Surgery of Exotic Animals. Группа авторов

the current exits the generator, passes to the active electrode, and concentrates at the tip which contacts the patient. After creating a thermal event at the tip, the current disperses throughout the patient's body, exits through the ground plate, and is carried back to the generator to complete the electrical circuit. Therefore, the patient is within the electrical circuit. If the ground plate only contacts a small area of the patient’s skin burns and subsequent necrosis can result because the current concentrates where it exits the patient. The Surgitron® Dual Frequency 120 (Ellman International, Inc., Hewlett, NY) generates 4.0 MHz current which is in the radio frequency wavelength. Current is received by the indifferent electrode acting as an antenna. Because the current is in the radio frequency, the area of contact between the patient and the ground plate is irrelevant and thermal injury should not occur. This is helpful with small patients where it might be difficult to disperse the current exiting the patient adequately.

      The bipolar electrosurgical forceps are primarily used for hemostasis, but can also be used for tissue dissection resulting in minimal hemorrhage. The same generator is used, but the patient is not within the electrical circuit so the current only affects tissue within the tips of the forceps. Bipolar forceps are most useful near structures that would be adversely affected by the current such as the heart, brain, spinal cord, etc., or for hemostasis deep within body cavities. When using bipolar to dissect or cut tissue, grasp the tissue in the forceps and activate the current while pulling the forceps. The tissue within the tips will be affected by the current providing hemostasis for small vessels within the tissue grasped. In birds, this technique is useful for making a skin incision. Grasp the skin with the forceps and activate the current to create a small defect in the skin. Then insert one limb of the forceps under the skin for 1–2 cm, oppose the other limb of the forceps, activate the current, and withdraw the forceps, thus cutting the skin. Bipolar mode is available on most electrosurgical units including the Surgitron®.

      Vessel Sealing Devices

LigaSure™ (Medtronic, Minneaplis, MN) is a vessel/tissue sealing system that is commonly used in veterinary surgery. The ForceTriad™ (Medtronics, Minneapolis, MN) combines the LigaSure technology with monopolar and bipolar electrosurgery. While the specific technology is proprietary, LigaSureTM is a type of bipolar electrosurgery. The generator senses the electrical impedance of the tissues within the tips and delivers the amount of current needed to melt the elastin and collagen; it then allows the elastin and collagen to re‐form, creating a permanent seal in a single application. It generates less than 1 mm of heat lateral to the seal and is Food and Drug Administration (FDA)‐approved to seal vessels up to 7 mm diameter. A wide range of handpieces are available for open surgical procedures and for minimally invasive surgeries.

      Harmonic Scalpel

      Ethicon® Harmonic Scalpel (Ethicon US, LLC, www.ethicon.com/na) is an ultrasonically activated cutting instrument that converts electrical energy to mechanical energy. The blade vibrates at 55,500 Hz creating heat that coagulates vessels and cuts tissue. Hand pieces are available in various sizes and types for both open surgical procedures and minimally invasive surgery. It is FDA‐approved to seal vessels up to 5 mm diameter and does not create smoke. The tissue is compressed between a Teflon anvil and the vibrating blade. There are two settings, one to seal the tissue and another to cut through the tissue.

      Carbon Dioxide Laser

      The carbon dioxide (CO₂) laser (Aesculight; LuxarCare LLC, Bothell, WA) gained popularity in veterinary surgery in the 1990s and continues to be in common use today. CO₂ lasers produce a beam of intense light at a wavelength that is highly absorbed by water molecules. It cuts tissue when the beam is very focused and coagulates for hemostasis when it is more diffused. The CO₂ laser seals vessels <0.6 mm, so most skin incisions are bloodless with minimal or no bruising. It also seals lymphatic vessels and nerves so there is less swelling and reportedly less pain associated with incisions compared with those made using a scalpel. When used with correct technique, the amount of lateral heat damage is minimal (Harkness et al. 2010); however, when used incorrectly, lasers can cause significant thermal damage.

      In addition to being able to incise skin and other tissues, CO₂ lasers can also be used to fulgurate or destroy tissue, such as a tumor or the tissue bed after a tumor has been removed in an effort to eliminate residual microscopic disease. Use a high‐power setting and keep the tip as close to the tissue as possible when cutting tissue. Do not touch the tip to the tissue. If there is hemorrhage, move the tip farther from the tissue, which will diffuse the beam and coagulate vessels. Use a smaller tip to create a small spot of light which will then cut better with less collateral heat. A wider tip will not cut as well and will cause more heat damage, but will also control hemorrhage better by coagulating vessels. Proper safety training for all personnel is important when using surgical lasers.

      Magnification

      Magnification is a vital part of efficiently performing surgery on small exotic animals, but it is also useful for delicate procedures in any size animal (see Chapter 3).

      Focal Light

      Overhead surgery lights are not adequate for surgery in small exotic animals and are becoming obsolete being replaced by head‐mounted focal light sources that illuminate whereever the surgeon is looking, including deep into body cavities. These lights illuminate a smaller area allowing better visualization of the tissues. Inexpensive head‐mounted cool focal lights are available with or without magnifying loupes from many sources (LED Headlight; MDS, Inc., Brandon, FL). SurgiTel loupes (General Scientific Corporation, Inc., Ann Arbor, MI) are available with different light options that mount onto the frame to illuminate the surgeon's field of view.

      General Scientific Corporation, Inc., also offers SurgiCam HD, a head‐mounted digital video camera with 3× magnification. The procedure can be viewed on a monitor, and images, and videos can be captured onto a computer.

      Retractors

In the past, spring‐loaded eyelid retractors have been recommended for abdominal wall retractors in small patients. The tension cannot be adjusted and is often too much for small patients. Heiss and Alm Self‐Retaining Retractors work well as abdominal and tissue retractors in companion exotic animals (Figure 1.5). The Lone Star™ Retractor (Veterinary Specialty Products, Inc., Mission, KS) consists of a plastic frame and silastic bands with tissue hooks on the ends (stays) (Figure 1.6). Be sure to look for the models with all components that are fully autoclavable. Place the stay hooks in the tissue and using an appropriate amount of tension, pull and insert the silastic bands into the notches of the frame to retract tissue. These retractors are very versatile and have a wide range of applications.

Instrumentation

In the past, many surgeons have turned to using ophthalmic instruments for surgery in small exotic animals; however, they are not well suited for this purpose. Being made for surgery on a superficial structure, the eye, they are short making them more difficult to control and to manipulate tissues deep in a body cavity. Microsurgical instruments are manufactured so they are of a standard length and only the tips are miniaturized (Bennett 2009) (see Chapter 3). They are long enough for the instrument to balance in the hand while the tips extend beyond the surgeon's hand into the patient's body cavity (Figure 1.7). They should be counterbalanced to minimize hand fatigue. Round handles are recommended because the instruments should be rolled between the thumb and first two fingers rather than using wrist action. Having round handles is most important for needle holders because the curved needle has