Electrosurgical Generators (ESU)

Electrosurgery — is a medical procedure that involves the destruction of biological tissue using alternating electric current with a frequency of 200 kHz to 5.5 MHz. The basic principle of electrosurgery is the conversion of high-frequency current into thermal energy.

The operating principle of ESU devices

To understand the basics of electrosurgery, it is necessary to know some terms:

1. Direct current is an electric current that does not change in magnitude or direction over time. This current is obtained from chemical power elements: galvanic cells (batteries), accumulators, etc.

2. Alternating current is an electric current that changes in magnitude and usually in direction over time in an electrical circuit. We get this current from a household outlet, and it was the ability to change the characteristics of the current that made it possible to discover electrosurgery, a method that is essential to most of the surgeries today.

An electric circuit is a set of devices and elements designed for the flow of electric current, the electromagnetic processes in which can be described using the concepts of "current" and "voltage". When an electric circuit is closed, electric current can flow through it. When an electric circuit is not closed, electric current does not flow through it.

Characteristics of Current and Circuit

1. Current is the amount of electricity passing through a conductor per unit of time (measured in Amperes)

2. Power is the amount of work per unit of time (measured in Watts)

3. Frequency (the characteristic is applicable to alternating current) is the number of periods - repeated changes in current and voltage - per unit of time (measured in Hertz)

4. Voltage is the work of an electric field to transfer a certain charge from point A to point B (measured in Volts)

5. Electrical resistance is a physical quantity that characterizes the properties of a conductor to impede the passage of electric current (measured in Ohm)

Electric current in surgery

The current "From the socket" has a frequency of 60 Hz. Current of this frequency is potentially lethal for humans: its passage through the human body causes pain, muscle spasm (including ventricular fibrillation), burns, stimulation of nerve cells. Electrosurgical devices use high-frequency current (500 kHz - 33 MHz), this allows to bypass the effect of neuromuscular stimulation, "trick" the receptors of the human body and perform surgical manipulations using electric current.

The first electrosurgical device was used back in 1924 by the American neurosurgeon Harvey Cushing.

Monopolar and bipolar modes of electrosurgical devices

There are two types of electrical circuits in surgery, commonly referred to as monopolar circuits and bipolar circuits.

In monopolar electrosurgery, current flows through the patient's body from the "active" electrode, which the surgeon uses, to the "neutral" or "passive" electrode, which picks up the charge and thus completes the circuit. From a circuit perspective, both electrodes are the same. However, the working electrode is made thin, sometimes pointed, its working area is minimal, and maximum power is concentrated on it. The "neutral" electrode, on the other hand, has the largest possible area in order to dissipate the generated heat and minimize thermal damage on the side of attachment of this electrode. Monopolar electrosurgery is characterised by fast incisions, high energy, availability in almost every operating room, and low cost of consumables. For the safety of monopolar interventions, a secure fit of the return electrode to the patient's body is critical.

In bipolar surgery, both electrodes are located on a single device called a "bipolar electrode," and the current flows from one end of the electrode to the other, affecting only the area of human tissue that is located between these electrodes. The most obvious example of a bipolar electrode is bipolar tweezers, in which the current flows between the branches. The effect of bipolar is more targeted and precise, while the entire patient's body is not included in the electrical circuit, but only a fragment of tissue located between the branches. Bipolar surgery is often used by neurosurgeons, ophthalmologists - specialists who have to work precisely with nerves or small vessels.

Coagulation types

Argon-assisted electrosurgery

A separate front among electrosurgical devices are generators for argon plasma electrosurgery. Such systems add a circuit with an inert gas supply - argon - to the electrode. Argon has proven to be an excellent conductor for an electric signal, effectively and evenly dispersing it over a large area. Electric energy ionizes the gas flow and instantly interacts with tissues through argon. The clinical effect is higher quality than from direct contact with tissue or by transmitting an electric charge through air.

Also, when coagulating with an argon plasma tip, blood is literally "blown out" of the affected area, thus forming a higher quality and more reliable scab.

Argon-assisted coagulation

It is popular in parenchymatous organ surgery — lungs, liver — when there is a need to coagulate large areas penetrated by blood vessels. It is also known that argon plasma generators are often used in orthopedics — when preparing a place for a hip joint prosthesis, the acetabulum is drilled with special reamers, which leads to extensive bleeding. Argon-assisted electrosurgery allows for effective coagulation of such areas.

Electrosurgical Generators. Comparison of CONMED devices

For electrosurgical effects, special medical devices are used: electrosurgical generators. They are also called "ESUs" (Electrosurgical units), "coagulators", "diathermic devices" or "cauters".

What unites them all is that, working from a socket, they produce high-frequency electric signal, can change the parameters of this signal in a wide range in order to produce different working cycles and produce different clinical effects.

Electrosurgical generators can differ in power, speed, number of modes, availability of special operating modes, as well as appearance, controls, standards for connecting consumables, and more.

An electrosurgical generator is a source of an electric signal. Electrodes are connected to it, which the doctor works with. Pedals are connected to it, which can be used as controls. If this is an argon plasma system, then a gas source - argon - is also connected to the generator.

The standards for connecting disposable accessories are well-recognized, there are several of them and there are adapters between different standards. For example, ConMed electrosurgical generators are compatible with mono- and bipolar electrodes of the Valleylab standard. The same standard is used today by BOWA, Bovie and other brands.

CONMED Electrosurgical Generators

CONMED offers several models of 300-watt coagulators

We recommend checking out the basic model System 2450

This is a universal, affordable, powerful device with the highest level of electrical safety and the highest speed: the generator measures the resistance of the tissues affected by the electrode 420,000 times per second.

CONMED System 2450 has two modes of monopolar cutting: Cut and Blend - a mixture of cutting and coagulation. The Blend mode, in turn, can have two varieties.

This coagulator can operate in two modes of monopolar coagulation and in two modes of bipolar coagulation. The maximum power in bipolar mode is 70 watts

The System 2450 coagulator is equipped with two monopolar connectors and can simultaneously work with two monopolar electrodes.

The generator controls are extremely simple and clear, the control panel is oriented upward for ease of manipulation by medical personnel.

System 2450 is a classic, high-quality, reliable and inexpensive American EHF generator

CONMED System 5000 is the next model in the manufacturer's hierarchy. This ESU has more operating modes and is capable of outputting higher power when working with bipolar electrodes.

Special modes and features of CONMED System 5000:

Fluids — a mode for working in a liquid environment. When the electrode is activated, the generator produces a more powerful charge than in the normal mode so that the charge can “break through” the saline solution and reach the target faster.
Lap mode — a mode for laparoscopy. In this mode, the generator limits the maximum voltage supplied to the electrode to avoid the accumulation of leakage currents or unwanted burns associated with a limited field of vision and possible damage to the braid of laparoscopic instruments.
Pinpoint coag — gentle contact coagulation under low voltage
Monopolar pulse cut — a special “pulsating” work cycle for precision dissection. Work is performed for 70 ms every 600 ms.
Monopolar pulse coag — a special “pulsating” work cycle for precision hemostasis. Can be activated in Spray and Standard modes. The electric charge is supplied for 2.5 ms every 5 ms. The clinical effect is more gentle, and the accuracy of the work is increased.
Ability to save up to 9 user settings of operating modes
Ability to reassign the buttons of the electrode pencil to adjust the power of exposure directly from the electrode

CONMED System 5000 is equipped with two monopolar connectors of the Valleylab standard, one bipolar connector 28.5 mm, one universal connector for connecting pedal-activated monopolar accessories

CONMED System 5000 can be supplied in the "system" version on a special trolley with two metal baskets for consumables, cables, pedals. Pedals are also included in the "system" version

CONMED HelixAR — 300 W coagulator with the additional feature of argon-assisted coagulation. On the one hand, this device completely replicates the functionality of the System 5000 model, and on the other hand, it has a special connector for connecting electrodes for argon-assisted coagulation. The HelixAR generator is supplied on a specialized cart equipped with space for two argon cylinders and a surgical smoke evacuator.