Electrosurgery as an Adjunct to Minimally Invasive Procedures

Laparoscopy is rapidly becoming a widely accepted technique for surgery in veterinary medicine. While the use of laparoscopy as a minimally invasive approach is quickly gaining in popularity there are certain aspects of the procedure that make it more challenging including intracorporeal suturing. Intracorporeal suturing is more challenging than open suturing for many reasons, including; long instrument length, using a two dimensional monitor to observe the surgical procedure, the fulcrum of the body wall, and lack of "touch" with the tissue. To this end, many companies have developed products to aid the surgeon in performing surgery in the endoscopic environment. The main purpose of all of these technologies is to provide hemostasis in the amputation of organs, or removal of tissue. When performing endoscopic surgery, the best way to deal with bleeding is to prevent it, as irrigation can be difficult, and visibility severely hampered by hemorrhage. Flexible Endoscopic surgery has become more common with the advent of video endoscopes. Using electrosurgical devices allows the surgeon to perform surgeries on the upper respiratory tract, uterus, and bladder without external incisions. Some of these devices used in both rigid and flexible endoscopy include: staplers, ligating loops, lasers, monopolar electrosurgery, bipolar electrosurgery, ultrasonic cutting/coagulating machines, and radiofrequency devices. This chapter will discuss electrosurgical devices including: monopolar and bipolar electrosurgery, ultrasonic cutting/coagulating devices, radiofrequency devices and lasers used in rigid and flexible endoscopy.

Monopolar Electrosurgery

General Characteristics [1]

Monopolar electrosurgery requires the use of an electrosurgical generator, an active electrode, and a grounding pad (Fig. 1). The energy passes through the body from the active electrode to the passive return electrode. When cutting using monopolar electrosurgery, the tissues are divided by focusing the electrical current over a small area, causing vaporization or explosion of the cells. After the cells vaporize, heat is dissipated, minimizing heat transfer to deeper tissues. Consequently, coagulation and hemostasis are minimized. Technically this is done in a non-contact method. When the active electrode contacts the tissue, the current is less focused, causing a desiccation of cellular water leading to a coagulum. Thermal damage occurs over a greater area improving hemostasis. The tissue effects are controlled by the generator output. The heat generated at the tip of the active electrode is approximately 150°C causing 2 - 3 mm deep and 2.5 - 3 mm lateral tissue damage. It is generally considered that monopolar electrosurgery provides good cutting and coagulating activity.

Figure 1. Photograph of an electrosurgical generator with grounding pad.

Flexible Endoscopic Uses [2-5]

Monopolar electrosurgery requires special instrumentation that will fit through the instrument channel of the flexible endoscope. The electrodes must be long enough to extend beyond the endoscope to allow free movement of the scope during the procedure. Various instruments are available including wire loops, (Fig. 2) sphincterotomes or simple stylets. Any generator that will accept the wire electrodes will work for the surgical procedure. The grounding pad is secured to the neck, providing a wide, secure point of contact. It is of utmost importance to not activate the electrode until the plastic safety covering can be seen through the endoscope to prevent damage to the inside of the scope. The animals are sedated, and topical anesthesia is performed through the scope. The author has found that 20 mg of detomidine hydrochloride mixed in 1 liter of polyionic replacement fluids administered as needed through a jugular catheter provides excellent long term sedation. The drip rate can be increased if the horse wakes up, or slowed down if the horse is too sedate. When performing surgery, particular attention should be given to the adjacent and deep structures in order to prevent serious collateral damage to the tissue. This is obviously very important in the guttural pouches. Procedures that have been reported include correction of epiglottic entrapment, removal of subepiglottic cysts, amputation of pedunculated lesions such as polyps or neoplasia, removal of laryngeal granulation tissue, fenestration of the median septum of the guttural pouches, and abscess drainage. Settings will vary depending on the generator, the length of the electrode, and the tissue being resected. Electrodes in the shape of loops will generally be more useful in cases of granulation tissue or polyp removal whereas cutting stylets will be more useful in resection of the aryepiglottic folds or median septum of the guttural pouches.

Figure 2. Photograph of 1.5 m monopolar active electrode snare for flexible endoscopy. Inset shows wire snare.

Laparoscopic Uses [6,7]

Monopolar electrosurgery is probably the most commonly used electrosurgical modality in human laparoscopy. The main reason monopolar electrosurgery is so popular is the minimal cost associated with its use. Most surgical facilities already have electrosurgical generators, and many laparoscopic instruments have attachments that allow connection of wiring to act as the active electrode (Fig. 3a and Fig. 3b). One of the main benefits of monopolar electrosurgery is that you can attach the wiring to a pair of scissors and coagulate while cutting. However, as the power charge leaves the end of the instrument, it will return to the generator through the surrounding soft tissue and the grounding plate. The return to the grounding plate is unpredictable, and may lead to secondary soft tissue injury. It is very important to not let the active electrode come in contact with any other non-insulated structures such as cannulas or the telescope. This can happen inadvertently when a non-insulated instrument or cannula comes in contact with a soft tissue structure that has charge running through it from the active electrode. Consequently the best way to reduce inadvertent burns is to make sure that any non-insulated instruments do not contact any tissue. Monopolar electrosurgery has been used in all types of laparoscopic surgery using both scissors and grasping forceps. In many cases, monopolar electrosurgery is combined with other hemostasis techniques such as ligating loops.

Figure 3a. Photograph of monopolar laparoscopic grasper.

Figure 3b. Close-up of handle with arrow pointing to the cord attachment.

Bipolar Electrosurgery

General Characteristics [1]

Bipolar electrosurgery involves the use of an active electrode and a passive electrode similarly to monopolar electrosurgery, except that both electrodes are found in the surgical instrument. Consequently current passes only through the tissue that is placed between the jaws of the instrument, and no grounding is necessary. The cutting and coagulating effects are similar as for monopolar electrosurgery, except that in all cases, tissue contact is achieved. The heat generation, tissue damage, and coagulating ability are similar to monopolar electrosurgery, whereas the cutting ability is poor.

Laparoscopic Uses [8,9]

Bipolar electrosurgery has been shown to be very useful in laparoscopic surgery in the horse. The main limit in the author’s hands has been the quality and capability of the generator. A good generator is required to provide enough energy at the instrument tip to cauterize the tissue. The main detriment to bipolar electrosurgery is that the bipolar instruments do not incorporate a cutting blade, requiring sequential application of the instrument and scissors to transect the area of interest (Fig. 4). Bipolar electrosurgery has been successfully used for ovariectomy and cryptorchidectomy (Video 1).

Figure 4. Photograph of bipolar surgical instrument. Inset shows close up of electrodes.

Video 1 - 2.4 Mo. Video showing bipolar cautery for ovariohysterectomy in a Llama.

Ultrasonic Cutting/Coagulating Devices

General Characteristics [1]

Ultrasonic cutting and coagulating devices rely on sound waves to cause intended tissue effects. At high power levels and density, the sound waves can be used for tissue dissection, coagulation, and cutting. Ultrasonic surgical units consist of a generator, foot switch, and hand piece (Fig. 5). In most surgical units, the hand piece consists of a transducer and some type of blade system that vibrates at a frequency of 55,500 cycles per second at a distance of 50 to 100 microns per cycle. The blade configuration will determine the tissue effect. Sharper blades will cut faster with less coagulation, whereas blunt blades will cut slower with more coagulation. Some instruments are configured with jaws at the end where one portion of the jaw holds the tissue still, and the other portion of the jaw vibrates. The generator power level along with the blade type will determine the amount of energy delivered to the tissue. The amount of blade tissue contact, pressure, blade speed, and activation time will determine the tissue response to the energy delivered. Tissue coagulation occurs when the mechanical energy of the blade is transferred to the tissue, breaking tertiary hydrogen bonds. The friction and shear stress caused generate a moderate amount of heat, in combination with the breaking of hydrogen bonds leads to sticky protein coagulum. If more pressure is placed on the tissue, and the power setting increased, cutting occurs. The heat generated is generally less than 150°C, with 0.5 - 2.0 mm depth and 0.2 - 3 mm lateral tissue damage. The cutting and coagulating abilities are both considered good. Vessels up to 3 mm in diameter are thought to be reasonable for coagulation. One of the major benefits of ultrasonic surgery over electrosurgery is that there is no potential for passing electricity through the patient.

Figure 5. Photograph of Autosonix ultrasonic surgical unit (courtesy of Kendall TycoHealthcare, Mansfield MA).

Laparoscopic Uses [10-12]

A major benefit of ultrasonic cutting/coagulating devices in equine surgery is that hemostasis and transection can be performed with the same instrument, obviating the need to switch instruments. Benefits include potentially faster surgery time, and reduced chance of infection. The published uses of ultrasonic surgical devices have been limited to ovariectomy in standing horses (Fig. 6). However, the author has used the ultrasonic surgical devices for cryptorchid surgery as well. In one report, many of the mares undergoing ovariectomy had to have additional methods performed to achieve complete hemostasis. It is the author’s opinion that the vasculature of the ovarian pedicle is at the maximum allowable size for ultrasonic cutting/coagulating devices, and that additional devices, such as ligature clips, should be available during surgery to ensure complete hemostasis. However, the use of an ultrasonic cutting/coagulating device provided complete hemostasis in multiple cryptorchid surgeries. These devices have been shown to be very useful in adhesiolysis in human surgery, especially when using the blunt blades.

Figure 6. Intra-operative photograph of ovariectomy using ultrasonic cutting coagulating device. A. During procedure, B. After successful amputation of the ovarian pedicle. Note arrow pointing to ligature clip necessary to stop bleeding.

Radiofrequency Devices

General Characteristics

In general, radiofrequency devices are similar to electrosurgical devices. In this chapter, only specific devices that automatically control the energy delivered by measuring tissue impedance are considered. The frequency range for electrosurgical devices is typically between 300 kHz and 13 Mhz. At higher frequencies, the ions do not physically move and the main effect is of tissue heating. The heat that is formed occurs due to higher friction of the patient’s tissue than the rest of the circuit. These devices can be used in a monopolar or bipolar fashion. In most cases, the monopolar electrodes are used in arthroscopy whereas the bipolar electrodes are used in laparoscopy. The bipolar electrodes are essentially feedback controlled electrothermal sealers that apply a precise amount of energy to vessel walls to produce a denatured protein seal.

Laparoscopic Uses [13]

The most commonly used device in laparoscopic surgery is the LigaSure vessel-sealing device (Fig. 7) (LigaSure, Valley Lab/Tyco Healthcare, Boulder, CO). This device is available with both a 5 mm and a 10 mm handpiece that have integrated cutting blades. The LigaSure device is capable of sealing up to 7 mm vessels with minimal thermal spread to adjacent tissues. This device has been very effective in sealing vessels during equine ovariectomy (Fig. 8) and cryptorchidectomy. The author has removed a granulosa thecal cell tumor that measured 20 cm x 18 cm x 15 cm with no hemorrhage using the LigaSure device. The Ligasure device can also be used for adhesiolysis.

Figure 7. Photograph of LigaSure surgical unit (courtesy of Kendall TycoHealthcare, Mansfield MA).

Figure 8. Intra-operative photograph of ovariectomy using radiofrequency device. A. During procedure, B. After successful amputation of the ovarian pedicle.

Lasers

General Characteristics

Laser surgery is performed using light amplification of various substances to create heat. The laser beam consists of photons that exit the amplification chamber in specific wavelengths based upon the lasing medium. Commonly available lasing mediums in veterinary medicine include CO2 and diode semiconductors. CO2 lasers are more efficient cutting lasers, and provide minimal collateral damage. CO2 lasers are often considered as "what you see is what you get" lasers in that the tissue damage that is seen at surgery is similar to what will be seen in the post-operative period. Diode lasers are less efficient cutting lasers, and will have up to 3 mm collateral damage to the tissue. CO2 laser energy is delivered through semi-rigid waveguides or articulated arms making them best suited for skin or open surgical techniques. New wave guides may be available to offer minimally invasive delivery in the future. Diode laser energy is delivered through a crystal fiber, allowing introduction into cavities through cannulas or flexible endoscopes (Fig. 9).

Figure 9. Photograph of 50 Watt diode laser with 600 micron fiber.

Flexible Endoscopic Uses [14]

Diode and Nd:YAG lasers are the most commonly used lasers in flexible endoscopy, due in most part to the flexible fiber delivery system. Lasers have been used to perform surgery on ethmoidal hematomas, laryngeal granulation tissue, epiglottic entrapment, rostral displacement of the palatopharyngeal arch, ventriculectomy, (Fig 10, Video 2) guttural pouch tympanities, guttural pouch mycosis, upper airway cysts, choanal atresia, uterine cysts and urolithiasis. It is important to recognize that lasers can cause significant collateral damage and secondary swelling causing severe respiratory distress. Depth perception is dramatically reduced when performing flexible endoscopic surgery when compared to rigid endoscopy.

Figure 10. Photograph of surgical room performing laser ventriculocordectomy with a diode laser.

Video 2 - 6 Mo. Video showing diode laser application for ventriculocordectomy in a horse.

Laparoscopic Uses [15,16]

The diode and Nd:YAG lasers are the most commonly used lasers in laparoscopy for reasons similar to those for flexible endoscopic surgery. Primary uses have been adhesiolysis and ovariectomy. The laser can be used in both contact and non-contact modes. In some cases of ovariectomy, additional methods were used for complete hemostasis including, ligating clips, and linear staples.

Safety Concerns

Monopolar Electrosurgery

It is very important to ensure good contact between the patient and the passive electrode. Poor contact will increase the current density and may lead to skin burns of the patient. In most cases the use of monopolar electrosurgery will require general anesthesia. In minimally invasive surgical procedures, it is difficult to predict where the return of current will occur. Consequently, it is possible for unrecognized tissue burns to occur leading to later tissue necrosis and failure.

Bipolar Electrosurgery

It is important to make sure the jaws of the bipolar instrument are clear of other tissue that is not intended for coagulation.

Ultrasonic Cutting/Coagulating Devices

The blades/instrument tips can get hot so it is important to keep them away from normal tissues when doing surgery.

Radiofrequency Devices

Radiofrequency devices are generally thought to be safe.

Laser Surgery

Laser energy does not always stop at the surface, especially with diode lasers. It is therefore important to monitor the length of time the laser is active on the tissue to make sure that deeper structures are not being negatively affected. Laser safety also involves appropriate goggles and warning signs.