Automated external defibrillators are life-saving pieces of equipment that allow almost anyone to quickly and easily save lives. They determine when defibrillation is appropriate to administer, and prompt users through every step of the process.

That said, even though an AED is excellent at determining when it should and should not administer a shock, there are some situations where an AED shouldn't be applied to begin with.

When To Avoid Using An AED

An AED shouldn't be used when it could do more harm than good. These situations, while rare, generally fall into two categories:

  • When it may not be able to obtain an accurate analysis of the patient.

  • When it may pose a hazard to people around the patient.

What Can Affect The Accuracy Of An AED?

An AED should not be applied in situations where its analysis may be affected. This can cause it to fail to administer a shock, or administer one in the wrong situation. Moving vehicles, for an example, can negatively impact an AED's accuracy and cause it to fail to recognize when a shock should or shouldn't be delivered. 

A lot of body hair can interfere with the adhesion of the pads themselves. This isn't a contraindication; some AED kits may come equipped with razors to remove some body hair to let the pads adhere effectively. However, any shaving must be performed extremely quickly-- a shock should be delivered as soon as possible after a patient begins going into cardiac arrest in order to give them the greatest chance at survival.

When Can An AED Be Dangerous?

An AED delivers a strong electrical shock. This means that it can be dangerous to patients or bystanders in any situation where a spark or live wire would be dangerous. Do not use an AED on a patient that is in water, even if it's only a puddle, get patients out of the rain, remove any wet clothing, and dry their chests before applying the adhesive pads. It's also important not to use an AED around combustible materials. Solvents, flowing oxygen, or fuels like gasoline can ignite or explode. 

That said, it's not dangerous to use an AED on patients that are lying on metal surfaces, provided bystanders stay clear of the patient's body, the pads don't touch metal, and all of the right safety precautions are taken. Similarly, it's safe to use on people with pacemakers or jewelry. Medication patches, like those used to treat chronic pain, won't cause problems for a defibrillator. However, they can still pose a hazard to other people who come in contact with the patient's skin and should be removed.

When someone goes into cardiac arrest, one of the most important factors that determines their survival is time. The sooner they get help, the less time there is for their heart, brain, and other organs to suffer damage from hypoxia. In all but a few situations, an AED can be safely used on someone suffering from cardiac arrest with minimal delay.