EFFECT OF DOBUTAMINE ON OXYGEN-CONSUMPTION AND GASTRIC-MUCOSAL PH IN SEPTIC PATIENTS

Decreases in gastric mucosal pH (pH(i)) are associated with splanchnic hypoxia in animals and with increased mortality in patients. In the present study we measured changes in gastric pH(i) with a tonometer in septic patients after a short-term infusion of dobutamine. These changes were compared with concurrent alterations in systemic O-2 consumption (VO2) and arterial lactate. Twenty-one patients admitted sequentially to a medical intensive care unit with sepsis and gastric pH(i) < 7.32 were prospectively separated into a normal lactate group (less than or equal to 2.2 mM; n = 10) and an elevated lactate group (> 2.2 mM; n = 11). Dobutamine HCI was infused intravenously at 5 mu g/kg/min for approximately 3 h and then increased to 10 mu g/kg/min. Measurements were obtained after each increase in the dose of dobutamine. Dobutamine infused at 10 mu g/kg/min produced increases in O-2 transport in both groups (p < 0.05) whereas systemic O-2 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 pH(i) increased in both groups when dobutamine was infused at 5 mu g/kg/min (p < 0.01), and then again at 10 mu g/kg/min (p < 0.05). These results imply that regional tissue hypoxia, as characterized by a low gastric pH(i), may be present in septic patients with normal arterial lactate concentration. Moreover, a rise in gastric pH(i) in response to increases in systemic O-2 transport may be a better indicator of regional hypoxia in septic patients than related increases in systemic VO2.