The instrument is designed to provide the correct electrical waveforms to deliver to the site of surgery in order to coagulate blood vessels and to cut tissues smoothly. Surgeons may use the electrosurgery tool instead of, or in conjunction with, a conventional scalpel. When used properly, the electrosurgery unit damages tissue considerably less than the scalpel, with the added ability to stem bleeding safely.
Commercial electrosurgery machines may differ significantly, but comprise multiple components, which include:
- the electrode(s)
- the electrosurgical unit (ESU), which generates the radiofrequency current
- dispersive pads/electrodes for electrical current dispersion and foot pedals for operation in cut or coagulation mode
A complete circuit must be connected for current to flow, as in any circuit. In the case of electrosurgery, the circuit comprises the electrosurgical power unit, the active electrode (where cutting or coagulation transpire), the dispersive electrode (also known as the "return electrode," for return of current), and the path of least resistance through the patient's own body from the active electrode to the return electrode. When the circuit is complete and current can flow through it without too great of a resistance, the electricity that causes coagulation and cutting is readily applied to appropriate sites at the surgeon's discretion.
The low frequency power input of the wall (i.e. 60 Hz in the United States) is converted by the ESU to a high-frequency (on the order of 400,000 to 1,000,000 Hz) alternating current output that yields the therapeutic effects of electrosurgery. Safety is important with all electrical equipment; consequently the ESU should be grounded to a true earth ground that is electrically isolated from other grounds in the operating room, so that neither the surgeon nor the patient are shocked or electrocuted.
The high-frequency current is transmitted to the patient via the active electrode, which is insulated along its length until the electricity-emitting tip is reached, and which may take the form of:
- a one-piece electrode
- a pencil handpiece
- suction tips
The complete circuit discussed above may be achieved through either bipolar or monopolar modalities. Bipolar surgery is as the title implies, involving the use of two poles, or electrodes. The electrodes (active and return) are fixed upon a forceps-shaped tool. When pinched, the surgeon may apply current that traverses only the tissue in between the two electrodes, thereby coagulating it (unless the tissue is completely desiccated, in which case some current may leak into surrounding tissue). Carrying low-voltage current and affecting little tissue, the bipolar instrument is considerably safer than the monopolar device. Neurosurgeons usually opt for the bipolar tool over monopolar for this reason and for its inherent delicacy, among others.
The monopolar instrument is often used in place of the bipolar for three main reasons: it is easier to use, it
possesses the added capability of cutting tissue, and it is able to coagulate larger blood vessels. The active electrode, which may be in shape of a blade, loop, ball, needle, or pencil, can be disposable or reusable. Current emitted from this electrode is dispersed over a large area of padding by one of two types of dispersive electrode: conductive or capacitive. This can prove difficult, and is one reason why bipolar is the safer choice. Any erroneous selection or misuse of dispersive pads can result in a dangerous predicament for both the patient and the surgeon. While systems in use as of 2001 generally retain a number of alarms and warning systems built in, health care personnel must remain aware of the dangers implicit in using the equipment.
Three modes of operation are available, and can be produced on command, dependent upon the waveform issued by the ESU:
- Cutting: A high-frequency alternating current yields smooth, rapid cuts that evoke little to no hemostasis. The current stimulates cells to swell and explode.
- Fulguration: Sparking the tissue to lead to coagulation. There is no tissue-electrode contact; rather, voltage is raised in order to incite a spark between electrodes in order to coagulate the tissue in between.
- Desiccation: The drying out of cells leading to coagulation. Stems from direct contact with the active electrode and leaves a soft brown eschar, or scab.
It is key for all health care personnel involved in electrosurgery to be educated about the specific ESU and electrodes used by physicians at their location. The power settings on the ESU unit do not necessarily correspond to the quantity of power delivered. Thus, personnel must know not to equate numerical power settings with specific units unless explicitly labeled that way, i.e. one must not equate a power setting of "1" with 1 watt (or 100 watts) of power. Even if the amount of power is not known in watts, medical personnel must have an intuitive idea of what the different power settings mean in terms of the ability to cut, to coagulate, and for safety. Most machines make it easier with the ability to pre-program cutting and coagulation settings so that the surgeon and staff can move swiftly and accurately between settings during surgery.
Smoke can also be an issue with electrosurgery, so many units as of 2001 come equipped with smoke evacuation and filtration systems, which the staff must also learn how to operate through reading manufacturers' manuals.
Most maintenance on the electrosurgery power unit is generally performed by trained biomedical equipment technicians or biomedical engineers unless nursing staffers are adequately trained. The electrodes, however, must be cleansed and sterilized by the staff immediately following each surgery if they are not disposable.
Health care team roles
Most of the electrosurgical machine configuration and settings are handled by nursing staff and technicians. Often the operating room (O.R.) personnel know more about setting up the machine, its safety controls, and its handling than the surgeons using the equipment. This is because surgical residents are not formally trained in electrosurgical use; thus, since O.R. nursing personnel are usually trained by the manufacturer's sales representatives, the surgeons tend to rely on nursing staff to set up and manage the equipment. It is therefore very much an integral aspect of the staff's responsibility to alert surgeons to possible dangers, especially electrical, inherent in using the electrosurgical machine. The electrode insulation mentioned above is a key element in electrosurgical safety, so staff should remain alert for inadequate or defective insulation.
Health care personnel are generally trained by the sales representatives of the electrosurgery unit's manufacturer to set up and properly maintain the equipment. Without care and knowledge of the electrosurgery apparatus, great harm can be caused to patients undergoing surgery. Special attention should be paid to the manual since each ESU model is unique.
Hemostasis—Stoppage of bleeding.
Van Way, C. W., III. "Electrosurgery 101." Current Surgery 57, no. 2 (March-April, 2000): 172-177.
Van Way, C. W., III, and C. S. Hinrichs. "Electrosurgery 201: Basic electrical principles." Current Surgery 57, no. 3 (May-June, 2000): 261-264.
Electrosurgical Devices and Principles. <http://robo.fe.unilj.si/~matijap/bts/electrosurgery/section2.htm>.
Solid State Coagulation. <http://www.kirwans.com/solidstate.htm>.
Bryan Ronain Smith