Electro Surgical Unit (ESU).

Electrosurgery. 

Definition:- 

Electrosurgery is a procedure involved in cutting and coagulation of biological tissues. This procedure uses high frequency alternating electrical current. This is also used for dissection, fulguration (removal of abnormal tissue growth), and for shrinking tissues.

Principles of Electrosurgery.

The main principle of electrosurgery is that it uses an alternating (AC) electric current at high frequency or radiofrequency. The frequency ranges from 100KHz to 5 MHz. This current is passed through the patient’s body and produces the heat. Therefore, the surgical procedure is performed using an electrode and it is controlled either by a hand switch or footswitch.

Another procedure called Electrocautery is related to Electrosurgery. But in electrocautery, it uses direct current (DC) and heat is generated in the circuit, not in the patient’s body. Electrocautery is also known as thermal cautery. This procedure uses heated metal wire electrode for tissue destruction (i.e either to remove or coagulate the damaged tissue). As we all know, the movement of electrons is called electric current. In Direct current, electrons flow in the same direction. In Alternating current, the flow of electrons changes periodically.

Modes of Electro-surgery:

Monopolar Electrosurgery vs Bipolar Electrosurgery.

In Monopolar Electrosurgery, it consists of an electrosurgical generator, active electrode, patient and patient return electrode. During operation, the patient plate is attached to any part of the patient’s body. Electric current is generated from the electrosurgery generator and it passes through the active electrode where it creates heat in the tissue as well as the entire body cavity. And it returns back to the generator through the patient return electrode.

Monopolar is used to cut, coagulate, desiccate tissues. This is the most commonly used method in electrosurgery.

In Bipolar Electrosurgery, the bi-forceps electrode is used. The forceps perform both the active and return electrode function. Forceps are used for grabbing the tissue and the electric current passes through the forceps to the respective area in the tissue. 

Therefore this prevents further damage to other body parts and prevents the patient from any burns. Bipolar surgery uses only less voltage and hence it is not used for cutting and coagulation of larger bleeding tissues. Bipolar surgery is recommended in patients with implanted devices to prevent them from short circuit.

Types of Electrosurgical Technique:-

• Electrocoagulation
• Electrodesiccation
• Electrofulgaration
• Electrocution

These techniques are used for destroying abnormal or damaged tissues. Also used to prevent loss of blood while performing the surgery.

Types of Current:-

There are three types of current used in electrosurgery

• CUTTING – Cutting current is a continuous sinusoidal waveform. The power of cutting current must be maintained between 50W and 80W. The surgeon holds the electrode slightly away from the tissue to create a spark for cutting. This spark creates heat in the tissue area.

• COAGULATION – Coagulation current is an interrupted and damped sine waveform. The waveforms have high peak voltages. Due to this, the temperature also increases causing thermal destruction in the tissues. Therefore, coagulating current is used for coagulation in bleeding vessels/tissues.

• BLENDING –Blend current has a combination of both cutting and coagulating current waveform. This is also a modified form of cutting current. This blending current is used in hemostasis of tissues. Blend current produces a higher peak to peak voltages. Therefore, the duty cycle also changes between the burst current and coagulation. For maintaining the same directional flow, this blend current can be rectified. Surgeries like dental and dermatology use rectified current.

Tissue Effects of Electrosurgery

• Vapourisation – Vapourisation of tissue is achieved by producing heat in the tissue. Heat is produced by creating a spark in the surgical area with the help of the electrode. During surgery, the surgeon creates a minimum spark over the tissue. Due to sparking, the maximum current can be produced.

• Fulguration –Fulgaration is a combination of sparking with coagulation. This creates longer sparks in the tissue. In this process, less heat is produced in the tissue. That is why coagulation takes place rather than vapourisation.

• Dessication – Desiccation is produced by low current density and high voltages. This is the modification of coagulation. In this procedure, the electrode is used directly in contact with the tissue, which converts the electrical energy into heat, which causes the cells to shrink. 

Electrosurgical Unit 

Electrosurgical unit is a device used in electrosurgery for cutting, coagulation, fulguration, and desiccation of tissues. Electrosurgical unit is used in surgeries to prevent blood loss. ESU consists of an electrosurgical generator with one or more electrodes and a patient return electrode. This unit is controlled using a hand switch or a footswitch.

The Electrosurgical Generator produces different waveforms corresponding to the tissue effects. 

The Active Electrode is placed directly in the surgical area and the patient Return Electrode is kept in any part of the patient body.

The electrosurgical unit creates an electric current to pass through the electrode and produces heat in the tissue for cutting, coagulating and removing damaged tissues. It is operated under two modes: Monopolar and Bipolar.

In monopolar mode, there is an active electrode which carries the current to the tissue and a patient return electrode for taking back the current from the tissue. In bipolar mode, it uses the forceps type of an electrode which performs both active and return operations.

Electrosurgery is often similar to diathermy. Diathermy uses an electromagnetic current to produce heat. It uses dielectric poles. Diathermy passes electromagnetic waves and thus heat is generated in the body. The generated heat increases blood flow in the area causing pain. This is most commonly used in muscle and joint problems for allowing free blood flow. 

There are three types of Diathermy. This includes:- 

• Shortwave diathermy – High-frequency electromagnetic current is used to generate heat in the tissue. This is used to treat pains that occur during kidney stones.

• Microwave diathermy – Microwaves are used to generate heat in the body. Microwaves cannot penetrate deep into the muscles.

• Ultrasound diathermy – This uses sound waves by causing vibration in the tissues. This is used to treat deeper tissue areas.

Types of Electrodes

1. Needle electrode
2. Blade electrode
3. Wire loop electrode (used for cutting)
4. Electrosurgical forceps
5. Angular electrode

Block Diagram of ESU :

High-frequency power is required to generate heat from the waveform generator. Different waveforms like cutting, coagulation and blending are also produced from the generator. The mode selector is used for selecting which type of mode should be used while performing the surgery. Power level control determines the power applied to the electrodes during surgery.  Alarm circuit is used for creating safety alarms whether the electrodes are attached properly in the patient circuit. 

Circuit Components

The front panel consists of:- 

Power ON/OFF switch – Turning On/ Off of the electrosurgical unit. 

Mode selector – For selecting the modes for performing surgery (CUT mode, COAG mode, BLEND mode ). Cut mode indicates a yellow colour, whereas Coagulation mode indicates a blue colour. 

Fault indicator switch – This indicates poor contact of patient return electrode with the patient by producing alarm. Three-pin switch for monopolar use only hand switch. Three-pin switch for bipolar can be activated with or without footswitch. There is also a two-pin connector for the patient return electrode.

Rear panel Consists of:-

Footswitch control – This is for connecting the footswitch. 

The volume control knob - is used for controlling the audio volume during cutting, coagulation or blending. Power cord connection.

Safety precautions

• Electrosurgery must be performed by specially trained technicians in electrosurgical technologies.
• Electrosurgery should not be performed in oxygen-rich environments because it may easily catch fire and cause serious burns. 
• Before operating, insulation of the electrode must be checked carefully to avoid thermal injuries. 
• Do not activate the equipment in an open circuit.

Do’s

• Electrodes should be placed in clean, dry areas

• Use only insulated electrodes

• Electrodes must be placed in well-cleaned holster, when not in use

• Electrode tips must be cleaned properly.

• Use only low voltage waveforms while operating

• Bipolar electrosurgery can be performed when necessary

Don’ts

• One should not use the electrode in the presence of flame causing agents like (alcohol, tincture etc.) to avoid burns and fire.
• Electrodes should not be wrapped around metal instruments because they cause burns.
• Rubber catheters should not be used in electrode tips.
• One should not operate the electrosurgical unit by standing on a wet surface to prevent them from shocks.
• Surgeons or technicians must not perform the operation with wet hands/wet gloves to prevent electric shock.
• Must wear surgical masks during surgery to avoid smoking difficulties which may cause breathing problems.
• Avoid using the electrode near electric devices.
• Do not use the equipment in patients prior to testing. 

Problems in ESU

• If surgery is performed in oxygen-rich environments, it may cause a surgical fire.

• Patient burns may also be caused by detachment of the electrode pad.

• Incorrect placement of the electrode may also cause burns.

• Electrosurgical injury occurs when the electrode comes in contact with non-target tissue.

• Since the device uses high current, it may cause electric shock, the transmission of infection etc.

• Direct skin contact will cause burns.

Preventive Maintenance

• Regular testing of the equipment should be done to prevent any harm and to enhance patient and staff safety. 
• The person handling the equipment must be well trained by the manufacturer.
• He/She must follow the instructions given in the manual. 
• The technician must carefully inspect the insulation. 
• Lower power setting must be used when starting the equipment for use.

Risks of Electrosurgery

• Most of the risks are caused by thermal injuries. This is mainly due to unintended contact of the active electrode with any part of the body tissues. 
• Another kind of thermal injury is caused by the contact of the active electrode with metal instruments.
• Injuries caused by smoke also causes breathing problems in both patients and surgeons.
• Major risks are associated with respiratory illness and irritation in the eyes, skin etc.
• Therefore, proper measures must be taken before handling the equipment during surgery.

Electrical safety

• The proper power cord must be used. It must be properly grounded.
• Use only proper fuses which have correct voltage and current rating.

Patient Safety

• Proper contact must be maintained between the patient and other metal parts to avoid burns.

• Patient electrode must be connected in order to avoid skin injuries.

• Ensure the connections made do not affect the blood supply in the patient.

Clinical Applications

• Electrosurgery is often used in most of the operations involving tissue surgeries
• ENT (To control nose bleeding)
• Gynaecology
• Ophthalmic surgery
• Dermatology (To remove abnormal skin growth, moles etc.)
• To remove lesions, hair follicles.
• Also used in surgeries associated with organs like liver, spleen, kidneys and heart surgery.

Environments of use

Electrosurgery is used in operating rooms in the hospital while performing surgeries.

Troubleshooting

• Check Electrosurgical unit for any physical damage
• Ensure all cables, electrodes, power cord is connected properly
• Check the power cord properly or immediately replace it.
• Pin connections and switches must be properly checked. If any damage is found, it must be replaced immediately.

👉 Watch ESU Video on Our YouTube Channel Below:- 

Article Prepared By:-

👉 Sumitha Ramadass

References

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3407433/#:~:text=Principles%20of%20Electrosurgery,Often%20%E2%80%9Celectrocautery%E2%80%9D%20is&text=Electrocautery%20refers%20to%20direct%20current,alternating%20current%20(Figure%201).&text=Electrical%20current%20flows%20when%20electrons,produced%20when%20electrons%20encounter%20resistance.
• http://www.boviemedical.com/2016/10/03/bipolar-electrosurgery-vs-monopolar-electrosurgery/
• https://www.asit.org/assets/documents/Prinicpals_in_electrosurgery.pdf
• https://www.glowm.com/section_view/heading/electrosurgery-principles-biologic-effects-and-results-in-female-reproductivesurgery/item/21#:~:text=There%20are%20three%20basic%20types,%2C%20nonmodulated%20sinusoidal%20waveform%20(Fig.
• https://veteriankey.com/surgical-modalities-laser-radiofrequency-ultrasonic-and-electrosurgery/
• https://www.semanticscholar.org/paper/Electrosurgery%3A-principles-and-practice-to-reduce-Brill/ba1a6e6b411cba18601762375b62562cdf166677/figure/5
• https://www.uptodate.com/contents/overview-of-electrosurgery
• https://www.slideshare.net/prasadvagal/electrosurgical-unit
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4579996/#:~:text=An%20electrosurgical%20unit%20(ESU)%20consists,do%20the%20corresponding%20tissue%20effects.
• https://avantehs.com/p/11947
• https://www.cehjournal.org/article/electrosurgical-units-how-they-work-and-how-to-use-them-safely/
• https://www.gimaitaly.com/prodotti.asp?sku=30512&dept_selected=44&dept_id=446
• http://www.micromed.com/en-US/products/electrodes/
• https://www.sutter-med.de/en/products/monopolar-instruments/monopolar-electrodes_aid_50.html
• https://www.who.int/medical_devices/innovation/electrosurgical_unit.pdf
• https://www.flukebiomedical.com/blog/what-are-electrosurgical-units-why-should-we-test-them%3F
• https://webstor.srmist.edu.in/web_assets/srm_mainsite/files/downloads/esu.pdf
• https://www.magmedical-equip.com/product/valleylab-force-fx-c-electrosurgical-unit/
• https://docplayer.net/21481453-Instructions-electrosurgical-unit-psd-30.html