Regional Differences in Gastric Acidity and Antacid Distribution: Is a Single pH Electrode Sufficient?

Accurate measurement of intragastric acidity has both clinical and investigational importance in studying gastric pathophysiology. Objectives: The aims of this study were fourfold: (I) to investigate whether regional differences in intragastric acidity exist: (2) to determine intragastric acidity after a standard antacid was administered in both the fasting and fed states; (3) to monitor gastric emptying of and anatomic distribution of radio-labeled antacid during fasting and postprandial periods; and (4) to determine whether the regional effects of ingested antacid correlated with the anatomic distribution of (he antacid. Methods: Eight normal male volunteers were studied after fluoroscopically guided nasogastric placement of a tube assembly containing four pH electrodes, with one electrode in each quartile of the stomach. Simultaneous pH readings were made from the four electrodes while fasting, after administration of fasting antacid (30 ml, 79 mEq buffering capacity), post-prandially, and after postprandial antacid ingestion. All subjects repeated the protocol on a separate day, five of them using radiolabeled antacid. Gastric emptying and gastric distribution over time of radiolabeled antacid were determined for comparison to regional intragastric acidity. Results: Intragastric acidity varied regionally over time in response to meals and to fasting and post-prandial antacid. In the fasting state, intragastric acidity returned to baseline after antacid ingestion in a proximal to distal (cardia to antrum) sequence, while post-prandial antacid resulted in a return to baseline acidity in a distal to proximal (antrum to cardia) sequence. Radiolabeled antacid distribution paralleled intragastric pH and hydrogen ion concentration in the fasting state, with 82% of the antacid localizing in the distance of the stomach within the first minute after antacid ingestion. Postprandially, the greatest initial and most prolonged antacid buffering... [ABSTRACT FROM AUTHOR]