LOW INTRAMUCOSAL PH IS ASSOCIATED WITH FAILURE TO ACIDIFY THE GASTRIC LUMEN IN RESPONSE TO PENTAGASTRIN

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 mug/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 (pH(L)) 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 pH(L) in response to pentagastrin (decrease in pH(L) 4.02 +/- 1.52). Of the patients (n = 7) with low pHi (7.2 +/- 0.13) and a pH(L) > 4 (6.51 +/- 0.48) only one responded to pentagastrin (decrase in pH(L) for this group 0.93 +/- 1.86). Patients with a pH(L) < 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.