ELECTROSURGICAL UNIT

ELECTROCAUTERY

GLOSSARY

• Coagulation: process by which the blood loses its liquidity becoming a gel, to form a clot. This process potentially results in hemostasis, that is, in the cessation of blood loss from a damaged vessel, followed by repair.
• Electrode: device such as a metal plate or a small needle that conducts electricity from an instrument to a patient undergoing treatment or surgery. The electrodes can also carry electrical signals from the muscles, brain, heart, skin or other parts of the body to the recording devices to help diagnose certain conditions.
• Galvanic skin response (GSR): also an electrodermal activity (EDA) and skin conductance (SC), is the measure of the continuity of skin characteristics, for example, conductance, caused by variation Of the sweating of the human body. 
•  Hemostasis: is the ability of an organism to make blood in the liquid state remain in the blood vessels. Hemostasis allows the blood to circulate freely through the vessels and when one of these structures is damaged, it allows the formation of clots to stop the hemorrhage, later repairing the damage and finally dissolving the clot.
• Impedance: Apparent resistance of a circuit equipped with capacity and self inductance to the flow of an alternating electric current, equivalent to the effective resistance when the current is continuous. 
•  Tissue damage: type of injury or injury suffered by the skin. A cut, a bruise or a burn.
• Vascularization: Presence and disposition of the lymphatic blood vessels in a tissue, organ or region of the organism. The way in which the vessels are distributed in a certain organ.

The electrocautery

Also called electric scalpel, surgical unit or HF device, is an electrical device that converts electrical energy into heat to cut, remove or coagulate soft tissues such as meat, thanks to currents that are above 200,000 Hz. 

These frequencies are used because they only produce heat and, if lower frequencies are used, they could interfere with the nervous processes of the body.

The operation of the electrocautery: 

It circulates high frequency current and moderate or high intensity between two electrodes applied to the body. This causes that heat is generated in the place applied and cut (electrosection) or coagulate (electrocoagulation) the tissue.

 The currents can be of two types: direct current or alternating current. In direct current, also called galvanic current, there is a continuous and one-way exchange of electrons between two opposite poles. 

In the alternating current, the exchange of electrons is bidirectional and the magnitude and direction vary cyclically in a sinusoidal manner

Effects of the current on the tissue: 

When the current is applied to human tissue, the following effects occur:

•  Faradic effect: the alternating current of low or medium frequency provoke stimulations in muscles or nerves, something that can produce tetany, premature ventricular fibrillation, or in the worst case, death. The maximum impact occurs when the current is about 100 Hz, and decreases as the frequency increases, because with high frequencies its harmful effect is lost.
•  Electrolytic effect: an ion current is produced in the tissue caused by the electric current. With direct current the positive ions would move towards the negative pole and the negative ions towards the positive pole, causing tissue damage. For this reason direct current is not used. Instead, with the alternating current the ions are displaced permanently changing direction, something that does not cause any damage to human tissue. 
• Thermal effect: it is produced with high frequency alternating current, something that is used in current electrocautery and that avoids the two previous effects.

Types of electrocautery 

The surgical units have two modes of operation: 

• Monopolar mode: It has a large surface electrode, called a return electrode, and a smaller one called an active electrode. The current density that is generated at the contact point of the active electrode is high, which is why a large amount of heat is concentrated in it. 

Active electrode Depending on the shape of this electrode, one effect or another is achieved on the tissue. If the contact surface is smaller, the current density increases, and with it the generation of heat at the contact point, which results in a cut. In contrast, a larger contact surface is used to coagulate the tissue.

Return electrode The return electrodes have a low contact impedance with the skin, have a large surface ranging from 100 to 200 cm² and are very adhesive. It can be of two types: solid, which have a continuous conductive surface, or split, consisting of two pieces to be able to monitor the contact between the electrode and the skin. It should be placed in muscular masses with good vascularization, preventing parts of the body with irregularities and with a lot of bone. In case it is placed preventing a good contact between the electrode and the skin, it can cause an increase in the contact impedance and lead to burns.

•  Bipolar mode:The current is applied between the two tips of an instrument, which are usually clamps or scissors. The current generated between the two tips causes heat to be generated, which is delivered to the fabric. The bipolar electrosurgical units have a lower power density than the monopolar ones, and this means that they can not produce cuts in the tissue (except for some exceptions). With them, hemostasis can be performed using modulated or unmodulated current. It is usually used in endoscopic applications or to seal vessels.

Types of electric wave generated by the electrocautery 

All high-frequency electrosurgery equipment generates an oscillatory wave known as a sine wave. There are two types of waves, damped sine waves and pure sine waves.

• Damped sine wave (damped): A damped sine wave is a waveform that occurs as a group of oscillations, the first oscillation of the group presents the maximum amplitude followed by a train of small waves. This type of wave has a wide effect on living tissue, which results in excessive heat generation and of coagulation. When the wave is more cushioned, the coagulation and tissue destruction effect increases. As a result, the greater the damping in the wave, the greater the hemostasis.

• Sine wave undamped (undamped) or pure An undamped sine wave is a pure, balanced and symmetric wave, in which the amplitude in all oscillations is the same. A pure sine wave produces an effect in the highly focused tissue, which results in tissue separation with very little coagulation. Since it produces very little damage to the tissue or coagulation, there is no significant hemostasis.

• Wave mixture (moderately damped) The most common form used for cutting current it is usually a mixture of a pure sine wave and a damped sine wave. The combination of both waveforms simultaneously allows to cut with hemostasis. With the proper balance in the mix, the cut can be performed with satisfactory hemostasis and minimal tissue damage.