First Aid/Defibrilators


I was trying to find the right category to ask this question and first aid seemed to be the best fit. I have just been curious about something for a while. What would happen if a defibrillator was used on someone who didn't need one? I could think of a few scenarios, like for instance if a child somehow got hold of one and thought it was a toy and figured out how to use it. Could it kill them?

Hello Rob,

First, it world have to be a manual defibrillator like we have on the ambulance or in the hospital. An AED you would find at the mall, school, or work site has built-in safety features that would not allow someone with a rhythm wt be shocked. We shock patient's for a number of reasons, usually to stop a rhythm that cannot support life (usually V. Fib or V. Tach), with these rhythms the patient doesn't have a pulse and CPR should also be started. In the hospital and on the ambulance  we sometimes shock an otherwise normal rhythm which has become so fast the heart cannot pump blood well enough to keep the patient from passing out and ultimately, dying. This is usually done because of an "unstable, super ventricular tachycardia" and in this case we need to shock the patient while he still has a week pulse, and who may be awake. The important part about this kind of shock is that we (or the computer inside the defibrillator) must match up the cardiac rhythm with the shock placement in order to "reset" vs. stop the heart. There is a brief period of time (the relative refractory period) where an electrical shock placed within that period, will shut the heart's electrical system off. It's also possible with some defibrillators that the power setting is set too low to cause a catastrophic injury though with newer units it is more likely to automatically set it's self to an energy level that will work for the patient in distress.

See the attached web site about the relative refractory period (RRP):

I hope this answered your question.


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Marcus LaBarbera


I am available to answer most questions related to: first aid, pre- hospital medicine, EMT and Paramedic questions, medical transport, critical care transport, ICU/CCU care, sedation, and medicine in general.


I have worked as a NYS Paramedic since 1993 for both community based ambulance companies and large commercial agencies. I Have experience as bike team commander, and shift supervisor for a commercial ambulance. As a member of the Disaster team I was deployed to Louisiana for 20 days following hurricane Katrina. I worked along side the county Haz-Mat team as a "Tox-Medic" with advanced training in treating injuries from chemical agents. Besides my experience on the on the ambulance I have worked in a number of hospital based offices including dialysis and a sleep lab.

I started my EMS career as a NYS CFR (Certified First Responder)in 1989, an EMT in 1991, a Paramedic since 1993, and a CCU transport paramedic since 2005. I currently hold certification as a: NYS Paramedic, Critical Care Transport Paramedic, ACLS/CPR/PALS certified. Advanced Haz-Mat Life Support certified (AHLS). In the past I have taught CPR and ACLS to my coworkers and the local community.

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