Of greater concern is bowel gas, which frequently contains a mixture of methane and hydrogen which, when mixed with oxygen, even in low concentrations, are highly explosive.
This is a real hazard when operating around the large bowel, or when performing anorectal surgery. Nitrous oxide supports combustion, as well as pure oxygen. Many gynecologists use nitrous oxide as a laparoscopic distention medium to avoid the peritoneal irritation caused by carbon dioxide. If electrosurgery is to be used during a laparoscopic operation, the use of nitrous oxide to distend the abdomen should be avoided.
Although most modern cardiac pacemakers are resistant to interference by extraneous electromagnetic signals, several incidences of asystole and cardiac arrest have been reported when electrosurgery is used in patients with pacemakers. In these units, the electrosurgical signal may block the pacer's inhibition amplifier allowing an R-on-T phenomenon to occur, leading to ventricular fibrillation. Aside from the special case of the cardiac pacemaker patient, with the use of radio frequency currents, cardiac arrhythmia due to discharge from an ESU should be an almost nonexistent event.
Until the recent upsurge in interest in operative laparoscopy, reports of burns of the bowel during laparoscopic sterilization had rendered the use of unipolar techniques in laparoscopy almost untenable.
Inthe Complications Committee of the Association of Gynecologic Laparoscopists 32 reported burns to skin or bowel occurring at a rate of 2. In the same year, Thompson and Wheeless 33 reported 10 burn injuries of the intestines occurring in a cohort of patients undergoing unipolar laparoscopic sterilization. Four of these injuries were noted at the time of surgery and treated with observation alone due to the small, superficial nature of the injury. This group experienced uneventful recovery.
A fifth patient with a small burn had the site oversewn, although she could have been treated by observation. In five additional cases, the injury was unrecognized and resulted in delayed perforation.
Most of the burns occurred on the terminal ileum. As we shall see presently, it is important that burns occurred with both one- and two-puncture techniques. InLoffer and Pent 34 reviewed the 71 electrical complications of laparoscopy that had been reported at that time. Twenty-five cases involved burn injuries to the abdominal wall, and 44 cases, burns of the bowel. Of these 44 cases, the ileum was involved in 39 and the colon in five. Schwimmer 35 reported two superficial intestinal burns occurring in sterilization procedures performed with a two-puncture Break It Down - Various - Groovetechnology V1.2 - Electrocuted Presents Sexmachinemusic (CD), using unipolar current.
InMaudsley and Qizilbash 36 reported an additional four small bowel injuries among consecutive procedures, all performed with a two-puncture technique. The mechanism of these injuries is controversial.
Mechanisms involving current arcing to the bowel at distant sites, arcing from tube to bowel, and creation of a capacitor have been proposed. Each of these mechanisms appears equally improbable. It requires about 30, volts to cause dielectric breakdown of a 2. Theoretically and in practice, a capacitor can be inadvertently constructed using unipolar current and a single puncture technique.
This would allow several thousands of volts of electrical energy to accumulate in the laparoscope barrel—more than enough to allow arc formation between laparoscope and nearby bowel. Although this mechanism may account for some of the reported injuries, it is unlikely to account for the majority because most cases occurred with a double puncture technique.
It is possible that faulty insulation on the unipolar electrode, passed either through an insulated or a metal sheath may account for some of the injuries. Perhaps the most likely mechanism was proposed by Engle and Harris 37 who studied the electrodynamics of tubal coagulation.
It was found that, initially, with the electrode in good contact with the intact tube, as tissue heating began, the resistance dropped, and no sparking occurred. As coagulation proceeded and the tissue fluids boiled away, the resistance increased. When resistance became so high that tissue contact was poor, sparking occurred from the electrode to the nearest moist tissue. This effect was related to the peak voltage.
It is recommended that tubal coagulation be carried out with the lowest effective power and a cutting current to limit peak voltage. The bipolar electrosurgical forceps have been adapted to gynecologic use as a highly successful remedy to the problem of inadvertent bowel burns.
One additional potential cause of inadvertent electrical injury deserves discussion. When unipolar current is applied to a structure on a stalk, the current tends to concentrate at the base of the stalk causing coagulation of the blood supply to the structure. While this may be applied to advantage in treatment of condylomas and papillomas, there is a potential for disastrous consequences if unipolar coagulation is used to control bleeding during circumcision.
Electrosurgical generators are devices that produce currents of various waveforms suitable for surgical applications. The earliest electrosurgical generators used a spark gap system to produce a highly damped, high frequency current. Shortly thereafter, valve vacuum tube generators, which had the capability of producing smooth, sine wave currents, suitable for cutting of tissue, were introduced.
The tube generator has since been replaced by the modern, solid state generator. The spark gap and the solid state generators are the two types in modern usage. Solid state generators produce the coagulation waveform by using transistors and solid state components to produce high voltage bursts of current. Spark gap generators produce damped, high voltage bursts of current by discharge of air-spaced plates.
Spark gap systems are incapable of producing undamped, cutting current. Even though solid state generators are capable of producing peak voltages in excess of 10, volts, unlike spark gap units, they usually cannot maintain the same level of power output at high impedance loads, as when working in a fluid environment.
Cutting and coagulating currents are produced from two independent generators contained within the ESU. Contrary to what is popularly understood, blended currents from solid state electrosurgical systems are produced by the cutting current generator, and consist of a simple, damped waveform, much less drastic in modulation than the coagulation current.
In either case, the desired effect is to enable the standard electrode to cleanly divide tissue, while causing sufficient thermal effect to produce hemostasis. Frequency Several considerations place limits upon the frequencies at which electrosurgical generators can operate.
Frequencies in excess of 10, Hz are necessary to produce the diathermic effect without neuromuscular stimulation. Frequencies below this threshold cause undesirable depolarization of susceptible tissues heart, muscle, and nervous tissueleading to tonic and clonic muscle contractions with rhabdomyolysis and cardiac dysrythmias.
Similarly, the use of excessively high frequencies can lead to surgical complications. The primary concern in the design of electrosurgical equipment is the containment of the current pathway within its intended circuit. Travel of the current via alternate, undesired pathways can produce electrosurgical burns.
Such an alternate pathway may occur via a pathway of less capacitive resistance to ground. Capacitance, technically defined as leakage or loss of current through an insulator, occurs with much greater efficiency as the frequency of the current increases, allowing shunting of current to occur short circuit. Capacitive coupling can occur if other electrical circuits, such as monitoring equipment, are in contact with the patient, causing alternate site burns.
It is for these reasons that almost all contemporary electrosurgery generators use a frequency of betweenHz and 2. Grounding In electrosurgery, the Break It Down - Various - Groovetechnology V1.2 - Electrocuted Presents Sexmachinemusic (CD) grounding refers to the relationship between the dipole circuit active electrode—patient—return electrode and earth ground.
Three relationships between the dipole circuit and earth ground are possible: direct grounding, isolated grounding circuitry, and capacitive grounding circuitry. The return portion of the circuit is connected directly to earth ground. Direct grounding is considered unsafe and is not used in modern ESUs because it invites numerous alternate pathway possibilities with the potential for unintended burns. The output current is floating free of ground. This means that the patient ground is referenced to the ESU rather than earth ground.
The machine is, in turn, referenced to earth ground via special circuitry that avoids alternate pathways. If the patient should inadvertently be placed in contact with another grounded object, this circuit will detect the loss of current and disable the ESU. It should be noted that if an ESU using isolated grounding circuitry is activated while the active electrode is not in contact with the patient, it is possible for alternate site burns to occur if the patient is in contact with a direct path to ground i.
The return circuit is referenced to earth ground via a capacitive circuit, which reduces some of the hazards of electrosurgery by acting as an electrical filter, permitting only currents of specific frequencies to flow through the return plate attached to the patient. Each grounding scheme has inherent advantages and disadvantages. In response to the need of many surgical disciplines for a very effective spray coagulation current, many manufacturers of ESUs have increased the performance of their solid state generators to deliver 10, or more volts.
Since high voltages have the ability to seek and find earth ground effectively, it is difficult to contain these higher voltages with an isolated circuit. Because direct grounding would only compound this problem, when high voltages are used, capacitive grounding becomes the method of choice. Most generators producing lesser voltages use isolated circuitry because this grounding scheme reduces alternate pathway possibilities and is generally considered to be the safest.
Monitoring of the Return Electrode Electrosurgical generators built prior to the late s did not incorporate any type of monitoring device to ensure proper connection of the return electrode, either to the patient or the ESU. Reports of burn injuries caused by a breach of the return electrode pathway led manufacturers of electrosurgical equipment to develop a monitor circuit, which incorporated a Break It Down - Various - Groovetechnology V1.2 - Electrocuted Presents Sexmachinemusic (CD) conductor patient cable, rather than a simple single conductor cable.
A low voltage current is introduced into the circuit and travels through one conductor of the patient cable, through the patient plate, and back to the unit via the second conductor of the cable.
If this low voltage current is interrupted for any reason, an alarm sounds and the unit's output is disabled. This should be considered the minimum requirement from a safety standpoint for any electrosurgical generator. This monitoring system does have one limitation: it cannot detect proper adherence of the return electrode to the patient. It only assures that the patient cable is connected to the generator.
The return electrode monitor REM system was introduced by ValleyLab in the early s, and offers one further level of safety in preventing alternate site burn injuries by ensuring that the return electrode is properly attached to the patient. With REM monitoring, a special return electrode with two separate, isolated areas is used. A low voltage current is introduced into one of the conductive areas of the pad. If the pad is evenly applied to the patient's skin, the current is transmitted to the second conductive area, and back to the ESU, completing the circuit.
The REM circuit is calibrated to detect a range of impedance, which would be expected between one side of the return electrode pad and the other with the patient's skin as the dielectric.
Impedances outside this precalibrated range will engage the REM alarm and disable the unit's output. This circuit is not impossible to defeat, as surfaces such as the Break It Down - Various - Groovetechnology V1.2 - Electrocuted Presents Sexmachinemusic (CD) floor of the operating room may provide an impedance within the monitor's range.
It must, therefore, be stressed that there is still no substitute for carefully and properly applying the return electrode to the patient. The two mechanisms by which patient injury is most likely to occur are the use of excessively high peak voltages and improper patient grounding. To avoid injury, the surgeon should personally ensure that the patient is positioned in such a manner that there is no contact with metal or other conductive objects that may potentially be grounded, and that the return electrode is properly applied and connected to the ESU.
The lowest effective settings on the ESU should be used to limit peak voltages and, for the same reason, a cutting rather than a coagulating waveform should be employed where possible. If excessively high power settings are needed to achieve the desired tissue effect, a faulty ground should be suspected, and the use of the ESU stopped until safe function has been assured.
J Urol 86 3 : Comparison of induction heating and radiofrequency electrocoagulation. J Neurosurg Radiology 2: McLean AJ: Characteristics of adequate electrosurgical current. Am J Surg 18 3 : Pearce JA: Electrosurgery. New York, John Wiley and Sons, Oral Surg 29 5 : J Prosthet Dent 42 4 : Luciano AA, Randolph J, Whitman P et al: A comparison of thermal injury, healing patterns, and postoperative adhesion formation following CO 2 laser and electromicrosurgery.
Fertil Steril 48 6 : Greenwood J: Two point coagulation. A new principle and instrument for applying coagulation current in neurosurgery. Am J Surg Urol Res 99, Neurosurgery 13 2 : Ellis JD: The rate of healing of electrosurgical wounds as expressed by tensil strength. JAMA 16, Am Surg 56 10 : Surg Gynecol Obstet Break It Down - Various - Groovetechnology V1.2 - Electrocuted Presents Sexmachinemusic (CD) Prosthet Dent 33 3 : Am J Obstet Gynecol 3 : Carbon dioxide laser and electromicrosurgery.
Find Free WordPress Themes and plugins. Did you find apk for android? You can find new Free Android Games and apps. In the electroplating process an external voltage is applied across a pair of electrodes, causing: A. In the electroplating process the electrode connected to the positive polarity of the supply is called the anode and the electrode connected to the negative is: A.
Primary cells are electrochemical devices that convert chemical energy into: A. Secondary cell chemistries permit the cell to be recharged by: A. Look at the following figure: The diagram shows a simple voltaic cell consisting of two electrodes, one of copper and the other of zinc, immersed in a solution of dilute hydrochloric acid. In this cell the copper electrode is: A.
This simple cell is not very practical, because the copper electrode becomes covered with hydrogen gas, preventing hydrogen ions from taking further electrons from the surface. This effect is known as: A. To reduce the local action in a simple cell it is necessary to: A. Two dissimilar metals in an electrolyte form a primary cell. The voltage across their terminals depends on the: A. Given the following standard reduction potentials: What is the standard electromotive force of the following reaction?
Consider the following data: The anode of a certain galvanic cell is composed of copper. O 2— ions III. Electrons A. I only B. II only C. I and III only D. II and III only 5.
Equilibrium constant B. Reaction quotient C. Temperature of the system D. Half-reactions of the cells 6. NaCl B. MgSO 3 D. Current III. I and II only D. II and III only 8. Which Break It Down - Various - Groovetechnology V1.2 - Electrocuted Presents Sexmachinemusic (CD) the following can alter the emf of an electrochemical cell?
The mass of the electrodes B.
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