Performance of Cardiopulmonary Resuscitation in Infants and Children

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Chapter 34 Performance of Cardiopulmonary Resuscitation in Infants and Children

Pediatric cardiac arrest is not a rare event. Approximately 16,000 American children (8-20/100,000 children/year) experience cardiopulmonary arrest each year.15 Approximately half of these cardiac arrests occur in-hospital, and about half outside the hospital.5,6 In times past, survival outcomes were not good and many children had severe neurological injury after their arrest event. With advances in resuscitation science and implementation techniques, survival from pediatric cardiac arrest has improved substantially over the past 25 years.7 This chapter focuses on pediatric cardiac arrest, cardiopulmonary resuscitation (CPR), and other therapeutic interventions that have been specifically designed to improve outcomes from pediatric cardiac arrest.

Four Phases of Cardiac Arrest

The four distinct phases of cardiac arrest and CPR interventions are (1) prearrest, (2) no flow (untreated cardiac arrest), (3) low flow (CPR), and (4) postresuscitation. Interventions to improve the outcome of pediatric cardiac arrest should optimize therapies targeted to the time and phase of CPR, as suggested in Table 34-1.

Table 34–1 Phases of Cardiac Arrest and Targeted Interventions

Phase Interventions
Prearrest phase: Protect

Arrest (no-flow): Preserve Low-flow (CPR): Resuscitate Long-term

Prearrest

The prearrest phase refers to relevant preexisting conditions of the child (e.g., neurologic, cardiac, respiratory, or metabolic problems) and precipitating events (e.g., respiratory failure or shock). It is known that pediatric patients who suffer an in-hospital cardiac arrest often have changes in their physiological status in the hours leading up to their arrest event.8,9 Therefore, interventions during the prearrest phase focus on preventing the cardiac 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. These teams respond to patients on general inpatient units who are at high risk of clinical decompensation and transfer these children to more acute care areas, with the goal to prevent progression to full cardiac arrest. Implementation of pediatric METs has been moderately successful; decreased cardiac arrest frequency and mortality have been demonstrated.1012 While 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 process for better monitoring and more aggressive interventions can improve resuscitative care and clinical outcome.

Postresuscitation

The postresuscitation phase includes management of the immediate postresuscitation stage, the next few hours to days, and long-term rehabilitation. The immediate postresuscitation stage is a high-risk period for ventricular arrhythmias and other reperfusion injuries. Interventions during the immediate postresuscitation stage and the next few days include adequate tissue oxygen delivery, treatment of postresuscitation myocardial dysfunction, and minimizing postresuscitation tissue injury (e.g., preventing postresuscitation hyperthermia, hyperglycemia/hypoglycemia and, perhaps, providing postresuscitation hypothermia). This postarrest phase may have the greatest potential for innovative advances in the understanding of cell injury and death, inflammation, apoptosis, and hibernation, ultimately leading to novel interventions. The rehabilitation stage concentrates on salvage of injured cells, recruitment of hibernating cells, and reengineering of reflex and voluntary communications of these cell and organ systems to improve functional outcome.

The specific phase of resuscitation dictates the focus of care. Interventions that improve outcome during one phase may be deleterious during another. For instance, intense vasoconstriction during the low-flow phase of cardiac arrest improves coronary perfusion pressure and the probability of ROSC. The same intense vasoconstriction during the postresuscitation phase increases left ventricular afterload and may worsen myocardial strain and dysfunction. 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 cellular inflammation, thrombosis, reperfusion, mediator cascades, cellular markers of injury and recovery, and transplantation technology.

An overview of some of the pathophysiologic pathways perturbed by cardiac arrest and resuscitation, along with potential avenues for intervention, is shown in Figure 34-1.

Epidemiology of Pediatric Cardiac Arrest

Cardiovascular disease remains the most common cause of disease-related death in the United States, resulting in approximately 1 million deaths per year.21 It is estimated that more than 400,000 Americans will have a cardiac arrest each year, nearly 90% in prehospital settings. While data regarding the incidence of childhood cardiopulmonary arrest are less robust, the best data suggest that about 16,000 American children suffer a cardiac arrest each year (annual incidence: 8 to 20 per 100,000 children per year).1522 For in-hospital arrests specifically, it is estimated that approximately 2% to 6% of all children admitted to pediatric intensive care units,1,2,23 and 4% to 6% of children admitted to cardiac units will suffer a cardiac arrest.24,25 In short, pediatric cardiac arrest is an important public health problem.

Outcomes from pediatric cardiac arrest have improved significantly over the past 20 years (Table 34-2). Nearly two thirds of children who have an in-hospital cardiac arrest are successfully resuscitated initially (i.e., attain sustained ROSC). Moreover, more than 25% of them will survive to hospital discharge, and many (nearly 75%) will have good neurologic function.14,7,2537 Factors that influence outcome from pediatric cardiac arrest include (1) the preexisting condition of the child, (2) the initial electrocardiographic (ECG) rhythm detected, (3) the duration of no-flow time (the time during an arrest without spontaneous circulation or provision of CPR), and (4) the quality of the life-supporting therapies provided during the resuscitation. With this knowledge, it is no surprise then that out-of-hospital pediatric arrests have worse outcomes compared to in-hospital arrests.3,22,23,30,35,3844 As many of these out-of-hospital events are not witnessed and bystander CPR is not common (less than 30% of children receive bystander CPR),3 the duration of no-flow time can be prolonged. As a result, less than 10% of these children survive their initial event, and in those that do survive, neurological injury is common. These findings are especially troublesome given that bystander CPR more than doubles patient survival rates.45

Compared to adults, superior survival rates are documented after pediatric cardiac arrest, specifically after in-hospital events; 27% of children survive to hospital discharge compared with only 17% of adults.7 These findings may be in part due to differences in the initial ECG rhythm detected. While pediatric arrests are less commonly caused by arrythmias, such as ventricular tachycardia or ventricular fibrillation—10% of pediatric arrests versus 25% of adult arrests—the superior pediatric survival rate reflects a substantially higher survival rate among children with asystole or pulseless electrical activity compared with adults (24% vs. 11%). Moreover, the higher survival rate seen in children is mostly attributable to a much better survival rate among infants and preschool age children compared with older children.26 Although this is speculative, the higher survival rates in children may be due to improved coronary and cerebral blood flow during CPR because of increased chest compliance in these younger arrest victims.46,47

Interventions During the Low-Flow Phase: Cardiopulmonary Resuscitation

Airway and Breathing

During the low-flow state of CPR, cardiac output and pulmonary blood flow are approximately 25% of that during normal sinus rhythm; therefore, much less ventilation is necessary for adequate gas exchange from the blood traversing the pulmonary circulation. Moreover, animal and adult data indicate that a rapid rate of assisted ventilation (“overventilation” from exuberant rescue breathing) during CPR is common and can substantially compromise venous return and cardiac output by increasing intrathoracic pressure.4850 Moreover, these detrimental hemodynamic effects are compounded when one considers the effect of interruptions in CPR to provide airway management and rescue breathing.5155 While overventilation is problematic, in light of the fact that most pediatric arrests are asphyxial in nature, provision of adequate ventilation is still important. The difference between arrythmogenic and asphyxial arrests lies in the physiology. In animal models of sudden VF cardiac arrest, acceptable PaO2 and PaCO2 persist for 4 to 8 minutes during chest compressions without rescue breathing.56 This is in part because aortic oxygen and carbon dioxide concentrations at the onset of the arrest do not vary much from the prearrest state. As a result, the lungs act as a reservoir of oxygen during CPR, and adequate oxygenation and ventilation can continue without rescue breathing. However, during asphyxial arrest, blood continues to flow to tissues in the prearrest state, resulting in significant arterial and venous oxygen desaturation, elevated lactate levels, and depletion of the pulmonary oxygen reserve. Therefore, at the onset of resuscitation, there is substantial arterial hypoxemia and acidemia. In this circumstance, rescue breathing with controlled ventilation can be lifesaving. In contrast, the adverse hemodynamic effects from overventilation during CPR combined with the interruptions in chest compressions to open the airway and deliver rescue breathing are a lethal combination in certain circumstances such as VT/VF arrests. In short, the resuscitation technique should be titrated to the physiology of the patient to optimize patient outcome.

Circulation

Optimizing Blood Flow During Low-Flow Cardiopulmonary Resuscitation: Push Hard, Push Fast

When the heart arrests and no blood flows to the aorta, coronary blood flow ceases immediately.57 At that point, provision of high-quality CPR (push hard, push fast) is necessary to reestablish flow. The goal during CPR is to maximize the myocardial perfusion pressure (MPP). Related by the following equation:

image

myocardial blood flow improves as the gradient between AoDP and RAP increases. During downward compression phase, aortic pressure rises at the same time as right atrial pressure with little change in the MPP. However, during the decompression phase of chest compressions, the right atrial pressure falls faster and lower than the aortic pressure, which generates a pressure gradient perfusing the heart with oxygenated blood during this artificial period of “diastole.” Several animal and human studies have demonstrated in both VT/VF and asphyxial models the importance of establishing MPP as a predictor for short term survival outcome (ROSC).19,5861

Based on the equation above, MPP can be improved by strategies that increase the pressure gradient between the aorta and the right atrium. As an example, the inspiratory impedance threshold device (ITD) is a small, disposable valve that can be connected directly to the tracheal tube or face mask to augment negative intrathoracic pressure during the inspiratory phase of spontaneous breathing and the decompression phase of CPR by impeding airflow into the lungs. Application in animal and adult human trials of CPR has established the ability of the ITD to improve vital organ perfusion pressures and myocardial blood flow51,6265; however, in the only randomized trial during adult CPR, mortality benefit was limited to the subgroup of patients with pulseless electrical activity.66 Additional evidence that augmentation of negative intrathoracic pressure can improve perfusion pressures during CPR comes from the active compression-decompression device (ACD). The ACD is a handheld device that is fixed to the anterior chest of the victim by means of suction—think household plunger—that can be used to apply active decompression forces during the release phase, thereby creating a vacuum within the thorax. By actively pulling during the decompression phase, blood is drawn back into the heart by the negative pressure.67 Animal and adult studies have demonstrated that the combination of ACD with ITD acts in concert to further improve perfusion pressures during CPR compared to ACD alone.63 In the end, while novel interventions such as the ITD and ACD are promising to improve blood flow during CPR, the basic tenants of “push hard, push fast, minimize interruptions, and don’t overventilate” are still the dominate factors to improve blood flow during CPR and chance of survival.

Chest Compression Depth

The pediatric chest compression depth recommendation of at least one-third anterior-posterior chest depth (approximately 4 cm in infants and 5 cm in children) is based largely upon expert clinical consensus, using data extrapolated from animal, adult, and limited pediatric data. Recently, Maher et al. published data from a case series of infants postcardiac surgery associating arterial blood pressure with qualitative chest compression depths. In this small study of 6 infants, chest compressions targeted to one-half anterior-posterior chest depth imparted improved systolic blood pressures compared to those at one-third anterior-posterior chest depth.68 While a small series with qualitatively estimated chest compression depths, this is the first study to collect actual data from children supporting the existing chest compression depth guidelines. On the contrary, two recent studies using computer-automated tomography69,70 suggest that depth recommendations based on a relative (%) anterior-posterior chest compression depth are deeper than those recommended for adults, and that a depth of one-half anterior-posterior chest depth is unattainable in most children. Future studies that collect data from actual children and that associate quantitatively measured chest compression depths with short- and long-term clinical outcomes (arterial blood pressure, end-tidal carbon dioxide, return of spontaneous circulation, survival) are needed.

Compression/Ventilation Ratios

The amount of ventilation provided during CPR should match, but not exceed, perfusion and should be titrated to the amount of circulation during the specific phase of resuscitation as well as the metabolic demand of the tissues. Therefore during the low-flow state of CPR when the amount of cardiac output is roughly 25% of normal, less ventilation is needed.71 However, the best ratio of compressions to ventilations in pediatric patients is largely unknown and depends on many factors including the compression rate, the tidal volume, the blood flow generated by compressions, and the time that compressions are interrupted to perform ventilations. Recent evidence demonstrated that a compression/ventilation ratio of 15:2 delivers the same minute ventilation and increases the number of delivered chest compressions by 48% compared to CPR at a compression/ventilation ratio of 5:1 in a simulated pediatric arrest model.72,73 This is important because when chest compressions cease, the aortic pressure rapidly decreases and coronary perfusion pressure falls rapidly.57 Increasing the ratio of compressions to ventilations minimizes these interruptions, thus increasing coronary blood flow. These findings are in part the reason the American Heart Association (AHA) now recommends a pediatric compression/ventilation ratio of 15:2.

Duty Cycle

In a model of human adult cardiac arrest, cardiac output and coronary blood flow are optimized when chest compressions last for 30% of the total cycle time (approximately 1:2 ratio of time in compression to time in relaxation).74 As the duration of CPR increases, the optimal duty cycle may increase to 50%. In a juvenile swine model, a relaxation period of 250 to 300 milliseconds (duty cycle of 40% to 50% at a compression rate of 120/min) correlates with improved cerebral perfusion pressures compared with shorter duty cycles of 30%.75

Circumferential Versus Focal Sternal Compressions

In adult and animal models of cardiac arrest, circumferential (vest) CPR has been demonstrated to improve CPR hemodynamics dramatically.76 In smaller infants, it is often possible to encircle the chest with both hands and depress the sternum with the thumbs, while compressing the thorax circumferentially (thoracic squeeze). In an infant animal model of CPR, this “two-thumb” method of compression with thoracic squeeze resulted in higher systolic and diastolic blood pressures and a higher pulse pressure than traditional two-finger compression of the sternum.77

Open-Chest Cardiopulmonary Resuscitation

Excellent standard closed-chest CPR generates cerebral blood flow that is approximately 50% of normal. By contrast, open-chest CPR can generate cerebral blood flow that approaches normal. Whereas open-chest massage improves coronary perfusion pressure and increases the chance of successful defibrillation in animals and humans,7880 performing a thoracotomy to allow open-chest CPR is impractical in many situations. A retrospective review of 27 cases of CPR following pediatric blunt trauma (15 with open-chest CPR and 12 with closed-chest CPR) demonstrated that open-chest CPR increased hospital cost without altering rates of ROSC or survival to discharge. However, survival in both groups was 0%, indicating that the population may have been too severely injured or too late in the process to benefit from this aggressive therapy.81 Earlier institution of open-chest CPR may warrant reconsideration in selected special resuscitation circumstances.

Medications Used to Treat Cardiac Arrest

While animal studies have indicated that epinephrine can improve initial resuscitation success after both asphyxial and VF cardiac arrests, no single medication has been shown to improve survival outcome from pediatric cardiac arrest. A variety of medications are used during pediatric resuscitation attempts including vasopressors (epinephrine or vasopressin), antiarrhythmics (amiodarone or lidocaine), and other drugs such as calcium chloride and sodium bicarbonate. Each is discussed separately below.

Vasopressors

Epinephrine (adrenaline) is an endogenous catecholamine with potent α- and β-adrenergic stimulating properties. The α-adrenergic action (vasoconstriction) increases systemic and pulmonary vascular resistance. The resultant higher aortic diastolic blood pressure improves coronary perfusion pressure and myocardial blood flow even though it reduces global cardiac output during CPR. Adequacy of myocardial blood flow is a critical determinant of ROSC. Epinephrine also increases cerebral blood flow during CPR because peripheral vasoconstriction directs a greater proportion of flow to the cerebral circulation.8284 However, recent evidence suggests that epinephrine can decrease local cerebral microcirculatory blood flow at a time when global cerebral flow is increased.85 The β-adrenergic effect increases myocardial contractility and heart rate and relaxes smooth muscle in the skeletal muscle vascular bed and bronchi; however, the β-adrenergic effects are not observed in the peripheral vascular beds secondary to the high dose used in cardiac arrest. Epinephrine also increases the vigor and intensity of VF, increasing the likelihood of successful defibrillation.

High-dose epinephrine (0.05 to 0.2 mg/kg) improves myocardial and cerebral blood flow during CPR more than standard-dose epinephrine (0.01 to 0.02 mg/kg) in animal models of cardiac arrest and may increase the incidence of initial ROSC.86,87 Administration of high-dose epinephrine, however, can worsen a patient’s postresuscitation hemodynamic condition. Retrospective studies indicate that use of high-dose epinephrine in adults or children may be associated with a worse neurologic outcome.88,89 A randomized, controlled trial of rescue high-dose epinephrine versus standard-dose epinephrine following failed initial standard-dose epinephrine in pediatric in-hospital cardiac arrest demonstrated a worse 24-hour survival in the high-dose epinephrine group (1/27 vs. 6/23, P < .05).90 Based on these clinical data, high-dose epinephrine cannot be recommended routinely for either initial or rescue therapy.

Vasopressin is a long-acting endogenous hormone that acts at specific receptors to mediate systemic vasoconstriction (V1 receptor) and reabsorption of water in the renal tubule (V2 receptor). The vasoconstriction is most intense in the skeletal muscle and skin vascular beds. Unlike epinephrine, vasopressin is not a pulmonary vasoconstrictor. In experimental models of cardiac arrest, vasopressin increases blood flow to the heart and brain and improves long term survival compared with epinephrine. However, vasopressin can decrease splanchnic blood flow during and following CPR and can increase afterload in the postresuscitation period.9195 Adult randomized controlled trials suggest that outcomes are similar after use of vasopressin or epinephrine during CPR.96,97 During pediatric arrest, a case series of four children who received vasopressin during six prolonged cardiac arrest events suggested that the use of bolus vasopressin may result in ROSC when standard medications have failed.98 However, a more recent retrospective study of 1293 consecutive pediatric arrests from the National Registry of CPR (NPCRP) found that vasopressin use, while infrequent (administered in only 5% of events), was associated with a lower likelihood of ROSC. Therefore, it is unlikely that vasopressin will replace epinephrine as a first-line agent in pediatric cardiac arrest. However, the available data suggest that its use in conjunction with epinephrine may deserve further investigation.

Buffer Solutions

There are no randomized controlled studies in children examining the use of sodium bicarbonate for management of pediatric cardiac arrest. Two randomized controlled studies have examined the value of sodium bicarbonate in the management of adult cardiac arrest108 and in neonates with respiratory arrest in the delivery room.109 Neither was associated with improved survival. One multicenter retrospective in-hospital pediatric study found that sodium bicarbonate administered during cardiac arrest was associated with decreased survival, even after controlling for age, gender, and first documented cardiac rhythm.99 Therefore, during pediatric cardiac arrest resuscitation, the routine use of sodium bicarbonate is NOT recommended.

Clinical trials involving critically ill adults with severe metabolic acidosis did not demonstrate a beneficial effect of sodium bicarbonate on hemodynamics despite correction of acidosis.110,111 However, the presence of severe acidosis may depress the action of catecholamines, so the use of sodium bicarbonate may be considered in an acidemic child who is refractory to catecholamine administration.112,113 Acidosis may increase the threshold for myocardial stimulation in a patient with an artificial cardiac pacemaker114; therefore administration of bicarbonate or another buffer is appropriate for management of severe documented acidosis in these children. Administration of sodium bicarbonate also is indicated in the patient with a tricyclic antidepressant overdose, hyperkalemia, hypermagnesemia, or sodium channel blocker poisoning. The buffering action of bicarbonate occurs when a hydrogen cation and a bicarbonate anion combine to form carbon dioxide and water. If carbon dioxide is not effectively cleared through ventilation, its buildup counterbalances the buffering effect of bicarbonate. Because carbon dioxide readily penetrates cell membranes, intracellular acidosis may increase without adequate ventilation. Therefore, bicarbonate should not be used for management of respiratory acidosis.

Unlike sodium bicarbonate, tromethamine (THAM) buffers excess protons without generating carbon dioxide. Carbon dioxide is consumed following THAM administration. In a patient with limited ventilation, tromethamine may be preferable when buffering is necessary. Tromethamine undergoes renal elimination, and renal insufficiency may be a relative contraindication to its use. Carbicarb, an equimolar combination of sodium bicarbonate and sodium carbonate, is another buffering solution that generates less carbon dioxide than sodium bicarbonate. In a canine model of cardiac arrest comparing animals given normal saline, sodium bicarbonate, THAM, or Carbicarb, the animals given any buffer solution had a higher rate of ROSC than the animals given normal saline. In the animals given sodium bicarbonate or Carbicarb, the interval to ROSC was significantly shorter than in animals given normal saline. However, at the end of the 6-hour study period, all resuscitated animals were in a deep coma, so no inferences regarding meaningful survival can be drawn.115 It is premature to recommend either THAM or Carbicarb during CPR at this time.

Postresuscitation Interventions

Temperature Management

Hyperthermia following cardiac arrest is common in children, and fever following cardiac arrest is associated with poor neurologic outcome.116,117 Two seminal articles addressing adult out-of-hospital VF cardiac arrest have established that mild induced hypothermia (32° C to 34° C) is a clinically promising recent goal-directed postresuscitation therapy. In these randomized studies of comatose patients older than 18 years after VF cardiac arrest, outcomes were improved.118,119 However, extrapolation of these findings to the pediatric arrest victim is difficult, as fever, trauma, stroke, and other ischemic conditions, common in pediatric cardiac arrest, are associated with poor neurologic outcome. Emerging neonatal trials of selective brain cooling and systemic cooling show promise in neonatal hypoxic-ischemic encephalopathy, suggesting that induced hypothermia may improve outcomes.120,121 At a minimum, it is advisable to avoid hyperthermia in children following CPR. Using an approach of “therapeutic normothermia” with scheduled administration of antipyretic medications and the use of external cooling devices may be necessary to prevent hyperthermia in this population.

Glucose Control

Both hyperglycemia and hypoglycemia following cardiac arrest are associated with worse neurologic outcome.122125 While it seems intuitive that hypoglycemia would be associated with worse neurologic outcome, whether hyperglycemia per se is harmful or is simply a marker of the severity of the stress hormone response from prolonged ischemia is not clear. In critically ill adult patients, tight glucose control using an insulin infusion was associated with improved survival.126,127 However, subsequent studies of nonsurgical adult populations and neonatal/pediatric trials have demonstrated no survival benefit and/or the potential for harm when rates of inadvertent hypoglycemia were high during treatment.125,128135 Using the available data, there is insufficient evidence to formulate a strong recommendation on the management of hyperglycemia in children with ROSC following cardiac arrest. If hyperglycemia is treated following ROSC in pediatric patients, blood glucose concentrations should be carefully monitored to avoid hypoglycemia.

Blood Pressure Management

Compared with healthy volunteers, adults resuscitated from cardiac arrest have impaired autoregulation of cerebral blood flow.136 Hence they may not maintain adequate cerebral blood flow in the context of low systemic pressure and, likewise, may not be able to protect the brain from excessive blood flow and microvascular perfusion pressure in the context of systemic hypertension. However, in animal models, brief induced hypertension following resuscitation results in improved neurologic outcome compared with normotensive reperfusion.137,138 Therefore, a practical approach to blood pressure management following cardiac arrest is to attempt to minimize blood pressure variability in this high-risk period following resuscitation.

Postresuscitation Myocardial Dysfunction

Postarrest myocardial stunning and arterial hypotension occur commonly after successful resuscitation in both animals and humans.118,119,139146 Animal studies demonstrate that postarrest myocardial stunning is a global phenomenon with biventricular systolic and diastolic dysfunction. This postarrest myocardial stunning is pathophysiologically and physiologically similar to sepsis-related myocardial dysfunction and post–cardiopulmonary bypass myocardial dysfunction, including increases in inflammatory mediators and nitric oxide production.139,141,142,145 Because cardiac function is essential to reperfusion following cardiac arrest, management of postarrest myocardial dysfunction may be important to improving survival. The classes of agents used to maintain circulatory function (i.e., inotropes, vasopressors, and vasodilators) must be carefully titrated during the postresuscitation phase to the patient’s cardiovascular physiology. Trials in animal models have shown that various vasoactive medications can effectively ameliorate postarrest myocardial dysfunction (e.g., dobutamine, milrinone, levosimendan).147151 Similarly, in human observational studies, fluid resuscitation and various vasoactive medications (i.e., epinephrine, dobutamine, and dopamine) have been provided for myocardial dysfunction syndrome.118,119,140144 In the end, optimal use of these agents involves close goal-directed titration, and the use of invasive hemodynamic monitoring may be appropriate.

Other Considerations

Quality of CPR

The quality of healthcare provider CPR during adult resuscitations typically does not comply with American Heart Association clinical practice guidelines. Long CPR-free intervals, shallow chest compressions, incorrect chest compression rates, and overventilation are common.152155 Unfortunately, the quality of CPR performed during the resuscitation attempt is directly related to patient outcome.52,152,156 Studies have shown in adults and in children that patients with a witnessed cardiac arrest4 and those who receive bystander CPR157 have an increased chance of survival. Those that suffer their in-hospital cardiac arrest at night or during weekends (presumably when the quality of resuscitation is not as good as in the daytime or on weekdays) have higher mortality.158 Furthermore, pediatric outcomes are improved in hospitals staffed with highly trained pediatric specific providers.22 Taken all together, these findings establish that the quality of resuscitative care, specifically early high-quality CPR, is an important determinate of patient survival.

In an effort to improve CPR quality, CPR-monitoring defibrillators with audiovisual feedback have been used during adult resuscitation, and improvements in CPR quality and clinical outcomes have been achieved.156,159 In a recent pediatric article, the combination of focused bedside training and automated feedback defibrillators improved CPR guideline compliance of in-hospital providers.154 However, there were still significant portions of the resuscitation that suffered from substandard resuscitative care. Future studies should continue to focus on novel ways to improve pediatric CPR during resuscitation attempts.

Extracorporeal Membrane Oxygenation Cardiopulmonary Resuscitation

Venoarterial extracorporeal membrane oxygenation (ECMO) has been increasingly used as a rescue therapy during CPR, especially for potentially reversible acute postoperative myocardial dysfunction or arrhythmias. Studies of extracorporeal CPR (E-CPR) have demonstrated favorable early survival outcomes in children with primary cardiac disease when E-CPR protocols were in place at the time of the arrest.31,160170 Interestingly, data has been mixed regarding the relationship between outcome and CPR duration before ECMO cannulation. CPR and ECMO are not curative treatments. They are simply cardiopulmonary supportive measures that restore tissue perfusion until recovery from the precipitating disease process is achieved. As such, they can be powerful tools. Thus E-CPR should be considered for children with cardiac arrest who have heart disease amenable to recovery or transplantation, if the arrest occurs in a highly supervised environment such as an intensive care unit with existing clinical protocols and available expertise and equipment to rapidly initiate extracorporeal life support (ECLS).

Ventricular Fibrillation and Ventricular Tachycardia in Children

Pediatric VF or VT has been an underappreciated pediatric problem. Recent studies indicate that VF and VT (i.e., shockable rhythms) occur in 27% of in-hospital cardiac arrests at some time during the resuscitation.28 In a population of pediatric cardiac intensive care unit patients, as many as 41% of arrests were associated with VF or VT.24 According to the National Registry of Cardiopulmonary Resuscitation (NRCPR) database, during in-hospital arrest, 10% of children had an initial rhythm of VF/VT. In all, 27% of the children had VF/VT at some time during the resuscitation.28 The incidence of VF varies by setting and age.171 In special circumstances, such as tricyclic antidepressant overdose, cardiomyopathy, status post–cardiac surgery, and prolonged QT syndromes, VF and pulseless VT are more likely.

The treatment of choice for short-duration VF is prompt defibrillation. In general, the mortality rate increases by 7% to 10% per minute of delay to defibrillation. Because VF must be considered before defibrillation can be provided, early determination of the rhythm by electrocardiography is critical. An attitude that VF is rare in children can be a self-fulfilling prophecy with a uniformly fatal outcome. The recommended defibrillation dose is 2 J/kg, but the data supporting this recommendation are not optimal and are based on old monophasic defibrillators. In the mid-1970s, authoritative sources recommended starting doses of 60 to 200 J for all children. Because of concerns for myocardial damage and animal data suggesting that shock doses ranging from 0.5 to 1 J/kg were adequate for defibrillation in a variety of species, Gutgesell et al. evaluated the efficacy of their strategy to defibrillate with 2 J/kg monophasic shocks. Seventy-one transthoracic defibrillations in 27 children were evaluated. Shocks within 10 J of 2 J/kg resulted in successful defibrillation in 91% of defibrillation attempts. The major determinant of successful defibrillation other than VF duration is countershock current. This current depends on the defibrillator energy and transthoracic impedance. Studies in children indicate that the transthoracic impedance of infants and children greatly overlap. Although there is a statistically significant correlation between size and transthoracic impedance, the correlation is weak. These studies provide only weak support for the present dogma that the defibrillator energy dose should vary directly with weight. Nevertheless, the present recommendation of 2 J/kg has stood the test of time.

Although the limited data regarding pediatric defibrillation used monophasic waveform shocks, most new defibrillators use biphasic waveform shocks. Defibrillation with these biphasic waveforms apparently is safer and more effective than monophasic waveform defibrillation. Therefore the use of 2 J/kg biphasic waveform shocks should be at least as effective as 2 J/kg monophasic shocks and possibly safer.

Antiarrhythmic Medications: Lidocaine and Amiodarone

Administration of antiarrhythmic medications should never delay administration of shocks to a patient with VF. However, after an unsuccessful attempt at electrical defibrillation, medications to increase the effectiveness of defibrillation should be considered. Epinephrine is the current first-line medication for both pediatric and adult patients in VF. If epinephrine and a subsequent repeat attempt to defibrillate are unsuccessful, lidocaine or amiodarone should be considered.

Lidocaine traditionally has been recommended for shock-resistant VF in adults and children. However, only amiodarone improved survival to hospital admission in the setting of shock-resistant VF compared with placebo.172 In another study of shock-resistant out-of-hospital VF, patients receiving amiodarone had a higher rate of survival to hospital admission than patients receiving lidocaine.173 Neither study included children. Because there is moderate experience with amiodarone use as an antiarrhythmic agent in children and because of the adult studies, it is rational to use amiodarone similarly in children with shock-resistant VF/VT. The recommended dosage is 5 mg/kg by rapid intravenous bolus. There are no published comparisons of antiarrhythmic medications for pediatric refractory VF. Although extrapolation of adult data and electrophysiologic mechanistic information suggest that amiodarone may be preferable for pediatric shock-resistant VF, the optimal choice is not clear.

Pediatric Automated External Defibrillators

Automated external defibrillators (AEDs) have improved adult survival from VF.174,175 AEDs are recommended for use in children 8 years or older with cardiac arrest.176,177 The available data suggest that some AEDs can accurately diagnose VF in children of all ages, but many AEDs are limited because the defibrillation pads and energy dosage are geared for adults. Adapters having smaller defibrillation pads that dampen the amount of energy delivered have been developed as attachments to adult AEDs, allowing their use in children. However, it is important that the AED diagnostic algorithm is sensitive and specific for pediatric VF and VT. The diagnostic algorithms from several AED manufacturers have been tested for such sensitivity and specificity and therefore can be reasonably used in younger children.

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