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Principles Of Early Defibrillation

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The earlier defibrillation occurs, the higher the survival rate. When a fatal arrhythmia is present, CPR can provide a small amount of blood flow to the heart and brain, but cannot directly restore an organized rhythm. The likelihood of restoring a perfusing rhythm is optimized with immediate CPR and defibrillation. The purpose of defibrillation is to disrupt a chaotic rhythm and allow the heart’s normal pacemakers to resume effective electrical activity.


Assure oxygen is NOT flowing across the patient’s chest when delivering shock

Do NOT stop chest compressions for more than 10 seconds when assessing the rhythm

Stay clear of patient when delivering shock

Assess pulse after the first 2 minutes of CPR

If the end tidal CO2 is < 10 mmHg during CPR, consider adding a vasopressor and improve chest compressions


The appropriate energy dose is determined by the design of the defibrillator – monophasic or biphasic. If you are using a monophasic defibrillator, give a single 360J shock. Use the same energy dose on subsequent shocks.

Biphasic defibrillators use a variety of waveforms, each of which is effective for terminating a fatal arrhythmia over a specific dose range. When using biphasic defibrillators, providers should use the manufacturer’s recommended energy dose. Many biphasic defibrillator manufacturers display the effective energy dose range on the face of the device.

To minimize interruptions in chest compressions during CPR, continue CPR while the defibrillator is charging. Immediately after the shock, resume CPR, beginning with chest compressions. Give CPR for 2 minutes (approximately 5 cycles). A cycle consists of 30 compressions followed by 2 ventilations for a patient without an advanced airway. Those patients with an advanced airway device in place can be ventilated at a rate of one breath every 5 to 6 seconds or 10 to 12 breaths per minute.

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