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What are Electrosurgical Units?

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What are Electrosurgical Units?

Electrosurgical units (ESU) use an alternating high current coupled with a high frequency to cut and cauterize a patient during surgery. The ESU generates heat in the tissue and “dissects” the cell. Dissecting the cell means the cell is destroyed by removing all water and drying the cell. Using an ESU allows the surgeon to cut and coagulate at the same time.

How does an ESU work?

The device dissects by converting electromagnetic energy into kinetic energy into thermal energy, creating different effects on the cell/tissue. Applying current to a cell will give it polarity, this aligns the ions. Because of the current alternates, it causes the ions to oscillate and create friction. The generator takes your 60 Hz from the wall outlet and changes it to about 500 000 Hz.

Regularly a cell is around 37 degrees Celsius, around 50 degrees, and the cell dies over time. Between 60-90 is instant cell death and where desiccation and fulguration occur. When we get to 100 degrees, water boils, and the cell vaporizes.

Monopolar vs Bipolar?

ESU’s can be set up in two different ways, monopolar and bipolar. Electrosurgery is always a closed circuit, but it’s different in how we close the circuit.

During the Bipolar method, the current is sent through two prongs or forceps. The current enters the patient from one prong, the tissue is desiccated in between, and then the current leaves out the other prong. Bipolar is useful when the area is small enough for you to grab or can be surrounded by both sides. It’s especially useful when used in patients with implanted devices. The ESU keeps the current between the electrodes, and the current does not pass through the device.  By keeping the current between the electrodes, it does not cause a misfire or a short.

With the monopolar method, a pencil with one tip is used. The current starts at the pencil and enters the patient’s body; it then completes the circuit and leaves through a return electrode pad.

Why does the energy only burn at the point of the pencil and not when it leaves out the pad?

The energy is achieved by dispersion. When the current enters the patient, it is at the very small pencil tip and so the energy is dense and compact. When the energy leaves the body, it is through the pad, which is large and covering a greater surface area, not harming the patient as it leaves. This is like a bed of nails, one nail will puncture you, but when the pressure is dispersed, you can apply much more weight without harm. Monopolar is very versatile and practical, making it the most used.

What are the common failures in ESU’s?

ESU’s are complex machines, but the common failures usually happen at the patient side. There can be issues with the pencil; if there are cracks, then it can shock the user. This can happen if there are breaks in the wire also. If the pads are bad in monopolar surgery, then we can burn the patient, as we mentioned before. If the output of the unit is not what is displayed, then we can have a problem of burning or not having enough power to do the job. An ESU can do great work, but only if a lot of parts can work in tandem.


What does TRH Services perform during preventative maintenance?

One of the tests checked by Biomeds would be the CQM (contact quality monitoring) or REM test. In the circuit, there is a REM system that measures the resistance at the return electrode site, which references a safe resistance. If this were to exceed the safe amount, a pad site burn might occur. It is our duty to ensure the REM system is in calibration and working order. Aside from that, we check cable and pen integrity. We assure the output is what is displayed on the unit. And lastly, we perform electrical safety to ensure you are not shocked in any way that the unit is not meant to perform!

TRH Value

During our annual preventive maintenance, TRH Services will fully test the your Electrosurgical Unit (ESU).  TRH Services will completed extensive testing, with a focus on electrical safety and ensures that the built-in safety features are operating according to manufacture specification; calibrations are performed as deemed necessary to ensure the ESU is safe to use. Our maintenance program extends the life of your ESU and is cost-effective, especially in medical settings.

For more information on TRH Services, and the work that we do with Electrosurgical Units (ESU), please call 1-844-371-9488 or email info@trhservices.ca

Here are some common wax baths that we work on at TRH Services:


Description FieldManufacturer FieldModel Number Field
Electrosurgery UnitBirtcher733
Electrosurgery UnitBovie Medical CorporationA1250U (AAORN 1250U)
Electrosurgery UnitBovie Medical CorporationA940
Electrosurgery UnitBovie Medical CorporationDerm 942
Electrosurgery UnitColtene/Whaledent Inc.Perfect TCSIII
Electrosurgery UnitConmed Health Care Group7-9000-115
Electrosurgery UnitConmed Health Care GroupSystem 5000
Electrosurgery UnitCovidienForce Triad
Electrosurgery UnitEllman International Inc.70FFP
Electrosurgery UnitEllman International Inc.FFPF
Electrosurgery UnitERBE Elektromedizin TubingenVIO 200S
Electrosurgery UnitERBE Elektromedizin TubingenVIO 300 D
Electrosurgery UnitERBE USA IncVIO 200S
Electrosurgery UnitEthicon Endo-Surgery LLCGEN11
Electrosurgery UnitMedtronicForceFX
Electrosurgery UnitOlympusESG-400
Electrosurgery UnitValleylabForce 1B
Electrosurgery UnitValleylabForce 1C
Electrosurgery UnitValleylabForce 2
Electrosurgery UnitValleylabForce 2-20PC
Electrosurgery UnitValleylabForce Fx
Electrosurgery UnitValleylabForce FX – CS
Electrosurgery UnitValleylabForceFX
Electrosurgery UnitValleylabForceTriad


Written by: Andrew Ta
Edited by: Tyler Hasenpflug, C.E.T.