24 Resuscitation
After reading this chapter, you should be able to:
• identify the clinical assessment used to identify sudden cardiac arrest (SCA).
• outline the role of the chain of survival in the management of SCA.
• outline the management of common arrhythmias associated with SCA.
• describe the use of advanced airway adjuncts and indications for use in SCA.
• discuss indications, actions and routes of administration of medications used in advanced life support.
• describe the appropriate care of persons experiencing SCA including specific circumstances such as the pregnant woman, electrical injuries and drowning.
Introduction
The continuum of critical illness for an individual can span the period before and beyond hospital admission. Resuscitation is often required outside the critical care environment, and the ‘cardiac arrest’ team has evolved to use a more proactive, early-intervention approach, utilising a range of systems and instruments to detect deterioration in patients’ clinical status (see Chapter 3). It is well recognised that improved outcomes from cardiac arrest are dependent on early recognition and initiation of the ‘chain of survival’. This chapter introduces the resuscitation systems and processes in both the prehospital and the in-hospital settings. The chain of survival provides a framework for the management of the person experiencing cardiac arrest and resuscitation in specific circumstances. The chapter expands on the final link in the chain, advanced life support, to outline advanced airway management, rhythm recognition, administration of medications and post resuscitation care. Resuscitation involves many moral and ethical issues, such as family presence during resuscitation, deciding when to cease or initiate resuscitation, and near-death experiences.
Background
Coronary heart disease (CHD) is the leading cause of death in most industrialised countries, with over half of these being due to sudden cardiac arrest (SCA).1–3 Despite advances in CHD management, survival outcome figures from SCA remain poor.4–6 Survival after SCA is dependent on the presenting rhythm, early defibrillation, effective cardiopulmonary resuscitation and advanced life support.6 Because the presenting rhythm with the majority of witnessed SCAs is ventricular fibrillation, bystander cardiopulmonary resuscitation and early defibrillation are the major interventions influencing outcome after SCA.2,6–7 It is possible that the number of ventricular fibrillation/ventricular tachycardia (VF/VT) arrests is actually higher than reported, as often by the time the cardiac arrest team arrives the patient’s rhythm has deteriorated to asystole.8
Incidence/Aetiology of Cardiac Arrests
The prevalence of CHD varies worldwide, thus estimates of the incidence of SCA are difficult to obtain. In Australia, CHD is the leading cause of disease burden (9%) and accounts for 16.5% of all deaths.9,10 There are many factors that contribute to cardiac arrest. In adults, the most common cause of cardiac arrest is a primary cardiac event,11 with coronary artery disease accounting for up to 90% of all victims.12,13 CHD is the most likely cause of death in those over 35 years of age, compared to non-cardiac causes such as drowning, acute airway obstruction or trauma for people less than 35 years of age.13
While causes of cardiac arrest are numerous, most often it is associated with ventricular fibrillation triggered by an acutely ischaemic or infarcted myocardium or primary electrical disturbance.3 Causes of cardiac arrest may be separated into two categories, primary and secondary, as displayed in Table 24.1.
TABLE 24.1 Causes of cardiac arrest
| Primary causes | Secondary causes |
|---|---|
Acute myocardial infarction (AMI) is the most common precursor to cardiac arrest. In victims of trauma, drug overdose and drowning, the predominant cause of cardiac arrest is asphyxia. Cardiac arrest in children is rare and even more rarely sudden,14,15 with the common causes being trauma, congenital heart disease, long QT syndrome, drug overdose, hypoxia and hypothermia. The most common arrhythmia in infants is bradycardia, and the prognosis is especially poor if asystole is present.14,16
Pathophysiology
In sudden cardiac arrest with cardiac origin, it is believed that myocardial ischaemia leads to ventricular irritability and the progression from ventricular tachycardia to ventricular fibrillation (VF) and ultimately asystole.17 After the onset of VF (in animal studies), carotid arterial blood flow continues for approximately 4 minutes even in the absence of cardiac compressions, as coronary perfusion pressure (the pressure gradient between the aorta and the right atrium) falls over this period.17 This initial phase is characterised by minimal ischaemic injury, and it is during this time that defibrillation is most likely to result in the restoration of a perfusing rhythm, while initiation of effective cardiac compressions will increase the coronary perfusion pressure.17
Progression of the cardiac arrest beyond 4 minutes results in accumulation of toxic metabolites, depletion of high-energy phosphate stores, and the initiation of ischaemic cascades.17 A high probability of irreversible cellular injury exists where a cardiac arrest extends for longer than 10 minutes, and the return of a spontaneous circulation during this period may initiate a reperfusion injury17 (see Chapter 11 for further discussion).
Resuscitation Systems and Processes
Since the rediscovery of the effectiveness of closed-chest cardiopulmonary resuscitation (CPR) in 1960 and its subsequent widespread adoption, CPR has saved the lives of many, potentially ensuring years of productive life.18 As CPR quickly became one of the most widely-used and researched procedures, voluntary coordinating bodies developed throughout the world.13 Organisations such as the European Resuscitation Council (ERC), the American Heart Association (AHA), the New Zealand Resuscitation Council (NZRC), the Heart and Stroke Foundation of Canada, and the Southern African and Australian Resuscitation Councils (ARCs) established practice guidelines to improve standards in resuscitation, and coordinated resuscitation activities on a national basis.19,20 However, as standardised recording of outcome data did not exist, resuscitation endeavours could not be compared meaningfully between countries.19Consequently, the International Liaison Committee on Resuscitation (ILCOR) was formed in 1992 to promote global discussion and consistency of guidelines between these international resuscitation councils.19 The AHA, ARC, NZRC, ERC and ILCOR guidelines are subject to constant review and modification based on emerging scientific data. Guidelines and recommendations are classified according to scientific evidence. The most recent substantive guidelines from ILCOR were published in October 2010,20 with the ARC and NZRC guidelines published in January 2011. While it is recognised there are differences between the various councils, this chapter primarily reports on the ARC and NZRC recommendations.
Survival of OUT-Of-Hospital Arrests
Despite recent advances in resuscitation and technology, the survival rate for out-of-hospital cardiac arrest (OHCA) remains poor.6 Factors associated with higher rates of mortality for adults are: age over 80 years, unwitnessed arrest, delays before commencing CPR, defibrillation response times longer than 8 minutes, and non-ventricular tachycardia/fibrillation rhythm.21 The outcome statistics for children after OHCA are similarly poor.14 Marked differences in the inclusion criteria and outcome definitions may, however, also explain the wide variations in survival rates from cardiac arrests.21 In recognition of these variations, the Utstein guidelines were developed and implemented to consistently document, monitor and compare out-of-hospital cardiac arrests. These guidelines:
• establish uniform terms and definitions for out-of-hospital resuscitation
• establish a reporting template for resuscitation studies to ensure comparability
• define time points and time intervals relating to cardiac resuscitation
• define clinical items and outcomes that emergency medical systems should gather
Survival from in-Hospital Arrests
In-hospital resuscitation, as with OHCA, have survival rates of around 20%.22,23 Many factors such as age, presence or absence of morbidity before or during the hospital admission, absence of ‘not-for-resuscitation’ orders, asystole and non-ICU location contribute to the low in-hospital survival rates.24,25
Management
The overall aim of managing a patient in arrest is the prompt restoration of a spontaneous perfusing rhythm with minimal neurological dysfunction. It is well recognised that successful outcome from cardiac arrest is dependent on several key factors: (a) early recognition of cardiac arrest; (b) immediate effective CPR, (c) optimising response times, and (d) early defibrillation.26,27 The probability of an unsuccessful outcome grows with the length of time taken to restore spontaneous circulation.
Chain of Survival
To optimise a person’s chance of survival, the ‘chain of survival’ strategy has been developed,27 that represents the sequence of four events that must occur as quickly as possible: early recognition, early CPR, early defibrillation and postresuscitation care (see Figure 24.1). These time-sensitive, sequential actions must occur to optimise a cardiac arrest victim’s chances of survival. Communities with integrated links along this chain have demonstrated higher survival rates after OHCA than those with deficiencies in these links.2
Early Recognition of Cardiac Arrest
The chain of survival begins with early recognition of a medical emergency and the activation of the medical calling system.2,28 However, the chain of survival has not always been adequate when a cardiac arrest occurs in the hospital, from the point of view of early recognition, timeliness or availability of equipment or staff.24,25 The traditional cardiac arrest team responded to the seriously ill, but the patient was often not salvageable by the time the cardiac arrest team arrived. Two-thirds of in-hospital cardiac arrests are potentially avoidable, with up to 84% of all in-hospital cardiac arrests demonstrating evidence of deterioration in the 6 to 8 hours preceding the arrest.29,30 Consequently, in recent years there has been a move to implement rapid response teams (RRT) that facilitate the early recognition and rapid management of critically ill patients, for example the medical emergency team (MET), the patient-at-risk team (PART) and physiological track and trigger systems (TTS) such as the medical early-warning system (MEWS)31–33 (see Chapter 3 for further discussion). These teams replace the traditional cardiac arrest team by responding to a calling criteria based primarily on abnormal vital signs (see Table 24.2).
Early warning system calling criteria are widely displayed around the hospital and the RRT is activated in the same manner as the cardiac arrest team, ultimately resuscitating patients earlier.34 Recent reviews of the literature and meta-analyses show that in clinically unstable patients, early access – including early recognition and intervention by a MET/rapid response system – can reduce the incidence of cardiac arrests outside ICUs, however there are inconsistent findings regarding their impact on intensive care admission rates and lowering hospital mortality rates.35–37 To further facilitate earlier activation of the RRTs family and patients have been provided with a means to activate the team on a patient’s behalf.38
Basic Life Support
When a patient is identified as in potential or actual arrest, a primary and secondary survey should be conducted in the DRSABCD sequence:39
• Danger. Check for danger (hazards or risks or safety)
• Responsive. Check for response (if responsive/unconscious)
• Airway. Open the airway. Airway assessment is undertaken to establish a patent airway while maintaining cervical spine support (if injury is suspected)
• Breathing. Check breathing. Breathing includes the assessment and establishment of breathing, noting rate, pattern, chest movement and tissue oxygenation
• CPR. Start CPR. Give 30 chest compressions (almost two compressions/second) followed by two breaths.
• Defibrillation. Attach an automated external defibrillator as soon as available and follow its prompts.
Continue CPR until responsiveness and normal breathing return. Ideally, these interventions are performed simultaneously or in rapid sequence and will take no longer than 60–90 seconds to complete. This systematic approach correlates closely with the principles of basic life support (BLS), in that where a life-threatening abnormality is detected, immediate intervention is required before further assessment (see Figure 24.2).
Airway
Recognition of airway obstruction includes listening for inspiratory (stridor), expiratory or grunting noises. The work of breathing can be assessed by the respiratory rate, intercostals, subcostal or sternal recession, use of accessory muscles, tracheal tug or flaring of the alae nasi. Nasal flaring is especially evident in infants with respiratory distress. Noisy breathing is obstructed breathing, but the volume of the noise is not an indicator of the severity of respiratory failure. Should obstruction to air flow be detected, then the airway should be opened using three manoeuvres: the head-tilt, chin-lift and jaw thrust. The ARC recommends assessing a person’s airway without turning them onto the side unless the airway is obstructed with fluid (vomit or blood) or submersion injuries.39
The airway of the infant differs from that of the older child or adult in that the infant has a large head and tongue, small mouth, and the larynx is narrower, shorter, more anterior and acutely angled.17 The airway of an infant is also more cartilaginous and can be easily occluded when the neck is hyperextended; in addition, the large tongue can easily fall back to obstruct the pharynx.40 Hence, the head of an infant should be maintained in the neutral position, whereas a child aged 1–8 will require the ‘sniffing position’ with varying degrees according to age. The chin-lift and head-tilt manoeuvres may be used in children to obtain the appropriate amount of positioning for age. Jaw thrust may be used if head-tilt/chin-lift is contraindicated.40 Do not use the finger sweep to clear the airway of an infant, as this may result in damage to the delicate palatal tissues and cause bleeding, which can worsen the situation. Use of finger sweep can force foreign bodies further down into the airway.40 Suction is more useful for removing vomitus and secretions.
Breathing
To assess for the presence of breathing, look, listen and feel for breath sounds for no more than 10 seconds. If the person is unresponsive with absent or abnormal breathing, call for help and compressions should be commenced immediately. Agonal gasps are not to be considered as normal breathing. Typically, the arterial blood will remain saturated with oxygen for several minutes following the cardiac arrest and as cerebral and myocardial cell oxygenation is limited more by the absence of cardiac output as opposed to the reduced PaO2, effective compressions are more important than rescue breaths.27
CPR
Individuals should commence cardiac compressions if the victim is unconscious, unresponsive, not moving and not breathing normally. Where possible, change the person delivering the compressions every two minutes. Pulse check by lay rescuers and health professionals in BLS is not recommended. Assessment of effective chest compression by healthcare professionals may be made by continuous end tidal CO2 (ETCO2) monitoring. For CPR to be effective the patient should be flat, supine and on a firm surface. The chest should be compressed in the midline over the lower half of the sternum, which equates to the ‘centre of the chest’, at a depth of more than 5 cm (in adults) and at a rate of 100 compressions per minute for adults, infants and children, with the rate rising to 120/min for the newborn.27 CPR should be initiated when the heart rate is 60 beats/min for the neonate, infant and the small child and 40 beats/min for the large child. Performed correctly, external cardiac compressions (ECC) can produce a systolic blood pressure peak of 60–80 mmHg (in adults) and a cardiac output of 20–30% of normal.27,41 With external chest compressions it takes time to reach optimal levels of coronary perfusion pressure and, ultimately, bloodflow. Any interruption to chest compressions therefore decreases the coronary perfusion pressure and resultant blood flow, ultimately reducing survival.42 After 30 compressions open the airway and give two breaths.43
Survival potentially improves when an individual receives a higher number of chest compressions during CPR, even if the person receives fewer ventilations. Because of this, it is recommended that a 30 : 2 compression-to-ventilation ratio is used in adults, children and infants regardless of the number of rescuers, and 3 : 1 for neonates. Having noted this, in the advanced life support paediatric setting, the compression ratio changes to 15 : 2 and a ratio of 3 : 1 for the newborn with any number of rescuers (see Table 24.3). Studies note that the average person may not only be reluctant to initiate mouth-to-mouth resuscitation44 but will also take eight seconds to deliver one breath.45 When a rescuer is reluctant to perform rescue breaths, external cardiac compression (ECC) without expired air resuscitation (EAR) should be encouraged, as the generally held belief is that ECC alone is better than no CPR at all.46–48
Devices to augment compression
As ECC supplies only 30% of normal cardiac output49 and 15% of normal cerebral blood flow, there is a great need to find ways to improve ECC. While no circulatory adjunct is currently recommended, several are being routinely used in the preadmittance and in-hospital settings.20 A few of the recent devices are outlined in Table 24.4.
TABLE 24.4 Augment compression devices
| Device | Description |
|---|---|
| Active compression–decompression (ACD-CPR) | • utilises a small portable device to compress and decompress the chest (‘plunger method’) • enhances ventilation and venous return by raising the negative intrathoracic pressure139 which facilitates venous return, thus priming the heart for subsequent compressions. |
| Interposed abdominal compression combined (IAC) with CPR (IAC-CPR) | |
| Non-invasive automated chest compression device (AutoPulse) |
Given the limited available information on the outcome of any of these devices and the absence of evidence to demonstrate these devices are superior to conventional manual CPR, no device is currently recommended as a routine substitute for manual CPR.20
Defibrillation
While CPR has been associated with improved survival to discharge from hospital, it cannot be substituted for the definitive treatment of early defibrillation. It is thought that CPR will supply sufficient oxygen to the brain and heart until defibrillation is available. Ultimately, despite the most effective CPR, the single-most important cause of decreased prognosis in pulseless VT/VF cardiac arrests is a delay in electrical defibrillation.3
Praecordial thump
A praecordial thump is a single, sharp blow delivered with a clenched fist to the midsternum of a victim’s chest from a height of 25–30 cm above the sternum.7 The mechanical energy generated by the praecordial thump may generate a few joules, and therefore if applied within the first few seconds of onset of a shockable rhythm, but it has a very low success rate at converting VF/VT to a perfusing rhythm.50,51 Because of the very low success rate and the brief period for application, delivery of the thump must not delay accessing help or a defibrillator. Only situations where the VF arrest is witnessed and monitored and a defibrillator is not immediately on hand (i.e. critical care environments) would the delivery of the praecordial thump be appropriate.20
Electrical defibrillation
Defibrillation is the passage of a current of electricity through a fibrillating heart to simultaneously depolarise the mass of myocardial cells and allow them to repolarise uniformly to an organised electrical activity.52 There are two defibrillator modes for delivery of electrical energy: monophasic and biphasic waveforms. Monophasic defibrillators are no longer manufactured, however they are still available in clinical settings. Monophasic defibrillators operate by the current travelling in one direction from one paddle through the heart to the opposite paddle.52,53 In comparison, the biphasic defibrillator’s current travels in one direction through the heart for a predetermined time, then reverses.
There are two types of external defibrillators: the manual external defibrillator (MED), and the automatic external defibrillator (AED). The AED can be either fully automatic (FAED) or semiautomatic (SAED). The MED requires the user to be able to immediately and accurately recognise arrhythmias and make the decision whether to initiate defibrillation or not. In comparison, the AED automatically detects and interprets the rhythm without relying on the user’s recognition of arrhythmias. AEDs can be operated in both manual and semiautomatic mode. When using an AED, the user determines whether the person is unresponsive, not breathing and pulseless.54 After checking for a pulse, the AED requires only four steps to operate: turn power on, place self-adhesive electrodes on a victim’s chest, rhythm analysis follows (hands-off period), then (if advised by the machine) press the shock button. The AED will automatically interpret the cardiac rhythm and if VF/VT is present, will advise the operator to provide a shock. This ‘hands-off’ period may result in significant interruptions to chest compressions and adversely impact patient survival.55 The combined preshock and the postshock pause ideally should be less than 5 seconds.53 This can be achieved by continuing compressions while the defibrillator is charging and resuming chest compressions immediately after the delivery of the shock. Biphasic AEDs are safe, easy to use and are effective for detecting and classifying arrhythmias (sensitivity 100%, specificity 97%). FAEDs are programmed to assess the rhythm, charge the defibrillator and deliver shocks without user intervention.
Successful defibrillation and survival to discharge is inversely related to the time from onset of ventricular fibrillation to defibrillation. For every minute that passes, the probability of survival decreases 5–10%,56 so resuscitation bodies place great emphasis on early defibrillation. To facilitate early defibrillation, ILCOR endorses the concept of non-medical individuals being authorised, educated and encouraged to use defibrillators.53 This public access to early defibrillation has seen the placement of defibrillators on aircraft, in casinos and cricket grounds, with non-medical personnel such as police, flight attendants, security guards, family members and even children successfully initiating early defibrillation.57,58 The effectiveness of training non-traditional out-of-hospital first responders to use the AED has improved survival to discharge rates.20 Similarly, in-hospital cardiac arrests also occur in any area, and all healthcare workers should be capable of initiating early defibrillation.53 The ARC notes that while BLS does not have to include the use of adjunctive equipment, the use of AEDs by persons with education in their use is supported and should be taught. Figure 24.3 outlines the integration of defibrillation with BLS.
Practice tip
Remember, when using a monophasic defibrillator for AF cardioversion, the use of hand-held paddles is preferable to the use of self adhesive pads.59
For 90% of people in VF, return of a perfusing rhythm will occur after a single shock. However it is rare that a pulse will be palpable with the perfusing rhythm, hence the immediate resumption of chest compressions in the postshock period is supported.53 Failure to successfully convert VF after the single-shock strategy may indicate the need for a period of effective CPR (30 : 2) for 2 min and rhythm reanalysis, then shock if indicated.53 A single shock strategy is now recommended for all patients in cardiac arrest requiring defibrillation for VF or pulseless VT.39 Not all the electrical energy delivered during defibrillation will traverse the myocardium. Table 24.5 outlines some of the common factors contributing to the success or failure of defibrillation. Studies have demonstrated that lower-energy biphasic defibrillators are associated with greater first-shock efficacy, require lower joules, cause less myocardial dysfunction and increase return of spontaneous circulation when compared with the monophasic defibrillator.60,61 The optimum defibrillation energy level is that which sufficiently abolishes the arrhythmia to enable the return of an organised rhythm, with minimal myocardial damage.53 The recommended first shock for a monophasic defibrillator is 360 J and 200 J for biphasic defibrillators. Other biphasic energy levels may be used providing there is relevant clinical data for a specific defibrillator that suggests that an alternative energy level provides adequate shock success (ARC & NZRC Guideline 11.4).62 If the initial shock is unsuccessful, subsequent shocks should be delivered at the above doses or higher energy levels may be selected.61 In children, it is recommended 4J/kg for the initial and subsequent shocks for both biphasic and monophasic defibrillators.53 Standard adult AEDs and pads are suitable for use in children older than 8 years. Ideally, for children between 1 and 8 years paediatric pads and an AED with paediatric capability should be used.63 These pads also are placed as per the adult methodology. If the AED does not have a paediatric mode or paediatric pads then the standard adult AED and pads can be used.24 Defibrillation of infants less than one year of age is not recommended.53
TABLE 24.5 Factors contributing to the success or failure of defibrillation
The importance of early, uninterrupted chest compressions and early defibrillation are well promulgated in the ILCOR guidelines.12 As determining the length of time from collapse is difficult to accurately estimate, it is imperative rescuers perform chest compressions until the defibrillator is both available and charged.64,65
Advanced Life Support
Basic life support can provide around 20–30% of normal cardiac output and a fraction of inspired oxygen (FiO2) of 0.1–0.16. Consequently, a significant number of patients rely on the provision of advanced life support (ALS) for survival. ALS extends BLS to provide the knowledge and skills essential for the initiation of early treatment and stabilisation of people post-cardiac arrest. Advanced skills traditionally include defibrillation, advanced airway management and the administration of resuscitation drugs. While BLS is generally initiated prior to ALS, where a defibrillator and a person trained in its use are available, defibrillation takes precedence over BLS and ALS. The ARC and NZRC algorithm for management of cardiopulmonary arrest (see Figures 24.3 and 24.4) outlines the two decision paths of therapy in ALS: (a) defibrillation and CPR for pulseless VT/VF (shockable); and (b) identifying and treating the underlying cause for non-VT/VF (non shockable).
Advanced Airway Management
A person with signs of acute respiratory distress should be administered oxygen at the highest possible concentration. Initially during CPR, whenever possible, administer the highest possible oxygen concentration.43 Oxygen should never be withheld for fear of adverse effects, as rescue breaths provide an inspired oxygen concentration of only 15–18%. The administration of oxygen alone does not result in adequate ventilation, and as such the establishment of an effective airway is paramount. Airway management is essential in the performance of CPR, and may be administered using a variety of techniques. The choice of advanced airway adjunct is determined by the availability of equipment and experienced personnel (see Table 24.6 and Chapter 15):
TABLE 24.6 Adjuncts used during resuscitation
