Prearrest

The prearrest phase refers to relevant preexisting conditions of the child (e.g., respiratory insufficiency/failure, sepsis, pulmonary hypertension, neurologic disability) and the events that precipitated cardiac arrest (e.g., respiratory decompensation, progressive hypotension and shock, pulmonary hypertensive crisis, drug overdose). Because pediatric patients usually exhibit changes in their physiologic status in the hours leading up to their arrest event, interventions during the prearrest phase should focus on identifying children at risk for arrest, with special attention to early recognition and treatment of respiratory failure and shock. Rapid response teams or medical emergency teams (METs) are in-hospital emergency teams designed specifically for this purpose. While the composition and operating characteristics of these teams vary widely, their existence has become almost universal across pediatric institutions. Implementation of pediatric METs has been successful in that they have been temporally associated with decreased cardiac arrest frequency and mortality. ^, Although METs cannot identify all children at risk for cardiac arrest, it seems reasonable to assume that transferring critically ill children to an intensive care unit (ICU) early in their disease progression for better monitoring and more aggressive interventions would improve clinical outcome. Supporting this contention, late transfers to the ICU (e.g., unrecognized situational awareness failure events [UNSAFE]) are associated with a higher risk of in-hospital mortality. ^,

No-flow/low-flow

To improve outcomes from pediatric cardiac arrest, it is imperative to shorten the no-flow phase of untreated cardiac arrest. To that end, it is important to monitor high-risk patients to facilitate early recognition of the cardiac arrest and initiate basic and advanced life support. Effective CPR optimizes coronary perfusion pressure (CoPP) and cardiac output to support vital organ viability during the low-flow phase. Important tenets of basic life support are: PUSH HARD, ^, PUSH FAST, allow full chest recoil between compressions, and minimize interruptions in chest compressions. For ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT), rapid rhythm identification and prompt defibrillation are vital for successful resuscitation. ^, For all cardiac arrests, it is vital to provide adequate myocardial perfusion, to restore myocardial oxygen delivery, and to assess and reverse the underlying arrest etiology. ^,

Postarrest

Most deaths in children receiving CPR in the hospital occur after initially successful resuscitation. Thus, the immediate postarrest period should be considered a critical time of ongoing intervention. Patients remain at risk for ventricular arrhythmias and critical organ reperfusion injuries. Interventions during the immediate postarrest stage should focus on minimizing secondary injury. Current evidence-based goals include the following: (1) avoid hypotension (i.e., <5th percentile systolic blood pressure for age), ^, (2) avoid fever by proactively providing targeted temperature management, and (3) recognize and promptly treat seizures. ^, This postarrest phase may have the greatest potential for innovative advances to improve functional outcomes and facilitate reintegration of the patient back into society.

The specific phase of resuscitation dictates the focus of care. Interventions that improve outcome during one phase may be deleterious during another. For instance, the administration of vasopressors during the low-flow phase of cardiac arrest raises systemic vascular resistance with the goal of increasing CoPP and the probability of event survival (return of spontaneous circulation [ROSC]). The persistence of this vasoconstriction into the postarrest phase may worsen myocardial strain and dysfunction and negatively impact cerebral perfusion. Current understanding of the physiology of cardiac arrest and recovery allows us to only crudely manipulate blood pressure, oxygen delivery and consumption, body temperature, and other physiologic parameters in our attempts to optimize outcome. Future strategies likely will take advantage of increasing knowledge of mitochondrial bioenergetics, cellular metabolism, and cellular markers of injury and recovery.

Chest compression depth

Pediatric chest compression depth recommendations are largely based on expert clinical consensus using data extrapolated from animal, adult, and limited pediatric studies. Supported by two computer-automated tomography studies suggesting that depths of one-half anteroposterior (AP) chest depth are unattainable in most children, ^, the most recent change to the pediatric depth recommendation occurred in 2015 when the American Heart Association (AHA) Guidelines ^, recommended a compression depth of “at least one-third AP chest depth” rather than “one-third to one-half.” This subtle change acknowledged the potential difficulty (or even potential harm) of trying to provide chest compressions to one-half AP depth. ^, These recommendations correspond to approximately 4 cm in infants and 5 cm in children. Once children reach puberty, the adult CPR depth of “at least 5 cm, but no more than 6 cm” is recommended. Again, an upper limit is placed to acknowledge the potential harm of compressions that are too deep. Future studies that collect data from pediatric patients and that associate quantitatively measured CPR mechanics with physiologic measurements and clinical outcomes (e.g., arterial blood pressure, end-tidal carbon dioxide [E tco ₂ ], ROSC, survival) are needed.

Chest compression rate

Over the last 20 years, there have been minimal changes to the recommended chest compression rate, which has hovered around 100 per minute for adults, children, and infants. These recommendations were initially based primarily on animal models of cardiac arrest showing improved hemodynamic measures and short-term survival outcomes when rates were increased from 60 to greater than 100 per minute. The most recent refinement to the chest compression rate recommendation occurred in 2015, at which time an upper rate limit (120/minute) was added. ^, This change acknowledged animal work dating back to the 1980s establishing that higher rates can have a detrimental effect on stroke volume/cardiac output as a result of shorter diastolic filling times, but was also supported by large clinical studies of adult OHCA from the Resuscitation Outcomes Consortium funded by the National Institutes of Health. ^, Importantly, the guidelines acknowledge that “insufficient data were available for a systematic review of chest compression rate in children” and thereby deferred to the adult guidelines of 100 to 120 chest compressions per minute.

Chest compression fraction/minimizing interruptions

The avoidance of unnecessary interruptions in chest compressions and minimization of the duration of necessary interruptions remain central tenets of high-quality CPR. Laboratory studies have shown that CoPP falls during chest compression interruptions and requires multiple compressions to return to the preinterruption baseline. Recent data in pediatric IHCA suggest that these harmful hemodynamic effects can be attenuated by limiting the frequency and duration of interruptions. Current guidelines call for a goal of maintaining a chest compression fraction (CCF)—the percentage of time during a CPR event spent actually delivering compressions—of more than 80%. However, high-functioning resuscitation teams have reported mean CCFs more than 90%. Recent adult studies have revealed counterintuitive data regarding the relationship between CCF and outcome, but interpretation of these is difficult due to their observational nature. ^,

Duty cycle

Duty cycle (DC), the percentage of time spent during the downstroke of a chest compression, remains a relatively understudied aspect of CPR quality. The 2002 version of the Pediatric Advanced Life Support (PALS) Guidelines recommended that rescuers provide compressions with “approximately equal compression and relaxation phases (DC = 50%).” This approximation was based on the argument that it is difficult for the rescuer to judge or manipulate the DC during compressions when they are provided at rates exceeding 100 per minute. However, there are substantial amounts of preclinical data suggesting that a briefer, more “high-impact” compression phase improves organ blood flow. In a recent single-center clinical study of pediatric in-hospital CPR, the mean DC for events was 40%, with only 5% of events having a DC compliant with guideline recommendations. Unfortunately, an optimal DC to improve outcomes could not be established, highlighting the need for further study of this element of CPR quality.

Arterial blood pressure

In preclinical models of pediatric IHCA, titration of vasopressor administration to CoPP and adjustment of compression depth to systolic blood pressure results in higher rates of survival and improved neurologic outcomes. ^{, , ,} While CoPP monitoring requires simultaneous measurement of diastolic blood pressure (DBP) and central venous pressure, DBP alone is a more clinically feasible surrogate marker of CPR quality. ^, In a large multicenter prospective trial conducted in the CPCCRN, a DBP of 25 mm Hg or higher in infants younger than 1 year and 30 mm Hg or higher in older children was associated with improved survival to hospital discharge and survival with favorable neurologic outcome among children with an ICU arrest.

End-tidal carbon dioxide

E tco ₂ reflects pulmonary blood flow; thus, it is a marker of cardiac output. There are three main themes regarding E tco ₂ use during CPR: (1) low values (<10 mm Hg) are rarely associated with successful resuscitation, (2) E tco ₂ values are generally higher among patients who achieve ROSC, and (3) an abrupt rise in E tco ₂ can be used to detect underlying ROSC during CPR. ^, Similar to hemodynamic-directed CPR described earlier, recent animal work in a neonatal model of cardiac arrest has demonstrated that E tco ₂ -guided chest compressions are associated with improved rates of ROSC compared with standard CPR. ^, In a large multicenter prospective pediatric trial, there was no association between E tco ₂ and survival, highlighting the need for further pediatric study to establish an E tco ₂ target to which CPR could be adjusted. Irrespective of a specific target to guide CPR, E tco ₂ remains a useful device for confirmation of invasive airway placement as long as the CPR is sufficient to provide some amount of pulmonary blood flow.

Despite being recommended by the AHA, providers rarely use physiology to guide the resuscitation effort. However, in a propensity-matched cohort, the use of physiologic monitoring was associated with a higher likelihood of ROSC, indicating that more widespread use may be one method to improve pediatric cardiac arrest outcomes.

Vasopressors

Antiarrhythmics

Other medications

Targeted temperature management

Hyperthermia following cardiac arrest is common in children and is associated with poor neurologic outcome. Therefore, proactive avoidance of fever should be a priority. However, whether a patient should receive therapeutic hypothermia has been a topic of substantial interest. Two large pediatric multicenter trials ( https://www.thapca.org ) in comatose survivors of OHCA and IHCA have failed to demonstrate a benefit of therapeutic hypothermia (32°C–34°C) compared with targeted normothermia (36°C–37.5°C). ^, However, it is worth noting that there was a nonsignificant trend toward improved rates of survival with hypothermia in the out-of-hospital study. As a result, the most recent PALS Guidelines recommended that for infants and children between 24 hours and 18 years of age who remain comatose after OCHA or ICHA, it is reasonable to use either targeted temperature management (TTM) of 32°C to 34°C followed by TTM of 36°C to 37.5°C or to use TTM of 36°C to 37.5°C. In either case, providers should ensure continuous measurement of temperature during the postarrest period and should aggressively avoid and treat fever (temperature of 38°C or more; class I recommendations).

Anticipation and prevention of hypotension

Postarrest myocardial dysfunction and arterial hypotension occur commonly after successful resuscitation. ^{, ,} This postarrest myocardial stunning is pathophysiologically similar to sepsis-related myocardial dysfunction and postcardiopulmonary bypass myocardial dysfunction, including increases in inflammatory mediators and nitric oxide production. Four small observational studies after pediatric cardiac arrest have demonstrated lower rates of survival to hospital discharge when children exhibited hypotension after ROSC. ^{, , ,} One of these studies associated post-ROSC hypotension (defined as a systolic blood pressure <5th percentile for age) after IHCA with a lower likelihood of survival to discharge with favorable neurologic outcome. Interestingly, only about half of the patients with hypotension in this study were treated, highlighting postarrest hypotension as an underrecognized therapeutic target. In response, the most recent iteration of the PALS Guidelines recommended that when appropriate resources are available, providers should both continuously monitor invasive arterial pressure after ROSC and use parenteral fluids, inotropes, and vasopressors to avoid/treat hypotension (class I recommendation).

Postarrest oxygenation and ventilation management

In children, hyperoxia is common and continuous normoxia is rarely achieved in the 6 hours following cardiac arrest. One report in pediatrics has demonstrated a survival benefit of normoxia (Pa o ₂ ≥60 and <300 mm Hg) over hyperoxia (Pa o ₂ >300 mm Hg). Similarly, hypocapnia (Pa co ₂ <30 mm Hg) and hypercapnia (Pa co ₂ ≥50 mm Hg) were both associated with mortality in pediatric observational studies. As such, the most recent PALS Guidelines made recommendations to avoid extremes of oxygenation and ventilation, with the understanding that avoiding hypoxemia is most important .

Monitoring for and treating seizures

Seizures are present in up to 30% of patients after cardiac arrest. Moreover, certain electroencephalographic findings (abnormal background, burst suppression, and subclinical status epilepticus) are all associated with worse neurologic outcome. Therefore, most experts agree that close monitoring and treatment of status epilepticus in the postarrest phase is important, although there is a paucity of data showing that treatment of seizures improves outcomes. In deciding on how to treat seizures in the postarrest period, providers must be aware of potential side effects of antiepileptic drugs and be prepared to treat them. For example, causing severe hypotension with benzodiazepines and/or other antiepileptic drugs may provide more harm than benefit.

Contemporary methods to improve cardiopulmonary resuscitation quality

Extracorporeal cardiopulmonary resuscitation

Extracorporeal membrane oxygenation (ECMO) has been increasingly used during resuscitation when standard CPR alone does not result in ROSC. In a large CPCCRN study of ICU CPR, more than 15% of the 77% of patients who achieved return of circulation did so through use of ECMO instituted during CPR. In children with medical or surgical cardiac diseases, Extracorporeal CPR (E-CPR) has been shown to improve survival to hospital discharge and can be effective even after prolonged CPR (>50 minutes). In a recent GWTG-R study that included patients from all illness categories who received at least 10 minutes of CPR, E-CPR was associated with improved rates of survival and favorable neurologic outcome at discharge compared with conventional CPR, even after propensity matching. The most recent PALS Guidelines states that E-CPR may be considered for pediatric patients with cardiac diagnoses but highlighted that existing ECMO protocols, expertise, and equipment should be in place. Suitability for E-CPR rescue should be individualized at the patient level with consideration of the reversibility of the underlying process in the ultimate decision rather than focusing on a specific disease category, such as cardiac versus noncardiac.

Airway management

As previously mentioned, most pediatric cardiac arrests are triggered by respiratory deterioration. As such, airway and ventilation management remain basic tenets of pediatric resuscitation. However, it must be noted that tracheal intubation of critically ill children is increasingly being recognized as high risk for precipitating cardiac arrest and that intubation during resuscitation can potentially detract from other therapies. Supporting that contention, a large observational cohort study demonstrated that tracheal intubation during cardiac arrest compared with no intubation is associated with worse rates of survival. Another identified that when intubation was not achieved on the first attempt, outcomes were worse. Similarly, a recent Cardiac Arrest Registry to Enhance Survival (CARES) study of pediatric OHCA found higher survival rates among children receiving bag-mask ventilation (BMV) compared with those who were intubated. As such, the 2019 PALS update states that BMV is reasonable when compared with advanced airway interventions for pediatric OHCA but was unable to make a recommendation regarding BMV versus advanced airway management for pediatric IHCA. Further study as to why tracheal intubation may be associated with worse outcomes (e.g., interruptions in CPR for the procedure, decreased venous return due to increased intrathoracic pressure, poor CPR quality as the team is distracted during tracheal intubation) are necessary.

Ventilation during pediatric cardiopulmonary resuscitation

Despite children having much higher ventilation rates at baseline and more pediatric cardiac arrests being associated with respiratory deterioration, CPR guidelines recommend a ventilation rate of 10 breaths/minute for both children and adults. This recommendation was made partly to simplify training but also to avoid the risk of excessive ventilation worsening hemodynamics, as is evident in some animal models of adult cardiac arrest. ^, In contrast to these animal studies, a recent multicenter CPCCRN study found that higher rates were associated with improved outcomes. Similar pediatric models have also found that higher rates may be beneficial to children. Cumulatively, these studies may indicate that future PALS Guidelines should reevaluate existing CPR ventilation rate recommendations for children and that prospective studies on this topic are needed.

Ventricular fibrillation and pulseless ventricular tachycardia

Pediatric VF/pVT has been an underappreciated problem. Believing that these lethal rhythms are rare in children can lead to a uniformly fatal outcome. Reports indicate that these shockable rhythms occur in 27% of pediatric IHCAs at some time during CPR. The treatment of choice for short-duration VF is prompt defibrillation. Adult studies have established that the mortality rate increases by 7% to 10% per minute of delay to defibrillation. In 2018, the corresponding pediatric study investigating the association between time to defibrillation and survival was published. Unlike the adult study, there was no association between delayed defibrillation and outcomes. These surprising findings were likely due to known differences between pediatric and adult IHCA. As a specific example, more pediatric IHCAs occur in ICUs in highly monitored patients. Presumably, these patients are more likely to receive immediate high-quality CPR, which may make time to defibrillation less important as high-quality CPR preserves the metabolic milieu for successful defibrillation longer. In short, more work is clearly needed regarding optimal defibrillation strategies in children. Regardless, a high index of suspicion for shockable rhythms, both as the initial rhythm and as subsequent rhythms later during cardiac arrest, and timely defibrillation when indicated remain of paramount importance.

Pediatric automated external defibrillators

Automated external defibrillators (AEDs) have improved adult survival from VF and are recommended for use in children 8 years or older with cardiac arrest. The available data suggest that some AEDs can accurately diagnose VF in children of all ages and rarely inaccurately recommend defibrillation. The energy doses delivered by AEDs are high, but they are below the range demonstrated to cause harm in laboratory animal studies of shock toxicity. Adapters with smaller defibrillation pads that dampen the amount of energy delivered have been developed as attachments to adult AEDs, facilitating their use in children. Given these advances, consensus guidelines recommend that AEDs be used in younger children, including infants, when manual defibrillators are not available. Importantly, recent data demonstrate relatively low rates of AED application to children with OHCA, suggesting that this as an area for additional education and training.