• Electrocautery
• Principles of Electrosurgery in the OR
• Frequency Spectrum
• Bipolar Electrosurgery
• Monopolar Electrosurgery
• Tissue Effects Change as You Modify the Waveform
• Electrosurgical Tissue Effects
  Electrosurgical Cutting
  Fulguration
  Desiccation
• Variables Impacting Tissue Effects
• Tissue Response Technology
• Grounded Electrosurgical Systems
  RF Current Division
• Isolated Electrosurgical Systems
  Isolated System
  Deactivated Isolated System
• Patient Return Electrodes
  Function of the Patient Return Electrode
  Ideal Return Electrode Contact with Current Dispersion
  Dangerous Return Electrode Contact with Current Concentation
  Assess Pad Site Location

• Patient Return Electrode Monitoring Technology
• Electrosurgery Safety Concerns During MIS
• Direct Coupling
• Insulation Failure
• Capacitive Coupling During Endoscopy
  Metal Cannula System
  Plastic Cannula System
  Hybrid Cannula System
• Recommendations to Avoid Electrosurgical Patient Complications in MIS
• Coated Electrodes
• Argon-Enhanced Electrosurgery
  Argon Flow
  Properties of Argon Gas
  Argon-Enhanced Coagulation and Cut
• Surgical Smoke
  Spectral Content of Surgical Smoke
  Smoke Evacuation Devices
• AORN Recommended Practices for Electrosurgery
• OR Safety Precautions
• Bibliography

Often "electrocautery" is used to describe electrosurgery. This is incorrect. Electrocautery refers to direct current (electrons flowing in one direction)whereas electrosurgery uses alternating current. During electrocautery,current does not enter the patient's body. Only the heated wire comes in contact with tissue. In electrosurgery, the patient is included in the circuit and current enters the patient's body.

Principles of electricity are relevant in the operating room. The electrosurgical generator is the source of the electron flow and voltage. The circuit is composed of the generator, active electrode, patient, and patient return electrode. Pathways to ground are numerous but may include the OR table,stirrups, staff members, and equipment. The patient's tissue provides the impedance, producing heat as the electrons overcome the impedance.

Standard electrical current alternates at a frequency of 60 cycles per second (Hz). Electrosurgical systems could function at this frequency, but because current would be transmitted through body tissue at 60 cycles, excessive neuromuscular stimulation and perhaps electrocution would result.

Because nerve and muscle stimulation cease at 100,000 cycles/second(100 kHz), electrosurgery can be performed safely at "radio"frequencies well above 100 kHz. An electrosurgical generator takes 60 cycle current and increases the frequency to over 300,000 cycles per second. At this frequency electrosurgical energy can pass through the patient with minimal neuromuscular stimulation and no risk of electrocution.

Bipolar Circuit

This picture represents a typical bipolar circuit.

Active output and patient return functions are both accomplished at the site of surgery.
Current path is confined to tissue grasped between forceps tines.
Patient return electrode should not be applied for bipolar only procedures.

In bipolar electrosurgery, both the active electrode and return electrode functions are performed at the site of surgery. The two tines of the forceps perform the active and return electrode functions. Only the tissue grasped is included in the electrical circuit. Because the return function is performed by one tine of the forceps, no patient return electrode is needed.

Monopolar Circuit

This picture represents a common monopolar circuit. There are four components to the monopolar circuit:

• Generator
• Active Electrode
• Patient
• Patient Return Electrode

The active electrode is in the wound.
The patient return electrode is attached somewhere else on the patient.
The current must flow through the patient to the patient return electrode.

Monopolar is the most commonly used electrosurgical modality. This is due to its versatility and clinical effectiveness. In monopolar electrosurgery, the active electrode is in the surgical site. The patient return electrode is somewhere else on the patient's body. The current passes through the patient as it completes the circuit from the active electrode to the patient return electrode.

Electrosurgical cutting divides tissue with electric sparks that focus intense heat at the surgical site. By sparking to tissue, the surgeon produces maximum current concentration. To create this spark the surgeon should hold the electrode slightly away from the tissue. This will produce the greatest amount of heat over a very short period of time, which results in vaporization of tissue.

Cut- Low voltage waveform, 100% duty cycle

Coag- High voltage waveform, 6% duty cycle

Electrosurgical desiccation occurs when the electrode is in direct contact with the tissue. Desiccation is achieved most efficiently with the "cutting" current. By touching the tissue with the electrode, the current concentration is reduced. Less heat is generated and no cutting action occurs. The cells dry out and form a coagulum rather than vaporize and explode.

Many surgeons routinely "cut" with the coagulation current. Likewise, you can coagulate with the cutting current by holding the electrode in direct contact with tissue. It may be necessary to adjust power settings and electrode size to achieve the desired surgical effect. The benefit of coagulating with the cutting current is that you will be using far less voltage. Likewise, cutting with the cut current will also accomplish the task with less voltage. This is an important consideration during minimally invasive procedures.

1. Waveform
2. Power setting
   In addition to waveform and power setting, other variables impact tissue effect. They include:
3. Size of the electrode: The smaller the electrode, the higher the current concentration. Consequently, the same tissue effect can be achieved with a smaller electrode, even though the power setting is reduced.
4. Time: At any given setting, the longer the generator is activated, the more heat is produced. And the greater the heat,the farther it will travel to adjacent tissue (thermal spread).
5. Manipulation of the electrode: This can determine whether vaporization or coagulation occurs. This is a function of current density and the resultant heat produced while sparking to tissue versus holding the electrode in direct contact with tissue.
6. Type of tissue: Tissues vary widely in density and resistance.
7. Eschar: Eschar is relatively high in resistance to current. Keeping electrodes clean and free of eschar will enhance performance by maintaining lower resistance within the surgical circuit.

Comparison in Pure Cut mode of a tissue response generator and conventional generators.

There is now generator technology which has a feedback circuit that senses tissue density. Computer-controlled output automatically adjusts the voltage delivered in the cut modes to instantly respond to the varying densities of the target tissue. This maintains a constant output power to produce a consistent tissue effect.

Grounded Electrosurgical Systems

Electrosurgical technology has changed dramatically since its introduction in the 1920's. Generators operate by taking alternating current and increasing its frequency from 50 or 60 cycles/second to over 300,000 cycles/second. Originally, generators used grounded current from a wall outlet. It was assumed that,once the current entered the patient's body, it would return to ground through the patient return electrode. But electricity will always seek the path of least resistance. When there are many conductive objects touching the patient and leading to ground,the current will select as its pathway to ground the most conductive object -- which may not be the patient return electrode. Current concentration at this point may lead to an alternate site burn.

Alternate Site Burn

With the phenomenon called current division,the current completes the circuit to ground whether it travels the intended electrosurgical circuit to the patient return electrode or to an alternate site. Patients are thereby exposed to the risk of alternate site burns because (1) current always follows the easiest, most conductive path; (2) any grounded object, not just the generator, can complete the circuit; (3) the surgical environment offers many alternative routes to ground; (4) if the current is sufficiently concentrated at an alternate site, a burn will occur.

This picture shows an alternate site burn that occurred when a grounded electrosurgical generator was used. The ECG electrode provided the path of least resistance to ground. However, it did not disperse the current over a large enough area. The heat produced an alternate site burn under the ECG electrode due to current concentration.

In 1968, electrosurgery was revolutionized by isolated generator technology. The isolated generator isolates the therapeutic current from ground by referencing it within the generator circuitry. In other words, in an isolated electrosurgical system, the circuit is completed not by the ground but by the generator. Even though grounded objects remain in the operating room, electrosurgical current from isolated generators will not recognize grounded objects as pathways to complete the circuit. Isolated electrosurgical energy recognizes the patient return electrode as the only pathway back to the generator.

By removing ground as a reference for the current, the isolated generator eliminates many of the hazards inherent in grounded systems, most importantly current division and alternate site burns.

Historically, patient return electrode burns have accounted for 70% of the injuries reported during the use of electrosurgery. Patient return electrodes are not "inactive"or "passive". The only difference between the "active"electrode and the patient return electrode is their size and relative conductivity. The quality of the conductivity and contact at the pad/patient interface must be maintained to prevent a return electrode site injury.

The function of the patient return electrode is to remove current from the patient safely.
A return electrode burn occurs when the heat produced, over time,is not safely dissipated by the size or conductivity of the patient return electrode.

BURN = HEAT X TIME / AREA

The ideal patient return electrode safelyc ollects current delivered to the patient during electrosurgery and carries that current away. To eliminate the risk of current concentration, the pad should present a large, low impedance contact area to the patient. Placement should be on conductive tissue that is close to the operative site.

Again, the only difference between the "active" electrode and the patient return electrode is their relative size and conductivity. Concentrate the electrons at the active electrode and high heat is produced. Disperse this same current over a comparatively large patient return electrode and little heat is produced.

If the surface area contact between the patient and the return electrode is reduced, or if the impedance of that contact is increased, a dangerous condition can develop. In the case of reduced contact area, the current flow is concentrated in a smaller area. As the current concentration increases, the temperature at the return electrode increases. If the temperature at the return electrode site increases enough, a patient burn may result. Surface area impedance can be compromised by: excessive hair, adipose tissue, bony prominences, fluid invasion, adhesive failure, scar tissue and many other variables.

Choose:
Well vascularized muscle mass

Avoid:
Vascular insufficiency
Irregular body contours
Bony prominences

Consider:
Incision site/prep area
Patient position
Other equipment on patient

REM™ contact quality monitoring was developed to protect patients from burns due to inadequate contact of the return electrode. Pad site burns are caused by increased impedance at the return electrode site. REM™-equipped generators actively monitor the amount of impedance at the patient/pad interface. The system is designed to deactivate the generator before an injury can occur, if it detects a dangerously high level of impedance at the patient/pad interface.

In order to work properly, REM™-equipped generators must use a patient return electrode that is compatible. Such an electrode can be identified by its "split" appearance-- that is, it has two separate areas -- and a special plug with a center pin. REM™ technology has been safely used in over 95,000,000 procedures.

Electrosurgery Safety Considerations During MIS

• Direct Coupling
• Insulation Failure
• Capacitive Coupling
  
  When electrosurgery is used in the context of minimally invasive surgery, it raises a new set of safety concerns. Some of these are: insulation failure, direct coupling of current, and capacitively coupled current.

Direct coupling occurs when the user accidentally activates the generator while the active electrode is near another metal instrument. The secondary instrument will become energized. This energy will seek a pathway to complete the circuit to thepatient return electrode. There is potential for significant patient injury.

Do not activate the generator while the active electrode is touching or in close proximity to another metal object.

Many surgeons routinely use the coagulation waveform. This waveform is comparatively high in voltage. This voltage or "push" can spark through compromised insulation. Also, high voltage can "blow holes" in weak insulation. Breaks in insulation can create an alternate route for the current to flow. If this current is concentrated, it can cause significant injury.

You can get the desired coagulation effect without high voltage,simply by using the "cutting" current while holding the electrode in direct contact with tissue. This technique will reduce the likelihood of insulation failure. Remember, you can coagulate with the cutting current by holding the electrode indirect contact with tissue, thereby lowering the current concentration. By lowering current concentration you will reduce the rate at which heat is produced and rather than vaporize tissue you will coagulate - even though you are activating the "cutting"current.

A capacitor is not a part labeled "capacitor"in an electrical device. It occurs whenever a nonconductor separates two conductors.

During MIS procedures, an "inadvertent capacitor" maybe created by the surgical instruments. The conductive active electrode is surrounded by nonconductive insulation. This, in turn, is surrounded by a conductive metal cannula.

A capacitor creates an electrostatic field between the two conductors and, as a result, a current in one conductor can, through the electrostatic field, induce a current in the second conductor.

In the case of the "inadvertent capacitor" in an MIS procedure, a capacitor may be created by the surgical instrument's composition and placement.

Capacitance cannot be entirely eliminated with an all plastic cannula. The patient's conductive tissue completes the definition of a capacitor. Capacitance is reduced, but is notw eliminated.

The worst case occurs when a metal annuals held in place by a plastic anchor (hybrid cannula system).The metal cannula still creates a capacitor with the active electrode. However, the plastic abdominal wall anchor prevents the current from dissipating through the abdominal wall. The capacitively coupled current may exit to adjacent tissue on its way to the patient return electrode. This can cause significant injury.

Most potential problems can be avoided by following these simple guidelines:

• Inspect insulation carefully
• Use lowest possible power setting
• Use a low voltage waveform (cut)
• Use brief intermittent activation vs. prolonged activation
• Do not activate in open circuit
• Do not activate in close proximity or direct contact with another instrument
• Use bipolar electrosurgery when appropriate
• Select an all metal cannula system as the safest choice. Do not use hybrid cannula systems that mix metal with plastic
• Utilize available technology, such as a tissue response generator to reduce capacitive coupling or an active electrode monitoring system, to eliminate concerns about insulation failure and capacitive coupling.

NOTE: Any cannula system may be used if an active electrode monitor is utilized.

Teflon® (PTFE) Coating and Elastomeric Silicone Coating

• Reduces eschar build-up which can lead to increased resistance on the surface of the electrode.
  • Eschar can cause arcing of current to adjacent tissue
  • Arcing increases the risk of a fire, especially in an oxygen-enriched environment
• Wipes clean with a sponge
  • Eliminates the need for a "scratch pad" which creates grooves on a stainless steel electrode that may contribute to eschar build-up
• Saves time

Elastomeric Silicone Coated Electrode

• Retains cleaning properties longer
• Bendable
• Coating will not crack or flake
• Cutting edge performance similar to stainless steel electrode
• Enables surgeon to use lower power settings
  • Reduces potential for thermal spread.

Argon-Enhanced Electrosurgery

Argon-enhanced electrosurgery incorporates a stream of argon gas to improve the surgical effectiveness of the electrosurgical current.

Argon gas is inert and noncombustible making it a safe medium through which to pass electrosurgical current. Electrosurgical current easily ionizes argon gas, making it more conductive than air. This highly conductive stream of ionized gas provides the electrical current an efficient pathway.

• Inert
• Noncombustible
• Easily ionized by RF energy
• Creates bridge between electrode and tissue
• Heavier than air
• Displaces nitrogen and oxygen

There are many advantages to argon-enhanced electrosurgical cutting and coagulation.

• Less smoke, odor
• Noncontact in coagulation mode
• Reduced drag and tissue adhesion to electrode in cut
• Less tissue damage
• Flexible eschar

Surgical smoke is created when tissue is heated and cellular fluid is vaporized by the thermal action of an energy source.

Research has shown that smoke from electrosurgery is similar in content to that produced by a surgical laser. If you currently evacuate the plume from a laser, you should do likewise for smoke created by electrosurgical generators. Viral DNA, bacteria, carcinogens,and irritants are known to be present in electrosurgical smoke. Universal precautions indicate a smoke evacuation system should be used.

New products have been introduced to make smoke evacuation easier and more effective. Smoke evacuation devices can now be attached directly to a standard electrosurgical pencil.

"An evacuation system should be used to remove surgical smoke."
Patients and perioperative personnel should be protected from inhaling the smoke generated during electrosurgery."

AORN Recommended Practices for
Electrosurgery 1997

The Association of Operating Room Nurses revised the Recommended Practices for Electrosurgery in the 1994 AORN Standards and Recommended Practices for Perioperative Nursing. It now includes a recommendation for evacuation of all surgical smoke.

• "The ESU should not be used in the presence of flammable agents (i.e., alcohol and/or tincture-based agents)"
  
• Avoid oxygen enriched environments.
  
• ALWAYS use an insulated safety holster to store active electrodes when not in use.

"The active electrode(s) should be placed in a clean, dry, nonconductive safety holster, in a highly visible area when not in use."

AORN Recommended Practices for Electrosurgery 1994

1. AAGL Technical Bulletin Committee, "Electrosurgical Safety", AAGL Technical Bulletin, January, 1995, No. 1, pages 1-7
2. Lucy Jo Atkinson, "Biotechnology: Specialized Surgical Equipment",Chapter 15, Berry & Kohn's Operating Room Technique Eighth Edition, Mosby-Yearbook, 1996, pages 265-270
3. Barbara J. Gruendemann, Billie Fernsebner, "Technology Management:Electrosurgery", Chapter 10 Comprehensive Perioperative Nursing Volume I Principles, Jones and Bartlett Publishers 1995, pages 315-323
4. Margaret Huth Meeker, Jane C. Rothrock, "Patient and Environmental Safety" Chapter 2, Alexander's Care of the Patient in Surgery Tenth Edition, Mosby-Yearbook 1994, pages 24-28
5. "Monopolar Electrosurgical Safety During Laparoscopy"ECRI Health Devices, January, 1995, Vol. 24, No. 1, pages 6-27
6. "Recommended Practices For Endoscopic Minimal Access Surgery",AORN Standards and Recommended Practices for Perioperative Nursing, Association of Operating Room Nurses, Inc, Denver,Colorado: 1997, Section 3, pages 175-180
7. Recommended Practices for Electrosurgery,AORN Standards and Recommended Practices for Perioperative Nursing, Association of Operating Room Nurses, Inc, Denver,Colorado, 1997, Section 3, pages 163-168
8. Robert D. Tucker, C. Randle Voyles, "Laparoscopic Electrosurgery:Complications and Prevention", AORN Journal, July,1995, Vol. 62, No. 1, pages 49-78
9. "Update: Controlling the Risks of Electrosurgery", ECRI Health Devices, December, 1989, Vol. 18, No. 12, pages 430-432
10. Theirry G. Vancallie, "Electrosurgery: Principles and Risks"Center for Gynecologic Endoscopy, San Antonio, Texas, 1994
11. Beverly P. Giordano, "Don't Be a Victim of Surgical Smoke", AORN Journal, March, 1996, Vol. 63, No. 3
12. "Control of Smoke From Laser/Electric Surgical Procedures", NIOSH Hazard Controls, DHHS(NIOSH) Publication No. 96-128, September, 1996
13. Charles R. Yeh, "Surgical Smoke Plume Principles and Function of Smoke, Aerosol, Gases, and Smoke Evacuators",Surgical Services Management, April, 1997, Vol. 3, No. 4, pages 41-44