Electrosurgery demands OR vigilance Russell Church, RN William T Hamlin
Russell Church, R N , is codirector of the Urological Physician’s Assistant Program, University of Minnesota, General College, and Veterans Administration Hospital, Minneapolis. He is past president of the American Urological Association Allied Division. He received a BS i n nursing from the University of Minnesota. William T Hamlin is medical products manager for Ritter Company. He has a B S M E from the University o f Rochester.
lthough electrosurgery has been known in this country for 50 years, the most rapid changes in its use have occurred in the past five years. New types of electrosurgical units have appeared in the OR and other electrical devices are being attached to the patient. OR personnel should understand what electrosurgical equipment does, how the results are achieved, and why precautions are necessary. Recent trends in legislation, medical education, and patient-care standards emphasize the need for personnel to be well informed. OR personnel are directly concerned with the electrosurgical unit in several ways including the legal responsibility for its proper function. The proper attachment of equipment to the patient is critical. They must be familiar with the controls on the equipment so that the surgeon’s instructions can be carried out quickly and smoothly. They must know what situations are hazardous or contraindicated and what variables are important for the patient’s safety. Urology is a most demanding service in the use of electrosurgery; therefore, some special details are to considered. The first use of intense heat in surgery was a red-hot iron applied to a wound or stump to stop bleeding. A later change involved heating the iron by passing a n electrical current through it, the modality known as electrocautery today. The distinction between electrocautery and electrosurgery is that in electrocautery heat is transferred to the tissue from a preheated object. In electrosurgery, the heat is generated in the tissue by passage of high frequency electrical current. In simple terms, electricity is a force produced by rotating a loop of wire
AORN Journal, Deceniber 1975. Vol22. N o 6
903
lectrosurgical cutting is accomplished by cellular heating and cellular disintegration.
E
through a magnetic field. Electrons are caused to move in this manner, and properly drawn off of the wire loop, produce electrical current. If the wire loop is rotated 60 times each second, the frequency of the generated electricity is 60 cycles per second (60 cps), the standard frequency of electricity we use in homes. Depending upon how the electrons are drawn off of the wire loop, direct current (DC) can be produced where the electron force moves in one direction only. If the electrons ebb and flow, that is, frequently reverse direction, alternating current (AC) is produced. Sixty cycles every second is referred to as low frequency current. Frequencies can range from 100,000 to 3,000,000 times per second. These are the radio frequency (RF) or high frequency currents. When electricity is applied to the body, tissue fluids act as an electrical conductor because of the electrolytes they contain. The low frequency alternating current tends to move the cellular ions to and fro, polarizing the cell. This causes a neuromuscular activity which can range from a tingling sensation to a painful contraction. It can be fatal if it interferes with the electrical conductivity of the heart. When electrical frequencies reach 20,000 or 50,000 cycles per second, the cellular ions cannot totally react so rapidly, and no electrical conduction is
904
discernable. However, the cellular ions are in rapid, though limited motion. They collide frequently and release energy in the form of heat. This is the basis of the cellular destruction caused by the electrosurgical unit. In other words, cutting is accomplished by cellular heating-instantaneous vaporization of cellular water-and cellular disintegration. The first work in this field was done around the turn of the century by Tesla, D’Arsonval, and Riviere. Later, DeForest built the first vacuum tube generator, which was well accepted and used in Paris and Vienna. This vacuum tube generator was not suited to controlling bleeding. In the late 1920s, Harvey Cushing and Dr W T Bovie worked with George H Liebel and Edwin S Flarsheim in the development of a spark-gap electrosurgical unit. The first Bovie electrosurgical unit provided a cutting current which could cut cleanly and provided variable amounts of hemostasis to seal bleeders and capillaries. Combinations of vacuum tube cutting current generators with spark-gap cutting and coagulation units continue to be manufactured and are used in many hospitals today. Around 1970, a new method of generating electrosurgical currents was developed with a variety of solid state units. These units produce essentially the same RF current, but
AORN Journal, December 1975, Vol22, No 6
use transistors, diodes, and rectifiers instead of spark-gaps or tubes to generate the current. The greatest difference between solid s t a t e and spark-gap/tube units (other than unit size) seems to be in coagulation. Either type will cut readily, but the solid state units provide a “pin-point” coagulation rather than a ‘‘spray” coagulation. This is not always acceptable where large bleeding areas are
Fig 1. A low concentration of high frequency current produces a gentle, deep tissue warming. This penetrating heat is beneficial in the treatment of joint pain of rheumatoid arthritis and muscular pains.
encountered such as in open heart surgery and in some transurethral procedures. The basic principle of electrosurgery is that when electrical current flows through a resistance, heat is produced. Common examples of this phenomenon are the electrical soldering iron and the electric blanket. It is apparent that when energy is concentrated in a small area as in the tip of the soldering iron, very high temperatures result. The same amount of energy spread over a large area, as in an electric blanket, gives a much lower rise in temperature. Medical diathermy this principle with two to produce large heat for pain relief and an imrease in circulation in the treated area (Fig 1). Surgical diathermy or electrosurgery reduces the size of one of the electrodes
to the point where intense current concentration causes destruction of tissue or a cutting or coagulation effect a t the smaller electrode (Fig 2). The distinction between cutting and coagulating is achieved basically by varying the amount of dampening or interruption of the current. The undamped current of a tube generator or solid state generator will cut freely and smoothly, but will have little hemostatic effect. Damping the current increases the hemostatic effect. Solid state units have not been able to duplicate completely the coagulation effects possible with the spark-gap type generators. Some surgeons are willing to modify the technique and feel that the advantages of the solid state units outweigh this requirement with greater precision in pinpointing bleeders. Others feel that there is no substitute for the spark-gap generator current in cases where massive coagulation is required. The effects of electrosurgery depend upon the flow of high frequency electrical current through the patient’s tissues. The current enters the body a t the active electrode and returns to the electrosurgical unit through the dis-
Fig 2. When a high concentration of R f current is applied to tissues, mechanical disruption produces a cutting effect. Since it is the same principle as diathermy, improper amlication moduces deeD. Dainful burns. I
,
AORN Journal, December 1975, Vol22, N o 6
-
1
,
905
Correct Flow
j&
Fig 3. A variety of dispersion devices are available today.
persive (inactive or ground) plate. At the dispersive plate, maximum area or electrical contact or both is required to achieve minimum heating effect. In this country, the dispersive plate can vary from the stainless steel plate supplied by the manufacturers of electrosurgical units to a variety of disposable dispersive electrodes. Saline pads and lead plates, still reported in Europe, are not presently in use in any United States hospital. Whatever dispersive plate is used with the electrosurgical unit, it should ensure a sufficient area of contact with the patient to avoid any temperature rise at this point (Fig 3). The National Fire Protection Association recommends a minimum of one square centimeter per one and one-half watts of power output from the electrosurgical unit.’ This works out t o approximately 27 square inches for the average fullsized hospital operating room electrosurgical unit. If the stainless steel plate is used, it should be completely clean and free of nonconductive soilage. Conductive gels and lubricants Fig 4. As more devices are connected to the patient, problems of interaction become more numerous.
906
should be nondrying so that they remain conductive over the period of long operations. It is best to use a conductive gel designed specifically for electrosurgery. Do not rely on some similar material which may be intended for electrocardiographs (ECG) o r other electroappraisals. Another reason why a dispersive plate and a conductive lubricant are required is that many other pieces of electrical equipment may be attached to the patient and alternate “grounds” may be provided (Fig 4). Any increase of resistance at the dispersive plate will tend to cause current to flow through these alternate paths. Unwanted current concentrations can and will cause patient burns. It is necessary to be sure that the dispersive electrode is not applied to hairy surfaces which tend to insulate or to bony protuberances which tend to concentrate electrical current. It is always best to keep the dispersive plate as close to the active site as possible to cut down the total current path. The current path should not include a
Incorrect Flow INACT IVE ELECTRODE
GROUND
Fig 5. Discontinuity in the grounding system may be external as illustrated, and, in rare instances, internal to the electrosurgical system. If current flow to alternate sites is substantial, radio-frequency burns may result.
GROUND
pacemaker or similar device, since some models of pacemakers may be deactivated by high frequency currents. A critical factor is the assurance that the connection between the dispersive plate and the electrosurgical unit is complete. A number of circuits and devices have been developed and are used either singly or in combination with other units. The earliest circuit for this purpose was the “circuit sentry’’ that relied on a signal being sent out from the machine to the dispersive plate and back to the machine. If either wire were broken, the unit was deactivated and a n alarm sounded. This circuit sentry could sometimes be fooled by some of the grounds from other patient connected devices (Fig 5 ) . Other electrosurgical units use the isolated output system. Theoretically, a n isolated output has no ground connection, and the RF current will not flow to other grounds. If the dispersive plate is grounded accidentally, however, the output is like any other grounded system, and the unit may be activated. There is also a patient sentry system which involves a monitoring current through the active lead and the pa-
tient back to the dispersive plate and its current. It is most helpful to know which system your particular electrosurgical unit has, and to know how it can be checked out. It should be checked each day. In the ideal world of the laboratory, it would be possible to place the patient on a wooden table with no other electrical equipment attached to him and have the electrosurgical unit work safely and effectively 10070 of the time. In the real world of the operating room where the patient is on a conductive table and there are conductive floors, the high frequency current will tend to ground through a variety of paths: the ECG electrodes, the surgeon’s gloves (and occasionally his eyebrow), and conductive anesthesia equipment. The use of a n approved dispersive electrode, properly applied, offers the lowest resistance path. This will reduce the possibility of undesired current concentrations at unexpected points and subsequent patient burns. For the use of electrosurgery in urology, the following suggestions will help reduce problems. Combination spark-gap and tube electrosurgery units should have the selector switch left in some other position than No 1 Tube
AORN Journal, December 1975, V o l 2 2 , No 6
907
Cutting unless that modality is being used. This keeps the filaments from being turned on and lengthens the life of the tubes. be checked 0 Spark-gaps should periodically and may be cleaned with an abrasive strip when they first start growing peaks and valleys on the gap facings. Gaps require replacement a t periodic intervals depending upon use. 0 Cutting loops should be checked to be sure that the insulation is complete. The proximal end of the loop must be inserted as far as it will go into the resectoscope block before securing it. If this is not done, the current will arc and burn the block, which ruins the block and the operation. 0 Loops should be checked to be sure that they have not been bent accidently or intentionally. This seriously shortens the life of the loop, and intentional reshaping of the loop accomplishes little. One manufacturer suggests that a cutting loop should be used only once and discarded. 0 Conductive lubricants must never be used on the sheath of a resectoscope, and nonconductive solutions must be used as an irrigating media during transurethral resecting procedures. There have been cases where the irrigating solution was changed during the course of the operation. The introduction of a “hard’ or saline solution causes dispersion of power and complete loss of cutting ability. 0 Sheaths are sometimes charred if faulty coordination allows the unit to remain activated after the loop completes its excursion through the tissue. This is aggravated by needlessly high power settings and slow cuts. The use of
908
too high a power setting and too slow a cut also can overcoagulate the tissue and build up a cumulative wall of coagulum which becomes increasingly difficult to cut with each excursion of the loop. In each case, the surgeon should use the unit a t the lowest setting which will accomplish the desired results. Any demand for an increase in power should warrant a check of the active electrode and cord as well as the dispersive plate and its grounding cord to be sure that these items have not become accidentally disconnected or faulty. 0 When using the solid state electrosurgical unit to coagulate, it is essential that the loop contact the exact point of the bleeder. Sparkgap units tend to provide a spraytype coagulation that can be used to cover a broader area. Another area of hazard with electrosurgery is that any electrosurgical unit is capable of producing a spark a t the active electrode. For this reason, it should not be used in the presence of flammable anesthetics. Flammable skin preparations should be avoided or allowed to dry thoroughly since there have been occasions where these have been ignited. A less obvious hazard is the flammable gases present in the colon. If electrosurgery is to be used in that area, a nitrogen or carbon dioxide atmosphere should be provided. A preventive maintenance program, including cords and accessories, by hospital staff or manufacturer’s servicemen can avoid many problems. Vigilance on the part of the operating room staff can provide patient safety in the use of electrosurgery. 0 Notes 1. National Fire Protection Association, High frequency Electrical Equipment in Hospitals (Boston: National Fire Protection Association, 1970, NFPA No 76CM) 7.
AORN Journal, December 1975, Vol 22, No 6
Russell Church, R N , is codirector of the Urological Physician’s Assistant Program, University of Minnesota, General College, and Veterans Administration Hospital, Minneapolis. He is past president of the American Urological Association Allied Division. He received a BS i n nursing from the University of Minnesota. William T Hamlin is medical products manager for Ritter Company. He has a B S M E from the University o f Rochester.
lthough electrosurgery has been known in this country for 50 years, the most rapid changes in its use have occurred in the past five years. New types of electrosurgical units have appeared in the OR and other electrical devices are being attached to the patient. OR personnel should understand what electrosurgical equipment does, how the results are achieved, and why precautions are necessary. Recent trends in legislation, medical education, and patient-care standards emphasize the need for personnel to be well informed. OR personnel are directly concerned with the electrosurgical unit in several ways including the legal responsibility for its proper function. The proper attachment of equipment to the patient is critical. They must be familiar with the controls on the equipment so that the surgeon’s instructions can be carried out quickly and smoothly. They must know what situations are hazardous or contraindicated and what variables are important for the patient’s safety. Urology is a most demanding service in the use of electrosurgery; therefore, some special details are to considered. The first use of intense heat in surgery was a red-hot iron applied to a wound or stump to stop bleeding. A later change involved heating the iron by passing a n electrical current through it, the modality known as electrocautery today. The distinction between electrocautery and electrosurgery is that in electrocautery heat is transferred to the tissue from a preheated object. In electrosurgery, the heat is generated in the tissue by passage of high frequency electrical current. In simple terms, electricity is a force produced by rotating a loop of wire
AORN Journal, Deceniber 1975. Vol22. N o 6
903
lectrosurgical cutting is accomplished by cellular heating and cellular disintegration.
E
through a magnetic field. Electrons are caused to move in this manner, and properly drawn off of the wire loop, produce electrical current. If the wire loop is rotated 60 times each second, the frequency of the generated electricity is 60 cycles per second (60 cps), the standard frequency of electricity we use in homes. Depending upon how the electrons are drawn off of the wire loop, direct current (DC) can be produced where the electron force moves in one direction only. If the electrons ebb and flow, that is, frequently reverse direction, alternating current (AC) is produced. Sixty cycles every second is referred to as low frequency current. Frequencies can range from 100,000 to 3,000,000 times per second. These are the radio frequency (RF) or high frequency currents. When electricity is applied to the body, tissue fluids act as an electrical conductor because of the electrolytes they contain. The low frequency alternating current tends to move the cellular ions to and fro, polarizing the cell. This causes a neuromuscular activity which can range from a tingling sensation to a painful contraction. It can be fatal if it interferes with the electrical conductivity of the heart. When electrical frequencies reach 20,000 or 50,000 cycles per second, the cellular ions cannot totally react so rapidly, and no electrical conduction is
904
discernable. However, the cellular ions are in rapid, though limited motion. They collide frequently and release energy in the form of heat. This is the basis of the cellular destruction caused by the electrosurgical unit. In other words, cutting is accomplished by cellular heating-instantaneous vaporization of cellular water-and cellular disintegration. The first work in this field was done around the turn of the century by Tesla, D’Arsonval, and Riviere. Later, DeForest built the first vacuum tube generator, which was well accepted and used in Paris and Vienna. This vacuum tube generator was not suited to controlling bleeding. In the late 1920s, Harvey Cushing and Dr W T Bovie worked with George H Liebel and Edwin S Flarsheim in the development of a spark-gap electrosurgical unit. The first Bovie electrosurgical unit provided a cutting current which could cut cleanly and provided variable amounts of hemostasis to seal bleeders and capillaries. Combinations of vacuum tube cutting current generators with spark-gap cutting and coagulation units continue to be manufactured and are used in many hospitals today. Around 1970, a new method of generating electrosurgical currents was developed with a variety of solid state units. These units produce essentially the same RF current, but
AORN Journal, December 1975, Vol22, No 6
use transistors, diodes, and rectifiers instead of spark-gaps or tubes to generate the current. The greatest difference between solid s t a t e and spark-gap/tube units (other than unit size) seems to be in coagulation. Either type will cut readily, but the solid state units provide a “pin-point” coagulation rather than a ‘‘spray” coagulation. This is not always acceptable where large bleeding areas are
Fig 1. A low concentration of high frequency current produces a gentle, deep tissue warming. This penetrating heat is beneficial in the treatment of joint pain of rheumatoid arthritis and muscular pains.
encountered such as in open heart surgery and in some transurethral procedures. The basic principle of electrosurgery is that when electrical current flows through a resistance, heat is produced. Common examples of this phenomenon are the electrical soldering iron and the electric blanket. It is apparent that when energy is concentrated in a small area as in the tip of the soldering iron, very high temperatures result. The same amount of energy spread over a large area, as in an electric blanket, gives a much lower rise in temperature. Medical diathermy this principle with two to produce large heat for pain relief and an imrease in circulation in the treated area (Fig 1). Surgical diathermy or electrosurgery reduces the size of one of the electrodes
to the point where intense current concentration causes destruction of tissue or a cutting or coagulation effect a t the smaller electrode (Fig 2). The distinction between cutting and coagulating is achieved basically by varying the amount of dampening or interruption of the current. The undamped current of a tube generator or solid state generator will cut freely and smoothly, but will have little hemostatic effect. Damping the current increases the hemostatic effect. Solid state units have not been able to duplicate completely the coagulation effects possible with the spark-gap type generators. Some surgeons are willing to modify the technique and feel that the advantages of the solid state units outweigh this requirement with greater precision in pinpointing bleeders. Others feel that there is no substitute for the spark-gap generator current in cases where massive coagulation is required. The effects of electrosurgery depend upon the flow of high frequency electrical current through the patient’s tissues. The current enters the body a t the active electrode and returns to the electrosurgical unit through the dis-
Fig 2. When a high concentration of R f current is applied to tissues, mechanical disruption produces a cutting effect. Since it is the same principle as diathermy, improper amlication moduces deeD. Dainful burns. I
,
AORN Journal, December 1975, Vol22, N o 6
-
1
,
905
Correct Flow
j&
Fig 3. A variety of dispersion devices are available today.
persive (inactive or ground) plate. At the dispersive plate, maximum area or electrical contact or both is required to achieve minimum heating effect. In this country, the dispersive plate can vary from the stainless steel plate supplied by the manufacturers of electrosurgical units to a variety of disposable dispersive electrodes. Saline pads and lead plates, still reported in Europe, are not presently in use in any United States hospital. Whatever dispersive plate is used with the electrosurgical unit, it should ensure a sufficient area of contact with the patient to avoid any temperature rise at this point (Fig 3). The National Fire Protection Association recommends a minimum of one square centimeter per one and one-half watts of power output from the electrosurgical unit.’ This works out t o approximately 27 square inches for the average fullsized hospital operating room electrosurgical unit. If the stainless steel plate is used, it should be completely clean and free of nonconductive soilage. Conductive gels and lubricants Fig 4. As more devices are connected to the patient, problems of interaction become more numerous.
906
should be nondrying so that they remain conductive over the period of long operations. It is best to use a conductive gel designed specifically for electrosurgery. Do not rely on some similar material which may be intended for electrocardiographs (ECG) o r other electroappraisals. Another reason why a dispersive plate and a conductive lubricant are required is that many other pieces of electrical equipment may be attached to the patient and alternate “grounds” may be provided (Fig 4). Any increase of resistance at the dispersive plate will tend to cause current to flow through these alternate paths. Unwanted current concentrations can and will cause patient burns. It is necessary to be sure that the dispersive electrode is not applied to hairy surfaces which tend to insulate or to bony protuberances which tend to concentrate electrical current. It is always best to keep the dispersive plate as close to the active site as possible to cut down the total current path. The current path should not include a
Incorrect Flow INACT IVE ELECTRODE
GROUND
Fig 5. Discontinuity in the grounding system may be external as illustrated, and, in rare instances, internal to the electrosurgical system. If current flow to alternate sites is substantial, radio-frequency burns may result.
GROUND
pacemaker or similar device, since some models of pacemakers may be deactivated by high frequency currents. A critical factor is the assurance that the connection between the dispersive plate and the electrosurgical unit is complete. A number of circuits and devices have been developed and are used either singly or in combination with other units. The earliest circuit for this purpose was the “circuit sentry’’ that relied on a signal being sent out from the machine to the dispersive plate and back to the machine. If either wire were broken, the unit was deactivated and a n alarm sounded. This circuit sentry could sometimes be fooled by some of the grounds from other patient connected devices (Fig 5 ) . Other electrosurgical units use the isolated output system. Theoretically, a n isolated output has no ground connection, and the RF current will not flow to other grounds. If the dispersive plate is grounded accidentally, however, the output is like any other grounded system, and the unit may be activated. There is also a patient sentry system which involves a monitoring current through the active lead and the pa-
tient back to the dispersive plate and its current. It is most helpful to know which system your particular electrosurgical unit has, and to know how it can be checked out. It should be checked each day. In the ideal world of the laboratory, it would be possible to place the patient on a wooden table with no other electrical equipment attached to him and have the electrosurgical unit work safely and effectively 10070 of the time. In the real world of the operating room where the patient is on a conductive table and there are conductive floors, the high frequency current will tend to ground through a variety of paths: the ECG electrodes, the surgeon’s gloves (and occasionally his eyebrow), and conductive anesthesia equipment. The use of a n approved dispersive electrode, properly applied, offers the lowest resistance path. This will reduce the possibility of undesired current concentrations at unexpected points and subsequent patient burns. For the use of electrosurgery in urology, the following suggestions will help reduce problems. Combination spark-gap and tube electrosurgery units should have the selector switch left in some other position than No 1 Tube
AORN Journal, December 1975, V o l 2 2 , No 6
907
Cutting unless that modality is being used. This keeps the filaments from being turned on and lengthens the life of the tubes. be checked 0 Spark-gaps should periodically and may be cleaned with an abrasive strip when they first start growing peaks and valleys on the gap facings. Gaps require replacement a t periodic intervals depending upon use. 0 Cutting loops should be checked to be sure that the insulation is complete. The proximal end of the loop must be inserted as far as it will go into the resectoscope block before securing it. If this is not done, the current will arc and burn the block, which ruins the block and the operation. 0 Loops should be checked to be sure that they have not been bent accidently or intentionally. This seriously shortens the life of the loop, and intentional reshaping of the loop accomplishes little. One manufacturer suggests that a cutting loop should be used only once and discarded. 0 Conductive lubricants must never be used on the sheath of a resectoscope, and nonconductive solutions must be used as an irrigating media during transurethral resecting procedures. There have been cases where the irrigating solution was changed during the course of the operation. The introduction of a “hard’ or saline solution causes dispersion of power and complete loss of cutting ability. 0 Sheaths are sometimes charred if faulty coordination allows the unit to remain activated after the loop completes its excursion through the tissue. This is aggravated by needlessly high power settings and slow cuts. The use of
908
too high a power setting and too slow a cut also can overcoagulate the tissue and build up a cumulative wall of coagulum which becomes increasingly difficult to cut with each excursion of the loop. In each case, the surgeon should use the unit a t the lowest setting which will accomplish the desired results. Any demand for an increase in power should warrant a check of the active electrode and cord as well as the dispersive plate and its grounding cord to be sure that these items have not become accidentally disconnected or faulty. 0 When using the solid state electrosurgical unit to coagulate, it is essential that the loop contact the exact point of the bleeder. Sparkgap units tend to provide a spraytype coagulation that can be used to cover a broader area. Another area of hazard with electrosurgery is that any electrosurgical unit is capable of producing a spark a t the active electrode. For this reason, it should not be used in the presence of flammable anesthetics. Flammable skin preparations should be avoided or allowed to dry thoroughly since there have been occasions where these have been ignited. A less obvious hazard is the flammable gases present in the colon. If electrosurgery is to be used in that area, a nitrogen or carbon dioxide atmosphere should be provided. A preventive maintenance program, including cords and accessories, by hospital staff or manufacturer’s servicemen can avoid many problems. Vigilance on the part of the operating room staff can provide patient safety in the use of electrosurgery. 0 Notes 1. National Fire Protection Association, High frequency Electrical Equipment in Hospitals (Boston: National Fire Protection Association, 1970, NFPA No 76CM) 7.
AORN Journal, December 1975, Vol 22, No 6
