Effects of preoperative administration of intravenous crystalloids on the gastric effects of famotidine were studied in 89 patients scheduled for elective surgery in the afternoon. Patients were randomly assigned to one of six groups. Groups P1, P2, and P3 received 2.0 mL of intramuscular saline (placebo) and groups F1, F2, and F3 received 20 mg of intramuscular famotidine 1 h before anesthesia. All patients fasted for 14-18 h before surgery. No fluid was administered to groups P1 and F1 preoperatively, whereas 500 mL of intravenous fluid was given to the other groups over a period of 4-5 h before anesthesia: a maintenance fluid with 10% glucose to groups P2 and F2, and lactated Ringer's solution without glucose to groups P3 and F3. After anesthetic induction, the stomach was aspirated using a nasogastric tube and volume and pH of the contents were measured. The gastric volume was significantly less in F2 (4.2 +/- 1.2 mL, mean +/- SEM) than in P1 (30.7 +/- 5.5 mL) (P less than 0.01) and in F3 (12.7 +/- 2.1 mL) than in P3 (26.8 +/- 4.4 mL) (P less than 0.05). There was no significant difference between P2 (23.4 +/- 4.6 mL) and F2 (17.5 +/- 3.5 mL). Mean pH values were significantly higher in F1 (6.82 +/- 0.48) than in P1 (3.21 +/- 0.72) (P less than 0.01). No significance was observed between P2 (3.65 +/- 0.62) and F2 (4.53 +/- 0.77), or P3 (3.17 +/- 0.81) and F3 (5.03 +/- 0.80).(ABSTRACT TRUNCATED AT 250 WORDS)