G A Vilos1, S McCulloch, P Borg, W Zheng, J Denstedt. 1. Department of Obstetrics and Gynecology, St. Joseph's Health Centre, 268 Grosvenor Street, London, Ontario, Canada N6A 4V2.
Abstract
STUDY OBJECTIVE: To test the hypothesis that electrical burns of the genital tract and urethral strictures after hysteroscopic endometrial ablation and transurethral prostatectomy, respectively, are related to capacitive coupling and/or stray currents induced by intact and defective electrodes and/or resectoscopes. DESIGN: Basic in vitro measurements. SETTING: Laboratory. MATERIALS: Porcine muscle and liver, resectoscope, electrosurgical unit (ESU), and ESU analyzer. INTERVENTION: We measured electrical coagulation and cutting currents of rollerball and loop electrodes and the external sheath of the resectoscope from 80 to 200 W through a resistance load of 200 and 250 ohms, using intact electrodes and conditions simulating potential insulation defects along the shaft of the electrodes. MEASUREMENTS AND MAIN RESULTS: Approximately 20% to 25% of current was induced by capacitive coupling to the resectoscope sheath. Touching porcine muscle or liver with small areas of the sheath while the generator was activated resulted in superficial tissue burn. Surrounding large segments of the sheath with tissue did not result in visible burns, indicating that under normal conditions the sheath acts as a dispersive electrode. Defective insulation of distal segments of the electrodes resulted in 100% transfer of current to the sheath and caused extensive electrical burns of tissue in contact with the sheath. CONCLUSIONS: Capacitive coupled currents induced by intact resectoscopes and electrodes may cause thermal injury to surrounding tissue during prolonged resectoscopic surgery. Stray currents from defective insulation of the electrodes result in direct coupling of current to the telescope and sheath and cause extensive burns of surrounding tissues in contact with the sheath.
STUDY OBJECTIVE: To test the hypothesis that electrical burns of the genital tract and urethral strictures after hysteroscopic endometrial ablation and transurethral prostatectomy, respectively, are related to capacitive coupling and/or stray currents induced by intact and defective electrodes and/or resectoscopes. DESIGN: Basic in vitro measurements. SETTING: Laboratory. MATERIALS: Porcine muscle and liver, resectoscope, electrosurgical unit (ESU), and ESU analyzer. INTERVENTION: We measured electrical coagulation and cutting currents of rollerball and loop electrodes and the external sheath of the resectoscope from 80 to 200 W through a resistance load of 200 and 250 ohms, using intact electrodes and conditions simulating potential insulation defects along the shaft of the electrodes. MEASUREMENTS AND MAIN RESULTS: Approximately 20% to 25% of current was induced by capacitive coupling to the resectoscope sheath. Touching porcine muscle or liver with small areas of the sheath while the generator was activated resulted in superficial tissue burn. Surrounding large segments of the sheath with tissue did not result in visible burns, indicating that under normal conditions the sheath acts as a dispersive electrode. Defective insulation of distal segments of the electrodes resulted in 100% transfer of current to the sheath and caused extensive electrical burns of tissue in contact with the sheath. CONCLUSIONS: Capacitive coupled currents induced by intact resectoscopes and electrodes may cause thermal injury to surrounding tissue during prolonged resectoscopic surgery. Stray currents from defective insulation of the electrodes result in direct coupling of current to the telescope and sheath and cause extensive burns of surrounding tissues in contact with the sheath.