The diagnosis of direct thermal visceral injury may be difficult. If unintended activation of the electrode occurs, nearby intraperitoneal structures should be evaluated carefully. The appearance can be affected by several factors, including the output of the generator, the type of electrode, its proximity to tissue, and the duration of activation. The diagnosis of visceral thermal injury is often delayed until signs and symptoms of fistula or peritonitis secondary to perforation appear. Because these complications may not manifest until 2 to 10 days after surgery, patients should be advised to report any postoperative fever or increasing abdominal pain.
Thermal injury to the bowel, bladder, or ureter that is recognized at the time of laparoscopy should be managed immediately, taking into consideration the potential extent of the zone of coagulative necrosis (114). Incisions made with the focused energy from a pointed electrode are associated with a minimal amount of surrounding thermal injury. Prolonged or even transient contact with a relatively large-caliber electrode may produce a zone of thermal necrosis that may be much larger than visually apparent. In such cases, wide excision or resection of up to several centimeters of bowel may be necessary. The choice of route of access for any required surgical repairs depends in part on the nature of the injury and on the skills and training of the surgeon.
The incidence of unintended activation injuries can be reduced if the surgeon is always in direct control of electrode activation and if all electrosurgical hand instruments are removed from the peritoneal cavity when not in use. When removed from the peritoneal cavity, the instruments should be detached from the electrosurgical generator, or they should be stored in an insulated pouch near the operative field. These measures prevent damage to the patient’s skin if the electrode is accidentally activated.
Current diversion occurs when the radiofrequency circuit follows an unintended path between the active electrode and the electrosurgical generator. This may occur with insulation defects, direct coupling, or capacitative coupling. In older, grounded systems, unlikely to be in use, current can be diverted if any part of the patient’s body touches a conductive and grounded object. In any of these situations, if the power density becomes high enough, unintended and severe thermal injury can result.
If the insulation coating the shaft of a monopolar electrosurgical instrument becomes defective, it can allow current diversion to adjacent tissue, most often bowel, potentially resulting in significant injury. This happens in part because such defects create a zone of high current density (Fig. 23.20A). Therefore, the instruments should be examined before each procedure to detect worn or obviously defective insulation. When using monopolar laparoscopic instruments, the shaft of the device should be kept away from vital structures and, if possible, totally visible in the operative field.
Direct coupling occurs when an activated electrode touches and energizes another uninsulated metal conductor such as a laparoscope, cannula, or other instrument. Direct coupling is often used for hemostasis when a grasping instrument is used to occlude a blood vessel while a separate activated electrode is used to provide the energy for desiccation and coagulation. If this occurs while the noninsulated device rests against structures such as bowel or the urinary tract, injury may occur (Fig. 23.20B). The risk of direct coupling can be reduced by eliminating the simultaneous use of noninsulated and monopolar instruments. The surgeon should visually confirm that there is no contact with other conductive instruments before activating a monopolar instrument.