An Automated External Defibrillator (AED) is a portable medical device designed to deliver an electrical shock to the heart, aiming to restore a normal rhythm in individuals experiencing sudden cardiac arrest. While AEDs are designed for ease of use and are found in many public spaces, understanding when their application is inappropriate is as important as knowing how to operate them.
When Not to Deliver a Shock
An AED shock should not be delivered if the individual is conscious, responsive, or breathing normally. AEDs are specifically intended for people who are unconscious, unresponsive, and not breathing or only gasping. If a pulse is present, even if the person is unconscious, an AED is not indicated because it is designed to correct heart rhythms that are pulseless.
Using an AED in wet conditions or while the patient is submerged in water poses a risk of electrical current dispersion. It is important to move the individual to a dry area and thoroughly dry their chest before applying the AED pads.
If the person has an implanted medical device such as a pacemaker or an implantable cardioverter-defibrillator (ICD), AED pads should be placed at least one inch away from the device. Transdermal medication patches on the chest, such as those for nitroglycerin or nicotine, must be removed before applying AED pads. After removal, the skin should be wiped clean to ensure good electrical contact and prevent burns. For children, specific considerations apply regarding pad size; pediatric pads, which deliver attenuated energy, should be used for children under 8 years old or weighing less than 55 pounds if available. If only adult pads are accessible for a small child, they should be placed on the front and back of the chest to prevent them from touching, which can help distribute the energy more safely.
Understanding the Risks
While AEDs are programmed to analyze the heart’s rhythm and will not deliver a shock if one is not needed, attempting to use the device on a conscious individual or someone with a pulse wastes valuable time and delays appropriate medical assessment. The device’s internal safety features prevent accidental shocks to a normally functioning heart, but defibrillation is not the correct intervention in these cases.
Applying an AED in a wet environment can lead to the electrical current being dispersed through the water, reducing the effectiveness of the shock and potentially affecting bystanders. Water conducts electricity, diminishing focused energy delivery to the heart and creating a less safe environment. A clear path to the heart is essential for successful defibrillation.
Placing AED pads directly over an implanted pacemaker or ICD can interfere with the device’s function or reduce the effectiveness of the AED shock. The implanted device could block the electrical pathway, preventing the full therapeutic energy from reaching the heart. Similarly, medication patches can block the electrical current and also pose a risk of burns to the skin due to the rapid heating of the patch’s contents during the shock. Using adult pads on a small child can deliver an excessive amount of energy, potentially causing harm to the child’s smaller heart.
What to Do Instead
When an AED is not indicated, the immediate and most important action is to call for emergency medical services (such as 911 in many regions). Providing clear and concise information to the dispatcher can guide professional responders to the scene efficiently. This initiates the chain of survival.
If the individual is unresponsive and not breathing normally, even if an AED is contraindicated for reasons like a wet environment or the presence of a medication patch, cardiopulmonary resuscitation (CPR) should be initiated without delay. Chest compressions and rescue breaths help maintain blood flow to the brain and other vital organs until professional medical help arrives or an AED can be safely applied. CPR provides a temporary but crucial bridge, sustaining the person until more advanced care is possible.
While waiting for emergency services, continue to monitor the patient’s condition closely. If the contraindication is temporary, such as the presence of water or a medication patch, resolve the issue by moving the patient to a dry location and drying their chest, or by removing the patch and wiping the skin. After addressing these temporary obstacles, reassess the individual to determine if AED use becomes appropriate.