Electrosurgery: the newest energy-based devices

October 1, 2013

Electrosurgical instruments aid skilled surgeons in performing safe cutting-edge procedures.

 

Dr. Sobolewski is Chief, Division of Minimally Invasive Gynecologic Surgery, Duke University, Durham, North Carolina. He reports receiving honoraria from and/or holding ownership interest in Covidien, AbbVie, and TransEnterix.

 

Use of electrosurgery is pervasive in gynecologic abdominal procedures. The technology also is common for many vaginal and operative hysteroscopic procedures. But formalized training in the safe and effective use of electrosurgery is lacking. With the exception of the use of laser energy, there is no uniform credentialing process to allow surgeons to operate with devices that apply electrical energy to tissues.

Industry-sponsored events and sales representatives provide much of the training in the use of new surgical devices. In residency, most education is limited to observing a senior resident or attending surgeon. An understanding of how electrosurgical instruments interact with tissue is essential to their safe use.

Understanding cut, coagulation, and blend waveforms

Electrosurgical devices create the effect that they have on tissues by generating heat. In fact, all modern surgical energy devices, including ultrasonic energy, laser energy, and plasma energy, work by creating heat.

With electrosurgery, the heat is generated as electrons flowing through tissue meet resistance to that flow. This is referred to as resistive heating.1 If high temperatures are generated rapidly, the result is boiling of the intracellular water. Increased pressure inside the cell causes the cell wall to explode. As the cells are disrupted, tissue dissection occurs. Because the heat dissipates rapidly as steam or plasma, adjacent tissues receive only very minimal heat.

When using monopolar electrosurgical devices, resistive heating occurs best with the “pure cut” waveform. In the pure cut mode, energy is delivered continuously and can be described as a high current/low voltage waveform. In contrast, in “coagulation mode,” the current is interrupted and, in fact, is “on” only 6% of the time. This interrupted deliv protein denaturation and formation of a coagulum.

Compared with pure cut current, coagulation current is a low current/high voltage form of electrosurgical energy. With higher voltage, the heat generated has a greater potential to deeply penetrate tissue. Therefore, although coagulation current may generate lower tissue temperatures, the higher voltage can result in substantially greater and potentially unrecognized lateral thermal spread.

Understanding this fundamental difference is critically important for a gynecologic surgeon, especially because the names assigned to these waveforms imply different clinical effects. The word “cut” sounds more dangerous than the word “coagulate,” but it is possible that cut current will be far safer if the goal is to minimize lateral thermal spread.

Modern electrosurgical units (ESUs) have begun to address this important issue of voltage by evolving into “adaptive” generators.2 These ESUs are capable of determining tissue resistance that is encountered by the tip of the electrode and relaying that information back to the generator. The ESU, in turn, adjusts its internal algorithms to ensure that there are no voltage spikes and that power output remains constant. That may allow the surgeon to achieve the same clinical effect at lower wattage settings than required by generators.

As with medications, using the lowest “dose” of electricity over the shortest time may be the safest way to operate with energized devices.

Newer waveform technology

In addition to the standard “cut,” “coagulate,” and “blend” waveforms, one ESU manufacturer has used adaptive technology to develop a new waveform.

The Valleylab waveform is a modulated waveform that originates as a coagulation current, unlike “blend current,” which is a modulated cut current waveform. Using the adaptive properties of the ESU, the voltage of the new waveform is controlled such that there is less tissue drag than with pure coag current, but improved hemostasis as compared with pure cut current.

So now, surgeons who are accustomed to electrosurgical pencils with only 2 buttons (yellow for cut and blue for coagulate) now may use a third button for application of this new Valleylab waveform.

Surgeon-controlled variables

Choosing the color of button or pedal to push is only one way that the surgeon can impact how electrosurgical instruments can affect what happens at the tissue level. Other variables include electrode size and shape, contact with tissue as energy is applied, and length of time of energy administration.

The effect that energy has on tissue is quite different, for example, if a surgeon uses a needle electrode rather than a ball electrode. With the former, the electrons are concentrated at the needle tip and as they are discharged, they rapidly create heat and tissue separation. At the same wattage setting with the ball electrode, tissue desiccation is more likely than dissection because the electrons are widely distributed across the surface of the ball.

Likewise, if a surgeon moves the instrument rapidly, penetration is more superficial than the deep penetration that would occur if the instrument were held in place or moved slowly. So the surgeon controls many variables that can impact what he or she sees at the tissue level when operating with monopolar electrosurgical instruments.

Thermal injury

Surveys have shown that up to 18% of surgeons have experienced a thermal injury complication during laparoscopic surgery.3,4 A significant portion of the shaft of the typical laparoscopic electrosurgical instrument is not visible on the video monitor, creating a potential for unrecognized injury. Instrument insulation failure and direct and capacitive coupling can cause stray energy burns. All of these are more likely to occur with the use of a high-voltage waveform (coagulation current).1

A capacitor is created when an insulator (eg, the coating of the shaft of an instrument) separates 2 conductors (eg, the metal conductor inside the shaft and a metal laparoscope). If enough energy is stored within this capacitor, it can discharge spontaneously. “Open-air-activation” can also contribute to this. Open-air-activation refers to activating the button or pedal before the electrode tip is near the target tissue. The result is accumulation of electrons along the electrode’s surface, which can build up enough energy within the capacitor to produce a spontaneous discharge to surrounding structures, resulting in injury.

Insulation failure is more difficult to predict and the most common cause of electrosurgical energyrelated thermal injury.4 Montero et al found evidence of insulation failure in 19% of reusable and 3% of disposable instruments used in cholecystectomy instrument sets at 4 hospitals.5

A technology referred to as active electrode monitoring (AEM) is designed to detect both insulation failure and capacitive coupling. By integrating a coaxial conductive shield into the shaft of the instrument and running that through the AEM monitor, the system can detect insulation failure and deactivate the ESU before energy is delivered (Figure 1).

Figure 1. An active electrode monitoring device.

Although the adaptive properties of modern ESUs have minimized but not eliminated risk of capacitative coupling by reducing potential high-voltage peaks, this is true only in instruments with intact insulation. With the growing government focus on reducing complications, there may be increased interest in maximizing risk reduction. This may result in a growing interest in technologies such as AEM that are currently available but not very well known because of limited marketing.

Strategies that can help reduce the potential for stray monopolar energy injuries include using lowvoltage waveforms (cut current) and lower wattage settings, avoiding open-air-activation, and using AEM instrumentation.

Bipolar versus monopolar instruments

In general, risk of unrecognized thermal injuries is lower but not completely eliminated with use of bipolar electrosurgical instruments. A traditional Kleppinger-style bipolar instrument creates a great deal of lateral thermal spread. In fact, that is what a surgeon requires in order to achieve effective tubal desiccation during laparoscopic sterilization. Such thermal spread, however, may be undesirable when the instrument is being used to control uterine vasculature in an area adjacent to the ureter.

The modern generation of bipolar vessel sealer/ cutting devices uses the adaptive technology present in today’s ESUs to deliver controlled, low-voltage energy with very minimal lateral thermal spread. Currently available advanced bipolar devices on the market in the United States include the PlamaKinetics System, LigaSure, EnSeal, and Caiman. Each of these devices is approved to seal and cut tissue pedicles up to 7 mm in diameter. Some of these instruments include the Thunderbeat platform from Olympus, which integrates both ultrasonic and advanced bipolar technologies (Figure 2). The LigaSure Advance incorporates both advanced bipolar and monopolar technologies (Figure 3). The Caiman 12 Plus offers an articulating 12-mm instrument (Figure 4).

Figure 2. The THUNDERBEAT platform. Courtesy of Olympus America, Inc., Center Valley, PA.

Figure 3. The LigaSure Advance. Courtesy of Covidien, Boulder, CO.

Figure 4. The Caiman 12 Plus. Courtesy of Aesculap, Inc., Center Valley, PA.

Strictly speaking, electrosurgery is defined as the interaction of electrons with tissue to achieve a desired clinical effect. As with monopolar instruments, bipolar instruments generate heat within the tissue pedicle via the interaction of the electrons within the tissue itself delivered via alternating current (AC).

The Altrus Thermal Tissue Fusion system fits that definition but it is not an electrosurgical instrument, although it uses electricity to create heat that in turn achieves the desired tissue effect. In contrast with true electrosurgical instruments, the Altrus system uses direct current (DC) to heat the jaws of the instrument and then passively transfer that heat to the tissue (Figure 5). No electricity enters the patient through the device. The system monitors the temperature at the jaws and then bladelessly cuts through tissue. It comes in both 10-mm and 5-mm options.

Figure 5. The Altrus system. Courtesy of ConMed, Centennial, CO.

The PlasmaJet system is not strictly an electrosurgical device either, but use of direct current electrical energy is necessary to eventually create the heat needed to treat tissue. In the case of this system, a beam of argon gas is energized when it passes through a low DC voltage that is applied between internal bipolar electrodes. This separates the argon gas atoms into positive and negative ions and creates the fourth state of matter known as plasma.

The PlasmaJet system releases its energy in 3 ways: light, heat, and kinetic energy. The effect at the tissue level is influenced by how close the jet of ionized gas is to the tissue, which handpiece is chosen, and which button is pushed on the handpiece. The maximum depth of tissue penetration effect is only 2 mm, reached after 5 seconds of continuous application.

Conclusion

Safe application of energy-based surgical devices lies in the hand of the surgeon. A sound understanding of the fundamentals of surgical practice is still of prime importance.

Adherence to standards for careful surgical dissection, appropriate exposure of the surgical field, and a thorough knowledge of anatomy are still necessary regardless of all of the advances in modern technology.

 

REFERENCES

1. Brill A. Electrosurgery: principles and practice to reduce risk and maximize efficiency. Obstet Gynecol Clin N Am. 2011;38(4):687–702.

2. Vilos G, Rajakumar C. Electrosurgical generators and monopolar and bipolar electrosurgery. J Minim Invasive Gynecol. 2013;20(3):279–287.

3. Abu-Rafea B, Vilos G, Al-Obeed O, et al. Monopolar electrosurgery through single-port laparoscopy: a potential hidden hazard for bowel burns. J Minim Invasive Gynecol. 2011;18(6):734–740.

4. Odell R. Surgical complications specific to monopolar electrosurgical energy: engineering changes that have made electrosurgery safer. J Minim Invasive Gynecol. 2013;20(3):288–298.

5. Montero PN, Robinson TN, Weaver JS, Stiegmann GV. Insulation failure in laparoscopic instruments. Surg Endosc. 2010;24(2):462–465.