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 determine d by tonometry; b) reduces the variability of these measurements. Desi gn: Prospective, double blind, randomized, placebo-controlled study. S etting: General Intensive Care Unit of a teaching hospital. Patients: Twenty-five critically ill, mechanically ventilated patients requiring arterial catheter and nasogastric tube. Interventions: Tonometer plac ement; blind, random administration of intravenous ranitidine (50 mg) or placebo. Measurements and main results: Tonometer saline PCO2 (PCO( 2)i), arterial blood gases, gastric juice pH and pHi were determined i mmediately 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: PCO(2)i or pHi; pHi was 7.34 +/- 0.14 be fore 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 adminis tration (p = 0.55), Ranitidine did not modify the coefficients of vari ation of PCO(2)i or pHi, either. No significant changes in gastric jui ce pH, PCO(2)i or pHi were observed in the placebo group. Conclusions: In critically ill patients, ranitidine has no effect on pHi values, a nd does not increase the reproducibility of pHi measurements.