Gastric intramucosal acidosis in mechanically ventilated patients:: Role of mucosal blood flow

Objective: To investigate whether gastric intramucosal acidosis is associated with a decreased gastric mucosal blood flow in mechanically ventilated patients. Design: Prospective, clinical investigation. Setting: University hospital intensive care unit. Patients: Seventeen mechanically ventilated patients with stable hemodynamic status. Interventions: Gastric tonometry and endoscopic assessment of mucosal blood flow, Measurements and Main Results: Six patients had gastric intramucosal acidosis (intramucosal pH [pHi] of 7.24 +/- 0.06), whereas the remaining 11 patients had pHi values within the normal range (7.44 +/- 0.01), No differences were found between intramucosal acidotic and nonacidotic patients with respect to their general and hemodynamic characteristics. Patients with intramucosal acidosis had a lower gastric mucosal blood flow, as assessed by laser-Doppler flowmetry, than nonacidotic patients (1.4 +/- 0.1 vs, 2.1 +/- 0.2 volts, respectively; p<.05), Reflectance spectrophotometry disclosed that patients with low gastric pHi had also a significantly (p < .05) lower hemoglobin content index (61 +/- 4 arbitrary units) than patients with normal pHi (81 +/- 3 arbitrary units), whereas oxygen saturation index was similar for both groups. Conclusion: Our results support the hypothesis that gastric mucosal hypoperfusion underlies the development of intramucosal acidosis in mechanically ventilated patients.