Defibrillation Flashcards
How long after cardiac arrest does cerebral hypoxic injury begin?
3 minutes
In the absence of chest compressions, how quickly does the probability of survival decline in VT/VF arrest?
10% every minute before defibrillation.
HOw does ventilation affect defibrillation?
Fully inflated lungs increase impedance.
Therefore shocks should ideally be delivered during full expiration.
PEEP should be minimised before defibrillation.
In acute asthma/COPD, gas trapping increases impedence, so higher energy levels may be needed.
Alternative pad placement options
Antero-posterior
Postero-lateral (right scapula and left mid-axilla)
Bi axillary
How does defibrillation procedure change if patient has witnessed arrest whilst already connected to a defibrillator to begin with (e.g. in cardiac catheter lab)?
If initial rhythm is VF/VT, give up to three successive shocks. Start compressions after the third shock.
What is the advantage of biphasic defibrillators?
Biphasic defibrillators release a current in one direction, and reverse the direction afer a few miliseconds during each shock.
They are effective at lower energy levels, require smaller capacitors, and are therefore smaller, lighter and more portable devices.
What energy level should be used during defibrillation?
Start at 150J.
Increase to gradually, with each shock, to 360J if necessary.
Unless using a monophasic defibrillator (old-school one), in which case, 360J is starting energy.
How long should a pause in compressions last when delivering a shock?
No more than 5 seconds to stop compressions, get everyone to stand clear, deliver the shock and restart compressions.
How far away should O2 devices be taken from patient before delivering a shock?
1 metre
During defibrillation, what O2 devices need to be moved away from the patient, and what don’t?
Face mask or nasal cannula need to be moved away.
Supraglottic airway or ETT do not.
What is the advantage of manual defibrillators?
Operator can diagnose the rhythm and deliver shock rapidly without waiting for rhythm analysis. This minimises interruption in chest compressions.
In shockable rhythms, when do you give adrenaline? When do you give amiodarone?
After third shock, during chest compressions.
How does pad placement differ if the patient has an implantable defibrillator/cardioverter/pacemaker?
Place pad at least 10cm away from edge of pacemaker.
Use one of the alternative pad placement options if necessary.
Should pacemakers be deactivated during CPR?
Not necessary.
