Choosing the right electrosurgical unit

An electrosurgical unit is a device that uses high-frequency (HF) electrical currents to cut or coagulate tissue during surgery, known as electrosurgery. It consists of an electrosurgical generator that transforms electrical energy into HF current. It is operated using a specific control. The generator is connected to an active electrode. It is this active electrode that comes into contact with the tissue it will create a thermal effect on. Electrosurgical units have multiple functions and electrodes that vary according to the surgical applications.

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  • What are the different types of electrosurgical units?

    There are different types of surgical units that use different sources of energy: radio frequency or high-frequency, ultrasound and molecular resonance.

    Radio frequency electrosurgical unit

    • Ultrasound surgical unit: these units work with ultrasonic handpieces. They have an ultrasonic wave generator. These ultrasound waves break the hydrogen bonds of the cells during coagulation, while the cutting is done by cavitation.

      Ultrasound surgical unit

    • Molecular resonance surgical unit: unlike high frequency surgical units, these units use frequencies that interact with tissue in a non-thermal way. Tissue is only modified on a molecular level, making this technique is less invasive.

      Molecular resonance surgical unit

  • What are the main modes of operation for electrosurgical units?

    Electrosurgical units are mainly used to cut or coagulate tissue. The cut and coagulation can be performed using two techniques: monopolar and bipolar. Here are the differences:

    • Monopolar technique: this technique uses a single active electrode which will also act as a neutral electrode. It transmits the HF current from the generator. When this electrode comes into contact with the tissue, a high current density is transmitted. It is this high concentration of energy on a small area that achieves the desired effect. The current then flows through the patient’s body to the neutral electrode. In this way the electrical circuit is closed.
      • Advantages: suitable for desiccating large tissue masses;
      • Disadvantages: higher risk of electrocution, to reduce this risk it is important that the neutral electrode is correctly applied to the patient; this technique is not compatible with patients with metal implants or pacemakers.
    • Bipolar technique: the HF current arrives through an active electrode and exits through the neutral electrode, without flowing through the patient’s body. Bipolar forceps are the most common instrument used for this technique. They allow the active electrode and the neutral electrode to be placed opposite each other. The current flows directly from one tip of the forceps to the other. The neutral electrode has no function here.
      • Advantages: this technique is safer than the monopolar technique as there is no risk of burning or electrocution for the patient; this technique should be used for patients with pacemakers
      • Disadvantages: not suitable for desiccating large tissue masses.
  • What types of cuts and coagulations can be performed with the monopolar and bipolar techniques?

    Monopolar technique

    With the monopolar technique, it is possible to perform a pure or hemostasis monopolar cut, as well as gentle, forced or fulguration coagulation.

    • Monopolar cutting:
      • Pure cut: obtained by generating a pure sine wave. For the tissue to be cut, the voltage between the active electrode and the tissue must be at least 200 Vp.
      • Hemostasis cut: this cut is less bloody than the pure monopolar cut. The cut is clean and the edges are coagulated to a depth that can be adjusted. This cut is obtained by increasing the Vp voltage and including “breaks” in the HF wave trains. These breaks allow for a better diffusion of heat and in this way encourage hemostasis.
    • Monopolar coagulation:
      • Gentle coagulation: the voltage between the active electrode and the tissue is less than 200 Vp. This produces a slow, penetrating coagulation
      • Forced coagulation: the output voltage is high (up to kVp). The coagulation is faster but less penetrating than gentle coagulation
      • Coagulation with fulguration: the output voltage here is very high (4 kVp). In this case the tissue is desiccated without the active electrode coming into contact with the tissue (“non-contact coagulation”). This technique is widely used when it is necessary to coagulate a large area or to stop widespread bleeding (i.e. coagulation of the sternum) but also to perform “underwater cutting” i.e. transurethral resection).

    Bipolar technique

    With the bipolar technique, a bipolar cut and bipolar coagulation can be performed.

    • Bipolar cutting: this fairly recent technique has developed with the increasingly frequent use of endoscopic surgery. The development of this technique, which is safer than the monopolar technique, has led to the development of bipolar cutting instruments. The operating principle of the electrosurgical unit is similar to that of the monopolar cut except that the current only flows between two electrodes very close to each other. The risk of patient burns is almost non-existent, there is practically no current leakage and the influence on pacemakers is very small.
    • Bipolar coagulation: this technique is widely used, often in complex surgical procedures. Bipolar forceps are usually used and the tips must be kept clean during the operation to prevent them from sticking to the clamped tissue and causing further bleeding when they are removed. As in gentle coagulation, low (< 200 Vp) stabilized voltages are used.
  • What are examples of surgical procedures where electrosurgery is suitable?

    Electrosurgical units are used in operating rooms for many surgical procedures such as endoscopic, cardiac, dental and cosmetic surgery.

    • Endoscopic surgery: in this type of minimally invasive surgery, which is becoming increasingly popular, bipolar electrosurgical cutting is widely used
    • Heart surgery: in heart and liver surgery, fulguration is mainly used
    • Dental or oral surgery: in the oral cavity, electrosurgery is used to stop bleeding and remove any exophytic soft tissue tumor formations
    • Cosmetic or dermatological surgery: electrosurgery is used for skin removal, electric depilation or the treatment of rosacea by electrocoagulation
  • Which electrodes are used in electrosurgery?

    The electrodes are mainly classified according to their functions. These are neutral, cutting, coagulation, desiccation and electrotomy.

    • Neutral electrodes: these are only used in monopolar electrosurgery. They must be applied to the entire active surface. They can be disposable or reusable.
    • Cutting electrodes
    • Coagulation electrodes: ball tube electrodes, knife electrodes or lancet electrodes are used for monopolar coagulation; for bipolar coagulation, bipolar forceps are used, which can come in various shapes.
    • Desiccating electrodes
    • Electrotomy electrodes: they can be blade, needle or loop electrodes.
  • What are the risks associated with using an electrosurgical unit?

    Several risks are inherent in the use of an electrosurgical unit. They can affect patients, users or third parties. It should be noted that high frequency generators and their accessories are subject to the standards for technical equipment with specific risks. These are the different risks:

    • High-frequency burns. Sometimes bedsores caused by the patient’s position during the operation can be mistaken for burns.
    • Fires due to the presence of combustible liquids or gases in the operating room
    • Electrical hazards due to incorrect connection to other devices
    • Technical problems with defective equipment or accessories
  • What will influence the thermal effect of the surgical unit?

    The thermal effect of the surgical unit is influenced by a series of factors such as the current intensity, the degree of modulation and the shape of the electrode. These are the factors:

    • Current intensity and output power
    • Degree of modulation: this is the shape of the pulses of the HF current. They depend on the generator itself and the possible settings on the electrosurgical unit. The degree of modulation may play a role in the efficiency of the cut or the depth of coagulation
    • The shape of the electrode: the shape of the electrode determines the concentration of the field lines at the point of application. It therefore has an impact on the temperature of the zone and the result obtained
    • The state of the active electrode: according to Joule’s law, the expected effects depend on the resistance present. In addition to the physical resistance of the tissue, the resistance caused by residue potentially deposited on the active electrode must also be taken into account. It is therefore essential to always clean electrodes thoroughly during an operation
    • Cutting speed and duration of the intervention
    • Characteristics of the tissue: depending on their physiology, different types of tissue provide different levels of resistance.
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