Objective To investigate the effectiveness of using a medium molecular weight hydroxyethyl starch solution (HES) administered as a replacement for estimated blood loss (EBL) during cytoreductive surgery for ovarian cancer on splanchnic oxygenation Methods Forty two patients undergoing cytoreductive surgery for ovarian cancer were enrolled in this prospective randomized study As soon as the EBL exceeded 10% but was less than 20% of the estimated blood volume, the patients were randomly assigned to receive either a volume of lactated Ringer’s solution (LRS) equal to three times the EBL (LRS group, n=22) or a volume of 6% HES equal to the EBL (HES group, n=20) Tissue oxygenation was assessed indirectly by measuring tonometric parameters, including the difference between gastric intramucosal PsCO 2 and arterial PaCO 2 (Ps a CO 2 gap), gastric intramucosal pH (pHi) and arterial lactate acid concentration at 30 min after induction of anesthesia (baseline value), 1 hour and 2 hours after skin incision, and at the end of surgery Results At the end of surgery,the Ps a CO 2 gap in the HES group (8 7±1 6 mmHg) was significantly lower than that of the LRS group (18 74±4 4 mmHg, P <0 01), while the pHi (7 30±0 05 mmHg) in the HES group was significantly higher than that of the LRS group (7 21±0 07 mmHg, P <0 01) There was no significant difference between the two groups in terms of arterial lactate acid concentration Conclusion In patients undergoing major surgery with relatively large blood losses, volume resuscitation with medium molecular weight hydroxyethyl starch solution may improve splanchnic blood flow and tissue oxygenation Objective To investigate the effectiveness of using a medium molecular weight hydroxyethyl starch solution (HES) administered as a replacement blood loss (EBL) during cytoreductive surgery for ovarian cancer on splanchnic oxygenation Methods Forty two patients undergoing cytoreductive surgery for ovarian cancer were enrolled in this prospective randomized study As soon as the EBL exceeded 10% but was less than 20% of the estimated blood volume, the patients were randomly assigned to receive either a volume of lactated Ringer’s solution (LRS) equal to three times the EBL (LRS group , n = 22) or a volume of 6% HES equal to the EBL (HES group, n = 20) Tissue oxygenation was demonstrated indirectly by measuring tonometric parameters, including the difference between gastric intramucosal PsCO 2 and arterial PaCO 2 2 gap), gastric intramucosal pH (pHi) and arterial lactate acid concentration at 30 min after induction of anesthesia (baseline value), 1 hour and 2 hou rs after skin incision, and at the end of surgery Results At the end of surgery, the Ps a CO 2 gap in the HES group (8 7 ± 1 6 mmHg) was significantly lower than that of the LRS group (18 74 ± 4 4 mmHg, P <0.01) while the pHi (7 30 ± 0 05 mmHg) in the HES group was significantly higher than that of the LRS group (7 21 ± 0 07 mmHg, P <0.01) There was no significant difference between the two groups in terms of arterial lactate acid concentration Conclusion In patients undergoing major surgery with relatively large blood losses, volume resuscitation with medium molecular weight hydroxyethyl starch solution may improve splanchnic blood flow and tissue oxygenation