CONTINUING

MEDICAL EDUCATION

Electrosurgery Part I. Basics and principles Arash Taheri, MD,a Parisa Mansoori, MD,b Laura F. Sandoval, DO,a Steven R. Feldman, MD, PhD,a,b,c Daniel Pearce, MD,a and Phillip M. Williford, MDa Winston-Salem, North Carolina CME INSTRUCTIONS The following is a journal-based CME activity presented by the American Academy of Dermatology and is made up of four phases: 1. Reading of the CME Information (delineated below) 2. Reading of the Source Article 3. Achievement of a 70% or higher on the online Case-based Post Test 4. Completion of the Journal CME Evaluation

Learning Objectives After completing this learning activity, participants should be able to list the various electrosurgical modalities and describe their indications and contraindications; delineate the tissue effects of various electrical waveforms; recognize the factors influencing depth of tissue injury; and identify the sources of possible complications and describe strategies for the prevention of these complications.

CME INFORMATION AND DISCLOSURES Statement of Need: The American Academy of Dermatology bases its CME activities on the Academy’s core curriculum, identified professional practice gaps, the educational needs which underlie these gaps, and emerging clinical research findings. Learners should reflect upon clinical and scientific information presented in the article and determine the need for further study.

Date of release: April 2014 Expiration date: April 2017

Target Audience: Dermatologists and others involved in the delivery of dermatologic care. Accreditation The American Academy of Dermatology is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. AMA PRA Credit Designation The American Academy of Dermatology designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditsÔ. Physicians should claim only the credit commensurate with the extent of their participation in the activity. AAD Recognized Credit This journal-based CME activity is recognized by the American Academy of Dermatology for 1 AAD Credit and may be used toward the American Academy of Dermatology’s Continuing Medical Education Award. Disclaimer: The American Academy of Dermatology is not responsible for statements made by the author(s). Statements or opinions expressed in this activity reflect the views of the author(s) and do not reflect the official policy of the American Academy of Dermatology. The information provided in this CME activity is for continuing education purposes only and is not meant to substitute for the independent medical judgment of a healthcare provider relative to the diagnostic, management and treatment options of a specific patient’s medical condition. Disclosures Editors The editors involved with this CME activity and all content validation/peer reviewers of this journal-based CME activity have reported no relevant financial relationships with commercial interest(s). Authors Dr Feldman is a consultant and speaker, has received grants, or has stock options in Abbott Labs, Amgen, Anacor Pharmaceuticals, Inc, Astellas, Caremark, Causa Research, Celgene, Centocor Ortho Biotech Inc, Coria Laboratories, Dermatology Foundation, Doak, Galderma, Gerson Lehrman Group, Hanall Pharmaceutical Co Ltd, Informa Healthcare, Kikaku, Leo Pharma Inc, Medical Quality Enhancement Corporation, Medicis Pharmaceutical Corporation, Medscape, Merck & Co, Inc, Merz Pharmaceuticals, Novan, Novartis Pharmaceuticals Corporation, Peplin Inc, Pfizer Inc, Pharmaderm, Photomedex, Reader’s Digest, Sanofi-Aventis, SkinMedica, Inc, Stiefel/GSK, Suncare Research, Taro, US Department of Justice, and Xlibris. Drs Taheri, Mansoori, Sandoval, Williford, and Pearce have no conflicts of interest to declare. Planners The planners involved with this journal-based CME activity have reported no relevant financial relationships with commercial interest(s). The editorial and education staff involved with this journal-based CME activity have reported no relevant financial relationships with commercial interest(s). Resolution of Conflicts of Interest In accordance with the ACCME Standards for Commercial Support of CME, the American Academy of Dermatology has implemented mechanisms, prior to the planning and implementation of this Journal-based CME activity, to identify and mitigate conflicts of interest for all individuals in a position to control the content of this Journal-based CME activity.

Ó 2013 by the American Academy of Dermatology, Inc. http://dx.doi.org/10.1016/j.jaad.2013.09.056 Technical requirements: American Academy of Dermatology: d Supported browsers: FireFox (3 and higher), Google Chrome (5 and higher), Internet Explorer (7 and higher), Safari (5 and higher), Opera (10 and higher). d JavaScript needs to be enabled. Elsevier: Technical Requirements This website can be viewed on a PC or Mac. We recommend a minimum of: d PC: Windows NT, Windows 2000, Windows ME, or Windows XP d Mac: OS X d 128MB RAM d Processor speed of 500MHz or higher d 800x600 color monitor d Video or graphics card d Sound card and speakers Provider Contact Information: American Academy of Dermatology Phone: Toll-free: (866) 503-SKIN (7546); International: (847) 240-1280 Fax: (847) 240-1859 Mail: P.O. Box 4014; Schaumburg, IL 60168 Confidentiality Statement: American Academy of Dermatology: POLICY ON PRIVACY AND CONFIDENTIALITY Privacy Policy - The American Academy of Dermatology (the Academy) is committed to maintaining the privacy of the personal information of visitors to its sites. Our policies are designed to disclose the information collected and how it will be used. This policy applies solely to the information provided while visiting this website. The terms of the privacy policy do not govern personal information furnished through any means other than this website (such as by telephone or mail). E-mail Addresses and Other Personal Information - Personal information such as postal and e-mail address may be used internally for maintaining member records, marketing purposes, and alerting customers or members of additional services available. Phone numbers may also be used by the Academy when questions about products or services ordered arise. The Academy will not reveal any information about an individual user to third parties except to comply with applicable laws or valid legal processes. Cookies - A cookie is a small file stored on the site user’s computer or Web server and is used to aid Web navigation. Session cookies are temporary files created when a user signs in on the website or uses the personalized features (such as keeping track of items in the shopping cart). Session cookies are removed when a user logs off or when the browser is closed. Persistent cookies are permanent files and must be deleted manually. Tracking or other information collected from persistent cookies or any session cookie is used strictly for the user’s efficient navigation of the site. Links - This site may contain links to other sites. The Academy is not responsible for the privacy practices or the content of such websites. Children - This website is not designed or intended to attract children under the age of 13. The Academy does not collect personal information from anyone it knows is under the age of 13. Elsevier: http://www.elsevier.com/wps/find/privacypolicy.cws_home/ privacypolicy

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The term electrosurgery (also called radiofrequency surgery) refers to the passage of high-frequency alternating electrical current through the tissue in order to achieve a specific surgical effect. Although the mechanism behind electrosurgery is not completely understood, heat production and thermal tissue damage is responsible for at least the majority—if not all—of the tissue effects in electrosurgery. Adjacent to the active electrode, tissue resistance to the passage of current converts electrical energy to heat. The only variable that determines the final tissue effects of a current is the depth and the rate at which heat is produced. Electrocoagulation occurs when tissue is heated below the boiling point and undergoes thermal denaturation. An additional slow increase in temperature leads to vaporization of the water content in the coagulated tissue and tissue drying, a process called desiccation. A sudden increase in tissue temperature above the boiling point causes rapid explosive vaporization of the water content in the tissue adjacent to the electrode, which leads to tissue fragmentation and cutting. ( J Am Acad Dermatol 2014;70:591.e1-14.) Key words: coagulation; current; electricity; electrocoagulation; electrodesiccation; electrofulguration; electrosurgery; high frequency; radiofrequency.

INTRODUCTION Key points d

d

In electrosurgery, an electric current flows from the active electrode through the patient’s body to the return electrode Electrocautery differs from electrosurgery in that an electrical current heats a metallic probe that is then applied to tissue (hot iron cautery). Because no heat is generated in deeper tissue, electrocautery is more suitable for the destruction of superficial tissue layers

The concept of using heat for hemostasis goes back hundreds of years. As technology evolved, devices were created that used electricity to heat tissue and control bleeding. These advancements eventually developed into modern-day electrosurgery. The term electrosurgery (also called radiofrequency surgery) refers to the passage of high-frequency electrical current through the tissue in order to achieve a specific surgical effect, such as cutting or coagulation (Table I). Each electrosurgical device consists of a high frequency electrical generator and 2 electrodes (Fig 1). The electric current flows from the active electrode through the patient’s body and then to the return (dispersive) electrode,

From the Center for Dermatology Research, Departments of Dermatology,a Pathology,b and Public Health Sciences,c Wake Forest School of Medicine. The Center for Dermatology Research is supported by an unrestricted educational grant from Galderma Laboratories, L.P. Dr Feldman is a consultant and speaker, has received grants, or has stock options in Abbott Labs, Amgen, Anacor Pharmaceuticals, Inc, Astellas, Caremark, Causa Research, Celgene, Centocor Ortho Biotech Inc, Coria Laboratories, Dermatology Foundation, Doak, Galderma, Gerson Lehrman Group, Hanall Pharmaceutical Co Ltd, Informa Healthcare, Kikaku, Leo Pharma Inc, Medical Quality Enhancement Corporation, Medicis

where current flows back to the electrosurgical generator. Adjacent to the active electrode, tissue resistance to the passage of alternating current converts electrical energy to heat, resulting in thermal tissue damage. While heat generation occurs within the tissue, the treatment electrode acts as a conductor that only passes the current and may remain cooler than the treated medium.1,2 Electrocautery differs from electrosurgery in that an electrical current heats a metallic probe that is then applied to tissue (hot iron cautery). In electrocautery, no current flows through the patient’s body (Fig 2).3 Because no heat is generated in deeper tissue, electrocautery is more suitable for the destruction of superficial tissue layers. The term diathermy was originally applied to the therapeutic (nonablative) heating effect of passing high-frequency electrical current through deeper parts of the body. This term was later used to describe cutting tissue.4,5 While the term diathermy is still used today, the term electrosurgery is preferred when referring to cutting or coagulation. Although electrosurgical instruments are used routinely, familiarity with the principles behind how these instruments produce their effect is limited.6,7 An understanding of the basic principles of electrosurgery can help increase efficiency of use and reduce complications.

Pharmaceutical Corporation, Medscape, Merck & Co, Inc, Merz Pharmaceuticals, Novan, Novartis Pharmaceuticals Corporation, Peplin Inc, Pfizer Inc, Pharmaderm, Photomedex, Reader’s Digest, Sanofi-Aventis, SkinMedica, Inc, Stiefel/GSK, Suncare Research, Taro, US Department of Justice, and Xlibris. Drs Taheri, Mansoori, Sandoval, Williford, and Pearce have no conflicts of interest to declare. Reprint requests: Arash Taheri, MD, Department of Dermatology, Wake Forest School of Medicine, 4618 Country Club Rd, Winston-Salem, NC 27104. E-mail: [email protected]. 0190-9622/$36.00

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Table I. Electrosurgical modes and definition of common terms used in electrosurgery Method

Electrical current or mode of choice

Alternative currents

Electrocautery

Direct current

Electrosurgery

High-frequency alternating current

Electrocoagulation (contact coagulation)

Continuous current (cutting mode)*

Interrupted currents (eg, blend, coagulation, or fulguration modes)

Electrodesiccation

Same as electrocoagulation

Same as electrocoagulation

Electrofulguration (spray or noncontact coagulation)

Interrupted current (fulguration mode)

Interrupted current (coagulation mode)

Electrosection, pure cutting

Continuous current (cutting mode)

—

Electrosection, blend cutting

Interrupted current (blend or coagulation modes)

—

Bipolar electrosurgery Monopolar electrosurgery

Bipolar mode Monopolar modes (for cutting, coagulation, desiccation, and fulguration) Biterminal electrosurgery All modes (for cutting, coagulation, desiccation, and fulguration) Monoterminal electrosurgery All modes except for pure cutting (monoterminal mode is not suitable for pure cutting)

Alternating current

—

— —

—

—

Definition

An electrical current heats a metallic probe that is then applied to tissue A high-frequency electrical current is passed through the tissue in order to achieve a specific surgical (thermal) effect, such as cutting or coagulation The tissue is heated below the boiling point and undergoes thermal denaturation Vaporization of the water content and drying occurs at superficial tissue layers at the end of coagulation The active electrode is held a few millimeters above the tissue. The electric current bridges the air gap by creating a spark A sudden increase in tissue temperature above the boiling point leads to tissue fragmentation and cutting. In pure cutting, there is little coagulation on the incision walls and little hemostasis In blend cutting, there is more coagulation on the incision walls and more hemostasis than pure cutting There are 2 active electrodes There is 1 active and 1 dispersive (return) electrode Both active and return electrodes are in contact with the patient’s body Return electrode is not connected directly to the patient’s body; instead, it is connected to the Earth and the Earth acts as an indirect return electrode

*The cutting mode in some electrosurgical units cannot provide a very low power output that is necessary for a superficial coagulation using a fine-tip electrode.

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Fig 1. An electrosurgery circuit. Current flows through the tissue, generating heat within the tissue. Heat generation is practically limited to the area of high current density, meaning adjacent to the active electrode. The characteristics of the current flow affect the depth, speed, and degree of tissue heating and determine the tissue results. The arrows indicate the direction of the electricity in 1 phase of current. In the next phase, the current will be in the opposite direction.

Fig 2. An electrocautery circuit. No current flows through the patient’s body. Current heats the tip of the probe, which can then be used to heat superficial tissue layers.

FUNDAMENTALS OF ELECTRICITY Key points d

d

d

d

In a high-frequency alternate current circuit, cables and pathways of electricity always form capacitors with each other and with nearby conductive environmental objects. Therefore, all insulation on instruments and cables is relative and some energy always leaks through it as a capacitive current If the active electrode cable comes in close proximity to the patient’s body, current leakage may result in a burn When a direct or low-frequency current enters the body, a chemical reaction called electrolysis occurs at the electrodeetissue interface. The chemical effects of electrolysis disappear at higher frequencies A direct or low frequency current can depolarize cell membranes and cause neuromuscular excitation. Neuromuscular stimulation becomes negligible at higher frequencies

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Fig 3. The peak and average voltage of alternating electrical currents. The left waveform has a higher ratio of average to peak voltage than the right waveform.

Electricity and currents There are 2 types of electrical current: direct and alternating. Direct current uses a simple circuit and flows only in 1 direction, whereas alternating current switches, or alternates, the direction of the flow of electricity back and forth. Household electrical wall outlets, for example, have alternating currents. During each phase of an alternating current, voltage and current fluctuate between a maximum (peak) and a minimum (0). The effective or average voltage is lower than the peak voltage (Fig 3) and is usually used to describe an alternate current source and to calculate the power. A continuous circuit must be present in order for a direct current to flow. However, an alternating current can pass through some breaks and insulations by several mechanisms, the most important of which is capacitance. In its simplest form, a capacitor consists of 2 nearby conducting plates separated by a nonconducting medium (Fig 4). Higher frequency alternating currents can pass a capacitor more easily than lower frequency alternating currents. The flow of an alternating current through a capacitor is known as a capacitive current. In an alternate current circuit, cables and pathways of electricity always form capacitors with each other and with nearby conductive environmental objects. Therefore, high-frequency alternating currents are impossible to insulate completely. All insulation on instruments and cables is relative, and some energy always leaks through insulations as capacitive current.8,9 In an electrosurgery circuit, the tissue adjacent to the active electrode acts as a resistor that induces heating (Fig 1). If the active electrode cable comes in close proximity to the dispersive electrode cable or

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Fig 4. An alternate current circuit with a generator, a resistor (R), and a capacitor (C). A capacitor consists of 2 nearby conducting plates separated by a nonconducting medium. When a direct current voltage source is applied to a capacitor, there is an initial surge of current. Electrons flow into 1 of the plates, giving it a negative charge, and are taken off the other plate, causing that plate to become positively charged. While the capacitor is charging, current flows, usually for a fraction of a second. The current will stop flowing when the capacitor has fully charged. However, if the current changes its direction, as in the case of an alternating current, the current will flow and charge the capacitor every time the electricity changes direction. Therefore, some current will be allowed to pass in each phase of the cycle. As the frequency of alternations increases, more current passes the capacitor every second. The result is that higher frequency alternating currents can pass the capacitor more easily than lower frequency alternating currents.

to the patient’s body, a capacitor is formed that passes some of the current through an alternate path (Fig 5). This is called current leakage.10 Current leakage may result in a burn on the patient or anyone that comes in contact with the cable (Fig 5).11 As detailed earlier, higher frequency alternating currents can pass the capacitors more easily than lower frequency currents. Ultra-high frequencies ([5 MHz) are not used in electrosurgery because the leakage effect is too great to fall within the limits set by safety standards.12,13 Electricity and biologic tissues Electrical conduction differs depending on the conductive material. In metals, the charge carriers are primarily electrons, whereas in gases and liquids the carriers are ions.14,15 Gases are nonconductive materials. When a nonconductive gas is placed in a sufficiently high voltage electric field (eg, between the 2 poles of a high-voltage generator), the gas will be ionized. This ionized gas is called plasma and conducts the electrical current as a spark. Two common examples of plasma are lightning in nature and fulguration in electrosurgery. Electrical conduction in biologic tissues is primarily caused by the conductivity of body fluids and is therefore predominantly ionic.16,17

A

F

B

C Fig 5. Current leakage in electrosurgery circuit. Current leakage from active electrode cable to the patient’s body may result in a burn. It can occur as a result of putting the active cable near the patient’s body (A) or near any conductive element that is in direct contact or close contact to the patient’s body or surgical staff (B; object F). Examples of object F can be a surgical table or a metallic clamp that is used for securing the cable to the surgical drapes over the patient’s body. On the other hand, if the active and dispersive electrode cables are put near each other, current will leak from the active to dispersive electrode cable before reaching the active electrode (C). As a result of this power loss, the power dissipated in tissue will be less than the output power of the generator.

Chemical effects of electrical currents on tissues When a direct current enters the body through a metallic electrode, a chemical reaction called

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Fig 6. Electromagnetic spectrum. Electrosurgical units use alternating currents with frequencies which are part of the radio-wave frequency range.

electrolysis occurs at the electrodeetissue interface. This chemical reaction may cause destruction of a thin layer of tissue around the electrode very slowly.18 Electrolysis has been used as a method of hair removal (galvanic depilation) and for the treatment of telangiectasia.19-21 A low-frequency alternating current can cause similar chemical reactions. However, because the chemical reaction of each phase can be neutralized by the opposite phase, these chemical effects diminish as the frequency of alternations increase and almost disappear at high frequencies ([5 to 10 kHz).2,17,22-26

d

d

d

Effects of electrical currents on cell membranes A direct or low-frequency alternate current can depolarize cell membranes and cause neuromuscular excitation. This stimulation may cause pain, muscle contraction, and even cardiac arrhythmia. Neuromuscular stimulation decreases as the frequency of current increases above 1 kHz, and becomes negligible at frequencies of 100 to 300 kHz.22,23,26-28 At these high frequencies, current reversal is so rapid that cellular ion position change is essentially nil and depolarization fails to occur. High-frequency alternating current therefore makes it possible to exploit the heating effects of electricity while avoiding the undesirable neuromuscular effects. Whereas physiologic reasons dictate the lower limit of the frequency used, as detailed earlier, practical and safety considerations place restrictions on the upper limit of current frequency used by electrosurgical units. Electrosurgical units typically produce alternating currents in the frequency range of 0.3 to 5 MHz. These frequencies are part of the radiowave frequency range (Fig 6); this is why electrosurgery is also called radiofrequency (RF) surgery or high-frequency electrosurgery. Although these terms are used synonymously, the term electrosurgery has a more specific meaning in applied biomedical engineering and is the preferred term.10,29,30

BASIC MECHANISM OF ELECTROSURGERY Key points d

An active electrode can concentrate the current at a small area and provide a sufficiently

high current density to induce heating and thermal tissue damage. The large return electrode disperses the current, reducing the current density to levels where tissue heating is minimal Electrocoagulation occurs when tissue is heated below the boiling point and undergoes thermal denaturation An additional slow increase in temperature leads to vaporization of the water content and tissue drying, a process called desiccation A sudden increase in tissue temperature above the boiling point causes rapid explosive vaporization of the water content in the tissue adjacent to the electrode, which then leads to tissue fragmentation and cutting

Although precisely how electrosurgery works is not completely understood, heat production and thermal tissue damage caused by tissue resistance to the passage of the alternating electrical current is responsible for at least the majority—if not all—of the tissue effects in electrosurgery.16,29,31-34 The electrical current is applied to the surgical site with a small active electrode and is collected by a largesurface return electrode that is attached to the patient’s body. An active electrode can concentrate the current at a small area in its immediate vicinity and provide a sufficiently high current density to induce heating and thermal tissue damage.16,29 The large return electrode disperses the current, reducing the current density to levels where tissue heating is minimal. Electrocoagulation occurs when tissue is heated below the boiling point and undergoes thermal denaturation.29 An additional slow increase in temperature leads to vaporization of the water content in the coagulated tissue and tissue drying, a process called desiccation. As more superficial coagulated tissues dry out, they become less electrically conductive, potentially preventing the current from continuing to flow and heat the tissue, thereby limiting the depth of coagulation. A sudden increase in tissue temperature above the boiling point results in rapid explosive vaporization of the water content in the tissue adjacent to the electrode. This leads to tissue fragmentation, which

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Fig 7. Different alternating electrosurgical current waveforms at equivalent output power settings. Cutting mode uses a continuous waveform that is able to provide the maximum output power of the generator. Coagulation mode uses an intermittent waveform that pulses on and off thousands of times per second. Coagulation waveform usually has a lower maximum power than cutting waveform because the delivery of the current is off for some periods of time. A coagulation waveform incorporates higher voltage than a cut waveform at the same power setting. Fulguration mode has the highest peak voltage ($ 10,000 volts), which helps with large spark formation. Interrupted modes have a higher ratio of peak to average voltage than continuous mode. In previous generations of electrosurgical units, damped currents were commonly used to provide currents with high ratio of peak to average voltage. Theoretically, the surgical effects of damped currents are not different from interrupted undamped currents.

allows the electrode to pass through the tissue and is the mechanism of tissue cutting in electrosurgery (electrosection).35-37

CURRENT WAVEFORMS Key points d

d

d

Cutting mode uses a continuous waveform that is able to provide the maximum output power of the generator Intermittent currents have a lower maximum power and a higher ratio of peak-to-average voltage than a continuous current Fulguration mode usually has the highest peak voltage

Electrosurgical generators are able to produce a variety of electric waveforms (Fig 7). The name of each waveform or mode does not necessarily translate to the final effect the mode has on tissue (Table I). The only variable that determines the final tissue effects of a current is the depth and the rate at which heat is produced. The waveform, voltage, and power of electrosurgical current and the size of electrode tip can affect the depth and the rate of heat production and indirectly influence the final effect of current on the tissue.29,38,39 In an intermittent waveform, the voltage, amperage, and power fluctuate between 0 or

minimum in off phases and maximum in on phases. In this article, we use the term peak voltage to refer to maximum voltage of the current during on phases and the terms amperage and power to refer to the mean amperage and mean power of the current.

ELECTROSURGICAL MODALITIES Electrocoagulation Key points d Coagulation can be performed in contact mode or in spray (fulguration) mode. However, the term electrocoagulation is usually used to refer to electrocoagulation in contact mode d At the end of contact electrocoagulation, the more superficial coagulated tissues may dry out (desiccation). The current may decrease or stop flowing at this time, a popping sound may be heard, and sparking may occur through the dried, nonconductive layer, leading to explosion and fragmentation of the dried layer d Practically, a fine-tip electrode can be best used for superficial electrocoagulation and a large-tip electrode with a large contact area only for deep coagulation d In contact mode, depth of coagulation is proportional to the size of electrode tip,

Depth of tissue injury

Size of area

Superficial destruction Small with low collateral damage

Large

Medium depth destruction with some collateral damage

Small to large

Method of application of current

Electrical current or mode of choice

Alternative currents

Setting

Possible indications*

Continuous current (cutting mode)

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Small seborrheic keratosis, Usually a very low power Interrupted current freckle, lentigo, plane setting is used. The (blend or coagulation wart, common wart, power is started very low modes) genital wart, molluscum and is increased until a contagiosum, dermatosis reasonably fast papulosis nigra, very movement of the small skin tag, syringoma, electrode on the target cherry angioma, spider can be attained. angioma and Coagulated materials can telangiectasia, and be wiped off and a sebaceous hyperplasia second pass may be performed if necessary Fine- or large-tip Interrupted current Interrupted current Depending on the speed of Seborrheic keratosis, electrode and verrucous epidermal (fulguration mode) (coagulation mode) movement of electrode, fulgurationy (spray) nevus, and rhinophyma a low to medium power setting is used. The method power is started low and is increased until a reasonably fast movement of the electrode on the target can be attained. Coagulated materials can be wiped off and a second pass may be performed if necessary Medium-tip electrode Genital wart,z rhinophyma, Needs more power than Depending on the Interrupted currents and contact method, superficial destruction. If method (see above) (blend or coagulation Bowen disease, actinic or fine- or large-tip curettage or shaving is modes) keratosis, mucous cysts, electrode and performed before and pyogenic fulgurationy (spray) electrosurgery, granulomax achievement of method hemostasis using electrosurgery can be (but not necessarily) an indicator of adequacy of treatment Fine-tip electrode and contact method

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Table II. Settings of electrosurgical units for destruction/coagulation based on the indication and type of procedure46-57

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*Although electrosurgery can be used for the mentioned indications, it is not necessarily the treatment of choice. y Depending on the power and the speed of movement of the electrode on the target, electrofulguration potentially can induce either a very superficial or a relatively deep destruction. z Because of the risk of viral transmission through the smoke, electrofulguration is not a preferred method for the treatment of viral warts. x Fragile tumors can be treated using curettage and electrodesiccation as an alternative to excision. However, depending on variables, such as tumor type, location, and size, for many cases of basal cell carcinoma and keratoacanthoma and most cases of squamous cell carcinoma excision rather than curettage and electrodesiccation is preferred.

Continuous current (cutting mode) Small to large Loop excision

A thin wire in loop shape

Medium Large-tip electrode to large and contact method Deep destruction (usually used as an alternative to excision)

Continuous current (cutting mode)

Basal cell carcinoma,x Medium to high power Interrupted currents setting. The power (blend or coagulation keratoacanthoma,x and should be enough for a modes) squamous cell slow desiccation (hearing carcinomax a popping sound after a few second). The slower desiccation process, the deeper damage Interrupted currents The type of the current and An alternative to shave excision and hemostasis; (blend or coagulation the power setting should not suitable for biopsy modes) be selected depending for histopathologic on the amount of desired evaluation; rhinophyma hemostasis

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d

power, and duration of activation time. However, a relatively low power may be able to provide a deeper maximum coagulation depth than a higher power because of delayed occurrence of desiccation with lower power Fulguration mode can provide a superficial coagulation if a relatively low power is used. It can cause deeper tissue damage if a relatively higher power is used or if the activated electrode is kept over a confined area for a longer period of time

The rate at which the tissue temperature rises is proportional to the current density in tissue. For coagulation, the current density is lower than that used for cutting to prevent tissue explosion and fragmentation. Electrocoagulation can be performed in contact mode or in spray (fulguration) mode. However, the term electrocoagulation is usually used to refer to electrocoagulation in contact mode. For superficial coagulation of small areas (eg, the destruction of small seborrheic keratoses) a fine-tip electrode should be used to concentrate the current to a fine point (Table II). This allows the same tissue effect to be achieved with a lower power setting. When using a fine-tip electrode, the current density in tissue rapidly decreases with distance from the electrode (Fig 8); therefore, heat generation is practically confined to the vicinity of the electrode tip, potentially decreasing the depth of dermal damage and possibility of visible scar formation.25 When using a large-tip electrode with a large electrodeetissue contact surface, a higher power output should be used to achieve the desired current density and tissue effect (Fig 8).40 Current density decreases with distance from the electrode surface more slowly compared to a fine electrode. A higher power output (higher amperage) and slower decrease in current density leads to presence of a higher current density in deeper layers, resulting in deeper tissue injury. A large electrode tip (ie, ball- or disc-shaped electrodes), therefore, should be used only for deep coagulation (eg, the destruction of reticular dermis after curettage of a malignant skin tumor).41 Because superficial coagulation of large areas (eg, the destruction of large, flat seborrheic keratoses or hemostasis of oozing surfaces) using a fine-tip electrode is a slow process and takes time, spray mode coagulation or electrofulguration was developed (Table II). In electrofulguration, the active electrode is held a few millimeters above the tissue. Using an

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Fig 8. Electrocoagulation. A fine-tip electrode needs a low power setting and is suitable for superficial coagulation. A large-tip electrode is suitable for deep coagulation. A large electrode cannot provide a superficial coagulation because current density decreases with distance from the electrode surface slowly.

interrupted high-peaked voltage output (fulguration mode), the gap of air between the electrode and the tissue will be bridged by an electric discharge arc (spark). The arc rapidly jumps and moves from one location to the other, reestablishing itself at different locations. In this approach, the current is spread over an area larger than that of just the tip of the electrode.42 By moving the electrode and spraying the current over tissue, coagulation can be achieved on a large surface area faster than when operating in contact with tissue. Spray coagulation can be achieved with a fine- or large-tip electrode. In electrofulguration, each spark carries the current to a very small point at a moment, acting as a very fine electrode. Given a relatively low power, the temperature is extremely high only at the end of each spark, leading to tissue explosion and fragmentation or charring. However, the temperature drops rapidly with increased distance from the end of the spark, and thermal damage is contained. Therefore, tissue destruction and coagulation appears within a thin superficial layer of tissue, and fulguration can be

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suitable for superficial tissue destruction. However, if a fulgurating electrode is kept over a confined area, continuous heat production on the superficial layers can cause heating of deeper layers, primarily via heat conduction. In such cases, fulguration can potentially cause deep coagulation. During electrocoagulation, the more superficial tissues may dry out. This stage of coagulation, called desiccation, is important because the current may decrease or stop flowing at this time, limiting the maximum depth of coagulation (Fig 9). When this occurs, a popping sound may be heard and/or sparking may occur through the dried nonconductive layer, leading to explosion and fragmentation of the dried layer. Desiccation is not a method or a distinctive final result—it is only a stage that may or may not happen, and it may happen at any time during the course of coagulation, regardless of the depth of the coagulated tissue. The timing of the occurrence of desiccation during the course of coagulation depends on the rate of increase in temperature that is the result of current density. With lower current density, there may be a deep coagulation before desiccation happens.29 Therefore, for deep coagulation (eg, after curettage of a malignant skin tumor), a relatively low power should be chosen to provide a slow coagulation and late occurrence of desiccation. However, a very low power may not be able to provide the desired coagulation. Although there are no published data, it seems that choosing a power which can provide desiccation (popping sound) after 4 to 7 seconds can result in a relatively deep destruction. Achievement of hemostasis is not necessarily an indicator of a deep coagulation. It seems that definitions have at times hindered a higher level of understanding of electrosurgery. The term electrodesiccation has been used in literature as a distinctive method from coagulation. Some authors use the term electrodesiccation to refer to monoterminal electrocoagulation while reserving the term electrocoagulation to refer to biterminal electrocoagulation.18,43,44 Others use the term electrodesiccation to refer to contact electrocoagulation as opposed to spray electrocoagulation (fulguration).13,45 A common and appropriate usage of the term electrodesiccation is in reference to a deep contact coagulation caused by a large electrode up to the stage of tissue drying.29 This use of ‘‘electrodesiccation’’ is what is referred to in ‘‘electrodesiccation and curettage,’’ a widely used surgical technique in dermatologic surgery. Although tissue drying may also occur during fulguration, the term electrodesiccation is mainly used to refer to the final stage of contact mode coagulation.

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during destruction of flat seborrheic keratoses), the activation time should be short or divided into multiple pulses separated by periods of time long enough to allow the tissue to cool before the next pulse.

A

B

C Fig 9. Electrocoagulation and electrodesiccation. The process starts with coagulation (A). At the end of coagulation, the more superficial coagulated tissue dries out (desiccation) and become less electrically conductive, potentially preventing the current from continuing to flow (B). However, sparking may then occur through the nonconductive desiccated layer, leading to disruption of this layer, passage of more current, more heat production, and deeper thermal damage (C).

Factors influencing the depth of coagulation While the amount of heat generation and resulting tissue damage is proportional to the electrodeetissue contact surface area (ie, the size of the electrode tip) and the power setting (ie, waveform and voltage) used, it also depends on the duration of active contact between the active electrode and tissue. A longer activation time results in more heat generation and wider and deeper tissue damage. One may propose that choosing a low power setting and a longer activation time is safer and produces the same result as choosing a higher power and a shorter activation time. However, this is not the case. Longer activation times result in more heat conduction and collateral tissue damage before the desired outcome is attained.11,40 This is similar to choosing pulse duration of lasers. Therefore, in order to minimize the collateral tissue damage (eg,

Electrosection Key points d For a pure cutting (relatively clean incision with little hemostasis) a thin electrode and a continuous cutting current (cut mode) is used. The cutting of the tissue should be brisk, using the lowest possible power setting d A thick electrode cannot provide a pure clean cut d Blend cutting can be performed using an interrupted current (blend or coagulation mode) Electrosection provides a means of cutting tissue in place of a scalpel. The major advantage of this method of cutting is that hemostasis is achieved immediately upon incision by coagulation on either side of the incision wall. Larger blood vessels may still require additional spot coagulation at the completion of the cutting to achieve hemostasis. A thin needle or wire can concentrate current on a small area in the same way that a fine-tip coagulation electrode does, and allows the same cutting effect to be achieved with a lower power setting. This leads to less heat production and less collateral tissue coagulation compared with a thicker electrode.37,58 Therefore, a thin needle or wire is used to make a relatively clean incision with minimal coagulation and hemostasis on either side of the incision wall (Fig 10). A thick needle electrode can cut through the tissue if a very high power current is used. In this case, current density and temperature decreases from electrode more slowly compared with a thin electrode.25 The result is a deeper coagulation margin during cutting that leads to more effective hemostasis and also more tissue damage. This mode is called blend cut, meaning a blend of cutting and coagulation (Fig 10). When the cutting electrode comes in contact with the tissue, an initial tissue heating and explosive vaporization of the medium around the electrode leads to isolation of the metallic electrode from the tissue. Ionization of the vapor around the electrode allows maintaining the current through the vapor cavity by spark. Therefore, the cutting may continue without a direct contact between the active electrode and tissue.25,35 The higher the peak voltage of the

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essentially ‘‘sticking.’’34 If large arcing or sparking is seen across the surface of the tissue, the voltage is too high and should be appropriately reduced. Practically, after determining the best power setting, this setting can be used for each successive patient, maybe with some fine tuning.

Fig 10. Cross section of tissue with 3 cutting electrodes. Left, A thin needle is able to concentrate a lowepeaked voltage, low-power current (cutting current with relatively low power) on a small area and make a relatively clean incision with very little coagulation on the incision walls. Middle, A thick electrode can cut through the tissue if a higher power current is used. The result is deeper coagulation margins. Right, A highepeaked voltage current (blend or coagulation waveforms) produces large sparks and acts as if a thicker electrode is being used that cannot concentrate the current.

current, the larger the sparks. Larger sparks can spread current to a wider area of tissue around the electrode and act as if a thicker electrode is being used that cannot concentrate the current in a small area, resulting in a deeper coagulation (Figs 8 and 10).24 Therefore, an interrupted highepeak voltage current provides deeper collateral tissue coagulation on either side of the incision walls and better hemostasis than a continuous lowepeak voltage current (Figs 7 and 10).29,59 Blend mode or coagulation mode currents have a higher ratio of peak to average voltage than pure cut currents and can be used for making a blend cut. Depending on the technique used, the depth of coagulation on either side of an electrosurgical incision varies from 0.1 to 2 mm.60-62 Fulguration mode currents have a very high ratio of peak to average voltage (Fig 7) and produce very thick coagulation on the incision walls if used for cutting. While there are conflicting reports of postoperative results comparing pure electrosection of the skin to scalpel surgery, electrosection, especially blend cut, is seldom used when a primary closure is planned.63-66 In order to have less collateral tissue damage and coagulation on the incision walls, contact time should be reduced to minimize heat production and conduction.11 Therefore, the cutting of the tissue should be brisk with the lowest effective power setting.36,37 When the power setting is too low, the cutting process may be slow, resulting in wider collateral coagulation.36 The correct output power for a clean incision can be determined by starting low and increasing the power until the maximum cutting speed can be attained. If the power is insufficient, the electrode does not glide through the tissue easily,

CONCLUSIONS The superficial coagulation of small areas (eg, small, flat, benign epidermal tumors) can be performed with a fine-tip electrode. Cutting, blend, coagulation, or fulguration mode currents can be used; however, fulguration or coagulation mode currents are more likely to cause tissue fragmentation and deeper destruction by producing spark through the desiccated tissues. Therefore, fulguration current should be avoided for a very superficial coagulation in contact mode (contact coagulation). On the other hand, the cutting mode in some electrosurgical units cannot provide a very low power output that is necessary for a superficial coagulation using a fine-tip electrode. In this case, coagulation mode, which may have a lower minimum output power, may be used. A large-tip electrode is used for deep coagulation of a large area. A high power is usually necessary; therefore, the cutting mode may be needed. Making a relatively clean incision with little hemostasis (pure cutting) requires a thin electrode and a cutting current (cut mode). Blend cutting can be performed using an interrupted current (ie, blend or coagulation mode). Cutting mode current is suitable for all electrosurgical methods except for fulguration, which requires a higher peak voltage. This is the reason some electrosurgical units only provide cut and fulguration modes. A knowledgeable selection of the electrosurgical circuit, electrode configuration, power, waveform, voltage, and activation time is necessary for achieving the best possible surgical results. Surgeons should be familiar with the principles of electrosurgery and its electrophysical properties. REFERENCES 1. Rey JF, Beilenhoff U, Neumann CS, Dumonceau JM. European Society of Gastrointestinal Endoscopy (ESGE) guideline: the use of electrosurgical units. Endoscopy 2010;42:764-72. 2. Huntoon RD. Tissue heating accompanying electrosurgery: an experimental investigation. Ann Surg 1937;105:270-90. 3. Swerdlow DB, Salvati EP, Rubin RJ, Labow SB. Electrosurgery: principles and use. Dis Colon Rectum 1974;17:482-6. 4. Turrell WJ. Treatment by diathermy. Br Med J 1923;1:143-5. 5. Wilson D. Discussion on the present position of short-wave diathermy and ultrasonics. Proc R Soc Med 1953;46:331-8. 6. Feldman LS, Fuchshuber P, Jones DB, Mischna J, Schwaitzberg SD. Surgeons don’t know what they don’t know about

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