BACKGROUND: Preservation of intestinal perfusion is considered the goal of resuscitation because derangement of gut perfusion is the major factor in multi-organ dysfunction. Gut intramucosal pH measured by tonocap, has been proven to be the sensitive monitor of gut mucosal perfusion. The effects of vasoactive agents on regional blood flow and cellular metabolism remain unclear. This study was done to examine the effects of dopamine or dobutamine on systemic hemodynamics and splanchnic perfusion assessed by gastric intramucosal pH (pHi) during resuscitation of hemorrhagic shock. METHODS: Thirty anesthetized dogs were bled to 30 40 mmHg of mean arterial pressure (MAP) and maintained at the shock state for 90 minutes. Cardiac output and arterial and mixed venous blood gas data was measured for the global assessment of circulation and oxygenation. Gastric intramucosal pH (pHi) and CO2 tension (PrCO2) and the difference of arterial and gastric intramucosal CO2 tension (CO2 gap) were measured for the assessment of splanchnic perfusion. Dogs were resuscitated with shed blood and a crystalloid solution at the maintenance dose (control group, n = 10). Dopamine (4microgram/kg/min, dopamine group, n = 10) or dobutamine (7microgram/kg/min, dobutamine group, n = 10 ) was added from the start of volume replacement and maintained for a follow-up period of 180 minutes. RESULTS: Cardiac index and global oxygen delivery and consumption were increased after resuscitation in all groups. These parameters were significantly higher in the dopamine or the dobutamine groups than in the control group (P< 0.05), and significantly higher in the dopamine group than in the dobutamine group (P< 0.05). The pHi, PrCO2 and CO2 gap were not improved from the values of shock state after volume resuscitation in the control group. The pHi, PrCO2 and CO2 gap were significantly improved from the values of shock state after resuscitation in the dopamine group (P< 0.05), but not differentfrom the control group. The pHi, PrCO2 and the CO2 gap were significantly improved from the value of shock state after resuscitation in the dobutamine group and maintained significantly higher than in the control group for the follow-up period (P< 0.05). Compared to the dopamine group, the pHi increased early and was higher in the dobutamine group (P< 0.05). CONCLUSIONS: We conclude that dobutamine is effective in improving gut mucosal oxygenation during early resuscitation of hemorrhagic shock. Dopamine has little effect on the restoration of gut mucosal oxygenation. Considering the better recovery of cardiac index and global oxygenation parameters in the dopamine group, this finding could be explained by the redistribution of cardiac output or imbalance of oxygen metabolism occuring in the dopamine group.