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Effects of single-dose oral ranitidine and sodium citrate on gastric pH during and after general anaesthesia


The effects on gastric pH of the H2-receptor antagonist ranitidine (R) with 0.3 molar (M) sodium citrate (SC) as an oral effervescent and those of plain SC were studied in 25 patients scheduled for elective surgery. Following induction of general anaesthesia, the gastric contents were evacuated via a nasogastric tube, and a pH electrode was placed 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 seven received 50 ml SC alone (Group SC). The drugs were administered orally in a double-blind fashion, and the gastric pH was recorded continuously 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 7.0 (6.2–7.5), 6.9 (6.3–7.3), and 4.9 (1.9–7.3), respectively, at emergence from anaesthesia (P < 0.05 for R300 vs SC and R150 vs SC). Two minutes 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 remained above 2.5 for 14 hr (P = NS). Plain SC increased the gastric pH within two minutes to a mean of 6.8 (6.7–7.0), and maintained it above 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 administered orally after induction of anaesthesia. However, the effectiveness 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 combination should be administered.


On a étudié chez 25 patients programmés pour une chirurgie non urgente, les effets sur le pH gastrique d’un antagoniste des H2 récepteurs, la ranitidine (R) additionnée de citrate de sodium (CS) 0,3 molaire (M) effervescent, per os et ceux du CS seul. Apres l’induction de l’anesthésie générate, le contenu gastrique est évacue par une sonde nasogastrique et une électrode à pH placée dans l’estomac. Ensuite, huit patients regoivent 300 mg de R avec CS (Groupe R300), dix patients reçoivent 150 mg de R avec CS (Groupe R150) et sept patients reçoivent 50 ml de CS seul (Groupe CS). Ces médicaments sont administrés oralement en double aveugle, et le pH gastrique est enregistré continuellement pendant 24 h. Les valeurs moyennes de base du pH (écart) sont de 1,2 (0,8–1,8), 1,3 (1,0–1,8) et 1,2 (0,9–1,6) respectivement dans les groupes R300, R150 et CS (P = NS entre les groupes). Les valeurs s’accroissent respectivement de 7,0 (6,2–7,5), 6,9 (6,3–7,3) et 4,9 (1,9–7,3), au réveil de l’anesthésie (P < 0,05 pour R300 vs CS et R150 vs CS). Deux min après l’administration de R300 et R150, on atteint respectivement des valeurs moyennes (écart) du pH gastrique de 6,8 (5,8–7,5), et de 5,6 (1,2–7,0), qui restent audessus de 2,5 pendant 14 h (P = NS). Le CS seul augmente le pH gastrique dans les 2 min à une valeur moyenne de 6,8 (6,7–7,0) et le maintient audessus de 2,5 pendant 6 h (P < 0,05 pour R300 versus CS à 8, 10, 12 et 14 h après l’induction). Nous concluons qu’autant la combinaison de R avec CS que le CS seul sont rapidement efficaces pour neutraliser l’acidité gastrique lorsqu’ils sont administré après l’induction de l’anesthésie. Cependant, l’efficacité du CS seul est de plus courte durée, et si le maintien du pH gastrique audessus de 2,5 est nécessaire pour plus de 6 h, on devrait administrer la combinaison de R et de CS.


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Correspondence to Peter G. Atanassoff.

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Atanassoff, P.G., Rohling, R., Alon, E. et al. Effects of single-dose oral ranitidine and sodium citrate on gastric pH during and after general anaesthesia. Can J Anaesth 42, 382 (1995).

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Key words

  • agents: ranitidine, sodium citrate
  • gastric ph: continuous monitoring, general anaesthesia