Pre-anesthetic cimetidine alteration of gastric fluid volume and pH.

Gastric volume and pH were studied immediately after induction of anesthesia and endotracheal intubation in 101 elective surgical patients. Of 44 patients not given cimetidine, 82% had a gastric pH less than 2.5 with a mean pH of 1.6; 45% of these patients had a gastric aspirate pH less than 2.5 associated with a volume exceeding 25 ml. In 57 patients premedicated with intravenous cimetidine at variable intervals (15 to 60 minutes) prior to induction of anesthesia, a significant time-dependent increase was noted in gastric pH (p less than 0.001) together with a decline in gastric volume (p less than 0.001). Of the patients given intravenous cimetidine (mean 4.5 mg/kg) 45 minutes prior to induction of anesthesia, 90% had a gastric pH greater than 2.5. The increase in gastric pH after cimetidine administration would result in a reduced chemical pulmonary reaction should aspiration occur during induction of anesthesia.