Capacitive coupling: a comparison of measurements in four uterine resectoscopes

To compare electrosurgical waveform and electrode integrity as variables in the capacitive induction of current to the external sheath of four different resectoscopes.

Laboratory comparative study.

Surgical laboratory.

Valleylab Force FX and Force 4 radiofrequency (RF) electrosurgical units (ESUs); resectoscopes from four manufacturers; and rollerball electrodes, both intact and with standardized insulation defects. The ESU was fired over a working range of high- and low-voltage outputs in open circuit conditions, and current and wattage were measured and recorded from both the electrodes and the external sheath.

With intact insulation, relatively little current was measurable on the external sheath of any of the resectoscopes regardless of the power or waveform. However, with high-voltage outputs, most proximal insulation defects, and some distal defects, a large proportion of ESU output was measured on the external sheath. There were no such findings with any resectoscope, at any power setting or with any insulation defect, with low-voltage ("cutting") outputs.

These results confirm that high-voltage outputs may present a greater risk for current diversion to the external sheath of any of the monopolar resectoscopes tested and that this could contribute to the risk of lower genital tract injury during RF resectoscopic surgery.