Lower esophageal sphincter and the gastroesophageal antireflux mechanism

Various factors involved in the structure and functional control of the gastroesophageal antireflux mechanism were investigated experimentally in dogs and in a clinical series, with special attention to manometric examination of the lower esophageal sphincter (LES). The prevention of the compressive action of extrinsic paraesophageal structures did not lead to changes either in LES pressure or in LES response to increases in abdominal pressure. The mechanism intrinsic to the gastroesophageal junction, the LES, seems to be primarily responsible for the maintenance of gastroesophageal competence. Also, the LES response to increased ultra-abdominal pressure appears to be a property of the LES itself. Vagotomy performed at different levels did not produce a change in LES pressure, whereas LES response was significantly attenuated after each type of vagotomy. The vagus nerves apparently have no important role in the maintenance of LES pressure, whereas LES response seems to be mediated by a vagal reflex. Intragastric bile instillation caused a significant rise in LES pressure, but chronic intragastric bile contamination did not lead to changes in gastroesophageal competence. This suggests that intragastric bile contamination does not have a deleterious effect on LES competence and does not seem to predispose to gastroesophageal reflux. Of the drugs generally used in premedication for or induction of anesthesia, atropine decreased LES pressure significantly. Metoclopramide, in turn, produced a significant rise in LES pressure and, when administered before atropine, was capable of preventing the depressant effect of atropine on LES pressure. Thus, routine use of metoclopramide in premedication for or induction of anesthesia to prevent the depressant effect of atropine on LES pressure and the possible consequent gastroesophageal reflux, pulmonary aspiration, and postoperative pulmonary complications should be considered. The mean LES pressure after surgery for reflux esophagitis was significantly greater in patients with an objectively good operative result than in those with an objectively poor result. However, some overlapping occurred in LES pressure values between these two groups. The correlation between LES manometry and other examination methods in the evaluation of the operative result of reflux esophagitis seems to be rather good.