Gastric mucosal pH during continuous nocturnal intragastric hypertonic sodium chloride infusion in a patient with hypercalcemia. Administration of hypertonic sodium chloride, 3 to 4 g per day, in the continuous intragastric infusion technique has been shown to be an effective means of lowering elevated serum calcium in patients with hypercalcemia. We evaluated the effect of hypertonic sodium chloride (3.6 g/day) on gastric mucosal pH in a patient with marked hypercalcemia (calcium = 25 mg/dL) and a non-ulcerated hyperplastic gastric polyps in the stomach. Three-day pH recording from an indwelling catheter revealed that the mean preinfusion pH was significantly (p < 0.005) higher (4.8 +/- 0.4) than that of 4.1 +/- 0.2 during the first hour of infusion. Thereafter, the pH decreased to reach 3.2 +/- 0.6 by 2 to 3 hours. This decrease in pH was significantly (p < 0.01) higher than that during the preinfusion (baseline) period. The pH then returned to the baseline level by 2 to 3 hours of continuous infusion. The mean percentage of time for pH to remain in the range 4 to 8 during the first and second hours of infusion was 34.5% +/- 13.1% and 40.0% +/- 12.2%, respectively. These data demonstrate that intragastric hypertonic sodium chloride infusion does not significantly alter gastric pH under these conditions. Because hypercalcemia, hyperparathyroidism, and certain drugs are associated with increased risk of gastric ulceration, it is necessary to be aware of the effect of hypertonic sodium chloride infusion on gastric pH. If intragastric pH remains below 4 in patients with hypercalcemia who require infusion of hypertonic sodium chloride, it may need to be discontinued or replaced by some other treatment.