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
- 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 -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, 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
Generally 200J
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?
- >8 yo - 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 avoids relative refractory period
- Minimises risk of inducing VF
VF/pVT don’t require this