Mechanisms of thermal injury to the lower genital tract with radiofrequency resectoscopic surgery

Study objectiveIdentification of mechanisms of thermal injury to the lower genital tract during radiofrequency (RF) resectoscopic surgery.DesignLaboratory comparative study using uterovaginal tissue models.SettingUniversity surgical laboratory.PatientsNo patients involved.InterventionsA tissue model was created to simulate the uterus, contiguous posterior vaginal wall, and the introitus. Instrumentation included a RF electrosurgical generator; a continuous-flow resectoscope; and rollerball electrodes, both intact and with insulation defects created in a standardized fashion. The resectoscope was serially activated, varying electrode insulation defects and RF waveforms and wattage, both in open-circuit conditions, with or without cervical contact, and with variable amounts of the external sheath within the simulated cervical canal. The cervix was either overdilated or minimally dilated so that the surrogate cervical tissue was snug to the external sheath. After activation of the generator, the external sheath was brought into contact with the proximal vagina and perineum, any visible arcing was noted, and tissue effects were visually graded according to a zero-to-three scale.Measurements and main resultsWhen the resectoscope was in contact with the cervix, the prerequisites for vaginal injury included cervical overdilation, a proximal electrode insulation defect, and less than 2 cm of the external sheath in the canal. There was greater risk with larger electrode insulation defects located beside the telescope, and there was a greater degree of coupling and injury with high voltage outputs.ConclusionThe incidence of vaginal and perineal burns associated with unipolar RF resectoscopes can likely be minimized by careful attention to technique.