Advanced life support - Clinical Tree

Essentials

1
Follow the Advanced Life Support (ALS) resuscitation guidelines developed by, or based on, those of the International Liaison Committee on Resuscitation (ILCOR).
2
Perform chest compressions without interruption for patients with no pulse, except when performing essential ALS interventions.
3
Deliver a shock to attempt defibrillation (150–200 joules [J] biphasic or 360 J monophasic) if the rhythm is either ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT).
4
Institute other ALS interventions as indicated.
5
Correct reversible causes of cardiac arrest―the ‘4 Hs and 4 Ts’.
6
Implement a comprehensive, structured post-resuscitation treatment protocol.

Introduction

A patient in cardiac arrest represents the most time-critical medical crisis an emergency physician manages. The interventions of Basic Life Support (BLS) and Advanced Life Support (ALS) have the highest probability of success when applied immediately; they 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 after out-of-hospital cardiac arrest. When all three interventions were immediately available, the survival rate was 67%. This figure declined by 2.3%/min of delay to BLS, by a further 1.1%/min of delay to defibrillation, and by 2.1%/min to other ALS interventions. Without treatment, the decline in survival rate is the sum of the three, or 5.5%/min.

Chain of Survival

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

Early access to EMS and cardiac arrest prevention
Early high-quality cardiopulmonary resuscitation (CPR)
Early defibrillation
Early advanced care and post-resuscitation care

All the links in the chain must connect, as weakness in any one reduces the probability of patient survival. ALS involves the continuation of BLS as necessary, but with the additional use basic or advanced airway devices, vascular access techniques, and the administration of pharmacological agents.

Aetiology and incidence of cardiac arrest

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

The incidence of out-of-hospital cardiac arrest (OHCA) recorded in Aus-ROC Epistry was 102.5 cases per 100,000 population. The crude incidence of OHCA in New Zealand was noted as 124 cases per 100,000 person-year. In both studies, 12% to 15% of cases with attempted resuscitation survived to hospital discharge or 30 days.

Advanced Life Support guidelines and algorithms

The most clinically relevant advance in ALS, over the last two decades has been the substantial simplification of the management of cardiac arrest by the development of widely accepted universal guidelines and algorithms that include evidence-based recommendations.

International Liaison Committee on Resuscitation

In Chapter 1.1 , Box 1.1.1 shows the national associations that formed the International Liaison Committee on Resuscitation (ILCOR) in 1993. The ILCOR group used to meet every 5 years to review the best available scientific literature and to publish the Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations (CoSTR). However, ILCOR realized the potential drawbacks of this approach in terms of delays in the implementation of new effective treatments. Since 2016, therefore, ILCOR has adopted the new procedure of publishing annual ILCOR CoSTR summary articles so as to provide a nearly continuous review of resuscitation science. The conference held in Dallas in February 2015 gave rise to the CoSTR documents published later that year.

Australasian guidelines and algorithms

Each ILCOR member body is expected to use the CoSTR documents to develop its own guidelines for local use. The Australian Resuscitation Council (ARC) and the New Zealand Resuscitation Council (NZRC) released joint Australasian guidelines in 2016; these are available at http://www.resus.org.au/policy/guidelines/ and http://www.nzrc.org.nz/guidelines/ respectively. The Australasian guidelines include an Adult Cardiorespiratory Arrest algorithm ( Fig. 1.2.1 ) that is clear, concise and easy to memorize and adapt into poster format. It is also readily applied clinically. This algorithm provides the framework used throughout this chapter to discuss ALS interventions.

Fig. 1.2.1, Algorithm for the management of adult cardiorespiratory arrest.

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

Initiation of Advanced Life Support

The purpose of BLS is to support the patient’s cardiorespiratory status as effectively as possible until equipment―particularly a defibrillator―and advanced treatment support become available. High-quality CPR remains the cornerstone of both BLS and ALS. The vast majority of cardiac arrest survivors have ventricular fibrillation (VF) as the primary rhythm, and electrical defibrillation is fundamental to the successful treatment for VF and pulseless ventricular tachycardia (VT). Therefore the likelihood of defibrillation restoring a sustained, perfusing cardiac rhythm and of a favourable long-term outcome greatly depends on good CPR and decreasing the time to defibrillation. The chances of survival to hospital discharge decline rapidly after as little as 90 seconds of cardiac arrest.

The point of entry into the ALS algorithm depends on the circumstances of the cardiac arrest. In situations where there are multiple rescuers, BLS should be initiated or continued while the defibrillator-monitor is being prepared. For a single rescuer who witnesses cardiac arrest in a setting where a defibrillator-monitor is readily available, it is a reasonable approach to obtain and attach the defibrillator immediately without commencing BLS. In all other cases, there is low-quality evidence suggesting that a brief period (1.5–3 minutes) of CPR before defibrillation may improve survival in patients where the cardiac arrest is unwitnessed or time to get a defibrillator is more than 4 to 5 minutes from arrest time.

Automated Chest Compression Devices

Load-distributing band and piston devices as well as the Lund University Cardiac Arrest System (LUCAS) are commonly used automated chest compression devices (ACCDs). Moderate-quality evidence has shown uncertainties regarding the benefits or harms of ACCDs over manual compressions. Therefore ILCORs suggest against the routine use of ACCDs to replace manual chest compressions. An ACCD can be used as an alternative where manual compressions are impractical or may compromise a provider’s safety, as in a moving ambulance, CPR in limited space or fewer personnel available for CPR.

Attachment of the defibrillator-monitor and rhythm recognition

Automated external defibrillator

Apply the self-adhesive pads in the standard anteroapical positions for defibrillation (see further on) when using an automated external defibrillator (AED). An internal microprocessor analyses the electrocardiographic (ECG) signal and, if VF/VT is detected, the AED displays a warning and then either delivers a shock (automatic) or advises the operator to do so (semiautomatic).

Manual external defibrillator

In manual defibrillation, after applying the self-adhesive pads or handheld paddles of an external defibrillator, the rescuer must determine whether or not the cardiac rhythm is VF/VT.

Rhythm recognition

Ventricular fibrillation

VF is a pulseless, chaotic, disorganized rhythm characterized by an undulating, irregular pattern that varies in amplitude and morphology, with a ventricular waveform of more than 150/min.

Pulseless ventricular tachycardia

Pulseless VT is characterized by broad, bizarrely shaped ventricular complexes associated with no detectable cardiac output. The rate is more than 100/min by definition and is usually in excess of 150.

Asystole

Asystole is identified by the absence of any electrical cardiac activity on the monitor. Occasionally it is incorrectly diagnosed (‘apparent asystole’) on the ECG monitor because

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.
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.
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 resembles asystole. Select at least two leads in succession before asystole is diagnosed, preferably leads at right angles, such as II and aVL.

Pulseless electrical activity/electromechanical dissociation

The absence of a detectable cardiac output in the presence of a coordinated electrical rhythm is called pulseless electrical activity (PEA), also known as electromechanical dissociation (EMD). Use of an arterial line in place, monitoring of end-tidal carbon dioxide (ET co ₂ ) or point-of-care cardiac ultrasound can help to differentiate between a true PEA and a pseudo-PEA. In general PEA has a poor outcome compared with shockable rhythms and there is some evidence regarding true PEA having a worse outcome than pseudo-PEA. In an observational study of OHCA and patients with PEA, an electrical frequency of greater than 60/min compared with the frequency of less than 60/min showed better 30-day survival rate (22%) and good neurological outcome (in 15%) – comparable to with shockable cardiac arrest.

Defibrillation

The only proven effective treatment for VF and pulseless VT is early electrical defibrillation. The defibrillator must immediately be brought to the person in cardiac arrest and, if the rhythm is VF/VT, a shock must be delivered without delay.

Anteroapical pad or paddle position

There are two accepted positions for the defibrillation pads or paddles to optimize the delivery of current to the heart. The most common is the anteroapical position: one pad/paddle is placed to the right of the sternum just below the clavicle and the other is centred lateral to the normal cardiac apex in the anterior or midaxillary line (V5–6 position).

Anteroposterior pad or paddle position

An alternative is the anteroposterior position: the anterior pad/paddle is placed over the precordium or apex and the posterior pad/paddle is placed on the patient’s back to the left or right of the spine at the level of the lower scapula or even in the interscapular region.

Do not attempt defibrillation over ECG electrodes or medicated patches and avoid placing pads/paddles over significant breast tissue in females. Also, the pads/paddles should be placed at least 8 cm away from the module and pulse generator, if the patient has an implanted pacemaker or a cardioverter-defibrillator. Arrange to check the function of any pacemaker or cardioverter-defibrillator as soon as practicable after successful defibrillation.

Waveform and energy of shocks

Two main types of waveform are available from cardiac defibrillators.

Biphasic waveforms

All modern defibrillators use biphasic waveforms with impedance compensation; this is now considered the ‘gold standard’. Biphasic (bidirectional) truncated transthoracic shock defibrillators are effective at lower energies and result in fewer ECG abnormalities after defibrillation.

Set the energy level at 150 to 200 J or follow the manufacturer’s advice if using a biphasic defibrillator in an adult with VF/pulseless VT cardiac arrest. For subsequent shocks, if the defibrillator is capable of increasing energy, it is reasonable to do so.

Monophasic sinusoidal waveform

Old defibrillators use a damped monophasic sinusoidal waveform, which is a single pulse lasting for 3 to 4 ms. Set the energy level at the maximum when using a monophasic defibrillator in adults, which is usually 360 J for all shockable rhythms in cardiac arrest.

Optimizing transthoracic impedance

A critical myocardial mass must be depolarized synchronously for defibrillation to be successful. This interrupts the fibrillation and allows recapture by a single pacemaker. The transthoracic impedance must be minimized for the greatest probability of success.

Reduction of transthoracic impedance

Use pads/paddles 10 to 13 cm in diameter for adults. Smaller paddles/pads allow too concentrated a discharge of energy, which may cause focal myocardial damage. Larger pads/paddles do not make good chest contact over their entire area and/or may allow current to be conducted through non-myocardial tissue.
Use conductive pads or electrode paste/gel. This reduces impedance by 30%. Take care to ensure that there is no electrical contact between the pads or paddles, either directly or through electrode paste, as this will result in current arcing across the chest wall.
Apply a pressure of 5 to 8 kg to the paddle when adhesive pads are not being used.
Perform defibrillation when the chest is deflated (i.e. in expiration).
However, routine use of impedance thoracic device in addition to conventional CPR is discouraged.

Current-based defibrillation

Conventional defibrillators are designed to deliver a specified amount of energy measured in joules. Depolarization of myocardial tissue is accomplished by the passage of electrical current through the heart; clinical studies have determined that the optimal current is 30 to 40 amps (A). The current delivered at a fixed energy is inversely related to the transthoracic impedance, so a standard energy dose of 200 J delivers about 30 A to the average patient.

Some newer current-based defibrillators automatically measure transthoracic impedance and then predict and adjust the energy delivered to avoid an inappropriately high or low transmyocardial current. These devices have defibrillation success rates comparable to those of conventional defibrillators while cumulatively delivering less energy. The reduced energy should result in less myocardial damage and may reduce post-defibrillation complications.

Automated external defibrillators

Automated external defibrillators (AEDs) were first introduced in 1979 and have become standard equipment in EMS systems for use outside hospital, as well as in many areas within hospital. EMS systems equipped with AEDs are able to deliver the first shock up to 1 minute faster than when a conventional defibrillator is used. Rates of survival to hospital discharge are equivalent to those achieved when more highly trained first responders use manual defibrillators.

The major advantage of AEDs over manual defibrillators is their simplicity, which reduces the time and expense of initial training and continuing education and increases the number of persons who can operate the device. Members of the public have been trained to use AEDs in a variety of community settings and have demonstrated that they can retain these skills for up to a year. Encouraging results have been produced when AEDs have been placed with community responders, such as firefighters, police officers, casino staff, security guards at large public assemblies, and public transport vehicle crews.

The Australasian College for Emergency Medicine recommends that all clinical staff in health care settings should have rapid access to an AED or a defibrillator with AED capability.

Delivering a shock

If the rhythm is assessed as shockable (VF or pulseless VT), the defibrillator should be charged while CPR continues. Then, after health care personnel are clear of the patient, a single shock is delivered. Following this shock, CPR should be recommenced immediately without any delay to assess or analyse either the pulse or the rhythm.

If the resuscitation team leader is uncertain whether the rhythm is shockable or non-shockable, no shock should be given.

Three stacked shocks

In 2010, the ILCOR recommended single-shock delivery for cardiac arrest patients with a shockable rhythm. Since 2010 no study has shown that any specific shock strategy is of benefit for survival, return of spontaneous circulation (ROSC) or recurrence of VF outcomes. However, keeping in mind the significance of minimal interruptions to chest compressions in improving survival outcomes, the 2015 CoSTR by ILCOR recommends single-shock delivery for all cases of cardiac arrest with shockable rhythm.

In a witnessed and monitored cardiac arrest with VF/VT, if the time to deliver shock is less than 20 seconds and time to rhythm check and recharge the defibrillator is less than 10 seconds, a sequence of up to three stacked shocks can be considered. This may be applicable to a patient who develops witnessed cardiac arrest while connected to a defibrillator with monitoring capability in a prehospital, emergency department (ED), critical care unit, coronary care unit or operation theatres.

Technical problems

Whenever attempted defibrillation is not accompanied by skeletal muscle contraction, take care to ensure good contact and that the defibrillator is turned on, charged up, develops sufficient power and is not in synchronized mode. The operational status of defibrillators should be checked regularly, and a standby machine should be available at all times. The majority of defibrillator problems are due to operator error or faulty care and maintenance.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here