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 g/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.