Defibrillation is a medical procedure using a controlled electrical current to stop or reset a life-threatening abnormal heart rhythm, often during a “Code Blue” for cardiac arrest patients in a hospital setting. The electrical shock depolarizes a large portion of the heart muscle simultaneously, allowing the heart’s natural pacemaker to re-establish a coordinated, effective rhythm. This therapy treats ventricular fibrillation (V-fib), where the heart quivers chaotically, and pulseless ventricular tachycardia (V-tach), a rapid rhythm that does not generate a pulse.
Preparing the Patient and Equipment
The first step in defibrillation is confirming that the patient’s heart rhythm is one that requires a shock, such as ventricular fibrillation or pulseless ventricular tachycardia. The medical team utilizes a manual defibrillator, which requires a trained provider to interpret the rhythm and select the energy level, unlike the automated external defibrillators (AEDs) found in public places. While high-quality chest compressions are administered, the team prepares the defibrillator device for use.
The device is first checked to ensure it is in manual mode and functioning correctly, with the appropriate adhesive pads or paddles connected. Adhesive pads are generally preferred because they allow for hands-free operation and are less likely to cause a break in chest compressions. Proper placement of these pads is critical to ensure the electrical current passes through the heart muscle, typically in an anterior-lateral position, with one pad placed below the right collarbone and the other on the left side of the chest.
The medical team selects the appropriate energy level, measured in Joules (J), based on established guidelines. For modern biphasic defibrillators, the initial shock energy is set between 120 and 200 Joules, while older monophasic devices require 360 Joules. Before applying the pads, the patient’s chest must be assessed for obstructions, such as medication patches, and ensured to be clean and dry, as moisture can divert the electrical current. Excessive chest hair may be quickly shaven to ensure excellent pad contact.
Delivering the Shock: Safety and Procedure
Once the correct rhythm is confirmed and the pads are in place, the device is charged to the pre-selected energy level. The professional performing the shock presses the charge button, a process that can take a few seconds. During this charging period, the team should continue chest compressions to maintain blood flow, minimizing the interruption of CPR.
The most important step before delivering the shock is strict adherence to the safety call-out protocol. The operator must verbally announce a warning, such as “I’m clear, you’re clear, oxygen is clear, everybody clear!”. This mandatory sequence ensures no personnel are touching the patient or connected equipment, preventing accidental electrical conduction. The oxygen source is also temporarily moved away or stopped if it is free-flowing to mitigate fire risk.
After the verbal and visual confirmation that the area is clear, the operator delivers the electrical shock by simultaneously pressing the discharge buttons. The time between stopping chest compressions and delivering the shock should be kept to a minimum, ideally less than five seconds, because even brief pauses reduce the chances of a successful outcome. The shock delivery is often visible as a momentary muscle contraction in the patient. After the energy is delivered, the operator immediately confirms the shock was successful and the defibrillator is disarmed if the rhythm is now non-shockable.
Assessing Results and Continuing Care
Immediately following the shock, the medical team does not pause to check for a pulse or a change in rhythm. Instead, the priority is the immediate resumption of high-quality chest compressions, starting with minimal delay. Even if the shock was successful in terminating the abnormal rhythm, the heart muscle is often stunned and may not generate a palpable pulse right away. Early resumption of CPR is crucial for maintaining blood pressure and coronary perfusion.
The team continues cardiopulmonary resuscitation for a full two-minute cycle before performing the next rhythm check. This period allows for the circulation of oxygen and any administered medications, maximizing the chance of a stable rhythm returning. If the rhythm check reveals that the life-threatening rhythm persists, the defibrillator is charged again, often to the same or a higher energy level, and the shock is repeated.
Throughout the process, the team leader ensures that all actions, including the energy level used, the number of shocks delivered, and the patient’s response, are meticulously recorded. If the heart successfully converts to an organized rhythm, the team then checks for a pulse. If a stable pulse is present, the team transitions to post-resuscitation care, which focuses on supporting the patient’s vital functions and addressing the underlying cause of the cardiac arrest.