Use adult AED pads on a child older than 8 years or weighing more than 55 pounds (25 kg). If adult pads are unavailable, pediatric pads may still be applied, but they deliver a reduced energy dose and are not the preferred choice for this age and weight group. When adult pads are the only option for a smaller child, place them so they do not touch each other.
How AED Pads Alter the Shock Dose
An automated external defibrillator does not decide the dose; the pads and the device's internal programming do. Adult pads have a larger conductive surface area, often roughly 10 to 13 centimeters across, and they signal the device to deliver a standard adult energy protocol. Pediatric pads are smaller and typically include a built-in attenuator that reduces delivered energy, commonly to about 50 to 86 joules depending on the manufacturer, versus 150 to 200 joules or more for adult protocols.
The pad size matters because current density depends on contact area. A larger pad spreads the same current over more tissue, which lowers impedance and improves the chance the shock reaches the heart muscle rather than burning or arcing at the skin surface. Pediatric pads reduce energy partly by design and partly through smaller contact geometry. That is appropriate for a small chest, but on a larger chest it can mean less current density where it is needed.
The device reads the pad type through a coded connector or resistor, then selects the energy waveform and joule setting. This is why mixing pad types, or forcing pediatric pads into an adult-mode device, can produce an unpredictable dose. The mechanism is simple: pad identity sets the protocol.
Plain language: the pads tell the machine how big the patient is, so the right pads give the right shock.
Why Age 8 and 55 Pounds Are Both Thresholds
Manufacturers and resuscitation councils set two overlapping cutoffs: age older than 8 years and weight greater than 55 pounds (25 kg). These thresholds exist because chest size, thoracic impedance, and heart mass scale roughly with age and weight, and pediatric attenuated doses were validated for smaller bodies. The two criteria are meant to be used together, not as alternatives to argue over.
In practice, if either criterion is met, adult pads are indicated. A large 7-year-old who weighs 70 pounds crosses the weight threshold. A small 9-year-old who weighs 45 pounds crosses the age threshold. Most children reach both thresholds around the same developmental stage, but growth variation means some cross one before the other.
The reconciliation rule is straightforward: use adult pads when age is greater than 8 years OR weight is greater than 25 kg. Use pediatric pads when the child is 1 to 8 years old AND weighs 25 kg or less. For infants under 1 year, use pediatric pads if available, or adult pads with careful placement if not, following device guidance and local protocol.
Quantified context: adult pad energy is typically 150 to 200 joules or higher; pediatric attenuated energy is commonly 50 to 86 joules. A 25 kg child sits near the upper edge of validated pediatric dosing, which is why the weight cutoff is set there rather than at a higher figure.
Edge Cases That Break the Simple Rule
Chest size can contradict age and weight. A child with obesity, chest wall deformity, or a large torso may need adult pads even if younger than 8 years, because pediatric pads may not cover enough surface to conduct effectively. Conversely, a thin 9-year-old may have a chest closer to pediatric geometry, but the age threshold still directs adult pads.
Pad placement is a separate edge case. Standard placement is anterior-lateral: one pad below the right clavicle and one on the left lateral chest below the armpit. If adult pads overlap or touch on a small chest, current can arc across the skin instead of crossing the heart. Separate them, or switch to pediatric pads only if the device and protocol allow.
Implanted devices are another edge. An implanted defibrillator or pacemaker can sit under a pad and absorb energy. Place pads at least 8 centimeters (about 3 inches) away from the device generator, and avoid placing a pad directly over it. Do not delay a shock to reposition for this unless the device is clearly in the way.
Wet chests, medication patches, and excessive chest hair reduce pad adhesion and increase impedance. Dry the chest, remove patches, and press pads firmly. Hypothermia and trauma are separate protocols that may override pad choice; follow the device voice prompts and local emergency medical services direction.
Misconceptions About Pediatric and Adult Pads
The most common misconception is that pediatric pads are "safer" for everyone. They are safer only when the dose matches the body; on a child over 8 years or over 55 pounds, they may underdose. The second is that adult pads are dangerous for any child. If pediatric pads are unavailable, adult pads are the recommended fallback for children 1 to 8 years, with careful placement to avoid pad contact.
Another misconception is that pads are interchangeable across brands. Connectors are often proprietary, and a pad may not fit a different manufacturer's device. Always check compatibility before use, and never modify a connector.
A counterintuitive detail: more joules is not automatically better. The goal is adequate current density across the heart, and pad geometry plus placement determine how efficiently energy is delivered. An adult dose with poor pad contact can be less effective than a well-placed lower dose. This is why technique matters as much as pad selection.
A professional caveat: follow the specific AED's voice and screen prompts. Device programming, not general rules, determines the actual delivered dose. If the device detects pediatric pads, it may cap energy regardless of patient size, so the pad choice and device mode must agree.
Comparison of Pad Options
| Pad type | Typical patient | Typical energy delivery | Contact area | When to choose |
|---|---|---|---|---|
| Adult pads | Older than 8 years or over 25 kg | Standard adult protocol, often 150 to 200 J or higher | Larger | Default for this age/weight group |
| Pediatric pads | 1 to 8 years and 25 kg or less | Attenuated, often 50 to 86 J | Smaller | Younger or lighter children only |
| Adult pads on small child | Under 8 years when pediatric unavailable | Adult protocol | Larger | Fallback with non-touching placement |
| Pediatric pads on larger child | Over 8 years or over 25 kg when adult unavailable | Attenuated | Smaller | Temporary fallback only |
| Anterior-lateral placement | Most patients | Depends on pad type | Varies | Standard position |
| Anterior-posterior placement | Selected cases per device guidance | Depends on pad type | Varies | When anterior-lateral is compromised |
The table makes the hierarchy visible: adult pads first for the stated group, pediatric pads second, and placement technique always relevant.
Time Course of AED Use
| Time point | Action | Why it matters |
|---|---|---|
| 0 seconds | Recognize arrest, call emergency services, start CPR | Early CPR buys time until defibrillation |
| Within 1 to 2 minutes | Retrieve AED and apply pads | Each minute of delay lowers survival |
| Pad application | Dry chest, remove patches, place pads correctly | Good contact improves current delivery |
| Analysis | Do not touch the patient during rhythm analysis | Movement corrupts the reading |
| Shock delivery | Clear everyone, deliver per prompt | Safety and dose accuracy |
| Immediately after shock | Resume CPR for 2 minutes | Circulation support between analyses |
| Repeat cycle | Reanalyze per device prompts | Persistent shockable rhythms need repeat shocks |
The time course is device-driven; the pad selection happens at the application step and then constrains every subsequent dose.
Practical Actions and Red-Flag Warnings
Step 1: Check age and weight. If older than 8 years or over 55 pounds (25 kg), select adult pads. Step 2: Confirm pad compatibility with the AED model. Step 3: Dry the chest, remove medication patches, and clip excessive hair if it prevents adhesion. Step 4: Place one pad below the right clavicle and one on the left lateral chest, ensuring they do not touch. Step 5: Follow the device prompts without touching the patient during analysis. Step 6: Resume CPR immediately after each shock until EMS arrives or the patient shows signs of life.
Red-flag warnings:
Never let adult pads overlap or touch on a small chest; arcing reduces effective dose. Do not place a pad directly over an implanted pacemaker or defibrillator generator. Do not use expired pads or pads with dried gel; adhesion and conduction fail. Do not delay a shock to search for pediatric pads when adult pads are available for a child over 8 years or 25 kg. Do not touch the patient during analysis or shock delivery. Do not substitute one brand's pads for another without confirming connector compatibility.
Limits of the Evidence and What This Article Cannot Do
Pad thresholds come from manufacturer labeling and resuscitation guidance, and individual device behavior varies. Energy values cited here are typical ranges, not universal specifications, and some devices use different waveforms or dose caps. Chest geometry, underlying heart condition, and cause of arrest can change effective dosing in ways no simple rule captures. This article cannot substitute for device labeling, local emergency medical services protocol, or training.
This article is general educational information, not a diagnosis, treatment plan, or medical advice. It does not promise any outcome from AED use. For device-specific instructions, follow the manufacturer's labeling and your local emergency medical services protocol, and consult a qualified clinician or certified instructor for training. In an emergency, call local emergency services immediately and follow dispatcher instructions.