Cardiac Monitoring

Please refer to the separate cardiac section of this site for ECG basics and information on cardiac monitoring.

Defibrillation
The purpose of defibrillation of ventricular arrhythmias is to apply a controlled electrical shock to the heart, which leads to depolarisation of the entire electrical conduction system of the heart.

WARNING: Defibrillation can be DANGEROUS to you and to others!

When the heart repolarises, the normal electrical conduction may assert itself, in which case the ventricular arrhythmia is terminated. However, if enough energy is not used for defibrillation, the heart may not be completely depolarised, in which case the ventricular tachycardia or fibrillation may not be terminated. If there is no electrical activity in the heart (electrical asystole, or standstill), then the heart is already depolarised, and defibrillation will have no effect. 

For the patient to survive the emergency, the 'chain of survival' concept should be adopted, which requires the following actions:

At the time of a patient collapse, he/she could be in one of four cardiac rhythms. These are :

  1. Pulseless ventricular tachycardia - VT (Shockable)
  2. Ventricular Fibrillation - VF (Shockable)
  3. Asystole (Non-Shockable)
  4. Pulseless Electrical Activity - PEA (Non-Shockable) 

Ventricular tachycardia and ventricular fibrillation are common rhythms seen in sudden cardiac arrest and the only effective treatment is rapid defibrillation.

Management of VF and Pulseless VT

Patients Level of Consciousness - Is the Patient,

  1. Airway - Check that airway is clear. Perform finger sweep if anything is noticed or use suction
  2. CSpine - Does the mechanism indicate C Spine injury? Apply inline immobilisation and rigid collar if suspected injury.
  3. Breathing - Head tilt, chin lift or a jaw thrust if C Spine injury is present. Look, Listen and Feel for 10 seconds. If not breathing insert Oropharyngeal or Nasopharyngeal airway.
  4. Circulation - Feel for a carotid pulse for 10 seconds, if no pulse commence chest compressions at a rate of 100 per minute. Alternate between breaths and chest compressions. 2 breaths to 30 compressions.

While one crew member is doing the procedure above the second crew member will be preparing the defibrillator.

  1. Expose the patients chest
  2. Check for the 4 P's
    1. Perspiration (dry casualties chest)
    2. Patches (GTN patches)
    3. Pacemakers
    4. Pendants (All the above are only a concern if located where the defibrillator pads need to be positioned)
  3. Attach electrodes to the location indicated on the rear of the pads
  4. Connect to the defibrillator
  5. Switch on defibrillator
  6. Stop CPR to analyze the rhythm (All hands off patient)
  7. Confirm VF and VT
  8. Shout command ' STAND CLEAR CHARGING
  9. Charge the defibrillator to 200 joules *
  10. Before delivering shock shout ' STAND CLEAR SHOCKING' then look to make sure all hands are off.
  11. Deliver 200 joule shock *
  12. Charge Defibrillator straight away to 200 joules * ready for next shock.
  13. Follow steps 7 - 11 if still in shockable rhythm (if not a shockable rhythm dump the defibrillator charge)
  14. If a third shock is required this needs to be a 360 joule * shock
  15. Carry out 1 minute of CPR
  16. If patient is still in VF or VT continue shocks at 3 x 360 joules
  17. Carry on at 360 joule shocks unless a new rhythm appears and continue as appropriate e.g. Asystole = no shock but 2 minutes of CPR. Refer to ALS algorithm 

Note: * If using a Biphasic Defibrillator adjust joule setting as necessary 

Keep abreast of current resuscitation guidelines at all times
Paediatric Defibrillation Settings

Age

Weight (kg)

1st Defib

2nd Defib

3rd + Defib

1

10

20

20

40

2

12

24

24

48

3

14

28

28

56

4

16

32

32

64

5

18

36

36

72

6

20

40

40

80

7

22

44

44

88

8

24

48

48

96

9

26

52

52

104

10

28

56

56

112

11

30

60

60

120

12

32

64

64

128

Further Reading
Info on the following: Can be found on the European Resuscitation Council Guidelines 2010 Website

Please make sure your Ambulance service has adopted the new guidelines before using

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Defibrillators

  • Monophasic - current flows in one direction
  • Biphasic - direction of current flow is reversed at some point (usually near half way) during the discharge from the machine