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Cardiopulmonary Resuscitation and Advanced Cardiac Life Support
Key Points
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Cardiac arrest is a major public health issue worldwide. Despite significant advances in resuscitation science, survival rates remain considerably low. Improvement of patient survival and neurologic outcome relies on the development and implementation of vigorous and evidence-based resuscitation guidelines involving basic life support (BLS), advanced cardiovascular life support, and post–cardiac arrest care.
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In cardiac arrests without hypoxic causes, oxygen content in the lungs at the time of cardiac arrest is usually sufficient for maintaining acceptable arterial oxygen content during the first several minutes of cardiopulmonary resuscitation (CPR). Blood flow rather than arterial oxygen content is the limiting factor for oxygen delivery to coronary, cerebral, and systemic circulation during CPR. Thus rescue breaths are less important than initiating effective chest compressions as soon as possible after sudden cardiac arrest (SCA).
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The mechanism through which chest compressions generate blood flow can be explained by the thoracic or cardiac pump theories. The provision of uninterrupted, high-quality chest compressions after SCA is associated with better survival and neurologic outcomes than delaying chest compressions for airway intervention in both adult and pediatric patients. Circulation, airway, breathing has replaced airway, breathing, circulation.
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A single resuscitative shock should be delivered at the earliest possible opportunity after the recognition of cardiac arrest, followed immediately by the resumption of chest compressions without postshock cardiac rhythm analysis. Outcome studies have failed to demonstrate the benefit of a period of chest compressions before shock or for a series of stacked shocks.
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Vasopressor medications during resuscitation have been de-emphasized in deference to providing uninterrupted, high-quality chest compressions. Standard-dose epinephrine (1 mg every 3-5 minutes) is recommended for patients in cardiac arrest. Vasopressin offers no advantage as a substitute for epinephrine in cardiac arrest and has been removed from the adult cardiac arrest algorithm. Steroids combined with a vasopressor bundle or cocktail of epinephrine and vasopressin improved return of spontaneous circulation (ROSC) compared with the use of placebo and epinephrine alone in out-of-hospital cardiac arrest.
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Continuous-flow left ventricular assist devices result in an unconventional, unique physiologic state of hemodynamically stable pulseless electric activity. Assessment of adequate tissue perfusion is the most important factor in determining the need for circulatory assistance such as chest compressions. Total artificial hearts (TAHs) are refractory to chest compressions, antiarrhythmic drugs, and electric therapy. Vasopressor medications are contraindicated because they increase afterload, result in complete hemodynamic collapse with pulmonary edema, and worsen TAH function.
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In consideration of opioid overdose epidemiology, patients with known or suspected opioid addiction who are in cardiac or respiratory arrest should receive intravenous, intramuscular, or intranasal naloxone in addition to standard BLS care.
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For nonshockable rhythms, the essential step will be early detection and correction of potentially reversible underlying causes. Ultrasound technology is used to assess the etiology and the management of these patients, as well as to predict the possibility of ROSC and to justify the termination of resuscitative efforts. However, utilization of this technique should not interfere with other resuscitation efforts such as chest compressions.
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Asphyxiation is a much more common cause of cardiac arrest in infants and children than the primary cardiac event, and airway management and ventilation are therefore more important during the resuscitation of children. However, in order to facilitate training, retention, and implementation of resuscitation guidelines, the pediatric resuscitation guidelines follow similar principles as adult guidelines.
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Targeted temperature management (TTM) applied to comatose survivors of out-of-hospital cardiac arrests has significantly improved the neurologic recovery in those surviving to hospital discharge. A target temperature between 32°C and 36°C is recommended for at least 24 hours, and normothermia (to treat fever) should be maintained beyond this window. Prognostication should not occur until 72 hours after ROSC or, if TTM is provided, 72 hours after completion of TTM.
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Most deaths after SCA in both adults and children typically occur within the first 24 hours. Coordinated postresuscitation care involving access to coronary catheterization capabilities and intensive care management that includes TTM represents the best chance survivors of SCA have for optimal neurologic and cardiac recovery.
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New technologies such as individualized CPR, extracorporeal CPR, controlled automated reper-fusion of the whole body (CARL), and emergency preservation for delayed resuscitation may offer opportunities for patients suffering from cardiac arrest.
Acknowledgment
The editors and publisher would like to thank Drs. Brian P. McGlinch and Roger D. White for contributing a chapter on this topic in the prior edition of this work. It has served as the foundation for the current chapter.
Sudden Cardiac Arrest and Cardiopulmonary Resuscitation
Brief History and Physiologic Considerations
Cardiac arrest is a major public health issue, with more than 500,000 deaths per year in the United States. Seventy percent of out-of-hospital cardiac arrests (OHCAs) occur at home, and approximately 50% are unwitnessed. Despite significant advances in resuscitation science, survival rates remain considerably low for both OHCA and in-hospital cardiac arrest (IHCA). Only 10.4% of adult patients with nontraumatic cardiac arrest who receive resuscitative efforts from emergency medical services (EMS) survive to hospital discharge. IHCA has a better outcome, with 22.3% to 25.5% of adults surviving to hospital discharge. Statistics for Europe are similar, with OHCA as one of the leading causes of death in Europe and an overall survival rate of 2.6% to 10.7%.
Sudden cardiac arrest (SCA) is a complex and dynamic process. Forward systemic arterial blood flow continues after cardiac arrest until the pressure gradient between the aorta and right heart reaches equilibrium. A similar process occurs with forward pulmonary blood flow between the pulmonary artery and the left atrium. As the arteriovenous pressure gradient diminishes, the left heart filling is decreased, right heart filling is increased, and the venous capacitance vessels become increasingly distended. When the arterial and venous pressures reach equilibration (approximately 5 minutes after no-flow cardiac arrest), coronary perfusion and cerebral blood flows stop. The goal of cardiopulmonary resuscitation (CPR) thus is to maintain oxygen and blood supply to vital organs, restore spontaneous circulation, minimize postresuscitation organ injury, and ultimately improve the patient’s survival and neurologic outcome.
The history of CPR traces back to the biblical age. However, the more contemporary approach to CPR dates back to the 1950s. James Elam and Peter Safar showed that the earlier methods of resuscitation with chest-pressure and arm-lift were ineffective, and that mouth-to-mouth ventilation was an easily learned and life-saving approach. William B. Kouwenhoven of Johns Hopkins University is credited with introducing a formalized system of chest compressions. Claude Beck of Case Western Reserve University and Paul Zoll of Beth Israel Hospital introduced defibrillation to break ventricular fibrillation. In 1966 the National Academy of Sciences National Research Council conference generated consensus standards for the performance of CPR and opened the modern era of CPR.
The mechanism through which chest compressions generate blood flow can be explained by the thoracic or cardiac pump theories. The thoracic pump theory postulates that blood flows from the thorax when the intrathoracic vascular pressures exceed extrathoracic pressures. The venous-to-arterial blood flow direction is a result of venous valves that prevent retrograde flow at the thoracic inlet. According to the cardiac pump theory, blood flow is generated as a result of actual compression of the heart between the sternum and the vertebral column. Transesophageal echocardiography (TEE) during CPR in humans allowed direct visualization of changes in cardiac chambers and valve functions during chest compressions, as well as the direction of blood flow. During chest compression, the tricuspid and mitral valves close, the left and right ventricular volumes decrease, and blood is ejected into the arterial system. During the decompression phase of CPR, the pressure gradient between the systemic venous system and thoracic cavity facilitates blood flow into the heart chambers. Systemic blood flow during CPR is dependent on effective chest compressions but also on the venous blood return to the heart. Therefore, even modest increases in the intrathoracic pressure, as might occur with overzealous ventilation during CPR, will impair venous return and negatively impact systemic, coronary, and cerebral perfusions and also reduce the chances of return of spontaneous circulation (ROSC).
Cardiac output during CPR with effective, uninterrupted chest compression is at best 25% to 30% of the normal spontaneous circulation. In cardiac arrests without hypoxic causes (e.g., suffocation, drowning), oxygen content in the lungs at the time of cardiac arrest is usually sufficient for maintaining acceptable arterial oxygen content during the first several minutes of CPR. Blood flow rather than arterial oxygen content is the limiting factor for oxygen delivery to coronary, cerebral, and systemic circulation during CPR. Thus rescue breaths are less important than initiating effective chest compressions as soon as possible after SCA.
Understanding the pathophysiology during SCA and CPR is vitally important. The actual improvement of patient outcome, however, relies on development and implementation of vigorous and evidence-based resuscitation guidelines. The more recent recommendations, the 2015 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care (2015 American Heart Association [AHA] Guidelines for CPR and ECC), represent the fourth internationally recognized resuscitation guidelines from the AHA and the European Resuscitation Council; therefore, these guidelines are practiced in many countries and medical specialties. More recently, the guidelines underwent a major updating process change. Instead of updating guidelines every 5 years, the new process involves a continuous evidence evaluation process and annual guidelines update, with the most recent one being the 2017 AHA Guidelines for CPR and ECC update. The intent of this chapter is to review the history, rationale, and current understanding of both basic life support (BLS) and advanced cardiovascular life support (ACLS) techniques based on the most recent updated guidelines.
Basic Life Support
BLS is, according to the Carnegie Safety Institute, the foundation for saving lives after cardiac arrest. Fundamental aspects of adult BLS include immediate recognition of SCA and activation of the emergency response system, early CPR, and rapid defibrillation with an automated external defibrillator (AED). Initial recognition and response to heart attack and stroke are also considered as parts of the BLS. All BLS interventions are time sensitive for preventing SCA, terminating SCA, or supporting circulation until spontaneous circulation is restored. The steps of the adult BLS algorithm for healthcare providers are illustrated in Fig. 86.1 .
The 2015 AHA Guidelines for CPR and ECC on BLS continue to emphasize the simplified universal adult BLS algorithm. The recommended sequence for a single rescuer is to initiate chest compressions before giving rescue breaths (circulation, airway, breathing [C-A-B] rather than airway, breathing, circulation [A-B-C]) to reduce any delay in providing effective chest compressions in adults without any known information of possible asphyxiation as the cause of cardiac arrest. The single rescuer should begin CPR with 30 chest compressions followed by 2 breaths. The guideline, in addition, also emphasizes a simultaneous, choreographed approach to the performance of chest compressions, airway management, rescue breathing, rhythm detection, and shocks (if indicated) by an integrated team of highly trained rescuers in applicable settings such as the hospital environment. With the current rhythm analysis technology, pause of chest compressions may still be required for accurate rhythm analysis, but the compressions should be resumed as soon as possible after rhythm analysis or defibrillation. The key components of high-quality CPR for BLS providers are summarized in Table 86.1 .
Table 86.1
Summary of Components of High-Quality Cardiopulmonary Resuscitation
From Kleinman ME, Brennan EE, Goldberger ZD, et al. Part 5: Adult Basic Life Support and Cardiopulmonary Resuscitation Quality: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation . 2015;132[18 suppl 2]:S414–S435. https://eccguidelines.heart.org/index.php/circulation/cpr-ecc-guidelines-2/part-5-adult-basic-life-support-and-cardiopulmonary-resuscitation-quality/ .
| Component | Adults and Adolescents | Children (Age 1 Year to Puberty) | Infants (Age Less Than 1 Year, Excluding Newborns) |
|---|---|---|---|
| Scene safety | Make sure the environment is safe for rescuers and victim | ||
| Recognition of cardiac arrest | Check for responsiveness No breathing or only gasping (i.e., no normal breathing) No definite pulse felt within 10 s (Breathing and pulse check can be performed simultaneously in less than 10 s) |
||
| Activation of emergency response system | If you are alone with no mobile phone, leave the victim to activate the emergency response system and get the AED before beginning CPR Otherwise, send someone and begin CPR immediately; use the AED as soon as it is available |
Witnessed collapse
Follow steps for adults and adolescents on the left |
|
| Compression-ventilation ratio without advanced airway | 1 or 2 rescuers 30:2 |
1 rescuer 30:2 2 or more rescuers 15:2 |
|
| Compression-ventilation ratio with advanced airway | Continuous compressions at a rate of 100-120/min Give 1 breath every 6 s (10 breaths/min) |
||
| Compression rate | 100-120/min | ||
| Compression depth | At least 2 inches (5 cm) ∗ | At least one-third AP diameter of chest About 2 inches (5 cm) |
At least one-third AP diameter of chest About 1 1⁄2 inches (4 cm) |
| Hand placement | 2 hands on the lower half of the breastbone (sternum) | 2 hands or 1 hand (optional for very small child) on the lower half of the breastbone (sternum) | 1 rescuer 2 fingers in the center of the chest, just below the nipple line 2 or more rescuers 2 thumb–encircling hands in the center of the chest, just below the nipple line |
| Chest recoil | Allow full recoil of chest after each compression; do not lean on the chest after each compression | ||
| Minimizing interruptions | Limit interruptions in chest compressions to less than 10 s | ||
AED , Automated external defibrillator; AP , anteroposterior; CPR , cardiopulmonary resuscitation.
∗ Compression depth should be no more than 2.4 inches (6 cm).
Recognition of Sudden Cardiac Arrest
The necessary first step in the management of cardiac arrest is its immediate recognition. Studies have shown that both lay rescuers and healthcare providers have difficulty detecting a weak pulse. The healthcare provider should take no more than 10 seconds to check for a pulse and, if the rescuer does not definitely feel a pulse within that time period, start chest compressions. Ideally, the pulse check is performed simultaneously with the examination for breathing or gasping, to minimize delay in the detection of cardiac arrest and initiation of CPR. Cardiac arrest victims sometimes present with seizure-like activity or agonal gasps that can confuse potential rescuers. If the victim is unresponsive with absent or abnormal breathing, the rescuer should assume that the victim is in cardiac arrest.
Bystander Cardiopulmonary Resuscitation
For victims of OHCA, the key determinants of survival are timely performance of high-quality bystander CPR and, in the presence of any of the shockable rhythms of ventricular fibrillation or pulseless ventricular tachycardia (VT), defibrillation. Similarly, for IHCA, the important provider-dependent determinants of survival are early defibrillation for shockable rhythms and high-quality CPR, along with recognition and response to deteriorating patients before an arrest. The implication of timely CPR is discussed in the next section of this chapter. The components of high-quality CPR include compressing the chest at an adequate rate and depth, allowing complete chest recoil after each compression, minimizing interruptions in compressions, and avoiding excessive ventilation.
As previously described, chest compressions create blood flow by increasing the intrathoracic pressure and directly compressing the heart. The 2015 AHA Guidelines for CPR and ECC recommended a chest compression rate of 100 to 120/min (updated from at least 100/min), and a chest compression depth for adults of at least 2 inches (5 cm) but not greater than 2.4 inches (6 cm). Despite the “push hard and push fast” recommendation, most CPR feedback devices have shown that compressions are more often too shallow than too deep. In clinical practice, the compression depth may be difficult to judge without the use of feedback devices, and identification of upper limits of compression depth may be challenging. The addition of an upper limit of compression rate is based on a large registry study analysis associating extremely rapid compression rates (greater than 140/min) with inadequate compression depth. Overzealous and rapid chest compressions also compromise chest recoil and venous return, and can potentially have adverse effects on patient survival and outcome.
The total number of compressions delivered during resuscitation is an important determinant of ROSC and survival with good neurologic function from cardiac arrest. The number of compressions delivered is affected by the compression rate (the frequency of chest compressions per minute) and by the compression fraction (the portion of total CPR time during which compressions are performed). Obviously, increases in compression rate and fraction increase the total number of compressions delivered. Compression fraction is improved by reducing the number and duration of any interruptions in compressions (such as securing the airway, delivering rescue breaths, or allowing AED analysis).
Compression-only CPR is easy for an untrained rescuer to perform and can be more effectively guided by dispatchers over the telephone. Moreover, survival rates from adult cardiac arrests of cardiac etiology are similar with either compression only CPR or CPR with both compressions and rescue breaths when provided before EMS arrival. However, for the trained lay rescuer who is able, the recommendation remains for the rescuer to perform both compressions and breaths, especially for victims with asphyxiation causes of cardiac arrest or prolonged CPR. The same emphasis on rescue breathing should also apply to the pediatric population. All lay rescuers should, at a minimum, provide chest compressions for victims of cardiac arrest. The rescuer should continue CPR until an AED arrives and is ready for use, EMS providers take over care of the victim, or the victim starts to move.
The 2015 AHA Guidelines for CPR and ECC emphasize the initiation of chest compressions before ventilation (i.e., a change in the sequence from A-B-C to C-A-B). The prioritization of circulation (C) over ventilation reflected the overriding importance of blood flow generation for successful resuscitation and practical delays inherent to initiation of rescue breaths (B). Physiologically, in most cases of SCA, the need for assisted ventilation is a lower priority because of the availability of adequate arterial oxygen content at the time of a SCA. The presence of this oxygen and its renewal through gasping and chest compressions (provided there is a patent airway) also supported the use of compression-only CPR and the use of passive oxygen delivery.
Shock First or Chest Compressions?
Previous guidelines recommended a period of chest compressions before attempting defibrillation in unwitnessed cardiac arrests or when CPR had been delayed longer than 4 minutes. However, two recent randomized control trials failed to demonstrate a benefit (ROSC or hospital discharge) when CPR was performed before defibrillation. Thus the 2015 AHA Guidelines for CPR and ECC recommend that for adult witnessed cardiac arrests when an AED is immediately available, the defibrillator should be used as soon as possible. For adults with unmonitored cardiac arrest or for whom an AED is not immediately available, it is reasonable that chest compressions be initiated while the defibrillator equipment is being retrieved and applied, and that defibrillation, if indicated, be attempted as soon as the device is ready for use.
Automated External Defibrillators and Manual Defibrillation
Ventricular fibrillation (VF) and pulseless VT are the most common cardiac arrhythmias encountered during witnessed cardiac arrest in adults. CPR prolongs tissue viability and the duration of VF by providing oxygen and energy substrate, but cannot convert the arrhythmia to an organized rhythm in most circumstances. Defibrillation delivers an electrical current passing through the myocardium to interrupt disorganized cardiac activity and restore an organized cardiac rhythm.
The first AED was introduced in 1979. When it is applied to an individual with possible SCA, the AED analyzes the cardiac rhythm, and then automatically attempts defibrillation if it is VF or rapid VT. A trained rescuer needs to simply apply the defibrillator pads to the patient’s chest, activate the AED, and deliver the shock through the push of a button when prompted to do so by the AED. Thus the purpose is to have early defibrillation more readily available through trained bystanders, such as security guards, police, and the general public.
When a standard manual defibrillator is used in resuscitation, the rescuer needs to interpret the rhythm and shock when appropriate. If a monophasic defibrillator is available, then a single 360 joule (J) shock should be delivered. With biphasic defibrillators, a much lower energy level (150-200 J) is usually sufficient to terminate the arrhythmia due to its ability to compensate and adjust for the patient’s impedance. If the rescuer is unfamiliar with the waveform used or the manufacturer recommendations, then the maximal available energy should be used as the default energy. There is no evidence indicating superiority of one biphasic waveform design or energy level for the termination of VF with the first shock. For subsequent shocks, it is reasonable to select fixed versus escalating energy based on the specific manufacturer’s instructions.
The same protocol used with the AED should be applied when using the manual defibrillator: (1) emphasis is placed on delivering uninterrupted chest compressions while defibrillator pads are being applied and for periods when rhythm analysis is not occurring; (2) chest compressions are immediately resumed after shock delivery; (3) cardiac rhythm is reanalyzed as indicated after 2 minutes of chest compressions and rescue breathing; and (4) defibrillation is attempted only for VF and rapid VT.
Single versus Stacked Defibrillation
The 2015 AHA Guidelines for CPR and ECC recommended a 2-minute period of chest compressions after each shock instead of immediate successive shocks for persistent VF. The rationale for this is that when VF is terminated, a brief period of asystole or pulseless electrical activity (PEA) typically ensues and a perfusing rhythm is unlikely to be present immediately, necessitating chest compressions to provide organ perfusion and circulation of ACLS drugs. No difference in the 1-year survival or frequency of VF recurrence was shown when a single shock protocol with 2 minutes of CPR between successive shocks was compared against a previous resuscitation protocol employing three initial stacked shocks with 1 minute of CPR between subsequent shocks. A recent study demonstrated that in monitored in-hospital VF/VT arrests, expeditious defibrillation with use of stacked shocks is associated with a higher rate of ROSC and survival to hospital discharge. Without further data, current AHA guidelines recommend that a single-shock strategy (as opposed to stacked shocks) is reasonable for defibrillation. Stacked defibrillation is considered only during cardiac surgery or in the cardiac catheterization laboratory where invasive monitoring and defibrillation pads are in place already.
Determination of Efficiency of Cardiopulmonary Resuscitation
Immediately after cardiac arrest, when minute ventilation is constant and carbon dioxide (CO 2 ) production is unchanged, the changes in the partial pressure of end-tidal CO 2 (PETCO 2 ) can serve as a reliable surrogate for pulmonary blood flow and cardiac output. This has been proven extensively by animal and human studies during cardiac arrest and CPR and after ROSC. Monitoring of both PETCO 2 by quantitative waveform capnography with controlled ventilation and systemic arterial pressure by invasive monitoring should provide optimal assessment of the efficiency of CPR. These parameters can be monitored continuously, without interrupting chest compressions. An abrupt increase in any of these parameters is a sensitive indicator of ROSC. The 2015 AHA Guidelines for CPR and ECC endorse this monitoring as a class I recommendation for adults with SCA with an endotracheal tube (ETT) or supraglottic airway (SGA) device in place. In addition, coronary perfusion pressure, arterial relaxation pressure, and central venous oxygen saturation can assist in determination of the efficiency of CPR, although these monitoring techniques require more complex catheters or devices. Currently there are no clinical trials that have studied whether titrating resuscitative efforts to a single or combined set of physiologic parameters during CPR results in improved survival or neurologic outcome. However, the 2010 AHA Guidelines for CPR and ECC recommended that PETCO 2 should be maintained above 10 mm Hg, and mathematical models suggest a cumulative maximum PETCO 2 above 20 mm Hg at all time points measured between 5 and 10 minutes postintubation best predicted ROSC.
Update to Airway Management and Ventilation in Cardiac Arrest
When cardiac arrest occurs, adequate oxygen delivery is required to restore the energy state of the heart as well as other vital organs, and consequently ventilation becomes an essential part of the resuscitation. However, it also needs to be emphasized that during the first few minutes after cardiac arrest, oxygen delivery to tissues with CPR is limited more by blood flow and low cardiac output than arterial oxygen content. Low cardiac output associated with CPR results in low oxygen uptake from the lungs that, in turn, reduces the need to ventilate the patient during this low-flow state. Thus chest compressions are the priority intervention, unless the cardiac arrest is due to asphyxiation, drowning, or suffocation, which are the only circumstances in which ventilation must be provided before chest compressions.
Healthcare providers must determine the best way to support ventilation and oxygenation. Options include standard bag-mask ventilation versus placement of an advanced airway (i.e., ETT or SGA device). Bag-mask ventilation with a head tilt–chin lift or head tilt–jaw thrust maneuver is recommended for initial airway control in most circumstances. There is inadequate evidence to show a difference in survival or favorable neurologic outcome with the use of bag-mask ventilation compared with endotracheal intubation or other advanced airway devices. There is also inadequate evidence favoring the use of endotracheal intubation compared with other advanced airway devices. Thus 2015 AHA/Guidelines for CPR and ECC recommend that either a bag-mask device or an advanced airway may be used for oxygenation and ventilation during CPR in both the in-hospital and out-of-hospital settings, assuming that providers have ongoing experience to insert the airway and verify proper position with minimal interruption in chest compressions. The choice of bag-mask device versus advanced airway insertion is determined by the skill and experience of the provider.
Regarding the inspired oxygen concentration, the 2015 AHA Guidelines for CPR and ECC support providing the maximal inspired oxygen concentration during CPR. Since oxygen delivery is dependent on both blood flow and arterial oxygen content and blood flow is typically limited during CPR, it is theoretically important to maximize the oxygen content of arterial blood by maximizing inspired oxygen concentration. Evidence for the detrimental effects of hyperoxia that may exist in the immediate post–cardiac arrest period should not be extrapolated to the low-flow state of CPR, where oxygen delivery is unlikely to exceed demand or cause an increase in tissue PO 2 . Therefore, until further data are available, physiology and expert consensus support providing the maximal inspired oxygen concentration during CPR.
After ETT placement, it is very important to confirm its correct placement, although this could be very challenging due to the patient’s body habitus, low-flow status, and distraction from other resuscitative tasks. In addition to observation of chest rise and auscultation of the lungs and stomach, continuous waveform capnography is recommended as the most reliable method of confirming and monitoring correct placement of an ETT. However, false-positive results (CO 2 detection with esophageal intubation) can still occur, especially within the first few breaths due to air/CO 2 insufflation of the stomach during bag-mask ventilation. False-negative results (i.e., absent exhaled CO 2 in the presence of tracheal intubation) can occur in the setting of pulmonary embolism (PE), low cardiac output, or severe obstructive pulmonary disease. If continuous waveform capnography is not available, a nonwaveform CO 2 detector, fiberoptic scope, esophageal detector, or ultrasound device used by an experienced operator are reasonable alternatives.
If bag-mask ventilation is chosen, 2 breaths are delivered after 30 chest compressions during one- and two-person CPR, providing that the rescuer(s) is(are) trained in CPR. Each breath is delivered over approximately 1 second. After placement of an advanced airway, it is recommended to provide 1 breath every 6 seconds (10 breaths/min) while continuous chest compressions are being performed. Extreme caution should be taken to avoid excessive airway pressure that will compromise venous return in cardiac arrest patients, as hyperventilation is common during enthusiastic resuscitation.
Advanced Cardiac Life Support: Management of Cardiac Arrest
BLS, ACLS, and post–cardiac arrest care are integral steps in the AHA’s “chain of survival” for patients suffering from cardiac arrest. CPR almost invariably necessitates rapid progression to ACLS interventions and follow-up care. There is overlap between these steps, as each stage of care progresses to the next, but generally ACLS comprises the level of care between BLS and post–cardiac arrest care. The 2015 AHA Guidelines for CPR and ECC adult cardiac arrest algorithm is illustrated in Fig. 86.2 . This section reviews the different interventions for managing cardiac arrest patients based on the presenting ECG rhythm, medications used during cardiac arrest, special situations of cardiac arrest, and new technologies developed to facilitate resuscitation and improve the patient’s survival.
Asystole
Asystole is the complete and sustained absence of electrical activity and portends extremely poor prognosis. Management of a patient in cardiac arrest with asystole follows the same pathway as management of PEA (as discussed later). The top priorities are also similar: following the steps in the ACLS Pulseless Arrest Algorithm and identifying and correcting any treatable, underlying causes for the asystole. In most patients, asystole is irreversible, but a brief trial of resuscitation, beginning with effective chest compressions, oxygen therapy, and intravenous (IV) epinephrine, is indicated particularly in the setting of witnessed cardiac arrest. Atropine is no longer recommended for treating asystole. Asystole should be differentiated from agonal bradycardia and fine ventricular fibrillation.
Pulseless Electrical Activity
PEA refers to the presence of organized electrical activity without a palpable pulse. Priority must be given to identifying possible reversible causes of PEA, which is frequently referred to as the five Hs (Hypoxia, Hypovolemia, Hypothermia, Hyper- or Hypokalemia, Hydrogen ions or acidosis) and Ts (Tamponade, Tension pneumothorax, Toxins, Thrombosis Pulmonary, and Thrombosis Coronary). Those causes are first suspected for each patient’s special circumstance. Severe hypoxia in respiratory emergencies can result in PEA. In the traumatized patient, hypovolemia, cardiac tamponade, and tension pneumothorax are possible causes of cardiac arrest and must be considered and acutely treated. Unanticipated cardiac arrest occurring in the intraoperative and postoperative periods should include acute massive pulmonary thromboembolism or air emboli as possible causes. Electrolyte and metabolic derangements such as severe hyperkalemia, metabolic acidosis, or drug (e.g., digitalis, β-blockers, calcium channel blockers, tricyclic antidepressants) overdose frequently presents as idioventricular rhythms. In every circumstance, prompt initiation of chest compressions and the administration of 1 mg epinephrine are recommended as temporizing measures until more definitive therapy can be provided once the cause for the PEA is identified. Each of these scenarios has an associated intervention unique to that situation. Asystole or VF can develop if PEA is not corrected.
Pulseless Ventricular Tachycardia or Ventricular Fibrillation
Pulseless VT and VF are shockable rhythms and hence the most treatable causes of cardiac arrest, yielding the greatest likelihood of ROSC and long-term survival in both in-hospital and out-of-hospital settings. Early defibrillation, not pharmacologic intervention, is responsible for the improved survival after VF cardiac arrest. Therefore, AEDs are placed in public locations to ensure early defibrillation can be performed by rescuers.
When a pulseless VT or VF arrest occurs, defibrillation should be performed at the earliest opportunity. Chest compressions should be immediately resumed after the delivery of shock and continued for 2 minutes before reassessing the underlying cardiac rhythm, unless obvious evidence for ROSC occurs. No evidence supports one biphasic waveform over another. Defibrillation energies should be increased until VF is terminated. In circumstances in which pulseless VT or VF is terminated with defibrillation but pulseless VT or VF recurs, defibrillation should use the previously successful energy level.
If ROSC does not occur after an initial defibrillatory attempt, then five cycles of CPR consisting of 30 compressions to 2 ventilations (nonintubated patient) should be performed before recheck of rhythm. Placement of a SGA device or endotracheal intubation can be considered in this interval. Peripheral IV access should be attempted if not already established without interruption of the chest compressions.
Resuscitation Medications During Cardiac Arrest
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