Out-of-Hospital Pediatric Cardiac Arrest: Where Are We Now and Where Do We Need to Go?

Abstract

Out-of-hospital pediatric cardiac arrest is difficult to study, and I congratulate the authors in this month's Annals of Emergency Medicine for their thorough systematic review of the current state of knowledge.1Donoghue A.J. Nadkarni V. Berg R.A. et al.for the Can Am Pediatric Cardiac Arrest InvestigatorsOut-of-hospital pediatric cardiac arrest: an epidemiologic review and assessment of current knowledge.Ann Emerg Med. 2005; 46: 512-522Abstract Full Text Full Text PDF PubMed Scopus (342) Google Scholar With due respect to the investigators who contributed to this knowledge base and to the authors of this report, I suspect that many Annals readers may feel uncertain about what we really know about out-of-hospital pediatric cardiac arrest and, more importantly, how that knowledge can be used to improve outcome. Other than knowing that outcome after out-of-hospital pediatric cardiac arrest is poor, this systematic review illustrates important limitations of this type of review because of the limitations of the studies on which it is based. The author's initial goals of clearly identifying gaps in our knowledge and determining the effects of commonly used interventions on outcome are difficult to deduce from the available data. Although 41 studies and more than 5,300 children are included in the identified studies, a minority of these studies could be evaluated when looking at the association of specific interventions on outcome, such as bystander cardiopulmonary resuscitation or the association of the initial rhythm with outcome in various patient causal categories.As the authors discuss under study limitations, observational studies often use inconsistent study designs. This inconsistency is clearly true for cardiac arrest studies and is illustrated by the more than 7-fold variation in the reported incidence of cardiac arrest (2.6 to 19.7 cases per 100,000 pediatric population) and the surprising results about outcome after traumatic-induced arrest. As the authors correctly note, however, the method of patient inclusion into the National Pediatric Trauma Registry database likely included children who were not in cardiac arrest. Once children in these National Pediatric Trauma Registry reports were excluded, traumatic cardiac arrest resulted in poor outcome, as expected. Throughout the more than 20 years of reports included in this review, imprecise inclusion and exclusion criteria were used. The pediatric Utstein guidelines for reporting data were not published until 19952Zaritsky A. Nadkarni V. Hazinski M.F. et al.Recommended guidelines for uniform reporting of pediatric advanced life support: the pediatric Utstein style: American Academy of Pediatrics, American Heart Association and the European Resuscitation Council.Ann Emerg Med. 1995; 26: 487-503Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar and were incorporated to various degrees in subsequent reports. In addition to variable inclusion criteria, different outcome definitions were used. Furthermore, the most commonly used functional outcome used was designed for school-aged children (the Pediatric Overall and Cerebral Performance Categories)3Fiser D.H. Assessing the outcome of pediatric intensive care.J Pediatr. 1992; 121: 68-74Abstract Full Text PDF PubMed Scopus (631) Google Scholar and was never validated as an outcome measure in infants. The latter is particularly important because many pediatric cardiac arrest victims are infants and toddlers (47% of the arrests in the reports included in this review were experienced by patients younger than 1 year).The authors searched the literature from 1966 to 2004, but the first article that met their inclusion and exclusion criteria was published in 1983,4Eisenberg M. Bergner L. Hallstrom A. Epidemiology of cardiac arrest and resuscitation in children.Ann Emerg Med. 1983; 12: 672-674Abstract Full Text PDF PubMed Scopus (172) Google Scholar covering 6.5 years, so their systematic review represents the experience during the last 26 years or so. Within this window, significant changes in the guidelines, training, and performance expectations of out-of-hospital providers occurred. These changes are difficult to account for in this type of systematic review. For example, was high dose epinephrine used more frequently in the past even though data from a recent blinded, randomized, in-hospital trial showed that outcome was worse with high dose epinephrine compared with standard dose epinephrine?5Perondi M.B.M. Reis A.G. Paiva E.F. et al.A comparison of high-dose and standard-dose epinephrine in children with cardiac arrest.N Engl J Med. 2004; 350: 1722-1730Crossref PubMed Scopus (244) Google Scholar Previous training emphasized the importance of providing adequate ventilation to pediatric patients because of the common association of a respiratory cause with the cause of an arrest. More recent data now show that excess ventilation likely impairs venous return and thus cardiac output, leading to a poorer outcome.6Aufderheide T.P. Sigurdsson G. Pirrallo R.G. et al.Hyperventilation-induced hypotension during cardiopulmonary resuscitation.Circulation. 2004; 109: 1960-1965Crossref PubMed Scopus (641) Google Scholar Little attention is given in most cardiac arrest reports to the specific interventions provided and, perhaps more important, the quality of adherence to the guidelines. As recently demonstrated, even well-trained health care providers often provide too many ventilations and not enough compressions.7Abella B.S. Sandbo N. Vassilatos P. et al.Chest compression rates during cardiopulmonary resuscitation are suboptimal: a prospective study during in-hospital cardiac arrest.Circulation. 2005; 111: 428-434Crossref PubMed Scopus (549) Google ScholarOne potentially important factor that may affect outcome after out-of-hospital cardiac arrest was not discussed in this systematic review: changes in pediatric intensive care. Although the focus of this review is on out-of-hospital interventions, the outcome of children admitted to the hospital is clearly influenced by interventions provided or not provided in the phase after return of spontaneous circulation. In this systematic review, almost twice as many children survived to hospital admission (23.9%) as subsequently survived to discharge (12.1%). It is implausible to think that the outcome after out-of-hospital cardiac arrest is determined only by the interventions provided in the out-of-hospital setting. Throughout the past 20 years, we have learned that close attention to avoidance of hyperthermia, avoidance of high tidal volumes in acute respiratory distress syndrome,8The Acute Respiratory Distress Syndrome Network Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome.N Engl J Med. 2000; 342: 1301-1308Crossref PubMed Scopus (9938) Google Scholar use of short term hypothermia,9The Hypothermia after Cardiac Arrest Study Group Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest.N Engl J Med. 2002; 346: 549-556Crossref PubMed Scopus (4411) Google Scholar tight glucose level control,10Van den Berghe G. Wouters P. Weekers F. et al.Intensive insulin therapy in critically ill patients.N Engl J Med. 2001; 345: 1359-1367Crossref PubMed Scopus (8109) Google Scholar and other interventions improve patient outcome. In addition, it is likely that the quality of ICUs, patient monitoring, and interhospital transport have all improved during the past 20 years, making comparisons over time more difficult. Even within the same ICU setting there is variation in care provided that may affect outcome. None of the reports describe a consistent approach to postresuscitation care.So where do we need to go from here? In my opinion, it is time to move our science forward from retrospective reviews and reports. We are not going to learn how to improve outcome until we conduct prospective multicentered trials using adequately explicit treatment interventions that detail important care interventions in the out-of-hospital, emergency department (ED), and ICU settings. Consistent definitions must be used, initial rhythm should be documented, metronomes or other devices may be useful to ensure consistent application of compressions and ventilations, and emergency medical services (EMS) providers must be trained to provide appropriate depth of chest compressions and minimize interruptions of chest compressions. Subsequent care should include attention to the avoidance of hyperthermia, to goal-directed therapy to reverse the common postarrest myocardial dysfunction and shock after cardiac arrest, and perhaps to early glucose level control. Ventilation should be adjusted to achieve normocarbia in most victims and to avoid excessive mean airway pressure, which may compromise cardiac output.Although “intact” survival to hospital discharge is the goal of our resuscitation interventions, there is probably value in studying other outcomes that may better reflect the utility of out-of-hospital interventions. These interval outcomes include the rate of return of spontaneous circulation, survival to ED arrival, and survival to ICU admission. Clearly, if the child does not survive to these endpoints, he or she will not survive to hospital discharge and therefore may not benefit from hospital-based interventions such as therapeutic hypothermia. For children who survive to hospital discharge, we need more precise assessments of their level of functioning. As used in this systematic review, “intact neurologic survival” is often a subjective assessment, which is frequently imprecise in infants and young children. In the absence of adequate neuropsychiatric testing, it is likely that some “intact” children with global hypoxic-ischemic insults have morbidity in the form of poor school performance and behavioral problems that affect their lives. We have few data to help guide inhospital and rehabilitative therapies that may improve these qualities of patient outcome.In summary, it is time to cease creating our resuscitation guidelines based on little to no high quality evidence. It does not help us to know that outcome is poor after out-of-hospital pediatric cardiac arrest unless we use that knowledge to motivate us to go to the next step. Creating high quality evidence will require careful planning with a collaborative effort because few EMS systems are likely to treat enough children to perform an adequately powered intervention study. Out-of-hospital pediatric cardiac arrest is difficult to study, and I congratulate the authors in this month's Annals of Emergency Medicine for their thorough systematic review of the current state of knowledge.1Donoghue A.J. Nadkarni V. Berg R.A. et al.for the Can Am Pediatric Cardiac Arrest InvestigatorsOut-of-hospital pediatric cardiac arrest: an epidemiologic review and assessment of current knowledge.Ann Emerg Med. 2005; 46: 512-522Abstract Full Text Full Text PDF PubMed Scopus (342) Google Scholar With due respect to the investigators who contributed to this knowledge base and to the authors of this report, I suspect that many Annals readers may feel uncertain about what we really know about out-of-hospital pediatric cardiac arrest and, more importantly, how that knowledge can be used to improve outcome. Other than knowing that outcome after out-of-hospital pediatric cardiac arrest is poor, this systematic review illustrates important limitations of this type of review because of the limitations of the studies on which it is based. The author's initial goals of clearly identifying gaps in our knowledge and determining the effects of commonly used interventions on outcome are difficult to deduce from the available data. Although 41 studies and more than 5,300 children are included in the identified studies, a minority of these studies could be evaluated when looking at the association of specific interventions on outcome, such as bystander cardiopulmonary resuscitation or the association of the initial rhythm with outcome in various patient causal categories. As the authors discuss under study limitations, observational studies often use inconsistent study designs. This inconsistency is clearly true for cardiac arrest studies and is illustrated by the more than 7-fold variation in the reported incidence of cardiac arrest (2.6 to 19.7 cases per 100,000 pediatric population) and the surprising results about outcome after traumatic-induced arrest. As the authors correctly note, however, the method of patient inclusion into the National Pediatric Trauma Registry database likely included children who were not in cardiac arrest. Once children in these National Pediatric Trauma Registry reports were excluded, traumatic cardiac arrest resulted in poor outcome, as expected. Throughout the more than 20 years of reports included in this review, imprecise inclusion and exclusion criteria were used. The pediatric Utstein guidelines for reporting data were not published until 19952Zaritsky A. Nadkarni V. Hazinski M.F. et al.Recommended guidelines for uniform reporting of pediatric advanced life support: the pediatric Utstein style: American Academy of Pediatrics, American Heart Association and the European Resuscitation Council.Ann Emerg Med. 1995; 26: 487-503Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar and were incorporated to various degrees in subsequent reports. In addition to variable inclusion criteria, different outcome definitions were used. Furthermore, the most commonly used functional outcome used was designed for school-aged children (the Pediatric Overall and Cerebral Performance Categories)3Fiser D.H. Assessing the outcome of pediatric intensive care.J Pediatr. 1992; 121: 68-74Abstract Full Text PDF PubMed Scopus (631) Google Scholar and was never validated as an outcome measure in infants. The latter is particularly important because many pediatric cardiac arrest victims are infants and toddlers (47% of the arrests in the reports included in this review were experienced by patients younger than 1 year). The authors searched the literature from 1966 to 2004, but the first article that met their inclusion and exclusion criteria was published in 1983,4Eisenberg M. Bergner L. Hallstrom A. Epidemiology of cardiac arrest and resuscitation in children.Ann Emerg Med. 1983; 12: 672-674Abstract Full Text PDF PubMed Scopus (172) Google Scholar covering 6.5 years, so their systematic review represents the experience during the last 26 years or so. Within this window, significant changes in the guidelines, training, and performance expectations of out-of-hospital providers occurred. These changes are difficult to account for in this type of systematic review. For example, was high dose epinephrine used more frequently in the past even though data from a recent blinded, randomized, in-hospital trial showed that outcome was worse with high dose epinephrine compared with standard dose epinephrine?5Perondi M.B.M. Reis A.G. Paiva E.F. et al.A comparison of high-dose and standard-dose epinephrine in children with cardiac arrest.N Engl J Med. 2004; 350: 1722-1730Crossref PubMed Scopus (244) Google Scholar Previous training emphasized the importance of providing adequate ventilation to pediatric patients because of the common association of a respiratory cause with the cause of an arrest. More recent data now show that excess ventilation likely impairs venous return and thus cardiac output, leading to a poorer outcome.6Aufderheide T.P. Sigurdsson G. Pirrallo R.G. et al.Hyperventilation-induced hypotension during cardiopulmonary resuscitation.Circulation. 2004; 109: 1960-1965Crossref PubMed Scopus (641) Google Scholar Little attention is given in most cardiac arrest reports to the specific interventions provided and, perhaps more important, the quality of adherence to the guidelines. As recently demonstrated, even well-trained health care providers often provide too many ventilations and not enough compressions.7Abella B.S. Sandbo N. Vassilatos P. et al.Chest compression rates during cardiopulmonary resuscitation are suboptimal: a prospective study during in-hospital cardiac arrest.Circulation. 2005; 111: 428-434Crossref PubMed Scopus (549) Google Scholar One potentially important factor that may affect outcome after out-of-hospital cardiac arrest was not discussed in this systematic review: changes in pediatric intensive care. Although the focus of this review is on out-of-hospital interventions, the outcome of children admitted to the hospital is clearly influenced by interventions provided or not provided in the phase after return of spontaneous circulation. In this systematic review, almost twice as many children survived to hospital admission (23.9%) as subsequently survived to discharge (12.1%). It is implausible to think that the outcome after out-of-hospital cardiac arrest is determined only by the interventions provided in the out-of-hospital setting. Throughout the past 20 years, we have learned that close attention to avoidance of hyperthermia, avoidance of high tidal volumes in acute respiratory distress syndrome,8The Acute Respiratory Distress Syndrome Network Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome.N Engl J Med. 2000; 342: 1301-1308Crossref PubMed Scopus (9938) Google Scholar use of short term hypothermia,9The Hypothermia after Cardiac Arrest Study Group Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest.N Engl J Med. 2002; 346: 549-556Crossref PubMed Scopus (4411) Google Scholar tight glucose level control,10Van den Berghe G. Wouters P. Weekers F. et al.Intensive insulin therapy in critically ill patients.N Engl J Med. 2001; 345: 1359-1367Crossref PubMed Scopus (8109) Google Scholar and other interventions improve patient outcome. In addition, it is likely that the quality of ICUs, patient monitoring, and interhospital transport have all improved during the past 20 years, making comparisons over time more difficult. Even within the same ICU setting there is variation in care provided that may affect outcome. None of the reports describe a consistent approach to postresuscitation care. So where do we need to go from here? In my opinion, it is time to move our science forward from retrospective reviews and reports. We are not going to learn how to improve outcome until we conduct prospective multicentered trials using adequately explicit treatment interventions that detail important care interventions in the out-of-hospital, emergency department (ED), and ICU settings. Consistent definitions must be used, initial rhythm should be documented, metronomes or other devices may be useful to ensure consistent application of compressions and ventilations, and emergency medical services (EMS) providers must be trained to provide appropriate depth of chest compressions and minimize interruptions of chest compressions. Subsequent care should include attention to the avoidance of hyperthermia, to goal-directed therapy to reverse the common postarrest myocardial dysfunction and shock after cardiac arrest, and perhaps to early glucose level control. Ventilation should be adjusted to achieve normocarbia in most victims and to avoid excessive mean airway pressure, which may compromise cardiac output. Although “intact” survival to hospital discharge is the goal of our resuscitation interventions, there is probably value in studying other outcomes that may better reflect the utility of out-of-hospital interventions. These interval outcomes include the rate of return of spontaneous circulation, survival to ED arrival, and survival to ICU admission. Clearly, if the child does not survive to these endpoints, he or she will not survive to hospital discharge and therefore may not benefit from hospital-based interventions such as therapeutic hypothermia. For children who survive to hospital discharge, we need more precise assessments of their level of functioning. As used in this systematic review, “intact neurologic survival” is often a subjective assessment, which is frequently imprecise in infants and young children. In the absence of adequate neuropsychiatric testing, it is likely that some “intact” children with global hypoxic-ischemic insults have morbidity in the form of poor school performance and behavioral problems that affect their lives. We have few data to help guide inhospital and rehabilitative therapies that may improve these qualities of patient outcome. In summary, it is time to cease creating our resuscitation guidelines based on little to no high quality evidence. It does not help us to know that outcome is poor after out-of-hospital pediatric cardiac arrest unless we use that knowledge to motivate us to go to the next step. Creating high quality evidence will require careful planning with a collaborative effort because few EMS systems are likely to treat enough children to perform an adequately powered intervention study.