Effect of ranitidine on gastric intramucosal pH in critically ill patients

Objective: To determine whether ranitidine a) increases the values of gastric intramucosal pH (pHi) in critically ill patients, as determined by tonometry; b) reduces the variability of these measurements. Design: Prospective, double blind, randomized, placebo-controlled study. Setting: General Intensive Care Unit of a teaching hospital. Patients: Twenty-five critically ill, mechanically ventilated patients requiring arterial catheter and nasogastric tube. Interventions: Tonometer placement; blind, random administration of intravenous ranitidine (50 mg) or placebo. Measurements and main results: Tonometer saline PCO2 (PCO2i), arterial blood gases, gastric juice pH and pHi were determined immediately before, and 2, 4, 6 and 8 h after, ranitidine (12 patients) or placebo (13 patients). Ranitidine significantly increased gastric juice pH, but did not affect PCO2i or pHi; pHi was 7.34 ± 0.14 before ranitidine, and 7.30 ± 0.12, 7.31 ± 0.11, 7.31 ± 0.14 and 7.31 ± 0.12 - 2, 4, 6 and 8 h, respectively, after ranitidine administration (p = 0.55). Ranitidine did not modify the coefficients of variation of PCO2i or pHi, either. No significant changes in gastric juice pH, PCO2i or pHi were observed in the placebo group. Conclusions: In critically ill patients, ranitidine has no effect on pHi values, and does not increase the reproducibility of pHi measurements.