Chapter 9: Defibrillation Flashcards

1
Q

How quickly after onset of VF or pulseless VT does cerebral hypoxic injury begin?

A

Within 3 minutes

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2
Q

In absence of bystander CPR, how much does mortality rate increase for every minute between collapse and attempted defibrillation?

A

7-10%

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3
Q

Do short interruptions in chest compressions (to assess rhythm and give rescue breaths) impact success of defibrillation?

A

Yes!

Associated with myocardial dysfunction and reduced survival

Pre-shock pause should also be minimised

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4
Q

When bystander CPR is given, how much does mortality rate increase for every minute between collapse and attempted defibrillation?

A

3-4%

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5
Q

What features do defibrillators have in common?

A

Power source capable of providing DC
Capacitor that can be charged to pre-determined level
2 electrodes placed on patients chest

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6
Q

How is successful defibrillation defined?

A

Absence of VF/pVT 5s after shock delivery

Ultimate goal is ROSC

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7
Q

What factors impact defibrillation success?

A

Transthoracic impedance:

  • good contact with pads
  • clean and dry area
  • shave off hair

Electrode position - best to be over area in fibrillation

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8
Q

What other electrode positions are acceptable for defibrillation?

A

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

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9
Q

What should you do first CPR or defibrillation?

A

If unwitnessed cardiac arrest, begin CPR immediately while defib is being set up

Once defibrillator on, dont delay, attempt ASAP

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10
Q

What should you do if a cardiac arrest is witnessed (and VF/pVT)?

A

Confirm rhythm

Give 3 successive shocks

Check for rhythm change and if appropriate pulse and signs of ROSC

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11
Q

What shock energy should be used?

A

First at minimum of 150J

Based on manufacturers guidance - if don’t know then maximum shock energy for all

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12
Q

What safety checks are key when defibrillating?

A
  • 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
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13
Q

How should oxygen be used safely during defibrillation?

A
  • 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
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14
Q

How is defibrillation modified in children?

A

> 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

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15
Q

What is the shock synchronised with in synchronised cardioversion?

A

R wave - this avoid relative refractory period so minimises risk of inducing VF

VF/pVT don’t require this

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16
Q

If synchronised cardioversion fails, what should you do?

A

Choose a different lead or adjust amplitude

17
Q

Can implantable ICD’s give a shock?

A

Yes at 40 or 80J

It gives these shocks without warning and number of shocks depends on the device

Can deactivate defibrillation capability by placing ring magnet over ICD - doesn’t disable pacemaker

18
Q

Should you defibrillate a patient if they have an ICD?

A

Yes if the ICD has not delivered a shock or if it has failed to terminate the arrhythmia

19
Q

What is the maximum energy needed for internal defibrillators?

A

50J

Typically deliver between 10-20J