillation and other ALS treatments, and analysed their effect on survival from out-of-hospital cardiac arrest.³ When all three interventions were immediately available the survival rate was 67%. This figure declined by 2.3% per minute of delay to BLS, by a further 1.1% per minute of delay to defibrillation, and by 2.1% per minute to other ALS interventions. Without treatment, the decline in survival rate was the sum of the three coefficients, or 5.5% per minute.

Chain of survival

The importance of rapid treatment for cardiac arrest has led clinicians to develop a systems management approach, represented by the concept of the ‘Chain of Survival’, which has become the widely accepted model for the emergency medical services (EMS) systems.⁴ The Chain of Survival concept implies that more people survive sudden cardiac arrest when a cluster or sequence of events is set up as rapidly as possible. This Chain of Survival sequence includes:

• early access to the EMS system

• early BLS

• early defibrillation

• early advanced care.

All the links must be connected, as weakness in any link of the chain reduces the probability of patient survival. ALS involves the continuation of BLS as necessary, but with the addition of manual defibrillation, advanced invasive airway and vascular access techniques, and the administration of pharmacological agents.

Aetiology and incidence of cardiac arrest

Aetiology

The commonest cause of sudden cardiac arrest in adults is ischaemic heart disease.^1,^2,⁵ Other causes include respiratory failure, drug overdose, metabolic derangements, trauma, hypovolaemia, immersion and hypothermia.

Incidence

The population incidence of sudden cardiac death (within 24 hours of the onset of any symptoms) has been estimated as 1.24:1000/year in the USA.⁶ The incidence of cardiac arrest notified to ambulances in western metropolitan Melbourne, Australia, in 1995 was approximately 0.72:1000/year.⁷ From among 20 communities in developed nations worldwide a population average of 0.62:1000/year received attempted resuscitation after out-of-hospital cardiac arrest.⁶

Advanced life support guidelines and algorithms

The most exciting and clinically relevant advance in ALS over the last decade has been the development of widely accepted universal guidelines and algorithms including scientifically proven therapies that have substantially simplified the management of cardiac arrest.

International Liaison Committee on Resuscitation (ILCOR)

In 2000, the American Heart Association, in collaboration with the International Liaison Committee on Resuscitation (ILCOR), convened the International Guidelines 2000 Conference on CPR and Emergency Cardiac Care (ECC). This was the first international assembly gathered specifically to produce international resuscitation guidelines, where the International Guidelines 2000 for CPR and ECC were developed and then published.⁸ These guidelines represented a consensus of expert individuals and resuscitation councils and organizations across many countries, cultures and disciplines. The underlying principle guiding decision-making was that additions to existing guidelines had to pass a rigorous evidence-based review. Revisions or deletions occurred because of:

• lack of evidence to confirm effectiveness, and/or

• additional evidence to suggest harm or ineffectiveness, and/or

• evidence that superior therapies had become available.⁸

Researchers from the ILCOR member councils continued to apply and develop the above evidence evaluation process, which culminated in the publication in 2005 of the Consensus on Science and Treatment Recommendations (CoSTR).¹

Consensus on Science and Treatment Recommendations (CoSTR)

Each ILCOR member body has used the CoSTR documents to develop its own guidelines for local use. Thus in 2006 both the Australian Resuscitation Council (ARC)⁵ and the New Zealand Resuscitation Council (NZRC)⁹ published their local guidelines. The ARC guideline on Adult Advanced Life Support² includes an Adult Cardiorespiratory Arrest algorithm (Fig. 1.2.1). This is clear, concise, and easy to memorize and adapt into poster format, and is readily applied clinically.

Fig. 1.2.1 Algorithm for management of adult cardiorespiratory arrest.

(Reproduced with permission from the Australian Resuscitation Council.)

However, resuscitation knowledge is still incomplete, and some of the ALS techniques currently in use are not supported by the highest levels of scientific rigour. Thus strict adherence to any guidelines should be guided by common sense. Individuals with specialist knowledge may modify them according to the level of their expertise and the specific clinical situation or environment in which they practise.¹⁰

Initiation of ALS

The ARC guidelines and algorithm qualify the commencement of BLS with the statement ‘if appropriate’.² This is because BLS is only a temporary and inefficient substitute for normal cardiorespiratory function. ALS interventions are almost always necessary to produce the return of spontaneous circulation (ROSC).

Electrical defibrillation is the fundamental tenet of the treatment for VF and pulseless VT. However, the likelihood of defibrillation restoring a sustained, perfusing cardiac rhythm, and of a favourable long-term outcome, exists for as little as 90 seconds after the onset of cardiac arrest. The chances of survival to hospital discharge decline rapidly thereafter, as myocardial high-energy phosphate stores are consumed. Therefore, minimizing the time to defibrillation is the priority in resuscitation from sudden cardiac arrest. The purpose of BLS is to support the patient’s cardiorespiratory status as effectively as possible until equipment – particularly a defibrillator – and drugs become available.^1,²

The point of entry into the ALS algorithm depends on the circumstances of the cardiac arrest. In many situations, such as out-of-hospital cardiac arrest, BLS will already have been initiated and should be continued while the defibrillator/monitor is being prepared. Diagnosis must be swift and the defibrillator attached without delay when the patient is being monitored at the time of a cardiac arrest.^1,²

Attachment of the defibrillator/monitor and rhythm recogniton

Automated external defibrillator

Apply the self-adhesive pads in the standard anteroapical positions for defibrillation (see below) using an automated external defibrillator (AED). An internal microprocessor analyses the ECG signal and, if VF/VT are detected, it causes the AED to display a warning and then either deliver a shock (automatic) or advise the operator to do so (semi-automatic).^2,^11,¹²

Manual external defibrillator

The critical decision for the rescuer after applying the self-adhesive pads or paddles of a manual external defibrillator is whether or not the cardiac rhythm is VF/VT.^1,² Up to 70% of patients with an out-of-hospital cardiac arrest will be in VF/VT at the time of arrival of EMS personnel and a monitor/defibrillator.¹¹ The vast majority of cardiac arrest survivors come from this group.^1,^2,⁴

1 The ECG lead may be disconnected or broken. Look for the presence of electrical artefact waves on the monitor during external chest compression, indicating that the ECG leads are connected and intact. A perfectly straight line suggests lead disconnection or breakage.

2 Lead sensitivity may be inappropriate. Increase the sensitivity setting to maximum. The resulting increase in the size of electrical artefact will confirm that the sensitivity selection is functioning.

3 VF has a predominant axis. Even coarse VF may cause minimal undulation in the baseline if the axis is at right-angles to the selected monitor lead, and thus resemble asystole. Select at least two leads in succession before asystole is diagnosed, preferably leads at right-angles, such as II and aVL.

Defibrillation

The only proven effective treatment for VF and pulseless VT is electrical defibrillation.^1,^2,^10,¹² The defibrillator must be brought immediately to the side of the person in cardiac arrest and, if the rhythm is VF/VT, defibrillation attempted without delay.