The tissue and thermal effects of electrosurgery in the uterine cavity

A brief outline of the physics associated with the production of electrosurgical wave-forms has been described. The conversion of electrical to thermal energy in electrosurgical techniques has demonstrable tissue and thermal actions and these were discussed in greater detail. In vitro electroresection was associated with a narrow ZTN underlying the electrode that did not vary with power output, but was related to duration of exposure. For blend 2 cutting output the mean ZTN ranged from 0.97 to 1.40 mm for a single sweep of the electrode. With longer time increments this ZTN increased to 2.20 mm. Coagulation by desiccation, in vitro, resulted in a depth of destruction of 3.24-3.49 mm that did not vary with power output or duration of exposure. Fulguration only achieved a depth of destruction of up to 1.78 mm that was related to time. This confined-ZTN in the fulguration mode was felt to be too narrow to destroy the deeply seated myometrial gland elements. Thermal transmission through blocks of human uterine tissue, in vitro, has been demonstrated. Resection generated a maximum rise of 5.8 degrees C at 12 mm from the electrode, with desiccation, a maximum of 4.0 degrees C. It was also demonstrated that resection and desiccation have differing thermal profiles, the latter being more confined in nature. Both power output and duration of exposure in resection are important factors, in vitro, with regard to heat generation. Duration of exposure during desiccation is important in terms of heat generation, but not power output. Repetitive electrosurgical insults have a cumulative effect on the thermal profile in vitro. The underlying damage to uterine tissue during electrosurgery in vivo has been established. In electroresection the zone of thermal necrosis was related to duration of exposure, whereas in electrodesiccation the damage appeared confined, self-limiting, and not time-related. The lack of clinically significant demonstrable thermal transmission through the uterus was important. However, excessively prolonged application of electrosurgical energy (greater than 5 seconds) in the narrow regions of the uterus, especially with electroresection, could still be potentially dangerous. The use of the desiccation mode in the cornual regions is recommended for three reasons; the loop electrode has greater potential for perforation in this thin region (because of its diameter); the desiccating mode appeared to have a clearly defined, consistent ZTN that did not alter appreciably; and the thermal imaging of the ball electrode, in vitro, demonstrated the more confined nature of its thermal profile compared to the loop electrode.(ABSTRACT TRUNCATED AT 400 WORDS)