Washington University School of Medicine St. Louis, Missouri
Guide to Pain Management in Low-Resource Settings Chapter 5 Ethnocultural and Sex In uences in Pain Angela Mailis-Gagnon Case reports health care providers medicine 4839 effective 500 mg antabuse. Maryann Bates [1] medications you can take while pregnant for cold generic antabuse 500mg mastercard, a professor at the School of Education and Human Development at A 40-year-old male patient comes to see you symptoms nicotine withdrawal purchase antabuse 250mg amex. He is Chi the State University of New York medicine vile antabuse 250 mg otc, studied pain patients nese and has been in a Western country for 2 years schedule 8 medications list buy antabuse with a mastercard. While you try to obtain in culture re ects the patterned ways that humans learn formation for the neck pain that brought him to you treatment xerosis order line antabuse, he to think about and act in their world symptoms 4 days after ovulation purchase 250mg antabuse overnight delivery. Is he styles of thought and behavior that are learned and depressed or does he simply disrespect you A 25-year-old woman with a hijab and tradi In this context medicine prescription purchase antabuse 250mg fast delivery, culture is di erent than ethnicity. The tional Moslem attire is brought in by her husband in re latter refers speci cally to the sense of belonging in a par gard to di use body pain complaints. Given the fact that this doctor is the traits such as religion, language, ancestry, and others. Why is it important to understand A 75-year-old farmer with elementary school ethnicity and culture when it comes education sees you for severe knee arthritis. He cannot tolerate nonsteroidal anti-in ammatory medications to pain diagnosis and management His pain responds very well to Culture and ethnicity a ect both perception and ex small doses of controlled-release morphine. However, he pression of pain and have been the focus of research becomes very nauseated and throws up every time. Research with adult twins supports becomes visibly upset when you o er him Gravol sup the view that it is the cultural patterns of behavior and positories after you explain to him how to use them. This material may be used for educational 27 and training purposes with proper citation of the source. In another Can cultural in uences increase experimental study, when Jewish and Protestant women and decrease pain perception In certain parts of the world such as the rst place had tolerated lower levels of shocks to India, the Middle and Far East, Africa, some countries start with. It is well known that our brains emit dif nic groups can change, as they are shaped and reshaped ferent wave frequencies during activities or sleep. Another kind of brain waves called theta waves are Caucasians or African Americans. The hook-hanging complain of more pain than Caucasians during scoliosis devotees actually displayed theta waves throughout all surgery, while Mexican-Americans report more chest the stages of the process. Larbig was also fascinated by the amaz fact that only 10% of adult dental patients in China rou ing things that fakirs do and investigated a 48-year-old tinely receive local anesthetic injections from their den Mongolian fakir. This man could stick daggers in his tist for tooth drilling compared with 99% of adult pa neck, pierce his tongue with a sword, or prick his arms tients in North America. All these studies and the ones with long needles without any indication of pain or Ethnocultural and Sex In uences in Pain 29 damage to his esh. Hypnosis makes the person more prone to procedure which is performed by inserting a needle at suggestions, modi es both perception and memory, and the back of the spine, on the surface of the spinal cord). Again, these studies are summarized in the observed to stare ahead to some xed imaginary point popular science book, Beyond Pain [3]. However, when he n ished his performance, he would return quickly to a between ethnic groups Amazingly, while the fakir did not feel any pain iors that in uence the thoughts and actions of the mem during his act, he complained bitterly (when he had re bers of a given cultural/ethnic group. Such be Another extreme example of cultural in uenc liefs result from interaction of cultural background, es in reducing perception and expression of pain is the socioeconomic status, level of education, and gender. During the procedure, done up is wrong with them and what they should expect from to the early 21st century for a number of reasons, the health care providers. Furthermore, the way patients re patients do not receive any form of analgesia or anes port pain is shaped to a certain degree by what is sup thesia. The doktari or daktari (tribal doctor) cuts the posed to be the norm in their own culture. For example, muscles of the head to uncover the bony skull in order some ethnocultural groups use certain expressions ac to drill a hole and expose the dura. Trepanation (evi cepted in their own culture to describe painful physical dence of which has been found even in Neolithic times) symptoms, when in reality they describe their emotion was done for both medical reasons, for example intra al distress and su ering. Research studies show that women use high acute, chronic, and cancer-related pain. Tese di erenc er health care services per capita as compared to men es in treatment may arise from the health care system for all types of morbidity and are more likely to report itself (the ability to reach and receive services) or from pain and other symptoms and to express higher distress the interaction between patients and health care provid than men. Furthermore, women in a deprived socioeco ers, as beliefs, expectations, and biases (prejudices) from nomic situation run a higher risk for pain. Patients may be treated by health care providers From the biological point of view, females are who come from a di erent race or ethnic background. Additionally, cer from ethnic di erences between patients and medical tain genetic factors unique to women may a ect sensi professionals have been shown in di erent studies dem tivity to pain and/or metabolism of certain substances. For example, in one study, women with arthri algesia in the emergency room or be prescribed certain this reported 40% more pain and more severe pain than amounts of powerful pain-killing drugs such as opi men, but were able to employ more active coping strat oids. However, worldwide di erences in administra egies such as speaking about the pain, displaying more tion of opioids in non-white nations are not solely due nonverbal pain indicators such as facial grimacing, ges to health provider/patient interaction, but may relate tures like holding or rubbing the painful area or shifting to system politics. One of the explanations for di erences cess of cancer patients to opioids in Mexico. It is believed that this greater role makes women ask people with diverse ethnocultural backgrounds, but questions or seek help in an e ort to maintain them such knowledge is necessary to improve diagnosis and selves or their family in a good condition. Ethnocultural and environmental factors also account partially for di erences in perceiving and re porting pain or other symptoms. For example, a few What is the e ect of gender on studies have shown higher pain perception and expres pain perception and expression and sion in South (Central) Asian groups (including patients health care utilization Altogether, the no physiological di erences when subjects were tested di erences between genders can be attributed to a com for warm and cold perception (this means the level at bination of biological, psychological, and sociocultural which a stimulus was felt as warm or cold). The researchers felt that maybe these pa moved to variable degrees or are of mixed back tients were sent by their doctors to the pain clinic with ground through intermarriage. This may indeed make sense merous factors in account in order to re ect the because South Central Asians constitute the most re complex reality of culture and ethnicity and their cent wave of immigrants to Canada, and therefore stress in uence not only in pain perception and expres of immigration may be substantial. Understanding how race and ethnicity in uence relationships in parities in clinical situations; plan and implement health care. Beyond pain: making the body-mind prospective studies to detect disparities; develop connection. Ethno cultural, ethnic, and linguistic di erences; clarify cultural and gender characteristics of patients attending a tertiary care pain clinic in Toronto, Canada. Racial and ethnic identi ers in pain management: the im in pain management; examine racial and ethnic portance to research, clinical practice and public health policy. A peripheral trauma the right analgesic will initiate peripheral hyperalgesia, which results from a Recently, a good friend of mine drove home on his bi prostaglandin-induced increase in nociceptor sensitivity. Tere Also, central hyperalgesia is initiated from the blockade after, he su ered from chest pain and asked his doctor of the activity of interneurons due to the production of for help. He called the next morning telling me that results in phosphorylation of the glycine-receptor-asso he had fallen asleep shortly after having taken diclofenac. Tis, in turn, reduces the prob this example demonstrates that so-called ability of chloride channel opening. A drug like diclofenac (an aspirin-like in ammation, and tissue damage activate the production drug) often does a better job. This material may be used for educational 33 and training purposes with proper citation of the source. Tose that are eliminated quickly have a sion and thus exerts an antihyperalgesic e ect. Again, blockade of prostaglandin production So, why did I recommend diclofenac reduces peripheral hyperalgesia. Going back to the case report, the acute trauma caused peripheral and central hyperalgesia within half The reasons I recommended diclofenac to my friend an hour. This may lead to delayed absorption, words, this group comprises relatively weak compounds and consequently, lack of fast pain relief. They di er in their phar hand, diclofenac, once absorbed, is eliminated quickly macokinetic behavior and some of their unwanted drug by metabolism. Consequently, to have a prolonged ef e ects that are not related to their mode of action. A man, aged 71, complained about excruciating pain in this group of drugs exerts analgesia via inhibition of his spine. The di erences, however, re cinoma, the growth of which was not completely con sult from their pharmacokinetic characteristics (Table 1). Examples are layer of in ammatory cells produces many prostaglandins, acetaminophen, celecoxib, and etoricoxib. Still, since most and su ered a complete compression of the spinal cord neuronal cells in our body comprise voltage-gated so between C4 and C5. Tese compounds must blood coagulation for up to 5 days and consequently se therefore be dosed cautiously in order to produce thera rious risks for neurosurgery. Her standard medication of dipyrone was not Are there options to block calcium channels e ective. However, it caused the woman to be calcium channels) that play a role in the communication sleepy and dizzy all the time to an extent that did not between cells. Unfortunately, as oral as these N-type channels are present in most neuronal bioavailability is unpredictable, only the intravenous cells, a general blockade would be incompatible with route can be used. But recently ziconotide, a toxin from a sea snail, has been found to block these channels when administered Pearls of wisdom directly into the spinal column, with tolerable side ef fects. In oth receptors are not limited to the pain pathway, but are er words, the normalization of hyperalgesia ends ubiquitously involved in neuronal communication. Increasing the dose will not increase not be limited to pain pathways, but a certain degree of the e ect any further. Consequently, the use of ketamine is restricted including acetaminophen (paracetamol). The discovery and development of antiin ammatory terminal pro-B-type natriuretic Peptide concentrations predict the risk drugs. Guide to Pain Management in Low-Resource Settings Chapter 7 Opioids in Pain Medicine Michael Schafer Classi cation of opioids introduction of the glass syringe by the French ortho pedic surgeon Charles Pravaz (1844), much easier han Treatment of pain very quickly reaches its limits. Any dling of this unique opioid substance became possible one who has su ered from a severe injury, a renal or gall with fewer side e ects. In codone, diacetylmorphine (heroin) and from fully syn contrast to many other pain killers, opioids are still the thetic opioids such as nalbuphine, methadone, pentazo most potent analgesic drugs that are able to control se cine, fentanyl, alfentanil, sufentanil, and remifentanil. This quality of opioids was known dur All these substances are classi ed as opioids, including ing early history, and opium, the dried milky juice of the the endogenous opioid peptides such as endorphin, en poppy ower, Papaver somniferum, was harvested not kephalin, and dynorphin which are short peptides se only for its euphoric e ect but also for its very powerful creted from the central nervous system under moments analgesic e ect. Overdosing occurred quite often, with many tors for opioids were rst discovered within specif unwanted side e ects including respiratory depres ic, pain related brain areas such as the thalamus, the sion, and, because of irregular use, the euphoric e ects midbrain region, the spinal cord and the primary sen quickly resulted in addiction. Accordingly, opioids produce potent With the isolation of a single alkaloid, mor analgesia when given systemically. This material may be used for educational 39 and training purposes with proper citation of the source. However, the Dose titration and regular assessments of pain intensity most relevant is the opioid receptor, since almost all and breathing rate are recommended. During prolonged clinically used opioids elicit their e ects mainly through and regular opioid application, respiratory depression is its activation. Cognitive impairment is an im receptors within the cell membrane forms a pocket at portant issue at the beginning, particularly while driving which opioids bind and subsequently activate intracellu a car or operating dangerous machinery such as power lar signaling events that lead to a reduction in the excit saws. However, patients on regular opioid treatment ability of neurons and, thus, pain inhibition. According usually do not have these problems, but all patients have to their ability to initiate such events, opioids are dis to be informed about the occurrence and possible treat tinguished as full opioid agonists. Constipation is a typical opioid occupancy for maximal response, partial opioid agonists side e ect that does not subside, but persists over the. It can lead to serious clinical cupancy even for a low response, and antagonists. However, after a few days these ics used to induce unconsciousness during surgical pro symptoms subside and do not further interfere with the cedures. Patients should be slowly titrated Muscle rigidity to the most e ective opioid dose to reduce the severity of the side e ects. In addition, symptomatic treatments Depending on the speed of application and dose, opi such as antiemetics help to overcome the immediate oids can cause muscle rigidity particularly in the trunk, Opioids in Pain Medicine 41 abdomen, and larynx. This problem is rst recognized to 3 40 mg/day orally), which is mandatory during by the impairment of adequate ventilation followed by chronic opioid use. Life-threatening di culty in assisted venti lation can be treated with muscle relaxants. Although pruritus may be due to a generalized Respiratory depression is a common phenomenon histamine release following the application of morphine, of all opioid agonists in clinical use. The fundamental drive mg orally) or with less impact on the analgesic e ect by for respiration is located in respiratory centers of the mixed agonists such as nalbuphine. Routes of opioid administration Life-threatening respiratory arrest can be reversed by titration with the i. The majority of opioids are easily absorbed from the Antitussive e ects gastrointestinal tract with an oral bioavailability of 35% In addition to respiratory depression, opioids suppress. The where glucuronic acid binding makes the drug inactive main antitussive e ect of opioids is regulated by opioid and ready for renal excretion. Tere is pre cause smooth muscle spasms of the gallbladder, bili liminary evidence for ethnic di erences. More common practice, however, is the coad follow the same goals: a convenient and reliable way of ministration of laxatives such as lactulose (3 10 mg application, a fast onset of analgesic e ect, and bypass 42 Michael Schafer of hepatic metabolism. Sublingual/nasal Only highly lipophilic substances such as fentanyl and mg, and a 24-h dose of 3.
Previous abdominal surgery increases the incidence of adhesions of the bowel to the anterior abdominal wall medications lexapro purchase discount antabuse line, frequently near the umbilicus and in the path of the primary trocar-cannula system (88 medications you can crush purchase 250mg antabuse amex, 89) symptoms of strep throat buy antabuse 250mg mastercard. Using such a laparoscope symptoms type 2 diabetes antabuse 250 mg line, the presence of adhesions under the incision can be identified and the umbilical cannula can be inserted under direct vision 5ht3 medications cheap antabuse 250mg mastercard. If adhesions are noted under the incision medicine bow national forest 250mg antabuse otc, appropriate placement of secondary cannulas may be used to introduce instruments for adhesiolysis medicine quiz purchase antabuse 500 mg visa. Ancillary Cannulas Ancillary cannulas are necessary to perform most diagnostic and operative laparoscopic procedures 4 medications list at walmart buy antabuse uk. Most currently available disposable ancillary cannulas are identical to those designed for insertion of the primary cannula; however, simple cannulas without the so called safety mechanisms and insufflation ports are generally sufficient (Figs. Proper positioning of these ancillary cannulas depends on a sound knowledge of the abdominal wall vascular anatomy. For the secondary puncture, the patient may be tipped head down (Trendelenburg), allowing the abdominal contents to shift from beneath the incision sites, and thus making it unnecessary to lift the abdominal wall during secondary cannula insertion. Alternatively, the intraperitoneal pressure may be maintained at 25 to 30 mm Hg to allow insertion of the secondary cannulas prior to placing the patient in the Trendelenburg position. Ancillary cannulas should always be inserted under direct vision because injury to bowel or major vessels can occur. For diagnostic laparoscopy, the most useful and cosmetically acceptable site for insertion of an ancillary cannula is in the midline of the lower abdomen, about 2 to 4 cm above the symphysis. The ancillary cannula should not be inserted too close to the symphysis because it limits the mobility of the ancillary instruments and access to the cul-de-sac. Laparoscopic cannulas can become dislodged and slip out of the incision during a procedure. There are a variety of cannula designs designed to reduce slippage, which include those with threaded exteriors and anchoring systems with balloon tips. Lateral placement of lower-quadrant cannulas is useful for operative laparoscopy, but the superficial and inferior epigastric vessels must be located to avoid injury (Fig. Transillumination of the abdominal wall from within permits the identification of the superficial inferior epigastric vessels in most thin women. The deep inferior epigastric vessels cannot be identified by this mechanism because of their location deep to the rectus sheath. The most consistent landmarks are the medial umbilical ligaments (obliterated umbilical arteries) and the exit point of the round ligament into the inguinal canal. At the pubic crest, the deep inferior epigastric vessels can often be visualized between the medially located umbilical ligament and the laterally positioned exit point of the round ligament. The cannula should be inserted medial or lateral to the vessels if they are visualized. If the vessels cannot be seen and it is necessary to position the cannula laterally, the device should be placed 3 to 4 cm lateral to the medial umbilical ligament or lateral to the lateral margin of the rectus abdominis muscle. If the incision is placed too far laterally, it will endanger the deep circumflex epigastric artery. The risk of injury can be minimized by placing a 22-gauge spinal needle through the skin at the desired location, in order to directly observe the entry through the laparoscope. This provides reassurance that a safe location is identified and allows visualization of the peritoneal needle hole, which provides a precise target for inserting the cannula. Even after a properly positioned incision, the abdominal wall vessels can be injured if a trocar slides medially during placement. Large-diameter devices are more likely to cause injury; therefore, the smallest cannulas necessary to perform the procedure should be used. Ancillary cannulas should not be placed too close together because this results in hindrance of the hand instruments, which compromises access and maneuverability. It is important to know that the outside diameter of a cannula is larger than the inside diameter, to allow for the thickness of the material used to create the port. In some instances, this can add two or more millimeters to the device diameter, and, therefore, increase the length of the required incision. Endoscopy During endoscopy, the image must be transferred through an optical system. Although direct optical viewing is feasible and often used for diagnostic purposes, virtually all operative laparoscopy is performed using video guidance. The light is generally transmitted from a cold light source via a fiberoptic cable to an attachment on the endoscope that passes the light to the distal end of the telescope via a peripherally arranged array of fiberoptic bundles. The image is obtained by a distally positioned lens and transmitted to the eyepiece via a series of rod shaped lenses. The eyepiece can be used to view the peritoneal contents directly or can serve as a point of attachment for a digital video camera. Another option is to position a digital chip on the end of the system, which then functions as a camera, obviating the need to have any lenses or fibers to transmit the image, a design that is colloquially called chip-on-a-stick. A laparoscope with an integrated straight channel, parallel to the optical axis, is called an operating laparoscope because the channel allows for the introduction of operating instruments. This offers an additional port for the insertion of instruments and the application of laser energy. Operative endoscopes are of relatively larger caliber than standard laparoscopes, may have smaller fields of view and may present increased risks associated with the use of monopolar electrosurgical instruments. Standard, viewing only laparoscopes permit better visualization at a given diameter. In general, the wider the diameter of the laparoscope, the brighter the image, resulting from either more light or wider lenses, which improve the viewing experience for the surgeon. Narrow-diameter laparoscopes generally allow reduced transfer of light both into and out of the peritoneal cavity; therefore, they require a more sensitive camera or a more powerful light source for adequate illumination. In the past, ideal illumination was provided by 10-mm diagnostic laparoscopes, but improvements in optics allowed the 5 mm diameter laparoscope to become the standard in many operating rooms (Fig. The viewing angle depicts the relationship of the visual field to the axis of the endoscope and typically ranges from 0 to 45 degrees to the horizontal. The 30-degree angle scope is invaluable in difficult situations, such as the performance of laparoscopic sacrocolpopexy, some myomectomies, and hysterectomy in the presence of large myomas. Imaging Visualization Systems the video camera is usually attached to the eyepiece of the endoscope where it captures the image and transmits it to the body of the camera located outside the operative field, where it is processed and sent to a monitor and, if desired, a recording device (Fig. Laparoscopes without an optical path were introduced, with the sensor located on the distal tip of the endoscope, a design that requires a remote camera location. The resolution capability of the monitor should be at least equal to that provided by the camera. The best available output is achieved from 250 to 300 watts, usually using xenon or metal halide bulbs. Most camera systems are integrated with the light source to vary light output automatically, depending on the amount of exposure required. Light guides or cables transmit light from the source to the endoscope via a bundle of densely packed optical fibers (fiberoptic). Fiberoptic cables lose function over time, and the fibers can break if they are mishandled. This tower comprises a monitor (A), a camera body or base unit (B) attached to a camera sensor; a light source (C) attached to a cable, which in turn will be connected with the endoscope; a still-image printer (D), and an insufflation machine (E). Other approaches are being explored that2 use mechanical lifting systems that allow room air into the peritoneal cavity. Carbon dioxide is injected into the peritoneal cavity under pressure by a machine called an insufflator. Most insufflators can be set to maintain a predetermined intra-abdominal pressure. High flow rates (9 to 20 L per minute) are especially useful for maintaining exposure when suction of smoke or fluid depletes the volume of intraperitoneal gas. Intraperitoneal retractors attached to a pneumatic or mechanical lifting system can be used to create an intraperitoneal space much like a tent (93). This gasless or isobaric technique may have some advantages over pneumoperitoneum, particularly in patients with cardiopulmonary disease. Airtight cannulas are not necessary, and instruments do not need to have a uniform, narrow, cylindrical shape. Consequently, some conventional instruments may be used directly through the incisions. Manipulation of Tissue and Fluid Fluid Management Fluid may be disseminated into the peritoneal cavity through wide-caliber arthroscopy or cystoscopy tubing using gravity pressure and an infusion cuff or a high-pressure mechanical pump. The pumps deliver fluid faster than the other techniques, and the highly pressurized stream of fluid may facilitate blunt dissection (hydro or aqua dissection). Small volumes of fluid can be removed with a syringe attached to a cannula; for large volumes, it is necessary to use suction generated by a machine or a wall source. The type of cannulas used for suction and irrigation depends on the irrigation fluid used and the fluid being removed. For ruptured ectopic gestations or other procedures in which there is a large amount of blood and clots, large-diameter cannulas (7 to 10 mm) are preferred. Cannulas with narrow tips are more effective in generating the high pressure needed for hydrodissection. If large volumes of fluid are required, isotonic fluids should be used to avoid fluid overload and electrolyte imbalance. If electrosurgery is to be performed, small volumes of a nonelectrolyte-containing solution such as glycine or sorbitol can be used for hemostasis and irrigation. Heparin (1, 000 to 5, 000 U/L) can be added to irrigating solution to prevent blood from clotting and facilitate fluid removal. Uterine Manipulators Uterine manipulation is an important component of the strategy to maximize visualization for most pelvic procedures, especially for myomectomy and hysterectomy. A properly designed uterine manipulator should have an intrauterine component, or obturator, and a method for attaching the device to the uterus. Articulation of the instrument permits acute anteversion or retroversion, both of which are extremely useful procedural maneuvers. If the uterus is large, longer and wider obturators can be used for more effective control. A hollow channel attached to a port allows intraoperative instillation of liquid dye to aid in the identification of the endometrial cavity (during myomectomy) or to demonstrate tubal patency. At the tip is a balloon inflated to maintain the device in the endometrial cavity. Next to the tip is a cervical collar that serves to facilitate identification of the vaginal fornices and cutting of the vagina in laparoscopic total hysterectomy. The blue truncated cone maintains a seal so that gas will not leak out when culdotomy is performed. Grasping Forceps the forceps used during laparoscopy should, to the extent possible, replicate those used in open surgery. Disposable instruments generally do not have the quality, strength, or precision of nondisposable forceps (Fig. Instruments with teeth (toothed forceps) are necessary to securely grasp the peritoneum or the edge of an ovary for the removal of an ovarian cyst. Instruments designed to be minimally traumatic, like Babcock clamps, are needed to retract the fallopian tube safely. Graspers should be insulated if unipolar radiofrequency instruments are being used to attain hemostasis. Other reusable tips (B) and (C) may be positioned in the same handle as is shown for (A). D: A 10-mm claw grasper, while (E) and (F) are 5 and 2-mm manipulating probes respectively. Cutting, Hemostasis, and Tissue Fixation Cutting can be achieved by mechanical means or by using laser, radiofrequency electrical, or ultrasonic energy. The methods for maintaining or securing hemostasis include sutures, clips, linear staplers, energy sources, and topical or injectable substances. Secure apposition or tissue fixation may be accomplished with sutures, clips, or staples. With appropriate training, a skilled surgeon can obtain good results with any combination of these techniques for cutting, hemostasis, and tissue fixation. Therefore, differences in results are likely to be caused by other factors, such as patient selection, extent of disease, and degree of surgical expertise. Because it is difficult to sharpen laparoscopic scissors, most surgeons prefer disposable instruments that can be used until dull and then discarded. The cost and large dimensions of the instruments limit their practical use to only a few highly selected situations, such as separation of the uterus from the ovary and fallopian tube during laparoscopic hysterectomy. Devices that coagulate tissue and mechanically transect it are designed to be narrow enough to be practical and effective enough to become the dominant devices for laparoscopic cutting, when concomitant sealing of vessels is a requirement. Laser and electrical sources of energy manifest their effect by conversion of electromagnetic energy (Fig. This expansion ruptures the already damaged cell membrane, resulting in cellular and tissue vaporization into a cloud of steam, ions, and protein particles. If the instrument used to focus this energy is moved in a linear fashion, tissue transection or cutting will result. Less focused radiofrequency energy (moderate current density) elevates intracellular temperature, causing desiccation, rupture of hydrogen bonds, and tissue coagulation, but vaporization does not occur. Monopolar electrosurgical instruments that are narrow or pointed are capable of generating the high-power densities necessary to vaporize or cut tissue. Continuous or modulated and relatively low voltage outputs tend to be the most effective. For optimal results, the instrument should be used in a noncontact fashion, following (not leading) the energy through the tissue. Specially designed bipolar cutting probes that contain both the active and dispersive electrode are available. The active electrode is shaped as a needle, or even a blade, while the other larger-surface-area electrodes are designed to be dispersive (Fig. Laparoscopic scissors are generally of unipolar design and are intended to cut mechanically; energy may be applied simultaneously for desiccation and hemostasis when cutting tissue that contains small blood vessels (Fig. They may be connected to an electrosurgical generator to act as a unipolar electrode. These limitations and their additional expense constrict the value of these lasers. Ultrasonic cutting is accomplished mechanically using a blade that oscillates back and forth in a linear fashion (Fig. The oscillation is achieved using an element located in a handle that vibrates the blade, hook, or one arm of the clamp 55, 000 times per second (55 kHz). The distance of the oscillation can be varied and determines the efficiency of the cutting process. The tip of the device cuts mechanically, but there is a degree of collateral thermal tissue coagulation injury that can be used for hemostasis. In low-density tissue, the process of mechanical cutting is augmented by the process of cavitation, in which reduction of local atmospheric pressure allows vaporization of intracellular water at body temperature. Hemostasis Because of the visual, tactile, and mechanical limitations of laparoscopy, prevention of bleeding is important for efficient, effective, and safe procedures. Radiofrequency electricity is the least expensive and most versatile method for achieving hemostasis during laparoscopy and can be applied with either monopolar or bipolar instruments. With adequate power, typically 20 to 30 watts (depending, in part, on the surface area of the electrodes), tissue will be heated, desiccated, and coagulated. This allows the opposing walls of the vessel to bond, forming a strong tissue seal in a process called coaptive coagulation. Bipolar devices can be fitted with a serial ammeter that measures the current flowing through the system. When the tissue between the blades of the forceps is completely desiccated, the device is no longer able to conduct electricity, which can trigger a visual or auditory cue for the surgeon. Alternatively, the generator can be designed to stop automatically when current is no longer being conducted by the tissue between the blades of the forceps. The surgeon can reduce lateral thermal spread of radiofrequency energy by manually pulsing delivery or by simultaneously running irrigation fluid over the pedicle.
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