The use of pressure-controlled mechanical ventilation in a swine model of intraoperative pediatric cardiac arrest.

BACKGROUND: Current pediatric resuscitation guidelines suggest that resuscitators using an advanced airway deliver 8-10 breaths per minute while carefully avoiding excessive ventilation. In the intraoperative setting, having a dedicated ventilation rescuer may be difficult because of limited personnel. Continuing pressure-controlled mechanical ventilation during resuscitation for intraoperative cardiac arrest reduces personnel needed and the risk of hyperventilation but might risk hypoventilation during chest compression delivery. AIMS: To determine whether the use of pressure-controlled mechanical ventilation at prearrest settings provides normoxia and normocarbia during resuscitation from cardiac arrest. METHODS: We retrospectively analyzed combined data from preclinical randomized controlled trials. Two-week-old swine (3-4 kg) underwent asphyxia-induced cardiac arrest. Animals were resuscitated with periods of basic and advanced life support. During resuscitation, pressure-controlled mechanical ventilation was delivered at the prearrest respiratory rate, peak inspiratory pressure, and positive end-expiratory pressure. Arterial blood gases were measured prearrest, at 11 minutes of asphyxia, and at 8 and 20 minutes of cardiopulmonary resuscitation. RESULTS: Piglets (n = 154) received pressure-controlled mechanical ventilation before and during cardiopulmonary resuscitation with a peak inspiratory pressure of 14-15 cm H2 O, positive end-expiratory pressure of 4 cm H2 O, 20 breaths/minute, and an inspiratory:expiratory ratio of 1:2. During asphyxia, the arterial blood gas showed the expected severe hypercarbia and hypoxia. Continuing pressure-controlled mechanical ventilation using prearrest parameters and increasing the FiO2 to 1.0 returned the PaCO2 to prearrest levels and slightly increased the partial pressure of arterial oxygen at 8 and 20 minutes of cardiopulmonary resuscitation. CONCLUSION: In this piglet model of resuscitation from asphyxial arrest, pressure-controlled mechanical ventilation during cardiopulmonary resuscitation at the prearrest ventilator settings with an FiO2 of 1.0 provides adequate oxygenation and restores normocarbia. Clinical investigation is warranted to determine the benefits of continuing pressure-controlled mechanical ventilation at prearrest parameters during pediatric cardiopulmonary resuscitation.

A National Survey on Interhospital Transport of Children in Cardiac Arrest.

OBJECTIVES: To describe the U.S. experience with interhospital transport of children in cardiac arrest undergoing cardiopulmonary resuscitation. DESIGN: Self-administered electronic survey. SETTING: Pediatric transport teams listed with the American Academy of Pediatrics Section on Transport Medicine. SUBJECTS: Leaders of U.S. pediatric transport teams. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Sixty of the 88 teams surveyed (68%) responded. Nineteen teams (32%) from 13 states transport children undergoing cardiopulmonary resuscitation between hospitals. The most common reasons for transfer of children in cardiac arrest are higher level-of-care (70%), extracorporeal life support (60%), and advanced trauma resuscitation (35%). Eligibility is typically decided on a case-by-case basis (85%) and sometimes involves a short interhospital distance (35%), or prompt institution of high-quality cardiopulmonary resuscitation (20%). Of the 19 teams that transport with ongoing cardiopulmonary resuscitation, 42% report no special staff safety features, 42% have guidelines or protocols, 37% train staff on resuscitation during transport, 11% brace with another provider, and 5% use mechanical cardiopulmonary resuscitation devices for patients less than 18 years. In the past 5 years, 18 teams report having done such cardiopulmonary resuscitation transports: 22% did greater than five transports, 44% did two to five transports, 6% did one transport, and the remaining 28% did not recall the number of transports. Seventy-eight percent recall having transported by ambulance, 44% by helicopter, and 22% by fixed-wing. Although patient outcomes were varied, eight teams (44%) reported survivors to ICU and/or hospital discharge. CONCLUSIONS: A minority of U.S. teams perform interhospital transport of children in cardiac arrest undergoing cardiopulmonary resuscitation. Eligibility criteria, transport logistics, and patient outcomes are heterogeneous. Importantly, there is a paucity of established safety protocols for the staff performing cardiopulmonary resuscitation in transport.

The Effect of Asphyxia Arrest Duration on a Pediatric End-Tidal CO2-Guided Chest Compression Delivery Model.

OBJECTIVES: To determine the effect of the duration of asphyxial arrest on the survival benefit previously seen with end-tidal CO2-guided chest compression delivery. DESIGN: Preclinical randomized controlled study. SETTING: University animal research laboratory. SUBJECTS: Two-week-old swine. INTERVENTIONS: After either 17 or 23 minutes of asphyxial arrest, animals were randomized to standard cardiopulmonary resuscitation or end-tidal CO2-guided chest compression delivery. Standard cardiopulmonary resuscitation was optimized by marker, monitor, and verbal feedback about compression rate, depth, and release. End-tidal CO2-guided delivery used adjustments to chest compression rate and depth to maximize end-tidal CO2 level without other feedback. Cardiopulmonary resuscitation for both groups proceeded from 10 minutes of basic life support to 10 minutes of advanced life support or return of spontaneous circulation. MEASUREMENTS AND MAIN RESULTS: After 17 minutes of asphyxial arrest, mean end-tidal CO2 during 10 minutes of cardiopulmonary resuscitation was 18 ± 9 torr in the standard group and 33 ± 15 torr in the end-tidal CO2 group (p = 0.004). The rate of return of spontaneous circulation was three of 14 (21%) in the standard group rate and nine of 14 (64%) in the end-tidal CO2 group (p = 0.05). After a 23-minute asphyxial arrest, neither end-tidal CO2 values (20 vs 26) nor return of spontaneous circulation rate (3/14 vs 1/14) differed between the standard and end-tidal CO2-guided groups. CONCLUSIONS: Our previously observed survival benefit of end-tidal CO2-guided chest compression delivery after 20 minutes of asphyxial arrest was confirmed after 17 minutes of asphyxial arrest. The poor survival after 23 minutes of asphyxia shows that the benefit of end-tidal CO2-guided chest compression delivery is limited by severe asphyxia duration.

End-Tidal CO2-Guided Chest Compression Delivery Improves Survival in a Neonatal Asphyxial Cardiac Arrest Model.

OBJECTIVES: To determine whether end-tidal CO2-guided chest compression delivery improves survival over standard cardiopulmonary resuscitation after prolonged asphyxial arrest. DESIGN: Preclinical randomized controlled study. SETTING: University animal research laboratory. SUBJECTS: 1-2-week-old swine. INTERVENTIONS: After undergoing a 20-minute asphyxial arrest, animals received either standard or end-tidal CO2-guided cardiopulmonary resuscitation. In the standard group, chest compression delivery was optimized by video and verbal feedback to maintain the rate, depth, and release within published guidelines. In the end-tidal CO2-guided group, chest compression rate and depth were adjusted to obtain a maximal end-tidal CO2 level without other feedback. Cardiopulmonary resuscitation included 10 minutes of basic life support followed by advanced life support for 10 minutes or until return of spontaneous circulation. MEASUREMENTS AND MAIN RESULTS: Mean end-tidal CO2 at 10 minutes of cardiopulmonary resuscitation was 34 ± 8 torr in the end-tidal CO2 group (n = 14) and 19 ± 9 torr in the standard group (n = 14; p = 0.0001). The return of spontaneous circulation rate was 7 of 14 (50%) in the end-tidal CO2 group and 2 of 14 (14%) in the standard group (p = 0.04). The chest compression rate averaged 143 ± 10/min in the end-tidal CO2 group and 102 ± 2/min in the standard group (p < 0.0001). Neither asphyxia-related hypercarbia nor epinephrine administration confounded the use of end-tidal CO2-guided chest compression delivery. The response of the relaxation arterial pressure and cerebral perfusion pressure to the initial epinephrine administration was greater in the end-tidal CO2 group than in the standard group (p = 0.01 and p = 0.03, respectively). The prevalence of resuscitation-related injuries was similar between groups. CONCLUSIONS: End-tidal CO2-guided chest compression delivery is an effective resuscitation method that improves early survival after prolonged asphyxial arrest in this neonatal piglet model. Optimizing end-tidal CO2 levels during cardiopulmonary resuscitation required that chest compression delivery rate exceed current guidelines. The use of physiologic feedback during cardiopulmonary resuscitation has the potential to provide optimized and individualized resuscitative efforts.

Early oxygenation and ventilation measurements after pediatric cardiac arrest: lack of association with outcome.

OBJECTIVES: To explore oxygenation and ventilation status early after cardiac arrest in infants and children. We hypothesize that hyperoxia is common and associated with worse outcome after pediatric cardiac arrest. DESIGN: Retrospective cohort study. SETTING: Fifteen hospitals within the Pediatric Emergency Care Applied Research Network. PATIENTS: Children who suffered a cardiac arrest event and survived for at least 6 hours after return of circulation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Analysis of 195 events revealed that abnormalities in oxygenation and ventilation are common during the initial 6 hours after pediatric cardiac arrest. Hyperoxia was frequent, affecting 54% of patients. Normoxia was documented in 34% and hypoxia in 22% of patients. These percentages account for a 10% overlap of patients who had both hyperoxia and hypoxia. Ventilation status was more evenly distributed with hyperventilation observed in 38%, normoventilation in 29%, and hypoventilation in 46%, with a 13% overlap of patients who had both hyperventilation and hypoventilation. Derangements in both oxygenation and ventilation were common early after cardiac arrest such that both normoxia and normocarbia were documented in only 25 patients (13%). Neither oxygenation nor ventilation status was associated with outcome. After controlling for potential confounders, arrest location and rhythm were significantly associated with worse outcome; however, hyperoxia was not (odds ratio for good outcome, 1.02 [0.46, 2.84]; p = 0.96). CONCLUSIONS: Despite recent resuscitation guidelines that advocate maintenance of normoxia and normoventilation after pediatric cardiac arrest, this is uncommonly achieved in practice. Although we did not demonstrate an association between hyperoxia and worse outcome, the small proportion of patients kept within normal ranges limited our power. Preclinical data suggesting potential harm with hyperoxia remain compelling, and further investigation, including prospective, large studies involving robust recording of physiological derangements, is necessary to further advance our understanding of this important topic.

Pediatric perioperative life support.

Pediatric advanced life support training and guidelines are typically designed for first-responders and out-of-hospital resuscitation. Guidelines and scenarios that are more applicable to the perioperative environment would be beneficial for anesthesiologists. The goal of this article is to review resuscitation of pediatric patients during the perioperative period. We use a format that focuses on preresuscitation preparation, resuscitation techniques, and postresuscitation management in the perioperative period. In an effort to provide information of maximum benefit to anesthesiologists, we include common pediatric perioperative arrest scenarios with detailed description of their management. We also provide a section on postresuscitation management and review the techniques for maintaining the child's hemodynamic and metabolic stability. Finally, 3 appendices are included: an example of an intraoperative arrest record that provides feedback for interventions; a table of key medications for pediatric perioperative resuscitation; and a review of defibrillator use and simulation exercises to promote effective defibrillation.

Noninvasive autoregulation monitoring in a swine model of pediatric cardiac arrest.

BACKGROUND: Cerebrovascular autoregulation after resuscitation has not been well studied in an experimental model of pediatric cardiac arrest. Furthermore, developing noninvasive methods of monitoring autoregulation using near-infrared spectroscopy (NIRS) would be clinically useful in guiding neuroprotective hemodynamic management after pediatric cardiac arrest. We tested the hypotheses that the lower limit of autoregulation (LLA) would shift to a higher arterial blood pressure between 1 and 2 days of recovery after cardiac arrest and that the LLA would be detected by NIRS-derived indices of autoregulation in a swine model of pediatric cardiac arrest. We also tested the hypothesis that autoregulation with hypertension would be impaired after cardiac arrest. METHODS: Data on LLA were obtained from neonatal piglets that had undergone hypoxic-asphyxic cardiac arrest and recovery for 1 day (n = 8) or 2 days (n = 8), or that had undergone sham surgery with 2 days of recovery (n = 8). Autoregulation with hypertension was examined in a separate cohort of piglets that underwent hypoxic-asphyxic cardiac arrest (n = 5) or sham surgery (n = 5) with 2 days of recovery. After the recovery period, piglets were reanesthetized, and autoregulation was monitored by standard laser-Doppler flowmetry and autoregulation indices derived from NIRS (the cerebral oximetry [COx] and hemoglobin volume [HVx] indices). The LLA was determined by decreasing blood pressure through inflation of a balloon catheter in the inferior vena cava. Autoregulation during hypertension was evaluated by inflation of an aortic balloon catheter. RESULTS: The LLAs were similar between sham-operated piglets and piglets that recovered for 1 or 2 days after arrest. The NIRS-derived indices accurately detected the LLA determined by laser-Doppler flowmetry. The area under the curve of the receiver operator characteristic curve for cerebral oximetry index was 0.91 at 1 day and 0.92 at 2 days after arrest. The area under the curve for hemoglobin volume index was 0.92 and 0.89 at the respective time points. During induced hypertension, the static rate of autoregulation, defined as the percentage change in cerebrovascular resistance divided by the percentage change in cerebral perfusion pressure, was not different between postarrest and sham-operated piglets. At 2 days recovery from arrest, piglets exhibited neurobehavioral deficits and histologic neuronal injury. CONCLUSIONS: In a swine model of pediatric hypoxic-asphyxic cardiac arrest with confirmed brain damage, the LLA did not differ 1 and 2 days after resuscitation. The NIRS-derived indices accurately detected the LLA in comparison with laser-Doppler flow measurements at those time points. Autoregulation remained functional during hypertension.

Association of end-tidal carbon dioxide levels during cardiopulmonary resuscitation with survival in a large paediatric cohort.

AIM: To examine the associations between ETCO2, ROSC, and chest compression quality markers in paediatric patients during active resuscitation. METHODS: This was a single-centre cohort study of data collected as part of an institutional prospective quality initiative improvement program that included all paediatric patients who received chest compressions of any duration from January 1, 2013, through July 10, 2018, in the Johns Hopkins Children's Center. Data was collected from Zoll R Series® defibrillators. Events were included if Zoll data files contained both chest compression and ETCO2 data. 2,746 minutes corresponding to 143 events were included in the analyses. RESULTS: The median event ETCO2 for all 143 events was 16.8 [9.3-26.3] mmHg. There was a significant difference in median event ETCO2 between events that achieved ROSC and those that did not (ROSC: 19.3 [14.4-26.6] vs. NO ROSC: 13.9 [6.6-25.5] mmHg; p < 0.05). When the events were based on patient age, this relationship held in adolescents (ROSC: 18.8 [15.5-22.3] vs. NO ROSC: 9.6 [4.4-15.9] mmHg; p < 0.05), but not in children or infants. Median event ETCO2 was significantly associated with chest compression rate less than 140 (p < 0.0001) and chest compression fraction 90-100 (p < 0.0001). CONCLUSIONS: This represents the largest collection of ETCO2 and chest compression data in paediatric patients to date and unadjusted analyses suggests an association between ETCO2 and ROSC in some paediatric patients.

Cerebral blood flow and cerebrovascular autoregulation in a swine model of pediatric cardiac arrest and hypothermia.

OBJECTIVE: Knowledge remains limited regarding cerebral blood flow autoregulation after cardiac arrest and during postresuscitation hypothermia. We determined the relationship of cerebral blood flow to cerebral perfusion pressure in a swine model of pediatric hypoxic-asphyxic cardiac arrest during normothermia and hypothermia and tested novel measures of autoregulation derived from near-infrared spectroscopy. DESIGN: Prospective, balanced animal study. SETTING: Basic physiology laboratory at an academic institution. SUBJECTS: Eighty-four neonatal swine. INTERVENTIONS: Piglets underwent hypoxic-asphyxic cardiac arrest or sham surgery and recovered for 2 hrs with normothermia followed by 4 hrs of either moderate hypothermia or normothermia. In half of the groups, blood pressure was slowly decreased through inflation of a balloon catheter in the inferior vena cava to identify the lower limit of cerebral autoregulation at 6 hrs postresuscitation. In the remaining groups, blood pressure was gradually increased by inflation of a balloon catheter in the aorta to determine the autoregulatory response to hypertension. Measures of autoregulation obtained from standard laser-Doppler flowmetry and indices derived from near-infrared spectroscopy were compared. MEASUREMENTS AND MAIN RESULTS: Laser-Doppler flux was lower in postarrest animals compared to sham-operated controls during the 2-hr normothermic period after resuscitation. During the subsequent 4-hr recovery, hypothermia decreased laser-Doppler flux in both the sham surgery and postarrest groups. Autoregulation was intact during hypertension in all groups. With arterial hypotension, postarrest, hypothermic piglets had a significant decrease in the perfusion pressure lower limit of autoregulation compared to postarrest, normothermic piglets. The near-infrared spectroscopy-derived measures of autoregulation accurately detected loss of autoregulation during hypotension. CONCLUSIONS: In a pediatric model of cardiac arrest and resuscitation, delayed induction of hypothermia decreased cerebral perfusion and decreased the lower limit of autoregulation. Metrics derived from noninvasive near-infrared spectroscopy accurately identified the lower limit of autoregulation during normothermia and hypothermia in piglets resuscitated from arrest.

Multicenter cohort study of out-of-hospital pediatric cardiac arrest.

OBJECTIVES: To describe a large cohort of children with out-of-hospital cardiac arrest with return of circulation and to identify factors in the early postarrest period associated with survival. These objectives were for planning an interventional trial of therapeutic hypothermia after pediatric cardiac arrest. METHODS: A retrospective cohort study was conducted at 15 Pediatric Emergency Care Applied Research Network clinical sites over an 18-month study period. All children from 1 day (24 hrs) to 18 yrs of age with out-of-hospital cardiac arrest and a history of at least 1 min of chest compressions with return of circulation for at least 20 mins were eligible. MEASUREMENTS AND MAIN RESULTS: One hundred thirty-eight cases met study entry criteria; the overall mortality was 62% (85 of 138 cases). The event characteristics associated with increased survival were as follows: weekend arrests, cardiopulmonary resuscitation not ongoing at hospital arrival, arrest rhythm not asystole, no atropine or NaHCO3, fewer epinephrine doses, shorter duration of cardiopulmonary resuscitation, and drowning or asphyxial arrest event. For the 0- to 12-hr postarrest return-of-circulation period, absence of any vasopressor or inotropic agent (dopamine, epinephrine) use, higher lowest temperature recorded, greater lowest pH, lower lactate, lower maximum glucose, and normal pupillary responses were all associated with survival. A multivariate logistic model of variables available at the time of arrest, which controlled for gender, age, race, and asystole or ventricular fibrillation/ventricular tachycardia anytime during the arrest, found the administration of atropine and epinephrine to be associated with mortality. A second model using additional information available up to 12 hrs after return of circulation found 1) preexisting lung or airway disease; 2) an etiology of arrest drowning or asphyxia; 3) higher pH, and 4) bilateral reactive pupils to be associated with lower mortality. Receiving more than three doses of epinephrine was associated with poor outcome in 96% (44 of 46) of cases. CONCLUSIONS: Multiple factors were identified as associated with survival after out-of-hospital pediatric cardiac arrest with the return of circulation. Additional information available within a few hours after the return of circulation may diminish outcome associations of factors available at earlier times in regression models. These factors should be considered in the design of future interventional trials aimed to improve outcome after pediatric cardiac arrest.