Читать книгу Surgery of Exotic Animals - Группа авторов - Страница 27

Electrosurgery uses high‐frequency alternating current to generate energy. There is an active electrode and an indifferent electrode or ground. With monopolar electrosurgery 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®.