A randomized, controlled trial of transcutaneous carbon dioxide monitoring during ERCP.

BACKGROUND: Pulse oximetry, used to monitor oxygen saturation during endoscopy, does not directly measure hypoventilation. Study goals were to determine whether transcutaneous carbon dioxide (PtcCO(2)) monitoring during endoscopic retrograde cholangiopancreatography (ERCP) prevents severe hypoventilation and to assess the accuracy of clinical observation and pulse oximetry in detecting hypoventilation. METHODS: All patients received intensive clinical and electronic monitoring including pulse oximetry. Supplemental oxygen was administered for pulse oximetry < 90%. Patients were randomized to a treatment arm (group 1) where PtcCO(2) monitoring guided sedation or a control arm (group 2) where PtcCO(2) was recorded but unavailable for guiding sedation. RESULTS: Group 1 had significantly fewer episodes of severe carbon dioxide retention (rise in PtcCO(2) >/=40 mm Hg above baseline) than group 2 (0 of 199 versus 5 of 196, respectively, p = 0.03), as well a shorter mean duration of procedure discomfort (8.3% of procedure duration rated as "uncomfortable" versus 11.5%, p = 0.04). Correlations between clinical observation and objective measures of ventilation were poor: level of sedation versus PtcCO(2) (R = 0.3) or pulse oximetry (R = 0.06); slowest respiratory rate versus PtcCO(2) (R = 0.4) or pulse oximetry (R = -0.4). PtcCO(2) rises of greater than 20 mm Hg occurred without oxygen desaturation in 10.7% of patients receiving supplemental oxygen. CONCLUSIONS: Carbon dioxide retention during ERCP is not reliably detected by clinical observation or by pulse oximetry in patients receiving supplemental oxygen. The addition of PtcCO(2) monitoring prevents severe carbon dioxide retention more effectively than intensive clinical monitoring and pulse oximetry alone. The clinical relevancy of this observation needs to be determined in an appropriately designed outcome study.

Silicone-covered Wallstent prototypes for palliation of malignant esophageal obstruction and digestive-respiratory fistulas.

BACKGROUND: Endoscopic palliation of malignant esophageal obstruction with uncovered self-expanding metal stents has been shown to have fewer complications than with conventional plastic stents. The addition of a membrane might prevent tumor ingrowth and allow treatment of digestive-respiratory fistulas. We report the clinical experience with a prototype silicone membrane-covered self-expanding metal stent. METHODS: Twenty-three silicone membrane-covered Wallstent prototypes were used in 21 patients with dysphagia due to inoperable malignant tumors involving the esophagus and cardia. RESULTS: Stent implantation was technically successful in all patients. There were no procedure-related perforations or deaths. The prototype stent was successful in sealing seven of the eight (87.5%) digestive-respiratory fistulas. As a group, the mean dysphagia grade improved significantly after stent placement (4.8 +/- 0.9 vs 3.4 +/- 1.6, p < 0.0005). However, 9 of 21 (42.9%) patients experienced no improvement in their dysphagia. Complications occurred in 13 of 21 (61.9%) patients. Tumor ingrowth was not observed in any patient. CONCLUSIONS: The prototype covered self-expanding metal stent was effective in sealing digestive-respiratory fistulas and provided palliation of dysphagia in slightly more than one half of the patients studied. A great deal has been learned from the preliminary experience, which has led to design modifications. The utility of the commercially available device should be evaluated in further prospective clinical trials.

A randomized blinded comparison of omeprazole and ranitidine in the treatment of chronic esophageal stricture secondary to acid peptic esophagitis.

BACKGROUND: Esophageal strictures due to gastroesophageal reflux disease are often resistant to medical therapy and require repeated dilation procedures. Our aim was to compare the efficacy of therapy with omeprazole (20 mg/day) to ranitidine (150 mg twice daily) in the treatment of chronic esophageal strictures. METHODS: Thirty-three patients with chronic esophageal stricture disease (mean length of prior treatment, 50.9 months) were entered into a randomized blinded trial. The majority (88%) of the patients had received multiple prior esophageal dilations (mean, 7.9 per patient). Endoscopy and barium esophagograms were performed initially and at the end of 10 months. Symptoms were considered every 2 months and dilations performed as needed. The patient groups were equivalent. RESULTS: One patient in each group was subsequently lost to follow-up. No significant differences were seen in symptom improvement or need of dilation. At the final endoscopy, 8 of 17 (47%) patients receiving ranitidine had residual erosions or ulceration, compared with 1 of 14 (7%) patients receiving omeprazole (p >0.2). All patients receiving ranitidine had persistent strictures, whereas 8 of 14 (57.1%) patients receiving omeprazole had radiographic and endoscopic resolution of their strictures (p <0.004). CONCLUSION: These data further emphasize the need for vigorously treating esophagitis in patients with acid peptic strictures.

Fluoroscopy is not necessary for Maloney dilation of chronic esophageal strictures.

The use of fluoroscopic guidance for Maloney dilation is controversial. In order to determine if fluoroscopic analysis would enhance the success of dilation and increase recognition of adverse events, we prospectively studied 125 Maloney dilations in 80 patients (mean age, 69.3 years) with mild esophageal strictures. Most strictures (89%) resulted from acid-peptic disease. Operators included two staff physicians (5 and 25 years of experience) and one trainee (1 year of experience). Dilations were performed with the patient seated upright and the operator noting the presence and amount of resistance (dilator size, 36F to 60F; median, 50F). The fluoroscopic monitor was not visible to the operator, and the results were recorded by an observer who did not communicate with the operator. Operator assessment of Maloney dilation was correct in 122 of 125 procedures. Two failures were interpreted as no passage by the operator when passage had occurred as confirmed by fluoroscopy. One failure was interpreted as passage when no passage had occurred as indicated by fluoroscopy. Adverse events included 1 episode of tracheal intubation and failure to recognize the dilator tip curling in the esophagus as observed by fluoroscopy in 6 of 125 (4.8%) procedures. Operator assessment of resistance was more often associated with curling of the dilator on the greater curve of the stomach than with an esophageal stricture. Greater operator experience tended to correlate with increased success and correct interpretation of dilation. Maloney dilations performed with patients at 30 degrees rather than upright at 90 degrees were associated with a marked increase in unsuccessful dilator passage and curling of dilator tip.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of covered versus uncovered wire mesh stents in the canine biliary tract.

Self-expanding wire mesh stents have been developed for endoscopic placement across malignant biliary strictures, but tumor ingrowth may limit the usefulness of open mesh stents. We reasoned that coating the wire mesh might prevent tumor ingrowth. Tissue response to covered and uncovered stents was compared in dogs. Stents were surgically placed in the bile ducts of 22 mongrel dogs through the sphincter of Oddi. Either a silicone-covered stent or an uncovered stent was inserted. Liver function test values remained normal throughout a 1- or 3-month study. Necropsy revealed that all ducts were unobstructed. Bile duct histologic examination revealed mild-to-moderate cellular infiltration in all animals. Mucosal hyperplasia was more marked in the animals with uncovered stents and the bare wires became deeply embedded in bile duct epithelium, whereas the wires of covered stents did not. We conclude that covered stents are well tolerated by the canine bile duct. These results suggest that such stents may be removable, making self-expanding metal stents an appropriate treatment for both benign and malignant biliary strictures.

Capacitive coupled stray currents during laparoscopic and endoscopic electrosurgical procedures.

Capacitively coupled currents may not be appreciated during laparoscopic and endoscopic radiofrequency electrosurgery. Two specific problems are documented and quantified: coupling of current into metal trocar cannulas during laparoscopic surgery and coupling of current into a guide wire during endoscopic surgery. The examples can yield power levels in excess of 25 watts (laparoscopic) and 15 watts (endoscopic) on nearby metal conductors, which can in turn be dissipated into patient organs such as the bowel or the common bile duct. This capacitive coupling can be, in part, responsible for serious patient complications. Methods to minimize capacitive coupling, e.g., active electrode shielding, dispersive metal cannulas, sheathed guide wires, and bipolar active electrodes, are discussed for each example.

Bipolar electrosurgical sphincterotomy.

We tested a newly developed bipolar sphincterotome. Monopolar and bipolar sphincterotomes were employed to cut small bowel smoothly and hemostatically. The bipolar instrument required 17.1 watts while the monopolar required 29.2 watts; these values are significantly different at p = 0.005. Bipolar sphincterotomies were performed via open surgical access on eight dogs. The animals were allowed to recover and were followed for 6 weeks. There was no evidence of stenosis or common duct dilation at autopsy, and serum alkaline phosphatase and bilirubin were within normal limits. Both sphincterotomes were used to cut tissue in vitro and histological examination displayed no evidence of thermal injury at the return electrode site of the bipolar sphincterotome. The lower power levels required by the bipolar sphincterotome may decrease procedure complications.

The interaction between electrosurgical generators, endoscopic electrodes, and tissue.

Endoscopic monopolar and bipolar devices were compared during cutting and coagulation. It was observed on appropriate animal models that the initial resistance (impedance) values recorded correspond to the normal tissue impedance at the electrode. The subsequent impedance values increase 25 to 50 ohms for the coagulator which relates to tissue desiccation and for the cutting electrodes the impedance increases greater than 1000 ohms during the arcing process. At similar power settings, typical monopolar generators produce maximum power at 300 to 500 ohms while typical bipolar generators produce maximum power at 25 to 100 ohms. With impedances greater than 1000 ohms, monopolar generators are capable of higher power output than are bipolar generators. Since cutting is a high impedance process, bipolar cutting electrodes do not perform as intended with typical bipolar generators. Therefore, bipolar cutting electrodes should be employed with a monopolar generator or a generator designed specifically for their use.

In vivo evaluation of monopolar versus bipolar electrosurgical polypectomy snares.

The energy required and tissue damage in bipolar and monopolar polypectomy snares were compared in a canine model. The bipolar snare required an average of 34 joules of energy, whereas the monopolar snare required 228 joules to cut the same diameter of gastric mucosa tended into a polypoid structure (p = 0.0005). The reduced energy delivered to the tissue from the bipolar procedure resulted in only 32% average depth of damage to the underlying gastric wall, whereas the monopolar procedure caused an average 69% (p = 0.001). Surgically created polyps required 247 joules and 69 joules for corresponding monopolar and bipolar polypectomy (p = 0.001). The decreased energy required and the correspondingly reduced damage caused to the underlying bowel wall by the bipolar snare should reduce the incidence of perforation and post-polypectomy syndrome. The bipolar snare completes a local circuit about the snare, eliminating the return electrode and, consequently, the possibility of any return electrode burns. The bipolar snare thus provides an added safety margin during polypectomy.

Pancreatic pseudocysts: clinical and endoscopic experience.

Records of 51 patients with proven pancreatic pseudocyst (PC) were retrospectively reviewed to assess clinical and endoscopic variables. Thirty-nine had surgery after preoperative endoscopic retrograde cholangiopancreatography (ERCP), six patients had ERCP only, and six patients had surgery without prior ERCP. Forty-two pancreatograms were obtained, and all were abnormal. PC communication with the pancreatic duct was present in 29 and ductal obstruction downstream from the PC was shown in 11 studies. Thirty-five cholangiograms were obtained and 19 were abnormal, including ductal narrowing in 16 and biliary calculi in three. PC contents were cultured intraoperatively in 29 patients, and 17 were positive. PC infection was highly correlated with the incidence of recurrent hospitalizations and with PC recurrence. PC infection did not occur significantly more often in patients with communicating PC or in those with preoperative ERCP. Factors that did not influence outcome included PC size, multiplicity, anatomic location, and PC communication with the pancreatic duct. Results from both ERCP and culture of PC contents add significantly to our knowledge of PC disease.