Electrosurgery is the application of a high-frequency (radio frequency) alternating polarity, electrical current to biological tissue as a means to cut, coagulate, desiccate, or fulgurate tissue. (These terms are used in specific ways for this methodology—see below). Its benefits include the ability to make precise cuts with limited blood loss. Electrosurgical devices are frequently used during surgical operations helping to prevent blood loss in hospital operating rooms or in outpatient procedures.In electrosurgical procedures, the tissue is heated by an electric current. Although electrical devices that create a heated probe may be used for the cauterization of tissue in some applications, electrosurgery is refers to a different method than electrocautery. Electrocautery uses heat conduction from a probe heated to a high temperature by a direct electrical current (much in the manner of a soldering iron). This may be accomplished by direct current from dry-cells in a penlight-type device.
Electrosurgery, by contrast, uses radio frequency (RF) alternating current to heat the tissue by RF induced intracellular oscillation of ionized molecules that result in an elevation of intracellular temperature. When the intracellular temperature reaches 60 degrees C, instantaneous cell death occurs. If tissue is heated to 60–99 degrees C, the simultaneous processes of tissue desiccation (dehydration) and protein coagulation occur. If the intracellular temperature rapidly reaches 100 degrees C, the intracellular contents undergo a liquid to gas conversion, massive volumetric expansion, and resulting explosive vaporization.
Appropriately applied with electrosurgical forceps, desiccation and coagulation result in the occlusion of blood vessels and halting of bleeding. While the process is technically a process of electrocoagulation, the term "electrocautery" is sometimes loosely, nontechnically and incorrectly used to describe it. The process of vaporization can be used to ablate tissue targets, or, by linear extension, used to transect or cut tissue. While the processes of vaporization/ cutting and desiccation/coagulation are best accomplished with relatively low voltage, continuous or near continuous waveforms, the process of fulguration is performed with relatively high voltage modulated waveforms. Fulguration is a superficial type of coagulation, typically created by arcing modulated high voltage current to tissue that is rapidly desiccated and coagulated. The continued application of current to this highly impedant tissue results in resistive heating and the achievement of very high temperatures—enough to cause breakdown of the organic molecules to sugars and even carbon, thus the dark textures from carbonization of tissue.
Diathermy is used by some as a synonym for electrosurgery but in other contexts diathermy means dielectric heating, produced by rotation of molecular dipoles in a high frequency electromagnetic field. This effect is most widely used in microwave ovens or some tissue ablative devices which operate at gigahertz frequencies. Lower frequencies, allowing for deeper penetration, are used in industrial processes.
RF electrosurgery is commonly used in virtually all surgical disciplines including dermatological, gynecological, cardiac, plastic, ocular, spine, ENT, maxillofacial, orthopedic, urological, neuro- and general surgical procedures as well as certain dental procedures.
RF electrosurgery is performed using a RF electrosurgical generator (also referred to as an electrosurgical unit or ESU) and a handpiece including one or two electrodes—a monopolar or bipolar instrument. All RF electrosurgery is bipolar so the difference between monopolar and bipolar instruments is that monopolar instruments comprise only one electrode while bipolar instruments include both electrodes in their design.
The monopolar instrument called an "active electrode" when energized, requires the application of another monopolar instrument called a "dispersive electrode" elsewhere on the patient's body that functions to 'defocus' or disperse the RF current thereby preventing thermal injury to the underlying tissue. This dispersive electrode is frequently and mistakenly called a "ground pad" or "neutral electrode". However virtually all currently available RF electrosurgical systems are designed to function with isolated circuits—the dispersive electrode is directly attached to the ESU, not to "ground". The same electrical current is transmitted across both the dispersive electrode and the active electrode, so it is not "neutral". The term "return electrode" is also technically incorrect since alternating electrical currents refer to alternating polarity, a circumstance that results in bidirectional flow across both electrodes in the circuit.
Bipolar instruments generally are designed with two "active" electrodes, such as a forceps for sealing blood vessels. However, the bipolar instrument can be designed such that one electrode is dispersive. The main advantage of bipolar instruments is that the only part of the patient included in the circuit is that which is between the two electrodes, a circumstance that eliminates the risk of current diversion and related adverse events. However, except for those devices designed to function in fluid, it is difficult to vaporize or cut tissue with bipolar instruments.