An Automated External Defibrillator (AED) is a medical device designed to analyze the heart’s rhythm and deliver an electrical shock to treat sudden cardiac arrest. A transdermal medication patch is an adhesive patch containing medication absorbed through the skin into the bloodstream. The presence of a transdermal patch near where AED electrode pads must be placed creates a significant safety concern during a life-saving emergency. This situation requires immediate intervention before the AED can be used safely and effectively.
Understanding the Risks Posed by Transdermal Patches
A primary risk of attempting to defibrillate over a transdermal patch is the potential for severe thermal burns to the patient’s skin. The patch creates a point of high electrical impedance between the skin and the AED pad, which concentrates the energy from the electrical shock. This concentration of current causes a rapid increase in heat at the skin’s surface, leading to full-thickness burns beneath the patch.
The electrical current delivered by the AED is intended to pass through the chest to the heart, but patch materials interfere with this pathway. Some patches contain a metal backing or aluminum foil layer, which are highly conductive. If the AED shock is delivered, this metallic component can arc the electrical current, causing a small explosion or a flash fire, a known risk particularly with nitroglycerin patches.
Another serious concern is the possibility of the electrical shock disrupting the patch’s controlled-release mechanism. Patches are engineered to deliver medication slowly and consistently. The high-energy electrical current can destabilize the patch’s structure, causing a rapid, uncontrolled release of the medication, often referred to as a “bolus.” This sudden surge can lead to an immediate and potentially fatal overdose.
The physical presence of the patch also interferes with the electrical contact necessary for successful defibrillation. Poor contact increases the transthoracic impedance, reducing the therapeutic current that reaches the heart muscle. This compromises the AED’s ability to stop the lethal arrhythmia.
Protocol for AED Use When a Patch is Present
When preparing a patient for defibrillation and a transdermal patch is discovered on the chest or near the intended pad placement site, the first step is the immediate removal of the patch. The rescuer should remove the patch quickly, ideally using a gloved hand to prevent accidental exposure to residual medication. The speed of this action is far more important than the method, as every second counts in a cardiac arrest scenario.
After the patch has been removed, the area of skin where it was located must be wiped clean to remove any traces of the medication or adhesive residue. This action serves two purposes: mitigating the risk of a rapid medication overdose and ensuring good electrical contact for the AED pad. A dry cloth, gauze, or even the rescuer’s shirt sleeve can be used to wipe the area quickly and thoroughly before the electrode is applied.
Rescuer safety must be maintained throughout this process. Gloves should be used if available when handling the patch, as the discarded patch contains a concentrated dose of medication that can be absorbed through the skin of the rescuer. The patch should be placed somewhere out of contact, such as under the patient’s shoulder or tucked safely away, to avoid accidental exposure.
If the patch cannot be removed quickly for any reason, or if the rescuer notices residue, the AED pads must be placed in a modified location. The standard procedure is to reposition the AED pads so that the edge of the pad is at least one inch (approximately 2.5 centimeters) away from the site of the patch or any residue. This small distance is often enough to prevent the current from concentrating on the patch site, reducing the risk of a burn and improving the chance of a successful shock.
Identifying Patches That Require Immediate Attention
A rescuer should be trained to recognize that any transdermal patch on the chest or upper torso is a concern and requires immediate attention before defibrillation. Patches that contain a metal backing or foil component, such as aluminum, represent the highest potential danger due to the risk of arcing and severe burns. These metallic layers are highly conductive pathways for the AED’s electrical current.
While all patches pose a theoretical risk of burn or medication bolus, those containing highly potent medications applied to the chest area are of the greatest concern in a cardiac emergency. Common examples of such patches include nitroglycerin, which is often used to treat chest pain, and fentanyl, a potent opioid used for pain management. The rapid, uncontrolled absorption of either of these drugs could cause life-threatening complications immediately following the electrical shock.
Other patches frequently applied to the upper body, such as scopolamine for motion sickness or nicotine patches for smoking cessation, also necessitate removal or pad repositioning. The key for the rescuer is not to spend time identifying the specific drug, but to recognize the object itself as a potential hazard. The presence of any small, adhesive square on the skin within the trajectory of the AED current should trigger the immediate removal and cleaning protocol to ensure patient safety and defibrillation efficacy.