Electrosurgery is a common surgical technique which involves the use of an alternating electrical current to desiccate, coagulate and vaporise tissues1. Despite its common nature, it is still the case that many surgeons who routinely perform electrosurgery misunderstand the physical principles that underpin it2,3. This article aims to explain electrosurgery in terms of exactly what it is, how it works, and how reliable electrical connectors can render it far safer.
The first successful operation to remove a previously inoperable tumour from a patient’s head was carried out on the 26th October 1926. This operation was carried out by one Dr William T Bovie, despite the fact that Dr Bovie’s PhD had been acquired in plant physiology and thus he was not even a medical doctor. Despite this, the apparatus used by Dr Bovie, a machine of his own invention, would serve to transform modern surgery. Bovie had invented electrosurgery: a surgical technique in which a high-frequency electric current is used to cut and cauterize tissue. By the 21 century electrosurgery had arguably become the most common surgical technique in use, with surgeons suggesting its involvement in up to 80% of all surgeries5.
What Does Electrosurgery Involve?
There exist two alternate forms of operation within electrosurgery – monopolar and bipolar. The more common, monopolar, involves the incorporation of the entire body of the patient into an electrical circuit using two electrodes. One of these electrodes, the passive electrode, which is normally a pad or a mat, is adhered to the patient in such a manner as to ensure as large a contact area as possible. It is with the other electrode that the surgeon operates, and this, the active electrode, therefore takes the form of a probe in their hand. A high frequency alternating voltage is created between the two electrodes such that, when the probe is brought into contact with the patient, an electrical current flows between the two electrodes. This current is an alternating current in the radio frequency, alternating between 100,000 and 5,000,000 times per second (100kHz – 5MHz)
Through this process, heating of the cells around the probe occurs. This heating occurs in two different ways, the first of which is ohmic heating. Ohmic heating, similar to that occurring in the filament of a lightbulb, refers to heating which occurs as the current of electrons causes the cells to heat up. Dielectric heating refers to that more similar to the principles of microwave cooking; polar molecules such as water are caused to vibrate by the current and this generates heat.
Current, measured in Amperes, describes the number of electrons flowing through something each second. The amount of current flowing through a given unit of area, otherwise termed the current density, is the determining factor in the controlling the heat applied during electrosurgery. As a result, heat is largely confined to the area around the point of the electrode where the current density is highest. The current density drops off extremely rapidly moving away from the tip of the electrode, therefore heat effects even small distances away from the probe are immeasurable. The contact area of the passive electrode is maximized so as to minimise the current density at its surface.
Bipolar electrosurgery works via similar principles, however in bipolar electrosurgery both electrodes take the form of small handheld probes meaning that the current only flows between the small volume of tissue between them.
As mentioned, the amount of heat applied during electrosurgery can be closely controlled. This renders electrosurgery an extremely versatile technique which can be used to carry out different procedures simply by altering the heat applied. High temperatures can be used to generate rapid heating of liquids within cells which causes them to spontaneously evaporate, bursting the cell in the process. This technique can be used to expunge or cut tissues.
Alternatively, slower heating can be used to cauterize or coagulate tissues through the denaturing of proteins. The extent of heating can be controlled through the varying of the voltage signal. Specifically this is controlled by the regularity with which current is applied; constantly applying current will produce high heats, applying current in pulses allows for reductions in heating. This fine control allows for the extant of heating to be placed anywhere on a sliding scale from cutting to dessication of tissue6. Electrosurgery is, therefore, particularly important in surgeries of highly vascularized areas, given that the area around the incision can be automatically cauterized.
High-Performance Connectors for Electrosurgical Safety
It stands to reason that the precise and reliable control of current in electrosurgery is vital for its safety and effectiveness. This is, however, not easily done. Not only is the current drastically affected by the size and positioning of the probe, but also by the differing resistance of various tissues within the body. Furthermore, carbonized tissue known as eschar can build up on the probe and this serves to further increase their resistance over time.
Electrosurgical generators must compensate for these issues, resulting in complex systems combining multiple signal generators so as to produce the range of signals and power outputs required for different effect. These systems also allow for both monopolar and bipolar modalities7,8.
The complexity of these electrosurgical systems results in a need for reliable electrical connectors. Stäubli, a Swiss electrical connector company highly experienced in the medical field, offers a wide range of high-performance connectors for use in electrosurgery9. Their connectors are manufactured to the highest quality, thus ensuring their dependability within a field in which any small unwanted deviation could have serious implications.
The connectors are sterilisable and make use of proprietary MULTILAM technology to achieve low and well-defined contact resistances, enabling safe and precise application of current. It stands to reason that reliability within the medical field is crucial, and Stäubli’s connectors are manufactured with this in mind. With the ability to perform up to 1,000,000 mating cycles, Staubli’s connectors are built to withstand all the pressures of the operating room, thus enabling surgeons to focus on the job at hand.
References and Further Reading
- Electrosurgical units - how they work and how to use them safely. Cordero, I. Community eye Heal. 28, 15–6 (2015).
- Common Myths About Electrosurgery. Zinder, D. J. Otolaryngol. - Head Neck Surg. 123, 450–455 (2000).
- Surgeons don’t know what they don’t know about the safe use of energy in surgery. Feldman, L. S. et al. Surg. Endosc. 26, 2735–2739 (2012).
- Michigan biographical dictionary. (Somerset Pub, 1998).
- Aaron Medical - Understanding Electrosurgery. Genard McCauley. Available at: https://web.archive.org/web/20060523223749/http://www.aaronmed.com/Images/UNDERSTANDINGLIT.pdf. (Accessed: 5th March 2018)
- Principles of Electrosurgery.
- VIO 300 D - Erbe USA, Incorporated. Available at: https://us.erbe-med.com/us-en/products/electrosurgery/vio-300-d/. (Accessed: 6th March 2018)
- Bovie OR|PRO 300 Electrosurgical Generator - Bovie Medical. Available at: http://www.boviemedical.com/orpro/. (Accessed: 6th March 2018)
- Modular connectors. Available at: https://www.staubli.com/en-gb/connectors/electrical-connectors/modularconnectors/. (Accessed: 6th March 2018)