EFFECT OF ATROPINE ON THE FREQUENCY OF REFLUX AND TRANSIENT LOWER ESOPHAGEAL SPHINCTER RELAXATION IN NORMAL SUBJECTS

Background & Aims: Low basal lower esophageal sphincter (LES) pressure is believed to be an important mechanism of reflux. The effects of at ropine on the frequency and mechanisms of gastroesophageal reflux unde r the experimental conditions of a low basal LES pressure in 13 normal subjects were studied. Methods: LES pressure, esophageal pressures, e sophageal pH, and crural diaphragm electromyogram were recorded simult aneously in the postprandial period for 30 minutes before and two 30-m inute periods after the injection of atropine. Results: Atropine reduc ed the basal LES pressure from 16.4 +/- 3 to 8.7 +/- 2 mm Hg. The freq uencies of reflux in the control and two postatropine periods were 3.5 +/- 0.5, 0.4 +/- 0.2, and 0.8 +/- 0.3, respectively (P < 0.05). The f requencies of transient LES relaxations decreased from 3.5 +/- 0.5 in the control to 0.4 +/- 0.2 and 1.5 +/- 0.4 in the two postatropine per iods (P < 0.05). Transient LES relaxation and associated inhibition of the crural diaphragm was the major mechanism of reflux under conditio ns of low LES pressure induced by atropine. Conclusions: Atropine-indu ced low LES pressure does not predispose to reflux in normal healthy s ubjects. Atropine reduces the frequency of reflux by its inhibitory ef fect on the frequency of transient LES relaxation.