Principles of Electro- and Laser Surgery

The use of electrosurgery in hysteroscopy began back in the 1970s, when tube cautery was used for the purpose of sterilization. In hysteroscopy, high-frequency electrosurgery provides hemostasis and tissue dissection simultaneously. The first report on electrocoagulation with hysteroscopy appeared in 1976, when Neuwirth and Amin used a modified urological resectoscope to remove the submucous myomatous node.

The main difference between electrosurgery and electrocautery and endothermy is the passage of high-frequency current through the patient's body. At the heart of the last two methods is the contact transfer of thermal energy to the fabric from any heated conductor or thermal unit, there is no directional movement of electrons through the tissues, as in electrosurgery.

Mechanism of electrosurgical action on tissues

Passage of high-frequency current through the tissue leads to the release of thermal energy.

The heat is released on the portion of the electrical circuit having the smallest diameter and, consequently, the greatest current density. In this case, the same law applies as with the inclusion of an electric bulb. A thin tungsten filament warms up and releases light energy. In electrosurgery, this occurs on a portion of the chain that has a smaller diameter and greater resistance, i. E. In the place where the surgeon's electrode touches the tissues. Heat is not released in the area of the patient's plate, since a large amount of its area causes dispersion and a low energy density.

The smaller the diameter of the electrode, the faster it heats the tissues adjacent to the electrode due to their smaller volume. Therefore, cutting is most effective and less traumatic when using needle electrodes.

There are two main types of electro-surgical effects on tissues: cutting and coagulation.

Various forms of electric current are used for cutting and coagulation. In the cutting mode, a continuous low-voltage alternating current is supplied. The details of the cutting mechanism are not completely clear. Probably under the influence of current there is a continuous movement of ions inside the cell, which leads to a sharp rise in temperature and evaporation of the intracellular fluid. There is an explosion, the cell volume instantly increases, the shell bursts, the tissues are destroyed. We perceive this process as cutting. Exempted gases dissipate heat, which prevents overheating of deeper layers of tissues. Therefore, the tissues are dissected with a slight lateral temperature transfer and a minimal zone of necrosis. The corpse of the wound surface is thus insignificant. Because of superficial coagulation, the haemostatic effect in this regimen is negligible.

A completely different form of electric current is used in the coagulation regime. This is a pulsed alternating current with high voltage. Observe a burst of electrical activity, followed by a gradual attenuation of the sinusoidal wave. Electrosurgical generator (ECG) supplies voltage only for 6% of the time. In the interval, the device does not produce energy, the fabrics cool down. Heating of tissues does not occur as quickly as when cutting. A short burst of high tension leads to the devascularization of the tissue, but not to evaporation, as in the case of cutting. During a pause, the cells are dried. By the time of the next electric peak, the dry cells have increased resistance, leading to more heat dissipation and further deeper tissue drying. This provides a minimal dissection with the maximum penetration of energy into the depth of the tissues, denaturation of the protein and the formation of blood clots in the vessels. So ECG realizes coagulation and hemostasis. As the fabric drains, its resistance increases until the flow practically ceases. This effect is achieved by directly touching the electrode with tissues. The site of damage is small in area, but significant in depth.

To achieve simultaneous cutting and coagulation mixed mode is used. Mixed flows are formed at a voltage greater than under the cutting regime, but less than in the coagulation regime. Mixed mode provides drying of adjacent tissues (coagulation) with simultaneous cutting. Modern ECG have several mixed modes with different ratio of both effects.

The only variable that determines the separation of the function of different waves (one cuts and the other coagulates the tissue) is the amount of heat produced. Greater heat, released quickly, gives a cut, i.e. Evaporation of tissues. A little heat, released slowly, gives coagulation, i.e. Drying.

In bipolar systems work only in coagulation mode. The tissue located between the electrodes is dehydrated as the temperature rises. Constant low voltage is used.