Monitoring gastric pH levels.

Stress gastritis in critically ill patients can be prevented by neutralizing gastric acid. Antacids are commonly used to accomplish this, but whatever the agent used, proper pH monitoring by aspiration of gastric fluid is necessary. This technique is labor intensive, but alternative methods have not proved practical. A simple pH probe in a nasogastric tube was tested to evaluate its accuracy in determining gastric pH in critically ill patients. Thirty-one patients in the surgical intensive care unit were studied for an average of 5.2 days with a range of one to 21 days. A nasogastric tube with a graphite and antimony pH sensor implanted in the tip (GrapHProbe ST, Zinetics Medical) was placed in each patient. The probe can be attached to a pH meter to read the gastric pH. Double aspiration samples from the nasogastric tube were taken for pH determination by pH paper, which guided antacid treatment to keep the pH equal to or greater than 5.0. Patients were monitored at two hour intervals and a total of 1,940 paired measurements were available for comparison. Comparison of values was based on a correlation of 1.5 pH units or whether or not the difference between the readings would have altered antacid therapy. Seventy-one per cent of the paired measurements were within 1.5 pH units. In only 4.3 per cent of the measurements would antacid treatment have been withheld based on the pH probe when compared with the aspiration pH. In 21 per cent of the measurements, treatment was indicated by the pH probe but not by the aspiration pH. The pH probe is a reliable, rapid method for monitoring gastric pH. It is less labor intensive than gastric aspiration and provides similar information in the patient at risk for stress gastritis.

[Comparison of 24-hour gastric pH in control subjects, in patients with duodenal ulcer and in patients with atrophic gastritis]. / Comparaison du pH gastrique de 24 heures chez des témoins, des ulcéreux duodénaux et des malades atteints de gastrite atrophique.

Twenty four hour intragastric acidity was measured by continuous recording using intragastric glass electrodes in 16 controls, 18 inactive duodenal ulcer patients and 7 patients suffering from atrophic gastritis. Medians pH for the 24h period, for the 8 AM-8 PM period, for the 8 AM-8 PM period were significantly lower in duodenal ulcer patients than in controls (1.19 vs 1.78; 1.17 vs 2.05; 1.27 vs 1.64). Median pH for these three periods were significantly higher in patients suffering from atrophic gastritis than in controls (3.90; 3.72; 3.81). In duodenal ulcer patients, 33 p 100 had medians for the 24h period higher than the lower quartile value of the control group. During the night (24h-3h) duodenal ulcer patients had median pH (1.03) significantly lower than controls (1.51). Antisecretory treatment should be directed to decrease this period of unbuffered acidity.

[How to express results of 24-hour gastric pH measurement? Choice of a mode of expression in 27 healthy subjects]. / Comment exprimer les résultats de la pH-métrie gastrique sur 24 heures? Choix d'un mode d'expression chez 27 sujets sains.

Twenty-four hour intragastric acidity was studied in 27 healthy subjects (mean age = 29 yrs) by continuous recording in standardized conditions. Data obtained were expressed according to several analytical methods as used extensively elsewhere. In our study, there was a wide discrepancy in results from one subject to another. The use of median values of pH was more appropriate than mean values to express half-hour acidity levels for 24 hours. The median value of H+ concentration is recommended as well. The median value of pH varied from 1 to 4.8 with a slight rise during the second half of the night. During the postprandial period, increase of pH values was prolonged over 2 h 30 in 50 p. 100 of subjects. Profile of pH allowed to demonstrate the distribution of pH value without excluding the extreme values. Both periodicity of pH measurement (30 or 60 min) and parameters used to quantify acidity (percentage of time or pH value at or below threshold values) did not modify results. As measured over a 24 hours period, the percentage of time (mean +/- SEM) at or below pH 1.5 and 3.5 was 54 +/- 3 p. 100 and 85 +/- 2 p. 100, respectively. Daytime and night-time profiles were similar. Mean 24 h H+ concentration (mean +/- SEM) was 47 +/- 35 mmol/l, with, once again, similarity between day and night-time values. The mean 24 h pH values underestimated true acidity with respect to median values.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of intragastric acidity in man: modern aspects, reproducibility of intragastric pH-monitoring, and pharmacodynamic results obtained with H2-receptor antagonists.

Unlike other methods for assessing intragastric pH or total acid output, the reproducibility of ambulatory pH-monitoring is excellent but is critically dependent on the electrode system and the recording device. In three double-blind randomized studies in normal volunteers the effects of different dosage regimens of roxatidine acetate were compared with placebo and ranitidine. Roxatidine acetate, 75 mg twice daily, raised median 24-h gastric pH from 1.6 to 3.2 and median nocturnal pH from 1.5 to 3.0 Roxatidine acetate, 150 mg at bedtime, raised median 24-h pH to 2.4 and nocturnal pH to 5.9. Roxatidine acetate, 150 mg at bedtime, was as effective as ranitidine, 300 mg at night, in raising median nocturnal pH. However, when drugs were taken after the evening meal, 150 mg roxatidine acetate was less potent than 300 mg ranitidine or 300 mg roxatidine acetate.

Effects of maturation and gastric acidity on gastroesophageal reflux in infants.

Using prolonged esophageal pH monitoring, we examined 42 infants referred for gastroesophageal reflux (GER) over a 16-month interval. Eighteen of these infants were also examined with intragastric pH monitoring following a standard formula meal. We found that prematurity and postcibal gastric acidity were significantly correlated with the amount of GER observed. Historical symptoms appeared to have little correlation with the amount of GER as measured by prolonged intraesophageal pH monitoring.

[Continuous intragastric pH-metry]. / Die intragastrale Langzeit-pH-Metrie.

Ambulatory intragastric pH-metry is a suitable method of assessing gastric acidity under conditions of normal daily life. A detailed profile of intragastric acidity is given which is a reproducible individual characteristic. There is a circadian rhythm of gastric acidity in which pH rises during the night and after meals. pH-metry was used to determine the effects of H2-antagonists and antacids, and the results are the basis for the clinical use of intragastric pH-metry.

Long-term ambulatory gastric pH monitoring: validation of a new method and effect of H2-antagonists.

A new ambulatory monitoring system was evaluated for long-term measurements of gastric acidity. A close correlation was observed between values indicated by the pH electrode of the system and the pH of simultaneously aspirated gastric juice, suggesting that the electrode signaled the pH of the gastric fluid content. When the pH electrode was passed via an endoscope, and its bulb was placed against the corpus mucosa, a higher acidity was recorded as compared with gastric juice. To test whether the electrodes measured mucosal pH during ordinary test conditions, the readings of pH probes with mechanically shielded bulbs that did not come into direct contact with the mucosa were compared with those of nonshielded probes in identical positions. Similar results were observed, supporting the hypothesis that nonshielded probes measured the pH of gastric contents rather than that of the mucosa. The importance of a standardized electrode position and a fixed meal schedule was demonstrated in simultaneous recordings of antral and fundic pH. Under fasting conditions, acidity was similar in both regions. After ingestion of a meal, gastric contents were more alkaline in the fundus than in the antrum. A wide range of 24-h acidity (19-83 mmol/L) was detected in 25 healthy subjects. The day-to-day reproducibility of the method as revealed in two consecutive 24-h tests was good. The effect of cimetidine and ranitidine on gastric acidity was evaluated in 9 subjects in a double-blind, double-dummy trial. Mean 24-h H+ activity was 37.4 +/- 4.6 mmol/L under placebo medication. It was lower with cimetidine, two doses of 400 mg (23.8 +/- 4.0); cimetidine, four doses of 400 mg (10.2 +/- 3.0); ranitidine, two doses of 150 mg (10.3 +/- 3.6), and two doses of 300 mg (10.0 +/- 3.5), respectively. In conclusion, ambulatory long-term pH monitoring is a suitable method to assess the physiologic pattern of gastric acidity and the effect of antisecretory drugs.

[Value and use of endoscopic pH measurement in gastroduodenal pathology]. / Interesse ed applicazioni della pH-metria perendoscopica nella patologia gastro-duodenale.

The pH values in 203 patients with various gastroduodenal pathologies were measured by means of a glass electrode inserted into the bioptic channel of the gastroscope. Analysis of the results confirms what we know of pH variations in gastric or duodenal ulcer cases and shows where perendoscopic pH measurements may be used beneficially. In particular it was found that mucous pH is not affected by H2 antagonists if these are taken more that 12 hours before the examination. Perendoscopic pH measurement appears to be a valuable tool in screening stomach lesions at risk in cases of chronic gastritis, since it facilitates the identification of atrophic or metaplastic lesions.

Continuous intragastric pH measurement in the critically ill and treatment with parenteral ranitidine.

Continuous measurement of gastric pH using a flexible pH electrode attached to a NG tube was performed in nineteen critically ill patients. The gastric pH readings correlated well with hourly intermittent pH values using indicator strips. Hypotension, physiotherapy and septicaemia was consistently associated with falls in gastric pH. A continuous infusion of Ranitidine, a H2-receptor antagonist, was titrated against the continuously measured gastric pH in an attempt to keep it above a pH of 4. This was successfully achieved in sixteen of the nineteen patients using widely variable doses of Ranitidine. The three patients whose gastric pH remained low all had severe septicaemia.