The grounding pad, also known as the patient return electrode, is a disposable safety device used during surgical procedures that require electrosurgery. This technology uses a high-frequency electrical current to perform tissue modifications. The pad’s primary function is to collect this electrical current after it has passed through the patient’s body and safely return it to the electrosurgical generator. The grounding pad prevents unintended thermal injury by safely completing the electrical circuit, which is necessary for this surgical technique.
The Role of Electrosurgery in the Operating Room
The grounding pad is necessary because of the widespread use of monopolar electrosurgery, a technique that allows surgeons to cut tissue and stop bleeding simultaneously. This technique involves generating a high-frequency alternating electrical current, typically in the radio-frequency range of 0.5 to 3 megahertz, which is delivered to the surgical site through a small active electrode. The high-frequency nature of the current avoids stimulating nerves and muscles. The electrical current encounters resistance in the tissue at the surgical tip, which generates heat.
The specific effect on the tissue depends on the power and waveform used by the electrosurgical unit. The cutting mode uses a continuous waveform to rapidly heat tissue, causing water inside the cells to vaporize. The coagulation mode, used to stop bleeding, employs a pulsed waveform that heats the tissue to a lower temperature, causing proteins to coagulate and sealing blood vessels. This process requires a continuous flow of electricity through the patient’s body.
How the Grounding Pad Completes the Circuit
In monopolar electrosurgery, the electrical current must travel through the patient’s body to complete a closed circuit back to the electrosurgical generator. The grounding pad serves as the return electrode, providing a controlled pathway for the current to exit the patient. The concept of current density is central to understanding the pad’s protective function, referring to the amount of electrical current concentrated in a given area.
At the small tip of the active electrode, the current is highly concentrated, leading to intense heating. The dispersive grounding pad is intentionally designed to have a very large surface area, spreading the electrical current over a wide expanse of the patient’s skin. This wide dispersal dramatically lowers the current density at the pad site. By keeping the current density low, the grounding pad prevents significant heat buildup that could cause a thermal burn.
Placement and Types of Grounding Pads
Proper placement of the grounding pad is important for patient safety. The pad must be applied to a clean, dry, and well-vascularized area of the skin, typically over a large muscle mass. Placing the pad over bony prominences, scar tissue, or metal implants is avoided because these areas may not conduct electricity well or could create alternative, unsafe current paths. The closer the pad is to the surgical site, the shorter the distance the current must travel through the body.
The pad itself consists of a conductive metallic film covered by an adhesive hydrogel that adheres firmly to the patient’s skin. Modern electrosurgical units utilize two main types of return electrodes: non-split and split pads. The traditional non-split design features a single continuous metal plate for current collection. The more advanced split pads, or dual pads, are segmented into two distinct halves, which enables continuous safety monitoring.
Preventing Patient Injury Through Monitoring
The greatest risk associated with electrosurgery is thermal injury at unintended exit points, which occurs if the grounding pad contact is poor or the pad detaches. If the pad lifts or is improperly placed, the electrical current will seek an alternative, smaller exit path, such as an EKG electrode. This unintended concentration of current creates a high current density at that small point, leading to a severe thermal burn.
To mitigate this failure mode, modern systems incorporate Return Electrode Monitoring (REM) technology. This technology exclusively uses the split pad design, allowing the electrosurgical unit to continuously measure the impedance, or resistance, across the two halves of the pad. A secure connection maintains a stable, low impedance. If the pad begins to detach or the contact quality degrades, the impedance rises significantly. The REM system detects this rise and automatically deactivates the electrosurgical generator, preventing thermal injury.