Kenneth N. Buchi

Argon laser therapy for hemorrhagic radiation proctitis: long-term results

In chronic radiation proctitis bleeding occurs from mucosal friability and neovascular telangiectasias. Fourteen patients with bleeding from chronic radiation proctitis underwent endoscopic argon laser therapy at 4 to 8 W. The goal of treatment was obliteration of all telangiectasias. The average follow-up was 35 months. Of the 51 procedures, 48 (94%) were performed on outpatients with enema preparation and little or no sedation. A median of three procedures was performed per patient, with two sessions required for initial control of bleeding. Ten patients (71%) required maintenance therapy for recurrent bleeding from telangiectasias that developed after initial therapy. The mean interval between maintenance sessions was 7 months. No immediate or late complications occurred.

High prevalence of adenomatous polyps of the duodenal papilla in familial adenomatous polyposis

Eighteen consecutive asymptomatic patients with familial adenomatous polyposis (both familial polyposis coli and Gardners syndrome) were studied over a 12-month period; side-viewing upper endoscopy and biopsy were used to assess the frequency of adenomatous polyps of the duodenal papilla. Nine of the 18 patients demonstrated adenomatous polyps of the papilla, varying in size and appearance from microadenomas in normalappearing duodenal papillae (two) to a sessile polyp 3 cm in diameter. Two were tubulovillous adenomas (0.5 cm and 2 cm in diameter) and the remainder were tubular adenomas. Severe atypia and malignancy were not encountered. These findings reveal that adenomas of the duodenal papilla are common in individuals with familial adenomatous polyposis. Because of these findings and because of the known risk of periampullary adenocarcinomas and nonmalignant complications of polyps of the duodenal papilla in patients with familial adenomatous polyposis, upper gastrointestinal screening of such patients should include examination of the duodenal papilla with a side-viewing endoscope.

Pharmacodynamics of intravenous ranitidine after bolus and continuous infusion in patients with healed duodenal ulcers

Fifteen adult men who had histories of duodenal ulcer disease were studied for 24 hours during treatment with varying intravenous doses of ranitidine (50 mg every 8 hours, 100 mg every 12 hours, 6.25 mg/hr continuous infusion, and 10 mg/hr continuous infusion) and placebo. Gastric pH was monitored under fasting conditions by means of an indwelling pH sensitive electrode. The continuous infusion regimens provided the most constant level of acid suppression. A “breakthrough” decrease in gastric pH began at approximately 6 PM at the 6.25 mg/hr dose level. The drop in pH at the 10 mg/hr dose level was less impressive. Ranitidine, 100 mg every 12 hours, resulted in better acid suppression than the regimen of 50 mg every 8 hours. A gastric pH ≥ 4 was achieved 35 to 50 minutes after the start of administration for all regimens. The median effective concentration (EC50) of ranitidine was approximately 45 ng/ml. Continuous infusion regimens, with a dosage adjustment for the time of day, may be the optimal dosage regimen for patients requiring continuous protection from gastric damage by hydrochloric acid. Bolus loading doses are not required to speed the onset of effect in the clinical setting.

Vascular Malformations of the Gastrointestinal Tract

The advent of fiberoptic endoscopy, which became widespread in the evaluation of gastrointestinal bleeding throughout the late 1970s and 1980s, has dramatically changed both our understanding of the extent to which vascular malformations account for gastrointestinal blood loss and our ability to treat these lesions at the time of diagnosis. Colonic vascular malformations appear to be the single most common cause of acute or recurrent gastrointestinal bleeding episodes in patients over 60 years of age, being responsible for the bleeding in as many as 35% of such patients. Although less common as a cause of upper gastrointestinal bleeding, these lesions still account for 2% to 5% of bleeding lesions in older patients. Diagnosis is accomplished by endoscopy, and the vascular malformations can then be coagulated via the endoscope using one of a number of thermal systems. The argon laser, the heater probe, and the BICAP system are all effective and safe throughout the gastrointestinal tract, especially in the cecum and right colon, where the majority of sporadic vascular malformations occur. Monopolar cautery and the Nd:YAG laser are equally efficacious, but their greater and less predictable depth of coagulation make them much less safe in the cecum and right colon. There are no apparent advantages in terms of efficacy and safety between laser treatment and the other thermal modalities. The laser has the advantage of being quicker, which is especially important when treating large or multiple lesions. The other modalities have the advantages of portability and low relative cost. Endoscopic therapy with lasers or other thermal devices is nonspecific. The effects are achieved by thermally coagulating the mucosal vascular lesions, allowing the coagulated tissue to slough, and leaving a mucosal ulceration that subsequently heals with re-epithelialization. Endoscopic coagulation has thus been reported effective in the treatment of gastrointestinal mucosal vascular lesions regardless of their etiology or characteristics. It has been effective for sporadic vascular malformations, hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease), radiation proctocolitis, the blue rubber-bleb nevus syndrome, and diffuse gastric antral vascular ectasia (the watermelon stomach). As we move through the 1990s and beyond, these endoscopic modalities offer an effective, relatively safe, and clearly less invasive treatment option for the many patients who experience acute, recurrent, or chronic gastrointestinal bleeding from any of these lesions.

Endoscopic pancreatic cystogastrostomy using the Nd:YAG laser

The rapid development of noninvasive diagnostic imaging methods during the past 10 years has improved our ability to detect pancreatic pseudocysts and has allowed for better definition of their natural history.l,2 As many as 40% of the acute pseudocysts may regress spontaneously within the first 4 to 6 weeks after detection2,3; those that do not regress have a high incidence of significant complications2 and, thus, require intervention. However, considerable controversy still exists about the proper surgical management of pseudocysts. All the standard approaches carry a significant risk of morbidity and mortality, especially when performed early in the development of the pseudocyst. ,4-6 New methods of management are being applied with variable success. These include percutaneous aspiration,7.8 percutaneous drainage,9 and endoscopic drainage using electrocautery4,lO,l1 or the argon laserY This report describes the successful endoscopic use of the Nd:YAG laser to decompress two acute, symptomatic, pancreatic pseudocysts.

Pharmacokinetics of Esmolol in Hepatic Disease

Esmolol is an intravenous beta blocker with a short duration of action. The pharmacokinetics of esmolol and its acid metabolite, ASL‐8123, were studied in nine patients who had stable, biopsy‐proved Laennecs cirrhosis and in three normal volunteer controls. Kinetics were determined after a four‐hour continuous infusion of esmolol at a rate of 200 μg/kg/min. Blood samples were collected during the infusions and at frequent intervals thereafter. The parameters studied were the steady state concentration, the total body clearance, the elimination half‐life, the area under the curve, and the volume of distribution. No significant differences in any of these parameters were detected between control subjects and those with hepatic disease, for either esmolol or its acid metabolite. It is concluded from this study that Laennecs cirrhosis does not cause any change in the pharmacokinetics of esmolol or its major metabolite. Therefore, adjustments in dosage of esmolol are not required for patients with Laennecs cirrhosis.

Day-Night and Individual Differences in Response to Constant-Rate Ranitidine Infusion

Twelve ulcer patients with inactive disease received constant-rate infusions of ranitidine, in doses of 6.25 and 10.0 mg/hr, during separate 24-h spans. Gastric pH and serum ranitidine concentrations were monitored. Serum ranitidine concentrations did not vary significantly after attainment of steady-state. For the group, gastric acidity was controlled above pH 4 during the day; however, at night, when gastric acid secretion was greatest under placebo conditions, ranitidine less effectively controlled gastric pH. There was individual variation in response to ranitidine. Patients (8/12) evidencing control of gastric acidity (pH greater than or equal to 4) for at least 16 h when infused with ranitidine (6.25 mg/h) were considered responders. Those (4/12) not so well controlled were designated poor responders. With parenteral infusion of 6.25, as well as 10.0 mg/h ranitidine, responders evidenced a relatively high 24-h mean pH and only minor day-night variation in gastric acidity. In contrast, poor responders were characterized by a low 24-h mean pH and high-amplitude circadian variation in gastric acidity. Poor responders evidenced statistically significant (p less than 0.05) lower gastric pH responses to parenteral infusions than did responders. A similar, significant difference between the two groups was observed when the percentage of time that gastric pH was maintained below 4 was considered. Differences between responders and poor responders to ranitidine infusion are unknown. Since Zollinger-Ellison syndrome patients were not included in the study, observed differences in drug response cannot be ascribed to hypersecretion of gastric acid.

Endoscopic laser surgery in the colon and rectum

The first applications of laser energy in the gastrointestinal tract occurred barely a decade ago. Since then, endoscopic laser therapy has become widespread in the management of colonic and rectal disease. Applications have been developed for the palliative therapy of obstructing or bleeding malignancies, for the management of some benign and premalignant mucosal diseases and for certain anatomic problems such as anastomotic strictures. Recurrent bleeding from mucosal vascular lesions can be controlled with laser therapy. Methods for treating anorectal disorders also are evolving. The continuing development of new wavelengths of laser energy, of innovative transmission systems, and of new endoscopic systems for increasing ease of access to the gastrointestinal tract all point to ever-increasing applications for laser therapy in colonic and rectal surgery.