What is the procedure for mechanical defibrillation (cardioversion using a device that delivers an electric shock to the heart)?

From the Guidelines

Mechanical defibrillation should be performed promptly in patients with cardiac arrest caused by ventricular fibrillation or pulseless ventricular tachycardia, using a device that delivers an electric shock to the heart to restore a normal rhythm. To perform mechanical defibrillation:

• Confirm cardiac arrest and initiate CPR immediately.
• Apply defibrillator pads to the patient's bare chest (one on the upper right chest and one on the lower left side) [ 1 ].
• Turn on the defibrillator and follow its prompts.
• Ensure no one is touching the patient when analyzing the rhythm.
• If a shockable rhythm is detected, charge the defibrillator.
• Clear the area, ensuring no one is touching the patient.
• Deliver the shock by pressing the designated button.
• Immediately resume CPR for 2 minutes before reassessing the rhythm. For adults, use 120-200 joules for biphasic defibrillators or 360 joules for monophasic devices, as recommended by the 2010 American Heart Association guidelines [ 1 ]. However, a more recent study is not available, but the European Resuscitation Council guidelines from 1998 suggest that the initial sequence of shocks should have energies of 200 J, 200 J, and 360 J [ 1 ]. Defibrillation works by depolarizing all heart muscle cells simultaneously, allowing the heart's natural pacemaker to regain control and restore a normal rhythm [ 1 ]. Quick action is crucial, as the chance of successful defibrillation decreases by about 10% for every minute of delay. The placement of the defibrillator pads is crucial, with one paddle placed below the right clavicle in the mid-clavicular line and the other over the lower left ribs in the mid-anterior axillary line [ 1 ]. It is also important to ensure adequate contact with the chest wall and to use couplants to aid the passage of current at the interface between the paddles and the chest wall [ 1 ]. In female patients, the second pad or paddle should be placed firmly on the chest wall just outside the position of the normal cardiac apex, avoiding the breast tissue [ 1 ]. The polarity of the electrodes does not seem to affect the success of transthoracic defibrillation [ 1 ].

From the Research

Procedure for Mechanical Defibrillation

The procedure for mechanical defibrillation, also known as cardioversion using a device that delivers an electric shock to the heart, involves several steps:

• Defibrillation is effective and the most common treatment for ventricular fibrillation (VF) and pulseless ventricular tachycardia in patients with cardiac arrest 2.
• A single defibrillation of 200J is typically performed twice for patients with ventricular fibrillation in the initial rhythm of the emergency room 2.
• Intubation and intravenous access are achieved, and epinephrine and amiodarone are administered at the same time 2.
• For patients with refractory ventricular fibrillation (RVF), a double sequence defibrillation (DSD) of 400J may be performed after several trials of 150-200J defibrillation and adherence to advanced cardiac life support 2.

Timing of Defibrillation

The timing of defibrillation is crucial in cardiac arrest treatment:

• High-quality cardiopulmonary resuscitation (CPR) and prompt defibrillation when appropriate are currently the best early treatment for cardiac arrest 3.
• A period of CPR before defibrillation may partially revert the metabolic and hemodynamic deteriorations imposed on the heart by the no-flow state, thus increasing the chances of successful defibrillation 3.
• Recent studies have suggested that ECG waveform analysis of VF, such as the derived Amplitude Spectrum Area, can monitor the CPR effectiveness and predict the responsiveness to defibrillation 3.

Defibrillation in Specific Cases

Defibrillation procedures may vary in specific cases:

• In pediatric cardiac arrest, defibrillation is necessary in 18% of cases, and the first shock dose is typically 2 J/kg 4.
• The survival rate is higher in patients treated with a second shock dose of 2 J/kg than in those who receive higher doses 4.
• Patients with pulseless ventricular tachycardia (p-VT) as the initial documented rhythm have significantly better outcomes than those with ventricular fibrillation (VF) 5.