9. Defibrillation

Question 1

T/F: bystander CPR doubles survival from witnessed cardiac arrest

Answer 1

true

Question 2

what is defibrillation?

Answer 2

the passage of an electrical current of sufficient magnitude across the myocardium to depolarise a critical mass of cardiac muscle simultaneously, enabling the natural pacemaker cells to resume control

Question 3

what is successful defibrillation defined as?

Answer 3

absence of VF/ pVT at 5s after shock delivery

Question 4

T/F: current flow is inversely proportional to transthoracic impedence

Answer 4

true - but biphasic defibrillators measures transthoracic impedance and adjust the energy delivered to compensate

Question 5

possible electrode positions?

Answer 5

ideally one just to the right of the upper sternum below the clavicle with the apical pad left mid-axillary in line with V6

can also go anteroposterior, posterolateral or bi-axillary

Question 6

T/F: you should avoid placing electrodes over a pt’s ICD

Answer 6

true - try placing at least 10cm away, can use alternative positions e.g. anterior-posterior

Question 7

T/F: a period of 2-3 mins CPR before defibrillation is recommended

Answer 7

false - defibrillate as soon as possible

Question 8

T/F: chest compressions should be continued during charging of the defibrillator

Answer 8

true - but everyone else other than the chest compressor stands back

Question 9

after a shock, immediately resume CPR

continue for how long before another rhythm analysis?

Answer 9

2 mins

Question 10

T/F: stop to check for pulse after defibrillation attempt

Answer 10

false - immediately resume CPR

people can remain pulseless for over 2 minutes before ROSC

Question 11

immediate management if pVT/ VF arrest occurs in a monitored environment

Answer 11

• confirm arrest
• call for help
• 3 successive shocks

commence CPR if not successful

Question 12

initial shock energy?

Answer 12

120-150J for first shock, same or higher for subsequent

Question 13

T/F: nasal cannulae, oxygen masks and ventilation bags attached to tracheal tubes should all be removed before defibrillation is attempted

Answer 13

false - remove any oxygen mask or nasal cannula

ventilation bags can be left connected to tracheal tubes/ SGAs

Question 14

sequence when using a manual defibrillator?

Answer 14

1) confirm arrest
2) call for help
3) start CPR while attaching pads
4) stop compressions to confirm rhythm (<5s)
5) resume compressions, advise everyone except chest compressor to stand clear. charge to 120-150J for first shock
6) when charged advise stop compressions and deliver shock
7) immediately resume CPR at ratio 30:2
8) continue for 2 mins then do another rhythm check
9) repeat until 3rd shock given, after which point give 1mg adrenaline and 300mg amiodarone IV. Give further adrenaline 1mg IV after alternate shocks

Question 15

when cardioverting a tachyarrhythmia, the shock must be synchronised with what part of the ECG?

Answer 15

the R wave
(note not required for VF/ pVT)

Question 16

where are ICDs usually implanted?

Answer 16

the pectoral region, most commonly on the left than the right

Question 17

what electrode position should be used for those with subcutaneous ICDs?

Answer 17

antero-posterior

Question 18

if an ICD goes off a large number of times causing distress and pain to the patient, how can it be disabled?

Answer 18

by placing a ring magnet over the ICD (does not disable its pacemaker ability)

Question 19

T/F: implantable loop recorders and neurostimulators are dangerous to do chest compressions over

Answer 19

false - they present no risk to those giving CPR but electrodes should be placed at least 10cm away to avoid damaging the devices