OBJECTIVE: In hypovolemic patients with sepsis syndrome, to determine the effects of colloid volume infusion using 10% pentastarch on abnormal gastric tonometer measurements (gastric intramucosal CO2 tension, gastric intramucosal-arterial PCO2 gradient, and gastric intramucosal pH [pHi]) and on cardiac index, global oxygen delivery, and hemoglobin. DESIGN: Prospective prepost intervention study. SETTING: Tertiary care, university-affiliated 15-bed general systems intensive care unit. PATIENTS: Patients were studied who had sepsis syndrome, who had pulmonary arterial catheters in place, who were hypovolemic (pulmonary arterial occlusion pressure [PAOP] <15 mm Hg), and who had a gastric arterial PCO2 gradient >10 mm Hg. INTERVENTIONS: Baseline measurements of gastric intramucosal CO2 tension, gastric intramucosal-arterial PCO2 gradient, and pHi, as well as arterial lactate, pulmonary arterial occlusion, central venous and systemic arterial pressures, thermodilution cardiac output, and temperature. Boluses of 500 mL pentastarch were administered to a total of 1,000 mL or until PAOP was >18 mm Hg. Measurements were repeated at 30 mins and 120 mins postinfusion of pentastarch. MAIN RESULTS: Volume infusion using pentastarch did not change gastric PCO2, gastric-arterial PCO2 gradient, or pHi. Volume expansion with pentastarch significantly increased cardiac index, global oxygen delivery, and PAOP. Administration of pentastarch decreased hemoglobin and arterial lactate at 30 mins but not at 120 mins. CONCLUSIONS: Volume expansion using a colloidal solution of 10% pentastarch does not change abnormal intramucosal CO2 tension, gastric-arterial PCO2 gradient, or pHi in critically ill hypovolemic patients who have sepsis syndrome despite increasing cardiac index, oxygen delivery, and pulmonary artery occlusion pressure.