Engineering aspects of electrosurgery

1. Electrosurgery
Presented by :
Ashan Warnakulasuriya

2. What is Electrosurgery?
• Electrosurgery is the application of a high-frequency (radio frequency)
alternating electrical current to biological tissue for thermal destruction of
tissue through dehydration, coagulation, or vaporization.
• Ability to make precise cuts with limited blood loss
• General surgical procedures:
 dermatological, gynecological, cardiac, plastic, ocular, spine, ENT, maxillofacial,
orthopedic, urological and general surgical procedures
• Voltage values from 230 V– 9 000 Volts is passed through tissue.
• Radio Frequency range for Electrosurgery is 100 KHz to 5 MHz

3. Neuromuscular Stimulation

5. Stimulus effect
• Pulsating electrical current e.g. d.c. pulses or low-frequency currents
(including mains supply frequencies) have a stimulating effect on nerve
and muscle cells. (ability to depolarize muscle and neural cells.)
• Stimulation of the standard ion exchange in the human body that is
responsible for the physiological transmission of stimulus.
• Stimulation of this kind leads to a spasm in the muscle that can extend
to extra-systole and ventricular fibrillation.
• With high frequency alternating currents (> 100 kHz), the physiological
system can no longer follow the stimulation impulse. An insensitivity to
stimulus develops.
• Jacques-Arsène d'Arsonval discovered that currents with frequency over
5 KHz did not cause the muscular contractions and nerve stimulation
effects of electric shock.

6. Brief History
• The use of heat for the treatment of wounds can be traced to Neolithic times.
• Ancient Egyptians (c. 3000bc) have described the use of thermal cautery to treat ulcers and tumors of
the breast
• Hippocrates (469–370 BC) employed heat to destroy a neck tumor
• Albucasis (980 BC) was reported to have used a hot iron to control bleeding
• Benjamin Franklin and John Wesley first described the use of Direct current (DC) for medical
therapeutics, in the mid-eighteenth century.
• In 1889 D'Arsonval’s groundbreaking discovery in electrophysics.
• In 1909, Doyen described the use of bipolar RF instruments for the coagulation of tissue
• In 1907 Forest’s invention called the “Audion”, a triode-containing vacuum tube that amplified
electrical signals
• In 1924 Wyeth became the first to report use of avacuum tube-generated, continuous alternating RF
current to cut tissue in humans
• William T. Bovie in 1926 invented the first electrosurgical generator

7. Source : Fundamentals of Electrosurgery by Malcolm G. Munro

8. Electrosurgery and Electrocautery
• Electrosurgery is the application of a high-frequency (radio frequency) alternating electrical
current to biological tissue for thermal destruction of tissue through dehydration, coagulation,
or vaporization.
• Electrocautery is a process in which a direct or alternating current is passed through a
resistant metal wire electrode, generating heat. The heated electrode is then applied to living
tissue to achieve hemostasis or varying degrees of tissue destruction
• Passing electrical current through tissueElectrosurgery
• Current is used to heat a handheld
element, which is then applied to the
tissue
Electrocautery

9. Components of a modern Electrosurgery
Device
Electrosurgery Generator (ESU)
Active Electrode
Bipolar Forceps

10. Patient Return Electrode
Footswitch

11. Working Principle of Electrosurgery
• Radiofrequency starts at about 3 KHz and extends through about 300 GHz In this frequency
neither muscular nor neural cells depolarize.
• RF Electrosurgery requires the creation of an electrical circuit that includes the two electrodes,
the patient, the ESU, and the connecting wires.
• The ESU converts electrical energy drawn from the mains supply to a high frequency current.
• This high frequency current is passed through a supply cable and a handle to an active spot
electrode.
• At the point of application, this electrode builds up a highly concentrated field in the tissue
surrounding the contact point.
• The concentration of energy within a small area produces the desired electrosurgical effect in
the region around the active electrode.
• As the energy is conducted through the patient to a neutral electrode, in contact with a large
surface. (Therefore in the vicinity of the neutral electrode, there is, as is intended, no thermal
effect.)
• The electrical circuit is completed by the neutral electrode's connecting cable

12. • Joules 5th Law
 electrosurgical instruments are based on the principle of converting
electrical energy into heat
 the relationship of the amount of heat to the electric current (I), the
ohmic resistance (R) and the duration (t) is expressed:
𝐻 = 𝐼2 𝑅𝑇
• Burn
𝐵𝑢𝑟𝑛 =
𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑥 𝑇𝑖𝑚𝑒
𝐴𝑟𝑒𝑎

13. • Denaturation
Temperatures above 45°C cause a breakdown in the structure of living
tissue and disruption of the function of protein molecules.
• Coagulation
Temperatures of 60 – 70°C in the area around the active electrode lead to
a slow boiling of the intra-cellular fluid through the cell membrane.
A "welding effect" is initiated which stops the bleeding.
The vessel walls near the electrode are fused together by the protein
clotting caused by the heat
• Electrotomy
Temperatures of above 100°C in the region around the active electrode
lead to the rapid evaporation of the fluid within the cell membrane.
cell membrane ruptures forming vapour around the electrode.
Impact of current

14. Coagulation Electrotomy

15. Types of ESU
1. Monopolar
• Only one electrode is mounted on the device (Active Electrode)
• Large dispersive electrode (Patient Return Electrode) that is
also attached to the ESU
• The narrow active electrode concentrates the current (and
therefore the power), at the designated site.
• Two modes : Cutting and Coagulation
• High power output, peak voltages and rated load than bipolar
type.

16. Monopolar Electrosurgery

17. 2. Bipolar
• Both electrodes mounted on the device
• Usually located on or near to the distal end so that only the
tissue located between
the two electrodes is included in the circuit.
• Patient Return Electrode is absent.
• Three types of operations
• Precise
• Standard
• Macro

18. Bipolar Electrosurgery

19. Output Characteristics at Different modes

20. Modes of Operations of Monopolar ESU
• Cut
• vaporize or cut tissue. This waveform produces heat very rapidly.
• Coag
• the duty cycle (on time) is reduced.
• This interrupted waveform will produce less heat.
• Instead of tissue vaporization, a coagulum is produced.
• Blend
• Produces cutting effect with hemostasis
• Not a mixture of both cutting and coagulation but rather a
modification of the duty cycle.
• A lower duty cycle produces less heat

22. The Front Panel of Force FX 8C ESU

23. The Rear Panel of Force FX 8C ESU

24. REM System
• Renewable Energy Management System
• REM system continually monitors the heat build-up under the
grounding pad
• If the system detects excess heat build-up it will shut off the current
flow to prevent patient injury
• REM Patient Return Electrode is connected to the patient and then
to the generator.
• REM indicator illuminates Green
• If the Patient Return Electrode is loosened or removed REM alarm
goes off and REM indicator illuminates Red.

25. INSTANT RESPONSE TECHNOLOGY
• Instant Response technology features an advanced feedback
system that recognizes changes in tissue 200 times per
second
• And adjusts voltage and current accordingly to maintain
appropriate power.
• This provides the instrument with a high Power Efficiency
Rating (PER)

26. Patient Return Electrode
• Designed with an adhesive to facilitate continuing contact with the patient
and prevention of a clinically significant local thermal effect.
• if there is partial detachment, the current (or power density) will increase,
and the dispersive electrode can become “active” and capable of creating
thermal injury, often called a burn.

27. • To avoid this they are designed in the form of a “split pad” (which
effectively is two dispersive electrodes in one) to measure the impedance
at the level of the electrode.
• A difference in the measured impedance in the two dispersive electrodes
will generally reflect partial attachment (or detachment) and the machine
will not start.
• Surface area impedance can be compromised by: excessive hair, adipose
tissue, bony prominences, fluid invasion, adhesive failure, scar tissue, and
many other variables.

28. Special Considerations: Patients with
• Implanted pacemaker
• Implanted automatic defibrillator
• Cochlear Implant
• Implanted Bone Growth Stimulator
• Body Jewelry
• Offender monitoring ankle bracelets
• Orthopedic implants (total hips, etc)

29. Safety
• Inspecting the machine for broken wires before use.
• If alcohol-containing prep solutions are used (ex: Duraprep, Prevail) the
prepped area must be allowed to dry completely before using ESU to
minimize fire risk.
• Using lowest possible power setting at all times.
• Keeping active electrode pencil in non-conductive holder when not in
use. This prevents accidental activation.
• No part of the patient should be touching any grounded metal objects
• Not allowing activating in close proximity or direct contact with another
instrument.
• The return electrode pad must be checked after the patient is
repositioned.

30. References
• Cordero, I., 2015. Electrosurgical units – how they work and how to use
them safely. [Online]
Available at: http://www.cehjournal.org/article/electrosurgical-units-how-
they-work-and-how-to-use-them-safely/
[Accessed 11 July 2016].
• Munro, M. G., 2012. Fundamentals of Electrosurgery, s.l.: Springer.

31. Thank You!!!