BACKGROUND: Norepinephrine, which is frequently administered as a vasopressor to the patients with septic shock, can decrease splanchnic and renal blood flows and aggravate splanchnic and renal ischemia. The low-dose dopamine (LDD) has been frequently combined with norepinephrine to ameliorate renal and splanchnic hypoperfusion in patients with septic shock. However, the effect of the LDD on the splanchnic and renal blood flow has not been fully elucidated. This investigation was carried out to determine the effect of the LDD on the splanchnic and renal blood flow in the patients with septic shock under the treatment of norepinephrine. METHODS: Eleven patients with septic shock were included in this study. All of them were under the norepinephrine treatment as the mean arterial pressure (MAP) was less than 70 mm Hg in spite of the adequate fluid resuscitation. With stabilization of MAP, the LDD (2 g/kg/min) was administered for two hours in each patients. Hemodynamics, gastric intramucosal pH (pHi), gastric regional PCO2 (rPCO2), rPCO2 - PaCO2, urine volume, urine sodium excretion and creatinine clearance were compared between with and without the LDD infusion. Diuretics was not used during the study period. RESULTS: Age of patients (n=11) was 64 12 and the APACHE III score was 84 17. The mortality rate of the subjects was 64%. Dosage of norepinephrine was 0.55 0.63 g/kg/min during the study period. There were no significant differences in hemodynamics (central venous pressure, cardiac output, pulmonary artery occlusion pressure, mixed venous gas), pHi, rPCO2, rPCO2 - PaCO2 depending on the concomitant infusion of the LDD. The volume of urine tended to increase (P=0.074) after concomitant LDD, but the changes in urine sodium excretion and creatinine clearance were not significantly different. CONCLUSIONS: The combined infusion of the LDD with norepinephrine did not improve splanchnic and renal blood flow in the patients with septic shock.