Selected Concepts and Controversies in Pediatric Cardiopulmonary Resuscitation

Epinephrine improves 24-hour survival in a swine model of prolonged ventricular fibrillation demonstrating that early intraosseous is superior to delayed intravenous administration

BACKGROUND

Vasopressors administered IV late during resuscitation efforts fail to improve survival. Intraosseous (IO) access can provide a route for earlier administration. We hypothesized that IO epinephrine after 1 minute of cardiopulmonary resuscitation (CPR) (an "optimal" IO scenario) after 10 minutes of untreated ventricular fibrillation (VF) cardiac arrest would improve outcome in comparison with either IV epinephrine after 8 minutes of CPR (a "realistic" IV scenario) or placebo controls with no epinephrine.

METHODS

Thirty swine were randomized to IO epinephrine, IV epinephrine, or placebo. Important outcomes included return of spontaneous circulation (ROSC), 24-hour survival, and 24-hour survival with good neurological outcome (cerebral performance category 1).

RESULTS

ROSC after 10 minutes of untreated VF was uncommon without administration of epinephrine (1 of 10), whereas ROSC was nearly universal with IO epinephrine or delayed IV epinephrine (10 of 10 and 9 of 10, respectively; P = 0.001 for either versus placebo). Twenty-four hour survival was substantially more likely after IO epinephrine than after delayed IV epinephrine (10 of 10 vs. 4 of 10, P = 0.001). None of the placebo group survived at 24 hours. Survival with good neurological outcome was more likely after IO epinephrine than after placebo (6 of 10 vs. 0 of 10, P = 0.011), and only 3 of 10 survived with good neurological outcome in the delayed IV epinephrine group (not significant versus either IO or placebo).

CONCLUSION

In this swine model of prolonged VF cardiac arrest, epinephrine administration during CPR improved outcomes. In addition, early IO epinephrine improved outcomes in comparison with delayed IV epinephrine.

The use of high-dose epinephrine for patients with out-of-hospital cardiopulmonary arrest refractory to prehospital interventions

OBJECTIVE

To determine if high-dose epinephrine (HDE) used during out-of-hospital cardiopulmonary arrest refractory to prehospital interventions improves return of spontaneous circulation, 24-hour survival, discharge survival, and neurological outcomes.

METHODS

A multicenter randomized controlled trial was conducted between May 1991 and October 1996 to compare the effectiveness of HDE versus standard-dose epinephrine (SDE) in patients having out-of-hospital cardiopulmonary arrest refractory to prehospital resuscitation efforts. Cardiopulmonary arrest was classified as "medical" or "traumatic." Two hundred thirty patients were enrolled in 7 pediatric emergency departments. Ages ranged from newborn to 22 years. Seventeen patients met exclusion criteria. Patients were assigned to receive HDE (0.1 mg/kg for the initial dose and 0.2 mg/kg for subsequent doses) or SDE (0.01 mg/kg). The main end points evaluated were return of spontaneous circulation, 24-hour survival, discharge survival, and neurological outcome.

RESULTS

One hundred twenty-seven patients received HDE (32 trauma patients), and 86 patients received SDE (27 trauma patients). Among medical patients, 24 (25%) of 95 experienced return of spontaneous circulation in the HDE group as compared with 9 (15%) of 59 in the SDE group (P = 0.14, chi2 = 2.17, relative risk = 1.66 [0.83-3.31]). Sixteen (17%) of 95 HDE patients and 5 (8%) of 59 SDE patients survived at least 24 hours (P = 0.14, chi2 = 2.16, relative risk = 1.99 [0.77-5.14]). Nine survivors to discharge received HDE, and 2 received SDE (P = 0.21, Fisher exact test, relative risk = 2.75 [0.61-12.28]). There were no long-term survivors among the trauma patients. Eight of 11 long-term survivors had severe neurological outcomes defined by the Glasgow Outcome Scale (2/2 SDE, 6/9 HDE; P = 0.51, Fisher exact test).

CONCLUSION

HDE does not improve or diminish return of spontaneous circulation, 24-hour survival, long-term survival, or neurological outcome compared with SDE in out-of-hospital cardiopulmonary arrest.

Pediatric Post-resuscitation Care

Current literature demonstrates a paucity of information on post-resuscitation care of pediatric clients. This lack of information is somewhat understandable in light of the relatively low incidence of occurrence and the statistically poor outcome. Nurses must be aware, however, of many issues when dealing with pediatric clients and their families after an arrest episode. This article explores key concepts involved with post-resuscitation care, including the outcome of cardiopulmonary resuscitation, immediate post-resuscitation needs, emotional outcomes for the child, and family stress and grief.

Comparison of epinephrine with vasopressin on bone marrow blood flow in an animal model of hypovolemic shock and subsequent cardiac arrest

OBJECTIVE

The intraosseous route is an emergency alternative for the administration of drugs and fluids if vascular access cannot be established. However, in hemorrhagic shock or after vasopressors are given during resuscitation, bone marrow blood flow may be decreased, thus impairing absorption of intraosseously administered drugs. In this study, we evaluated the effects of vasopressin vs. high-dose epinephrine in hemorrhagic shock and cardiac arrest on bone marrow blood flow.

DESIGN

Prospective, randomized laboratory investigation that used an established porcine model for measurement of hemodynamic variables and organ blood flow.

SETTING

University hospital laboratory.

SUBJECTS

Fourteen pigs weighing 30 +/- 3 kg.

INTERVENTIONS

Radiolabeled microspheres were injected to measure bone marrow blood flow during a prearrest control period and during hypovolemic shock produced by rapid hemorrhage of 35% of the estimated blood volume. In the second part of the study, ventricular fibrillation was induced; after 4 mins of untreated cardiac arrest and 4 mins of standard cardiopulmonary resuscitation, a bolus dose of either 200 microg/kg epinephrine (n = 6) or 0.8 units/kg vasopressin (n = 6) was administered. Defibrillation was attempted 2.5 mins after drug administration, and blood flow was assessed again at 5 and 30 mins after successful resuscitation.

MEASUREMENTS AND MAIN RESULTS

Mean +/- sem bone marrow blood flow decreased significantly during induction of hemorrhagic shock from 14.4 +/- 4.1 to 3.7 +/- 1.8 mL.100 g-1.min-1 in the vasopressin group and from 18.2 +/- 4.0 to 5.2 +/- 1.0 mL.100 g-1.min-1 in the epinephrine group (p =.025 in both groups). Five minutes after return of spontaneous circulation, mean +/- sem bone marrow blood flow was 3.4 +/- 1.1 mL.100 g-1.min-1 after vasopressin and 0.1 +/- 0.03 mL.100 g-1.min-1 after epinephrine (p =.004 for vasopressin vs. epinephrine). At the same time, bone vascular resistance was significantly (p =.004) higher in the epinephrine group when compared with vasopressin (1455 +/- 392 vs. 43 +/- 19 mm Hg. mL-1.100 g.min, respectively).

CONCLUSIONS

Bone blood flow responds actively to both the physiologic stress response of hemorrhagic shock and vasopressors given during resuscitation after hypovolemic cardiac arrest. In this regard, bone marrow blood flow after successful resuscitation was nearly absent after high-dose epinephrine but was maintained after high-dose vasopressin. These findings emphasize the need for pressurized intraosseous infusion techniques, because bone marrow blood flow may not be predictable during hemorrhagic shock and drug therapy.

Comparison of epinephrine and vasopressin in a pediatric porcine model of asphyxial cardiac arrest

OBJECTIVE

This study was designed to compare the effects of vasopressin vs. epinephrine vs. the combination of epinephrine with vasopressin on vital organ blood flow and return of spontaneous circulation in a pediatric porcine model of asphyxial arrest.

DESIGN

Prospective, randomized laboratory investigation using an established porcine model for measurement of hemodynamic variables, organ blood flow, blood gases, and return of spontaneous circulation.

SETTING

University hospital laboratory.

SUBJECTS

Eighteen piglets weighing 8-11 kg.

INTERVENTIONS

Asphyxial cardiac arrest was induced by clamping the endotracheal tube. After 8 mins of cardiac arrest and 8 mins of cardiopulmonary resuscitation, a bolus dose of either 0.8 units/kg vasopressin (n = 6), 200 microg/kg epinephrine (n = 6), or a combination of 45 microg/kg epinephrine with 0.8 units/kg vasopressin (n = 6) was administered in a randomized manner. Defibrillation was attempted 6 mins after drug administration.

MEASUREMENTS AND MAIN RESULTS

Mean +/- SEM coronary perfusion pressure, before and 2 mins after drug administration, was 13 +/- 2 and 23 +/- 6 mm Hg in the vasopressin group; 14 +/- 2 and 31 +/- 4 mm Hg in the epinephrine group; and 13 +/- 1 and 33 +/- 6 mm Hg in the epinephrine-vasopressin group, respectively (p = NS). At the same time points, mean +/- SEM left ventricular myocardial blood flow was 44 +/- 31 and 44 +/- 25 mL x min-(1) x 100 g(-1) in the vasopressin group; 30 +/- 18 and 233 +/- 61 mL x min(-1) x 100 g(-1) in the epinephrine group; and 36 +/- 10 and 142 +/- 57 mL x min(-1) x 100 g(-1) in the epinephrine-vasopressin group (p < .01 epinephrine vs. vasopressin; p < .02 epinephrine-vasopressin vs. vasopressin). Total cerebral blood flow trended toward higher values after epinephrine-vasopressin (60 +/- 19 mL x min(-1) x 100 g(-1)) than after vasopressin (36 +/- 17 mL x min(-1) x 100 g(-1)) or epinephrine alone (31 +/- 7 mL x min(-1) x 100 g(-1); p = .07, respectively). One of six vasopressin, six of six epinephrine, and four of six epinephrine-vasopressin-treated animals had return of spontaneous circulation (p < .01, vasopressin vs. epinephrine).

CONCLUSIONS

Administration of epinephrine, either alone or in combination with vasopressin, significantly improved left ventricular myocardial blood flow during cardiopulmonary resuscitation. Return of spontaneous circulation was significantly more likely in epinephrine-treated pigs than in animals resuscitated with vasopressin alone.

Acid-base status of blood from intraosseous and mixed venous sites during prolonged cardiopulmonary resuscitation and drug infusions

OBJECTIVES

a) To determine the relationship of acid-base balance (pH, PCO2) of blood samples from the intraosseous and the mixed venous route during prolonged cardiopulmonary resuscitation; b) to compare the effect of separate infusions of epinephrine, fluid boluses, or sodium bicarbonate through the intraosseous sites on the acid-base status of intraosseous and mixed venous blood during cardiopulmonary resuscitation; and c) to compare pH and Pco2 of intraosseous and mixed venous blood samples after sequential infusions of fluid, epinephrine, and sodium bicarbonate through a single intraosseous site.

DESIGN

Prospective, randomized study.

SETTING

Animal laboratory at a university center.

SUBJECTS

Thirty-two mixed-breed piglets (mean weight, 30 kg).

INTERVENTIONS

Piglets were anesthetized and prepared for blood sampling and cardiopulmonary resuscitation. After anoxic cardiac arrest, ventilation was resumed and chest compression was resumed. Blood gas samples from the pulmonary artery and both intraosseous sites were obtained simultaneously at baseline, at cardiac arrest, and at 5, 10, 15, 20, and 30 mins of cardiopulmonary resuscitation for group 1 (control group) and after drug (epinephrine and sodium bicarbonate) and saline infusions via one of the intraosseous cannulas in groups 2 through 5.

MEASUREMENTS AND MAIN RESULTS

We found no differences between intraosseous and mixed venous pH and Pco2 during periods of <15 mins of cardiopulmonary resuscitation. However, this relationship was not maintained during prolonged cardiopulmonary resuscitation and after bicarbonate infusion. After large volume saline infusion, the pH and Pco2 of mixed venous and intraosseous blood were similar. During epinephrine infusion, the relationship between intraosseous and mixed venous pH and Pco2 was similar to that found in the control group.

CONCLUSIONS

The intraosseous blood sample could be used to assess central acid-base balance in the early stage of arrest and cardiopulmonary resuscitation of <15 mins. However, during cardiopulmonary resuscitation of longer duration, drug infusions may render the intraosseous site inappropriate for judging central acidosis.

Out-of-hospital ventricular fibrillation in children and adolescents: causes and outcomes

STUDY OBJECTIVE

To compare causes and outcomes of patients younger than 20 years with an initial rhythm of ventricular fibrillation versus asystole and pulseless electrical activity.

DESIGN

Retrospective cohort study.

SETTING

Urban/suburban prehospital system.

PARTICIPANTS

Pulseless, nonbreathing patients less than 20 years who underwent out-of-hospital resuscitation. Patients with lividity or rigor mortis or who were less than 6 months old and died of sudden infant death syndrome were excluded.

RESULTS

Ventricular fibrillation was the initial rhythm in 19% (29 of 157) of the cardiac arrests. Rhythm assessment was performed by the first responder in only 44% (69 of 157) of patients. All three rhythm groups were similar in age distribution, frequency of intubation (96%), and vascular access (92%); 93% of ventricular fibrillation patients were defibrillated. The causes of ventricular fibrillation were distributed evenly among medical illnesses, overdoses, drownings, and trauma, only two patients had congenital heart defects. Seventeen percent were discharged with no or mild disability, compared with 2% of asystole/pulseless electrical activity patients (P = .003).

CONCLUSION

Ventricular fibrillation is not rare in child and adolescent prehospital cardiac arrest, and these patients have a better outcome than those with asystole or pulseless electrical activity. Earlier recognition and treatment of ventricular fibrillation might improve pediatric cardiac arrest survival rates.

Sodium bicarbonate may improve outcome in dogs with brief or prolonged cardiac arrest

OBJECTIVE

Despite the absence of outcome evaluation, the use of sodium bicarbonate in cardiac arrest has declined based on advanced cardiac life-support guidelines. The effects of bicarbonate therapy on outcome in a canine model of ventricular fibrillation cardiac arrest of brief (5-min) and prolonged (15-min) duration were examined.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Experimental animal laboratory in a university medical center.

SUBJECTS

Thirty-two adult dogs, weighing 10 to 17 kg.

INTERVENTIONS

The animals were prepared with ketamine, nitrous oxide/oxygen, halothane, and pancuronium. Ventricular fibrillation was then electrically induced and maintained in arrest for 5 mins (n = 12) or 15 mins (n = 20). Canine advanced cardiac life-support protocols were instituted, including defibrillation, cardiopulmonary resuscitation (CPR), and the administration of epinephrine (0.1 mg/kg), atropine, and lidocaine. The bicarbonate group received 1 mmol/kg of sodium bicarbonate initially, and base deficit was corrected to -5 mmol/L with additional bicarbonate, whereas acidemia was untreated in the control group. Cardiopulmonary values were recorded at intervals between 5 mins and 24 hrs, and the neurologic deficit score was determined at 24 hrs after CPR.

MEASUREMENTS AND MAIN RESULTS

The treatment group received an additional 2 to 3 mmol/kg of bicarbonate in the early postresuscitation phase. Compared with controls, the bicarbonate group demonstrated equivalent (with brief arrest) or improved (with prolonged arrest) return of spontaneous circulation and survival to 24 hrs, with lessened neurologic deficit. The acidosis of arrest was decreased in the prolonged arrest group without hypercarbia. Improved coronary and systemic perfusion pressures were noted in the bicarbonate group with prolonged arrest, and the epinephrine requirement for return of spontaneous circulation was decreased.

CONCLUSIONS

The empirical administration of bicarbonate improves the survival rate and neurologic outcome in a canine model of cardiac arrest.

CPR challenges in pediatrics

The concept of the chain of survival for children has been extended to include prevention, bystander CPR, prehospital CPR, and acute care. Two clinical cases are presented as examples. The current status and possible weaknesses in each link of the chain are discussed, and suggestions are made for possible research initiatives.

Citizen response to cardiopulmonary emergencies

Since 1985, it has become apparent that the key to survival from adult sudden cardiac death is prompt defibrillation. Any delay from the time of collapse to the initial countershock will decrease the likelihood of survival. It also has been determined that CPR performed by lay rescuers is not begun promptly and, once started, often is performed for more than one minute before the emergency medical services (EMS) system is accessed, which significantly delays the time to defibrillation. In adults, therefore, the rescuer should phone first to activate the EMS system before performing CPR. In the pediatric population, respiratory arrests are far more common than cardiac arrests. Therefore, a rescuer should perform one minute of rescue support before activating the EMS system (a concept termed phone fast). It is recognized that this change is dependent upon a national EMS system that is still evolving. It is hoped that this change to phone first and phone fast will provide an impetus for rapid development of the EMS infrastructure.

Pediatric resuscitation pharmacology. Members of the Medications in Pediatric Resuscitation Panel

The goal of resuscitation pharmacology is to restart the heart as quickly as possible while preserving vital organ function during chest compression. Unfortunately, the application of advanced life support to pediatric cardiac arrest patients is often unsuccessful. The goal of this paper is to review the scientific rationale and educational considerations used to derive the guidelines for medication use in the pediatric patient during CPR. The first step in drug delivery during CPR is to achieve vascular access. The endotracheal route and intraosseous route may be used, although the former is not reliable. To maximize endotracheal drug effect, a larger dose should be instilled into the airway as deeply as possible. Any vascular access, including intraosseous, is preferable to endotracheal drug administration. Although other alpha-adrenergic agents are theoretically superior, epinephrine remains the drug of choice in pediatric resuscitation. The previously recommended dose, however, may be inadequate; a dose 10 to 20 times larger (100-200 micrograms/kg) should be considered, particularly if the standard dose is ineffective. Lacking convincing data, the indications and dose for calcium are unchanged. Similarly, there are no data advocating a change in the indications or dose for lidocaine, bretylium, or atropine. The treatment of arrest-induced acidosis remains controversial. The mainstay of therapy consists of efforts to maximize oxygenation and tissue perfusion. Bicarbonate is not a first-line drug; its use should be considered when the patient fails to respond to advanced life support efforts, including the administration of high-dose epinephrine. Bicarbonate may be helpful in the postresuscitation setting, but its use should not supplant efforts to maximize tissue perfusion. Adenosine is an effective and generally safe medication for the treatment of supraventricular tachycardia in infants and children. Therefore, its indications, dose, and toxicities should be included in the new guidelines. Finally, a summary of research initiatives are included, including a call for the development of a multi-institutional pediatric clinical resuscitation research group. Large numbers of patients must be enrolled in a standardized manner to better evaluate the benefits and adverse effects of various therapies. This includes the use of high-dose epinephrine, calcium, bicarbonate, and other buffer agents such as Carbicarb and THAM. Animal models simulating the etiology and pathophysiology of pediatric arrest also are needed. In both clinical and animal studies, neurologic outcome and long-term survival should be assessed rather than simply the rate of restoration of spontaneous circulation.

13CO2 washout kinetics in acute hypercapnia

The redistribution of CO2 and bicarbonate throughout the body following perturbations of normal respiration is not well described. We used tracer techniques to examine CO2-bicarbonate dynamics in an animal model in which acute hypercapnia was induced by hypoventilation. Eleven rabbits were anesthetized, tracheostomized, paralyzed and ventilated. In five animals PaCO2 was kept between 30 and 35 mmHg (control, C) while in six PaCO2 was held between 65 and 70 mmHg (acute hypercapnia, AH). A bolus of [13C]bicarbonate was given intravenously. Breath samples were obtained for 13CO2 by isotope ratio mass spectrometry and CO2 output (VCO2) was measured breath-by-breath for 240 min. There was no difference in the VCO2 between C [5.6 +/- 1.8 (SD) ml/min per kg] and AH (5.3 +/- 0.8). The 13CO2 washout for both C and AH was well fit by the sum of three exponentials. Only the time constant of the third (slowest) exponential was significantly longer in AH (103 +/- 11 min) compared with C (75 +/- 15, P less than 0.01). The mean residence time in AH (82 +/- 9 min) was significantly lower than in C (57 +/- 10, P less than 0.001). The estimated mass of exchangeable CO2 and bicarbonate was significantly greater in AH (443 +/- 37 ml per kg) compared with C (312 +/- 63, P less than 0.005). Compartmental analysis indicated that the increase in CO2-bicarbonate occurred primarily in the slowly exchanging pool. The data suggest that acute hypercapnia may be accompanied by a redistribution of exchangeable CO2 and bicarbonate in the body.

Controversies in cardiopulmonary resuscitation: pediatric considerations

This article addresses some therapeutic controversies concerning medications that may be needed during advanced pediatric life support (APLS) and the routes of administration that may be selected. The controversies that are discussed include the appropriateness and selection of various routes for drug administration during APLS; the determination of whether epinephrine hydrochloride is the adrenergic agent of choice for APLS and its appropriate dose; treatment of acidosis associated with a cardiopulmonary arrest; recommendations for atropine sulfate doses; and the role, if any, of calcium in APLS. Background information differentiating pediatric from adult cardiopulmonary arrest is presented to enable the reader to have a better understanding of the specific needs of children during this life-threatening emergency. The article also presents an overview of various drugs used for APLS and a table of their typically recommended doses and routes of administration.