BACKGROUND Portal hypertension (PHT) with upper gastrointestinal hemorrhage as its chief complication is a very common disease with great harm to humans. The effects of infusion volume, speed, and type on hemodynamics in case of cirrhosis, PHT esophageal variceal bleeding, and their mechanism should be clarified. This study was designed to assess the effects of different infusion volumes on hemodynamics of PHT canines after hemorrhagic shock (HS). METHODS PHT canine models were made by chronic embolization via coarctating half of the main portal vein with silk suture. Two weeks later, the models were subjected to hemorrhagic shock by quick femoral artery venesection. The canines were divided into two groups to resuscitate: one to receive a large volume of infusion (n=6) (large volume infusion group) and the other to receive a small volume of infusion (n=6) (small volume infusion group). Hemodynamic indexes of PHT canines after HS and infusion were observed closely. RESULTS The PHT canines showed a series of hemodynamical changes in hemorrhagic shock stage, which aggravated hemodynamical disorder in PHT. After quick infusion, mean arterial pressure (MAP), inferior vena cava pressure (IVCP), portal venous pressure (PVP), portal vein pressure gradient (PVPG), portal vein blood flow (PVBF), hepatic artery blood flow (HABF) and hepatic blood flow (HBF) increased significantly. These indexes in the large volume infusion group were higher than those in the small volume infusion group. Portal vascular resistance (PVR), splanchnic vascular resistance (SVR), hepatic arterial resistance (HAR) decreased significantly, but PVP, PVPG, PVBF, HABF and HBF showed a rebounding increase above the baseline values in the large volume infusion group. The changes of PVP, PVPG, PVBF, HABF and HBF were in parallel with those of MAP and inferior vena cava pressure (IVCP), without a rebounding increase in the small volume infusion group. In the large volume infusion group PVPG increased earlier and more significantly than did PVP; moreover PVPG exceeded the baseline by 13%, making the possibility of rebleeding great. In the small volume infusion group, PVPG was lower than the baseline by more than 22%, indicating a small possibility of rebleeding. SVR and HAR were lower in the large volume infusion group. PVP, PVPG, PVBF, HABF and HBF were positively correlated with accumulated volume of vein infusion. PVR showed a positive correlation with accumulated volume of vein infusion in the small volume infusion group. HAR was negatively correlated with accumulated volume of vein infusion in the large volume infusion group. CONCLUSIONS PHT canines after HS, resuscitated by vein infusion, may show a rebounding increase of PVP, PVPG, PVBF, HABF and HBF above the baseline values in the large volume infusion group but not in the small volume infusion group. A large volume infusion causes PVP, PVPG, PVBF, HABF and HBF to increase higher than does a small volume infusion.