After 90 years of development since the American scientist William T. Bovie developed the high-frequency electrosurgical unit in the 1920s, the ESU has become an indispensable device in the operating room.

William T. Bovie

ESU in a narrow sense refers to a high-frequency electrosurgical unit that directly uses high-frequency and high-voltage alternating current to cut and coagulate human tissue through the thermal effect; in a broad sense, ESU refers to equipment that uses high-frequency electrical energy to cut, separate, and coagulate tissue, including high-frequency electrosurgical devices, RF knife, ion knife, etc.

Although the high-frequency electrosurgical generator has undergone rapid development, its principle is still to use the high-frequency current with extremely short pulse time to induce ions in human tissues to oscillate in viscous body fluids to generate heat.


When the surgical electrode of the ESU is in contact with the human body, due to the small effective area of contact, the high impedance body of the electrode itself allows high current density to pass through the local tissue, directly generating high heat and causing the separation and coagulation of the tissue. And because of the high frequency, the small effective area, and high current density, the consequences may be serious once a problem occurs. Therefore, the potential safety hazards in each link should be identified and evaluated, and effective preventive measures should be taken during the use of electrosurgical equipment.

Adverse events in the operating room caused by improper use of electrosurgical equipment include patients’ electrical burns, operating room fire incidents, and electrical shock injuries, among which patients’ electrical burns are the most common. The common clinical manifestations of electric burns are as follows:

  • The burns at the paste location of the negative plate of the electrosurgical generator are mainly at the negative plate or the skin around the negative plate. The burn is above 1cm×1cm and the depth reaches Ⅱ°~Ⅲ°.
  • Burns around the skin of the surgical field are mainly distributed in the surgical field or adjacent skin around the surgical field. They are manifested as redness, swelling, and blisters, with varying areas.
  • The burns of the patient’s contact with the conductors mainly occurred on the limbs, and the degree of burns showed redness and blisters.
  • Burns in the patient’s body are the most dangerous type, which manifests as severe burns to the tissues around the conductor in the patient’s body, and may cause cardiac arrest due to burns to the myocardium (patients with pacemakers).

Electric burns can cause great harm to patients. The common causes of burns from electrosurgical equipment include the following:

  1. The electrosurgical unit handle switch is out of control. The main cause of such burns is the malfunction of the handle or footswitch. When the switch is not pressed or the foot control is not stepped on, the electrosurgical generator continues to work. At this time, if the device touches human tissues, it will cause local burns. When the electrosurgical generator is not in use, place the handle on the cloth sheet near the surgical field. If the cloth sheet is soaked in saltwater, and the skin touched by the cloth sheet will be burnt.
  2. Electric burning meets flammable liquid gas. When using an alcohol-based skin disinfectant, the disinfectant may collect on the operating table, and the patient’s skin may burn due to electrode discharge during the operation. The use of electrosurgery or electrocoagulation in airway surgery should prevent airway burns. Similarly, patients with intestinal obstruction should be cautious with electrosurgery.
  3. Leakage current burns. The current output by the electrosurgical generator can be returned to itself through any conductor connected to the ground. This conductor can be the operating bed, the staff in contact with the patient, or the ECG monitor. Burns are more likely to occur when the negative plate is poorly contacted. Any part of the body that comes into contact with metal parts such as the operating bed, tray, infusion stand, head frame, etc., is burned. When the surgeon’s glove is perforated, the skin at the perforation site may be burned.
  4. Improper use of the negative plate of the electrosurgical unit. The main function of the negative plate of the ESU is to recover high frequency current to prevent the patient from being burned. If the patient is moved or incorrectly operated during the operation, the electrode plate and the skin may be incompletely adhered, resulting in a reduction in the effective conductive area and excessive local temperature causing burns. It may also cause burns if you use a negative plate of inappropriate size, or use an expired, damaged, and dry negative plate. According to AAMI’s regulations, the temperature of the skin under the electrodes should not exceed 6°C, otherwise, burns may occur. It should be noted that the selection and correct operation of the paste position of the negative plate also play a very important role in the prevention of burns under the negative plate.
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