Objective: To determine if low gastric intramucosal pH is associated with impaired secretion of gastric acid after pentagastrin stimulation.
Design: Prospective study.
Setting: Intensive care unit of a university teaching hospital.
Patients: 20 patients requiring mechanical ventilation.
Interventions: All patients with a gastric luminal pH > 4 were given pentagastrin 6 micrograms/kg s.c. to stimulate gastric acid secretion and the response assessed by further measurements of gastric luminal pH.
Measurements and results: Gastric intramucosal pH (pHi) and luminal pH (pHL) were measured. Patients were divided into two groups on the basis of a low or normal pHi (A value of 7.35 was taken as the lower limit of normal). Patients (n = 6) with normal pHi (7.40 +/- 0.05 [mean +/- SD]) and a luminal pH > 4 (5.65 +/- 1.25) all had a decrease in pHL in response to pentagastrin (decrease in pHL 4.02 +/- 1.52). Of the patients (n = 7) with low pHi (7.2 +/- 0.13) and a pHL > 4 (6.51 +/- 0.48) only one responded to pentagastrin (decrease in pHL for this group 0.93 +/- 1.86). Patients with a pHL < 4 (2.4 +/- 0.71) were not given pentagastrin (n = 7).
Conclusion: Some critically ill patients with low gastric intramucosal pH appear to have an impaired ability to acidify the gastric lumen in response to pentagastrin.