Electrosurgery for the Gynaecologist: Cutting and Coagulating with One Instrument and One Setting

The relationship between tissue effects, intensity (I), and voltage (V) of a high-frequency alternative current seems well known. However, the translation of the settings of the electrosurgical unit and their use during surgery seems not to be unanimously understood by all surgeons. This results in many variations of surgical technique and plenty of specific questions asked during live surgery. Above 200 V, the heat of the sparks results in the explosion of superficial cells and a cutting effect. With higher voltages, the associated coagulation is increasing. Voltage and amount of energy (Watt=I*V) are independent since a similar amount of energy can be obtained with a continuous current or an intermittent current half the time and a double voltage. Below 200 V, tissue is heated until the steam from boiling tissue stops the current. Therefore, slower heating with less energy or a larger contact area permits deeper coagulation. The maximal output (W) of the electrosurgical unit results in versatility of use besides being a safety measure. The current intensity increases with the area of contact. Therefore, when I*V exceeds the preset output, V has to drop. A limited maximal output thus permits using the same instrument for non-contact cutting with >200V and sparks and coagulation when the contact area is much larger. In conclusion, the tissue effects of electrosurgery vary with the device’s voltage setting (often indicated as force) and the maximal output. The sur-geon’s choice to cut or coagulate by changing the contact area adds versatility.