Effects of atropine, glycopyrrolate, and cimetidine on gastric secretions in morbidly obese patients.

Gastric volume and pH were studied immediately after induction of anesthesia and endotracheal intubation in 40 morbidly obese patients undergoing gastric bypass procedures. Of 14 patients receiving intramuscular atropine (0.6 mg) preoperatively, 67% had gastric pH values < 2.5; 33% of these patients had both a gastric pH < 2.5 and a volume > 20 ml. When the drug administered was intramuscular glycopyrrolate (0.3 mg), 62% of the patients had gastric pH values > 2.5; 30% had both gastric pH values < 2.5 and volumes > 20 ml. Differences between the two drugs were not significant. Thirteen patients received cimetidine orally at midnight preoperatively and again 2 to 4 hours before the induction of anesthesia. Patients in this group had gastric pH values that were significantly higher than those observed in patients given anticholinergic drugs. Only 15% had gastric pH values < 2.5. Gastric volumes observed in patients receiving cimetidine were not significantly different from those receiving anticholinergic drugs. Whereas only 7.9% of patients receiving cimetidine had both low pH values and gastric volumes > 20 ml, this was not statistically different from the observations made in patients receiving atropine or glycopyrrolate. Despite this, it is concluded that cimetidine administered before the induction of anesthesia in morbidly obese patients may reduce the high risk of aspiration pneumonitis in such patients.