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Abstract
The argon plasma coagulator is a device used for noncontact thermal coagulation of tissue. The device was first used in open and laparoscopic surgical procedures and in 1991 was adapted for use in endoscopy. Since then, argon plasma coagulation has expanded its clinical applications in the treatment of various gastrointestinal conditions. The endoscopy nurse plays an important role in the care of patients before, during, and after argon plasma coagulation treatment. This article reviews the principles and components of the argon plasma coagulator, and provides a summary of the various clinical applications, patient safety practices, and potential complications of argon plasma coagulation therapy.
The argon plasma coagulator is a device used for noncontact thermal coagulation of tissue. This technology was first introduced and utilized in surgical and laparoscopic procedures. In 1991, argon plasma coagulation (APC) was adapted for use in flexible endoscopy (Ginsberg et al., 2002). Endoscopic applications of APC continue to expand in the management of various gastrointestinal (GI) bleeding conditions as well as in procedures in which ablation of tissue abnormalities is necessary (Vargo, 2004).
The Argon Plasma Coagulator
Components of the argon plasma coagulator include an argon-compatible, high-frequency monopolar electrosurgical generator, APC unit, argon gas source, foot activation switch, flexible delivery catheters (probes), grounding pads, and accessories (filter membrane, connector hose). The synchronization of the electrical current and argon gas occurs when the footswitch is depressed.
In endoscopy, disposable APC probes are designed to operate through the working channel of flexible endoscopes (Figure 1). These probes are manufactured in two diameters (7 Fr. or 10 Fr.) with a variety of nozzle orientations (Figure 2A–2C). The probes are made of Teflon and contain a recessed tungsten electrode at the distal tip. The electrical current and argon gas travel through the flexible probe and become ionized at the point of contact with the electrode. It is this ionized argon plasma that allows electrical current to flow between the probe and tissue (R. Reed, personal communication, February 2, 2006) (Figure 3). The application of this energy causes coagulation of tissue.
 | FIGURE 1. The argon plasma coagulator probe is designed to operate through the working channel of a flexible endoscope (with permission, ERBE-USA, Marietta, GA). |
 | FIGURE 2. ( |
 | FIGURE 3. Schematic of an argon plasma coagulator probe (with permission, ERBE-USA, Marietta GA). |
The depth of tissue injury is a function of the generator's power setting, flow rate of the argon gas, distance from the target tissue, and the duration of application. The approximate depth ranges from 1 to 3 mm (Healthstream®, 2005) (Figure 4). Power settings and argon gas flow rates vary depending on the indication for therapy. In general, lower power settings and lower argon gas flow is used in hemostasis of vascular lesions, whereas higher power settings and higher argon gas flow is utilized in ablative applications (Ginsberg et al., 2002).
 | FIGURE 4. Tissue effects of argon plasma coagulation therapy (with permission, ERBE-USA, Marietta, GA). |
Indications
Indications for APC are categorized into hemostasis and ablative applications (Figure 5).
 | FIGURE 5. Argon plasma coagulation: endoscopic applications (dotted lines denote investigational applications). |
Vascular lesions of the GI tract are increasingly recognized as a source of bleeding (Greenwald & Brandt, 2002). Argon plasma coagulation has been successful in treating a variety of vascular lesions.
This syndrome involves the gastric antrum and is a vascular lesion of unknown etiology. The disorder is characterized by erythematous thickened antral folds that radiate out from the pylorus, resembling stripes on a watermelon (Greenwald & Brandt, 2002). Studies have shown that APC is a safe and effective nonsurgical treatment for symptomatic bleeding from gastric antral vascular ectasia syndrome. Treatment with power settings ranging between 20 and 50 W, argon gas flow ranging between 1 and 2 L/minute, and a median number of two treatment sessions resulted in no further need for blood transfusions. No treatment-related complications were reported (Kwan et al., 2006; Yusoff, Brennan, Ormonde, & Laurence, 2002). The advantage of APC over contact cautery with bipolar probes is the ability to “paint” the lesions without mucosal contact, enabling large surface area treatments in a rapid fashion.
Vascular ectasias are a frequent cause of acute and chronic (occult) GI bleeding. Olmos, Marcolongo, Pogorelsky, Varela, and Davolos (2004) found APC to be an effective treatment for angiodysplasia with the majority of patients responding to one treatment session. Different power settings were utilized, depending upon the anatomical location of the lesions. Gastric, duodenal, and left colonic lesions were treated at 60 W, whereas small intestine, right colon, and cecum were treated with 40 W, given the thin bowel wall in the latter locations. Argon gas flow ranged from 2 to 2.5 L/minute. There was no further GI bleeding reported in 50 of the 60 (83%) patients at a median follow-up of 18 months. Out of a total of 71 endoscopic APC procedures, two (2.8%) procedure-related complications (fever and pneumoperitoneum) were reported and treated conservatively.
Radiation proctopathy is a complication of radiation treatments for malignancies involving the pelvis. One of the late complications of radiation proctopathy is rectal bleeding. This bleeding can be severe enough to require urgent hospital admission with blood transfusions, or in mild or chronic situations, radiation proctopathy can present as transfusion-dependent iron deficiency anemia (Silva, Correia, Dias, Viana, & Viana, 1999). Villavicencio, Rex, and Rahmani (2002) concluded that rectal bleeding secondary to radiation proctitis was successfully controlled with APC. The mean number of treatment sessions per patient was 1.7. Argon gas flow ranged from 1.2 to 2 L/minute with a power setting ranging between 45 and 50 W. Short-term side effects of rectal pain, tenesmus, or abdominal distention occurred in 3 out of 21 (14%) patients. Long-term side effects of rectal pain, tenesmus, and diarrhea occurred in 4 out of 21 (19%) patients.
The use of APC in treating bleeding peptic ulcer disease is under investigation. Studies investigating the use of contact methods of hemostasis (heater probe, bipolar electrocoagulation) are well established. Chau et al. (2003) suggested that APC was as safe and effective as heater probe (thermal contact) when used in conjunction with epinephrine injection in those with high-risk bleeding peptic ulcer disease. More clinical trials are warranted to evaluate the effectiveness of APC in the treatment of bleeding peptic ulcers (Sung, 2006).
The use of APC as a supplemental treatment in the eradication and prevention of esophageal variceal recurrence and bleeding is under investigation. Cipolletta et al. (2002) initiated APC therapy within 30 days of esophageal variceal ligation for acute bleeding. Mean power output was 60 W with argon gas flow rate of 1.5–2.0 L/minute. The median number of treatment sessions per patient was 2.1. There were no episodes of recurrent varices and bleeding in those patients treated with APC. Six of the 14 (48%) patients in the non-APC treated group had recurrent varices. One (7.2%) patient in the non-APC treated group experienced recurrent bleeding. Of the 16 patients in the APC group, 13 experienced transient fever and 8 experienced dysphagia. Both symptoms subsided spontaneously within 24 hours. This high incidence of early complication is likely due to the high power setting used in this trial.
Endoscopic removal of adenomatous colonic polyps can reduce the incidence of colorectal cancer by 76% to 90% (Conio et al., 2004). Large sessile polyps represent a clinical challenge with respect to complete endoscopic removal. Residual viable adenomatous tissue carries the risk of progression to malignancy. Thermal ablation methods have been utilized to eradicate visible and microscopic residual adenomatous tissue. Thermal methods such as hot biopsy forceps or laser carry the risk of perforation, secondary to the unpredictable depth of tissue injury. Argon plasma coagulation is more suited for the treatment of residual adenoma as the electrosurgical energy is delivered at a predictable depth (Brooker et al., 2002).
Brooker et al. (2002) report APC to be an effective and safe adjunct to piecemeal resection of large sessile colon polyps. In this study, argon gas flow was set at 2 L/minute with power output ranging between 45 and 50 W for treatment in the right colon whereas left colon sites were treated with 65 W. The use of APC prevented recurrence in 54% of the patients, even in those cases where complete snare resection was not possible. In this study, there were no complications attributed to the use of APC. Because recurrence is sometimes seen after APC, patients require careful long-term surveillance. The current practice for this group was to repeat examinations in 1 year, followed by standard 3-year surveillance.
Barrett's esophagus is histologically defined as the replacement of normal squamous mucosa with metaplastic columnar lined epithelium in the distal esophagus (Eisen, 2003). It is considered as a premalignant lesion with the potential for progression to high-grade dysplasia (HGD) and adenocarcinoma (Healthstream®, 2005). The goal of ablative therapy is to destroy the metaplastic epithelium. In an anacid environment, new normal squamous mucosa may generate after ablative therapy (Eisen).
The use of APC in the treatment of HGD and early stage cancer is currently under investigation. Most studies have reported on the outcomes of APC in the treatment of nondysplastic Barrett's esophagus (Eisen, 2003). Van Laethem, Jagodzinski, Peny, Cremer, and Devière (2001) were the first to report on the effects of APC in the treatment of HGD and adenocarcinoma in situ. Patients were treated with 90 W of energy. Eight of 10 achieved complete eradication of HGD after a mean of 3.3 treatment sessions. These 8 patients did not show any evidence of local recurrence during a median follow-up period of 24 months. One patient had persistent HGD 30 months after initial therapy. One patient progressed to invasive adenocarcinoma after treatment with APC and photodynamic therapy. One patient developed an esophageal stricture after two treatment sessions, successfully treated with balloon dilation. There were no procedure-related deaths. In summary, APC may be an alternative treatment for those individuals who are deemed nonsurgical candidates as well as an adjunctive treatment following endoscopic mucosal resection (Peters et al., 2005).
Argon plasma coagulation has been utilized for the treatment of early gastric cancer in those patients who are not candidates for endoscopic mucosal resection or open surgery (Kitamura et al., 2006). Kitamura et al. followed 40 patients in an effort to establish a standard procedure for APC treatment of early gastric cancers. In this study, patients were treated with an energy setting of 60 W with an argon gas flow of 2 L/minute. There was no evidence of residual tumor or recurrence in patients with intramucosal lesions after one treatment session, and there was no evidence of recurrence in patients with submucosal invasion after two treatment sessions. These results suggest that early small superficial gastric cancers can be successfully treated in one session whereas larger (2 cm or greater) and deeper lesions are likely to require two sessions of APC treatment. Three of 40 (7.5%) patients experienced complications of submucosal emphysema, bleeding, and perforation, respectively, which resulted in the death of 1 patient. Other ablative applications for APC include palliative treatment for malignant GI tract obstruction, treatment of tissue ingrowth into metallic stents, and myotomy for Zenker's diverticulum (Ginsberg et al., 2002).
Complications
Complication rates of APC reported in various publications are low, especially when compared with other thermal methods of treatment, such as the Neodymium Doped Yttrium Aluminum Garnet laser (Prost, Poncet, Scoazec, & Saurin, 2004). The low complication rate is thought to be secondary to the limited depth of coagulation (1 to 3 mm) with APC. Perforation, although rare, is the most severe complication.
Prost et al. (2004) reported two perforations in unusual sites related to APC therapy. The first case involved the perforation of a blind ileal segment in a patient with a history of a colectomy for familial adenomatous polyposis. This patient was receiving APC treatment for residual polyps in the ileal segment (60 W/argon gas flow 1 L/minute). The second case involved treatment of angiodysplasias located in the fundus of the stomach with the same power and argon gas flow settings. This patient was on corticosteroids and carried a history of Osler-Weber-Rendu disease. There is a need for larger prospective studies to better define actual complication rates in relation to indications for treatment. Individual risk factors must also be considered prior to entertaining APC therapies.
Nursing Implications
The nurse plays a vital role in the care of the patient before, during, and after APC therapy. Upon arrival to the procedure area, a nursing assessment is performed. This assessment includes a review of systems, a summary of past medical and surgical histories, medication review, and documentation of allergies. Special attention should be given for the presence of a pacemaker or automated internal cardiac defibrillator (AICD). At this author's institution, the patient's cardiologist or a pacemaker manufacturer is consulted regarding safe use of monopolar electrosurgery. Automated internal cardiac defibrillators are deactivated by a qualified individual prior to the procedure.
The second area of attention is that of preparation for APC procedures involving the lower GI tract. The quality and type of preparation is documented. A full colonoscopy preparation is necessary in order to reduce the risk of explosion secondary to ignition of retained colonic hydrogen and methane gasses. Finally, the assessment process should include a visual inspection for the presence of jewelry. All jewelry, including pierced ornaments, should be removed to avoid the risk of electrical injury.
The nurse plays a valuable role in assisting with endoscopic APC therapies. Equipment and accessories are organized before the procedure is begun. This author finds it advantageous to “rehearse” the procedure with the physician. This ritual before the procedure ensures that all necessary equipment is in the procedure room and the nurse can better anticipate the needs of the physician during the procedure.
It is essential to maintain a safe electrosurgical environment for the patient during APC therapy. The APC unit should be plugged into a grounded electrical outlet. Avoid the use of extension cords. The disposable probes should be visually inspected for damage prior to test fire and subsequent use on the patient. The disposable grounding pad should be inspected to make sure the gel is moist. Prior to application, the patient's skin condition must be assessed. The grounding pad should not be placed over hairy surfaces, bony prominences, scar tissue, or tattoos, as the latter contains metallic dye. The grounding pad should maintain uniform body contact on an area of well-perfused muscle mass (Association of periOperative Registered Nurses [AORN], Recommended Practices Committee, 2005).
Patients should be clear of any electrical conductive objects. Final positioning should include placing padding between any metal and extremities (i.e., arms coming in contact with side rails). Padding should also be placed between any skin-to-skin contact sites (i.e., between legs for lateral positioning). For patients with pacemakers or an AICD, continuous cardiac monitoring is performed. In this patient population, the grounding pad should be placed as distal as possible to the cardiac device. The emergency cardiac arrest cart is kept in proximity to the procedure room with the defibrillator charged and pads ready for use.
Prior to performing APC therapy, the settings on the argon plasma coagulator are visually and verbally confirmed with the physician. During therapy, the patient's abdomen is frequently assessed for abdominal distention. At this author's facility, a double channel scope is preferentially used to allow for better decompression of the intestinal tract during the treatment of gastric and colonic lesions, as gas insufflation can lead to a considerable abdominal distention. During treatment, the APC probe is periodically cleansed of debris and inspected for evidence of kinking or damage. Immediately following the procedure, the APC unit is stored carefully. The disposable argon gas membrane filter is removed and discarded. The argon connector hose is removed and disinfected according to the manufacturer's recommendations.
Care after the procedure includes monitoring of vital signs and observation for complications immediately after the procedure. An AICD is reactivated immediately following the procedure. Continuous electrocardiogram monitoring is performed on patients with pacemakers or AICD until discharge. Upon discharge, written instructions are provided, with emphasis placed on observation for bleeding, abdominal pain, abdominal distention, fever, and chills. These instructions include an emergency telephone number for contacting the physician.
Summary
Argon plasma coagulation is an effective and safe technique in the endoscopic management of GI conditions involving hemostasis and ablative therapies. Several new applications of APC are currently under investigation (bleeding peptic ulcer, esophageal varices, and Barrett's esophagus) with preliminary studies reporting favorable treatment outcomes. The endoscopy nurses play an important role in the care of patients before, during, and after APC therapies.
Acknowledgment
The author thanks Kevin McGrath, MD, for his assistance in the preparation of this manuscript.
References
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