Laparoscopic energy source and its optimum use in dissection

Ultrasonic Generator

DISSEACTION WITH ENERGY AND THEIR OPTIMAL USE

Many powers are available to cut, coagulate and evaporate tissue. An entire knowledge of the gear, power source physics, potential hazards and limitations is important if power source related complications are to be reduced. Energy sources are classified as electrical, laser, ultrasonic, and mechanical. The surgeon must realize that the use of a specific energy source does not in itself lessen the risk of a complication. Energy sources for example electrical, laser, ultrasonic and hydro energy have unique properties that determine their effectiveness and limitations when used during non-invasive surgery. What's also true is the fact that a particular surgeon might be conversant or might have mastered a particular technique which may not really be familiar to a different. It's thus been aptly noticed that “It’s not the wand but the magician making a difference”

ELECTROSURGERY

Electrosurgery uses an alternating radiofrequency current with a frequency of 500,000 to two million Hz per second. This rapid turnaround of current implies that ion positions across cellular membranes don't change. Consequently, neuromuscular membranes don't depolarize, and there is no danger of cardiac defibrillation at extremely high frequencies unlike household current,which using its low frequency of 60 Hz, can producenventricular fibrillation. The terms electrocautery and electrosurgery are often used interchangeably in modern surgical practice. However, these terms define two distinctly different modalities. Electrocautery may be the utilization of electricity to heat a metallic object which is then accustomed to coagulate or burn. It is important to realize, there is no current flow with the object being marked or cauterized with electrocautery. Electrosurgery, on the other hand, uses the electrical current itself to heat the tissues. As a result, the electrical current must go through the tissues to produce the result. The current then flows through the tissues to produce heat from the excitation from the cellular ions.

PHYSICS OF ELECTROSURGERY

The basic principle of electrosurgery is the fact that current flowing through the body takes the path of least resistance which in the body means tissues with maximal water (thus electrical resistance is within inverse proportion to water content). Probably the most conductive is blood followed by nerve, muscle, adipose tissue and finally least conductive may be the bone. It's also important to remember that the path is not always a straight one. When the current passes through a tissue it dessicates (dries out) the tissue due to that the resistance of that tissue rises leading to non conductivity and also the current then takes the road through adjacent tissues that have a smaller resistance. Hence the flow pattern of current through live tissue can never be predicted. Also this changing resistance of body tissue throughout the current flow mandates that electrosurgical generators must deliver current at increasing voltages that are matched towards the expected tissue resistance of the body , otherwise, current flow could be too low to produce the desired effect or too great, leading to injury.

This explains why the pinpoint tip of the electrosurgical pencil works more effectively than the usual spatula. It follows that in laparoscopy, the less section of contact from the electrode in the intended site of effect, the higher would be the effect. The amount of heat released is directly proportional to the resistance of the tissues.

High Current density

  1. Direct current which is unidirectional and is also known as galvanic current and is used in acupuncture and endothermy although not for electosurgery.
  2. Alternating current or AC in which the flow alterations in a sinusoidal fashion and is utilized in electrosurgery.
  3. Then you have the pulsed current where a large quantities of electrical energy is discharged in a very small amount of time. It is used for electromyography and nerve stimulation.
  4. The current circuit needs to be completed that is carried out by either the floor pad (that is incorrectly called earth plate) that takes the present back to the machine after travelling through the body (unipolar circuit). Thus it should be the aim to reduce the length between the operating electrode and also the ground pad. Within the bipolar circuit ,because both the good and bad electrodes are close to one another, the present flow inside the body is minimal and is thus less damaging. Most (85%) of surgeons use monopolar electrosurgery, whereas the remainder use bipolar electrosurgery.

Electrosurgical generators are essentially of two types: grounded and isolated. The newer isolated generators get rid of the chance of an alternate site burn by requiring the present to return to the generator. In the early grounded generators the present returned to earth by any contact point and thus caused inadvertent burns. Both unipolar and bipolar circuits can further be modified as open and closed circuit. Open circuit is usually formed when the electrode does not make contact with the tissues or even the tissue in contact with the electrode has already been dessicated. In the circuit, the resistance increases and generator increases the voltage to shut the circuit and also the wave form also becomes erratic. The current in close circuit is safe and delivers lesser voltage.

BIOPHYSICS

  1. The electrosurgical effect on the tissue results in 3 definable effects
  2. cutting
  3. coagulation and or fulguration
  4. dessication

True electrosurgical cutting is really a noncontact activity in which the electrosurgical instrument must be ten or twenty yards in the tissue to be cut. If there is contact, desiccation will ensue rather than cutting. Cutting requires the generation of sparks of brief duration between the electrode and also the tissue. Heat from these sparks is used in the tissue, producing cutting. As electrons in the form of sparks bombard cells, the power used in them increases the temperature in a cell. As a result, a temperatures are reached at which the cell explodes. The best wave for cutting is a non modulated pure sine wave because current is delivered to the tissue almost 100% of the time that the electrosurgical delivery device is activated. If the cut is created by keeping the probe in contact with the tissue then it is not true cutting rather it's mechanical cutting through cauterized tissue. Fulguration also mandates that tthere shouldn't be contact between your electrosurgical delivery tool and the tissue. In contrast to cutting, fulguration requires short bursts of high voltage only 10% of the time to produce sparks but a low capacity to produce coagulation as compared to cutting. Coagulation and Fulguration thus utilize higher voltage than cutting however the pause between current flows is much more (maximum pause in fulguration). Both cause coagulative necrosis of tissues and fluid. Desiccation is the procedure by which the tissue is heated and the water within the cell boils to steam, resulting in a drying out from the cell. Desiccation is possible with either the cutting or even the coagulation current by contact from the electrosurgical device with the tissue because no sparks are generated. Therefore, desiccation is a low power form of coagulation without sparking, which is the most common electrosurgical effect utilized by surgeons.

The pure cutting current will cut the tissue but will give you poor hemostasis. The coagulation current will provide excellent coagulation but minimal cutting. The blend current is an intermediate current between the cutting and the coagulation current, as you might expect. In fact, it's a cutting current - the duty cycle or time how the current is really flowing during activation of the electrosurgical delivery device is decreased from 100% of the time to 50% to 80%. It is important to observe that setting the generator to blend mode does absolutely nothing to affect the coagulation current that's provided. Only the cutting current is altered so that the duty cycle is reduced to supply more hemostasis. The use of electrosurgery in laparoscopic surgery is complicated by the insufflating gas, with a low heat capacity. Consequently, instruments may not cool as rapidly as with the open environment. In addition the high water content from the gas increases the conductive capacity from the medium. Despite new advances in machines which are safer, complications can continue to occur and injuries like, bile leaks, intestinal injuries, anastomotic leaks and postoperative bleeding may derive from the inappropriate or injudicious use of electrosurgery. Fortunately most if not all injuries could be eliminated through isolated generators, returns, electrode monitoring systems. and active electrode monitoring systems.

“HOOK, LOOK, COOK”.

ELECTROSURGICAL PROBES

  1. COMPLICATIONS which could derive from the use of electrosurgey include.
  2. Grounding failures
  3. Alternate site injuries
  4. Demodulated currents
  5. Insulation failure
  6. Tissue injury at a distal site
  7. Sparking
  8. Direct coupling
  9. Capacitive coupling
  10. Surgical glove injury
  11. Explosion

Patient Pad Failures

The big surface area of contact it provides, allows the current to be dispersed on the large enough area that the current density at any one site on the electrode is small enough not to produce thermal damage. Lack of uniform contact can result in significant current concentration and damage. Any conductive low resistance object may serve as the conduit. Exit of current at these alternate sites can produce injury at an alternate site. Usually such injury results when the site of contact is small, thereby providing a higher current density.

Demodulated currents

Modern generators have filters that remove demodulated currents from the current sent to the patient so that only electrical current of 250 to 2000 kHz is delivered. Demodulated currents occur most often when an electrosurgical instrument is activated off metal after which touched towards the metal, like the common practice of “buzzing a hemostat”. Demodulated currents produce neuromuscular activity that is usually of no significance unless directly coupled to the heart through a catheter or throughout a cardiothoracic surgical treatment. Another illustration of demodulated current is muscle fasciculation at the site of the laparoscopic cannula throughout the utilization of electrosurgery.

Insulation Failure

Insulation failure is regarded as the most typical reason for electrosurgical injury during laparoscopic procedures and more commonly seen rich in voltage coagulation wave form. Voyles and Tucker have classified insulation failure into four potential zones of damage. Zone 1 failures are easily seen through the surgeon, Zone2 can only be seen after careful inspection also , since the break is small a high current density is achieved. Zone3 is detected by appearance of demodulated current induced fasciculations and Zone4 is injurious towards the surgeon or other personnel.The important thing factor that determines the magnitude of damage from insulation failure resides in the size the break in the insulation. Paradoxically, the smaller the break, the higher the probability of injury if contact of tissue with this site occurs. This really is associated with the concept of power density. Protection against insulation failure is supplied by the active electrode monitoring system available in many machines.

Current passing through structures of small cross sectional area may have current concentrated there, with resultant unintentional thermal injury. For instance when the testicle and cord are skeletonized and mobilized from the scrotum, using energy towards the testicle can lead to harm to the cord, because the current must return to the indifferent electrode through the small diameter cord prior to it being dissipated in your body through numerous pathways. Another illustration of cutting an adhesive band from the gallbladder to the duodenum with electrosurgery. If the adhesion is wider near the gallbladder than on the duodenum, the present density will be greater about the duodenum injuring the duodenum. Jumping of sparks in the electrode to tissues is the mechanism for fulguration and true electrosurgical cutting. However, additionally , it may occur in an unintended fashion such that injury results, particularly in laparoscopic surgery. The ability of electrical sparks to visit over a distance in a gaseous environment is increased once the tissue desiccates and there is a moist, smoky environment. Current may also jump from anywhere on the uninsulated end of the electrode and want not jump from the tip. Additionally, develop of eschar about the electrosurgical instrument may promote arcing to some secondary site. Sparking with monopolar electric energy is small. Under normal operating conditions at 30 to 35 W, because sparks jump Two to three mm, 50% of the time, it's not enough to allow significant air or CO2 gaps to be bridged.

Direct Coupling

Direct coupling occurs when an electrosurgical devices is in connection with a conductive instrument. Direct coupling can be reduced by using only insulated instruments and consideration to prevent contact with any metallic object within the operative field and activating the electrosurgical electrode should only be achieved inside the visual field and never near the another metal object like a clip, staple, laparoscope, or metal instrument.

Capacitive Coupling

Capacitance is stored electrical charge that occurs between two conductors that are separated by an insulator. The capacitively coupled current really wants to complete the circuit by getting a pathway towards the patient’s return electrode. The charge is stored in the capacitor until either the generator is deactivated or perhaps a pathway to complete the circuit is achieved. Capacitive coupling is greatest within the coagulation mode when there is no strain on the circuit (open circuit). Capacitive coupling is considerably greater via a 5-mm cannula than through an 11 mm cannula and greater, the longer the cannula. Every object in the room- the surgeon, the individual, the operating table - all possess a small but finite capacitance to earth when two conductors are separated by an insulator. Even without the ether and other explosive anesthetic agents there's still a significant explosive hazard when elecrosurgery can be used especially from intestinal gas. Indeed 43% of unprepared bowel includes a potentially explosive mixture or gases. Hydrogen air mixtures composed of 4% to 7% are potentially explosive. For this reason, mannitol, which promotes the production of methane, should be avoided in bowel preparations. Although debated, studies have documented levels of nitrous oxide within the peritoneal cavity during laparoscopy that can support combustion.

Electrosurgical By-products

Include biological by products, in addition to chemicals and irritants. Although a lot of of those by-products might be mutagenic or carcinogenic, no adverse effects happen to be documented in the literature.The best studied chemicals which are potentially generated by laparoscopy are methemoglobin and carboxyhemoglobin.

Bowel Injuries

Tend to be unrecognized when they occur and present 3 to Seven days after surgery. Because of this, they carry a higher mortality rate resulted from the early experience with tubal sterilization using monopolar electrosurgery.

Bipolar Electrosurgery

In contrast to unipolar circuits shows a decrease in the quantity of tissue damage. Also as compared to unipolar electrosurgery, the overall damage is twice less, there is reduced depth of penetration, less smoke is generated and also the risk of perforation is less. On the other hand, hemostasis isn't as good. Another obvious advantage of bipolar electrosurgery over monopolar electrosurgery may be the lack of coming back electrode about the patient which eliminates the possibility of ground pad and alternate site burns, and capacitive coupling. Additionally it almost eliminates the risk of insulation failure. Finally, direct coupling may appear only when metal is grasped or placed between the electrodes inside a bipolar circuit or extremely near to the electrodes. However since the outer layers of tissue desiccate, the potential to deal with current flow increases and lateral spread occurs to almost 3-4 mm. Also coagulation may cease before it is completed and for that reason bleeding may result. This explains in part the occasional high rates of pregnancy following bipolar sterilization. Where the tubes may not be completely blocked. A significant problem with bipolar electrodes is tissue sticking. This can be reduced or eliminated by irrigation from the bipolar electrodes during the time of activation; the irrigant not just cools the electrodes but additionally the tissue, thereby minimizing conducted thermal injury. Nonelectrolytic solutions for example glycine or weakly electrolytic solutions work best. The main tissue effect achieved with bipolar electrosurgery is tissue coagulation through the procedure for desiccation. Bipolar electrosurgery can coagulate vessels upto 7 mm diameter.

Guidelines for that Utilization of Electrosurgery in Laparoscopic Applications

  1. Avoid using over 30 W of power.
  2. Use just the coagulation mode with wire electrodes. When the cutting mode is used, there's more bleeding, which can obscure the operative field. Because wire electrodes are so thin, one can achieve satisfactory cutting (much like that achievable in a blend setting) in the pure coagulation surgery. Injury can be reduced by lowering the “on” time of the current. This really is controlled by the surgeon using whether handpiece or perhaps a foot pedal.
  3. Use electrode geometry to attain precise coagulation or cutting. Choose a smaller contact patch to achieve cutting and a larger contact patch to to achieve coagulation.
  4. The tissue needs to be positioned on tension to attain cutting.
  5. Use the thin wire electrodes to cut. Thick wire electrodes perform poorly simply because they tend to cause coagulation, and cutting and coagulation can't be properly achieved. Thinner wire electrodes may be used for precise bloodless dissection.
  6. The foot switch or hand switch ought to be activated for brief periods only. When the current is on long, the chance of remote site electrical injury is increased (in case it comes with an unrecognized insulation failure)
  7. If the surgeon observes blanching of tissue, a precursor of charring, an excessive amount of power has been used. Charring should be avoided. Within the liver bed, this will result in the liver tissue sticking with the electrode and, when the electrode is moved, it'll tear the liver tissue.
  8. The use of the hook could be summarized as - “HOOK, LOOK, COOK”

RECENT ADVANCED TECHNOLOGY AND INSTRUMENTATION IN ELECTROSURGERY

ULTRASONIC ENERGY

Today almost all laparoscopic procedures can be performed safely and efficiently without electrosurgery by using ultrasound. Furthermore, ultrasonic surgery has also replaced mechanical surgical clips and scissors in many laparoscopic procedures. Physics of Ultrasound: Audible sound waves, are confined to the regularity range of 20 cycle per second (Hz) to about 20,000 cycles per second. A longitudinal wave, whose frequency is above the audible range is an ultrasonic wave. When ultrasonic waves are applied at low power levels, no tissue effect occurs as is the case for diagnostic ultrasound imaging. However, higher power levels and power densities could be harnessed to produce surgical cutting, coagulation, and dissection of tissues. This involves mechanical propagation of sound (pressure) waves from a power source via a medium to an active blade element. Waves are longitudinal mechanical waves that may be propagated in solid, liquids, or gases. Ultrasonic dissectors are of two types, low power which cleaves water containing tissues by cavitations, leaving organized structures with low water content intact, e.g. arteries, bile ducts etc.; and high power systems which cleave loose areolar tissues by frictional heating and therefore cut and coagulate the edges simultaneously. Thus, low power systems (ultrasonic cavitational aspirators) bring liver surgery and neurosurgery (Cusa, Selector) and don't coagulate vessels. High power systems (Autosonix, Ultracision) are utilized extensively, particularly in advanced laparoscopic surgery. The Harmonic scalpel and also the AutoSonix system operate in a frequency of 55.5 kHz. Ultrasurgical devices are made up of a generator, handpiece, and blade. The handpiece houses the ultrasonic transducer, a collection of piezo electric crystals sandwiched under pressure between metal cylinders. The transducer is attached to a mount, which is then connected to the blade extender and blade. The harmonic scalpel cools the handpiece with air. AutoSonix and Sonosurg systems rely principally on large diameter handpiece made of heat dissipating materials to remove the heat and stop heat build up.

Ultrasonic cutting, coagulation, and cavitation: The fundamental mechanism for coagulation of bleeding vessels ultrasonically is comparable to that of electrosurgery or lasers. Vessels are sealed by tamponading and coapting with a denatured protein coagulum. Electrosurgery uses electrons and lasers use photons to excite molecules in the tissue. This in turn releases heat and protein is denatured to form a coagulum. Ultrasurgical devices denature proteins by mechanical energy from the vibrating probe. Ultrasurgical hook or spatula blade can coagulate blood vessels within the 2 mm diameter range quite easily and also the scissors can coagulate vessels up to 5 mm in diameter. Heat generated using the Harmonic is limited to temperature below 80OC. The overall temperatures achieved by the Harmonic scalpel even after prolonged use remains well below the 250O to 400O C achieved with electrosurgery and laser surgery. This leads to reduced tissue charring and desiccation and also minimizes the zone of thermal injury. Skin incisions made with the ultrasonically activated scalped or cold steel scalpel heal almost identically and therefore are superior to electrosurgically made incisions. This minimal damage may explain the marked reduction in postoperative adhesions to the liver bed following laparoscopic cholecystectomy with the ultrasonically activated scalpel, when compared with electrosurgery or laser surgery in experiments performed in pigs, Although coagulation made by ultrasonic surgery is slower than that observed with either electrosurgery or laser surgery , nonetheless, it is as effective or even more effective. However greater depth of thermal injury migh result with ultrasurgery as compared to electrosurgery if activation persists for more than 10 seconds. Despite the slower rate of tissues coagulation, the entire process of tissue coagulation coupled with transaction, the ultimate goal of surgery, is faster with the LCS or hook scalpel than with other energy modalities.

The mechanisms of coagulation offer an advantage for ultrasonic surgery over electrosurgery when coagulation the side wall of a blood vessel. Arteries are often not coapted significantly by electrosurgery due to the concomitant reduction in power density. Furthermore, the blood inside the vessels has a high temperature capacity and provides a heat sink, that allows one side to coagulate before the other, with resultant bleeding from the hole in the wall from the vessel that was in contact with the electrosurgical device. This isn't the case with ultrasurgery. Lack of coagulated tissue sticking to the active element, because of the vibration from the active blade, is really a unique feature of ultrasurgical coagulation compared with other energy modalities. In addition, the grasper blade allows unsupported tissue to be grasped and coagulated quite easily, or cut and coagulated as with scissors. The cutting mechanism for the ultrasonically activated scalpel is also different from that observed with electrosurgery or laser surgery. At least two mechanisms exist. The first is cavitational fragmentation in which cells are disrupted. This occurs primarily in low protein density areas such as liver. This mechanism is comparable to that observed using the ultrasonic aspirating device ( CUSA), The later device consists of an ultrasonic generator that vibrates at 23000 Hz. When coupled with powerful aspiration device , the ultrasonic aspirator fragments cells and aspirates the resulting cellular debris and water. This course of action leaves collagen rich tissues for example arteries, nerves, and lymphatic intact. Thus, these is no cutting or coagulation with the ultrasonic aspirator. In marked contrast, the ultrasonically activated scalpel not just coagulates and cavitates, additionally , it cuts high protein density areas such as collagen or muscle rich tissues. This happens via the second cutting mechanism , which is the particular “ power cutting” offered by a relatively sharp blade vibrating 55500 times per second over a distance of 80 um. A major benefit of the ultrasonically activated scalpel’s coagulation ability may be the lack of melting vand charring of tissues. This allows the tissue planes to be clearly and sharply visualized all the time. As a result surgeons can be more precise because they can see better than along with other energy forms. Because there is little if any cutting ability with the blade within an activated situation the ultrasonically activated scalpel can also be used as a blunt dissector to aid in identifying tissue planes. You should remember that high power ultrasonic dissection systems could cause collateral damage by excessive heating and this is well documented in clinical practice. Ultrasonic surgical dissection allows coagulation and cutting with less instrument traffic (reduction in operating time), less smoke with no electrical current.

  • Mechanical energy at 55,500 vibrations / sec.
  • Disrupts hydrogen bonds & forms a Coagulum
  • Temperature by Harmonic Scalpel-80-100 ° C
  • Temperature through Electro coagulation-200-300 ° C
  • Collateral damage,
  • Tissue necrosis.

With the development of newer generators and innovative instrumentation, better delivery of the appropriate quantity of energy leads to better sealing of vessels.

Argon Beam Coagulator:

Argon gas is an inert, noncombustible and easily ionized gas which is used in conjuction with monopolar electrosurgery to produce fulguration. Essentially, the electrical current ionizes the argon gas, thereby creating a more efficient pathway for that current to flow since the gas is much more conductive than air, therefore providing a bridge between your tissue and also the electrode. Less smoke is produced with the argon beam coagulator since there is less depth of injury. Despite these advantages, the argon beam coagulator suffers from one very significant drawback in laparoscopic surgery, namely, high flow infusion of argon gas to the abdominal cavity which not just boosts the intraabdominal pressure to very damaging levels, but could also lead to fatal gas embolism.

The Gyrus PK Tissue Management System (Gyrus Medical, Inc, Minneapolis, Minnesota) instruments give a unique technology called Vapour Pulse Coagulation (VPC), which produces faster, more uniform results with pulsed energy instantly delivered inside a controlled manner. VPC’s pulse-off periods allow tissue for cooling and moisture to return to the targeted area, greatly reducing hot spots and coagulum formation. Fraxel treatments also results in evenly coagulated target tissue, minimal thermal spread, less sticking, that has been enhanced hemostasis. It does require its own generator, which works in tandem using the Gyrus PK instruments.

The SurgRxEnSealSystem (SurgRx, Inc., Palo Alto, California) incorporates Smart Electrode Technology. The EnSeal instruments adjust dose energy simultaneously to numerous tissue types inside a tissue bundle each with its own impedance characteristics. This electrode includes an incredible number of nanometer-sized conductive particles embedded in a temperature-sensitive material. Each particle acts like a discrete thermostatic switch to regulate the quantity of current that passes into the tissue region with which it's in contact, thereby generating heat within it. To keep temperature from rising to potentially damaging levels, each conductive nanoparticle interrupts current flow to some specific tissue region engaged by the electrode region. When temperature dips below the perfect fusion level, the person particle switches back on, reinstating current flow as well as heat deposition. The procedure continues until the entire tissue segment is uniformly fused without charring or sticking. Less heat is needed to accomplish fusion, since the tissue volume is minimized through compression; energy is focused about the captured segment; and the vessel walls are fused through compression, protein denaturation,after which renaturation.

The Ligasure

The Ligasure System (Valleylab, Boulder, Colorado) LVSS (Ligasure vessel sealing system) utilizes a brand new bipolar technology for vascular sealing having a higher current and lower voltage (180 V) than conventional electrosurgery. It uses a unique mixture of pressure and energy to produce vessel fusion. This fusion is accomplished by melting the elastin and collagen within the vessel walls and reforming it right into a permanent, plastic-like seal. It doesn't depend on a proximal thrombus along with classic bipolar electrocautery. A feedback-controlled response system automatically discontinues energy delivery once the seal cycle is complete, eliminating guesswork and minimizing thermal spread to approximately 2 mm for most LigaSure instruments. This unique energy output leads to virtually no sticking or charring, and also the seals can withstand Three times normal systolic blood pressure level.[3] This system also requires a designated generator that works with a number of different instruments created by the company. The LigaSure Vessel Sealing System includes:

  1. An electrosurgical generator in a position to detect the characteristics of the tissue closed between the instrument jaws; it delivers the exact amount of energy needed to seal it permanently.
  2. Several kinds of instruments that seal and, in some instances, divide the tissue. Those used are the following:
  3. LigaSure Atlas is a surgical endoscopic device (diameter: 10 mm, length: 37 cm) that seals and divides vessels as much as 7 mm in diameter;
  4. LigaSure V is really a single-use endoscopic instrument (diameter: 5 mm, length: 37 cm) able to seal and divide;
  5. LigaSure Lap is a single-use endoscopic instrument (diameter: 5 mm, length: 32 cm);
  6. LigaSure Precise is really a single-use instrument (length: 16.5 cm) for open procedures specifically designed to supply permanent vessel occlusion to structures that require fine grasping;
  7. LigaSure Std is really a reusable instrument.

High- Velocity Water- Jet Dissection

High-velocity high-pressure water- jet dissection involves the use of not at all hard devices to create clean cutting of reproducible depth. Other advantages are the cleansing from the operating field through the turbulent flow zone and the little bit of water required to complete dissection. Specific problems were identified by using this modality. The “hail storm” effect lead to excessive misting which obscures vision. This has been solved to some extent by a hood within the nozzle. The non-haemostatic nature of this modality, difficulty in gauging distance and poor charge of the depth of the cut are additional drawbacks. The spraying of tissue fragments renders additionally , it oncologically unsound. The present utilization of water- jet dissection is restricted to dissection of solid organs.

Hydro Dissection

Hydro dissection uses the force of pulsatile irrigation with crystalloid solutions to separate tissue planes. The Laser unit with hand pieces 38 Powers in Laparoscopy and their optimal use operating field at the same time is kept clear. Like water jet dissection no haemostasis is achievable. Using this dissecting modality is fixed to pelvic lymhadenectomy and pleurectomy in thoracoscopic surgery.

Radiofrequency Ablation

Radiofrequency ablation is non-invasive method that utilizes thermal energy to destroy tumor cells. Initially computed tomography or ultrasound is conducted to find the tumor. A special needle is introduced into the tumor using direct image guidance. This is equal to a standard needle biopsy. The needle is mounted on a radiofrequency generator. The generator sends radiofrequency through the needle, which generates heat from frictional movement of ions. The heat destroys the tumor cells.

In RFA, energy is delivered through a metal tube (probe) inserted into tumors or other tissues. When the probe is within place, metal prongs open out to extend the reach of the therapy. RF energy causes atoms in the cells to vibrate that will create friction. This generates heat (as much as 100o C) and leads to the death from the cells. The efficacy of treatment methods are assessed by CAT scan 30 days following treatment. Re-treatments are often necessary. Risks of the procedure include bleeding, even though this is extremely rare. Prongs pop available to deliver RF energy, which generates heat that kills cancer cells.

Microwave Ablation

An alternative way of producing thermal coagulation of tissue requires the use of microwaves to induce an ultra-high-speed (2450 MHz) alternating electric field, resulting in the rotation of water molecules. Even though utilization of microwaves for tissue ablation isn't new, the majority of the clinical experience with this technique to ablate liver tumors comes from Japan. Percutaneous microwave ablation was first used as an adjunct to liver biopsy in 1986, but it has since been employed for hepatic tumor ablation. Just like RF ablation, microwave ablation involves placement of a needle electrode directly into the prospective tumor, typically under US guidance. Each ablation also produces a hyperechoic region round the needle, much like that observed with RF ablation. Unlike RF ablation, however, no retractable prongs are utilized, and the resulting ablation is commonly a lot more elliptical.

Cryotherapy

Used in the laparoscopic ablation of secondary tumordeposits in the liver, usually when the lesions are inoperable for whatever reason, Laparoscopic Cryotherapy with implantable probe destroys tumours by rapid freezing to -40°C or lower. The lesion re-vascularises for a short period (12-14 hours) on thawing but because the vasculature and also the tumour parenchyma are amaged beyond repair, hemorrhagic infraction ensues.

LASER (Light amplification through stimulated emission of radiation)

Principles of Stimulated Emission

In a normal population of atom most come in the resting state. Half the normal commission of atoms will be at the next higher degree of energy, E1, and decreasing percentage exists at ever-increasing energy to En. It's possible by the addition of optical, chemical, or electrical power from a pump (external) source, to raise the atom in the resting state to higher energy. This occurrence is called the spontaneous absorption of one's. When this occurs more atoms have been in the excited or higher energy state compared to the resting state, which is an unstable situation known as a population inversion. Such unstable atoms often produce their extra packet of optical energy and go back to the resting state which is known as spontaneous emission. It doesn't matter what kind of power source was used to create the population inversion, when the atoms release their extra photon of one's it is of the wavelength based on the atoms involved. For example with a neodymium: YAG laser the neodymium atoms are raised to raised energy with the use of krypton lamp. When the process of spontaneous emission occurs the additional photons of one's that are given of are those of neodymium energy. Because these extra photons of neodymium energy strikes other excited neodymium atoms they force the excited neodymium atoms to give off their extra energy and return to their resting state. This process is known as Stimulated Emission. Both photon of neodymium energy are emitted exactly in the same phase. Thus one incoming photon has been amplified to two outgoing photons. As this process is repeated more photons are recruited to the beam and the process of light amplification by stimulated emission is produced.

All this activity takes place inside a laser cavity. The laser cavity is really a cylinder that's closed at both ends by mirrors. The mirror in the back is a fully reflecting mirror, whereas the mirror in the front includes a small aperture in the centre, through which the laserlight can be released. Any atoms traveling parallel towards the laser cavity might be reflected backwards and forwards between the mirrors in the ends. Additionally a power pump of some sort such as the krypton lamp utilized in the neodymium laser is needed in order to create the population inversion. As the atoms are elevated to the higher energy they begin to bounce around inside the laser cavity. Most of the energy escapes tangentially into the interstices surrounding the cavity and should be removed by a heat sink. Half the normal commission from the beam however is trapped between the mirrors and continually bounces backwards and forwards running parallel towards the cavity. These photons of one's which are trapped between the mirrors still recruit more and more from the excited atoms through the procedure for stimulated emission and therefore continue to amplify their beam.
Using a foot pedal the surgeon has three options regarding the way the beam can be released from the cavity. The first mode is called the continuous wave (CW). In the CW mode, the beam continues to be emitted at a steady rate for as long as the foot pedal is depressed. The level of energy emitted is determined by the ability setting on the machine. In the pulse mode, the pulse is released for a limited time period as based on the machine setting. There is then a fixed interval between pulses. Within the interval between your pulses it's possible for that power within the laser cavity to climb higher then it will in CW mode. Thus higher peak powers are possible when using a pulsed setting. In the Q switched mode, a shutter like device like the one out of your camera enables the escape of one's in exceedingly narrow pulses. On this situation, the ability achieved within the laser cavity between pulses is extremely high. This is actually the kind of laser used frequently in ophthalmologic procedures, and also the powers in these lasers are usually measured in milliwatts. High power and short pulse duration are the hallmark of ophthalmologic lasers. First the light is monochromatic. The laser emits light on the very narrow, welldefined wavelength. Second, the sunshine is coherent. Due to the properties of stimulated emission, laser light is perfectly in the phase; that's each peak and valley of the sine wave curves align exactly. Finally the laser beam is nondivergent (upto 1degree of divergence).
Three major types of medical lasers are available commercially today, all named for the medium in the laser cavity. The carbon dioxide laser includes a wavelength within the far infrared region from the spectrum at 10600nm. Ninety seven percent of their energy is absorbed at the point of connection with a penetration of only 0.1 mm. Using the argon laser approximately 55 percent of the power is reflected back in the tissue, and also the reminder is absorbed. The argon laser is absorbed by hemoglobin or melanin selectively and does not penetrate a lot more than 1.0 mm. The neodymium: YAG laser is within the near infrared region from the spectrum at 1060nm. 50 % of its energy is reflected back in the tissue, as the other 50 % is absorbed. It is not absorbed preferentially by any pigment. Its penetration is 4.0 mm into tissue.

All three of these lasers work fundamentally by thermal action. When tissue is heated by any of these lasers as much as 60OC, there is no permanent or visible damage to the tissue. By 65OC, denaturation of protein occurs. The tissue will visibly turn white or grey and can disintegrate approximately 4 to Seven days later. This is the temperature range where the Nd:YAG laser works. Once tissue continues to be heated to 90OC to 100OC, there is tissue drying, some shrinkage, and permanent damage because of dehydration. Over 100OC carbonization or blackening of tissue occurs. As the temperature rise continues there's evolution of gas with tissue vaporization. This is actually the temperature in which the CO2 and argon laser works. The only laser system that doesn't work through the thermal cavity is argon pumped dye laser combined with hematoporphyrin derivative. On this laser system hematoporphyrin derivative is administered intravenously 48 hours just before therapy. The hematoporphyrin derivative in a few organ system of the body including the bladder is concentrated within the tumor cells in preference to the standard cells. When subjected to the red light, the hematoporphyrin derivative is excited and cleaves oxygen to from singlet oxygen within the mitochondria, leading to cell death. This is a non thermal effect.

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