Why Adult AEDs May Not Be Appropriate for Use in Children
Young children are much smaller than adults and therefore require a much lower energy setting for delivery of the same defibrillation dose (J/kg) used in an adult. AEDs designed for use in adults have energy levels (or a single energy level) capable of delivering a substantially higher dose (J/kg) to young children. Another concern is that infants and small children with sinus tachycardia or supraventricular tachycardia can have very high heart rates that might be misinterpreted as "shockable" rhythms by an AED with a diagnostic program developed for analyzing adult arrhythmias.
Current Recommendations in Pediatric Guidelines for Use of AEDs
The 2000 International Guidelines recommend use of AEDs for rhythm identification in children =8 years of age (Class IIb). Attempted defibrillation of VF/pulseless VT detected by an AED may be considered in these older children (Class Indeterminate). Attempted defibrillation of children less than approximately 8 years of age is not recommended, however.6
The average 8-year-old child weighs 25 kg. The current recommended initial dose of 150 to 200 J would provide 6 to 8 J/kg for the average 8-year-old. If the initial shock fails to eliminate VF, some AEDs are programmed to provide escalating doses to a maximum dosage of up to 360 J. Thus, second and subsequent doses deliver 150 to 360 J, resulting in a shock of 1 to 4 J/kg in an adult who weighs 80 to 125 kg and 6 to 15 J/kg in an 8-year-old child who weighs 25 kg.
Criteria for Changing the Recommendations for Use of AEDs in Children
First, it is necessary to determine whether the rhythm analysis system of a particular AED is safe and effective for children. This means that the rhythm analysis system must be evaluated to determine its capability to safely differentiate between shockable and nonshockable rhythms in children. Every effort must be made to confirm that the AED is safe when attached to and used in a child who does not have a shockable rhythm and who could be harmed by an inappropriate shock. Second, it is necessary to demonstrate that each AED delivers shocks that effectively defibrillate a child's heart and at the same time avoids any myocardial damage.
Clinical Data
One case report describes the successful use of a biphasic AED for adults in a 3-year-old child (level of evidence [LOE]=5).35 The child was successfully defibrillated with a single shock of 150 J (9 J/kg). Postresuscitation serum creatine kinase (216 IU/L) and troponin I (0.4 ng/mL) concentrations were normal. A postresuscitation echocardiogram showed no change in ventricular function compared with previous examinations.
Rhythm Analysis
A recently published report36 suggests that the rhythm analysis program of one AED system generally satisfies the sensitivity criterion of the AHA AED performance goals (ie, the device shocks a shockable rhythm) for VF, 1 of the 2 shockable rhythms. The same system also satisfies the AHA specificity criterion (ie, the device will not shock a nonshockable rhythm) for the nonshockable rhythms: sinus rhythm, supraventricular arrhythmias, ventricular ectopic beats, idioventricular rhythms, and asystole (this study contains LOE=3 and LOE=4).36,37The sensitivity for VF was 96%, which satisfies the AHA recommendation of >90%. The sensitivity for identification of rapid VT was 71%, which is below the AHA criterion of >75% sensitivity to shock rapid VT. The study reported 100% specificity for shockable rhythms (ie, the device never recommended a shock for a nonshockable rhythm). Most of the ECG rhythms (and all of the nonshockable rhythms) in that study were prospectively acquired (in hospital) using a modified AED. About 12%, however, were retrospectively collected (from in-hospital and out-of-hospital sources) and digitized from paper strips, then subjected to analysis by the AED's rhythm recognition algorithm. Those ECG test signals therefore lacked the fidelity of the ECGs acquired directly by an AED. Nevertheless, these initial findings are encouraging.
Another study prospectively examined the accuracy of a rhythm analysis program with an AED by another manufacturer. In this study the AED pads were used to directly record all of the ECG signals that were subsequently analyzed by an AED (LOE=3),38 which more realistically simulated the signal that would be analyzed by an AED in clinical use. Sensitivity for shockable VF was 94%. Sensitivity for shockable rapid VT was 60%, once again falling below the AHA criterion for rapid VT. Overall specificity was >99% (ie, the device correctly recommended no shock for 99% of the nonshockable rhythms analyzed) among a wide variety of sinus rhythms, sinus tachycardias, and supraventricular arrhythmias. In addition, this study investigated the effects of pad position on ECG rhythm analysis and found no significant differences in specificity between pads placed in the sternal-apical position and those placed in the anterior-posterior position.
On the basis of these 2 published studies, it seems that AED algorithms developed for detection of adult arrhythmias can provide highly specific and reasonably sensitive rhythm analysis in infants and children, especially given the relative rarity of rapid VT in this patient population.39 Because AED manufacturers use different arrhythmia detection algorithms, however, each manufacturer's algorithm should be tested against a pediatric arrhythmia database to demonstrate its efficacy in this population.
Delivered Energy
One recent development addresses concern about the level of energy delivered to a child by an AED designed for use in adults. Several AED manufacturers have designed new pediatric pad/cable systems for use with AEDs designed for use in adults to reduce the energy delivered to patients under 8 years of age.40 These modifications essentially raise impedance of the pad/cable system and also divert some of the delivered current away from the patient so that the adult energy dose delivered by the AED is reduced to about 50 to 75 J. The rationale was that with biphasic waveforms, the lower energy dose would be adequate for defibrillation yet reduce the possibility of myocardial damage to pediatric hearts. No changes were made in the AED rhythm analysis program, which continues to use algorithms for defibrillation in adults.
The FDA has ruled that AEDs, with these pediatric pad/cable systems, are composed of components that are "substantially equivalent" to components previously cleared by the FDA. Thus, several AED manufacturers have been cleared by the FDA to advertise, distribute, and sell to physicians (or physicians' agents) this new system, which accommodates both adult pad/cable pads for use in patients =8 years of age and pediatric pad/cable systems that reduce the delivered energies for use in patients <8 years of age.
The FDA clearance was based on the agency's conclusion that the new device is "substantially equivalent" to currently marketed devices. Because directly relevant clinical data are not yet available, the agency likely drew this conclusion by extrapolations from animal data and information similar to that included in this statement. FDA-cleared devices are subject to postmarket clinical surveillance for the purpose of accumulating further clinical data on device safety or efficacy. The ILCOR PALS Task Force is not responsible for determining whether a device should or should not be marketed, nor are its classes of recommendation meant to be a quantitative measure of clinical efficacy. Rather, these recommendations reflect the quality of published data in support of a therapy.
