Procedure: Defibrillation by Medical Directive

Ensure that patient and health care provider safety standards are met during this procedure including:

  • Risk assessment and appropriate PPE
  • 4 Moments of Hand Hygiene
  • Procedural Safety Pause is performed
  • Two patient identification
  • Safe patient handling practices
  • Biomedical waste disposal policies


Defibrillation is the treatment for ventricular fibrillation. The success of resuscitation of patients with ventricular fibrillation relates to how quickly electrical energy can be applied to the myocardium. The longer the heart fibrillates, the greater the myocardial oxygen consumption and deterioration of myocardial function. The chance of successful defibrillation is reduced as the fibrillation time increases.

Equipment Required:

  • Crash cart with Zoll biphasic defibrillator
  • Multipurpose pacing/defibrillation pads
  • PPE- non-sterile gloves, gown and facemask with shield (assess risk for need of gown and facemask with shield)


Identify life-threatening rhythm

Initiate CPR

Activate Code Blue

Prepares for defibrillation

Prepare defibrillator

Maintain Environmental Safety Environment

Discharge Paddles

Continue CPR

Reassess rhythm

Administer epinephrine

Consider cause for non-responsiveness

Administer amiodarone

Repeat Cycle

Obstetrical ACLS


Order Requirements


New Zoll R Series Defibrillators: 
Link to Educational Material for New Zoll R Series Defibrillator-Pacemaker includes a series of brief video tutorials.





Identify Life-Threatening Rhythm

A certified critical care nurses may initiate defibrillation under the following circumstances: 

  • Ventricular Fibrillation (VF)
  • Pulseless Ventricular tachycardia (VT)

Note: Arterial line pressures < 60 mmHg may be associated with pulselessness. CPR should be initiated immediately.

Successful conversation of these rhythms occurs with rapid delivery of the first shock of energy.

Pulseless VT is often short-lived and deteriorates to VF.


Initiate CPR

The first responder initiates CPR until the defibrillator arrives. Use the following sequence:

  1. Initiate compressions while cart is en route
  2. Confirm that the patient has a shockable rhythm and defibrillate as soon as the cart arrives. If non-shockable rhythm, continue CPR per algorithm. 
  3. Resume CPR following defibrillation and complete the first 2 minute cycle of compressions. 
  4. Complete one full cycle of CPR even if the patient has a return of sinus rhythm (unless the patient is actively pushing you away).
  5. Place the back board after the first full cycle of CPR. Continue with ACLS per algorithm.  

Effective Compressions

Position hands on the sternum at the nipple line. Perform chest compressions at a rate of 100 - 120/minute to a depth of 5 to 6 cm (2 - 2.5 inches) of chest wall diameter.  The new Zoll R series has a compression pad that provides real time feedback on the quality of CPR.

During CPR, minimize interruptions of compressions and allow for good chest recoil. 

Whenever feasible, switch the person who is performing compressions after each 2 minute cycle (the effectiveness of CPR decreases beyond this).

CPR during Pregnancy:

Use the same hand positions for pregnant patients as non-pregnant (no longer recommended to move them to a more cephalic placement during pregnancy). 

A second person is required to maintain continuous manual left uterine displacement with patient in the supine position (see Obstetrical Emergencies). If standing on the right of the patient, one hand is used to push the uterus towards the left. If the assistant is standing to the left of the patient, two hands are used to pull the uterus towards the left.

End-Tidal CO2

Should be initiated at the onset of bagging and intubation. ETCO2 is now displayed on screen with the Zoll R series.

End-Tidal CO2 Benefits:

  • Confirm ETT placement
  • Guide compression quality (goal for ETCO2 >20 mmHg)
  • Improved technique (e.g. prompt to identify need to switch CPR provider if < 10 mmHg)
  • Consider ROSC for an abrupt sustained increase to normal levels (35-40 mmHg) or at least 10 mmHg increase above level at onset of CPR
  • Guide decision to terminate CPR. Levels < 10 mmHg after 20 minutes indicates low probability of ROSC. This assumes that the ETCO2 is not < 10 mmHg because of overbagging (induced hyperventilation)

Activate Code Blue

Call a code blue simultaneously with initiation of CPR. In CCTC, activated the bedside emergency call button and call for critical care physician STAT.


Prepare Patient for Defibrillation

Initial defibrillation:

Apply OneStep CPR 1 A/A Multifunctional pads. The pads should be connected to the Zoll and the package unopened. Before starting, confirm that the pads and machine have passed their self-test and are ready to open and use.

If CPR is in progress, apply the gel pads in the Anterior - Anterior position.

Anterior-Anterior Placement

Apply Pad #1 first to the left chest position. Position below the pectoral muscle as shown on pad diagram. For female patients, lift the breast and position on top of the pad once it has been applied.  

Pad #2 is attached to a CPR sensor. Position the CPR sensor so that the red vertical line is mid-sternum and the blue horizontal line is aligned with the nipple. Press the right pad into position as shown on the pad diagram.

Mutlifunctional Pads
Apex Pad
CPR Sensor and Right Chest Pad
OneStep Multifunctional CPR A/A Pads can be used for either Anterior-Anterior or Anterior-Posterior. Pads remain connected to Zoll cable and remain unopened until use. Apply apex pad first. For female patients, lift the breast and position the pad under the breast.

Position cross bars of CPR sensor to align with the mid sternum and nipple line. The right chest pad is attached to the CPR sensor for correct positioning.

If Anterior-Posterior placement is desired, separate the right chest pad from the sensor and apply to the patients left back.  Note: the posterior pad should be placed first.

Anterior-Posterior Placement

The OneStep CPR 1 A/A Multifunctional pads can be used for anterior - posterior placement. Separate the right chest pad from the CPR sensor. Apply the right chest pad to the left posterior chest first (to prevent wrinkling of the anterior pads.  Apply the apex pad as shown above. Apply the apex pad as shown above.

Check Box
Quality of CPR
End Tidal CO2
Identify the checkmark in the window display. This confirms that the pads and machine are functioning prior to use. The purple display identifies the quality and depth of CPR. End Tidal CO2 confirms adequacy of CPR and endotracheal tube placement.

ECG Electrodes

Apply the Zoll ECG electrodes. The One Step Multifunctional pads can monitor, shock and pace, but they cannot read the ECG at the same time that they pace or cardiovert. The ECG must be connected to the Zoll to provide sending and rhythm feedback.

Paddles are no longer available on the Crash Carts. 

Prepare Patient:

  • Side rails
  • Bed and patient flat
  • Chest exposed.  When time permits, hair should be clipped (not shaved).
  • Confirm gel pads in correct position and pressed onto skin.
  • Ensure paddles have no contact with metal jewelry, pharmacological patches (e.g., fentanyl, nitroglycerin) or transparent dressings.  

Position for Pacemaker/Defibrillator Pads:


OneStep CPR 1 A/A Multifunctional pads are attached and ready to open and apply on all Crash Carts.  When the unopened package is connected to the Zoll R, they perform ongoing self-tests to ensure functionality.  The package must remain unopened for the self-test to work.  Confirm that the pads and machine are functional prior to use by confirming the check mark is visible in the display window.

The CPR A/A pads can be applied either in the Anterior-Posterior position or Anterior-Anterior, however, during CPR they should be applied Anterior-Anterior for speed.

When pads are applied Anterior-Posterior, apply the posterior pad first to avoid wrinkling of the anterior pad.

Do no place pads over ECG electrodes. Arcing will occur if shock is delivered too close to electrodes.


Prepare Defibrillator:

  1. Continue CPR while preparing defibrillator.
  2. Turn Defibrillator on and ensure dial is set to "Defib".
  3. Confirm the default charge is 200 joules.
  4. Charge the pads. The paddles can be charged using the "Charge" button on the paddle or on the front of the monitor
  5. Press paddles firmly to the chest using 25 - 30 lbs of force.

Ensure the paddles do not come in contact with ECG leads.

The only treatment for fibrillation is delivering electrical current immediately to the myocardium. Biphasic defibrillators are more successful at converting VF with the first shock.


Maintain Environment Safety

Ensure that there is no contact with any metal objects and no one is in contact with the patient or bed. Call "All Clear".


Deliver Shock/Discharge paddles

Discharge energy by simultaneously depressing the SHOCK button on the paddles or monitor (second person).

Deliver shock following exhalation.

Air filled lungs decrease electrical conduction. Patient may be in a respiratory arrest.


Continue CPR

  • Do not check for pulse. Immediately return to CPR for 2 minutes.
  • Do not stop compressions for rescue breathing. Second provider delivers 1 rescue breath by face mask/ETT every 6 seconds.
  • Charge paddles to 200 Joules before 2 minutes of CPR is completed.  After the first shock is delivered, you can change to multipurpose pads for subsequent defibrillations.

CPR immediately after shock provides myocardial oxygenation which improves shock success.

Higher respiratory rates increase intrathoracic pressure which decreases perfusion of organs.


If paddles or multipurpose pads have been charged and are no longer required, do not discharge the energy into the machine or the air. To safely discharge the paddles/pads, turn the dial on the machine from "defib" to "monitor", then return paddles to device. 


Reassess Rhythm

  • Quickly reassess rhythm at the end of 2 minute CPR cycle to ensure that patient has not returned to VF or VT.
  • If patient is in VT/VF, proceed to deliver the next shock (as above) at 200 Joules
  • Resume CPR after completion of the shock
10. Administer Epinephrine

While CPR is being performed, administer epinephrine 1 mg IV direct per after the second defibrillation.

A certified critical care nurse may give epinephrine 1 mg IV direct after the second defibrillation shock has been delivered by Medical Directive. The certified critical care nurse may repeat epinephrine 1 mg IV direct every 3 minutes until Return of Spontaneous Circulation (ROSC). 

If the patient does not have IV access, epinephrine may also be given by a certified critical care nurse by Medical Directive down the endotracheal tube.

Epinephrine may be ordered earlier by a physician during the cardiac arrest. This will require an order as it is outside the Medical Directive. 

Epinephrine can increase cerebral and coronary perfusion pressures by alpha vasoconstriction. Delivery of drug during compressions minimizes interruptions to CPR.


Consider Causes for Non-responsiveness

Return to step # 8-9.
Troubleshoot for possible causes of non-responsive VT/VF (e.g. electrolyte disturbance, hypoxemia, MI).

Consider H's and T's

Hydrogen ions
Tension pneumothorax
Thrombosis: coronary/pulmonary
Consider adrenal endocrine (adrenal insufficiency, hypoglycemia)


Administer Antiarrhythmic

While CPR is being performed, administer amiodarone 300 mg IV direct per amiodarone procedure.

If contraindicated, administer lidocaine 1 mg/kg per defibrillation procedure under medical directive.

A certified critical care nurse may give lidocaine by Medical Directive if amiodarone is contraindicated at a total bolus dose of 1.5 mg/kg (preloaded syringe).

An order is required to initiate an amiodarone or lidocaine infusion.


Return to Steps 8-10

Maintain ABC’s.
Continue to treat possible causes of arrhythmia.

Return to Step #11 Administer Epinenphrine

Continue CPR as per step # 9 followed then by step # 10.


Obstetrical Considerations

The priority during resuscitation of the pregnant patient is the mother. Activate Code OB STAT and early (as soon as patient shows signs of deterioration in condition).  Code OB is available at Victoria Hospital only. At UH, page a general surgeon STAT for perimortem cesarean: 

Follow standard ACLS algorithms with the following modifications:

  • Hand position in the same location as for the non pregnant patient (it is no longer recommended to position the hands closer to the head)
  • Perform CPR in the supine position with one person assigned to manually display the uterus toward the patient's left.
    • Use two hand uterine "pull" technique if standing on patient's left side or one hand "push" if standing on patients right side.
  • All IVs above the diaphragm
  • Consider calcium chloride if patient was receiving magnesium sulphate
  • Remove fetal monitor (external and internal) prior to defibrillation
  • The goal is to start perimortem C-section at 4 minutes during cardiac arrest

Causes for Maternal Cardiac Arrest (Beauchops)

B     Bleeding/DIC
E     Embolism cardiac/pulmonary/ amniotic
A    Anaesthetic complications
   Uterine atony
C    Cardiac disease: MI/ischemia/aortic dissection/cardiomyopathy
   Review standard ACLS guidelines (Hs and Ts)
   Placental abruptio, previa
S    Sepsis



Document in cardiac arrest record.


Order Requirements

The medical directive for ACLS provides the authority to initiate interventions.

The RN who initiates the medical directive should be identified in the cardiac arrest record. 


American Heart Association. 2015 & 2018 Integrated ACLS Guidelines

American Heart Association. 2020 ACLS highlights. 

Last Update: November 5, 2018, February 10, 2020 (KK/BM); Reviewed January 22, 2021, Revised January 20, 2022