Defibrillation

last authored: April 2010, David LaPierre
last reviewed:

 

Introduction

Earyl defibrillation is critical for maximizing chances of survival. With bystander CPR given, the chance of survival decreases by 3-4% per minute until defibrillation is given, or 7-10% per minute if CPR is not given.

 

Defibrillation does not restart the heart; rather, it temporarilty stops all electrical activity, allowing existing the heart's existing pacemaker to reset and begin a perfusing rhythm again.

This rhythm is typically quite slow initially, which is why CPR is required for several minutes following a shock.

 

 

 

Automatic External Defibrillation

Automatic External Defibrillators (AEDs) are small, affordable devices for use in cardiac arrest. They can be used with minimal training by the lay public.

 

There are many varities of AED which operate using similar principles.

Power on

Attach electrodes

• one on upper right chest, beside sternum and below clavicle
• one to left of nipple, just below left armpit

Analyze rhythm

• ensure no one is touching victim

Shock if advised

• ensure everyone is clear of vicitim

 

Do not stop CPR until pads are connected and in place. Do not stop CPR to troubleshoot AED.

Use AEDS only when patients have 3 clinical findings: no response, no breathing (excluding agonal gasps), no pulse.

Attach electrode pads to the patients bare chest, removing hair, water, sweat, and medication patches.

The

As soon as the shock is delivered, start CPR immediately with chest compressions for 2 minutes until the AED prompts a rhythm check.

After five cycles of CPR compressions and rescue breaths, use the AED to again analyze the victim's heart rhythm.

 

 

 

Special Considerations

 

Hairy chest: Attempt pad placement by pressing firmly. If connection is insufficient, a 'check pads or electrodes' message will occur. Quickly remove pads to remove hair; if this does not work, shave with a razor if available. Use a new set of pads to try again.	Victim is in water: remove from water   Victim is lying in a puddle: use AED   Chest is wet: dry chest
Pacemaker: Avoid placing AED directly over pacemaker; place at least one inch away   Transdermal medication patch: remove patch and wipe area clean. Act quickly to reduce delays in compressions	Children 8 years of age or younger should use a special patch.   Infants less than one year of age should not have AEDs placed.

 

 

 

Manual Defibrillators

Biphasic defibrillators use a variety of biphasic waveforms.

 

Paddles may be used, but require electrode paste to prevent burns. Pads may also be used, and these are preferred as they reduce the risk of arcing, can also be used for monitoring, and allow for rapid shock delivery.

 

 

 

 

Cardioversion

can be used to depolarize the bulk of myocardial tissue, interrupting rentry and allow the sinus node to regain pacemaker control.

 

 

Resources and References