ENERGY SOURCES IN SURGERY

Dr. M. Ramesh, D.N.B, F.I.C.S.

Introduction

Surgery today is being driven by technological innovations more than ever before. We are also becoming dependent on technology for further progress. I would not be wrong when I say that a whole new chapter of surgery was opened with the invention of Electro surgery several decades ago.

Adding better instrumentation and gadgets to our armamentarium is certainly helping us to leap ahead in the way we perform and our results are being made “better-than-before” always. Electro surgery not only helped us to perform surgery faster but it has also made us do certain operations that we had not imagined to be possible. Understanding nature and the energies around us, and the right application of them has surely been the prime factor to spell success in the story of the surgeon.

Today there is hardly any surgery where energy sources are not used. Yet it remains a hard truth that not a single surgical textbook that we read during our student days had a dedicated chapter for this most important factor that can make or break the fate of the patient. It has always been an enigma to me as to why we are not taught about these energy sources in our surgical curriculum. There is no doubt that the clear understanding of these energy sources is most essential for our surgical practice.

I have made a sincere attempt to write about the different gadgets that we use every day and what I feel is absolutely essential for every surgeon to know. This is a concise compilation of data rather than an article based on a surgeon’s experience.

Electro surgery

This is to describe the basic principles of Electro surgery. Unlike lasers, there has not been any regulatory body on the use of electro surgery. Traditionally the use of electro surgery has been learnt from the seniors during surgery, and surprisingly there is hardly anything written about it in any of our standard textbooks of surgery. Inspite of its potential dangers, there is not enough effort to understand the occurrence and prevention of the complications of electro surgery. This article attempts to give an insight into this topic of utmost importance to any surgeon today.

Definition One common mistake that we often come across is that the terms “Electro surgery” and “Cautery” is used for the same purpose while both of them are quite different. By definition, Electro surgery is the use of radio frequency alternating current to raise the cellular temperature as a way to vaporize or coagulate tissue. Cautery is a term derived from “Kauterion” which means, “hot iron”. It is the destruction or denaturation of tissue by a passive transfer of heat or application of a caustic substance.

Biological Effects of Electricity

There are primarily three types of effects produced on tissues by electrical energy. The first type is called Electrolytic effect where anions and cations in the body are attracted to opposite sides. This type of reaction is not conducive to life, and is produced by either low frequency alternating current or direct current. The second type of reaction is called Faradic effect, which is produced by high frequency alternating current up to 20 KHz. This type of current causes stimulation of nerve-endings and muscles, and is commonly used by physiotherapists and neurologists, and sometimes by general surgeons during parotid surgery to detect the branches of the facial nerve, etc. The third is the Thermal effect, which is produced by high frequency alternating current more than 300 KHz (also called radio-frequency AC).

There are basically three variable properties of electricity - Current, Voltage and Resistance. Current (I) is a measure of the electron movement past a given point in the circuit in a fixed period of time. It is measured as amperes. Voltage (V) is the pressure with which the electrons are pushed through the tissue. This is measured as volts. Resistance (R) is the measure of the difficulty that a given tissue presents to the passage of electrons, and is measured as ohms. Power (W) is the capacity to do work per unit time and is measured in watts. All this can be very easily understood using Odell’s Water-tower analogy.

Electro surgical Unit (ESU)

An Electro surgical Unit basically does two major functions. It converts a 60 cycles/second (60 Hz), low voltage alternating current into higher voltage radio frequency (500 KHz to 3.0 MHz) current. Secondly it is capable of producing current with a variety of waveforms.

Advantages of Electrocutting

u Reduced bleeding as there is simultaneous haemostatic effect. Preclusion of germ implantation, as there is heat produced in the vicinity, and as it is done by sterile technique.

u Avoidance of mechanical damage to the tissue.

u The possibility of using it in endoscopic surgery.

Types of Circuits

There are two types of circuits used to produce diathermy, Monopolar and Bipolar. In the Monopolar diathermy, the electricity travels from the ESU to the patient. The current enters the body of the patient and reaches the dispersive electrode (patient plate), which may be at a distance from the active electrode, and then returns the ESU. As, alternating current is used, the direction of current keeps changing several times every second. In the bipolar diathermy, the current passes through one limb of the instrument and returns through the other limb of the instrument. While doing so, it travels through the tissue grasped between the two limbs of the instrument.

In the Monopolar type the effect of the current is seen at close proximity to the active electrode, as the energy is concentrated here, and gets dispersed as it travels towards the dispersive or return electrode. The advantages of using the Monopolar Electrocautery are that it is easy to use and surgery can be performed much faster as it can be used as both cutting and coagulating current and thus can be used to dissect tissues also. The disadvantage is that larger volumes of tissue are injured and sometimes, distant burns can also occur. It requires a distant return electrode. It may also interfere with pacemakers. To prevent complications it is important to place the return electrode (patient plate) as close to the operating field as possible, so that the circuit runs only for a short distance in the patient’s body. Generally, it is advised to place the dispersive electrode around the arms or the thighs depending in which part of the body the surgery is being performed. The advantage of using Bipolar Electrocautery is that small volumes of the tissue are injured and there will not be any distant burns. It is a safe mode when used in patients with pacemakers. It is also effective in wet fields. The main disadvantage is that more skill and time is required to use bipolar Electrocautery, and that only coagulation current is available. Hence there is no dissecting capability. But some of the recent machines have incorporated the cutting mode also. Bipolar offers more safety when being used at close proximity to bowel and other abdominal viscera.

Tissue Effects of Electro surgery

There are three types of tissue effects of the radio frequency current, which is used for electro surgery - Vaporization (or Cutting), Desiccation (or Coagulation) and Fulguration (which is superficial coagulation). Vaporization and fulguration are non- contact procedures, and there is a small distance between the electrode and the tissue. The electrical spark travels through a steam bubble from the tip of the active electrode to the tissue to cause the particular effects on the tissue.

A high-frequency current with a sinusoidal waveform results in a pure cutting effect. The coagulation mode is produced by a series of dampened sinusoidal waves that are produced in rapid bursts. A combination of both cutting and coagulation effects is possible with a current that is a blend of the pure sinusoidal cutting current and the periodic dampened coagulation current. Altering the blended waveform can vary the relative cutting versus coagulation effect.

Mechanism of action (Cutting / Coagulation)

When an alternating current is used on a cell at a very high frequency (radio frequency), the anions and cations move to and fro within the cell with each cycle of the alternating current. This causes friction and results in increase in the intracellular temperature. Vaporization or cutting is caused by high current and low voltage. This causes a rapid heating of the cell and formation of steam inside. As a result there is an explosion due to the massive increase in volume of the intracellular contents, and lysis of the cell takes place. A low current and high voltage produces coagulation. This is a damped current and the flow of current is interrupted. Though the increased voltage causes deeper penetration into the tissues, the low current causes slow heating of the cell. This in turn causes dehydration of the cell and the cell shrinks in size. It is important to recapitulate the Ohm’s Law, which says: I = V/R This, when applied to the formula: W =VxI, =Vx(V/R) = V2 /R where, I = Current, V = Voltage, R = Resistance, and W = Power.

Hence the amount of work done (coagulation performed) is directly proportional to the voltage used and is indirectly proportional to the resistance offered by the nature of tissue on which it is used. A higher voltage leads to a higher spark intensity and a higher spark intensity results in a deeper zone of coagulation during the cutting process. The variables that affect the tissue effects of R-F current are as follows:

u Generator output

u Power density (Size and shape of electrodes)

u Electrode tissue proximity

u Tissue impedance

u Electrode speed / time on tissue

u Distension media.

Ideally when tissues have to be cut, a sharp electrode is used in the cutting mode, and the electrode is held at a small distance away from the tissue. Charring effect will be minimal when used in this way. It must be remembered that the electrical current generates the cutting effect of the electro surgical unit, not by the pressure of the electrode against the tissues/ There should be virtually no resistance to the movement of the tip of the electrode to the tissue. If resistance is encountered one must be sure that the active electrode is clean, that only the tip of the electrode is in contact with the tissue, and the power is at an adequately high setting. When fulguration (superficial coagulation) is desired, as while obtaining haemostasis over the liver bed, a ball electrode or a spatula is used in the coagulation mode, again holding the electrode at a small distance away from the tissue. If the electrode is pressed firmly over the liver surface, it would cause desiccation or deep coagulation. When coagulation or desiccation is desired, a flat electrode or a grasping instrument is used in the coagulation mode, in full contact with the tissue. While dissecting tissues and both cutting and coagulation are required, blended modes are used in different ratios of cutting and coagulation. The thickness of the electrode can be selected depending on how much coagulation effect is desired. The speed at which the electrode is moved determines the amount of contact and delivery of energy to the tissues, and thus the amount of coagulation and charring at the margins. If the coagulation current is used to incise tissue, tension and counter-tension has to be applied to the tissue, otherwise separation does not occur and it results in excessive thermal injury to neighbouring tissue. In laparoscopy, the Carbon dioxide gas used is not as good a conductor of the electrical energy as air, and thus would alter the performance of electro surgery. The power of the cautery should be set at the lowest possible setting to produce the desired effect of either cutting or coagulation, and prevent charring of neighbouring tissue.

When using the monopolar electrocautery to achieve haemostasis, it is important to remember that the electrical current will diffuse throughout any conductor of electricity including blood. Therefore, is imperative that the field in general be dry at the time of application of the current.

The bipolar cautery seals vessels by a coaptive technique. While using bipolar cautery, the tips of the forceps should not come in contact with each other. This will produce short-circuiting of the current and the tissue effects decrease. The tissue should be lightly grasped to allow a 1 to 2mm gap between the electrode tips. Coagulation with the bipolar forceps tends to be a self-limiting process since desiccation of tissue between the points will ultimately prevent further flow of current. For efficient use of the bipolar forceps, the tips must be free from the buildup of charcoal and coagulum. Therefore, frequent cleansing of the tips is required.

Electro surgical burns

During application of elecrosurgery three main types of burns can occur :

u Endogenous burns

u Exogenous burns

u Psuedo burns

ENDOGENOUS BURNS

Endogenous burns are always a result from a too high current density in the patient’s tissue. At the active electrode there is a need for high current density in order to cut or coagulate tissue, but accidental pressing of the foot pedal or use of the electrocautery for a longer time or extent can cause burns. There are three mechanisms in which inadvertent burns can occur during use of monopolar electrocautery in laparoscopic surgery.

Direct Coupling:

The common cause by which this occurs is when there is insulation failure or when the whole metal part of the instrument is not being visualized while using elecrocautery. The instrument may be touching some other tissues outside the laparoscopic visual field, where the instrument may not be insulated adequately. At such a time the current passes to that tissue and causes burns there.

Indirect Coupling:

There can be another instrument which can conduct electricity (like telescope, grasper, etc.,), in close proximity to the instrument through which electricity is passing and the energy can jump and get transferred to this instrument also. Supposing there is some other tissue in close proximity to this instrument then there can be burns of this tissue, which is located for away from the site of surgery. This burn may go unnoticed.

Capacitive Coupling:

There is certain amount of energy that leaks on to the reducer if it is made of metal, and usually if the reducer is in contact with a metal canula on its outer aspect, the energy is dissipated on the abdominal wall. In turn the energy goes to the dispersive plate and returns to the E.S.U. But if the reducer is not able to let out the energy (because the outside canula is made of a non-conducting material, like plastic), it gets accumulated in the reducer. When a loop of intestine or some other viscera comes in close proximity to the reducer, it suddenly discharges all the energy to that tissue and can result in burns there. Either using both metal reducer and canula, or both being made of nonconducting material can prevent this. The risk of capacitive coupling burns exists when a combination of metal and plastic ports is used. Certain modifications are incorporated in some new Electro surgical units, like Electrosheild and monitoring devices which are capable of either preventing accumulation of extra energy in the portals or carrying back this energy to the E.S.U.

The usual causes of endogenous burns other than those mentioned are as follows:

u Patient plate is too small

u Patient plate is not covering the patient’s tissue with its entire area. ( atleast 75% area should be in contact )

u Unintentional contact to other electrically conductive parts, e.g., drip stand or metal parts of the operation table, etc.,

Sometimes there may be concentration of energy at the patient plate or at areas where the patient comes into contact with electric-conductive parts. The current density becomes so high as to burn the patient’s tissue.

EXOGENOUS BURNS

Exogenous burns are caused from the heat of burning substances such as skin-cleansing lotions, degreasants and disinfectants, also anesthetics, which have been ignited by sparks between the active electrode and the patient’s tissue. Note that alcohol usually burns as invisible flames, since the operating lamp illuminates brighter than the flame does. This way the patient-burn can only be recognized after it has happened.

PSEUDO BURNS

From time to time minor or major necrosis are found with patients and are regarded as burns but without finding any explanations or reasons of how these burns have been caused. Endogenous burns can be excluded when the patient did not have contact with electric-conductive parts at the area where the necrosis is found. Exogenous burns can also be excluded when before or during electro surgery no flammable substances were used.

The causes of these burns must be found out by differential diagnosis: Necrosis caused by pressure to the patient’s tissue: During long operative procedures pressure to the patient’s tissue can cause necrosis, for example, during heart surgery when the patient is hypothermic a large tissue necrosis was found post-operatively. Pressure to the patient’s skin caused by rubber-straps being used to fix and attach the patient plate or by contact-clamps being put underneath the patient can again cause necrosis. In many cases this is erroneously diagnosed as patient-burn. During electro surgery patient-burns can only occur when the before mentioned facts exist. It is possible to prevent patient-burns safely when the operating team knows and observes the causes as well as pays attention to these before and during electro surgery.

SAFETY PRECAUTIONS

The following steps should be followed carefully while using electro surgery:

u All connections are carefully checked before the ES unit is put on. u The patient plate used is always one recommended by the manufacturer.

u The patient plate must always be applied by covering the patient with its entire area as best as possible.

u The conductive surface of the patient plate must always be clean and free from corrosion.

u If gelled patient plates are used, it is most important that the gel is evenly applied over the entire conductive area of the patient plate.

u Prior to use, the patient plate must be checked for damage, especially patient plates made of aluminum foil.

u It is important that the patient plate is applied with the electrically conductive surface to the patient’s skin and not with its wrong side.

u The patient plate is applied as close to the operative site as possible.

u Care must be taken that no electrical conductive fluids come between the patient’s skin and the patient plate.

u The patient is insulated against all electrically conductive objects by a thick, dry, electrically insulating sheet, placed between the patient, the operating table and the supports. The sheets must not become damp. Areas subject to considerable secretion of sweat, body extremities lying against the trunk or skin-to-skin contacts should be separated by the application of a dry cloth. Drain off urine with catheter.

u During electro surgery always sparks exist between the active electrode and the patient’s tissue.

Therefore do not use flammable or explosive substances or gases during electro surgery. If flammable or explosive substances have been used, these must be completely removed before activating the electro surgical unit.

A special precaution to be taken during laparoscopic surgery is that electro surgery should not be used whenever there is bowel perforation. Bowel contains Methane gas, which is released into the peritoneal cavity whenever there is a bowel perforation, and if electro surgery is used at such a circumstance, it may lead to an explosion.

Assuming good surgical technique and good endoscopic instrumentation with intact insulation, correct connection of cables and proper placement of neutral electrode would go a long way in making this efficient tool safe and a boon to the surgeon especially in the era of laparoscopic surgery.

Argon Beam Coagulation

Like the standard electrocautery units, the argon beam coagulator uses high-frequency oscillating current to generate coagulating heat. The argon beam coagulator differs from standard electrocautery in that it uses a spray of ionized argon gas as the active electrode rather than a metallic blade. This spray allows even, efficient, and broad application of the coagulating current to the tissues. The argon beam coagulator consists of a current generator, a grounding pad, and a handheld active electrode. The device is activated by a foot pedal that initiates the flow of pressurized ion gas through the end of the handheld unit. Once a solid column of gas connects the handheld active electrode to the patient, the electrical current arcs across the argon gas to the tissues. The type of current used with the argon beam coagulator is almost identical to the type used with standard electrocautery. To use the argon beam coagulator, the handheld unit is held like a pencil with the end directly pointed at the tissue from a distance of 1 to 2 cm. The person holding the active electrode also activates the foot pedal. (Tate’s rule). A jet of argon gas is emitted from the end of the handheld unit, completing the circuit between the argon beam coagulator and the patient. The cautery current is delivered to the surface of the tissue in contact with the argon stream.

To cauterize large surface areas, the unit can be used like a paintbrush using slow small strokes across the tissues. The power settings on most units range from 0 to 150 watts. As with the standard electrocautery, conduction is dependent on many factors, including the conductivity of the tissue. Therefore, it is recommended to start with a relatively low power setting of 50 to 60 watts and increasing as necessary. Because of its efficiency in coagulating large irregular surfaces, the argon beam coagulator is ideal for obtaining hemostasis along the cut surface of the liver following hepatic resection. The argon beam coagulator can also be helpful in controlling bleeding from minor splenic trauma or other oozing surfaces. It has also been used as a means of tumor debulking by fulgurating metastatic ovarian carcinoma. The argon beam coagulator offers some advantages over conventional electrocautery in that with the argon beam coagulator there is no physical contact between the active electrode and the tissues. This lack of physical contact means that no adhesion of the active electrode to the tissue occurs, which allows for improved eschar integrity. In addition, there is no need to clean the char from the instrument. The flow of argon gas blows the blood and secretions away from the solid tissue to be coagulated, allowing for effective and efficient coagulation of tissue surfaces that are actively oozing, and less smoke is generated than with conventional electrocautery.

The argon beam coagulator has some disadvantages: its lack of precision and its expenses both with the unit itself as well as the consumable argon gas. In addition, although the argon beam coagulator is excellent at standard coagulation function, it has no coaptive capabilities and is very limited as a dissecting tool. Because the argon beam coagulator is essentially a monopolar electrocautery device, all precautions applicable to monopolar cautery should apply to the argon beam coagulator. Because of the risk of possible injury, it is better to avoid the use of the argon beam coagulator in close proximity to delicate structures such as intestines, major vascular structures, ureters, and bile ducts. With the argon beam coagulator’s relative lack of precision, special precautions should be taken to avoid current diversion through metallic instruments or retractors. Inadvertent activation of the pedal can result in significant injury and fire, and so the argon beam coagulator should always be stored in a plastic holster when not in use. Use in laparoscopic surgery has been difficult as the abdomen is a closed cavity and there can be a sudden rise in the intra-abdominal pressure with flow of the argon gas into the abdomen.

Cryotherapy

Cryotherapy is a technique of in situ tissue ablation that uses freezing temperatures to cause cell death. Cryotherapy has been used to treat a variety of benign and malignant lesions. For several decades, in situ destruction of tumor by Cryotherapy has been used for cutaneous lesions. More recently, this mode of therapy has been applied to tumors of the head and neck, cervix, rectum, prostate, breast, and liver. Today sophisticated cryoprobes are available for the delivery of extremely low temperatures by means of pressurized liquid nitrogen. The probes come in varying sizes with differing capabilities. The delivery systems are complex, and their use requires personnel with special expertise in their operation and maintenance.

Although this technology is new and to a degree still unproven, ultrasound-assisted cryotherapy appears to have great promise in the treatment of liver tumors. In situ cryodestruction of tumor is best applied to unresectable or multiple liver metastases from colorectal cancer, where complete tumor ablation may lead to improved long term survival.

Cryotherapy causes tumor destruction and cell death by a combination of several possible mechanisms. These mechanisms include cold shock injury, reduction of cell volume by osmotic dehydration, denaturation of vital cellular enzymes, perforation of cell membranes by intracellular ice crystals, and destruction of tumor microvasculature. To ensure complete cell death, temperatures in the tissue should be lowered to below - 35degree C, maintained in the frozen state for at least 3 minutes, and then slowly thawed. The thawing cycle is particularly important, because too rapid or too slow thawing will allow survival of a portion of the tumor cells. For this reason, at least two freeze-thaw cycles should be applied to each tumor to ensure complete cellular destruction.

Infrared Coagulator

The infrared coagulator generates coagulation heat energy by infrared irradiation. The infrared coagulator consists of a transformer unit with a foot pedal switch and a handheld wand. The wand is round metallic cylinder that generates the infrared light that emanates through the crystal lens as the end of the wand. The heat energy produced by the infrared irradiation causes rapid heating of the tissues in contact with the crystal, and these heating results in desiccation and coagulation. The infrared coagulator is most useful for coagulating oozing tissue surfaces such as the cut edge of the liver following hepatic resection. The flat crystal is pressed against the tissue in a manner such that little or no light can escape from the end of the wand. The foot pedal is then pressed to activate the wand and generate the infrared irradiation. Approximately 1 to 2 seconds of exposure is usually sufficient to result in tissue coagulation and hemostasis, which are signified by the boiling of fluids at the edge of the crystal and the generation of a small amount of smoke. It is important that the wand not be pulled away from the tissue until the infrared generation has ceased. After each application, the end of the wand should be wiped with a moist sponge to cool the crystal and to remove char from the tip. The infrared coagulator is an effective device for coagulating oozing surfaces and has the advantage of not requiring electrical current to pass through the patient. Hence, the infrared coagulator does not interfere with ECG monitoring or pacemaker function.

Ultrasonic Dissector

The ultrasonic dissector is a surgical tool that uses high-frequency mechanical vibrations to fragment tissue. Developed in the late 1960s, this technology was originally applied to ophthalmic surgery, but has gained wide use in neurosurgery, hepatobiliary surgery, and oncologic cytoreductive surgery. The ultrasonic dissector system consists of a rather bulky hand piece connected to a function control console that is controlled by a standard foot pedal. The end of the handheld unit consists of a metal contact probe that vibrates at a frequency between 20,000 and 40,000 times per second. Because this vibration frequency is above the audible range, it is referred to as ultrasonic. No audible sound or electromagnetic radiation is emitted and the vibrating tip must be in direct contact with the tissues to bring about its effect. Transducers that rely on piezoelectric crystals or magnetostrictive laminations to convert electrical energy into mechanical vibrations generate the vibrations.

The ultrasonic dissector fragments tissue by contact with high water content cells. The vibrations generate vapor pockets within the cells that lead to cellular disruption and fragmentation. While fragmenting high water content cells, the dissector does not rapidly disrupt collagen-rich tissue such as blood vessels and ducts. Hence, the device can divide parenchymal tissue while leaving blood vessels intact so that they can be individually ligated prior to division.

The most common general surgical application of the ultrasonic dissector is for the division of the liver parenchyma during hepatic resection. In addition to its use as a dissecting tool, the ultrasonic dissector can be used as a means of tissue ablation. It has been extensively applied in cytoreductive surgery in the treatment of metastatic ovarian cancer. Ovarian epithelial cancers tend to have high water content with very little fibrous stroma; hence, these tissues readily fragment with the ultrasonic dissector. When the ultrasonic dissector is used for this purpose, it is important to be aware that tumor infiltration can involve full thickness penetration of hollow or tubular structures such as intestine, bladder, and blood vessels. Therefore, it is important that the surgeon be prepared to deal with possible perforation of these structures. With this in mind, it is always better to order for complete mechanical bowel cleansing with prophylactic intravenous antibiotics for patients undergoing cytoreductive surgery. Additionally, prior to applying the ultrasonic dissector to a tumor that is in close proximity to major vascular structures, it is advisable to first gain proximal and distal control of the vessel.

The ultrasonic dissector is a convenient way of dividing solid organ parenchyma with little blood loss. When used appropriately, this device is relatively safe and mishaps are infrequent. The ultrasonic dissector has some disadvantages. Its high cost, the bulkiness of the unit itself, and it has not been demonstrated to be consistently superior to standard dissecting techniques. For most routine liver resections, we can use a combination of electrocautery and finger fracture technique for noncirrhotic livers and reserve the ultrasonic dissector for patients with mild to moderate cirrhosis.

Ultrasonic knife

The ultrasonically activated scalpel comprises of a high frequency computer controlled generator, which converts incoming electrical signals into mechanical vibrations at 55.5 kHz at the blade tip via a hand piece transducer. The amplitude of motion amounts of 50-100 microns depending on the power setting. The moving blade couples with the tissue, resulting in breakage of protein hydrogen bonds and thus protein coagulum forms. This coagulum seals off blood vessels. The whole process operates at 80 degrees C, minimizing undesirable tissue damage due to high temperatures.

The ultrasonic knife can perform cutting and haemostasis with minimal tissue damage, and visibility may be improved, as there is less smoke. Energy flows in a longitudinal direction thus limiting its lateral spread and thermal injury. Unlike electro surgery, no electrical energy is transferred to patients, and extra safety can be ensured. In addition, the linear relationship between variables such as duration of application does not plateau, making the system more controllable as injury occurs gradually and reproducibly over time. The range of blades available serves both open and laparoscopic surgery. They are available in both 5 and 10 mm. diameter for laparoscopy. In addition to the grasping instrument, various other types are available such as the hook or the ball coagulators.

Though used for many surgeries, the most studied application is in laparoscopic fundoplication, in which short gastric vessels are cut haemostatically. Other applications include laparoscopic colectomy, adrenalectomy and gastric surgery besides others.

Lasers

The term “Laser” is an acronym, which stands for Light Amplification by the Stimulated Emission of Radiation. The word radiation does not mean ionizing type of radiation, but refers to a “radiant” body, i.e., one that “shines” with light energy. Light is comprised of photons of energy. The normal tendency of light is to scatter in all directions. Laser light contains of photons released in an organized fashion called stimulated emission.

Three unique qualities of laser light that differentiate it from regular light are its coherence, monochromaticity and collimation. Coherence means that the wave patterns of the light energy being emitted in a laser are orderly and similar. The laser waves ore always precisely in phase with one another, temporally and spatially. This property of a laser would be of use for diagnostic and scanning applications. The term monochromaticity means that lasers produce pure colors of light. They are always of the same wavelength and energy level. This is a property that is useful for us because of the fact that different tissues absorb various colours differently. Various chemical elements emit characteristic colors of light, and the laser is named after the material used. The term collimation means that laser light travels with all its waves bound tightly together, as a parallel beam in space. This particular property of lasers is what allows the beam to be finely focused to intensify its effects and is the major characteristic allowing its surgical use.

The surgical effects of the laser are due to localized heating when the tissues absorb the light. As tissue begins to heat, it blanches white as it coagulates, then shrivels as it desiccates, and finally turns to steam and vapor as it is vaporized above 100 degrees C. The heat-generating effect of the lasers is used for surgical applications. Lasers produce heat that is localized and produce desired surgical effects with associated haemostasis. There are five types of lasers primarily being used for surgical applications. They are Carbon dioxide (CO2), Nd:YAG (Neodymium: YAG), argon, Ho: YAG (Holmium: YAG) and the KTP (produced by altering the infrared output of the Nd:YAG laser with a KTP crystal). These lasers are used in two basic ways. One is a noncontact method whereby the laser light is absorbed by tissue and heat is generated. The other is the contact method by which the laser heats special fibre tips and this heat is in turn transferred to the tissue by contact with the fibre.

The factors that determine the amount of laser that is delivered to the tissue are:

u Power (watts) with which the delivery system is operated.

u Duration for which it was operated.

u Power density (the size of focused spot used to intensify the light).

u Color of the laser light.

u Color and vascularity of the tissue.

The surgeon can control the power setting, the duration of application and the spot size of the beam, and thus modify the effect of the laser on tissue. A laser beam can be used either as a continuous mode or a pulsed mode. A pulsed mode is a brief beam, which is delivered in fractions of a second. This type of delivery gives a good control to the surgeon to deliver precise doses of high power. This type of delivery provides a longer reaction time and produces less spread of heat damage to the distant organs. In the absence of such a mode of delivery in the laser machine, operating the foot pedal appropriately to produce controlled bursts can still use a pulsed mode.

Any type of lasers can be used to cut or vaporize by altering the way it is used. For laparoscopic surgery we could use a CO2 laser laparoscope, or regular fibres to deliver argon, KTP, Ho:YAG and free beam Nd:YAG lasers. In a CO2 laser laparoscope, the laser beam first focuses to a point and then diverges. Hence it maintains a long depth of field and it can burn or vaporize tissues distal to the target organ or tissue. Therefore while using this laser, it is essential to have a backstop to prevent distal injury. When a fibre is used the beam starts of diverge immediately distal to the beam. Hence this beam does not stay focused beyond an inch or two from the tip of the fibre. The advantage of the fibres is that different effects can be accomplished quickly with only a slight motion of the fingers holding the fibre hand-piece. A small pinch back with the fingers allows small blood vessels to be photocoagulated, then a small pinch forward to bring the fibre end just over tissue results in a cut, both at the same power settings on the machine. The short range of effect also reduces the need for intraabdominal backstops. The argon and KTP are the primary fibreoptic lasers for laparoscopy besides contact type modalities, which are mainly Nd: YAG lasers.

The CO2 laser provides a great deal of versatility in the “reach” it provides from the end of the laparoscope, the number of angles where it can work, and the speed at which it can vaporize or cut if desired. In this sense it is probably more versatile than a fibre system, but it has a significant longer learning curve and does not provide the hemostasis than fibre systems provide. It also requires a specialized laparoscope set and coupler to mate the laser with the scope.

Fibres terminating in some device such as a metal tip, sapphire probe, or even an altered shape of the fibre tip generate a significant amount of heat at this tip and are referred to as hot tip devices. They act as very intense, precise knives. Energy concepts such as power density do not really apply to contact devices, since they rely on simple heat conduction. The Nd: YAG laser is the primary one used for hot tip devices in laparoscopic surgeries. Some of the hot tip devices, such as rounded or chisel sapphire tips, do actually focus some of the laser light, so that combination effects may occur. A combination rounded tip fibre can be backed off from the tissue to vaporize or coagulate as free beam or touched to tissue to cut as a hot tip.

The safety of the patient and the operating team is very important. Trained, experienced assistants are invaluable during laser procedures. Operation theatres must be clearly labelled on the outside door indicating that a laser procedure is in progress. The window in the operating room must be covered. The type of laser must be specified on the “danger” sign. The optical density for protective eye wear must be appropriate for the wavelength of the laser being used. All personnel, including the anesthesiologist and assistants, must wear safety goggles or appropriate protective eye wear. It is absolutely essential that flammable substances or explosive solutions be avoided in the operating room during laser usage. Special care must be taken when using paper drapes. When using CO2 lasers the area surrounding the operative field should be draped with moist laps. The patient’s eyes must also be appropriately protected with moist gauze or dressings.

The production of smoke after tissue destruction with the lasers has led not only to respiratory complications, but has been implicated as a possible source of mutagenicity. Approximately 75% of the solid particulate matter in laser plume is less than 1 micron. When inhaled, this small particulate matter is capable of traveling directly to the distal tracheopulmonary tree and being deposited in individual alveoli. To eliminate 99% of the generated plume, a suction device that can mobilize 28 litres of air/sec when held 1 cm from the origin of the laser plume is needed. Although CO2 laser laparoscopy is associated with more plume formation than the Argon, Nd: YAG, or KTP lasers, adequate smoke evacuation systems are still mandatory when using the latter three wavelengths.

There are no prospective, blinded studies comparing laparoscopic use of lasers with conventional electro surgery, which have demonstrated a reduction in adhesion formation or an improvement in pregnancy rates. Its use to date is based on the clinical impression primarily of the surgeon. Many surgeons advocate the use of lasers because of their controlled depth of penetration, reduced thermal damage to adjacent tissue, and the reproducibility of the effects of lasers on tissue.