Defibrillation and resuscitation in a piglet model of pediatric ventricular fibrillation following AHA 2005 guidelines

Abstract

To evaluate the efficacy and safety of defibrillation on children according to AHA 2005 recommendations Pig resembles human in the chest configuration, anatomy and physiology of the cardiovascular and pulmonary systems. Piglets weighing 7.0 Kg ± 1.4kg, 14.0kg ± 2.8kg, 25.0kg ± 5.0kg respectively, which represented children 1 to 8 yr old were induced ventricular fibrillation (VF). An adult biphasic AED was used in conjunction with pediatric attenuating electrodes which could deliver 50-J shock for 2 min and two min of cardiopulmonary resuscitation (CPR) immediately followed it. If VF did not reverse, 70-J shock combined with CPR was used, and the protocol was repeated five times. If an organized cardiac rhythm with mean aortic pressure more than 60 mmHg persisted for an interval of 5 minutes, the animal was regarded as successfully resuscitated. If the AED recognized a "non-shockable" rhythm, CPR was also performed immediately for 2 min. The same resuscitation program was exercised on piglets of manual defibrillator group. Neurologic alertness score, hemodynamic and myocardial functions were evaluated, autopsy was routinely performed to document possible injuries. In the AED group, 14 out of 15 animals, were successfully resuscitated, among them 11 piglets were resuscitated by 50-J defibrillation combined with cardiopulmonary resuscitation, and other three recovered to normal by 1 or 2 times of 70-J shocks and CPR. All animals in manual defibrillator group were successfully resuscitated by 50-J shocks and CPR. Left ventricular ejection fraction and fractional area change were reduced significantly during 3-4 hr post-resuscitation (P<0.05) and returned to baseline ranges at the end of 72 hr. There was no evidence of myocardial and pulmonary damage during autopsy, and neurologic recovery was also normal. Data of blood gas analysis, blood electrolytes and myocardial enzymes does not show any statistically significant difference (P> 0.05) in the groups. 50 J biphasic dose defibrillation combined with effective CPR, successfully terminated VF without adverse effects on myocardial function and survival in a piglet defibrillation model for young children 1 to 8 yr of age. The new guidelines recommendation that one shock immediately followed by CPR is reasonable. Adults AED combined with pediatric electrodes is feasible to the diagnosis and treatment of pediatric VF model. But the user should not rely too much on AED's "automatic" function, but should accumulate and integrate his experience with AED technology.