Introduction
Electrosurgery is used in dermatological procedures to stop bleeding (haemostasis) or to destroy abnormal skin growths.
In electrosurgery, high-frequency, alternating electric current at various voltages (200 to 10,000 V) is passed through the skin to generate heat. It requires a power supply and a handpiece with one or more electrodes. The device is controlled using a switch on the handpiece or a foot switch.
Terminology used in electrosurgery
Some of the terminology used to describe electrosurgery is confusing. The aim of the procedure is to perform cauterisation. The word cautery originates from the latin, meaning to brand. It relates to the coagulation or destruction of tissue by heat or a caustic substance.
Electrosurgery (particularly electrocoagulation) is sometimes incorrectly called diathermy, which means ‘dielectrical heat’. Diathermy is produced by rotation of molecular dipoles in high frequency alternating electric field – the effect produced by a microwave oven.
The term electrocautery is most often used in reference to a device in which a direct current is used to heat the cautery probe. As no current flows through the patient, this is not a true form of electrosurgery. It is therefore preferable to use the term thermocautery for these devices.
Electrosurgery includes:
Electrofulguration (results in sparks)
Electrodesiccation (dehydration of superficial tissue)
Electrocoagulation (cause bleeding blood vessels to clot)
Electrosection (cut through tissue)
Thermocautery
Radiofrequency devices (very high frequency, for cutting [>1,500kHz])
Electrosurgery may be monoterminal, monopolar or bipolar.
Monoterminal electrosurgery
Handpiece has single electrode.
Indifferent electrode is not required.
Monopolar electrosurgery
Uses single pointed probe to carry electrical current from power generator to surgical site.
Requires indifferent electrode, typically large metal plate or flexible metalised plastic pad placed on skin distant from surgical site.
Current passes from tip of probe through patient to indifferent electrode and completes circuit by returning to electrosurgical generator.
Bipolar electrosurgery
Uses forceps with both tines connected to power generator: one is active and other is indifferent electrode.
Current runs through tissue grasped by forceps.
Used in patients with implanted cardiac devices such as a pacemaker or defibrillator, to prevent electrical current passing through the device, which might short-circuit or fire inappropriately.
Freestar
Waveforms in electrosurgery
Different waveforms may be generated by the electrosurgery machine for different procedures.
Continuous single, high frequency (>400 V) sine wave used at high heat for cutting / vaporisation leaves a zone of thermal damage. A high pitched sound is heard.
Pulsed or modulated waveforms allow tissue to cool between bursts so that the zone of thermal damage is minimal.
A sine wave turned on and off in a rapid succession (rectified) produces the slower heating process that results in coagulation. A rougher, lower tone is heard due to lower power.
Variable waveforms can be produced to blend cut and coagulation, as power is adjusted in real time depending on tissue impedance.
Electrofulguration and electrodessiccation
Electrofulguration and electrodesiccation are used to destroy superficial lesions that are unlikely to bleed profusely when disturbed, such as viral warts and seborrhoeic keratoses.
Electrofulguration and electrodesiccation use a single electrode to produce high voltage and low amperage current. The current accumulates in the patient but there is minimal tissue damage.
Electrofulguration
Electrofulguration is used to treat skin tags and protruding warty lesions such as seborrhoeic keratoses, viral warts, xanthelasma and dermatosis papulosa nigra.
Electrode is held 1–2 mm from skin surface, and produces spark or electric arc.
This causes superficial tissue dehydration and carbonisation over wide area.
High voltage allows current to overcome resistance of air gap between tissue and electrode tip.
Carbonised epidermis insulates and minimises further damage to the underlying dermis.
Electrodesiccation
Electrodesiccation is used to remove flat seborrhoeic keratoses and lesions under the skin such as syringoma, milia, comedones, sebaceous hyperplasia and molluscum contagiosum.
It can be also used for hair removal and to treat fine facial blood vessels.
Electrode contacts skin directly and heats it up
Results in dehydration of surface and slightly deeper skin
Dry coagulum forms on skin surface.
Treated areas usually heal rapidly with minimal scarring or loss of pigment
Caution
Unless bipolar output is used, the patient must be on an insulated table, as burns may result from current passing between patient and the earth-ground. Electrofulguration and electrodesiccation should only be performed on conscious patients who would feel the burn from an unwanted earth-