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
  1. Yes!
  2. Associated with myocardial dysfunction
  3. Reduced survival
  4. 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
  1. Power source capable of providing DC
  2. Capacitor that can be charged to pre-determined level
  3. 2 electrodes placed on patients chest
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6
Q

How is successful defibrillation defined?

A
  1. Absence of VF/pVT 5s after shock delivery
  2. Ultimate goal is ROSC
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7
Q

What factors impact defibrillation success?

A
  1. Transthoracic impedance:
    - good contact with pads
    - clean and dry area
    - shave off hair
  2. Electrode position - best to be over area in fibrillation
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8
Q

What other electrode positions are acceptable for defibrillation?

A
  1. Antero-posterior - left precordium and inf. to left scapula
  2. Postero-lateral - mid axillary line and inf. to right scapula
  3. 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
  1. If unwitnessed -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
  1. Confirm rhythm
  2. Give 3 successive shocks
  3. Check for rhythm, 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

Generally 200J

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12
Q

What safety checks are key when defibrillating?

A
  1. Ensure no-one is touching the body
  2. Wipe water away from patient chest before
  3. Don’t hold IV infusion equipment or patients trolley during delivery
  4. Oxygen safety
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13
Q

How should oxygen be used safely during defibrillation?

A
  1. Take off any mask or nasal cannula and place >1m away
  2. Can leave ventilation bag connected to tracheal tube or supraglottic airway
  3. 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
  1. >8 yo - same as adult
  2. 1-8 yo - special paediatric electrodes or can use adult but ensure don’t overlap
  3. < 1 can use AED if no other option
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15
Q

What is the shock synchronised with in synchronised cardioversion?

A
  1. R wave
  2. This avoids relative refractory period
  3. 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
  1. Choose a different lead
  2. Adjust amplitude
17
Q

Can implantable ICD’s give a shock?

A
  1. Yes
  2. At 40 or 80J
  3. No warning
  4. 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
  1. Yes
  2. 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
  1. 50J
  2. Typically deliver between 10-20J