Physical Bases of Electrosurgery : Physical Bases of Electrosurgery Dr. Mohammed Abdalla
Egypt, Domiat general hospital HISTORY OF ELECTROSURGERY : HISTORY OF ELECTROSURGERY 3000 B.C Egyptians used heat to treat tumors
Beginning of XIX century : discovery of electrocautery
1875: bottini used galvanocautery for prostatectomy
1889 : heniry simbthon built the first high frequency generator.
1890 : the action of high frequency alternating current on human tissue was demonstrated. Slide 3: The use of a flow of electrons, pushed through a biological tissue, generates heat and thus a series of thermo-destructive effects. Slide 4: thermo-destructive effects are either section and/or coagulation DEFINITION OF ELECTRICAL TERMS : DEFINITION OF ELECTRICAL TERMS current: ampere volume of electrons/sec flow.
voltage: volt strength with which electrons are pushed
impedance: ohm resistance to flow
power: watt "work" produced by electrons flow
energy: joule "work" produced/t There are two kinds of current : There are two kinds of current Slide 7: direct current, characterized only by the variability of its intensity, it is never used in
Electro-surgery Slide 8: alternate current, characterized by its frequency, that is by the number of oscillations per time unit
(1 oscillation/sec = 1 Hertz). Electro cautery and Electro surgery : Electro cautery and Electro surgery Electro cautery
Direct current through a high resistance metallic conductor
It is essentially application of heat and burning of tissue Electro surgery
High Frequency Alt. Current through living tissue
Manipulation of electrons to produce heat within the cells to destroy the tissue alternate current : alternate current We can distinguish
low frequencies from 0 up to 3000 Hz
medium frequencies from 3000 up to 50000 Hz
high frequencies > 50000 Hz. the tissue effects of electro-surgery : the tissue effects of electro-surgery The cut is obtained with a low voltage and a high continuous frequency .
The coagulation is obtained with high voltages with an intermittent frequency. Slide 12: Pure cut Blended cut Blended cut The pure cut is obtained with a low voltage and a high continuous frequency . Slide 13: a cut wave, is an uninterrupted continuous wave.
a coagulation wave is An interrupted sinusoidal wave, whose current is released in pulses (only in 6% of the time, while for the remaining 94% ESU does not release current any longer), .
a blended current modulation of these two kinds, with several on-off cycles. alternate current : Cut current Coagul. current Blended current alternate current cut current : supplies high frequency current, continuos non interrupted, with low voltage cut current Slide 16: supplies an interrupted-alternate current, with high voltage . in this case the electro-generator supplies power only in 6% of the time (on) while in the remaining 94% the generator does not produce power (off) allowing the electrode cool. These on-off cycles are called duty-cycles. Coagul. current blended current : a continuous cut current which is interrupted by creating several on-off cycles (duty cycles). blended current blended current : Blend1 means that ESU supplies power only in 80% of the time (on) while in the remaining 20% the generator does not produce current (off) (Vp-p=1200)
Blend2 means that ESU supplies power only in 60% of the time (on) while in the remaining 40% the generator does not produce current (off) (Vp-p=1500)
Blend3 means that ESU supplies power only in 50% of the time (on) while in the remaining 50% the generator does not produce current (off) (Vp-p=2000) blended current Electro-surgical systems : Electro-surgical systems Slide 20: Electro-surgical systems can be divided into two kinds:
monopolar /and bipolar. Slide 21: the distance between the two poles can be of many
centimeters , so the patient is completely included in the circuit Monopolar circuit Slide 22: the distance between the two poles (the
jaws of the forceps) is usually a few millimeters. bipolar circuit Monopolar : Monopolar the current flow passes through an "active" electrode, crosses the patient’s body and returns to the electro-generator through a suitably sized (>20 cm2 ) "passive" electrode which is normally applied on the skin surface Monopolar : In monopolar mode the patient’s body is completely included in the circuit Monopolar Monopolar : High frequency current flows from the active electrode through the patient’s body to the patient plate.
It produces heat in the tissues proportional to the electrical resistance of the tissues and the current density.
Fatty tissues have a high resistance.
Electrosurgical Cutting with / without Coagulation and Desiccation / Fulguration all are possible.
Patient plate is required. Monopolar Patient Plate : Patient Plate It is the negative pole / passive electrode through which the current returns to the machine after passing through the patient.
The current density at the patient plate is inversely proportional to the contact area.
A 50% decrease in contact area near the patient plate will produce two fold increase in current intensity and a four fold increase of heat. Patient Plate : Patient Plate Hence the Patient plate should be as large as possible.
It should be applied to a wide area of electrically more conductive tissues like muscles. ? ? Patient Plate : Patient Plate Current does not flow uniformly to the patient plate.
Its density is higher at the corners and edges of the patient plate nearer to the the active electrode.
Hence the patient plate should be placed such that the longer edge points to the active electrode. ? ? Patient Plate : Patient Plate It should make maximum and complete contact with the electrically conductive surface of the body to avoid burns.
Metal plates not to be used. Large Silicon rubber plates should only be used.
Simple patient plates are not so simple. Bipolar Diathermy : In bipolar mode, the electron flow passes through a forceps jaw, crosses the tissue interposed in the forceps and returns to the electro-generator through the second jaw. Bipolar Diathermy Bipolar Diathermy : Bipolar Diathermy Current flows locally through a small portion of tissue between two electrodes of the bipolar forceps Bipolar Diathermy : In bipolar mode the patient’s body is not included in the circuit Bipolar Diathermy The bipolar coagulation : The bipolar coagulation The bipolar coagulation decreases the risks of electrical accident but not the risk of burns of a tissue close to the coagulated area.
The two forceps jaws close the circuit when they are clamped on the tissue to coagulate.
If we clamp the forceps without any interposition of tissue, the current activation will lead to a circuit with a considerable increase in temperature at the forceps end The bipolar coagulation : Since bipolar coagulation enables to reach very high temperatures (up to 340°C) we must take into account that there is a moderate thermal damage until a distance of one centimeter from the forceps.
In case of big vessel coagulation (uterine arteries, pelvic-infundibular arteries), the surrounding tissue damage is essential in order to obtain a shutting of the vessel by the simple coagulation. The bipolar coagulation The bipolar coagulation : A too short application leads to an insufficient coagulation, but a too long coagulation causes an adherence of the tissue to the forceps and an excessive peripheral extension of tissue desiccation.
the application of an ammeter could be very useful; after complete desiccation the electricity will no longer pass so the ammeter will warn that the tissue desiccation has been "electrically" completed. The bipolar coagulation Slide 36: cut coagulation fulguration Effects of electrosurgery
on tissues Slide 37: current a low voltage and
a high continuous frequency electrode needle- kind Electro-surgical systems monopolar technique Non touch cut Slide 38: The current condense at the electrode’s end .
By approaching the electrode’s end to the tissue, without touching it, a voltaic arc between electrode and tissue occurs,causing the tissue vaporization.
Since the voltage is low and the current is rapidly dissolved and conveyed to the passive electrode (return plate), the side thermal damage will be small. cut Slide 39: The quick raising in the tissue temp. above 100°C leads to the rapid transformation of intra-cell water into vapour with the consequent "explosion" of the cell; thus the heat is dispersed and is not passed on the adjacent cells which remain intact. cut Slide 40: coagulation : the cell is dehydrated and the proteins are denatured but not destroyed.
Desiccation: is the process where temperature reaches 90°C with a consequent dehydration without protein denaturation.
From the clinical point of view, we normally talk about coagulation. coagulation Slide 41: current A high voltage and
intermittent frequency electrode wide surface
electrode Electro-surgical systems Monopolar
a real cut
or blend current technique touch coagulation Slide 42: spray coagulation or black coagulation,
the tissue is superficially carbonized, in consequence of voltage currents (coag), with a very short duty-cycle (6%), applied by means of a wide electrode (sphere-shaped) in no contact mode.
that is by keeping the electrode at a few millimeters far from the tissue. The electric arc leads to a quick and sudden raising of tissue temperature (>200°C). fulguration Variables changing the tissue effects of electro-surgery : Variables changing the tissue effects of electro-surgery Slide 44: tissue effects of electro-surgery are
influenced by : power Electrode shape nature of the electric wave Tissue kind Current application time power in monopolar mode
is usually three times higher
than in bipolar a thin, needle-shaped electrode
will produce a high power density Voltage and frequency directly correlated to the time
during which the electrode is
kept in contact with the tissue Adipose tissue is most resistant
vessels are least resistant The power : The power The power in monopolar mode is usually three times higher than in bipolar mode;
that is why the bipolar mode don't allow the power density required to obtain a cut effect. The nature of the electric wave. : The nature of the electric wave. a low voltage and a high continuous frequency produce cut effect.
high voltages applied with an intermittent frequency produce coagulation effect. electrode shape : electrode shape a thin, needle-shaped electrode will produce a high power density (cut effect).
a wider electrode (spatula-shaped),with same energy in contact with the tissue, will dilute the electron density on its end, temperature will increase more slowly and gradually, obtaining coagulation effect. Kind of tissue : Kind of tissue Without changing the electric parameters, we can obtain effects linked to the way in which we apply the energy.
For example, to perform a section we put the tissue in tension, activate the current and touch the tissue, while to obtain coagulation we do not tighten the tissue, touch it and after that we activate the current. Kind of tissue : some tissues (i.e., veins) explode, giving an effect opposite to the desired one. In these cases it is necessary to use a lower power and to grip with the forceps a bigger tissue mass. Kind of tissue Current application time : Current application time The amount of energy "administered" to a tissue is directly correlated to the time during which the electrode is kept in contact with the tissue. For example, during an electro-surgical section, if the electrode is slowly moved, there will be a greater side thermal damage. Of course, the longer the energy application time, the greater the risks at a distance from the coagulation or cut point . Thermal damage due to electrical diversion : Thermal damage due to electrical diversion Alternate Site Burn : Alternate Site Burn Slide 53: while the active electrode is near another metal instrument. The secondary instrument will become energized. This energy will seek a pathway to complete the circuit to the patient return electrode. There is potential for significant patient injury direct coupling. Thermal damage due to electrical diversion : direct coupling.
capacitive coupling. Thermal damage due to electrical diversion direct coupling insulation failure : direct coupling insulation failure Electrical conduction due to accidental contact with non insulated tool .
Insulation defect of the active electrode cause burn ( direct coupling ) Involuntary or accidentally prolonged activation of the active electrode. capacitive coupling Skin burn on alternative or same site of dispersive electrode ( plate). Thermal damage on the level of passive or earthed electrode. : Thermal damage on the level of passive or earthed electrode. The thermal damage on the level of earthed electrode has nowadays become rare as the modern generators use insulated circuits continuously monitor the return current
In case of an even partial detachment of the plate, the REM-equipped generators block the electricity supply, generally warning with a sound signal. Thermal damage due to direct or capacitive coupling : Undetected thermal injury should be suspected in patients who present with symptoms suggesting organ perforation or peritonitis following laparoscopic monopolar electrosurgery. Thermal damage due to direct or capacitive coupling Thermal damage due to direct or capacitive coupling : Unlike injuries that occur within the visible surgical field, stray current injuries are generally not immediately visible at the time of surgery. Since the surgeon cannot directly observe the burn Thermal damage due to direct or capacitive coupling Thermal damage due to direct or capacitive coupling : clinically significant symptoms of the complications of thermal burns are often delayed sometimes for several days after the initial surgery placing a patient at risk of delayed diagnosis and treatment. Thermal damage due to direct or capacitive coupling Slide 60: capacitive coupling Slide 61: Insulation failure can result in an unintended burn
to non-targeted tissue Slide 62: Energy can be transferred through intact insulation by means of capacitive coupling. Most potential problems can be avoided by following these simple guidelines: : Most potential problems can be avoided by following these simple guidelines: Inspect insulation carefully
Use lowest possible power setting
Use a low voltage waveform (cut)
Use brief intermittent activation vs. prolonged activation
Do not activate in open circuit
Do not activate in close proximity or direct contact with another instrument
Use bipolar electrosurgery when appropriate
Select an all metal cannula system as the safest choice. Do not use hybrid cannula systems that mix metal with plastic.
Utilize available technology, such as a tissue response generator to reduce capacitive coupling or an active electrode monitoring system, to eliminate concerns about insulation failure and capacitive coupling. Diathermy in Gynaecology- General Use : Diathermy in Gynaecology- General Use Diathermy in Gynaecology- General Use : Diathermy in Gynaecology- General Use During surgery ( Open & Laparoscopic) for Cutting & Haemostasis.
Cutting is more precise.
Haemostasis is better achieved.
Can be used in LSCS. No effect on the fetus.
Take care while working near vital structures.
Apply the point first , then switch on the current.
Monopolar & or Bipolar can be used. Diathermy in Gynaecology- General Use : Benign Cervical Lesions-
CIN (LEETZ / LEEP)-
Ovarian Drilling in PCOD-
Hysteroscopic surgery- TCRE, sub mucus Myoma, Septum Resection Diathermy in Gynaecology- General Use Electro surgery for Benign Cervical Lesions : Electro surgery for Benign Cervical Lesions Coagulation / Desiccation / Cutting can be done as the case may be, using Monopolar diathermy in the following conditions.
Erosion & Chronic Cervicitis - Avoid endocervix
Mild degree Cx. Tears
Amputation Electro surgery for Tubal Sterilisation : Electro surgery for Tubal Sterilisation Laparoscopic sterilisation should usually be done by a single puncture and use of monopolar coagulation as described by Wheeless [Wheeless 1992]. Female Sterilisation methods : Method 24.8 7.5 17.7 36.5 20.1 18.5 Pregnancy Probability per 1000 procedures Female Sterilisation methods 7.5 Electro surgery for PCOD : Electro surgery for PCOD For PCOD, Laparoscopic Ovarian Drilling (LOD) by Diathermy is cost effective than Laser vaporization.
It is done by passage of 40 W current for 4 seconds in 4 places on each ovary with a monopolar needle.
Advantages of ovarian drilling-
Sensitizes the ovary to F.S.H.
Less monitoring than Gonadotrophin therapy.
Unifollicular growth, No risk of OHSS and multiple pregnancy.
Low rate of abortion.
One treatment may result in many ovulatory cycles.
Ovulation rate 70 – 80% in failed C.C. cases, Pregnancy rate 60%
To reduce periovarian adhesions liberal peritoneal lavage should be done. Early second look laparoscopy and adhesiolysis may be required. Electro surgery in Endometriosis : Electro surgery in Endometriosis During surgery for endometriosis, small and multiple lesions on the peritoneum are better dealt with electrocoaglation.
Care should be taken while working near vital structures.
Though both monopolar and bipolar may be used, bipolar is safer and preferable. Electro surgery for Myoma : Electro surgery for Myoma Myolysis - involves delivering electric current via needles (Monopolar) to a fibroid at the time of laparoscopy.
It offers a better alternative to myomectomy with minimal blood loss to deal with myomas particularly multiple ones. Hysteroscopic Electro surgery : Hysteroscopic Electro surgery Endometrial ablation - Trans Cervical Resection of Endometrium (TCRE), with wire loop or roller ball is a simple office procedure.
It can be the first line of surgical treatment in Menorrhagia (DUB) and may avoid hysterectomy.
Other hysteroscopic electrosurgical procedures are -Electrovaporisation of sub mucus Myoma.
Septum Resection Thank you : Thank you