PrinciPlEs of ElEcTrosurgEry
Contents
1. energy training Man PRINCIPLES OF ELECTROSURGERY OLYMPUS CONTENTS 2 1 2 2 2 3 3 1 3 2 3 3 3 4 4 1 Introduction 5 BASICS nn 7 Historical DACKGIOUNG isictcosaiedcdivsasenpeasenstedosiededes fi Principes Of elec raras 7 Effects of current ON TISSUE nennen 13 Principles of electrosurgerY o 15 COUNT AT A odas 15 Vaporniza tio SUMING sisi 16 FOO IZ AUON 1 IOOAO P0 ODUEP 17 Electrosurgical modalities 17 Electrosurgical modes and technologies 21 COAQUIa ton MOJES marrano ioa 21 4 2 4 2 1 4 3 O 5 1 ol Dela 5 1 3 5 1 4 0 2 21 22 9 2 3 6 Energy Training Manual Principles of Electrosurgery Basic 3 Cutting MONBS oooocccccccccccncnococcnncnonoconcnonicinonos 23 External parameters determining the cutting results ans 29 Output control technologies 26 Safety and hazards 29 SAN ne E ee 29 A 29 POOF Se GT re een este 29 PCIE CCCI OCS are 29 Neutra CISCO Saa 30 m EE E sie geen 32 OS E euere 32 Laparoscopic considerations 000 32 Unintended current flow 00sseenn nennen nenn 33 Further reading 35 OLYMPUS DAI This document is intended for training purposes on the European and Asian market only All pages are marked confidential which means that it is prohibited to pass this information on to2. 10 000 1 000 000 Hz Fig 8 Relationship of current frequency and neuromuscular stimulation 14 Energy Training Manual Principles of Electrosurgery Basic Basics Example A low current level can already cause a faradic effect at the household frequency of 50 60 Hz The amount of current I that is necessary to cause a faradic effect increases with increasing frequency f when starting at 100 Hz Note In some cases all HF units can cause neuromuscular stimulations even at high frequencies due to high current densities applied Thermal effect The electrolytic and the faradic effect can be significantly reduced by using alternating current with high frequencies of above approximately 100 200 kHz The lons move very rapidly but only short distances and therefore do not move across cell barriers Therefore there is almost no stimulation and no acid or corrosive burns see fig 9 The basic principle of electrosurgery is that heat is generated within the tissue when the current is flowing through the tissue resistance In other words it is not the metal electrode that heats up and determines Fig 9 No separation of positive and negative ions and therefore no electrolytic effect OLYMPUS the desired effect but it is the heat generation within the tissue caused by the current flow that results in the cutting or coagulation effect Every tissue type corresponds with a certain resistance which is higher than m
3. Electrosurgical devices are used daily in the surgical suite and assist the perioperative team to deliver safe and efficient patient care To ensure patient safety the principles of electrosurgical safety must be understood and all safety measured observed M Fig 35 Insulation failure Energy Training Manual Principles of Electrosurgery Basic 35 Further Reading FUR THER READING O AORN guidance statement Care of the perioperative patient with an implanted electronic device Recommended Practices and Guidelines 2005 Barlow DE Endoscopic applications of electrosurgery a review of basic principles Gastrointestinal Endoscopic 28 73 6 1982 Cotton PB Williams CB Colonoscopic Polypectomy Practical gastrointestinal endoscopy Blackwell Victoria 2008 Curtis LE High frequency currents in endoscopy a review of principles and precautions Gastrointestinal Endoscopic 20 9 15 1973 Czerny V ber Operationen mit dem Lichtbogen und Diathermie Dtsch Med Wochenschr Vol 35 No 11 489 493 1910 D Arsonval A Action physiologique des courants alternatifs C R Soc Biol Vol 43 283 286 1891 Doyen E Traitment local des cancers accessibles par l action de la chaleur au dessus de 55 C Rev Th r Med Chir Vol 77 551 577 1910 Doyen E Bipolaire Voltaisation M nch Med Wochenschr Vol 48 2516 ff 1908 Gildemeister M ber die im tierischen K rper bei elektrischer Durchstr mung entstandenen Gegenkr fte Pfl
4. is required to enable a spark ignition even via air gaps of a few millimeters and results in the formation of a spark rain This energy creates a superficial strongly carbonized coagulation zone By moving the active electrode large wound areas of tissue structures can be coagulated The resulting coagulum is only very superficial and the carbonized area might break open again and result in postoperative bleeding Argon Plasma Coagulation Another method to coagulate tissue without any contact of the electrode is to apply the HF current to the tissue via an ionized gas This technique is beneficial for positions where the Endol herapy instrument is difficult to handle and it is often used for preventively coagulating residual areas of cancerous tissue after resection for haemostasis or to prevent post operative bleedings Other benefits are the possibility to treat larger tissue areas superficially and coagulate areas that are difficult to reach by a side fire coagulation 4 2 CUTTING MODES Depending on the HF unit and the procedure there are different kinds of cutting modes available The cutting modes can be divided according to the wave form of the HF voltage into continuous blend and intermittent The clinical result of the cut is also dependant on external factors which will be described at the end of this chapter Energy Training Manual Principles of Electrosurgery Basic 23 Electrosurgical Modes and Te
5. metal tube Should the metal tube make contact to a small area of the bowel wall a burn could result see fig 33 Direct Coupling is the movement of electrons directly from one conductor to another This occurs when the surgeon touches the active electrode to a metal instrument or object in the field and accidently activates the HF unit Fig 33 Capacitive coupling The first electrode can then activate the other instrument and create an unintentional burn on the tissue it is touching see fig 34 In laparoscopic surgery never activate the electrosurgery unit unless the uninsulated part of the active electrode is in full view Insulation failures occur in monopolar electrosurgery and describe the breakdown of insulation along the shaft of an active electrode This failure allows the energy an opportunity to seek another pathway of lesser resistance In this case the current can either activate another metal instrument or inadvertently directly burn tissue see fig 35 Fig 34 Direct coupling Insummary all electrosurgical devices should be handled with respect The staff using these devices should be thoroughly trained If there is no automatic regulation of the output power available the suitable voltage power setting should be used to achieve the desired tissue effect Requests to increase the power setting should trigger the nurse to ensure that all cords are properly connected and the neutral electrode is properly applied
6. 01 V 10 V 7 kV 10 7 000 V 230 V 400 kV 230 400 000 V several MV several million V Electrosurgery Power transmission Lightning Power The energy converted per second by a current which flows through a resistance is called power in formula referred to as P and is measured in Watts W Power is a product of voltage and current Power dissipated by resistance produces heat Note The higher the power level the more heat is created in the tissue Energy Energy in formula referred to as E Q is a physical quantity and a property of objects and systems which is conserved by nature Energy is often defined as the capacity to do work Several different forms of energy such as kinetic movement thermal heat electromagnetic chemical and nuclear energy have been Energy Training Manual Principles of Electrosurgery Basic 9 Basics defined to explain all known natural phenomena The energy is measured in Joule J Energy can be converted from one type to the other e g chemical energy such as coal can be transformed into electrical energy by a power plant tissue can be heated by electrosurgical energy The electrical energy can be calculated by multiplying power by time Impedance Resistance Impedance in formula referred to as Z and resistance in formula referred to as R both represent oppositions to the flow of current but they are not the same Impedance Z is the sum of
7. 5 gives an example for high and low current density respectively A cross sectional area m 12 Energy Training Manual Principles of Electrosurgery Basic OLYMPUS _ Basics The following table summarizes the most important parameters in electrosurgery Parameter Symbol Unit Symbol Equitation Explanation Voltage U Volt V A voltage between two poles is generated by the separation of pos and neg charges Current l Ampere A number of electric charges electrons or ions per time 1 A 6 24 x 1018 electrons per sec Resistance R Ohm 9 i U Ohm s law R Resistance is the opposition to the flow of current Power P Watt W in electrosurgery product of voltage and current Energy E Q Joule J in electrosurgery product of power and time Heat Q Joule J Q E Joule s law Heat is thermal energy Frequency f Hertz Hz y 1 number of oscillations u per second Current density j A m l concentration of electrical current in the cross section of a conductor rn A cross sectional area Impedance Z Ohm Q 7 RiX oppositions to the flow of current 7 x reactance Temperature T Kelvin K Celsius C Fahrenheit F Important rules of electricity 1 Electrical current seeks ground 2 Electrical current needs a complete circuit to flow 3 Electrical current is lazy and prefers the path of least resistance CONFIDENTIAL Aa OS CURRENT ON TISSUE Depen
8. Basic 33 Safety and Hazards acoustic and visual signal if the value of the earth leakage current exceeds a certain level The signals make the physician aware that there is an increased risk of burns for the patient Note The Olympus HF units will not disable the activation of the HF unit immediately as the physician might be in the middle of a life saving procedure Another phenomenon of electricity is that high frequency alternating current can pass from a conductive material like an active electrode through an insulator e g the insulation of the electrode into another nearby conductive material e g biological tissue without the aid of wires or cables This can occur despite intact insulation surrounding the gt gt conductors and is called capacitive coupling h ESTE A sE DEENEN E EE A A A E a E a a a A A A Fig 32 In the ideal case the current that leaves the HF unit 11 should travel back to the HF unit via the neutral electrode 12 and 13 represent earth leakage currents 34 Energy Training Manual Principles of Electrosurgery Basic OLYMPUS _ Safety and Hazards Those capacitively coupled currents are often also called leakage or stray currents which occur mainly in monopolar electrosurgery Due to capacitive coupling the current can pass from the active electrode via air or insulating material to the metal tube e g trocar and onto any tissue in contact with the
9. always follows the way of lowest resistance Metal implants have a very low resistance and could thereby concentrate the current and increase the risk of endogenous burns see fig 30 Do not align the neutral electrode in relation to the treatment site so that the implant is positioned in between e Remove excessive hair from the neutral electrode site It lle may be necessary to shave the site for optimum contact e Place the neutral electrode as close to the surgical site as possible e Maintain complete contact with the patient s skin Gaps in the adhesion of the pad to the patient s skin could result in a burn as the entrapment of air acts as an insulator e Plug the neutral electrode into the appropriately labelled receptacle on the HF unit e Remove all metal jewellery from the patient e Avoid contact between two neutral electrodes when more than one HF unit is used e In bipolar electrosurgery gt gt Fig 30 Endogenous burns might result if a conductive implant is located i i i tral elect i no neutral electrode is needed between the surgical site and the neutral electrode 32 Energy Training Manual Principles of Electrosurgery Basic Safety and Hazards Recommendations Basically there are two types of neutral electrodes split or non split ones see fig 31 a b In order to minimize the risk of burns the use of split neutral electrodes is recommended because most HF units such as the Olympus ESG line i
10. perform the cutting procedure and they effectively concentrate the high frequency electric current onto specific points of the tissue The very high temperatures produced at those points at which the sparks contact the tissue result in a rapid conversion of the intracellular fluid into vapour That vapour produces a high pressure within the cell membrane resulting in the explosive burst of the cell see fig 12 The repetition of this effect around the electrode finally determines the incision Note Electrical current not surgical instruments make electrosurgical cuts It is important to distinguish the mechanical cutting from the electrosurgical cutting with HF current where the instrument is not in direct contact to the tissue The spark can not ignite if the tissue has direct contact to the electrode There is always a small distance between the Fig 13a Illustration of the cutting mechanism by spark generation electrode and the tissue and in between there is a layer of vapor allowing the spark to move along the electrode One important advantage of electrosurgery is the fact that every cut generates at the same time a certain extent of haemostasis as the produced heat is transported to the neighbouring cells which then coagulate As the electrode passes through the tissue sparks are produced wherever the distance between the electrode and the tissue is sufficiently small producing a cut see fig 13a b Fig 13b Cross s
11. sophisticated technologies are comparable to cars incorporating a cruise control This cruise control maintains the driving speed analogue tissue effect on a constant level analogue reproducible independently from external parameters such as incline of the street analogue increase of tissue resistance Voltage control Since the 80s an automatic voltage control has been implemented in order to allow the physician to achieve improved cutting results The voltage level is kept constant while the output current varies depending on the tissue resistance When for example the resistance of the tissue increases due to dehydration and the voltage is maintained on a constant level the electrical current also decreases and in total the level of output power is lower than without this feature Power and current control In order to optimize the clinical results and contribute to more safety for the user and the patient Olympus has implemented for its ESG HF unit portfolio additionally to the voltage control the control of power and current output By combining the limitations of these three parameters Olympus optimizes the control of the power output see black line in fig 27 during electrosurgical procedures OLYMPUS Spark control A highly sophisticated and effective way of automatic output control is the constant monitoring and control of the spark intensity The Olympus HF units ESG line incorporate a Fast
12. the beginning of the 20th century such cauterization was the method usually applied in the field of surgery In 1891 the French physicist and biologist d Arsonval reported on thermal effects induced in biological tissue by using alternating current at high frequencies without the stimulation of muscles or nerves so called Faradic effect In the year 1908 Nernst could verify that nerve and muscle stimulation decreases with increasing frequency Gildemeister stated in 1912 that above 200 KHz stimulation ceases to exist In the years 1911 and 1912 Czerny Werner and Caan published detailed descriptions of methods for the application of RF current to cut and coagulate tissue that are still used today Between 1907 and 1910 deep coagulation with RF current was developed as a method for tissue destruction particularly against cancer by Doyen Czerny and Nagelschmiat Doyen even used bipolar applicators Lee DeForest Energy Training Manual Principles of Electrosurgery Basic 7 Basics 2 patented the first electrosurgical device a high frequency spark gap generator in 1907 Harvey Cushing and William Bovie collaborated in the 1920s resulting in an update of these spark gap generators with sophisticated technology to increase the safety of electrosurgery Advances in radiofrequency and computer technology have continued to increase the safety of these devices and enabled the development of versatile bipolar dev
13. tissue in order to achieve the same effect as for muscle layers More sophisticated HF units can regulate their output according to the tissue properties see chapter 3 3 4 3 OUTPUT CONTROL TECHNOLOGIES In order to cut tissue the voltage has to be high enough to ignite a spark between the tissue and the electrode A minimum voltage of approximately 200 V is needed The spark intensity increases in proportion to the peak voltage Conventional HF units face the issue that the tissue results are not reproducible due to fluctuations of the output peak voltage U These fluctuations happen due to external parameters such as the distinct resistance of tissue structures the design of the electrode the cutting speed and the internal resistance level of the HF unit This can lead to irregular cutting and coagulation results including carbonized or not sufficiently coagulated areas even during one single cutting process As mentioned above a minimum of approximately 200 Volt peak U is necessary to start the cutting procedure by spark generation If the output voltage is lower than approx 200 V cutting is not possible If the output voltage is much higher than 200 Vo the spark intensity and therefore the thermal effect is very high and might result in an undesired carbonization In order to enable reproducible tissue effects independently from tissue characteristics today s HF units offer automatic output control measurements These
14. ALITIES The electrosurgical circuit consists of e HF unit e active electrode e patient tissue e neutral electrode e cables between HF unit and electrodes Basically there are two types of electrosurgical circuits The basic differences between monopolar and bipolar technology are the size and location of the return electrode Monopolar electrosurgery is the most common type Electric current passes from the small active electrode into the tissue through the patient and then exits the tissue at a large neutral electrode The amount of high frequency current which flows out of the HF unit through the active electrode is equivalent to the current flow from the neutral electrode back to the HF unit See fig 16 Electrical current travels in circuit and always prefers the way of lowest resistance The neutral electrode ensures that the current travelling to the tissue returns back to the HF unit without causing damage to tissues outside the surgical side OLYMPUS Let s take a look at current density in monopolar applications The active electrode has a small surface This results in a high current density and high thermal effect The current flows through the body to the neutral electrode where the current is spread over a larger area thereby reducing the current density and allowing the electrical current to return to the HF unit without causing tissue damage at the site of the neutral electrode The configuration of the ac
15. Electrosurgery Basic 21 Electrosurgical Modes and Technologies A TECHNOLOGIES 41 COAGULATION MODES The selection of the optimal coagulation mode is dependent on several external parameters such as the location and size of the bleeding the tissue properties and the design of the electrode While the focus during cutting procedures is on reproducible tissue effects by implementing automatic regulation measurements the focus for coagulation modes is to effectively stop the bleeding source with reproducible coagulation effects The physician can therefore select from different types of coagulation modes in combination with the optimal power level according to the requirements of the individual clinical case Suitable electrodes for contact coagulation are e g ball electrodes plate electrodes or the side faces of cutting electrodes The coagulation electrode should have a bigger surface than a cutting instrument Basically it can be differentiated between contact and non contact coagulation The most important coagulation modes with their characteristics will be described in the following Soft coagulation A soft coagulation mode represents a contact coagulation which means the electrode needs direct contact to the tissue It is recommended for Endolherapy instruments with a relatively large surface of the electrode such as the Coagrasper by Olympus please refer to respective treatment recommendations for more detailed infor
16. Spark Monitor FSM which represents an advanced Energy Training Manual Principles of Electrosurgery Basic 27 Electrosurgical Modes and Technologies the spark intensity on a constant level This makes the effect on the tissue reproducible Each mode has a preset spark intensity that is kept constant during the cutting procedure independently from the tissue characteristics and electrode design Another benefit of the FSM is a lower risk of carbonization due to the spark control By combining the technology that constantly monitors and reacts to changes spark control with the voltage power and current control of the tissue resistance and keeps the power output as low Olympus effectively contributes to the safety for users and as possible and as much as necessary in order to keep patients Ml P I bad P U Uan CONSTAN VOLTAGE CONSTANT CURRENT Fig 27 Example of a voltage power and current control of a cutting mode SAFE Y AND HAZARDS 51 SAFETY There are five areas of concern for safety when using electrosurgical devices These are the HF unit the power settings the cords the electrodes and the environment 511 HF UNIT The HF unit should be checked for any signs of damage If there is any question about the integrity of the HF unit it should be checked by a technician prior to use HF units should be plugged directly into a wall outlet and not into a portable multiple outlet or extension co
17. any external party The comparison to competition has been written to the best of our Knowledge at the date of publication Even if the names of the competitive products mentioned in this manual show no indication of a registered trademark their trade names are not in the public domain Please keep in mind that our competitors enhance their products as well so their products might have changed in the mean time Make sure you use competitor comparisons only carefully in your conversations with customers This training material does not constitute medical or legal advice and should not be relied upon as such This document should not be considered as a substitute for carefully reading all applicable labelling including the Instructions for Use IFU supplied with the devices and published peer reviewed articles concerning the topics presented Before using or selling any product please thoroughly review the relevant user manual s for instructions warnings and cautions Energy Training Manual Principles of Electrosurgery Basic INTRODUCTION Electrosurgical units ESU were first introduced during the early twentieth century and have become an increasingly important component of most of today s surgical and also endoscopic procedures where cutting of tissue or haemostasis is required The physician has a wide portfolio of electrosurgical equipment to choose from and more and more sophisticated technologies contribute to more safety for users an
18. at all and the frequency is O Low frequency is defined as less than 100 000 cycles 100 kHz in one second The physical effects of low frequency electricity can vary and may include pain muscle and nerve stimulations and even cardiac arrest As the human body is less sensitive to current with high frequencies electrosurgical generators use frequencies Fig 3 Frequency of alternating current OLYMPUS between 300 kHz 300 000 cycles sec and 4 MHz 4 000 000 cycles sec and they are called High Frequency HF units In the Anglo Saxon world high frequency HF is often called radiofrequency RF because radio transmitters also operate in this frequency range The frequency f can be calculated according to the formula Example What is the frequency when one period T takes 10 ms Circuit All electrical current has to complete a circuit The current is extracted from ground at the power plant and distributed to outlets The current is then delivered to the patient at the Fig 4 Circuit of electricity surgical site and then returns to the HF unit and back to ground and power plant see fig 4 In order to perform electrosurgery a voltage U source is applied across the tissue which causes an electric current I to flow The voltage source and tissue form a simple electrical circuit with the tissue acting as a resistor R The formula simply demonstrates that the resistance of the tissu
19. cedure High current density Fig 28a Correct application of the neutral electrode with full contact to the skin Fig 28b Wrong application as the neutral electrode has no full skin contact The small contact point of the neutral electrode causes a high current density and corresponds with the risk for endogenous burns Energy Training Manual Principles of Electrosurgery Basic 31 Safety and Hazards e Make sure that the neutral electrode is in full contact with the skin see fig 28 Overlapping of the electrode must be avoided e Always select a new and unopened disposable adhesive neutral electrode appropriate for the patient s size and weight e Never use a neutral electrode that has been left open and never cut it to custom fit a patient e Pad placement is key to avoid burns There must be adequate tissue blood perfusion to promote electrical conductivity and to dissipate heat For traditional adhesive pads the ideal placement is on a clean dry Fig 29a Correct application of the neutral elec trode to the patient with large muscle mass Other sites may increase resistance Ong site to the treatment site to current flow thereby increasing the risk of burns e Place the neutral electrode with the long side to the treatment side see fig 29 Otherwise the current density might increase and enhance the risk for endogenous burns e Avoid proximity to metal prostheses Remember that electrical current
20. chnologies Continuous cutting modes A continuous cutting mode is characterized by a pure sine wave The peak voltage U of a continuous cut mode determines the spark intensity and the coagulation depth achieved during the cut The spark intensity increases proportional to the peak voltage and determines the thermal effect The higher the peak voltage U the higher the spark intensity and the higher the thermal effect deeper coagulation margin E g in figure 22 the spark intensity increases from the left to the right side corresponding with a higher voltage level gt gt and deeper coagulation Fig 22 Voltage level and spark intensity increases from left to right A spark ignites above approx 200 V 24 Energy Training Manual Principles of Electrosurgery Basic Electrosurgical Modes and Technologies Blend modes Some HF units offer a so called blend mode The term blend means that the voltage signals are modulated The sine wave is not regular compared to a continuous mode A blend mode can consist of sine waves with different phases and amplitudes or even include a pause without any current flow The modulation happens within microseconds us e g 50 us are the same as 0 00005 seconds The crest factor is a value that indicates the coagulation depth of an electrosurgical incision The higher the crest factor the higher the thermal effect and coagulation depth The crest factor is define
21. d as peak voltage U divided by rms voltage U me The general intention of modulation is to increase the thermal effect by increasing the crest factor c All three signals in but differently distributed In the third example 3 the crest factor figure 23 represent the same average voltage U is bigger than in example 1 and 2 The pause without any current flow between the packages of sine waves is bigger than in example 2 or 1 but the peak voltage U is higher A higher voltage level corresponds with a higher spark intensity higher thermal effect and deeper coagulation margin The thermal effect increases with increasing crest factor Intermittent cutting modes For some applications an additional haemostasis period is beneficial e g during polypectomies or dissection of OLYMPUS Fig 23 The left waveform 1 represents a continuous cut mode The middle 2 and right waveform 3 are modulated Urms root means square value of the voltage Fig 24 Example for an intermittent cut Olympus ESG 100 PulseCut HPCS stands for High Power Cut Support vascular tissue For those cases an intermittent cut such as the PulseCut see fig 24 of the Olympus ESG 100 offers a good compromise of cutting and coagulation by combining a cut phase 11 followed by a coagulation phase T2 within one mode The intermittent cut offers also the benefit of an enhanced control over the cutting procedu
22. d patients Nevertheless an understanding of the basic principles of electrosurgery is essential in order to achieve the best possible clinical result for each individual case This guide aims to give the medical personnel a better understanding for the principles of electrosurgery M 1 Our general term nowadays for a generator or ESU is HF unit You will find that term in the following Introduction BASICS 21 HISTORICAL BACKGROUND There have been many reports of using hot oils and hot irons as crude methods of haemostasis often with devastating results Egyptian pioneers recognized as early as 3000 B C that a bleeding can be stopped by applying heat The history of the develooment of radiofrequency surgery even reaches back to Hippocrates a Greek physician of antiquity who used a red hot iron to arrest the flow of blood haemostasis during amputations around 400 BC In the middle of the 19th century the so called Paquelin burner was developed as a thermocauter instrument for thermocautery and the so called galvanic cauter as an electrocauter The first of these consisted of a metal pin heated to over 1000 C by a fuel air mixture and used for the destruction of tumourous tissue The electrocauter on the other hand made it possible to separate or slough off biological tissue by means of a knife or platinum sling raised to red heat by direct current Prior to the introduction of high frequency technology at
23. ding on the characteristics of electrical current three different effects can occur Electrolytic effect Direct current DC generates in addition to the desired thermal effect also an undesirable electrolytic effect due to spatial separation of positive and negative ions see fig 7 producing acids and bases at the electrode poles and resulting in corrosive acid burns Therefore direct current is not suitable for electrosurgical procedures Faradic effect Alternating current with low frequencies which are normally used in every household 50 60 Hz is not suitable for electrosurgical procedures because in addition to the desired thermal effect these frequencies can produce undesirable physical effects such as pain muscle and nerve stimulations and even cardiac arrest The stimulation of muscles and nerves is also called faradic effect or neuromuscular stimulation NMS As the human body is less sensitive to current with high frequencies electrosurgical HF units usually use frequencies above 300 000 cycles sec 300 kHz Figure 8 shows the current strengths that are necessary to cause neuromuscular stimulation in dependence on frequency gt gt Energy Training Manual Principles of Electrosurgery Basic 13 Basics Fig 6 Three tissue effects caused by current flow The desired tissue effect is the thermal effect Fig 7 Spatial separation of positive and negative ions causes corrosive acid burns je
24. e determines the current flow This relationship is known as Ohm s Law It is one of the most fundamental laws in the field of electronic and electric engineering and demonstrates the relation between voltage current and resistance Joule s Law Current flowing through a resistor causes the conversion of electrical energy into heat Q The converted energy is measured in Joule J In electrosurgery this heat is generated in the tissue itself In other words the resistance of the tissue converts the electrical energy of the voltage source into heat thermal energy which causes the temperature T of the tissue to rise Joule s law generated heat converted electrical energy Q E Energy Training Manual Principles of Electrosurgery Basic 11 Basics Example with 4 A A dem J 4 Alco and J 4 Alco Fig 5 Low vs high current density Current Density Current density in formula referred to as is the concentration of electrical current in the cross section of a conductor and is measured in A m The current density depends on the size and shape of the electrode The active electrode of the EndoTherapy instrument has a very small surface compared to the neutral electrode see chapter 2 4 with a large surface A small area results in high current densities and produces the tissue effect at the surgical site Bigger areas such as the neutral electrode correspond with a low current density Figure
25. ection of an electrosurgical cut Energy Training Manual Principles of Electrosurgery Basic 17 Principles of Electrosurgery 3 3 CARBONIZATION Carbonization is the result of further heating of dehydrated desiccated tissue The solid contents of the tissue are reduced to carbon Figure 14 illustrates the relation between the temperatures and the tissue effects l en Fig 14 Undesired carbonization effect This effect is undesired because a significant charring of the tissue surface corresponds with reduced wound healing Summary ofthermal tissue effects in dependence on temperature up to approx 40 C no significant cell damage above approx 40 C reversible and irreversible cell damage depending on the duration of exposure Fig 15 Mechanism of thermal effect to biological tissue using HF current above approx 50 C irreversible cell damage start of protein denaturation above approx 60 0 C coagulation Smaller bleedings can be stopped above approx 100 C vaporization cutting phase transition from liquid to vapor of the intra and extra cellular fluid The complete dehydration of tissue is sometimes also called desiccation above approx 200 C carbonization latin carbo coal reduced wound healing due to significant charring of the tissue surface gt gt 18 Energy Training Manual Principles of Electrosurgery Basic Principles of Electrosurgery 3 4 ELECTROSURGICAL MOD
26. er tissue Ez Es and ETE OLYMPUS coagulation is required it is essential to avoid an early dehydration by using lower output power settings see fig 21 lower Although the coagulation will take longer the total amount of energy provided to the tissue is higher with lower power settings than with higher settings after t2 E3 gt El Forced coagulation Compared to a soft coagulation the forced coagulation is employed when a quick and superficial desiccation of the tissue is required using electrodes with a relatively small surface Voltages with peak values up to 2 kV create sparks with a high intensity and high thermal effect in order to achieve a quick coagulation result Due to the spark ignition the possibility of undesired carbonization remains Fig 21 The total amount of applied energy depends on the power level P and duration t of the application and are illustrated as blue and green squares E1 E3 Note An early dehydration results that no further current can be applied to deeper tissue layers The yellow coagulation margins demonstrate the clinical results in dependence of the power level and the duration of the application OLYMPUS Spray coagulation This coagulation mode represents a technique of contactless coagulation and has long been known under the name fulguration The active electrode is held several millimeters above the surface of the tissue very high voltage several thousand volts
27. etal The tissue resistance is mainly determined by the water content of the cells In fat tissue the water content is very low Fat itself cannot conduct electrical current very well since it contains little electrolytic liquid needed for conduction The resistance of fat is approximately 10 times higher than that of blood see table below Specific resistance of biological tissue unit Q cm Muscle 160 250 Blood 160 300 Liver 200 380 Brain 670 700 Fat 1 600 3 300 Skin 11 000 Specific resistance of metal unit Q cm Copper 0 0000017 Silver 0 0000016 E Fig 10 Summary of the effects of current to the tissue CONFIDENTIAL PRINCIPLES OF Energy Training Manual Principles of Electrosurgery Basic 15 Principles of Electrosurgery 3 ELEC TROSURGERY Electrosurgery is defined as the application of HF current to modify or destroy tissue cells or to dissect or remove tissue in combination with mechanical surgical techniques How does radiofrequency current affect tissue Electrosurgery uses radiofrequency current to cut tissue and seal bleeding vessels by producing heat The heat produced either vaporizes the intracellular fluid and denatures proteins or explodes the cell membrane at the site of the active electrode The effect of the radiofrequency current on tissue also depends on the current density in a particular area The effectiveness varies based upon four tissue characteristics e thickness e va
28. gers Archiv Vol 149 389 400 1912 Heymann E Chirurgische Eingriffe mit Hochfrequenz str men Med Klin Vol 15 539 545 1930 Huschak G Steen M Kaisers UX Principles and risks of electrosurgery Anasthesiol Intensivmed Notfallmed Schmerztherapie Jan 44 1 10 3 2009 H D Reidenbach Hochfrequenztechnik und Laser in der Medizin Springer Verlag Berlin 1983 Laine L Bipolar Multipolar electrocoagulation Gastrointestinal Endoscopic 36 538 41 1990 Luciano AA Soderstrom RM Martin DC Essential principles of electrosurgery in operative laparoscopy J Am Assoc Gynecol Laparosc May 1 3 189 95 1994 Massarweh NN Cosgriff N Slakey DP Electrosurgery history principles and current and future uses Journal of the American college of Surgeons Mar 202 3 520 30 2006 Morris ML Electrosurgery in the gastroenterology suite principles practice and safety Gastroenterology Nursing Mar Apr 29 2 126 32 2006 Nagelschmidt F Uber Hochfrequenzstr me Fulgu ration und Transthermie Z Phys Diat Ther Vol 3 1909 Nernst W Zur Theorie des elektrischen Reizes Pfl gers Archiv Vol 122 275 315 1908 Swerdlow DB Salvati EP Rubin RJ Labow SB Electrosurgery Principles and use Diseases Colon Rectum Jul Aug 17 4 482 6 1974 Vilos G How to Do Electrosurgery Safely Outpatient Surgery Magazine July 2000 www olympus com OL Mil U www olympus owi com W7 070 290 1 2_12 09 Printed in Germany
29. ices Electrocautery is defined as the use of direct electric current to heat an instrument that is used to coagulate and seal tissue It should not be confused with electrosurgery which uses alternating current at radiofrequency levels to directly heat the tissue instead 2 2 PRINCIPLES OF ELECTRICITY For a better understanding of electrosurgical effects on biological tissue this chapter will provide an overview on elementary aspects of electricity Electricity is based on electrons protons and neutrons which together create atoms Atoms which have the same number of protons as electrons are neutrally charged see fig 1a Atoms with more protons than electrons have a positive charge and are called positive ions Atoms with more electrons than protons have a negative charge and are called negative ions see fig 1b gt gt 8 Energy Training Manual Principles of Electrosurgery Basic OLYMPUS paces Electric current When charged particles electrons ons flow through a conductor e g metal air gaps tissue an electric current in formula referred to as is formed In other words Electric current is the rate at which electrons or ions flow along a conductive pathway and is measured in Ampere A The value describes the number of electric charges electrons or ions per time 1 A 6 24 10 electrons per second Examples Electronics integrated circuits 1nA 10 mA 0 000000001 0 01 A E
30. lectrosurgery 10 mA 10 A 0 01 10 A Power transmission 100 A 100 kA 100 100 000 A Lightning 200 kA 200 000 A Note Current through metal is a flow of electrons Current through liquids is a flow of ions Biological tissue consists of a greater or lesser extent of electrolytic liquid ions and can conduct electrical current The effects of electric current on biological tissue are described in chapter 1 3 There are two types of electric current e Direct Current DC where the electricity flows in one direction only See fig 2a Batteries for example supply direct current e Alternating Current AC where the flow direction of the electrons or polarity changes continuously Fig 1b Positive and negative ions see fig 2b A wall socket supplies alternating current Alternating current flows in cycles and is bidirectional The usual waveform of AC is a sine wave For electrosurgery only alternating current is used see chapter 1 3 Fig 2a Direct current DC Fig 2b Alternating current AC Voltage The Voltage in formula referred to as U is the force which is needed to push the electrons or ions through an electric conductor such as tissue and is measured in Volts V One volt moves 1 ampere of current through 1 ohm of resistance see below A voltage between two poles is generated by the separation of positive and negative charges Examples Electronics integrated circuits 0 1 uV 10 mV 0 0000001 0
31. lectrosurgery check the alignment of the electrodes e f electrosurgery is being used in a liquid environment such as urologic procedures or hysteroscopy it is important to use the correct kind of solution Monopolar applications require the use of non conductive fluids such as water sorbitol glycine or mannitol Bipolar applications require the use of conductive fluids such as saline 91 3 ACTIVE ELECTRODES Safety measures regarding monopolar and bipolar active electrodes include e Inspect the active electrode for damage before use Including the insulation cord and hand piece functionality e Plug the active electrode into the appropriate receptacle on the HF unit Never force a connector into a HF unit This is a clue that the instrument is not meant to be used with that HF unit e Activate the electrode only when ready to use e Always place the active electrode into an insulated holster when not in use If the active electrode tip is removable be sure it is securely attached to the hand piece e f the active electrode should fall off the sterile field and down the side of the OR table disconnect it immediately to prevent accidental activation or related risks gt gt 30 Energy Training Manual Principles of Electrosurgery Basic Safety and Hazards e Frequently clean the active electrode to prevent eschar build up on the active electrode tip and accessories e Donot activate the electrode if flammable vapours s
32. mation A soft coagulation mode is required for larger and deeper tissue coagulation and is available in monopolar or bipolar technique A benefit of the soft coagulation is the low sticking of instruments and low risk of carbonization In order to localize the bleeding source an irrigation pump such as the Olympus AFU 100 can be very helpful By slowly heating up the tissue the bleeding can be stopped by shrinkage and clotting In order to avoid unintended cutting or carbonization this mode has a voltage limitation U lt 200V accordingly adapting to the tissue properties gt gt 22 Energy Training Manual Principles of Electrosurgery Basic Electrosurgical Modes and Technologies What impact do different output power limits have to the effect on the tissue A higher output power level provides in general more energy to the tissue than a lower output level In figure 21 the area El represents the amount of energy applied to the tissue after a certain period of time t1 with at a higher power level and E2 represents the amount of energy at a lower power level El is larger than E2 after the same period of time However a higher output power level corresponds also with the risk of an early dehydration of the tissue surrounding the electrode Early dehydration means also a significant increase in the resistance of the superficial tissue layer with the result that no electric current can be transported to deeper layers When deep
33. ncorporate an additional safety feature in combination with split neutral electrodes The Contact Quality Monitor CQM of the ESG 100 constantly monitors the contact quality of the split neutral electrode to the tissue If the contact quality decreases to a risky level the HF unit will give an acoustic feedback and disable the activation in order to avoid any burns 9 2 HAZARDS 9 21 SMOKE The heat produced by an HF unit results in the formation of bioaerosols which are composed of gases and particles matter from patient tissue both vital and dead Particles varying in size from 0 1 to 5 0 um microns may include both viruses and bacteria The noxious gas produced carries many chemicals some of which may have either OLYMPUS mutagenic or carcinogenic potential The NIOSH released a study in 1998 regarding the effects of smoke on OR personnel This included nausea headache myalgia upper respiratory infections and eye and skin irritation High filtration pumps for smoke evacuation are commercially available to filter the hazardous chemicals from the plume that is the result of lasers or electrosurgery In addition the use of a high filtration mask is recommended to reduce the exposure 0 2 2 LAPAROSCOPIC CONSIDERATIONS Laparoscopic surgery requires particular considerations for electrosurgery Surgery is performed in a moist environment with limited access and visibility Electrosurgical tools are frequently used due t
34. o their versatility reasonable costs and overall ease of use An awareness of the hazards and an understanding of the mechanisms of injury can enable the medical personnel to facilitate safe tissue dissection and effective haemostasis Bipolar devices are becoming more popular due to safety concerns with monopolar devices 2 National Institute for Occupational Safety and Health Fig 31a Split neutral electrode O Fig 31b Non split neutral electrode OLYMPUS 9 2 3 UNINTENDED CURRENT FLOW High frequency alternating current always corresponds with a certain level of leakage currents Leakage currents represent current flows which travel another pathway than initially intended In the ideal case the current that leaves the HF unit should travel back via the neutral electrode to the HF unit see fig 32 I1 But a certain percentage of the current could alternatively travel via the patient and the operating table see fig 32 12 or the surgeon see fig 32 18 and then via the ground back to the HF unit These alternative current flows are also called earth leakage currents and correspond with the risk of thermal tissue damages Sophisticated HF units such as the Olympus ESG line constantly monitor earth leakage currents and give an mas rs ll MI A A E mn ME SE EEE ee ee n L E i j i i i i p i i i i I E 7 rt f FE Energy Training Manual Principles of Electrosurgery
35. rd The power cord should be checked to make sure it is not frayed or damaged Any other accessories that are attached to the HF unit should also be checked The instructions for use will provide specific information on what to check and how frequently Never put heavy objects or containers on top of a HF unit Fluids and electricity are a dangerous combination 91 2 POWER SET TING The power setting of the electrosurgical unit should be determined by the physician There are some devices that are pre programmed and will automatically set to the default values when a particular instrument is recognized by the HF unit The power settings if not already automatically set should be adjusted to the tissue type and the size and shape of the active electrode If the surgeon repeatedly requests that the power output of the HF unit e g Gyrus ACMI G400 should be increased check the following items in both bipolar and monopolar electrosurgery e Ensure that all cords are connected properly to allow the circuit to be completed Energy Training Manual Principles of Electrosurgery Basic 29 Safety and Hazards O e In monopolar electrosurgery check the adequacy of contact between the dispersive return electrode and the patient e Evaluate the power setting and increase the power in small increments e Clean the active electrode to remove eschar If problems persist consider replacing the accessories and or the HF unit e n bipolar e
36. re as the cutting phase is interrupted and not continuously CONFIDENTIAL Cut support technology In order to enable an immediate start of the cutting procedure some HF units offer a cut support named High Power Cut Support HPCS see fig 24 by applying a very high amount of power until a spark is ignited for a very short time lt 50ms This high power peak has the effect of rapidly drying out the tissue around the electrode thereby enabling an immediate spark ignition The cutting procedure can start right away by reducing the risk of an undesired thermal damage to the tissue The risk of a mechanical cut can be minimized at the same time 4 21 EXTERNAL PARA METERS DETERMINING THE CUTTING RESULTS The thermal effect of the cutting procedure also depends on external parameters which are the duration of electrode contact to the tissue the design and condition of the electrode and the tissue properties see below In order to deliver a high amount of energy into the tissue time is needed remember Energy E Power P time t The slower the cutting speed is or the longer the cutting electrode remains on the tissue the more electrical energy is transformed into heat per unit of length When a higher thermal effect is required the electrode should be moved slowly because more energy can be applied to the tissue which results in a deeper heat penetration and denaturated margin see example 1 of fig 25 If
37. scularity e fat content e liquid content In any type of electrosurgery eschar formation and build up may decrease the tissue effect due to poor heat diffusion The following chapters describe the three main effects caused by electrosurgery e coagulation e vaporization cutting e carbonization 31 COAGULATION Temperatures of 60 70 C in the area around the active electrode heat the cells gradually up until their intracellular fluid can escape through holes in the cellular membrane which are a result of protein denaturation and thereby result in the shrinkage of the cell see fig 11 Thus the haemostatic effect is attained by the denaturation of proteins that leads to the shrinkage of the vessels diameter and the clotting of blood This efficient form of haemostasis is commonly used to stop bleedings in both open and endoscopic surgery and represents an effective alternative to clipping or forms of ligations for smaller gt gt vessels Fig 11 Mechanism of the coagulation effect on a cell 16 Energy Training Manual Principles of Electrosurgery Basic __ OLYMPUS __ Principles of Electrosurgery 3 2 VAPORIZATION CUT TING When the voltage between the cutting electrode and the tissue to be cut is sufficiently high approx 200 Vo sparks electric arcs are generated between the cutting electrode l Fig 12 Mechanism of the cutting effect on a cell and the tissue These sparks are essential to
38. the electrode is moved more quickly see fig 25 example 2 3 then the same amount of energy is spread over a longer incision length than in example 1 The coagulation depth denaturated margin of example 3 is smaller than in the examples 1 2 Energy Training Manual Principles of Electrosurgery Basic 25 Electrosurgical Modes and Technologies Note The thermal effect decreases with increasing cutting speed Duration cutting speed The depth of the coagulation margin depends on the cutting speed bird s eye view see fig 25 Fig 25 Three different incision lengths after the same period of time Electrode design With most HF units the thermal effect to the tissue is bigger with a larger diameter of the electrode Larger electrodes correspond with a higher current flow and result therefore in a higher energy penetration and coagulation depth than smaller electrodes for constant cutting speed Fig 26 The depth of the coagulation margin depends on the design and condition of the electrode a 26 Energy Training Manual Principles of Electrosurgery Basic Electrosurgical Modes and Technologies Note The thermal effect increases with increasing surface of the electrode Tissue properties The thermal effect is also dependant on the tissue properties For example fatty tissue has a relatively high resistance compared to muscle tissue that is very vascular Thus a higher voltage is required for fatty
39. tive electrode and the application technique will determine the actual tissue result see fig 17 HF unit mep as io ee A Fig 16 Monopolar electrosurgery Fig 17 The current density at the surgical site around the active electrode is much higher than with the neutral electrode Energy Training Manual Principles of Electrosurgery Basic 19 Principles of Electrosurgery Bipolar electrosurgery differs from monopolar surgery in that the tissue effect takes place between two electrodes that are part of the same device see fig 18 Electric current passes directly from one electrode through the tissue and then returns via the opposing electrode and back to the electrosurgical HF unit Current does not pass large parts of the patient s body only through the tissue between both electrodes and therefore no neutral electrode is required see fig 19 20 The bipolar technique is safer than the monopolar because e The current exposition to the patient is limited e The risk of burns caused by the neutral electrode is non existent e The risk of leakage currents is reduced see chapter 4 2 3 I Fig 19 Bipolar circuit No neutral electrode is required as the return electrode is part of the surgical device Fig 20 A common bipolar instrument is a bipolar forceps which is used for the closure of blood vessels OLYMPUS ELEC I ROSURGICAL MODES AND Energy Training Manual Principles of
40. two quantities called resistance R and reactance X Z R X The resistance resistive part real part of impedance can dissipate power and hence produce heat The resistance for electrons as they attempt to move through tissue is measured in Ohm 2 Not all kinds of materials convert electrical energy into heat the same way Conductors have a low impedance to the flow of electrons and include for example copper saline blood and muscle This is why the neutral electrode or patient plate return electrode etc should be placed over a large muscle mass during monopolar electrosurgical applications Insulators have a high resistance to the flow of electrons and include air gt gt rubber plastic fat water and glycine 10 Energy Training Manual Principles of Electrosurgery Basic Basics Reactance is determined by the inductive and capacitive behavior of the electrical set up such as condition and position of cables Note The higher the water content of biological tissue the lower is its resistance Frequency Frequency is the number of times an alternating current reverses from minus to plus in one second and is measured in Hertz Hz see fig 3 In Europe frequencies with 50 Hz and in the USA 60 Hz are used in household power supplies and may cause cardiac defibrillation due to electric shock To give an example Batteries are powered by direct current supply only that means that the polarity does not change
41. uch as those from disinfection solution are present e Do not reuse single use electrodes Additional safety measures e Do not attempt to connect a bipolar instrument to a monopolar HF unit e As with all electrosurgical instruments turn off the power when not in use do not place them on flammable materials such as drapes or gauze The monopolar electrosurgical HF unit may start alarming after repositioning the patient Switch the HF unit into the standby mode and check the following items e Are all cables secured e In monopolar electrosurgery check that the neutral electrode has good contact with the skin Repositioning when using only bipolar devices is usually not a problem since there is no neutral electrode used OLYMPUS Interference with electronic implants Electronic implants like automatic cardioverter amp defibrillator pacemakers chochlear implants are being used more and more frequently The electrical energy of electrosurgical procedures can interfere with some of these devices It is always best to check the IFU of the implant or contact the manufacturer of the implant prior to using an electrosurgical device 0 1 4 NEUTRAL ELEC I RODES Neutral electrodes have many safety considerations Wrong application or malfunction of the neutral electrodes are the main causes for endogenous skin burns burns created within the tissue e Thoroughly assess the skin integrity before and after the pro
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