A defibrillator is a life-saving medical device designed to restore a normal heart rhythm by delivering a controlled electrical shock to a person experiencing sudden cardiac arrest. This process, known as defibrillation, interrupts a chaotic, ineffective heart rhythm, allowing the heart’s natural pacemaker to reset and resume coordinated beating. While this device is necessary for survival in these emergencies, the powerful electrical energy it uses carries specific, inherent risks that both users and patients should be aware of, ranging from direct physical injuries to operational hazards and issues with implanted medical technologies.
Direct Physical Injuries from the Electrical Charge
The transfer of high-energy electrical current through the body can cause physical injury, and the most common is the development of skin burns at the electrode sites. These burns occur because the skin presents high electrical resistance, generating heat (resistive heating) when current passes through. Burn severity is exacerbated if the pads are not applied firmly, if the skin is excessively hairy, or if conductive gel is insufficient, which concentrates current density.
The electrical shock is intended to depolarize the heart muscle, but it can also cause temporary damage to the myocardial tissue itself. Although modern biphasic defibrillators use lower energy levels, the shock can still injure heart muscle cells. The risk of this injury is generally considered minor compared to the alternative of death from cardiac arrest. Furthermore, the massive jolt causes an intense muscle contraction, which can lead to temporary muscle soreness or bruising in the chest area.
Operational Hazards and Bystander Safety
Defibrillation involves multiple steps where environmental conditions or human error can introduce significant risk for the rescuer and bystanders. The most dangerous operational hazard is the risk of electrical shock to anyone touching the patient or any conductive material connected to the patient during the discharge. This requires strict adherence to announcing “All clear!” before the shock button is pressed.
The “All clear!” protocol ensures no one is in physical contact with the patient, the bed, or any equipment that might be energized, preventing the current from traveling through a bystander. Using a defibrillator in a wet environment, such as rain or a puddle, also increases the risk of current conduction, potentially shocking the rescuer or others nearby.
Specific hazards arise from placing electrode pads over metal jewelry or transdermal medication patches. Medication patches must be removed and the skin wiped clean before pad placement to prevent the electrical current from igniting the substance or causing a severe localized burn. Placing a pad directly over a metal object, like an underwire bra or a body piercing, can cause the current to arc between the metal and the pad, leading to severe localized burns and redirecting energy away from the heart. The powerful muscle contraction caused by the shock can also lead to physical injury to the patient, such as a shoulder or back strain, especially if the patient is not lying on a firm surface.
Risks Related to Implanted Medical Devices
Patients with pre-existing implanted electronic devices, such as pacemakers or implantable cardioverter-defibrillators (ICDs), face risks when receiving an external defibrillator shock. The high-energy current can interfere with or potentially damage the internal circuitry of these devices, temporarily or permanently disrupting their function. The external shock can also cause the implanted device to deliver an inappropriate internal shock, which is painful and unnecessary.
To mitigate this danger, external defibrillator pads should never be placed directly over the site of an implanted device, which is usually visible as a small bump under the skin near the collarbone. The accepted protocol is to place the external pad at least one inch (about 2.5 centimeters) away from the device site to redirect the current pathway. While the external shock may temporarily affect the functionality of the implanted device, it is imperative to use the external defibrillator immediately if the patient is in cardiac arrest. The implanted device function should then be checked by a healthcare professional after the rescue attempt to ensure the settings are accurate and the device is operating correctly.
Dangers of Device Failure and Maintenance Neglect
For Automated External Defibrillators (AEDs) found in public spaces, the greatest danger lies in the device not being ready to function when a cardiac emergency occurs. Device failure creates a false sense of security and leads to a critical delay in life-saving care. A significant proportion of AED failures are linked to battery power issues, including expiration or depletion, which prevents the device from charging or delivering the necessary electrical current.
Similarly, electrode pads have an expiration date, often due to the drying out of the conductive gel. Deteriorated pads or faulty connectors are another major cause of device failure during a rescue attempt. This lack of readiness is frequently a result of maintenance neglect, as public access AEDs often lack regular checks. Ensuring the device’s status indicator shows a “ready” status, and regularly checking the expiration dates on the battery and pads, is a non-negotiable part of maintenance that ensures the device remains a reliable life-saving tool.