EFFECTS OF SINGLE-DOSE ORAL RANITIDINE AND SODIUM-CITRATE ON GASTRIC PH DURING AND AFTER GENERAL-ANESTHESIA

The effects on gastric pH of the H-2-receptor antagonist ranitidine (R ) with 0.3 molar (M) sodium citrate (SC) as an oral effervescent and t hose of plain SC were studied in 25 patients scheduled for elective su rgery. Following induction of general anaesthesia, the gastric content s were evacuated via a nasogastric tube, and a pH electrode war; place d in the stomach. Then eight patients received R 300 mg plus SC dose ( Group R300), ten received R 150 mg plus SC dose (Group R150), and seve n received 50 mi SC alone (Group SC). The drugs were administered oral ly in a double-blind fashion, and the gastric pH was recorded continuo usly over a period of 24 hr. Mean (range) baseline pH values were 1.2 (0.8-1.8), 1.3 (1.0-1.8), and 1.2 (0.9-1.6) in the R300, R150, and SC groups, respectively (P = NS among groups). These values increased to 70 (6.2-7.5), 6.9 (6.3-7.3), and 4.9 (1.9-7.3), respectively, at emerg ence from anaesthesia (P < 0.05 for R300 vs SC and R150 vs SC). Two mi nutes after administration of R300 and R150, a mean (range) gastric pH of 6.8 (5.8-7.5), and 5.6 (1.2-7.0), respectively, was reached, and r emained above 2.5 for 14 hr (P = NS). Plain SC increased the gastric p H within two minutes to a mean of 6.8 (6.7-7.0), and maintained it abo ve 2.5 for six hours (P < 0.05 for R300 vs SC at 8, 10, 12, and 14 hr after induction). We conclude that both the combination of R plus SC, and SC alone are rapidly effective in neutralizing gastric acid when a dministered orally after induction of anaesthesia. However, the effect iveness of plain SC is shorter-lived, and if maintenance of gastric pH above 2.5 for longer than six hours is needed, the R plus SC combinat ion should be administered.