All You Need-to-Know About Electro-Surgical Units

What is the Electrosurgical unit? 

An Electro Surgical Unit makes use of radiofrequency electrical current to cut, coagulate or destroy tissue. An electrosurgical unit is an instrument used in surgeries, where a high-frequency electric current is used to cut and coagulate tissues. 

During surgery, there is significant blood loss as the tissues and blood vessels are cut resulting in bleeding. Thus the use of an electrosurgical unit reduces bleeding and loss of blood. 

ESU circuit design is made to provide the correct electrical waveforms to be delivered to the site of surgery to coagulate blood vessels thus cutting tissues in a safe and smooth manner. A Surgeon may use the electrosurgery unit instead of, or in addition to a conventional scalpel. 

When used properly, the electrosurgical unit has a less damaging effect on tissues than that of a scalpel and allows for a safe way to stop bleeding. 

These electrosurgical equipment uses an electric current of an oscillating frequency of nearly 500 kHz to cut and coagulate tissues. When the electrical current is passed through the tissue, it gets heated up resulting in water evaporation which ultimately destroys cells. Thus, the process of cutting, clotting, dehydrating blood cells and tissues is achieved with minimal blood loss.

An alternating current enters into the patient’s that is part of the closed circuit consisting of a generator, an active electrode, patient, and the patient's return electrode.

A transformer allows generating a high voltage to let the passage of high electric current that corresponds to the power required for surgical purposes.

The voltage on the electrode is between 1000 to 10000 Volts peak to peak. There are mainly three modes of functioning for the electronic surgical unit: cutting, coagulation, and blended mode.

Modes Of Operation Of an ESU 

Cutting mode

The electric current divides tissues without coagulation. Then a lower voltage is required to achieve tissue vaporization. This requires 50 watts in the case of bipolar cut and around 150-300 watts in the case of a monopolar cut. Such mode is achieved with a continuous sinusoidal waveform.

Coagulation Mode

Blood clotting is achieved by burning the ends of vessels to control bleeding. This would require 80 watts in bipolar cut and 40-80 watts in the case of a monopolar cut. Coagulation mode is achieved primarily with a series of sinusoidal wave packets.

Modes of functioning

There are two modes; Monopolar and Bipolar. The main difference between the two modes is the method by which an electric current enters and exits human tissues.

Monopolar

Current flows through the patient to a patient return electrode.

The active electrode is in the wound and a patient return electrode is attached to the patient.

The high current density in the area of active the electrode achieves either tissue cutting or tissue coagulation.

The low current density under the dispersive electrode causes no tissue damage which is used for cutting and coagulation respectively.

Monopolar Mode

It is the sparking of tissues leading to coagulation. As shown in the figure below the waveform is of low frequency with a delay, this aids in increasing the surface area of the electrode. There is no tissue-electrode contact; rather, the voltage is raised in order to incite a spark between electrodes in order to coagulate tissues in between. 

Bipolar Mode

Bipolar mode

Active electrode and return electrode functions at the site of surgery(Forceps tines). Only the tissue grasped is included in the electrical circuit. (Current passes only between tips of forceps). Thus the patient does not need a return "dispersive" electrode. This mode is mainly used for coagulation.

Modes of Operation

There are three modes of operation and can be produced on command, dependent upon the waveform issued by the ESU.

Cutting Mode

A cutting mode in ESU

A high-frequency alternating current yield smooth, rapid cuts that evoke little to no homeostasis. The current stimulates cells to swell and explode. 

Coagulation Mode

Coagulation mode in ESU

It is the sparking of tissues leading to coagulation. There is no tissue-electrode contact; rather, voltage is raised in order to incite a spark between electrodes in order to coagulate the tissue in between. 

Blended Mode

A blended mode in ESU

It is a combined effect of cutting and coagulating; dampened waveform that produces some homeostasis during cutting.

Machine Block Diagram of a Typical ESU Block Diagram

ESU Block Diagram 

If you are looking for more in-depth information you might want to visit the link provided as it contains more useful information related to ESU.

ESU Accessories

Monopole active electrodes

ESU: Monopolar Electrodes 

Cut or coagulate control is from the pencil-like electrode or from a footswitch. The needle is disposable and changeable depending on the surface area required.

Bipolar Electrode

ESU: Bipolar Electrodes 

 Control of the coagulation is by a footswitch. So when activating the bipolar electrode, the monopole settings automatically shuts-off or are bypassed.

Dispersive Electrode

ESU: Dispersive / Grounding electrode

As mentioned before the dispersive electrodes are of very high importance as they are responsible for returning the current passing through the patient body safely back to the machine.

 Foot Switch 

ESU: Foot Switch 

That is how an ESU might look like from the inside. For any ideas and comments please don't hesitate to write them in the comments section. 

We highly recommend that you visit and sign up for advantage training and to be able to undergo training courses provided by Fluke Biomedical especially the one related to ESU session, you will be eligible for a system-generated certificate once you pass any course. 

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