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Defibrillation Basics

The ACEM fellowship focuses on Australian and New Zealand Guidelines. Emphasis should be initially placed upon national ANZCOR guidelines and nationally sanctioned methods of performing defibrillation e.g. COACHED. There may be variations in practices between hospitals, states, prehospital services, remember your examiner may be from a different location. If you chose to deviate from national practice you MUST explain it. Evidence basis for these guidelines are in the below ANZCOR and ILCOR links.

Factors to consider:

Pads:

  • Pad placement: Pads are now standard use in most departments. Paddles are an alternative option. There is limited evidence regarding pad placement choices in VF/pulseless VT with most studies describing positioning for cardioversion and transthoracic impedance. ANZCOR recommend the anterior-lateral position. One pad is placed in the midaxillary line over the 6th left intercostal space, the other is placed in the right parasternal area over the 2nd intercostal space.
    Other options include anterior posterior and apex posterior (though this is less practical with ongoing compressions – this may be considered in the event of cardioversion or in the event of an anticipated deterioration).
    In hirsute males, consideration is given to shaving or using one set of pads to perform a hair removal. In those with large breast tissue, the pad should be placed lateral to, or underneath the left breast. Priority remains to minimise delays to shock delivery.
  • Pad size: Studies have shown that larger pad size decreases transthoracic impedance and increased shock success. ANZCOR suggest >8cm2 size pads.
  • PPM / AICD: ANZCOR recommend the that pad should be placed 8cm from the generator position.
  • Skin must be dry and clean.
  • Contact: Avoid contact with other equipment e.g. ECG leads / ECG electrodes / GTN patch.
  • Safety / Complications:
    • Care with water, metal fixtures, flammable substances and oxygen.
    • Oxygen and fire: No need for oxygen to be removed if on a closed circuit but care must be taken if there is free flowing high flow oxygen.
    • Currently the ARC does not recommend continuing compressions during defibrillation with ongoing chest compressions as safety is not established.
    • After identifying a non-shockable rhythm, the defibrillator should be rapidly disarmed.
    • Care must be taken to ensure all personnel are clear during defibrillation.
    • The pads must be well adhered to the chest wall to minimise spark risk.

Timing:

  • Early defibrillation is recognised as a priority in the chain of survival. The likelihood of success decreases with time until initiation.
  • Interruptions to effective good equality compressions should be minimised.
  • In cardiac arrest (after commencing BLS), the next priority is attachment of the defibrillator and preparation for defibrillation.
  • As soon as the pads are on the rhythm requires assessment.
  • For the purpose of ARC guidelines, it is worth stating “Please prepare for defibrillation” or “Prepare for a charge and check”.
  • The only exception to this for an expert would be a witnessed monitored arrest in a known non-shockable rhythm. In that circumstance, it is reasonable to state “This is a cardiac arrest in a non-shockable rhythm which we have witnessed occurring” and proceed down a PEA pathway.

Energy Choice:

Energy choice in adults depends on several factors. The first branch point is the guideline choice – ANZCOR or local. In addition, energy choice is dependent on what defibrillator is in use.

Biphasic defibrillators are now standard use. However, in the event of a monophasic defibrillator being in use the energy choice is set to a maximum of 360J (very rare now days in Australia).

ANZCOR guidelines recommend for biphasic defibrillators, the default energy setting is 200J. *other energy levels may be used in the event there is sufficient evidence for the defibrillator in question to have adequate shock success e.g. some defibrillators will deliver to a maximum of 150J.

COACHED (a safe method for defibrillation):

Requires trained staff and clear instructions. We suggest in a resuscitation sim OSCE state you want to use it. There will be variability between departments and states etc on exact wording. Ensure good effective closed loop communication.

C: Compressions Continue
O: Oxygen away (if free flowing BVM)
A: All others clear
C: Charging defibrillator (200J)
H: Hands off (compressor should say I’m safe)
E: Evaluating rhythm
D: Defibrillate or Disarm

Confirmation of shock delivery. Instruct your team to continue CPR if shock delivered. If the rhythm is non-shockable, disarm the defibrillator and if potentially perfusing you may do a brief pulse check.

Ensure safe defibrillator practice. There should be visual feedback of delivery of the shock – muscle response, ECG evidence. If the shock has not been delivered review the equipment with CPR restarted.

Expert additions for consideration / Points of debate: **Any deviations or expert actions should be justified and verbalised out loud in an exam scenario **

  • Increasing energy: Both ILCOR and the ARC document discuss the option of escalating the energy from 200J to the maximum that the defibrillator can achieve if the first shock is unsuccessful. Certain hospitals deliver higher energy shocks routinely as part of an internal hospital guideline. The CoSTR 2015 describes this as a weak recommendation with very low-quality evidence.
  • Staked shocks: This remains in the ARC document in a witnessed monitored cardiac arrest where the defibrillator is attached, with a rapid ability to review the rhythm, and can also deliver a rapid shock. Classic examples include ED / ICU / Cath lab. While chest compressions may be omitted if there is a reason not to do them immediately, e.g. post sternotomy. It is reasonable to consider doing them during charging. (Given that it takes several seconds). If doing this in an exam scenario one must justify what they are doing out loud. Generally speaking, the ARC advocates a single shock approach.
  • Local policy: See above, certain hospitals recommend in their local guidelines high energy shocks. If your hospital does this, be warned it is non-standard therefore your examiners may be surprised.
  • Oxygen / PEEP and respiratory cycle: As discussed above free flowing oxygen must be removed during defibrillation. However, if attached to an LMA / ETT this may be left attached. Ideally defibrillation should occur during expiration to limit transthoracic impedance. PEEP can increase transthoracic impedance.
  • Is there any role for synchronising in pulseless VT? Some cardiologists express a preference for this in arrest but this is highly specialised with limited papers and likely is more reflective of varying practice. Previously it was thought that the time delay in achieving synchronisation was a significant barrier to this. However, it is thought in fast pulseless VT with modern adhesive pads there is less delay to sync and shock delivery. Defibrillation outside the QRS complex is thought to potentially increase the risk of degeneration into VF hence the preference for a sync. This is difficult to study.
  • “Double down”: [Electrical Storm] Generally this approach is suggested only with refractory rhythms with multiple unsuccessful shocks and all appropriate medications have been given. Essentially a second defibrillator is used with pads next to each other * they must not be making contact. Both are charged and shocks are delivered simultaneously.
https://rebelem.com/beyond-acls-dual-simultaneous-external-defibrillation/
  • Hands on defibrillation: Addressed above, currently not recommended in the ANZCOR guidelines.
  • Coarse VF / Fine VF: Coarse VF is more likely to respond to defibrillation than fine VF. The gain can be increased to differentiate fine VF from asystole. Fine VF is thought to be part of the natural progression of prolonged VF related to depletion of myocardial energy stores. Good quality CPR may increase the amplitude of fine VF to render it coarse and increase shock success.
  • ETCO2: There is an increased emphasis on the use of ETCO2 in arrest to monitor 1) Quality of compressions 2) LMA / ETT placement and good quality ventilation 3) Early signs of ROSC.
  • Drugs: ARC guidelines will advise Amiodarone 300mg after the 3rd 150mg after the 5th shock. Other options include Lignocaine, Magnesium and for refractory rhythms there is a role for consideration of beta-blockers, avoiding adrenaline. See LITFL electrical storm post.
  • Choice of defibrillator: Caution not all defibrillators can pace. The energy max choice is manufacture specific. One can use the defibrillator pads to monitor except when pacing where leads must be used too.
  • Special circumstances:
    1. Refractory VT / VF
    2. Toxins
    3. Electrolytes
    4. Torsades de Pointes
    5. Hypothermia

Exam instructions:
Written: Questions regarding the ALS algorithm, factors influencing defibrillation.
OSCE: Describe the process of defibrillation / Teach a student, RMO, nurse how to defibrillate / Running an ALS scenario
Video:

emergencypedia COACHED
Links in LITFL
External

Tá gaeilge agam. Irish doc, ED FACEM in Oz. Into trauma, resus, cardio & tox! Chase gaelic footballs, dive, hike, run & rock in spare time! | @unanici |

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