With the advent of new technologies, it is crucial to understand how instruments work to fully be able to utilize them and prevent injury. Training in equipment use varies but some basic facts should be familiar to every user.
Physicist William T. Bovie developed the first electrosurgical unit in 1920, and Dr. Harvey W. Cushing, the founder of modern neurosurgery, introduced it in the clinical practice and used it to maintain hemostasis during brain surgery.
The purpose of an electrosurgical unit (ESU) is to cut or to control bleed by causing coagulation. The term electrosurgery is often confused with electrocautery:
- In electrocautery, electrical current is used to heat up a metal probe, which resists the flow of the current and becomes hot. It is then applied to the target tissue. The current doesn’t enter the patient’s body.
- In electrosurgery, high frequency electrical current flows in a closed circuit using 2 electrodes. Here the target tissue offers resistance to passage of the current and the electrical energy is converted to heat. (Resection using combination cut and coag)
All electrosurgical units are bipolar, whereas the instrumentation can be either monopolar or bipolar and depends on the location of the second electrode.
- In monopolar instrumentation (argon plasma coagulation, hot snare), the patient is included in the circuit and the current enters the patient’s body. The circuit is composed of the electrosurgical generator, the active electrode, the patient and the return electrodes or the so-called grounding pad.
- In bipolar instrumentation (the tips of a pair forceps, graspers, or scissors), the current is restricted to the immediate vicinity of the two active electrodes. There is no electrical current that flows through the patient; the only part of the patient that is exposed to the current is what is between the two electrodes, so there is no need for a grounding pad.
Even with the new ESU, we continue to hear the expression “grounding the patient”. That was done in the past with the older ESU; when we depended on the ground itself to complete the circuit (both the machine and the patient were grounded). Now, the new machines are closed circuits with a return electrode. We moved from the ground reference to isolated units.
References:
J Am Board Fam Practice 1991;4:419-26
JSLS 2012;16:130-139
JACS 2006;202:520-530