2. Electrosurgery and Cautery are not
synonymous….
Electrosurgery (ESU)
• Here, high frequency(RF) alternating
current(AC) is used to raise the
intracellular temperatures, so that
vaporization (cutting) or the combination
of desiccation and protein coagulation
can be achieved.
• In this, since electric current is used to
cut the tissues, force required is very
less.
• Wound healing time is lesser than
cautery, and different effects can be used
for performing cutting and/or coagulation.
Cautery
• The word cautery is derived from the
greek word Kauterion, in which,
destruction or denaturation of tissue is
achieved by passively transferring heat
from a heated instrument (resistant metal
wire).
• DC/Low frequency AC is used to achieve
the desired effect.
• Cutting was done using conventional
knife, because of which high force was
required
.
3. HISTORY OF CAUTERY
• Ancient Egyptians (circa 3000 BC) described the use of thermal cautery to treat diseases
such as ulcers and tumors of the breast
•
• Hippocrates (469-370 BC) used heating to destroy a neck tumor.
• Albucasis used a hot iron to control the bleeding process.
• The first form of electrical energy used in medical therapeutics was direct current (DC).
Benjamin franklin and John Wesley described this first in the mid-eighteenth century. DC
was used to heat an instrument that was then applied to tissues, which caused an effect
secondary to passive heat transfer. The coagulation and desiccation of the tissue which
resulted from this procedure is a form of cautery.
• In the early nineteenth century, French Physicist Becquerel also demonstrated
electrocautery using electricity (DC) to heat a wire needle.
5. History of Electrosurgery..
• In the year 1891, D’Arsonoval played a part in an important development in the field of
electro-surgery. He discovered that, high frequency alternating current could be passed
through the body without electric shocks. At a frequency greater than or equal to 20kHz,
AC passing through the body does not produce muscle stimulation.
6. History of Electrosurgery continued..
• In 1893, D’Arsonoval designed capacitors, which were later modified by Oudlin, and
developed a high-voltage discharge in the form of sparks that could arc, and superficially
destroy nearby tissues. This process was termed as fulguration (fulgurate means to flash.).
• Doyen described the use of bipolar instruments to perform coagulation of tissue in the year
1909.
• In 1907, De Forest invented a triode-containing vacuum tube which could amplify electrical
signals and broadcast RF signals. This proved as a stepping stone for the production of
high-frequency continuous AC required for coagulating and cutting(linear propagation of
vaporization).
• 1924 was the first time, Wyeth used this vacuum-generated, alternating current to cut
tissue in human beings.
7. The Men who developed the ESU…..
Bovie and Cushing !!!!
• William T. Bovie, a Physicist and Harvey W. Cushing, a neurosurgeon are often credited
with the invention of the electrosurgical generator.
• In the year 1926, Cushing used Bovie’s side-by-side ESU’s- one, a vacuum tube-based
design for cutting, the other, a spark gap version for coagulation to perform neurosurgery
on a patient with an otherwise inoperable vascular myeloma.
• Solid state generators and isolated circuits were invented in the 1970’s which produced
lower voltage, more consistent waveforms, and their isolated circuitry allows for the
creation and use of systems for improving safety such as impedance monitoring.
• Some customers use the word Bovie and Electrosurgery synonymously.
8. Development of Endoscopic and Lap.
procedures using ESU
Endoscopically directed surgeries was first performed in the year 1910, where-in Kelly
described Beer’s use of a monopolar instrument to fulgurate bladder tumors using a
cystoscope.
• The first attempt at using laparoscopically directed electrosurgery was was reported by
Fervers in 1933, who described electrosurgical adhesiolysis.
• In 1941, Power and Barnes reported the first human performance of laparoscopic
electrosurgical female sterilization using a monopolar instrument.
• In the 70’s and the 80’s, Surgeons believed that, activated monopolar instruments can arc
long up to variable distances and cause substantial lateral thermal damage. However, in
1985, Levy and Soderstrom demonstrated that, under reasonable conditions, such injuries
were not frequent, and all the bowel injuries were secondary to physical (caused by trocar
cannula systems), and not electrical trauma.
• Fragenheim and Rioux developed and popularized use of Laparsocopic Bipolar
instruments in the early 1970’s.
9. Why Electro-Surgery???
• RF-Electrosurgery is used in more than 80% of surgical procedures, and many of them are
done in an out-patient environment.
• Using the conventional knife to cut tissues requires higher force, and subsequently more
wound healing time.
• Application areas become wider when ESU is used. These include Dermatology, Plastic
Surgery, Gynecology, Ophthalmology, Dental, Urology, Veterinary, Oncology, Cardiology
and many more.
• In that case, every Dr.’s clinic becomes a potential customer for an ESU manufacturer.
• With the right quality and the ability of the ESU to deliver the correct amount of power
makes this topic an interesting one.
• If the weight of the unit is less than or equal to 6kg’s, the surgeon can carry the unit to
different hospitals to perform surgeries.
10. Fundamentals of Electro surgery
• Understanding the principles of ESU is very important, which will play a vital role in the safe
and effective use of the equipment on a patient’s body.
• During RF-Electrosurgery, the electromagnetic energy is converted in the cells into kinetic
energy first, and then to thermal energy.
• The medium of current is high frequency AC, as line frequencies (50HZ) can cause
stimulation of the neuromuscular system, i.e., it can depolarize the muscle and neural cells.
• Because the frequencies used for surgery are in excess of 300 KHz, these units are also
termed as Radio frequency- Electrosurgery. (Fig. showing the electromagnetic spectrum)
11. Fundamentals of Electrosurgery
Contd…
RF- Electrosurgery can be classified into 2 types taking into consideration the return path
these techniques follow.
• In the Monopolar type, the narrow active electrode concentrates the current (power) to the
desired surgical site, and the large dispersive electrode (neutral electrode/patient plate),
placed away from the surgical site(any location near the surgical site, for eg. If the surgery
is done on the abdomen, it should be placed on the back/buttock, whichever is
comfortable) distributes the current over the larger area, and returns to the generator,
which helps in preventing burns to the patient’s skin. In the monopolar system, the entire
patient is involved in the circuit.
• In the Bipolar type, both electrodes are mounted on the device (bipolar forceps) , located
on or near the distal end, so that only the tissue grasped between the 2 poles gets affected.
In this, only the tissue interposed between the electrodes is included in the circuit.
12.
13. Why is it called
RF Electro-surgery??
There are 2 basic mechanisms by which RF current is used to elevate/rise tissue
temperatures to achieve the desired effect.
• In the first mechanism, electromagnetic energy is first converted into mechanical, which is
then converted to thermal (heat) energy with the help of frictional forces. The second
mechanism is resistive heating, where, current flowing across a resistor causes an
increase in the temperature of that resistor. The third mechanism is an indirect method of
heating of tissue, where, the tissue adjacent to the one being touched gets affected by RF
current, which is also termed as conductive heat transfer.
• Cells contain electrically charged particles/ ions in the form of atoms and molecules.
Cations are positively charged, whilst anions are negatively charged particles. When a DC
is applied to the cell, the ions move towards oppositely charged electrode, which is called
the galvanic effect and has no medical purpose. On the contrary, when an AC is applied to
the cell, the ions migrate to the opposite poles, but they do not maintain a single orientation
within the cell. They oscillate in conjunction with the differing polarity of the output.
• If the frequency of the AC is low (20-30KHz), the RF current will depolarize the muscles
and nerves because of which an action potential occurs, which will result in muscle
fasciculation and pain. This effect is known as the faradic effect.
14. Why is it called RF Electro-surgery
contd..
The depolarization process is initiated via the voltage gated sodium and potassium
channels in the neural and muscular cell membranes.
• The interesting thing to note here is that, neural and muscular stimulations do not take
place if the current switches very quickly (100KHz-3MHz), also called as Radio- Frequency
(RF). When such as high frequency current is applied across a cell membrane, the pulse
duration is so short that the sodium and potassium ionic channel gates do not get opened,
which is why the process of depolarization is not observed. In this case, the
electromagnetic energy is converted to mechanical energy, as the ions (cations & anions)
rapidly oscillate within the cellular structure. Thereafter, this mechanical energy is
converted into thermal energy with the help of frictional forces. This thermal (heat) energy
helps in elevating/rising the cellular/ tissue structures and provide the desired tissue
effects.
• When either AC or DC flows through a resistor, the resulting effect is the generation of
heat, i.e., because there is resistance/impedance provided to the flow of current, thermal
(heat) energy is generated, which was explained effectively by joule’s, also known as the
joule’s law (Q= {I^2×R×t}).
17. Some Basics Re-visited…
Current(I) Flow of electrons past
a point in the circuit
per unit time
Amperes
(coulombs/time)
Voltage (V) Difference in electrical
potential between 2
points in the circuit,
i.e., force required to
push a charge along
the circuit
Volts
(Joules/coulomb)
Impedance/Resistanc
e(R)
Degree to which a
circuit resists the flow
of electrons
Ohms
Power(P) Amount of energy per
unit time. Product of
V&I
Watts (Joules/Second)
Energy Capacity of a force to
do work
Joules
18. Some Basics Re-visited contd….
• Below equations play a vital role in the understanding of RF-ESU principles and
mathematical analysis of impact on the tissue.
• If the Voltage increases and impedance remains constant, current tends to increase. If
Voltage is kept constant and impedance increase, current decreases. Hence, modern
generators sense the increased impedance and increase the voltage, thereby keeping the
power constant.
Ohm’s law Current (I)= V/R
Voltage (V)= IR
Impedance (R)= V/I
Power (P) P=VI
P= (V^2)/R
P= (I^2)R
Energy(Q) Q=Pt
19. Understanding Current Density…
Electrosurgical impedance/resistance is impacted by a number of factors throughout the
circuit, but, tissue characteristics are the most important ones. Hydrated (wet) tissue
contains ions and has the lowest impedance, while dehydrated(desiccated) tissue has a
lower ionic content, and has a higher impedance.
• Power rises exponentially with increases in voltage and decreases inversely with increases
in resistance/impedance as per the equation (P=(V^2)/R).
• An important concept to be understood here is about the power or current density.
• Current density is the amount of current per unit area, and power density is directly
proportional to the square of current density.(current density=(current/area)).
• Hence, a higher current density concentrated at the tip of an electrode is used to heat and
vaporize cells, while a lower current density desiccates and coagulates the tissue.
23. Cut & Coag. waveforms
ESU performs 2 main operations – Cutting & Coagulation.
• The Cutting waveform is a continuous sine wave signal, letting the surgeon do a pure cut
on the tissue he/she is operating upon. The Crest Factor of such a waveform is very low (
1-2).
• The Coagulation waveform on the other hand has a modulated, dampened, high voltage
and a very low duty cycle signal. Typically the current in this mode will be `on’ 6% of the
time, referred to a 6% duty cycle.
• This helps in delivering power in bursts as compared to the cutting waveform.
Note:- Duty cycle describes the percentage of time the ESU generator is producing a
waveform or supplying current. If it is 80% of the time, it means 80% duty cycle.
24. 1)This shows a typical
cut and coag waveform.
2) The first waveform is
a continuous sine wave
and has no duty cycle.
3) The waveform below
has a modulated,
dampened, high voltage
and a low duty cycle
waveform (on for 6% of
the total time).
25. Cutting & Coagulation
In cutting or transection of the tissue, the cells
start vaporizing, i.e. the liquid gets converted
into steam. This is achieved with a continuous,
low-voltage waveform using a monopolar
instrument with a narrow, pointed blade shaped
electrode. The generator is activated, and
because of the high power density (current
concentration) at the tip, the tissue starts
heating up faster, reaches ≥100 degree Celsius
and separates/cuts the tissue. Usually, the edge
of the electrode is used in contact, since it can
concentrate more current at a single location,
and help in cutting purpose.
In this process (coagulation &
desiccation/dehydration), tissue
temperatures reach anywhere between 60 &
95 degree Celsius.
• When the tissue temperature is about 60
degree Celsius, the cellular fluid starts
dehydrating (desiccation/dehydration), but
the cellular structure is altered but not
destroyed, as seen in vaporization (cutting).
• The terms coagulation and desiccation are
used synonymously by some of the
manufacturers, because the local
temperature in both the techniques do not
go above 95 degree Celsius.
• Usually, the flat end of the monopolar pencil
is used for coagualation, as the area is
more, because of which the current
concentration at the site is less(distribution
increases due to larger area of the electrode
tip), and the heat delivery to the tissue would
not be as high as the cutting mechanism.
26. Coagulating with low voltage output (cut) waveform results in a predictable
zone of coagulation with higher quality and consistency than achieved with
the pure `coagulation’ output.
27. The intermittent output from the 6% duty cycle waveform causes a brief and superficial
elevation of tissue temperature, sufficient to cause focal coagulation, desiccation, and in many
cases carbonization. Hence, the next a burst or an arc returns to this area, the tissue
impedance has already increased, and the current is blocked or gets diverted to a zone of
lesser impedance. Such waveforms cannot really have deeper coagulation effect.
28. In fulguration, high-voltage modulated outputs (coag) is used. Arcs are produced between the
electrode and the tissue without having physical contact between the two. The desired effect is
achieved if the tissue temperatures (local temperature) rise to above 200 degree Celsius and can
maximum temperatures of 400 degree Celsius. It is also called as black or spray coagulation. It
is usually preferred when bleeding of small blood vessels like capillaries or arterioles has to be
prevented over a larger surface area. The depth of coagulation effect is about 0.5mm.
Spray
coagulation/
fulguration
29. What is a blended waveform
or blend?
Originally, blended outputs were created by mixing/combining/blending waveforms from 2
physically different generators that produced the continuous low voltage and the modulated
high voltage waveforms.
• The modern ESU’s create blended outputs by producing modulated/interrupted versions of
the pure cut (continuous sine wave) waveforms.(Figures shown in the next slide).
• When the current in interrupted (impeded) , voltage should be increased to keep the
wattage (power) constant.
• Blended currents are actually modulated low-voltage waveforms, and not the mixture of cut
& coag waveforms.
• Duty Cycle for blended waveforms vary 50-80% depending upon the make.
• As the duty cycle reduces, voltage starts rising provided the power is constant.
31. Effects of Temperature
on tissues..
The normal body temperature is 37 degree Celsius, but when we have infections, the body
temperature rises to about 40 degree Celsius. At this temperature, there is no damage to
the structure of the cells and tissues. However, when the temperature reaches 50 degree
Celsius, cell death will occur in approximately 6 min, and if the local temperature reaches
60 degree Celsius, cellular death is instantaneous.
• Between 60 & 95 degree Celsius, 2 simultaneous processes occur that is of major
importance to the surgeons. The first is protein denaturation which happens after the
impact of temperature on the hydro-thermal bonds between protein molecules. When the
local temperature is as low as 60 degree Celsius, the bonds break immediately, but tend o
reform as the temperature starts cooling down. This leads to a homogenous coagulum, and
the process is typically called `coagulation’. The other effect is desiccation or dehydration
as the cells lose water through the thermally damaged cellular wall.
• If the intracellular temperature rises to 100 degree Celsius or more, the liquid on the cell
wall gets converted into steam(vaporization. When the local temperature reaches 200
degree Celsius or higher, the organic molecules are broken down in a process called as
carbonization. This process is sometimes called as black coagulation, because the carbon
molecules formed have a black/brown appearance.
32.
33. Parameters impacting the tissue
effects in Electro-Surgery…
• 1) Power density:- It is the total amount of power (wattage) delivered per unit area from the
electrode either to adjacent areas of the tissue or at the site itself. Combination of the size
& shape of the electrode and the power settings on the ESU output decide the intensity of
this factor.
• 2) Electrode Surface area:- Power density will increase if the electrode surface area in
contact with the tissue is minimal (edge part of the blade electrode), and power density will
be lesser if the electrode surface area is higher (flat part of the blade electrode). The edgy
part can be used for cutting (vaporization) & the flat part can be for coagulation &
desiccation purposes. If the edgy part of the blade is used for cutting purposes, the flat part
may come in contact with the edge of the incision as the electrode is passed through the
tissue, giving an additional degree of coagulation to the adjacent areas. Ball electrodes are
usually preferred for fulguration/spray as the surface area of the ball reduces the power
density and provides the desired spray effect.
• 3) Tissue Impedance/Resistance: -. Tissues such as calloused skin, bone, fat or any
already desiccated tissue will impede the flow of current and the desired surgical effect
cannot be achieved. If cutting has to be achieved on a high impedance tissue, the voltage
is raised by increasing the power output or duty cycle of the waveform is decreased.
34. Parameters impacting the tissue
effects in Electro-Surgery contd….
• 4) Waveforms: - The effect of RF energy on tissue is also related to the waveform of the
output of the ESU. The peak voltage of the coagulation waveform is usually 3 times higher
than the peak voltage of the cut waveform. Since the voltage associated with the
coagulation mode is very high, there is a possibility instrument installation breakdown and
current diversion. High Voltage, Modulated and Dampened waveforms are used for
fulguration/spray purposes. Technically, spray has the lowest duty cycle, and hence the
highest voltage, and it gives higher lateral thermal damage than fulgurate. For cutting
tissues like fat, scars and tissues that have already been desiccated or coagulated, the
surgeon can use the blend setting on the ESU which has better cutting effect for high
impedance tissues along-with good haemostasis ability. The low voltage continuous
waveforms are best suitable for efficient cutting/coagulation/desiccation. Such waveforms
provide homogenous and deep coagulation & desiccation due to the low voltage and
continuous output.
• 5) Activation time:- The amount of energy delivered to a volume of tissue depends upon the
time for which the electrode is in contact with the tissue. In cutting, when the electrode is
moved slowly through the tissue, a greater degree of collateral thermal injury is observed.
36. As shown in the figure, if the tissue temperature is increased to 60 degree Celsius but
less than 100, cellular water is lost (desiccation/dehydration), and if the temperature
reaches 100 and above, vaporization takes place, i.e. the cell explodes in a cloud of
steam, ions and organic matter.
41. What is Vessel Sealing and why it is
required….
• As the name suggests, vessel sealing (bipolar technique) involves sealing blood vessels
(veins, arteries, tissue bundles etc.) and then cutting the sealed part so that the blood flow
can be occluded in that particular direction. In this method, the elastin and collagen fibres
get denatured, and form a white colour substance, which can be termed as a seal. This
technique is done to prevent surgical suturing, which can be very time consuming for the
surgeons, and the post-operative pain is lesser in vessel sealing. The amount of pressure
the sealed vessel can with-stand is much higher than the physiologic pressure.
• Two main parameters in vessel sealing is high pressure and high current. The tissue has to
be held under very high pressure by closing the ratchet (lock) at the proximal end of the
accessory. When the tissue under consideration is held under such pressure, high current
is delivered to the tissue which gives a haemostatic sealing of the vessel. If the current is
high (3-4A), the sealing takes happens in approximately 2-4 seconds The sealed part is
then cut with a knife or a blade. Now-a-days, we have in-built cutters which can perform
this operation.
• Some important surgeries where vessel sealing is required will abdominal hysterectomy,
Laparoscopically assisted vaginal hysterectomy, Nepherectomy, Choleycystectomy etc.
• All the vessel sealing systems available can seal vessels having diameter up to 7mm.
42. Bipolar clamp with ratchet
(lock) for vessel sealing in open
procedures.
Ratchet
(lock)
The end where the tissue is
grasped (held) under high
pressure
43. Figure on the left shows a laparoscopic vessel sealer with an in-built cutter at the proximal
end, and on the right, the distal end is the part where the surgeon holds the instrument.
(The ends have been considered wrt the tissue position.)
44. The white colour on the edges of
the tissue show the sealed part.
The sealed part have been
dissected using an in-built cutter.
The accessory is moved ahead
to perform vessel sealing on the
following blood vessels (to be
sealed).
45. As shown in the figure,
Argon gas is ionized
using electric current
(HF), which is
converted into argon
plasma. This stream of
plasma can be used
for cutting and
coagulation purposes.
The position of the
electrode can be axial
or tangential.
46. Fig. shows the polyp
structure which has to be
detached.
Fig.shows
waveforms used
for detachment
purpose. Since
excessive blood
loss is to be
prevented,
different pulses of
cutting and
coagulation are
being delivered,
which will
gradually detach
the polyp from its
base.
ENDO CUT
