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34 Automated External Defibrillation, Exercises of Nursing

Texas A&M University (A&M)Nursing

PURPOSE: An automated external defibrillator (AED) is a defibrillator that, by using a computerized detection system, analyzes cardiac rhythms, ...

Typology: Exercises

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286
Unit II Cardiovascular System
Section Five Cardiac Emergencies
PROCEDURE
34
Automated External
Defi brillation
Kiersten Henry
PURPOSE: An automated external defi brillator (AED) is a defi brillator that, by
using a computerized detection system, analyzes cardiac rhythms, distinguishes
between rhythms that require defi brillation and rhythms that do not, and delivers a
series of preprogrammed electrical shocks. The automated external defi brillator is
designed to allow early defi brillation by physicians, advanced practice nurses, and
other healthcare professionals who have minimal or no training in rhythm
recognition or manual defi brillation.
PREREQUISITE NURSING
KNOWLEDGE
• D e fi brillation is the therapeutic use of an electrical shock
that temporarily stops or stuns an irregularly beating heart
and allows the spontaneously repolarizing pacemaking
cells within the heart to recover and resume more normal
electrical activity. Ventricular fi brillation (VF) and ven-
tricular tachycardia (VT) are the only two rhythms recog-
nized as shockable by an automated external defi brillator
(AED; Fig. 34-1 ).
• Time is the major determining factor in the success rates
of defi brillation. In out-of-hospital cardiac arrests, for
every minute defi brillation is delayed the chance of
success decreases by 7% to 10%. When used in conjunc-
tion with effective CPR, the decrease in the likelihood of
success is more gradual and averages 3% to 4% per
minute. Effective CPR increases the amount of time in
which defi brillation may be effective.
1,10
• Although defi brillation is the defi nitive treatment for VF
and pulseless VT, the use of the AED is not a stand-alone
skill; it is used in conjunction with CPR. CPR should be
started as soon as the patient is found to be pulseless and
not stopped until the AED has been turned on, the pads
have been attached, and the machine is prompting the
provider to “stand clear” or “don ’ t touch the patient.”
1,2
Immediate postshock CPR starting with compressions has
been documented to lead to increased return of spontane-
ous circulation and increased cerebral survival,
1,9 which is
why time is not taken to check for a rhythm or pulse after
defi brillation.
• Ventricular fi brillation depletes the cardiac energy stores
of adenosine triphosphate (ATP) more rapidly than a
normal rhythm. The longer the heart goes without circula-
tion, the more depleted its energy stores. In a heart with
depleted energy stores, defi brillation is more likely to
result in asystole because no fuel remains to support spon-
taneous depolarization or myocardial contraction. Effec-
tive CPR can supply the needed oxygen and energy
substrates to the heart cells and allow them to return to a
perfusing rhythm.
1,6
• Three stages of VF are seen in cardiac arrest. The fi rst
phase is the electrical phase. During this phase, which is
considered the fi rst 4 to 5 minutes of VF, defi brillation is
most likely to be effective, and the sooner the shock can
be delivered the more likely it is to work. During the next
5 to 10 minutes after VF occurs, the hemodynamic or
circulatory phase, a brief period of CPR may “prime the
pump” and provide oxygen to the myocardial cells,
improving the effectiveness of the defi brillation. The met-
abolic phase starts 10 minutes after VF. During this phase,
the cardiac cells have experienced global ischemia and
energy depletion if no CPR has been initiated. CPR before
defi brillation is more likely to be successful and needs to
be used in conjunction with advanced cardiac life support
(ACLS) therapies.
1,6
• The AED is attached to the patient with adhesive electrode
pads. Through these pads, the rhythm is analyzed and a
shock delivered, if indicated. If the AED recognizes VF
or VT, visual and/or verbal prompts guide the operator to
deliver a shock to the patient. The AED, not the operator,
makes the decision about whether the rhythm is appropri-
ate for defi brillation.
• The chance of the AED shocking inappropriately is
minimal. There is a higher incidence of inappropriate
shocks with manual defi brillation than AED.
8 The AED
pf3
pf4
pf5

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286

Unit II Cardiovascular System

Section Five Cardiac Emergencies

PROCEDURE

Automated External

Defi brillation

Kiersten Henry

PURPOSE: An automated external defi brillator (AED) is a defi brillator that, by
using a computerized detection system, analyzes cardiac rhythms, distinguishes
between rhythms that require defibrillation and rhythms that do not, and delivers a
series of preprogrammed electrical shocks. The automated external defibrillator is
designed to allow early defi brillation by physicians, advanced practice nurses, and
other healthcare professionals who have minimal or no training in rhythm
recognition or manual defibrillation.

PREREQUISITE NURSING

KNOWLEDGE

  • Defi brillation is the therapeutic use of an electrical shock that temporarily stops or stuns an irregularly beating heart and allows the spontaneously repolarizing pacemaking cells within the heart to recover and resume more normal electrical activity. Ventricular fibrillation (VF) and ven- tricular tachycardia (VT) are the only two rhythms recog- nized as shockable by an automated external defibrillator (AED; Fig. 34-1).
  • Time is the major determining factor in the success rates of defibrillation. In out-of-hospital cardiac arrests, for every minute defi brillation is delayed the chance of success decreases by 7% to 10%. When used in conjunc- tion with effective CPR, the decrease in the likelihood of success is more gradual and averages 3% to 4% per minute. Effective CPR increases the amount of time in which defi brillation may be effective.1,
  • Although defibrillation is the definitive treatment for VF and pulseless VT, the use of the AED is not a stand-alone skill; it is used in conjunction with CPR. CPR should be started as soon as the patient is found to be pulseless and not stopped until the AED has been turned on, the pads have been attached, and the machine is prompting the provider to “stand clear” or “don ’t touch the patient.” 1, Immediate postshock CPR starting with compressions has been documented to lead to increased return of spontane- ous circulation and increased cerebral survival,1,9^ which is why time is not taken to check for a rhythm or pulse after defi brillation.
  • Ventricular fibrillation depletes the cardiac energy stores of adenosine triphosphate (ATP) more rapidly than a

normal rhythm. The longer the heart goes without circula- tion, the more depleted its energy stores. In a heart with depleted energy stores, defibrillation is more likely to result in asystole because no fuel remains to support spon- taneous depolarization or myocardial contraction. Effec- tive CPR can supply the needed oxygen and energy substrates to the heart cells and allow them to return to a perfusing rhythm.1,

  • Three stages of VF are seen in cardiac arrest. The fi rst phase is the electrical phase. During this phase, which is considered the first 4 to 5 minutes of VF, defibrillation is most likely to be effective, and the sooner the shock can be delivered the more likely it is to work. During the next 5 to 10 minutes after VF occurs, the hemodynamic or circulatory phase, a brief period of CPR may “prime the pump” and provide oxygen to the myocardial cells, improving the effectiveness of the defibrillation. The met- abolic phase starts 10 minutes after VF. During this phase, the cardiac cells have experienced global ischemia and energy depletion if no CPR has been initiated. CPR before defi brillation is more likely to be successful and needs to be used in conjunction with advanced cardiac life support (ACLS) therapies.1,
  • The AED is attached to the patient with adhesive electrode pads. Through these pads, the rhythm is analyzed and a shock delivered, if indicated. If the AED recognizes VF or VT, visual and/or verbal prompts guide the operator to deliver a shock to the patient. The AED, not the operator, makes the decision about whether the rhythm is appropri- ate for defibrillation.
  • The chance of the AED shocking inappropriately is minimal. There is a higher incidence of inappropriate shocks with manual defibrillation than AED.^8 The AED

34 Automated External Defibrillation 287

quality CPR and rapid initiation of ACLS should remain a focus for in-hospital cardiac arrest.

  • Many manual defibrillators have analysis capability that allows a tiered response (i.e., individuals with different skill levels can use the same defibrillator).
  • Most AEDs in use in emergency response systems (EMS) or in the hospital have a method of recording the event in the form of rhythm strip printouts, audio and event record- ing devices, data cards, or computer chips that can print an event summary.
  • AEDs may or may not have monitor screens. AEDs with screens may allow the provider with rhythm recognition skills to override the AED’s analysis and recommendations.
  • An important safety issue an AED operator must address is the possibility of inadvertently shocking a bystander or other provider at the scene. The operator must clear the patient verbally and visibly by looking at the patient from head to toe before and during the discharge of the energy to the patient.
  • All defi brillation programs need to include training for the potential operators. Training should include psychomotor skills, troubleshooting, equipment maintenance, and inter- facing with ACLS providers. Physicians, advanced prac- tice nurses, and other healthcare professionals have the responsibility to be familiar with the machine they will use.
  • When a resuscitation team (e.g., 911 responders, code team, ACLS providers) arrives, the team assumes respon- sibility for monitoring and treating the patient.

EQUIPMENT

  • AED
  • Nonsterile gloves
  • Barrier device or airway management equipment (bag- valve device with mask and oxygen)
  • Hand towel
  • At least two sets of adult defibrillation pads and poten- tially one set of child defibrillation pads

should be applied only to unresponsive, nonbreathing, pulseless patients. To keep artifact interference to a minimum, the patient should not be touched or moved during the analysis time.

  • The mnemonic “PAAD” makes it easy for the rescuer to remember the steps of operation of the AED: “P” for Power on, “A” for Attach the pads, “A” for clear to Analyze, and “D” for clear to Defibrillate.
  • Although AEDs are simple to use, healthcare personnel should be familiar with and technically competent in use of AEDs.
  • The AED is recommended for use in children ages 1 through 8 years if the child shows no signs of circulation. Approximately 15% of children in arrest have initial VT or VF. 5 Primary VF in children rapidly changes to asys- tole; rhythm detection and rapid defibrillation in children is most effective. It is best if the defibrillator has a pedi- atric switch or pediatric pads, which have an attenuator in the cord that decreases the amount of energy delivered. If pediatric pads are not available, adult pads should be used.3–5^ With use of adult pads, ensure that they do not touch each other because this may cause electrical arcing and skin burns and divert defibrillation energy. The pads should be at least 1 inch apart. If the pads cannot be fit on the child’s chest in a lead-II position, an anterior-posterior pad placement should be used. 3 Never use pediatric pads on an adult or large child because the reduced energy levels delivered by these electrodes may not be effective for treatment of VF.
  • The use of AEDs in prehospital settings has increased the success of defibrillation. The goal in the hospital should be to have the ability to defibrillate any person in cardiac arrest within 3 minutes or less of discovery. Placement of AED units in nonmonitored patient units and in public use areas of a hospital decreases the time to defibrillation. The largest study of in-hospital cardiac arrest found overall survival to discharge to be 15%. 2,10^ AEDs are also needed in freestanding or ambulatory care settings. The majority of in-hospital cardiac arrests do not involve VT/VF and therefore are not indications for defibrillation. 5,10^ High

Figure 34-1 Automated external defibrillator device. (Courtesy Philips Medical Systems.)

34 Automated External Defibrillation 289

Procedure continues on following page

Steps Rationale Special Considerations

A. Place one pad below the right clavicle to the right of the sternum and the other to the left of the left nipple or slightly lower than the nipple line with the center of the electrode pad on the midaxillary line. The electrode pads have pictures that indicate where to place them (see Fig. 34–1 ).

This placement ensures that the heart is between the two electrode pads, maximizing the current flow through the heart.

Placing an electrode pad on the sternum decreases effectiveness. Bone blocks some of the energy. Even with proper placement, only 4–25% of the delivered current actually passes through the heart, so proper pad placement is crucial.^1 Polarity of the electrode pads is interchangeable for defibrillation purposes. However, if ECG monitoring is being done, the QRS complex is inverted if the positive and negative pads are reversed. B. An alternative electrode pad position is anterior-posterior placement, where one pad is anterior over the left apex and the other is posterior behind the heart in the infrascapular location.

This placement also ensures that the heart is between the two electrode pads.

Ensure that the electrode pads are directly above and below each other.

  1. Connect the cables from the electrode pads to the AED.

Prepares equipment.

  1. Place the electrode pads firmly to eliminate air pockets and to form a complete seal.

The AED uses the electrode pads to monitor and to shock. Good contact must be ensured to defi brillate most effectively; air pockets under the electrode can cause electrical sparks and skin burns. A. Do not place the electrode pads over any medication or monitoring patches. Remove any medication pads from the chest and wipe the chest clean.

Defibrillating over medication patches can cause burns and block the transfer of energy from the electrode pad to the heart.

B. For the patient with an implantable cardioverter defi brillator (ICD) or pacemaker, keep the electrode pads 3 inches from the device generator. When possible for these patients, anterior- posterior placement is preferred. Other acceptable placement options are on the lateral chest wall on the right and left sides (biaxillary) or placement of the left pad in the standard apical position and the other pad on the right or left upper back.

Placement of electrode pads directly over an implanted device can divert energy away from the heart and can damage the device.

Some manufacturers recommend placing electrode pads 6 inches away from the device generators if possible. The ICD or pacemaker should be checked for possible damage to the device after defibrillation. Try to place the pads without interrupting CPR. Pad placement should not delay defibrillation.1,

Procedure for Automated External Defibrillation— Continued

290 Unit II Cardiovascular System

Steps Rationale Special Considerations

  1. Once the electrode pads are in place and plugged in, most AEDs sense an electrical pattern and tell the operator to make sure no one is touching the patient (“stand clear” or “don ’t touch the patient”).

The machine needs to analyze the rhythm to determine whether defibrillation is needed, and touching the patient or doing CPR may give the machine a false message or delay the ability of the AED to analyze the rhythm.

CPR must be stopped at this point. No one should be touching the patient when the AED is analyzing.

  1. Wait for the AED to analyze the patient ’s rhythm: A. If a shock is advised, clear the patient visually and verbally.

The AED has determined that the rhythm is either VF or VT; defibrillation is needed. Maintain safety for everyone around the patient. Anyone touching the patient or any conductive apparatus that is in contact with the patient (e.g., stretcher frame, intubation stylet) when the energy is discharged receives some of that shock.

Use a mnemonic such as “I ’ m clear, you ’ re clear, we ’ re all clear,” and look at the patient while talking to ensure that no one is touching the patient. Another mnemonic is “Shocking on three. One, I am clear. Two, you are clear. Three, we are all clear. Shocking now.”

B. If no shock is advised, restart CPR.

If the patient is not in a shockable rhythm and was pulseless, the only treatment is CPR until the ACLS team arrives.

  1. Push the shock button or buttons, as prompted while looking at the patient.

Delivering the shock quickly is the best way to convert the fatal rhythm. Most AEDs discharge the energy into the machine if the shock button is not pushed within a preset time frame, usually about 10–15 seconds.

The energy levels for AEDs are preset to an energy level recommended by the manufacturer. Some AEDs are fully automatic and deliver a shock if needed without user interaction. In this case the AED warns the user to stand clear before delivering the shock.

  1. Immediately restart CPR, beginning with compressions. Continue CPR for 2 minutes, approximately five cycles of 30 compressions to two breaths. If an advanced airway has been achieved, an asynchronous breath should be delivered 10 times/ min. 9 (Level D)*

Providing immediate postshock compressions increases the probability of return of spontaneous circulation.1,2,

Change compressors every 2 minutes to ensure effectiveness of CPR. Performing chest compressions is tiring, and effectiveness decreases after 2 minutes. 1

  1. After 2 minutes, the AED prompts the physicians, advanced practice nurses, and other healthcare professionals “stand clear” or “don ’t touch the patient” to allow it to analyze the rhythm, determining whether the rhythm remains shockable.

Checks to see whether the initial shock was effective or whether the patient needs to be defibrillated again.

Ensure that no one touches the patient during the analysis. A good time to change compressors is during the analysis pause.

  1. Repeat steps 8-11 if prompted to shock again.

If the patient remains in a shockable rhythm, CPR and defibrillation are most likely to be effective in return of spontaneous circulation.

Be sure to clear the patient for analysis and shocking.

Procedure for Automated External Defibrillation— Continued

*Level D: Peer-reviewed professional and organizational standards with the support of clinical study recommen dations.

292 Unit II Cardiovascular System

Documentation

Documentation should include the following:

  • Type of arrest (witnessed or not witnessed)
  • Time from patient collapse to first shock (only if witnessed)
  • CPR information (including start and stop times)
  • CPR performed before AED application: yes/no
  • Time of application of AED
  • Time of fi rst shock
  • Number of times patient was defibrillated
    • Preshock and postshock rhythms
    • Any complications
    • Assessment after resuscitation (if applicable)
    • Pain assessment, interventions, and effectiveness
    • Unexpected outcomes
    • Nursing interventions
    • Patient and family education

References and Additional Readings

For a complete list of references and additional readings for this procedure, scan this QR code with any freely available smartphone code reader app, or visit http://booksite.elsevier.com/.