Effects of atropine and glycopyrrolate on esophageal, gastric, and tracheal pH in anesthetized dogs.

Atropine, glycopyrrolate, or saline solution was administered before anesthesia in a blinded, controlled study of 40 dogs scheduled to undergo surgery. Effects of treatment on esophageal, gastric, and tracheal pH were measured with an intraluminal pH meter. Preanesthetic administration of atropine and glycopyrrolate had no effect on esophageal, gastric, or tracheal pH but did result in increased heart rate. Thoracotomy procedures resulted in decreased intraluminal esophageal pH and increased heart rate. Esophageal pH at the level of the thoracic inlet decreased over the duration of surgery.