Decreases in gastric mucosal pH (pHi) are associated with splanchnic hypoxia in animals and with increased mortality in patients. In the present study we measured changes in gastric pHi with a tonometer in septic patients after a short-term infusion of dobutamine. These changes were compared with concurrent alterations in systemic O2 consumption (VO2) and arterial lactate. Twenty-one patients admitted sequentially to a medical intensive care unit with sepsis and gastric pHi < 7.32 were prospectively separated into a normal lactate group (< or = 2.2 mM; n = 10) and an elevated lactate group (> 2.2 mM; n = 11). Dobutamine HCl was infused intravenously at 5 micrograms/kg/min for approximately 3 h and then increased to 10 micrograms/kg/min. Measurements were obtained after each increase in the dose of dobutamine. Dobutamine infused at 10 micrograms/kg/min produced increases in O2 transport in both groups (p < 0.05) whereas systemic O2 consumption remained unchanged. These changes were accompanied by decreases in the arterial lactate concentration of the elevated lactate group (p < 0.01). Arterial lactate remained constant in the normal lactate group. Gastric pHi increased in both groups when dobutamine was infused at 5 micrograms/kg/min (p < 0.01), and then again at 10 micrograms/kg/min (p < 0.05). These results imply that regional tissue hypoxia, as characterized by a low gastric pHi, may be present in septic patients with normal arterial lactate concentration. Moreover, a rise in gastric pHi in response to increases in systemic O2 transport may be a better indicator of regional hypoxia in septic patients than related increases in systemic VO2.