Chapter 9: Defibrillation Flashcards
How quickly after onset of VF or pulseless VT does cerebral hypoxic injury begin?
Within 3 minutes
In absence of bystander CPR, how much does mortality rate increase for every minute between collapse and attempted defibrillation?
7-10%
Do short interruptions in chest compressions (to assess rhythm and give rescue breaths) impact success of defibrillation?
Yes!
Associated with myocardial dysfunction and reduced survival
Pre-shock pause should also be minimised
When bystander CPR is given, how much does mortality rate increase for every minute between collapse and attempted defibrillation?
3-4%
What features do defibrillators have in common?
Power source capable of providing DC
Capacitor that can be charged to pre-determined level
2 electrodes placed on patients chest
How is successful defibrillation defined?
Absence of VF/pVT 5s after shock delivery
Ultimate goal is ROSC
What factors impact defibrillation success?
Transthoracic impedance:
- good contact with pads
- clean and dry area
- shave off hair
Electrode position - best to be over area in fibrillation
What other electrode positions are acceptable for defibrillation?
Antero-posterior - left precordium and inf. to left scapula
Postero-lateral - mid axillary line and inf. to right scapula
Bi-axillary
Patients with implantable pacemakers/defib’s - must place 10-15cm away from these
What should you do first CPR or defibrillation?
If unwitnessed cardiac arrest, begin CPR immediately while defib is being set up
Once defibrillator on, dont delay, attempt ASAP
What should you do if a cardiac arrest is witnessed (and VF/pVT)?
Confirm rhythm
Give 3 successive shocks
Check for rhythm change and if appropriate pulse and signs of ROSC
What shock energy should be used?
First at minimum of 150J
Based on manufacturers guidance - if don’t know then maximum shock energy for all
What safety checks are key when defibrillating?
- Ensure no-one is touching the body
- Wipe water away from patient chest before
- Don’t hold IV infusion equipment or patients trolley during delivery
- Oxygen safety
How should oxygen be used safely during defibrillation?
- Take off any mask or nasal cannula and place >1m away
- Can leave ventilation bag connected to tracheal tube or supraglottic airway
- If pt on ventilator - leave ventilator tubing unless preventing CPR –> ventilation bag and switch off ventilator. Patients in critical care unit may be dependent of PEEP so try leave connected to ventilator
How is defibrillation modified in children?
> 8yo - same as adult
1-8 yo - special paediatric electrodes or can use adult but ensure don’t overlap
<1 can use AED if no other option
What is the shock synchronised with in synchronised cardioversion?
R wave - this avoid relative refractory period so minimises risk of inducing VF
VF/pVT don’t require this