Electrosurgery

Chapter 16 Electrosurgery



Brenda C. Ulmer, MN, RN, CNOR


The use of electrosurgery generators (ESUs) have become commonplace throughout the world wherever surgical and invasive procedures are performed. The caustic “cautery” and “clamp, cut, and tie,” which was the gold standard for hemostasis for centuries, has been transformed by today’s surgeons to electrosurgery coagulation, vaporization, and vessel fusion.



HISTORICAL BACKGROUND


Papyrus documents from Egypt dated about 3000 bc are among the earliest records of surgery and the use of cauterization to control bleeding. Further examples of cautery use can be found in early manuscripts throughout the Middle Ages. Many researchers and physicians contributed to the body of knowledge of electrosurgery throughout the past two centuries.


In the 1800s researchers around the world were independently conducting experiments with electricity. In both England and America Michael Faraday (1791–1867) and Joseph Henry (1797–1878) were conducting experiments on the relationship between magnetism and electricity. They discovered that a moving magnet could induce an electrical current in a conductive wire. Electromagnetism was a very important principle that led to improved electromedical devices (Goldwyn, 1979).


The research conducted in the years between 1881 and 1900 saw electrical current moved into the higher-frequency ranges. In 1881 William J. Morton reported that current in the 100-kHz range did not produce the painful tissue effects of current in the lower-frequency ranges. By 1891 Arsenne d’Arsonval of France had documented that the alternating current frequency could safely be lowered to 100 kHz (Pearce, 1986).


An early use of electrosurgery clinically was by Joseph A. Riviere. While treating a musician with electricity for insomnia, Riviere accidentally touched one of the wires on a device he was using and produced a spark. This incident prompted Riviere to use the spark on an ulcer on the musician’s hand. Repeated treatments resulted in healing of the ulcer. Riviere reported his results at the First International Congress of Medical Electrology and Radiology in Paris in 1900. This is said to be the first surgical use of high-frequency current to treat a human condition (Kelly and Ward, 1932).


The first patent for an electrosurgical high-frequency generator was filed by Lee DeForest on February 10, 1907. The DeForest electrosurgery unit was not the device that came into general use in operating rooms. That distinction goes to the man whose name has become synonymous with electrosurgery—William T. Bovie—and his work with Harvey Cushing, MD. They are the two men whose names are most closely associated with electrosurgery. The Bovie and Cushing partnership yielded successful contributions to the field of electrosurgery that have stood the test of time.


Bovie’s interest in electrosurgery came about because of his work with radium at the Harvard Cancer Commission. He believed that the cautery effect achieved from radium emanation could be achieved more easily with electrocoagulation. Bovie’s work with high-frequency generators continued, and his machine developed into one that was better suited for the operating room.


The advances Cushing made in surgical care and specifically neurosurgery are legendary. He was one of the first proponents of blood pressure monitoring during surgery and used primarily local anesthesia. There were also great advances made in controlling blood loss during surgery through the methods that Cushing used. There were, however, still patients that were considered inoperable due to the concern of uncontrolled bleeding. Cushing’s first true consideration of the use of electrosurgery seems to have occurred at a medical conference in the summer of 1925. Samuel Harvey and John Morton, both residents of Cushing’s, were watching an electrosurgery demonstration when Cushing joined them. One of them jokingly suggested that Cushing use the machine on the brain. Instead of discounting the possibility, Cushing stopped and looked thoughtfully at the demonstration (Voorhees et al, 2005). Cushing later visited Bovie’s laboratory at Harvard to inquire further about his electrical machine.


By the fall of 1926 Cushing had arranged to use Bovie’s device during a surgical procedure. Over the next two years the two worked together to use and make refinements to the electrosurgical generator. Cushing’s adoption of the use of electrosurgery changed the landscape of surgery throughout the world. Both Cushing and Bovie gave credit to the work done by other researchers in the field of electrosurgery, but it is the work that the two of them accomplished together that contributed to the advancement of Bovie’s device. The combination of Cushing’s skill as a surgeon and Bovie’s genius made the difference. They worked with Liebel-Flarsheim to develop a commercial unit, which also contributed to the success of the “Bovie.” The continued refinement and evolution of electrosurgery devices did not end with Bovie and Cushing, but have continued throughout the twentieth and twenty-first centuries. Electrosurgery is one of the most common devices used in surgical and invasive procedures around the world.



ELECTROSURGERY



Basic Principles of Electricity


Electricity is the power behind radio-frequency electrosurgery generators; therefore it is useful to understand how electricity works. Electricity is a naturally occurring phenomenon arising from the existence of atoms. Atoms consist of negatively charged electrons, positively charged protons, and neutral particles called neutrons. Atoms that contain equal numbers of electrons and protons are charge neutral. Movement of electrons can change the charge of the atom. Atoms that lose electrons and gain protons have a positive electrical charge; atoms that gain electrons and lose protons have a negative electrical charge. During atom movement, like charges repel and unlike charges attract. Electron movement is termed electricity, and it can move at nearly the speed of light. The following two constant properties of electricity can have an impact on patient care in the operating room:



1. Electricity always follows the path of least resistance.


2. Electricity always seeks to return to ground (Columbia Encyclopedia, 2001).


Electrical current—electricity—is produced as electrons flow through a conductor. The pathway of the electrical current as it flows through the conductor is called the electrical circuit. There must be a complete circuit before the device will function. The two types of electrical current in use today are direct current (DC) and alternating current (AC). Direct current is a simple circuit, and the electricity flows in only one direction. All types of batteries employ a simple DC circuit. Energy flows from one terminal on the battery and returns to the other terminal to complete the circuit.


AC changes, or alternates, direction of the electrical flow. The frequency of these alterations is measured in cycles per second or Hertz (Hz), with 1 Hz being equal to one cycle per second. Household current alternates at 60 cycles per second, as does much of the electrical equipment used in operating rooms. Alternating current at 60 Hz can cause tissue injury. As early researchers discovered, neuromuscular stimulation ceases at about 100,000 Hz as the alternating current moves into the radio-frequency range. Electrosurgery generators take 60-cycle household current and raise it to the radio-frequency range of 200,000 Hz to 3.3 MHz (Figure 16-1). As electrons flow through a conductor, that flow is measured in amperes, or amps (Hutchisson et al, 1998).


image

Figure 16-1 Electrosurgery frequency spectrum.


(Courtesy Covidien, Inc.)


Additional factors that affect current flow and electrosurgery generator performance include resistance, voltage, and power.


Resistance is the opposition to the flow of the electrical current. Resistance or impedance is measured in ohms. In the operating room one source of resistance or impedance is the patient. All patient tissues have different ohms of resistance—muscle and blood have the lowest resistance and easily allow for the flow of electrons.


Voltage is the force that will cause 1 amp to flow through 1 ohm of resistance. It is measured in volts. The voltage in an electrosurgical generator provides the force that pushes electrons through the circuit. Electrosurgery generator voltages can range from about 2000 to as much as 10,000 volts of electricity, depending on the type of generator and how the generator is used.


Power is the energy produced. The energy is measured in watts. A watt is the amount of energy produced by 1 volt times 1 amp of current. Electrosurgical generator power settings are either printed on a light-emitting diode (LED) screen in watts, or a percentage of the wattage is demonstrated on a numerical dial setting. Most electrosurgical generators have a maximum coagulation output of 120 watts, and a maximum vaporization or cut output of 300 watts.


Current flow through a completed circuit, impedance/resistance, and voltage are all components that must be present for the electrosurgical generator to function. Knowing the role that each one plays during use of the generator will help to ensure safe use of the electrosurgery generator.



Electrosurgery Waveforms


One of the important discoveries during the early development of the electrosurgery generator was that the electrical output from the generators could be manipulated to produce different waveforms, or electrosurgical modes. There are three basic waveforms that have distinct tissue effects. The modes or waveforms are cut, fulguration, and blend (Figure 16-2).


image

Figure 16-2 Typical electrosurgery waveforms.


(Courtesy Covidien, Inc.)



Vaporization (Cutting)


The cutting current produced by an electrosurgical generator is a continuous waveform. Because the delivery of current is continuous, much lower voltages are required to achieve tissue vaporization. To produce a cutting effect the active electrode tip is held just over the tissue. The current vaporizes cell walls and divides the tissue. The cut mode can also be used for coagulation of tissue through desiccation. In this application the active electrode is in direct contact with tissue.

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Aug 5, 2016 | Posted by in ANESTHESIA | Comments Off on Electrosurgery

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