Gastroenterological Endoscopy. Группа авторов

was found useful for the removal of scarred, nonlifting, residual polyp tissue (so-called hot biopsy avulsion) (Video 7.4) without adverse events in a small study of 20 patients.¹⁷

      If utilized, the hot biopsy forceps technique should be restricted to the removal of polyps < 5 mm in size, with grasping and tenting of the polyp away from the bowel wall to limit thermal injury to the submucosa. The use of a fractionated cutting current or low-voltage soft coagulation current waveform set at low power (10–15 W) is suggested, with pedal activation of 1 to 2 seconds.

      7.4.3 Sphincterotomy

      Factors that affect the performance of sphincterotomy include the selected waveform, power setting, length of wire in contact with tissue, and force of the sphincterotome applied onto tissue. From an electrosurgical standpoint, only “Coag”-type waveforms with duty cycles lower than 37% have been associated with a significant increase in postsphincterotomy pancreatitis due to wider thermal spread, local edema, and restricted pancreatic outflow.³ Thus, endoscopists who perform sphincterotomy generally select waveforms that promote more cutting and less coagulation, such as low-voltage, 100% duty cycle, “Pure Cut” outputs or modulated waveforms with duty cycles > 40%. The power settings also tend to be higher (30–60 W) relative to polypectomy settings since cutting efficiency increases with rising power. Proprietary microprocessor-controlled outputs, such as “ENDO CUT I” or “Pulse Cut,” are increasingly being used for sphincterotomy. The use of such outputs that can “pulse” or “fractionate” the cut is useful in reducing the risk of an uncontrolled zipper cut, particularly in the hands of less experienced endoscopists.^3,6

      A meta-analysis of four prospective randomized trials (804 patients) comparing “Pure Cut” to “mixed” current, which included blended current and “ENDO CUT,” showed a higher rate of minor postbiliary sphincterotomy bleeding in the “Pure Cut” group, but no significant differences in the rates of pancreatitis or major bleeding between the two groups.¹⁸

      7.4.4 Hemostasis

      Contact Bipolar

      Bipolar applications in gastrointestinal endoscopy are mostly limited to the use of bipolar coagulation probes for hemostasis since the development of bipolar accessories for polypectomy and sphincterotomy is technically complex and expensive. Bipolar outputs designed for use with bipolar probes combine a low-voltage, continuous waveform with a narrow power-to-impedance curve. A power setting of 15 to 20 W is generally sufficient for endoscopic hemostasis (

Table 7.4). For larger caliber vessels, such as those found in peptic ulcers and Dieulafoy’s lesions, the bipolar probe should be applied for a longer time interval with firm contact pressure to promote deeper coagulation (Video 7.5). Shorter contact duration with light to moderate pressure is recommended in the small intestine and colon (Video 7.6).

      Contact Monopolar

      Dedicated monopolar hemostatic forceps (e.g., Coagrasper) and probes (e.g., TouchSoft Coagulator, Genii Inc., St. Paul, MN) for endoscopic use are available, which are particularly suitable for hemostasis of actively bleeding as well as nonbleeding vessels during procedures such as endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD). Low-voltage (< 200 Vp), continuous waveforms (e.g., “Soft Coag” or “TouchSoft”) are utilized with these devices to optimize coagulation of blood vessels, with manufacturer’s suggested power settings ranging from 50 W (colon) to 80 W (stomach). The application of brief (1–2 s) pulses of coagulation current, in addition to vascular coaptation by the closed jaws of the Coagrasper forceps, results in effective sealing of the blood vessel (Video 7.7). The Coagrasper device may also be suitable for other nonvariceal bleeding lesions, although care regarding its use for the treatment of a visible vessel in an ulcer is warranted, since grasping and tenting the vessel from an indurated base may result in vascular tearing and bleeding.

      Argon-Assisted Coagulation

      Argon-assisted or argon plasma coagulation (APC) is a noncontact monopolar method used primarily for coagulation of superficial vascular lesions, such as gastric antral vascular ectasia (Video 7.8) and angiodysplasias, and for tissue ablation, such as residual Barrett’s epithelium and polyp tissue (Video 7.9). APC works through delivery of RF energy to the target tissue via electrically conductive ionized argon gas (plasma). Nonionized gas outside of the argon beam does not conduct energy to the tissue.

      Some APC-enabled ESUs (e.g., ERBE VIO/APC2 and ConMed Beamer Mate) are equipped with amplified power profiles such that lower power settings produce similar tissue effects relative to nonamplified APC generators.⁷ A good starting point is to select the manufacturer’s recommended power setting in the lower range for a particular indication and increase power output until the desired tissue effect is achieved.

      In general, power settings of 40 to 60 W are adequate for hemostasis and superficial tissue ablation, with the argon flow rate maintained at 1 L/minute. For high-power amplified ESUs, the settings are typically about half that of nonamplified APC generators. Ideally, the APC probe should be maintained at a distance of 1 to 2 mm from the target site, as ionization will not begin if the probe is too far from tissue. If the ideal distance cannot be maintained and the probe is further away from tissue, it is best to augment the power setting rather than the argon flow rate since increasing the latter only serves to further dilute the ionized particles in the stream. Inadvertent probe–tissue contact may result in localized pneumatosis from dissection of tissue layers by argon gas, an often benign event. APC-induced perforations, however, have occurred and likely correlate with tissue contact with the probe tip, power setting, and duration of application.

      7.4.5 Miscellaneous

      Electrosurgery figures prominently in various other procedures, including EMR, ESD, peroral endoscopic myotomy (POEM), and radiofrequency ablation (RFA) of Barrett’s esophagus (BE). Dedicated generators and RFA catheters (BARRX, Covidien, Sunnyvale, CA) are commercially available for BE,¹⁹ as well as a variety of electrosurgical knives for ESD²⁰ and POEM.²¹ For the latter, the selected current waveforms and power settings are influenced by the type of knives used for incision and dissection, lesion characteristics and location, and operator preference. A review of these techniques and available electrosurgical accessories is beyond the scope of this chapter.

      7.5 Electrosurgical Hazards and Safety

      7.5.1 Unintended Burn Injury

      Older ground-referenced ESUs are outdated, since current seeking the path of least resistance could travel through electrically conductive grounded materials, causing thermal injury at alternate sites. Modern ESUs have isolated outputs such that the system is disabled if there is any break in the return circuit or when excessive leakage is detected, thus greatly minimizing the risk of alternate site thermal injury through other ground paths. Return electrode contact quality monitoring (RECQM) is a standard feature in most ESUs and, combined with dual-foil dispersive electrodes (“split” pads), RECQM-equipped units will not activate if a hazardous concentration of current is detected at the interface between the electrosurgical pad and the patient. These units have virtually eliminated the incidence of a skin burn at the pad site. Proper placement of the electrosurgical pad is nevertheless important. Flank or upper thigh placement is common in gastrointestinal endoscopy, and high-resistance areas, such as bony prominences, hair, scars, and prosthetic joints, should be avoided. The avoidance of the term “grounding pad” conveys