Defibrillation is a medical procedure that uses controlled electrical shocks to restore a normal heart rhythm. It is an important intervention for treating life-threatening arrhythmias, specifically ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT). These chaotic electrical activities prevent the heart from effectively pumping blood, leading to cardiac arrest. Defibrillation aims to depolarize the heart muscle simultaneously, allowing the heart’s natural pacemaker to re-establish a coordinated rhythm. This procedure is an important component of emergency medicine, offering a chance of survival in sudden cardiac arrest.
Patient-Specific Device and Body Surface Factors
Several patient-specific factors, including implanted devices and skin characteristics, require careful attention during defibrillation to ensure effectiveness and safety. Implanted medical devices, such as pacemakers and implantable cardioverter-defibrillators (ICDs), require special consideration. Placing defibrillation pads directly over these devices can potentially damage them or reduce the shock’s effectiveness. Pads should be positioned at least several inches away from the implanted device to mitigate these risks.
Transdermal medication patches, including those for nitroglycerin or nicotine, pose a hazard during defibrillation. These patches may contain metallic components that can lead to arcing, burns to the skin, or block the delivery of electrical current to the heart. Remove any such patches from the patient’s chest and wipe the skin clean before applying defibrillation pads.
Excessive body hair on the chest impedes proper adhesion of the defibrillation pads, leading to poor electrical contact and increased impedance. Poor contact reduces the amount of electrical current reaching the heart, making the shock less effective. Rapid shaving of the area or applying firm pressure to the pads helps ensure good skin contact.
Metal jewelry and body piercings in the vicinity of pad placement interfere with defibrillation. These metallic objects conduct electricity, potentially causing arcing or burns to the skin. If possible, remove any jewelry or piercings that might contact the pads or the electrical current path. If removal is not feasible, ensure pads are placed to avoid direct contact.
Physiological Conditions and Patient Demographics
Physiological conditions and patient demographics introduce specific considerations for effective defibrillation. In cases of severe hypothermia, below 30°C (86°F), the heart may become less responsive to electrical shocks. Current guidelines suggest delivering a limited number of shocks, typically one, followed by active rewarming efforts before attempting further defibrillation.
Defibrillating pediatric patients requires adjustments due to their smaller body size and unique physiology. Use appropriately sized defibrillation pads for children, which are often smaller and may require anterior-posterior placement (one on the chest, one on the back) to prevent them from touching. Energy levels are also adjusted based on the child’s weight, typically starting at 2 joules per kilogram and escalating to 4 joules per kilogram if initial shocks are unsuccessful.
When a pregnant patient requires defibrillation, the procedure is safe for both the mother and the fetus and should not be delayed. The goal is to ensure maternal survival, which improves fetal outcomes. Proper pad placement avoids the uterus, and positioning the mother on her left side helps optimize blood flow.
Obese patients present challenges for effective defibrillation due to increased chest wall thickness and difficulty achieving good pad contact. Alternative pad placements, such as the anteroposterior position (one pad on the chest, one on the back), may improve current delivery. Applying adequate pressure to the pads is important to ensure firm contact with the skin, minimizing impedance and maximizing the shock’s effectiveness.
Environmental and Equipment Safety
The environment and equipment handling are significant safety factors during defibrillation. Performing defibrillation on wet surfaces, such as a wet floor, carries a theoretical risk of electrical conduction to the operator or bystanders. While modern defibrillators are designed with safety features, it is recommended to move the patient to a dry surface and ensure their chest is dry for optimal pad adhesion and to minimize risks.
Flammable materials and oxygen pose a fire risk during defibrillation, especially if arcing occurs between pads and skin. Oxygen, while not flammable itself, significantly supports combustion. Remove oxygen delivery devices, such as masks or nasal cannulas, and move them at least one meter away from the patient’s chest during the shock.
Correct pad or paddle placement ensures the electrical current passes effectively through the heart. Common placements include anterolateral (one pad on the upper right chest, the other on the lower left side) or anteroposterior (one pad on the chest, one on the back). Good skin contact, free from air pockets, minimizes impedance and prevents burns.
Operator and bystander safety is important during defibrillation. Before delivering a shock, it is standard practice to announce “clear” to ensure no one is in contact with the patient, bed, or conductive surfaces. This verbal warning and visual check prevent accidental electrocution to rescuers and others.