Electro-surgery consists of the application of electrical current passing through tissue. Because tissue forms a resistance, heat is generated, which ensures a coagulation. An alternating current with a frequency above 300 kHz will not result in muscle contractions, and it is therefore suitable for electro-surgery. Depending on the signal waveform and voltage, different effects varying from purely cutting to purely coagulation can be achieved. There is monopolar and bipolar diathermia. A monopolar instrument has a small contact surface, resulting in a high energy density at the tissue level with subsequently a high temperature for cutting and/or coagulation. The other electrode is a broad contact diathermy plate. Comparatively, a bipolar instrument contains two electrodes united in one device, with an active electrode and a return electrode. The electro current is confined to a direct path between the electrodes. Other forms of electro-surgery include ultrasonic electro-surgery and vessel sealing techniques, which produce heat by rapid mechanical vibrations. Laparoscopic and robotic instruments are usually long and must be completely isolated to prevent unintended damage to adjacent tissue by current conduction. Only a small active tip of the instrument should be bare for safe electro-surgery. The minimally invasive surgeon should be familiar with electro-surgery and its risks. The background and risks of electro-surgery in minimal invasive procedures are summarized in this chapter.
