Usefulness of combined gastric and esophageal pH monitoring in detecting gastroesophageal alkaline and mixed reflux

Clinical relevance of esophageal and gastric pH measurements in patients with gastro-esophageal reflux disease (GERD)

BACKGROUND

Gastro-esophageal reflux disease (GERD) is a highly prevalent disease caused by the exposure of the esophagus to refluxed gastric contents. Proton pump inhibitors (PPIs) are the mainstay of current treatment. At present, the assessment of the efficacy of different PPIs in the treatment of GERD employs two measures: esophageal and gastric pH monitoring. Esophageal pH monitoring is the most accurate method of detecting reflux episodes and, therefore, its role as a diagnostic modality is well accepted. Gastric pH monitoring, on the other hand, is an accurate measure of gastric acid pH, but its relevance to patients with GERD is questionable, since recordings correlate poorly with esophageal acid exposure.

OBJECTIVE

This paper reviews (based on a Medline literature search, 1980-2004) the clinical relevance of esophageal and gastric pH measurements in both the management of GERD and in the evaluation of the efficacy of PPI therapy.

FINDINGS AND CONCLUSIONS

Evidence presented suggests that the assessment of esophageal pH yields data of greater relevance to patients with GERD than does data from gastric pH. This largely arises from the fact that esophageal pH monitoring assesses the pH of the refluxate and the frequency of reflux episodes at the mucosal site affected by the disease. The use of esophageal pH monitoring is recommended in patients who fail to present with endoscopic evidence of esophagitis, those with extra-esophageal symptoms, those who have failed traditional anti-reflux therapies, and those who are potential candidates for anti-reflux surgery. In recent years, the technique has benefited from the development of a wireless pH probe, and there is also an increasing body of evidence supporting its use in combination with other emerging technologies, such as Bilitec monitoring and multichannel intraluminal impedance. Such an approach is anticipated to aid both the diagnosis of GERD and the characterization of gastro-esophageal reflux (GER) in these patients.

Analysis of the optical properties of bile

Invasive bile determination is very useful in the diagnosis of many gastric pathologies. At the moment, this measurement is performed with Bilitec 2000, an optical fiber sensor, that is based on absorption by bilirubin. Nevertheless, erroneous evaluations are possible, due to the different configurations which the bilirubin molecule can adopt. The optical behavior of human samples of pure bile and bile+gastric juice has been examined using an optical fiber spectrophotometer and two suitably modified Bilitec 2000 units. A protocol has been established for the treatment of biological fluids, in order to make it possible to study the behavior of their optical properties as a function of pH and concentration without causing any alteration in the samples. The analysis of pH dependence evidenced the presence of different calibration curves at different pH values: the self-aggregation of the bilirubin molecules observed in pure bile samples was almost totally absent in the gastric samples. Measurements carried out on Bilitec 2000 showed that the most appropriate wavelength for bilirubin detection in the stomach should be 470 nm.

Long-term ambulatory enterogastric reflux monitoring. Validation of a new fiberoptic technique

A new technique for the long-term ambulatory detection of enterogastric and nonacid gastroesophageal reflux has been conceived, developed, and validated. It is based on the use of a fiberoptic sensor that utilizes the optical properties of bile. In vitro studies have shown good precision, good stability, sensitivity of 2.5 mumol/liter bilirubin concentration, as well as a useful working range of 2.5-100 mumol/liter bilirubin concentration. In vivo studies have been performed in 29 subjects. Simultaneous gastric aspirations have allowed a comparison of fiberoptic system measurements both with spectrophotometric analysis and bile acid concentrations of corresponding gastric juice samples. Linear correlations were shown between fiberoptic assessment and both spectrophotometric and bile acid concentration findings (P < 0.01). Simultaneous assessment of reflux with the fiberoptic system and cholescintigraphy has shown a 92.9% concordance as regards the presence or absence of reflux. Present results imply that the fiberoptic system is an important tool for the understanding of the clinical relevance of enterogastric and nonacid gastroesophageal reflux.

Effects of atropine and glycopyrrolate on esophageal, gastric, and tracheal pH in anesthetized dogs

Atropine, glycopyrrolate, or saline solution was administered before anesthesia in a blinded, controlled study of 40 dogs scheduled to undergo surgery. Effects of treatment on esophageal, gastric, and tracheal pH were measured with an intraluminal pH meter. Preanesthetic administration of atropine and glycopyrrolate had no effect on esophageal, gastric, or tracheal pH but did result in increased heart rate. Thoracotomy procedures resulted in decreased intraluminal esophageal pH and increased heart rate. Esophageal pH at the level of the thoracic inlet decreased over the duration of surgery.

Combined esophageal and gastric pH-metry in healthy volunteers. Influence of cable through LES and effect of misoprostol

In order to evaluate whether combined esophageal and gastric pH-metry is feasible without interference due to the transcardial cable, four 24-hr ambulatory esophageal pH-metries were carried out in seven healthy volunteers in a randomized order. In two studies only one glass electrode was used. It was placed 5 cm above the lower esophageal sphincter. In the two other studies an additional electrode was placed in the corpus region 10 cm below the lower esophageal sphincter. In order to obtain a wide range of pH values, misoprostol (400 micrograms) was given at 9 AM and 9:15 PM in two studies. In the two other studies placebo was given. Misoprostol exerted only a weak and short-lasting effect on gastric acidity. The four measuring conditions did not differ with respect to medians of esophageal reflux time and duration of single reflux episodes, Kendall's coefficient of concordance yielded a high reproducibility for both variables (P less than 0.0025). Thus, combined esophageal and gastric pH-metry is feasible and highly reproducible.