High Frequency Electrosurgery Unit has two main modes of operation: monopolar and bipolar.
In the monopolar mode, tissue is cut and coagulated with a complete circuit consisting of a high-frequency generator within the high-frequency electrosurgical unit, patient paddles, connecting leads, and electrodes. In most applications, current is passed through the patient through active leads and electrodes, and from the patient pads and leads back to the generator of the HF electrosurgery.
The heating effect of high-frequency electrocautery, which destroys diseased tissue, is not caused by the heating electrode or tip, as is the case with electrocautery. It concentrates high-frequency current with high current density and directly destroys the tissue just below the point of contact with the active electrode tip. Coagulation occurs when the temperature of tissue or cells in contact with or adjacent to the active electrode rises to the point where the proteins in the cells denature. This precise surgical effect is determined by the waveform, voltage, current, tissue type and electrode. shape and size.
To avoid continuing to heat tissue and burn the patient when the current leaves the patient and returns to the HF electrosurgical unit, the patient paddle in a monopolar device must have a relatively large area in contact with the patient to provide a low impedance and low current density channel. Some high-frequency electrosurgical knives used in doctor's offices have low current and low density, and cannot use patient pads, but most general-purpose high-frequency electrosurgery uses a large current, so patient pads are required.
The output system isolated from the ground makes the current of the high-frequency electrosurgery no longer need an auxiliary channel between the patient and the ground, thereby reducing the risk of burning the body that may be in contact with the ground. With a ground-based system, the risk of burns is greater than with an insulated output system.
Bipolar coagulation is to provide high-frequency electrical energy to the body tissue through the two tips of the bipolar forceps, so that the blood vessels between the two ends of the bipolar forceps are dehydrated and coagulated to achieve the purpose of hemostasis. Its scope of action is only limited between the two ends of the forceps, and the degree of damage and impact on the body tissue is much smaller than that of the monopolar method, and it is suitable for sealing small blood vessels (diameter <4mm) and fallopian tubes. Therefore, bipolar coagulation is mostly used in more delicate operations such as brain surgery, microsurgery, ENT, obstetrics and gynecology, and hand surgery. The safety of bipolar coagulation is gradually being recognized, and its use is gradually expanding.
When the high-frequency high-voltage current generated by the high-frequency electrosurgical knife passes through the high-impedance tissue, it will generate heat in the tissue, causing the tissue to vaporize or coagulate. During electrosurgical use, the resistance varies from 100 ohms to 2000 ohms. As the tissue coagulates, the water in the cells vaporizes, drying out the tissue, causing a constant increase in electrical resistance, and eventually a complete cessation of current flow.