Biterminal versus monoterminal electrosurgery
Biterminal versus monoterminal electrosurgery
The prefixes monoterminal and biterminal refer to the number of electrodes in contact with the patient’s body. Bipolar electrosurgery is always biterminal, whereas monopolar electrosurgery may be monoterminal or biterminal.
In monoterminal electrosurgery, there is no dispersive electrode connected to the patient’s body. Instead, the return electrode is connected to the earth, often through the power supply cable. These are known as earth-referenced units. These monoterminal units are ubiquitous in medical dermatology suites. However, it is important to note that if an electrically conductive object, such as a metal table or electrocardiogram electrode, makes contact with the patient’s body, some current may pass through this object on its return pathway to the ground. If the contact area is small, the current may be concentrated enough to cause a focal burn at the site. Therefore, these devices should only be used on conscious patients who are able to alert the surgeon to such complications, and on insulated tables with no exposed metal parts near the patient’s body.
The most common electrosurgical unit used in operating rooms today is a floating or isolated biterminal unit. Unlike earth-referenced units, the dispersive electrode is isolated from earth. Therefore, current will only flow if there is a dispersive electrode attached to the patient.23 As a result, if the patient comes in contact with a conductive environmental object, minimal to no current will pass through that object, and therefore the risk for burning is minimal. Additionally, the surgeon is protected, since one can touch the active electrode and as long as they do not touch the patient or the dispersive
electrode, there is no risk of the surgeon sustaining a burn.