Megadyne-Principles of Electrosurgery
Megadyne-Principles of Electrosurgery
Megadyne-Principles of Electrosurgery
Principles of Electrosurgery 1
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Table of Contents
Introduction Principles of Electricity Electrocautery is not Electrosurgery Electrosurgery: Techniques of Delivery Electrosurgical Waveforms Tissue Heating Tissue Responses Generators Active Electrodes Active Electrode Tips PTFE Coated Active Electrode Tips Specialty Active Electrode Tips Disposable Patient Return Electrodes Pressure Sores Reusable Patient Return Electrodes Considerations in Endoscopic Electrosurgery Surgical Smoke Summary
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introduction Having an understanding of the principles of electricity is a strong foundation for best practices in electrosurgical patient care. Electrosurgery units and accessories facilitate the passage of high frequency, oscillating electric currents through tissue between two electrodes to fulgurate, desiccate or cut tissue. Although the scientic application of electricity and the technologies have come a long way in regards to development and safety, hazards still exist for the surgical patient and OR team. It is imperative that all surgical team members know the principles involved, the technology at hand and the safety practices necessary for optimal usage of electrosurgery.
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Principles of Electricity
Principles of Electricity Electrons orbit atoms and with energy move out from one atom to another to produce an electrical current. Understanding the science and principles of electricity is an important step to using the technology properly and eliminating potential hazards possibly encountered during patient application of electrosurgery.
Principles of Electricity
In surgery, the generator converts the electricity to high frequency waveforms and creates the voltage for ow of current. 60 cycle current is increased to over 300,000 cycles per second by the generator.
Current:
The number of electrons moving past a given point per second, measured in amperes (A). The path along which electricity ows. The force that pushes electric current through resistance; electromotive force or potential difference expressed in volts. The energy produced over a period of time. The lack of conductivity or the opposition to the ow of electric current, measured in ohms. The ability of an electrical circuit to transfer an electrical charge from one conductor to another, even when separated by an insulator.
Circuit: Voltage:
Power: Resistance:
Capacitance:
Why over 300,000 cycles per second? 60 cycles per second creates nerve stimulation and electrocution. High radio frequency eliminates nerve and muscle stimulation and electrocution.
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Principles of Electricity
Current Density Current density refers to the intensity of the current as it passes through the tissue. When current is concentrated, heat is produced and the amount of heat produced determines the tissue response. The smaller the application area, the greater the current density at the application site.
Electrosurgical Waveforms
Electrosurgical Waveforms Electrosurgical generators can produce a variety of waveforms and each waveform creates different tissue results.
Cut
Blend
Coagulation
The density of current is high at the delivery point of the active electrode. The density of current is low at the dispersive point of the patient return pad.
The cutting current will cut the tissue but provides little hemostasis. The coagulation current provides coagulation but does not allow for smooth cutting. The blend current is an intermediate current between the cutting and coagulation currents but is not a combination of the two as the name might imply. It is a cutting current in which the duty cycle (time current is actually owing) is reduced from 100 percent of the time to approximately 50 percent of the time (depends on manufacturer). The off time allows the tissue to cool creating some hemostasis. It is important to know that the Blend currents in ESUs are delivered only when the cut button/footswitch is activated. Depressing the coag button/footswitch will deliver the coag or spray coag current.
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Techniques of Delivery
Electrosurgery: Techniques of Delivery There are two basic types of electrical circuits: monopolar and bipolar. (monoterminal) is an electrosurgical technique in which the tissue effect takes place at a single active electrode and is dispersed (circuit completed) by a patient return electrode.
MONOPOLAR BIPOLAR
Techniques of Delivery
(biterminal) is an electrosurgical technique in which the electrosurgical effect takes place between paired electrodes placed across the tissue to be treated. No patient return electrode is needed. Typically bipolar forceps are utilized for this technique. The distance between the active and return electrodes in a bipolar circuit is very small since both electrodes are adjacent to each other. The distance the current ows is limited and is contained in the vicinity of the two electrodes. As current passes through the tissue from one electrode to the other, the tissue is desiccated and the resistance increases. As resistance increases current ow decreases. The LEDs on the Mega Power electrosurgical generator indicate current ow when bipolar instruments are used.
Generator Active Tine Patient Tissue
Return Tine
It is important to remember that the dispersive electrode is just as capable of producing injury as the active electrode unless the patient return pad has large contact over conductive tissue to provide a low current density; or incorporates technology to maintain patient safety. Pad safety technologies will be discussed in later sections.
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Tissue Heating
As electrical current enters tissue, the ions within the cells become excited and begin to go into motion releasing kinetic energy. As this action increases or is prolonged, the cells begin to heat. The temperature rise in tissue is directly proportional to: the resistance of the tissue the current density the power output the time of current application. If a substance is an excellent conductor it will allow easy passage of current and offer very little resistance; therefore, the heat generated will be very little. The resistance to current ow in living tissues is inversely proportional to the water content. The more water present the greater current ow through that tissue because of the lower resistance. Therefore, current ow is greatest in tissues of high water content, such as blood, and least in those of low water content, such as bone. Electrical current ows preferentially through blood, then nerve, then muscle, then adipose tissue and nally bone.
Direct hot wire burn to tissue. Current does not transfer through the patient.
Electrosurgery: the electrical current heats the tissue. The current must pass through the tissue to produce the desired effect. Alternating current ows through the patient. Current enters the body at a high density and leaves the body at a low density.
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Tissue Responses
Tissue Responses Given the versatility of waveforms available with modern generators, surgeons have the opportunity to create a multitude of tissue responses and results.
Electrosurgical Generators
Electrosurgical Generators There are two types of electrosurgical generators: Ground referenced generators (typically older, outdated units) Isolated generators (todays state-of-art technology) Many of the modern isolated generators also have return electrode contact quality monitoring (RECQM) systems that measure the impedance between the patients skin and the return pad. Ground Reference Generators The current passes through the patient and returns to the generator, which is linked to ground. The problem is the current can go to any grounded object other than the pad (ECG electrodes, OR bed, metal objects) and cause alternate site burns. If the dispersive pad is forgotten, or is not in contact with the patient, a ground referenced generator will still send current to and through the active electrode and into the patient. If the patient is grounded by any other means, the current goes wherever it nds a path, this may again result in patient burns at alternate sites if current densities are high. Ground referenced generators are considered to be outdated technology but are occasionally found in some operating rooms.
Bovie Electrosurgical Generator Historic Alternate Burn Sites
is direct energy application that slowly drives water out of the cells creating a drying out of the cells. The blood vessels are thrombosed. Desiccation can be achieved with either the cutting or the coagulation current by contact of the electrosurgical device with the tissue.
DESICCATION
a form of coagulation, is the arcing or sparking of energy above the tissue to create a surface charring. When the spark reaches the tissue, it has a very high current density thus the tissue effect is supercial. Fulguration requires a high enough voltage to produce sparks with a coagulation effect rather than cutting.
FULGURATION,
waveforms vaporize the cellular uid causing cellular explosions, which result in a scalpel like dissection. True electrosurgical cutting is a non-contact activity in which the electrosurgical pencil is a short distance from the tissue.
CUTTING
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Electrosurgical Generators
Isolated GeneratorsAlternate burn sites essentially eliminated Patient Return Pads
Safety
Warnings: highly visible and audible. Labels: clear & legible. Contact: patient & pad contact quality monitoring. Power: accurate
Reliability
Warranty: available. Loaner Service: replacement loaner service for repairs. Experience: long term focus on electrosurgery
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Although sticky adhesive patient return pads rarely cause pressure ulcers, the adhesives can contribute to skin problems that break down further during a patients recovery period.
Two cords allow for one pad with two generators
Using a reusable, large patient return electrode containing viscoelastic polymer ll serves multiple critical functions. The primary function is the dispersement of electrosurgical energy and in addition, the polymer prevents pressure points, friction and shearing.
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YES
YES
YES
YES YES
YES YES
NO NO
NO
NO
YES
YES NO NO
Friction can occur when the patients skin is pulled or rubbed over a stationary object. Shearing occurs when the patients skin is xed while the underlying tissue shifts or is moved without support to the skeletal system. Direct pressure or weight applied over time to specic areas causes an ischemic reaction in deep tissue. Damage occurs as the bone pushes against the muscle and ischemia extends outwardly to the soft tissue layers of the dermis. The tissue is deprived of blood and oxygen and eventually necrosis will result. Pressure can also result in nerve damage.
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Active Electrodes
Active Electrodes The active electrode delivers the RF current from the generator to the surgical site.
Active Electrodes
Reusable Steam Sterilizable E-Z Pen with counting mechanism and E-Z Clean Active Electrodes
The pencil handpieces can be controlled directly by pushing the desired button or by activating the foot pedal. The yellow switch will turn on the cut or blend mode selected on the generator while the blue switch will deliver the coag mode selected. Pencil pieces can be purchased as disposable or reusable. Cost conscious surgical managers report that the reusable pencils are more economical per procedure.
The electrosurgical pencil should be used in a manner that minimizes the risk of injury to the surgical patient. Patient injury may result from unintentional activation, incomplete circuitry and incompatibility of the generator and the active electrode. Inspect each pencil prior to use. To minimize the risk of inadvertent activation place the electrode in a safety holster when not in immediate use.
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Active Electrodes
Active Electrode Tips The current to tissue action at the tip of the active electrode is high electron ow over a small area. As resistance is encountered heat is produced. The current density is high but differs for each tip based on the size and shape of the tip.
Active Electrodes
Coated Active Electrode TipsE-Z Clean Polytetrauoroethylene (PTFE) coating on stainless steel tips makes them eschar-resistant and easy to clean during surgical applications.
Stainless Steel
Needle tip active electrodes require a lower power setting than blade or ball electrodes because the current is concentrated on a very small area at the tip of the electrode. Active electrode tips manufactured from stainless steel have the disadvantage of eschar build up which results in increased resistance. This resistance interferes with the desired tissue effect and can become a re hazard. These tips have to be cleaned frequently with a scratch pad. Scratching off the eschar roughens the surface of the electrode, which promotes the build up of more eschar. This action adds time and hassle to the procedure.
Benets of PTFE Coating Resists eschar Easily cleaned Non-stick properties Resistant to high temperatures Bendable Cutting edge performance More durable than silicone Decreased thermal necrosis Silicone has been used to coat active electrode tips but has not been as successful because of intolerance to high temperatures. PTFE is a slippery polymer surface that allows for high degrees of heat while preventing molecular adherence and thus slides through tissue without build up. PTFE creates such a strong bond that it can be found in the Guinness Book of World Records as the most slippery material available.
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Active Electrodes
Specialty Active Electrode Tips Large Loop Excision of the Transformation Zoneelectrodes come in a variety of sizes for precise exicisions. Active Electrode Hazard
Active Electrodes
Right
Wrong
Lletz Loop Electrodes Provide a precise specimen by using a high current density.
Bayonet needle tips allow the surgeon improved visibility past the pencil to the operative site. Blunt needle tips have the benet of a needle-type current concentration without the risk of vessel or nerve puncture injuries.
Do not modify active electrodes. On occasion, nurses and surgeons have altered the active electrodes and unknowingly put their patients at risk. For example, do not use red rubber catheters over the tip of the electrode to minimize the chance of secondary burns to tissue. This practice increases the risk of a re hazard and is not recommended. Sparks and leakage can and will occur at the juncture of the catheter and the insulation on the tip. The high temperature of the electrosurgical active electrode can melt the red rubber catheter. The practice of modifying frequently takes place and is often because the appropriate tip is not available. Also, there is a perception that the use of a red rubber catheter saves money when in fact using a red rubber catheter costs more than purchasing the fully insulated tip. The attempt at saving a few pennies is not worth the risk of increasing the re potential. Be sure to have the right tip and improve the safety by being sure that the tip is PTFE coated to minimize sparking and charring.
Mega Fine Needle Electrodes Extremely sharp needles create very high current densities. These high current densities allow the surgeon to use lower power settings which minimize thermal damage to tissue. The Mega Fine needles can be used at power settings below 10 watts and are typically used by plastic and ENT surgeons.
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Active Electrodes
Considerations during monopolar endoscopic electrosurgery Three unique problems related to monopolar electrosurgery use during endoscopic procedures are direct coupling, insulation failure and capacitive coupling. Direct coupling Direct coupling occurs when the active electrode touches another metal instrument. The electrical current ows from one to the other and then proceeds to tissue resulting in unintended burn. This can also occur if an active electrode is activated while in contact with a metal clip. The prevention of this occurrence is with the surgeon who is in control of the instrumentation. The best way surgeons can avoid this problem is to refrain from activating the active electrode until the intended tissue is in the eld of vision and the electrode is in direct contact with the tissue and NOT in contact with any other metal object. Insulation failure
Active Electrodes
Insulation failure can occur when the insulation covering of an endoscopic instrument has been damaged. Cracks or breaks in the shafts insulation allow the electrical energy to escape and burn unintended tissue. The insulation of endoscopic instruments must be inspected before, during and after each use. Most damage to insulation occurs during instrument processing, specically during sterilization. Heat with subsequent cooling causes insulation to shrink and then expand. During this process cracks and breaks can occur. Insulation failure will result in instantaneous, irreversible death to tissue because of the high density current at the point of exit from the shaft insulation break.
The Megadyne resposable and reusable Indicator Shaft is an innovative design with a dual insulation layer. The underlying surface is yellow, which allows for immediate identication of cracks and breakage. When the yellow is visualized, the shaft needs to be replaced.
The Megadyne Indicator Shaft clearly shows when insulation damage has occured and replacement is required. 28 Principles of Electrosurgery Principles of Electrosurgery 29
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Active Electrodes
Capacitive coupling Capacitive coupling is a natural occurrence that can happen when energy is transferred through intact insulation to conductive materials. The current leaks from a conductor through insulation to another conductor.
Active Electrodes
Surgical Smoke Surgical smoke is generated when the uid within the tissue cells heats to the point of coagulum or vaporization. Smoke from tissue, no matter the heating source, is noxious and harmful to anyone who inhales the contents. Various researchers have identied carcinogenic, toxic, mutagenic and poisonous contents. The smoke can also contain and transmit bacteria and viruses. The safest means of eliminating the hazards contained within surgical smoke is to use a high efciency ltration smoke evacuation system. Capturing the smoke requires that the wand be placed as close as possible to the origin of the smoke with sufcient ow to remove the smoke from the eld. Mega Vac provides excellent smoke capturing by utilizing a patented nose cone that creates a Venturi tornado effect resulting in a high velocity ow rate.
AORN recommends that equipment should be designed to minimize the risk of capacitive coupling injuries during minimally invasive procedures. The best way to eliminate this potential hazard is to avoid the use of hybrid (plastic and metal) instruments or trocars. Endoscopic trocar cannula systems should meet safety criteria established for the practice setting. When an allmetal system is used, capacitive current is safely dispersed through the greater surface area provided by the chest or abdominal wall, thereby reducing current concentration. Metal cannula systems are best for the port of electrosurgical instruments. An all-plastic system is another alternative. The lowest power setting minimizes the potential for capacitive coupling. Use the lower voltage setting such as Cut, or Coag rather than Spray Coag.
AORN and OSHA recommend that surgical smoke exposure should be avoided.
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Summary
Summary Regardless of the frequent use and familiarity of surgical team members with electrosurgery units and devices, safety issues and operational concerns continue to exist. Megadyne is committed to quality products and concentrates on patient safety through product design and surgical team member education. Our dedicated representatives are willing to provide inservice device training as well as professional continuing education on safety and science related to the application of electrosurgery. We are committed to best practices in electrosurgery.
About Megadyne
MEGADYNE MEDICAL PRODUCTS, INC. CORPORATE PROFILE
Established: 1985 Headquartered: 11506 South State Street Draper, Utah, 84020 Customers: More than 4,000 hospitals, surgical centers, healthcare providers, distributors and kit packers worldwide Ownership: Privately Owned URL: www.megadyne.com
Megadyne is the recognized authority in electrosurgery. The electrosurgical products company was founded in 1985 with the launch of the E-Z Clean line of non-stick, eschar-resistant, PTFE-coated electrodes. Co-founders Dr. G. Marsden Blanch, an ENT surgeon; Gary R. Kehl an entrepreneur and visionary; and Matthias R. Sansom, an experienced medical device executive, established Megadyne to facilitate the research and development of high quality, cost effective medical products for surgeons and nurses. Today, Gary Kehl serves as the Companys Chief Executive Ofcer, Matt Sansom as President and Chief Operations Ofcer. Dr. Blanch remains involved in Megadynes product research and development serving as the Companys chairman of the board and medical director.
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About Megadyne
After more than two decades of innovation, Megadynes research and development team has continued to develop and bring to market innovative electrosurgical devices and accessories for the changing needs of healthcare professionals. To help ensure high standards of training, Megadyne provides grant funds to support continuing nurse and surgeon education through independent study courses. Megadyne maintains a certied Quality System that is substantially compliant with ISO 9001, EN 46001, ISO 13485, the EU Medical Device Directive 93/42/ EEC, Canadian Medical Device Requirements, and 21 CFR part 820. E-Z Clean Products: E-Z Clean non-stick electrodes feature a patented and proprietary polytetrauoroethylene (PTFE) coating that reduces eschar build-up during surgical procedures, enabling surgeons to use lower power settings. Lower power settings mean less thermal necrosis to surrounding tissue and a further reduction in eschar build-up; E-Z Pen Electrosurgical Pencil is lightweight and ergonomic. The 12-time use E-Z Pen has a built-in count down mechanism which displays the number of uses left and the lock-out failsafe function prevents additional use once the lifespan has expired; MEGAne Line of extra sharp, precision needles designed for clean, fast, safe electrosurgery. Congurations include 2-inch and 2.5-inch long needle electrodes, with 45 and 90-degree angled styles, and a 6-inch extended version;
About Megadyne
Disposable Laparoscopic Electrodes provide a new fully insulated instrument for each case, minimizing the risk of stray current and unwanted burns. Featuring E-Z Clean, they require no reprocessing and come in varying congurations of tip styles, and include either foot or pencil control; Resposable Laparoscopic Electrode includes disposable MegaTips with E-Z Clean coating to minimize eschar build-up, rendering surgical procedures cleaner, faster and safer. It also features the patented Indicator Shaft technology with two layers of insulation to minimize the risk of burn due to stray current from damaged insulation. The patented yellow inner Indicator layer shows through when the black outer layer is nicked or worn away to alert clinicians to discard and replace the electrode; Reusable Stainless Steel Laparoscopic Electrodes also feature Indicator Shaft technology and come in varying congurations. Each instrument provides excellent dissection and coagulation for a variety of laparoscopic applications; and; All-In-One Hand Control, which provides nger controlled on/off cutting and coagulation, suction and irrigation for laparoscopic procedures. In addition to the E-Z Clean Products, Megadyne offers: The Mega Power Electrosurgical Generator is designed for its simple elegance. The Mega Power features large, easy to read displays and is driven by Constant Control Technology that automatically monitors tissue impedance and adjusts power to reduce tissue damage and drag. The result is a smooth, clean, accurate cutting and coagulation effect at the lowest possible settings for maximum patient safety;
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About Megadyne
Mega Soft Line includes safe, reusable patient return electrodes that are easy to use and provide cost savings for the hospital. The Mega Soft incorporates this innovative technology with an OR table pressure reduction pad providing added patient protection against pressure sores; The Mega Soft Dual Cord provides clinicians with the ability to attach two separate generators to a single patient return electrode, eliminating the hassle of looking for, and prepping, two sites to place sticky return electrodes; and Mega Vac Smoke Evacuation System to protect surgeons, nurses, patients and other O.R. staff from breathing hazardous electrosurgical smoke. The Mega Vac creates effective suction with less noise during electrosurgical procedures and enables the surgeon to easily capture smoke while comfortably performing surgery. Pencils and Accessories: LEEP/LLEETZ loop electrodes Electrosurgical cables Disposable electrosurgical pencils PRODUCTS: Megadynes products have been proven in thousands of operating rooms worldwide. Its agship E-Z Clean line of non-stick electrosurgical tips and electrodes come in a variety of sizes, shapes and congurations that can be easily wiped clean with a sterile sponge. USERS: Megadynes Mega Soft technology has been used in millions of electrosurgical procedures worldwide and its active electrodes are used by hospitals in millions of procedures each year. In addition to hospitals and surgical centers, its customers include healthcare group purchasing organizations and supply companies in most regions of the world. Glossary
Active Electrode An
Glossary
electrosurgical instrument or accessory that concentrates the electric (therapeutic) current at the surgical site. Electrosurgery where current ows between two electrodes that are positioned around tissue to create a surgical effect (usually desiccation). Current passes from one electrode, through the desired tissue, to another electrode, thus completing the circuit without entering any other part of the patients body.
Bipolar Electrosurgery
The condition that occurs when electrical current is transferred from one conductor (the active electrode), through insulating materials, into adjacent conductive materials.
Capacitive Coupling Circuit
The path along which electricity ows. Weight-bearing portion of the Mega Soft Reusable
Patient Return Electrode The number of electrons moving past a given point per second, measured in amperes (A).
Current
The electrosurgical effect that results from high current density in the tissue causing cellular uid to burst into steam and disrupt the structure. Voltage is low and current ow is high.
Cutting
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Glossary
The condition that occurs when one electrical conductor (the active electrode) comes into direct contact with another secondary conductor (scopes, graspers). Electrical current will ow from the rst conductor into the secondary one and energize it.
Direct Coupling Resistance
Glossary
The lack of conductivity or the opposition to the ow of electric current, measured in ohms. A system that actively monitors tissue impedance (resistance) at the contact between the patients body and the patient return electrode and interrupts the power if the quality of the contact is compromised.
Return Electrode Contact Quality Monitoring
The passage of high frequency electrical current through tissue to create a desired clinical effect.
Electrosurgery
Using electrical arcs (sparks) to coagulate tissue. The sparks jump from the electrode across an air gap to the tissue.
Fulguration
The force that pushes electric current through resistance; electromotive force or potential difference expressed in volts.
Voltage
The condition that occurs when the insulation barrier around an electrical conductor is breached. As a result, current will travel outside the intended circuit.
Insulation Failure
A surgical procedure in which only the active electrode is in the surgical wound; electrosurgery that directs current through the patients body and requires the use of a patient return electrode.
Monopolar Electrosurgery
A plate or pad (dispersive electrode) that recovers the therapeutic current from the patient during electrosurgery and returns it to the electrosurgical generator.
Patient Return Electrode
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