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.Hainer BL, "Fundamentals of electrosurgery", ''Journal of the American Board of Family Practice'', 4(6):419–26, 1991 Nov.–Dec. Electrosurgery for the Skin
Barry L. Hainer M.D., Richard B. Usatine, M.D., ''American Family Physician'' (Journal of the American Academy of Family Physicians), 2002 Oct 1;66(7):1259–66."A Simple Guide to the Hyfrecator 2000"
. Schuco International (London) Ltd.Bouchier G, "The fundamentals of electro-surgery. High frequency current generators", ''Cah Prothese'', 1980 Jan;8(29):95–106. In French. (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 An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...

. Although electrical devices that create a heated probe may be used for the

cauterization Cauterization (or cauterisation, or cautery) is a medical practice or technique of burning a part of a body to remove or close off a part of it. It destroys some tissue in an attempt to mitigate bleeding and damage, remove an undesired growth, or ...

of tissue in some applications, electrosurgery refers to a different method than

electrocautery Cauterization (or cauterisation, or cautery) is a medical practice or technique of burning a part of a body to remove or close off a part of it. It destroys some tissue in an attempt to mitigate bleeding and damage, remove an undesired growth, or ...

. Electrocautery uses

heat conduction Conduction is the process by which heat is transferred from the hotter end to the colder end of an object. The ability of the object to conduct heat is known as its ''thermal conductivity'', and is denoted . Heat spontaneously flows along a te ...

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 high impedance 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 Diathermy is electrically induced heat or the use of high-frequency electromagnetic currents as a form of physical therapy and in surgical procedures. The earliest observations on the reactions of high-frequency electromagnetic currents upon the ...

is used by some as a synonym for electrosurgery but in other contexts

diathermy Diathermy is electrically induced heat or the use of high-frequency electromagnetic currents as a form of physical therapy and in surgical procedures. The earliest observations on the reactions of high-frequency electromagnetic currents upon the ...

means dielectric heating, produced by rotation of molecular dipoles in a high frequency electromagnetic field. This effect is most widely used in

microwave oven A microwave oven (commonly referred to as a microwave) is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range. This induces polar molecules in the food to rotate and produce ...

s 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.

Electrical stimulation of neural and muscle cells

Neural In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes ...

and

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...

cells are electrically-excitable, i.e. they can be stimulated by electric current. In human patients such stimulation may cause acute pain, muscle spasms, and even

cardiac arrest Cardiac arrest is when the heart suddenly and unexpectedly stops beating. It is a medical emergency that, without immediate medical intervention, will result in sudden cardiac death within minutes. Cardiopulmonary resuscitation (CPR) and possi ...

. Sensitivity of the nerve and muscle cells to electric field is due to the

voltage-gated ion channel Voltage-gated ion channels are a class of transmembrane proteins that form ion channels that are activated by changes in the electrical membrane potential near the channel. The membrane potential alters the conformation of the channel proteins, ...

s present in their

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (t ...

s. Stimulation threshold does not vary much at low frequencies (so called

rheobase Rheobase is a measure of membrane potential excitability. In neuroscience, rheobase is the minimal current amplitude of infinite duration (in a practical sense, about 300 milliseconds) that results in the depolarization threshold of the cell m ...

-constant level). However, the threshold starts increasing with decreasing duration of a pulse (or a cycle) when it drops below a characteristic minimum (so called

chronaxie Chronaxie is the minimum time required for an electric current double the strength of the rheobase to stimulate a muscle or a neuron. Rheobase is the lowest intensity with indefinite pulse duration which just stimulated muscles or nerves. Chrona ...

). Typically,

of neural cells is in the range of 0.1–10 ms, so the sensitivity to electrical stimulation (inverse of the stimulation threshold) decreases with increasing frequency in the kHz range and above. (Note that frequency of the alternating electric current is an inverse of the duration of a single cycle). To minimize the effects of muscle and neural stimulation, electrosurgical equipment typically operates in the

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the up ...

(RF) range of 100 kHz to 5 MHz. Operation at higher frequencies also helps minimizing the amount of hydrogen and oxygen generated by

electrolysis of water Electrolysis of water, also known as electrochemical water splitting, is the process of using electricity to decompose water into oxygen and hydrogen gas by electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, or remi ...

. This is especially important consideration for applications in liquid medium in closed compartments, where generation of gas bubbles may interfere with the procedure. For example, bubbles produced during an operation inside an eye may obscure a field of view.

Common electrode configurations for devices with isolated circuits

There are several commonly used ''electrode configurations'' or circuit topologies: With "bipolar" instruments the current is applied to the patient using a pair of similarly-sized electrodes. For example, special

forceps Forceps (plural forceps or considered a plural noun without a singular, often a pair of forceps; the Latin plural ''forcipes'' is no longer recorded in most dictionaries) are a handheld, hinged instrument used for grasping and holding objects. Fo ...

, with one tine connected to one pole of the RF generator and the other tine connected to the other pole of the generator. When a piece of tissue is held by the forceps, the RF alternating polarity electrical current oscillates between the two forceps tines, heating the intervening tissue by the previously described synchronous oscillation of intracellular ions. In ''monopolar'' configuration the patient is attached to the dispersive electrode, a relatively large metal plate or a flexible metalized plastic pad which is connected to the RF generator or electrosurgical unit (ESU). 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. The electric current oscillates between the active electrode and the dispersive electrode with the entire patient interposed between the two. Since the concentration of the RF current reduces with distance from the active electrode the

current density In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional a ...

rapidly (quadratically) decreases. Since the rate of tissue heating is proportional to the square of current density, the heating occurs in a very localized region, only near the portion of the electrode, usually the tip, near to or in contact with the target tissue. On an extremity such as a finger, there is limited cross-sectional area to disperse the current, a circumstance which might result in higher current density and some heating throughout the volume of the extremity. Another bipolar instrument is characterized with both electrodes on the same design, but the dispersive electrode is much larger than the active one. Since current density is higher in front of the smaller electrode, the heating and associated tissue effects take place only (or primarily) in front of the active electrode, and exact position of the dispersive electrode on tissue is not critical. Sometimes such configuration is called ''sesquipolar'', even though the origin of this term in Latin (''sesqui'') means a ratio of 1.5.

Dedicated non-grounded machines without a dispersive electrode

Relatively low-powered high frequency electrosurgery can be performed on conscious outpatients with no grounded machines without a dispersive electrode . Operating at low currents with no dispersive electrode is possible because, at the medium RF frequencies (usually 100 – 500 kHz) that the machines generate, the self-

capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...

of the patient's body (which is between the patient's body and the machine's ground) is large enough to allow the resulting

displacement current In electromagnetism, displacement current density is the quantity appearing in Maxwell's equations that is defined in terms of the rate of change of , the electric displacement field. Displacement current density has the same units as electric ...

to act as a virtual "circuit completion path." One example of such a machine is called a

hyfrecator A hyfrecator is a low-powered medical apparatus used in electrosurgery on conscious patients, usually in an office setting. It is used to destroy tissue directly, and to stop bleeding during minor surgery. It works by emitting low-power high-frequ ...

. 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.

Electrosurgical modalities

In cutting mode electrode touches the tissue, and sufficiently high power density is applied to vaporize its water content. Since water vapor is not conductive under normal circumstances, electric current cannot flow through the vapor layer. Energy delivery beyond the vaporization threshold can continue if sufficiently high voltage is applied (> +/-200 V) to ionize vapor and convert it into a conductive plasma. Vapor and fragments of the overheated tissue are ejected, forming a crater. Electrode surfaces intended to be used for cutting often feature a finer wire or wire loop, as opposed to a more flat blade with a rounded surface. Coagulation is performed using waveforms with lower average power, generating heat insufficient for explosive vaporization, but producing a thermal coagulum instead. Electrosurgical

desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...

occurs when the electrode touches the tissue open to air, and the amount of generated heat is lower than that required for cutting. The tissue surface and some of the tissue more deep to the probe dries out and forms a coagulum (a dry patch of dead tissue). This technique may be used for treating nodules under the skin where minimal damage to the skin surface is desired. In fulguration mode, the electrode is held away from the tissue, so that when the air gap between the electrode and the tissue is ionized, an

electric arc An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such as air produces a plasma; the plasma may produce visible light. ...

discharge develops. In this approach, the burning to the tissue is more superficial, because the current is spread over the tissue area larger than the tip of electrode. Under these conditions, superficial skin charring or carbonization is seen over a wider area than when operating in contact with the probe, and this technique is therefore used for very superficial or protrusive lesions such as skin tags. Ionization of an air gap requires voltage in the kV range. Besides the thermal effects in tissue, the electric field can produce pores in the cellular membranes – a phenomenon called

electroporation Electroporation, or electropermeabilization, is a microbiology technique in which an electrical field is applied to cells in order to increase the permeability of the cell membrane, allowing chemicals, drugs, electrode arrays or DNA to be introd ...

. This effect may affect cells beyond the range of thermal damage.

Wet field electrosurgery

There are wet and dry field electrosurgical devices. Wet field devices operate in a saline solution, or in an open wound. Heating is as a result of an alternating current that passes between two electrodes. Heating is usually greatest where the current density is highest. Therefore, it is usually the smallest or sharpest electrode that generates the most heat. Cut/Coag Most wet field electrosurgical systems operate in two modes: "Cut" causes a small area of tissue to be vaporized, and "Coag" causes the tissue to "dry" (in the sense of bleeding being stopped). "Dried" tissues are killed (and will later slough or be replaced by fibrotic tissue) but they are temporarily physically intact after electrosurgical application. The depth of tissue death is typically a few millimeters near the contact of the electrode. Cut If the voltage level is high enough, the heat generated can create a vapour pocket. 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. Coag When the system is operating in "coag mode" the voltage output is usually higher than in cut mode. Tissue remains grossly intact, but cells are destroyed at the point of contact, and smaller vessels are destroyed and sealed, stopping capillary and small-arterial bleeding.

Electrosurgical waveforms

Different

waveform In electronics, acoustics, and related fields, the waveform of a signal is the shape of its graph as a function of time, independent of its time and magnitude scales and of any displacement in time.David Crecraft, David Gorham, ''Electro ...

s can be used for different electrosurgical procedures. For cutting, a continuous single frequency

sine wave A sine wave, sinusoidal wave, or just sinusoid is a mathematical curve defined in terms of the '' sine'' trigonometric function, of which it is the graph. It is a type of continuous wave and also a smooth periodic function. It occurs often in ...

is often employed. Rapid tissue heating leads to explosive vaporization of

interstitial fluid In cell biology, extracellular fluid (ECF) denotes all body fluid outside the cells of any multicellular organism. Total body water in healthy adults is about 60% (range 45 to 75%) of total body weight; women and the obese typically have a lower ...

. If the voltage is sufficiently high (> 400 V peak-to-peak) the vapor sheath is ionized, forming conductive plasma. Electric current continues to flow from the metal electrode through the ionized gas into the tissue. Rapid overheating of tissue results in its vaporization, fragmentation and ejection of fragments, allowing for tissue cutting. 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. Open circuit voltage in electrosurgical waveforms is typically in the range of 300–10,000 V peak-to-peak. Higher precision can be achieved with pulsed waveforms. 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. Heat accumulation during repetitive application of bursts can also be avoided if sufficient delay is provided between the bursts, allowing the tissue to cool down. The proportion of ON time to OFF time can be varied to allow control of the heating rate. A related parameter,

duty cycle A duty cycle or power cycle is the fraction of one period in which a signal or system is active. Duty cycle is commonly expressed as a percentage or a ratio. A period is the time it takes for a signal to complete an on-and-off cycle. As a form ...

, is defined as the ratio of the ON time to the period (the time of a single ON-OFF cycle). In the terminology of

electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

, the process of altering this ratio to achieve an average amplitude, instead of altering the amplitude directly is called

pulse-width modulation Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts. The average value of voltage (and current) fed ...

. For coagulation, the average power is typically reduced below the threshold of cutting. Typically, sine wave is turned on and off in rapid succession. The overall effect is a slower heating process, which causes tissue to coagulate. In simple coagulation/cutting mode machines, the lower duty cycle typical of coagulation mode is usually heard by the ear as a ''lower frequency'' and a rougher tone than the higher frequency tone typical of cutting mode with the same equipment. Many modern electrosurgical generators provide sophisticated wave forms with power adjusted in real time, based on changes of the tissue impedance.

Prevention of unintended harm

;Burns For the high power surgical uses during anesthesia the ''monopolar modality'' relies on a good electrical contact between a large area of the body (Typically at least the entire back of the patient) and the return electrode or pad (also known as dispersive pad or patient plate). Severe burns (3rd degree) can occur if the contact with the return electrode is insufficient, or when a patient comes into contact with metal objects serving as an unintended (capacitative) leakage path to Earth/Ground. To prevent unintended burns, the skin is cleaned and a conductive gel is used to enhance the contact with the return electrode. Proper electrical grounding practices must be followed in the electrical wiring of the building. 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. Prior generators relied on single pad return electrodes and thus had no means of verifying safe patient connection. Return electrodes should always have full contact with the skin and be placed on the same side of the body and close to the body part where the procedure is occurring. If there is any metal in the body of the patient, the return electrode is placed on the opposite side of the body from the metal and be placed between the metal and the operation site. This prevents current from passing selectively through metal on the way to the return electrode. For example, for a patient who has had a right sided hip replacement who is scheduled for surgery, the return electrode is placed on the left side of the body on the lateral side of the lower abdomen, which places the return electrode between the location of the metal and the surgical site and on the opposite side from the metal. If there is metal on both sides of the body, the return electrode is placed between the metal and the procedure site when possible. Common return electrode locations include lateral portions of the outer thighs, abdomen, back, or shoulder blades. The use of the bipolar option does not require the placement of a return electrode because the current only passes between tines of the forceps or other bipolar output device. Electrosurgery should only be performed by a physician who has received specific training in this field and who is familiar with the techniques used to prevent burns. ;Smoke toxicity Concerns have also been raised regarding the toxicity of

surgical smoke Surgical smoke is the by-product produced by electrosurgery, laser tissue ablation, or other surgical techniques. Surgical smoke, as a health threat to those exposed to it, has become a growing concern. Studies have demonstrated, depending on seve ...

produced by electrosurgery. This has been shown to contain chemicals which may cause harm by inhalation by the patients, surgeon or operating theatre staff. ;Fire hazard Electrical knives should not be used around flammable substances, like alcohol-based disinfectants.Woman dies after being set on fire during surgery in Romania
The Guardian, 2019

History

Development of the first commercial electrosurgical device is credited to

William T. Bovie William T. Bovie (September 11, 1882 – January 1, 1958) was an American scientist and inventor. He is credited with conceptualizing the field of biophysics and with inventing a modern medical device known as the Bovie electrosurgical generator. ...

, who developed the first electrosurgical device while employed at

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of highe ...

. The first use of an electrosurgical generator in an operating room occurred on October 1, 1926 at

Peter Bent Brigham Hospital Brigham and Women's Hospital (BWH) is the second largest teaching hospital of Harvard Medical School and the largest hospital in the Longwood Medical Area in Boston, Massachusetts. Along with Massachusetts General Hospital, it is one of the two f ...

Boston Boston (), officially the City of Boston, is the state capital and most populous city of the Commonwealth of Massachusetts, as well as the cultural and financial center of the New England region of the United States. It is the 24th- mo ...

Massachusetts Massachusetts (Massachusett: ''Muhsachuweesut Massachusett_writing_systems.html" ;"title="nowiki/> məhswatʃəwiːsət.html" ;"title="Massachusett writing systems">məhswatʃəwiːsət">Massachusett writing systems">məhswatʃəwiːsət'' En ...

. The operation—removal of a mass from a patient’s head—was performed by

Harvey Cushing Harvey Williams Cushing (April 8, 1869 – October 7, 1939) was an American neurosurgeon, pathologist, writer, and draftsman. A pioneer of brain surgery, he was the first exclusive neurosurgeon and the first person to describe Cushing's disease ...

. The low powered

for office use was introduced in 1940.

Notes

{{reflist, 2

External links

A Simple Guide to the Hyfrecator 2000
Richard J Motley, Schuco International Ltd. a primer for low-powered outpatient dermatological devices, such as the Hyfrecator 2000 device.

Barry L. Hainer M.D., Richard B. Usatine, M.D., ''American Family Physician'' (Journal of the American Academy of Family Physicians), 2002 Oct 1;66(7):1259-66.

Online Journal of the Biomedical Engineering Association of Ireland (BEAI), May 1997.
Update on Electrosurgery
Judith Lee, Contributing Editor, ''Outpatient Surgery Magazine'', February, 2002. Dermatologic surgery Surgery Veterinary procedures