Factors affecting capacitive current diversion with a uterine resectoscope: an in vitro study.

STUDY OBJECTIVE

To evaluate electrosurgical waveform, generator type, and electrode integrity as variables in capacitive induction of current on the external sheath of a resectoscope in open-circuit conditions.

DESIGN

In vitro, laboratory, comparative study (Canadian Task Force classification CII-1).

SETTING

Surgical laboratory.

INSTRUMENTATION

Three ValleyLab radiofrequency (RF) electrosurgical generators (ESU), Force-2, Force-4, and Force-F/X; a resectoscope (Storz 50 series); and rollerball electrodes, both intact and with two types of standard insulation defects (lateral and circumferential) placed in two locations: distally, beyond the end of the telescope, and proximally, beside the distal aspect of the telescope. A Dynatek ESU analyzer was used to record current and wattage on electrodes and the external sheath.

MEASUREMENTS AND MAIN RESULTS

With intact insulation, current was not disproportionately induced on the external sheath of the resectoscope regardless of ESU, power, or waveform. Proximally located electrode insulation defects allowed induction of most of the generator's output to the external sheath when high-voltage modulated outputs were used, and the risk varied somewhat with the ESU. There was no such induction at any power setting or with any insulation defect when low-voltage (cutting) outputs were tested.

CONCLUSION

In the presence of proximal electrode defects, high-voltage currents may contribute to thermal injury to the lower genital tract during RF resectoscopic surgery.