Introduction
In modern surgical procedures, the high - frequency electrosurgical unit (HFESU) has become an indispensable tool. Its applications span a wide range of surgical fields, from general surgeries to highly specialized microsurgeries. By generating high - frequency electrical currents, it can efficiently cut through tissue, coagulate blood vessels to control bleeding, and even perform ablation procedures. This not only significantly reduces the time of surgery but also improves the precision of the operation, bringing more hope for patients' recovery.
However, along with its extensive use, the problem of burns caused by high - frequency electrosurgical units has gradually emerged. These burns can range from mild tissue damage to severe injuries that may lead to long - term complications for patients, such as infections, scarring, and in severe cases, organ damage. The occurrence of these burns not only increases the patient's pain and the length of hospitalization but also poses a potential risk to the success of the surgery.
Therefore, it is of great significance to explore the common causes of burns during the use of high - frequency electrosurgical units and corresponding preventive measures. This article aims to provide a comprehensive understanding of this issue for medical staff, surgical equipment operators, and those interested in surgical safety, so as to reduce the incidence of such burns and ensure the safety and effectiveness of surgical procedures.
Working Principle of High - Frequency Electrosurgical Unit
The high - frequency Electrosurgical Unit operates based on the principle of electrical energy conversion into thermal energy. The basic mechanism involves the use of high - frequency alternating current (usually in the range of 300 kHz to 3 MHz), which is far above the frequency range that can stimulate nerve and muscle cells (the human body's nerve and muscle response frequency is generally below 1000 Hz). This high - frequency characteristic ensures that the electrical current used by the Electrosurgical Unit can heat and cut tissue without causing muscle contractions or nerve stimulations, which are common problems with low - frequency electrical currents.
When the high - frequency electrosurgical unit is activated, an electrical circuit is established. The generator in the electrosurgical unit produces a high - frequency electrical current. This current then travels through a cable to the active electrode, which is the part of the surgical instrument that directly contacts the tissue during the operation. The active electrode is designed in various shapes depending on the surgical needs, such as a blade - shaped electrode for cutting or a ball - shaped electrode for coagulation.
Once the current reaches the active electrode, it encounters the tissue. Tissues in the human body have a certain electrical resistance. According to Joule's law ( , where is the heat generated, is the current, is the resistance, and is the time), when the high - frequency current passes through the tissue with resistance, electrical energy is converted into thermal energy. The temperature at the contact point between the active electrode and the tissue rises rapidly.
For the cutting function, the high - temperature generated at the tip of the active electrode (usually reaching temperatures around 300 - 1000 °C) vaporizes the tissue cells in a very short time. The water within the cells turns into steam, causing the cells to burst and separate from each other, thus achieving the effect of tissue cutting. This process is highly precise and can be controlled by adjusting the power and frequency of the electrosurgical unit, as well as the movement speed of the active electrode.
Regarding the hemostasis function, a lower - power setting is usually used compared to the cutting mode. When the active electrode touches the bleeding blood vessels, the generated heat coagulates the proteins in the blood and the surrounding tissue. This coagulation forms a clot that blocks the blood vessel, stopping the bleeding. The process of coagulation is also related to the tissue's ability to absorb heat. Different tissues have different electrical resistances and heat - absorption capabilities, which need to be considered during the operation to ensure effective hemostasis without excessive damage to the surrounding normal tissue.
In summary, the high - frequency Electrosurgical Unit uses the thermal effect generated by high - frequency electrical current passing through tissues with resistance to perform tissue cutting and hemostasis, which is a fundamental and crucial technology in modern surgical procedures.
Common Burn Causes
Plate - related Burns
Plate - related burns are one of the common types of burns caused by high - frequency electrosurgical units. The main reason for this kind of burn is the excessive current density at the plate area. According to safety standards, the current density at the plate should be less than . When calculating based on the maximum power and working under the rated load, the minimum plate area is , which is the lowest limit value of the plate area. If the actual contact area between the plate and the patient is less than this value, the risk of plate burns will occur.
There are several factors that can lead to a reduction in the effective contact area between the plate and the patient. For example, the type of electrode plate matters. Metal electrode plates are hard and have poor compliance. During the operation, they rely on the patient's body weight to press the plate. When the patient moves, it is difficult to ensure the effective contact area of the plate, and burns are likely to occur. Conductive gel electrode plates require applying conductive paste before use. When the conductive gel on the negative plate dries out or is placed on a damp area of the skin, it may also burn the patient. Although disposable adhesive - wrapped electrode plates have good compliance and strong adhesion, which can ensure the contact area during the operation, improper use such as repeated use or expiration can still lead to problems. Repeated use may cause the plate to become dirty, with accumulated dander, hair, and grease, resulting in poor conductivity. Expired plates may have reduced adhesive and conductive properties, increasing the risk of burns.
In addition, the placement location of the plate also affects the contact area. If the plate is placed on a part of the body with excessive hair, the hair can act as an insulator, increasing the impedance and current density at the plate area, hindering the normal conduction of current, generating a discharge phenomenon, and potentially leading to thermal burns. Placing the plate on a bony prominence, joint, scar, or other areas where it is difficult to ensure a large and uniform contact area can also cause problems. Bony prominences are difficult to ensure sufficient contact area and affect the uniformity of contact. The pressure at the bony prominence is relatively high, and the current density passing through is relatively large, increasing the risk of burns.
Non - plate - related Burns
High - frequency Radiation
High - frequency radiation burns occur when the patient carries or their limbs come into contact with metal objects during the operation. High - frequency electrosurgical units generate strong high - frequency electromagnetic fields during operation. When a metal object is present in this electromagnetic field, electromagnetic induction occurs. According to Faraday's law of electromagnetic induction ( , where is the induced electromotive force, is the number of turns of the coil, and is the rate of change of magnetic flux), an induced current is generated in the metal object. This induced current can cause local heating of the metal object and the surrounding tissue.
For example, if a patient wears a metal necklace or ring during the operation, or if a metal surgical instrument accidentally touches the patient's body, a closed - loop circuit is formed between the metal object and the patient's body. The high - frequency current in the electromagnetic field flows through this circuit, and due to the relatively small cross - sectional area of the contact point between the metal object and the tissue, the current density at this point is very high. According to Joule's law ( ), a large amount of heat is generated in a short time, which can cause severe burns to the patient's tissue.
Circuit Short - circuit
Circuit short - circuits can also lead to burns during the use of high - frequency electrosurgical units. Before using the device, if the operator fails to check whether each line is intact, problems may arise. For instance, the outer insulation layer of the cable may be damaged due to long - term use, improper storage, or external forces, exposing the internal wires. When the exposed wires come into contact with each other or with other conductive objects, a short - circuit occurs.
In addition, when using a hard plate, if the surface organic matter is not removed in time, it can affect the electrical conductivity and insulation performance of the plate. Over time, this can lead to the formation of a conductive path between the plate and other parts of the circuit, causing a short - circuit. Regular maintenance by a dedicated person is also crucial. Without regular inspection and maintenance, potential problems in the circuit may not be discovered in time, such as loose connections, component aging, etc., which can all increase the risk of short - circuits.
When a short - circuit occurs, the current in the circuit will increase suddenly. According to Ohm's law ( , where is the current, is the voltage, and is the resistance), when the resistance in the short - circuit part decreases sharply, the current will rise significantly. This sudden increase in current can cause overheating of the wires and components in the circuit, and if the heat cannot be dissipated in time, it will transfer to the patient's body through the electrodes, resulting in burns.
Low - frequency Sparks
Low - frequency sparks are mainly caused by two common situations. One is when the knife - head cable is broken. The high - frequency current in the electrosurgical unit is supposed to flow stably through the intact cable to the knife - head. However, when the cable is broken, the current path is disrupted. At the broken end of the cable, the current tries to find a new path, which leads to the formation of sparks. These sparks generate low - frequency currents.
The other situation is when the electrosurgical unit is operated too frequently. For example, if the surgeon starts and stops the electrosurgical unit rapidly, like repeatedly clicking the activation button in a short period, each activation and de - activation can cause a small spark to occur. Although each spark may seem small, when accumulated over time, they can cause a certain degree of low - frequency burn.
The harm of low - frequency sparks is significant. Different from high - frequency current - induced burns that are usually on the surface, low - frequency current - induced burns can be more dangerous as they can affect internal organs. For example, when the low - frequency current enters the body through the broken cable or frequent operation - induced sparks, it can directly affect the heart. The heart is very sensitive to electrical signals, and abnormal low - frequency currents can interfere with the normal electrical conduction system of the heart, leading to arrhythmias, and in severe cases, cardiac arrest.
Contact with Flammable Liquids
In the operating room environment, there are often some flammable liquids used for disinfection, such as iodine tincture and alcohol. High - frequency electrosurgical units generate sparks during operation. When these sparks come into contact with flammable liquids, a combustion reaction may occur.
Alcohol, for example, has a low flash point. When the alcohol - soaked disinfection gauze is left with too much alcohol, and it wets the disinfection drape or there is excessive residual alcohol in the operation area, and the electrosurgical unit is activated to produce sparks, the alcohol vapor in the air can be ignited. Once ignited, the fire can spread rapidly, not only causing burns to the patient's skin but also endangering the safety of the entire operating room. The combustion process can be described by the chemical reaction formula of alcohol combustion: . During this process, a large amount of heat is released, which can cause severe burns to the surrounding tissue and may also cause damage to the surgical instruments and operating room facilities.
Prevention Measures
Patient - related Precautions
Before the patient enters the operating room, a comprehensive pre - operation assessment should be carried out. First, all metal objects on the patient, such as jewelry (necklaces, rings, earrings), metal - framed glasses, and any metal - containing accessories, must be removed. These metal objects can act as conductors in the high - frequency electromagnetic field generated by the electrosurgical unit, leading to the generation of induced currents and potential burns, as described in the section on high - frequency radiation burns.
During the operation, it is crucial to ensure that the patient's body does not come into contact with any metal parts of the operating table or other metal - based equipment. If the patient has a history of metal implants, such as artificial joints, metal plates for fracture fixation, or dental implants, the surgical team should be aware of their location. In such cases, using a bipolar electrosurgical unit instead of a unipolar one can be considered. Bipolar electrosurgical units have a smaller current loop, which can reduce the risk of current passing through the metal implant and causing burns. For example, in orthopedic surgeries where there are existing metal implants in the patient's body, the use of bipolar electrosurgery can minimize the potential harm caused by the high - frequency current interacting with the metal.
Electrode Plate - related Precautions
Selecting the appropriate electrode plate is the first step. Different types of electrode plates have their own characteristics. For adult patients, an adult - sized electrode plate should be chosen, while for children and infants, corresponding pediatric - sized plates are required. The size of the electrode plate should be sufficient to ensure that the current density at the plate area is within the safe range (less than ). Disposable adhesive - wrapped electrode plates are preferred due to their good compliance and strong adhesion. However, before use, it is necessary to carefully check the integrity of the conductive gel on the plate, ensuring that there are no cracks, dry - out areas, or impurities. Expired electrode plates should be strictly prohibited from use, as their conductive and adhesive properties may have deteriorated.
The correct placement of the electrode plate is also of great importance. The plate should be placed on a muscle - rich and hair - free area, such as the thigh, buttocks, or upper arm. It is necessary to avoid placing it on bony prominences, joints, scars, or areas with excessive hair. For example, if the plate is placed on a bony prominence like the elbow or knee, the contact area may be uneven, and the pressure at this point is relatively high. According to the principle of current density ( , where is the current density, is the current, and is the area), a smaller contact area will lead to a higher current density, increasing the risk of burns. Additionally, the plate should be placed as close as possible to the surgical site to reduce the length of the current path within the patient's body, but at the same time, it should be at least 15 cm away from the surgical incision to avoid interference with the surgical operation.
Equipment and Operation - related Precautions
Equipment Inspection
Before the operation, a detailed inspection of the high - frequency electrosurgical unit and its associated lines should be carried out. Check the outer insulation layer of the cable for any signs of damage, such as cracks, cuts, or abrasions. If the insulation layer is damaged, the internal wires may be exposed, increasing the risk of short - circuits and burns. For example, a cable that has been bent too frequently or has been squeezed by heavy objects may have a damaged insulation layer. In addition, test the functionality of the electrosurgical unit by running a self - test function if available. This can help detect potential problems in the generator, control panel, and other components.
During the operation, periodically check the equipment for any abnormal sounds, vibrations, or heat generation. Abnormal sounds may indicate mechanical problems in the device, while excessive heat generation may be a sign of over - current or component failure. For example, if the electrosurgical unit emits a high - pitched whining sound during operation, it may be a sign of a malfunctioning fan in the cooling system, which could lead to overheating of the device and potential burns to the patient.
After the operation, clean and disinfect the equipment according to the manufacturer's instructions. Inspect the equipment again to ensure that there is no damage caused during the operation. Check for any residual blood, tissue, or other contaminants on the electrodes and cables, as these substances can affect the performance and safety of the equipment if not removed in a timely manner.
Operation Specifications
Operators of high - frequency electrosurgical units should be well - trained and familiar with the operation procedures. When setting the power of the electrosurgical unit, start with a low power and gradually increase it according to the actual needs of the operation. For example, in a minor surgical procedure, a lower power setting may be sufficient for tissue cutting and hemostasis. Unnecessarily high power settings can cause excessive heat generation, leading to more severe tissue damage and an increased risk of burns.
During the operation, the active electrode (knife - head) should be held steadily to ensure accurate cutting and coagulation. Avoid placing the active electrode in contact with non - target tissues when it is not in use. For instance, when the surgeon needs to temporarily stop the operation, the knife - head should be placed in a safe position, such as in a special holder, rather than being left on the surgical drape where it could accidentally touch the patient's body and cause burns.
Environmental Considerations
The operating room environment plays a vital role in preventing burns caused by high - frequency electrosurgical units. First, ensure that there are no flammable gases or liquids in the operating room. Flammable substances such as alcohol - based disinfectants, ether (although less commonly used in modern anesthesia), and some volatile anesthetic gases can ignite when in contact with the sparks generated by the electrosurgical unit. Before using the electrosurgical unit, make sure that the operation area is dry and that any flammable disinfectants have completely evaporated.
Control the oxygen concentration in the operating room. High - concentration oxygen environments increase the risk of fire. In areas where the electrosurgical unit is used, especially in the vicinity of the patient's airway, the oxygen concentration should be kept at a safe level. For example, when performing surgeries in the oral or nasal cavity, extra care should be taken to ensure that the oxygen flow rate is properly adjusted and that there is no leakage of high - concentration oxygen near the surgical site where the electrosurgical unit is in use.
Conclusion
In conclusion, high - frequency electrosurgical units are essential and powerful tools in modern surgical procedures, but the potential for burns during their use cannot be overlooked.
To prevent these burns, a series of comprehensive measures need to be taken. Medical staff, surgical equipment operators, and all those involved in surgical procedures must have a deep understanding of these burn causes and preventive measures. By strictly following the preventive strategies, the incidence of burns caused by high - frequency electrosurgical units can be significantly reduced. This not only ensures the safety of patients during surgery but also contributes to the smooth progress of surgical procedures, improving the overall quality and effectiveness of surgical treatments. In the future, continuous research and improvement in the design and use of high - frequency electrosurgical units are expected to further enhance surgical safety and patient outcomes.
