Multipoint measurement of intragastric pH in healthy preterm infants.

Background: The diagnostic use of 24 hour oesophageal pH monitoring in infants is controversial because of the impact of feed buffering of gastric acidity.

Aim: To re-evaluate the effect of feeding on gastric pH and reflux using multipoint pH measurements.

Subjects: Fifteen healthy premature infants fed every four hours.

Methods: Oesophagea pH and intragastric pH at 3, 6, and 9 cm below the lower oesophageal sphincter were simultaneously measured using a four channel pH probe for four hours after bolus feeding. Parameters of pH were compared for the different levels within the stomach. During reflux episodes, the nadir pH was compared with intragastric pH at all levels.

Results: The proximal stomach was more significantly buffered by feeding and slower to re-acidify postprandially than the mid and distal stomach (42.2% of the time at pH < 4 compared with 58.7% and 55.7% respectively). During 27 of 62 gastro-oesophageal reflux episodes, nadir oesophageal pH was lower than the pH of the proximal stomach but always equal to or higher than the pH of the distal stomach.

Conclusions: These data indicate that previous studies may have overestimated the effect of feeding on gastric acidity and reflux.

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The use of 24 hour distal oesophageal pH monitoring as a diagnostic test for gastro-oesophageal reflux (GOR) disease in infants, particularly premature infants, is controversial, with little consensus among investigators on the appropriate normal/abnormal diagnostic criteria applicable in these patients. Studies of intragastric pH in premature infants have reported that the average percentage recording time that the gastric pH was below 4 was low, 24.5-42.4%, (1 2) and this has led to the derivation of "corrected" reflux indices (% time oesophageal pH < 4 when gastric pH < 4) for diagnosis of reflux. The utility of this approach has yet to be determined, but has led to a recommendation that oesophageal pH monitoring is deemed inappropriate in premature infants. (3) It is also important to note in this context that a large study of 90 infants recently failed to find any effect of gastric buffering on reflux index. (4) Therefore, the use of simultaneous gastric pH monitoring to correct for the effect of food buffering on gastric pH may be flawed. Furthermore, recent studies in preterm infants have used a gastric pH probe situated in the cardia. However, adult studies have previously shown that there are substantial regional differences in intragastric pH, with pH significantly less acidic in the cardia than in the …