Comparison of argon laser photocoagulation and bipolar electrocoagulation for endoscopic hemostasis in the canine colon

Severe bleeding from the lower gastrointestinal tract commonly occurs from mucosal lesions such as angiodysplasia and less often from acute ulcerations. Endoscopic coagulation of such lesions is now feasible. Our purpose was to compare the efficacy and histologic injury of bipolar electrocoagulation and argon laser photocoagulation applied at laparotomy in the canine colon. After right colotomy and heparinization in adult mongrel dogs, bleeding standard ulcers were randomly assigned to treatment or control. The colonic ulcers randomized to each group were not significantly different in size or bleeding rate. Efficacy of treatment was evaluated acutely. Adjacent normal mucosa was treated with the same modality as the ulcer to simulate treatment of a mucosal lesion. The same total exposure time (argon laser photocoagulation) or number of pulses (bipolar electrocoagulation) was used for these paired treatments. Gross and histologic injury were determined after 7 days. Both argon laser photocoagulation and bipolar electrocoagulation were uniformly effective in controlling bleeding from standard colonic ulcers and the incidence of full thickness injury was similar, 33%-48%. The histologic damage seen with normal mucosa treatment was consistently less than with standard ulcers for all treatment groups. The difference is easily explained by the reduction in colonic wall thickness of about 50% with creation of standard ulcers. In our opinion, argon laser photocoagulation and bipolar electrocoagulation are safe enough to be used in clinical trials for control of colonic bleeding from mucosal lesions but not acute colonic ulcers.

Comparison of endoscopic electrocoagulation and laser photocoagulation of bleeding canine gastric ulcers

The most promising endoscopic hemostatic techniques all depend upon heat to coagulate. Four thermally active techniques under similar controlled conditions in this endoscopic study were compared. The study was undertaken to compare the efficacy and histologic damage of monopolar electrocoagulation (MPEC), bipolar electrocoagulation (BPEC), argon laser photocoagulation (ALP) and neodymium-yytrium-aluminum-garnet (YAG) laser photocoagulation applied endoscopically to control bleeding from standard canine gastric ulcers. An open-closed model utilizing a nontraumatic intestinal clamp in heparinized adult mongrel dogs was used. Bleeding ulcers were randomly assigned to an endoscopic treatment modality or control. The endoscopic techniques and parameters of treatment for this study were established from a previous experience with each modality and from endoscopic treatment in pilot studies. Quantitative efficacy and subjective ease of endoscopic treatment were evaluated acutely; gross and histologic injury were determined after 7 days. Our conclusions were that more energy or greater power was required with each method to treat bleeding standard ulcers efficiently through the endoscope than at laparotomy. It was also concluded that each method was 93% or more effective in halting bleeding in this canine ulcer model but there were differences in ease of endoscopic use. Both lasers were much easier to apply than electrocoagulation. The order of decreasing ease of application was YAG, ALP, MPEC, BPEC. Argon laser and BPEC caused significantly less tissue injury than either MPEC or YAG. The order of increasing injury or decreasing margin of safety was ALP, BPEC, YAG and MPEC. In contrast to electrocoagulation, especially monopolar, laser related tissue injury was generally predictable and correlated with total treatment energy, animal weight or gastric overdistension, or both. The limitations, advantages, and disadvantages of each hemostatic technique are discussed and compared.

Acute hepatitis B: a further serological characterization

Sequential determinations of HBsAg, anti-HBs, HBeAg, anti-HBe, and anti-HBc in thirteen patients with acute hepatitis B have shown that the viral antigens and their respective antibodies may be simultaneously absent (9/13 with serologic window) or present (6/13 with presumed immune complex formation) in the early convalescent period. These data emphasize the usefulness of sequential determinations of antigen and antibody in the unequivocal assessment of etiology and potential for chronicity and contagion) in resolving acute hepatitis B. The transient appearance of an antibody to liver specific protein (anti-LSP) in eleven out of thirteen patients was documented; we found no correlation of anti-LSP titers with viral antigens or host antibody titers.

Peptic ulcer: new therapies, new diseases

Although hospitalizations and deaths attributable to peptic ulcer have decreased notably during the past decade, it is not certain whether this decrease is because of reduced incidence of new cases or changes in other factors, such as the severity of the disease. Several genetic traits associated with peptic ulcer have been recognized. Hyperpepsinogenemia I is the most prevalent. Peptic ulcer is a heterogeneous group of disorders with multiple genetic and environmental causes. One manifestation of the diversity of ulcer disease is the variety of physiologic abnormalities seen in patients. The use of endoscopy has enabled more reliable evaluation of new treatments. Histamine H2-receptor antagonists are the dominant mode of treatment, but increasing attention is being given to agents that enhance the resistance of the mucosa to injury, such as prostaglandins. Because of the lower frequency of side effects, proximal gastric vagotomy is gradually replacing truncal vagotomy with drainage. The possibility that endoscopic treatments, such as laser coagulation, may reduce mortality from bleeding ulcers is being investigated.

Laparoscopy: advances in biopsy and recording techniques

We have developed a second puncture accessory set and photographic technique for laparoscopy which are easy to use and potentially safer than others commonly used. A smaller second trocar (4mm) with various biopsy accessories, suction-coagulation cannula, and insulated grasper has been developed and successfully used in a series of more than 400 high risk patients where tissue samples were obtained under local anesthesia without serious complications or fatalities. The smaller size facilitated easy and safe introduction and manipulation. For laparoscopic photography a presterilized quartz rod attached to a sealed flash tube is used which is synchronized with a flash generator and 35-mm camera. An accessory trocar and the quartz rod are introduced under visual guidance parallel to the examining trocar. A separate "modeling" light is incorporated to provide illumination for observation. This photographic technique provides excellent illumination through a smaller trocar and probe than previously reported.

Computer-assisted electrocoagulation: bipolar vs. monopolar in the treatment of experimental canine gastric ulcer bleeding

A prospective, randomized, controlled experiment using a canine model of severely bleeding gastric ulcer was performed to compare the hemostatic efficacy and tissue damage produced by one bipolar and two monopolar electrodes. Both monopolar electrodes were insulated to their tips; they differed with respect to their surface area (3 mm2 vs. 4 mm2). The force of electrode application was controlled. An analog computer monitored the energy per electrode application and predetermined the duration of each application. Fifty-nine standard acute bleeding ulcers were made and treated one at a time in six heparinized foxhounds at sterile laparotomy. Treatment was randomized to the bipolar or to one of the monopolar electrodes within each of three bleeding strata. No significant difference was observed in hemostatic efficacy among the three electrodes. Treated ulcers were examined histologically after 5 to 7 days to determine the maximum tissue damage produced: Bipolar electrocoagulation caused significantly less damage than electrocoagulation with either monopolar electrode. We conclude that with these electrodes, bipolar electrocoagulation is equally effective for stopping bleeding but results in less tissue injury than monopolar electrocoagulation in this experimental model.

YAG laser treatment of experimental bleeding canine gastric ulcers

The neodymium-YAG laser was used to treat bleeding experimental canine gastric ulcers in four separate studies: (a) Extensive investigation by using the 1.06 micron YAG laser wavelength was performed to determine optimal YAG laser treatment parameters to maximize hemostatic efficacy while minimizing associated tissue injury. Eight out of 43 combinations of power, pulse duration, and spot size, with and without coaxial CO2 were found to be best. The range of settings tested were 30-90 W for power; 0.2-1 sec pulse duration; and 2.0- and 3.4-mm spot sizes, with and without coaxial CO2. (b) Five of these treatment combinations were studied in more detail to assess the respective effect of spot size, pulse duration, and presence or absence of coaxial CO2 on tissue injury. In spite of optimizing treatment parameters and conditions, each combination caused significant damage to the gastric wall. No acute perforations occurred. (c) Endoscopic YAG laser treatments were applied successfully. Efficacy and total energy requirements were compared with similar treatments previously done at laparotomy. (d) In an attempt to reduce tissue damage, the YAG laser was modified to produce a 1.3-microm wavelength. YAG laser treatment using this alternative wavelength caused more immediate damage than the 1.06 micron wavelength. From these studies we conclude: (a) YAG laser photocoagulation effectively stopped experimental gastric ulcer bleeding when applied both at laparotomy and endoscopy; (b) compared to untreated ulcers, YAG laser treatment caused significant tissue damage despite control of several important variables (power output, spot size, pulse duration, and coaxial CO2); (c) increased total energy, larger spot size, and longer pulse duration appeared related to increased tissue injury with YAG laser treatment; total energy was the single most important factor. (d) Successful hemostasis with endoscopic application of the YAG laser required more total energy than treatment of laparotomy. (e) Modification of the YAG laser wavelength to 1.3 microns did not reduce tissue injury.

Failure of atropine to inhibit gastrin-17 stimulation of the lower esophageal sphincter in man

Heptadecapeptide gastrin I (G-17) contrast the lower esophageal sphincter (LES) in man and animals. Previous studies in man found that atropine infusion (12 microgram kg-1hr-1) inhibited the effect of gastrin on the LES, suggesting that this effect of gastrin is mediated by a cholinergic mechanism. Studies in the opossum have not shown similar inhibition. To reevaluate the interaction of atropine and G-17 on the LES, 5 normal males were studied. Submaximal and maximal effective doses of G-17 were used with both atropine infusion (12 microgram kg-1hr-1) and rapid intravenous injection (1 mg). There was a small decrease in basal LES pressure with atropine infusion. However, neither atropine infusion nor rapid intravenous injection inhibited LES stimulation by submaximal and maximal doses of G-17. The results do not support the hypothesis that LES responses to gastrin are mediated by an atropine-sensitive cholinergic mechanism.

Detection of antibodies directed against a liver-specific membrane lipoprotein in patients with acute and chronic active hepatitis

A specific and sensitive radioimmunoassay was used to measure the levels of antibody to a liver-specific membrane lipoprotein in patients with acute and chronic liver disease. Antibody was detected in 29 of 30 patients with chronic active hepatitis (all of 15 HBsAg-negative and 14 of 15 HBsAg-positive cases), and in 10 of 17 patients with chronic persistent hepatitis but at significantly lower titer. The titer of antibody to the lipoprotein showed a significant correlation with activity of disease as judged histologically and biochemically. Transiently elevated levels were found in 20 of 21 patients with acute viral hepatitis, but there was no correlation with the degree of liver damage. Antibody to liver-specific membrane protein may be part of the final common pathway of liver-cell damage in both HBsAg-positive and HBsAg-negative chronic activite hepatitis, whereas other immune mechanisms determine the liver-cell injury in acute viral hepatitis.