Defibrillation is a medical procedure that delivers a controlled electrical shock to the heart, aiming to reset the organ’s chaotic electrical activity and restore a normal, coordinated rhythm. This intervention is reserved for life-threatening abnormal heart rhythms, such as ventricular fibrillation, which prevent the heart from pumping blood effectively. While the goal is the same for all patients, treating a child in cardiac arrest requires fundamentally different protocols than treating an adult. The pediatric body has distinct anatomical and physiological differences that necessitate specific modifications to equipment, energy dosage, and pad placement to ensure safety and effectiveness.
The Underlying Cause of Pediatric Cardiac Arrest
The reasons a child’s heart stops beating are often distinct from those in an adult, which dramatically influences the approach to resuscitation. Adult cardiac arrest is typically a primary cardiac event, often caused by sudden heart disease. In children, however, cardiac arrest is most frequently the final outcome of progressive respiratory failure or various forms of shock. This difference means the arrest is usually secondary to a lack of oxygen, known as an asphyxial arrest.
Conditions like severe infection, drowning, trauma, or airway obstruction can lead to profound hypoxia, causing the heart to slow down until it stops entirely. The most common initial rhythms seen in pediatric cardiac arrest are asystole (a flat line) or pulseless electrical activity (PEA), which are generally not responsive to defibrillation. Defibrillation is only indicated for the less common rhythms of ventricular fibrillation or pulseless ventricular tachycardia. Therefore, the priority in pediatric resuscitation is high-quality chest compressions and ventilation to address the underlying oxygen deficit.
Essential Equipment Modifications for Children
The equipment used for defibrillation must be adapted to a child’s smaller body size to deliver the electrical energy safely. The most visible modification involves the electrode pads, which come in specific pediatric sizes. These smaller pads prevent accidental contact between the electrodes when placed on a young child’s smaller chest, which would cause the electrical current to arc externally, preventing the shock from reaching the heart.
Beyond size, pediatric pads often function as dose attenuators, a safety feature that automatically reduces the amount of energy delivered by the defibrillator. When these specialized pads or a pediatric key are connected to an Automated External Defibrillator (AED), the device lowers the energy output to a level appropriate for a small patient. For example, adult AEDs delivering up to 360 Joules reduce the output to about 50 to 75 Joules when pediatric attenuating pads are used. This energy reduction is necessary because a full adult dose would deliver excessive energy relative to a child’s small body mass, risking myocardial damage.
Calculating the Correct Energy Dosage
The energy dose for defibrillating a child is calculated based on the patient’s weight, a fundamental difference from the fixed adult dose. Electrical energy is measured in Joules (J), and the dose is standardized as Joules per kilogram (J/kg) of body weight. This weight-based calculation ensures the energy delivered is sufficient to stop the chaotic rhythm without causing burns or damaging the heart muscle.
The generally recommended initial dose is 2 J/kg. If the first shock is unsuccessful, subsequent shocks must be escalated. The recommended energy for second and subsequent attempts is at least 4 J/kg.
For example, a 15-kilogram child would receive an initial shock of 30 Joules, increasing to 60 Joules for the second attempt. This precise titration is vital because too little energy may fail to stop the arrhythmia, while an excessive dose risks damaging the small heart. Since a child’s exact weight is often unknown in an emergency, responders rely on standardized methods, such as length-based resuscitation tapes, to quickly estimate the weight and determine the appropriate energy setting. Subsequent shocks may continue to escalate, but they should not exceed the maximum adult dose or 10 J/kg, whichever is lower.
Correct Defibrillator Pad Placement
The placement of electrode pads on a child must be deliberate to ensure the electrical current passes effectively through the heart muscle. In adults, the standard is anterolateral placement, with one pad on the upper right chest and the other on the lower left side. However, this placement may cause the pads to overlap in smaller children, resulting in a short circuit and ineffective energy delivery.
For infants and small children, or whenever the pads risk touching, the preferred method is anteroposterior placement (front-back). One pad is positioned on the front of the chest, usually over the sternum, while the second pad is placed directly on the back, between the shoulder blades. This front-to-back orientation ensures the heart is effectively sandwiched between the two electrodes, maximizing the chance that the electrical current travels directly through the cardiac tissue.