Electrosurgery
Although electrical devices that create a heated probe may be used for the cauterization of tissue in some applications, electrosurgery refers to a different method than electrocautery.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 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.To minimize the effects of muscle and neural stimulation, electrosurgical equipment typically operates in the radio frequency (RF) range of 100 kHz to 5 MHz.The surgeon uses a pointed or blade shaped electrode called the "active electrode" to make contact with the tissue and exert a tissue effect - vaporization, and its linear propagation called electrosurgical cutting, or the combination of desiccation and protein coagulation used to seal blood vessels for the purpose of Hemostasis.This term began in 1940 as a Birtcher Corporation brand name Hyfrecator for "High Frequency Eradicator", but now serves generically to describe a general class of single-electrode, non-isolated (earth-referenced) low-powered electrosurgical machines intended mainly for office use.An accidental circuit completion path through an earth-ground creates the danger of a burn at a site far away from the probe electrode, and for this reason single-electrode devices are used only on conscious patients who would be aware of such complications, and only on carefully insulated tables.In such a setting, hyfrecators are not used to cut tissue, but to destroy relatively small lesions, and also to stop bleeding in surgical incisions made by blade instruments under local anesthesia.In cutting mode electrode touches the tissue, and sufficiently high power density is applied to vaporize its water content.[citation needed] Coagulation is performed using waveforms with lower average power, generating heat insufficient for explosive vaporization, but producing a thermal coagulum instead.Electrosurgical desiccation occurs when the electrode touches the tissue open to air, and the amount of generated heat is lower than that required for cutting.The vapour pocket typically reaches temperatures of approximately 400 degrees Celsius, which vaporizes and explodes a small section of soft tissue, resulting in an incision.[11] In applications of a continuous wave the heat diffusion typically leads to formation of a significant thermal damage zone at the edges of the lesion.[11][12] Using bursts of several tens of microseconds in duration the tissue can be cut, while the size of the heat diffusion zone does not exceed the cellular scale.Many modern electrosurgical generators provide sophisticated wave forms with power adjusted in real time, based on changes of the tissue impedance.It is also recommended to use a modern ElectroSurgical Unit that includes a return electrode monitoring system that continuously tests for reliable and safe patient contact.These systems interrogate the impedance of a split or dual-pad return electrode and will alarm out, disabling further generator output in case of fault.Common return electrode locations include lateral portions of the outer thighs, abdomen, back, or shoulder blades.This has been shown to contain various volatile organic compounds (VOCs), including formaldehyde,[14] which may cause harm by inhalation by the patients, surgeon or operating theatre staff.