A study of the action of oral cimetidine or placebo on the pH and the volume of gastric contents when administered the evening or the morning before general anesthesia. A double blind study.

A double blind experiment studied the effect on the pH and on the volume of gastric fluid after the administration of either cimetidine or a placebo as premedication before scheduled operations. The patients were divided into 4 groups. Group A received 400 mg of cimetidine the night before the operation and the placebo in the morning. Group B received 400 mg of cimetidine the night before and 200 mg in the morning. Group C received the placebo in the evening and in the morning and group D received the placebo in the evening and 200 mg of cimetidine in the morning. Compared to the placebo group C, the action of cimetidine on the pH was only significant in the 2 groups (B, D) which received a morning dose (p less than 0.01), but cumulative evening and morning administration of cimetidine (group B) was the only method which statistically diminished the mean volume of gastric fluid (p less than 0.05). The administration of repeated doses of cimetidine increased the pH and decreased the volume of gastric fluid and would thus seem to be a good method to prevent inhalation pneumonia during anesthesia.