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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_986_Библиотеки_им_академика_М_И_Перельмана
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Energy Devices Handbook of Laparoscopy Instruments 79
https://t.me/medicina_free
Specialized Electrosurgical Units
Harmonic Scalpel
The principle of a harmonic scalpel is that electrical current induces ultrasonic
vibration at the rate of 55500/sec (55.5 kHz) from the ultrasonic generator.
Piezoelectric crystal embedded in metal cylinders converts ultrasonic energy into
mechanical vibrations that are transferred to tissue through an active blade,
leading to movement between the range of 60-100μm that causes denaturation of
the cellular protein due to cellular friction and hydrogen bond breakdown leading
to precise coagulation or cutting effect even in thickened tissue or higher density
tissues uniformly.
Cutting in tissues is done by two mechanisms- a) stretching of tissue to the
extreme by longitudinal blade motion. b) Water vaporization and cavitation effect
in higher water content tissue like liver leading to cellular busting.
As vibrations cause coagulation, there is limited heat generation by the scalpel
blade; hence there is limited thermal damage to the nearby tissue. To avoid
collateral damage by vibration-generated heat, the vibrating blade of the probe is
to be away from the adjacent tissue.
Advanced refinements in tips of harmonic devices are progressed to reduce the
jaw's thickness, precise cutting, coagulation and limited adjacent tissue damage.
Available hand probes: ACE curved shears, scalpel, and dissecting hook for open
and laparoscopic procedures.
Uses: These are used in major gastrointestinal surgeries,specially in laparoscopic
resections and surgeries.
Advantages
●
Safety is enhanced.
●
Commonly used in laparoscopic gastrointestinal, hepatic, pancreatic and
thoracic surgery, and hand instruments are also available for a range of open
surgical procedures.
●
Vessel sealing effect of shear is up to 5mm, and the hook is 2mm.
●
Less smoke generation provides better visibility than the conventional
Electrosurgery unit.
●
There is limited lateral damage to tissue, charring and desiccation.
●
No risk of electrical injuries.
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Disadvantages
●
Slower rate of cutting and coagulation compared to conventional devices.
Inappropriate use, i.e., longer contact time, leads to tissue injury due to
overheating of the non-active blade. The experimental model reported adjacent
tissue damage up to 25.7mm and temperature up to 1400C.
●
No reliable sealing of medium-sized vessels more than 3mm.
●
Mist production due to vaporization or de-atomization, or cavitation effect.
●
Blade fatigue, higher heat production due to changing impedance of tissue [5, 6].
Vessel Sealing Bipolar Electrosurgery [Ligasure]
This advanced electrosurgery equipment has a tissue-grasping jaw that measures
tissue impedance. It delivers pulsed energy with a continuous computerized
feedback system in a specialized bipolar electrosurgery unit in a combination of
optimal compression force over tissue or vessel to seal it reliably up to 7mm.
Sealing of the vessel is comparable to mechanical suturing or clipping that can
withstand pressure three times higher than normal systolic blood pressure as the
technology senses the tissue impedance; real-time adjusted energy is used to seal
the vessel using tissue collagen and elastin. It avoids foreign body-related
reactions.
It has a particular sound at the time of sealing and a different sound at the end of
the completion of sealing where the energy cycle stops, usually sealing time 24seconds. It may have an inbuilt knife for dividing. Lateral thermal spread is
minimal. It has specially designed jaws for the ease of working in a limited space.
Uses: All major surgeries where vessels between 3-7mm require reliable
transaction- like in inferior mesenteric artery, branches of S.M.A., gastric arteries,
etc.
Advantages
●
Dissection, grasping, sealing and division of tissue are performed by a single
instrument.
●
Unit gives signals after the completion of sealing, indicating time to divide
tissue.
●
Faster and effective sealing of the vessels up to a diameter of 7mm within 2-4
seconds.
●
Lesser lateral thermal spread minimizing complications due to thermal injuries.
●
Different jaw sizes and in-built cutting knife provide ease of operating at a
difficult site like in pancreatic surgeries.
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Disadvantages
●
Higher cost of hand probes in developing countries [3, 4].
Argon Plasma Coagulation
It's a non-contact monopolar coagulation electrosurgical unit where inert and good
conductor Argon gas flows through a silicon tube Fig. 5. Electrode fitted in the
tube is ignited by 4kV amplitude current and 350 kHz frequency; thus, generated
sparks ionize Argon gas into plasma and thus, electric heat is transported to
superficial tissue for coagulation. Due to the safety of the device, it can be used to
coagulate larger surfaces like gastrointestinal vascular malformation and infective
cystitis leading to bleeding or solid organ surface in splenorrhaphy, nephronsparing renal surgery or hepatectomy. The operating probe has different tips for
delivering plasma at précised site; it is to be positioned at a distance of 2-10mm
from the tissue and Argon gas flow and net effect leading to coagulation.
Fig. (5). Assembly with external sheath, electrode.
Advantages
●
Faster and reliable superficial control of bleeding.
●
Blood from capillaries is pushed apart due to high-density Argon gas, resulting
in better coagulation, less eschar over tissue and less tissue damage.
●
It displaces air and oxygen and improves safety.
●
There is no charring at the tip as it is 2-10mm away from the tissue, and the
temperature generated is never higher than 1000C.
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Disadvantages
●
Gas embolism of different magnitudes is a frequently encountered complication
due to its insolubility; to minimize gas embolism, the rate of flow of Argon gas
should be the lowest possible rate [4, 7].
Cavitron Ultrasonic Surgical Aspirator [C.U.S.A.]
This unit combines an ultrasonic generator, an aspiration system and an irrigation
system. The electrosurgical unit generates ultrasonic frequency from 23 kHz to 36
kHz. Two types of transducers are currently available a) Piezoelectric, which uses
ceramic disks, and b) Magnetostrictive use Nickel alloy.
Fig. (6a). Diagrammatic assembly of circuit.
Fig. (6b). Actual assembly in transducer.
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Fig. (6c). Different parts of the active electrode of C.U.S.A.
Fig. (7). Diagrammatic view of C.U.S.A.- Tip, Transducer, suction and aspirator.
Depending upon the capacity, the ultrasonic generator produces a current of 23 or
36 kHz, which is transferred to the transducer; the piezoelectric transducer
converts this vibration into mechanical vibration; the transducer is connected to
84 Handbook of Laparoscopy Instruments Shinde et al.
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the hallow surgical tip through the connecting shaft, which results in to and fro
motion along the long axis of the instrument. When the tip comes in contact with
tissue, it produces a cavitation effect (vaporization at low heat), leading to precise
and effective destruction in tissue containing more fluid like the liver, spleen, and
kidney than in collagen-rich tissues like vessels, ducts, or nerves.
In a magnetostrictive transducer, current passes through a coil, producing a
magnetic field which in turn produces oscillating motion in the transducer, which
is attached to the hollow metal surgical tip of the instrument by the shaft.
Cellular debris produced due to cavitation is aspirated by a suction aspirator,
keeping the surgical field clear.
A higher frequency of vibration produces heat at the surgical tip; cooling is
performed by continuous irrigation of cold saline to avoid thermal injury in
addition to the emulsification of fragmented tissue. A pump pushes sterile
irrigation fluid to irrigate the lumen surrounding the vibrating tip. When the fluid
reaches the terminal end of the irrigating tube, 99% is aspirated through the preaspiration hole. This mechanism aids in avoiding the pooling of irrigation fluid at
the operative site, keeps the suction tube free from blockages, emulsifies tissue
fragments and cools the vibrating tip of the instrument to prevent thermal injury.
Lower amplitude mode has shorter strokes and less force of impact on the tissue;
hence, higher amplitude mode has longer strokes and higher force of impact and
fragmentation rate.
Advantages
●
Precisely tissue fragments with high water content like the liver, spleen, kidney,
brain or fat and more increased collagen-containing tissues are free from injuries
in low amplitude setting, i.e. selected tissue mode.
Disadvantages
●
Squeezing the flue over the vibrating connected shaft due to a faulty grip can
cause frictional heating injury to the surgeon's finger.
●
An injury to ducts, blood vessels and nerves has been reported; hence
appropriate settings are necessary [4, 8, 9].
Laser Electrosurgery
LASER (Light amplification by stimulated emission of light rays) is where an
optical resonator is used to modify waves into high-intensity light waves. The
diameter of the laser beam is inversely proportional to the frequency of the light
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waves, i.e., the frequency is smaller than the diameter of the laser. The range of
micro-millimetres of spot size of beam and scanner provides high precision. The
invention of photonic crystal fibers added to its use in endoscopic surgeries and
eliminated the limitation of the surface use of laser.
The power of the laser is measured in irradiation units.
Lasers have two types of effects on tissues: 1) Photochemical, and 2) Photothermal.
In a photo-chemical process, low irradiation amplified electromagnetic or light
waves are absorbed by the tissue, and heat is generated for cutting or coagulation
in the tissue. High irradiation is used to achieve photo-thermal effects to destroy
the tissue.
Commonly used Laser: Nd YAG Laser, CO2 Laser
Types of Lasers
●
Surface contact type where energy is directly transferred to tissue from the
probe's tip.
●
Surface non-contact type where energy is indirectly transferred to tissue through
explosive vapor bubbles formed from the tip to the tissue through a liquid
medium.
Advantages
●
Improved outcomes in cosmetic plastic surgery and infertility-related
gynaecological procedures.
●
Better outcomes are noted when used in endovascular or endoscopic urological
procedures like endovenous Laser treatment.
Disadvantages
●
Learning curve to use laser devices is longer.
●
Longer operative time.
●
Damage to surrounding tissues like vessels and duct is common.
●
Fire hazards from flammable materials [4, 9].
Radiofrequency Energy
3 kHz to 300 MHz is the range of radio frequencies generated by the
electrosurgical generator (Fig. 8). Electromagnetic radiation is used to generate
heat in the tissue. Active and dispersive electrodes are responsible for the
alignment and vibrations of dipole molecules in cells.
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Fig. (8). Relation rate of rise in temperature and varied effects on tissue.
Vibrations are of greater intensity near the electrode and lesser intensity in the
periphery; i.e., the electrode itself is not the source of heat production, but the
vibration of molecules in cells produces heat; hence temperature is higher near the
tip and lowers towards the periphery of the tip.
As this electrosurgical unit generates heat in the tissue due to vibrations of dipole
molecules, tissue conductivity is the most important tissue characteristic for
effective ablation. In cases where the temperature is high near the tip, it leads to
early desiccation, charring and carbonization. As desiccated and charred tissue
gives an insulating effect, it prevents the dispersal of electric current and limits
vibration causing inefficient heat in the periphery for the desired ablation; it limits
effective tissue destruction towards the periphery.
Slow temperature rise versus fast temperature rise For effective ablation of larger
tissue size, slower heat concentration is ideal than rising cellular temperature
faster for heat production. Blood flow (vessels >3mm) and tissue fluid cause a
cooling effect called a 'heat sink' (Fig. 9) that affects precision in ablation.
Energy Devices Handbook of Laparoscopy Instruments 87
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Fig. (9). Tissue sink effect.
Heat Sink: White dot reveals the vessel that decreases the tumor volume ablation.
The aim is to achieve tumour temperature of 500C -1000C over 4-6 minutes with
a cuff of normal tissue in the range of 0.5-1cm.
Radiofrequency ablation is commonly performed to ablate primary or secondary
tumour in the liver smaller than 3-4cm. Usually ultrasound-guided catheter
placement is achieved at the desired point, and methodically slow energy is
accumulated by the radiofrequency cathode to achieve effective tumour ablation
[2, 4].
CONCLUSION
The advantage of all electrosurgical devices is that they reduce the time of
surgery, precision of surgery, and surety about haemostasis; hence it is an aid in
safe surgery. It avoids foreign body use for achieving haemostasis. Monopolar
cautery has higher tissue destruction due to the lateral spread of current into the
tissue, which interferes with metal implants like orthopaedic devices or cardiac
implants. It has higher incidences of thermal burns at the returning electrode site,
stray current effect and capacitance when used improperly in laparoscopic
surgery. Good knowledge about the proper setting of the footplate, use of an
active electrode, and types of tissue is important for safety and to achieve the
desired effect.
Newer energy devices used for electrosurgery are much safer than monopolar
cautery. Bipolar cautery and its different modifications have several advantages
over monopolar cautery. Alterations in the bipolar tip for sensing the type of
tissue, the effect of current on the tissue and feedback mechanism about the
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completeness of the desired effect provide safety and convenience to the operator.
There is a limited spread of energy, no returning electrode site burn or effects over
body implants. High-end cautery like ultrasonic dissectors, C.U.S.A. have
improved the quality and feasibility of complicated surgeries, but at a high cost.
A radiofrequency energy device is used for the thermal destruction of benign or
malignant tissue but not for dissection in surgery.
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[6] Prof Jahangir Sarwar Khan. Harmonic Scalpel. Ann Pak Inst Med Sci 2015; 11(1): 1-2.
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[PMID: 20204117]
[8] Available From: http://aiimsnets.org/review_seminar/CUSA/1.pdf https://www.youtube.com/
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