Diurnal variation in the chemical clearance of acid gastroesophageal reflux in infants.

BACKGROUND & AIMS: Clearance of acid gastroesophageal reflux is biphasic. During volume clearance, refluxed material is cleared from the esophagus by peristalsis, and during chemical clearance, acidified esophageal mucosa is neutralized by saliva and possibly secretions from the esophageal lumen. In this study, we examined the effects of feeding on the durations of volume clearance and chemical clearance.
METHODS: Combined pH/multichannel intraluminal impedance tracings from 12 symptomatic infants (median age, 20 weeks) were analyzed. Acid gastroesophageal reflux episodes having both volume clearance and chemical clearance components were grouped into 1 of 4 feeding cycle phases (feeding, first hour postprandial, second hour postprandial, and fasting).
RESULTS: Mean duration of volume clearance and chemical clearance was 7.0 +/- 2.3 and 36.3 +/- 8.5 minutes (P = .001), respectively, per patient and 24.7 +/- 2.7 and 127.5 +/- 10.7 seconds (P < .0001), respectively, per episode. Whereas volume clearance did not change throughout the feeding cycle, chemical clearance was significantly prolonged during fasting (132.2 +/- 18.4 seconds) compared with feeding (13.5 +/- 4.1 seconds, P = .0046) and 1st postprandial (64.0 +/- 19.4 seconds, P = .0333). Statistical analysis failed to demonstrate a significant relationship between nadir pH and chemical clearance (P = .3104) or between chemical clearance and the interaction between nadir pH and feeding cycle.
CONCLUSIONS: Chemical clearance is significantly prolonged during fasting in infants. Falling pH alone cannot explain declining chemical clearance efficiency during later postprandial periods. We speculate that inefficient chemical clearance during fasting is likely due to reduced efficiency of acid clearance mechanisms that could include salivation, swallowing, peristalsis, and/or intraluminal secretion.