EFFECT OF NASOGASTRIC SUCTION AND RANITIDINE ON THE CALCULATED GASTRIC INTRAMUCOSAL PH

Objective. To study the effect of nasogastric suction and ranitidine o n the determination of gastric intramucosal pH (pH(i)). Design: Prospe ctive study. Setting.. Clinical research unit at a university hospital intensive care department. Subjects. 12 healthy volunteers. Intervent ions: After a 2-h measurement control period a tonometer was connected to nasogastric suction for 2 h, and thereafter ranitidine was given i ntravenously and gastric pH(i) measured. Measurements and results: Dur ing each 2-h measurement period gastric PCO2, gastric pH(i), and pH ga p were determined every 30 min. Luminal pH was measured after insertio n of tonometer and at the end of each study period. Neither nasogastri c suction nor ranitidine had an effect on the coefficient of variation for either gastric PCO2 or pH(i). Compared to control and nasogastric suction periods, after ranitidine mean gastric pH(i) was higher (cont rol 7.22 +/- 0.08; nasogastric suction 7.23 +/- 0.07; after ranitidine 7.31 +/- 0.06: p < 0.001) mean gastric PCO2 lower (control 6.4 +/- 1. 3; nasogastric suction 6.5 +/- 1.3; after ranitidine 5.3 +/- 0.9, p < 0.001) and pH gap lower (control 0.18 +/- 0.08; nasogastric suction 0. 17 +/- 0.05, after ranitidine 0.09 +/- 0.06, p (-0.01). Luminal pH inc reased after ranitidine in each subject. Conclusions: H-2 blockers hav e no effect on the reproducibility of gastric pH(i) measurements, but the use of H-2 blockers modifies the normal values for gastric pH(i) i n healthy subjects.