For infants and children 8 years of age or younger or weighing 55 pounds (25 kg) or less, use pediatric AED pads when available—ideally ones with an energy attenuator that reduces delivered energy to roughly 50–90 joules—and if only adult pads are on hand, apply them rather than skip defibrillation, positioning them so the pads do not touch each other and, when feasible, front-and-back for an infant.
How Pediatric Pads Change the Shock
An automated external defibrillator delivers a fixed or impedance-adjusted dose of energy, typically 120–200 joules on adult settings. A child's smaller heart and lower transthoracic impedance mean the same energy density is higher, so pediatric pads or a pediatric key attenuates the shock to a lower level, commonly in the 50–90 joule range for attenuated devices. The attenuator is usually a resistor or switch inside the pad connector or a key inserted into the AED.
The pad itself also matters physically. Pediatric pads have a smaller active surface area and are often placed front-and-back to fit a small chest without the two electrodes bridging. Bridging creates a short circuit across the skin, which can reduce current through the heart and cause arcing or skin burns. If adult pads must be used on a small patient, they should be positioned to avoid contact between them, and front-and-back placement is acceptable on an infant.
The mechanism is not merely "less energy is safer." The goal is enough current density to depolarize a critical mass of myocardium while limiting peak current that can damage the small heart. This is why manufacturer labeling, not a single universal number, defines what a given device delivers. The plain point: pediatric settings are an engineered dose reduction, not a different therapy.
Quantified Context: Ages, Weights, and Doses
Guidance converges on roughly the same population: children under about 8 years or under about 25 kg (55 pounds). The 2015 AHA guidelines update for CPR and emergency cardiovascular care supports pediatric attenuated pads for infants and children under 8 years when available, and adult pads when pediatric ones are not available (American Heart Association, 2015). The weight threshold of 55 pounds (25 kg) is a practical proxy for when a child's chest and impedance approach adult values.
Defibrillation doses for children are weight-based in manual defibrillation, commonly starting around 2 J/kg for the first shock and 4 J/kg for subsequent shocks, up to about 10 J/kg or the adult maximum. An AED's attenuated setting is a fixed approximation of this, not a per-kilogram calculation. That gap is the central number to understand: a 10 kg infant at 2 J/kg needs only 20 J, while an attenuated AED may deliver 50 J or more.
| Device or pad type | Typical delivered energy | Best use | Key limitation |
|---|---|---|---|
| Adult pads, adult setting | ~120–200 J | Patients over ~8 years or ~25 kg | Excessive for small patients |
| Pediatric pads (attenuated) | ~50–90 J (device-dependent) | Infants and children ≤8 years or ≤25 kg | Availability, pad size |
| Pediatric key plus adult pads | Device-dependent reduced dose | Some AED models | Key must be present |
| Adult pads on child, no alternative | ~120–200 J | Only when pediatric unavailable | Higher energy; pad bridging risk |
| Manual defibrillator, weight-based | 2–10 J/kg | Trained clinicians | Requires training and equipment |
Edge Cases That Break the Rule of Thumb
The age and weight cutoffs are proxies and can conflict. A large 18-month-old over 25 kg is rare but possible; a small 9-year-old under 25 kg is common. When age and weight disagree with the device's labeled pediatric range, follow the manufacturer's labeling and local protocol, and default to the lower-energy option when the child is clearly small. Many protocols treat "under 8 years OR under 25 kg" as the trigger, so either criterion qualifies.
Newborns and infants under about 1 year present the tightest margin. Front-and-back pad placement is often recommended to fit the chest and avoid bridging. Some devices are not labeled for infants under 1 year; in that case adult pads placed carefully may be the only option, and the shock should not be withheld if the rhythm is shockable.
A counterintuitive professional caveat: a shock that is too low can also fail. If attenuated pads on a larger child fail to terminate a shockable rhythm, protocols may direct a switch to adult pads or settings on subsequent shocks. The safe choice is not always the lowest energy; it is the labeled energy matched to the patient.
Misconceptions Worth Retiring
The most common error is withholding a shock because only adult pads are available. Recommendations are consistent that defibrillation should not be delayed for lack of pediatric pads. Another is assuming pediatric pads are interchangeable across brands; connectors and attenuation are device-specific, and pads must match the AED model.
A third misconception is that adult pads "cannot" be used on a child. They can, with attention to placement and contact. A fourth is that the weight cutoff is exact; it is a practical threshold, and clinical judgment plus device labeling should guide borderline cases. Finally, pediatric pads do not make an AED fully "pediatric" in the manual-defibrillation sense; they approximate a lower dose.
Never delay a shock for a shockable rhythm while searching for pediatric pads. Never let the two pads touch or overlap on a small chest. Never assume a pediatric key or pad fits a different AED brand. Never use expired or damaged pads; check the expiration date and package seal. Never place pads over a medication patch or an implanted device without following protocol.
Practical Actions in Order
First, turn on the AED and follow its prompts; the device will state whether pediatric pads or a key are required. Second, attach pediatric pads if available and the patient meets the age or weight threshold. Third, if pediatric pads are unavailable, apply adult pads without delay and position them to avoid contact, using front-and-back placement for an infant when feasible. Fourth, clear everyone before each shock and resume CPR immediately after.
If the first attenuated shock fails to terminate a shockable rhythm, follow the device prompts and local protocol, which may direct adult pads or settings. Document which pads and energy were used, and hand off that information to EMS. These steps are thresholds and sequences, not dosing instructions; the AED's voice prompts and your training take precedence.
Timeline: What Happens and When
| Time point | Action | Why it matters |
|---|---|---|
| 0–30 seconds | Recognize arrest, start CPR, send for AED | Early CPR maintains perfusion |
| Within ~3 minutes | Apply pads, analyze rhythm | Shock success falls with delay |
| At rhythm analysis | Deliver shock if advised | Defibrillation is time-critical |
| Immediately after shock | Resume CPR for about 2 minutes | CPR supports the stunned heart |
| Every 2 minutes | Reanalyze, repeat shock if advised | Persistent shockable rhythm needs retreatment |
| During transport | Hand off pad type and energy used | Continuity of care |
Limitations and What the Evidence Cannot Settle
The evidence base for pediatric AED use is built on consensus guidelines and device labeling rather than large randomized trials, which are impractical in pediatric cardiac arrest. Exact energy thresholds for harm in children are not precisely established, and optimal pad placement for infants is supported by physiological reasoning and expert consensus more than by comparative trials. Device-specific attenuation means no single joule number applies to every AED. Availability of pediatric pads varies by location and model, so planning matters as much as the pads themselves.
This article is general educational information about AED pad selection, not a diagnosis, treatment plan, or dosing instruction. It does not promise any outcome, and device labeling and current emergency cardiovascular care guidelines take precedence. For a real emergency, call local emergency services immediately and follow dispatcher and AED prompts.