Objective To investigate the effect of different methods of volume therapy on tissue oxygenation in elderly patients undergoing radical operation for gastrointestinal tumor.Methods Sixty ASA Ⅱ or Ⅲ patients,aged ＞ 65 yr,weighing 42 -85 kg,undergoing elective radical operation for gastrointestinal tumor,were randomized into 3 groups ( n =20 each):lactated Ringer' s solution (LR) group ( group Ⅰ ),LR + 0.6 ％ hydroxyethyl starch (HES) 130/0.4 (2 ∶ 1 ) group ( group Ⅱ ) and LR + 0.6 ％ HES 130/0.4 ( 1 ∶1 ) group ( group Ⅲ ).Anesthesia was induced with propofol,vecuronium and fentanyl and maintained with sevoflurane,remifentanil and vecuronium.The patients were mechanically ventilated after tracheal intubation.PETCO2 was maintained at 30-35 mm Hg.Transcutaneous partial pressure of oxygen (TcPO2) and transcutaneous partial pressure of carbon dioxide (TcPCO2) were measured within 5 min before fluid infusion (To ),25-30 min after beginning of fluid infusion (T1),within 5 min before skin incision (T2),within 5 min after skin incision (T3 ),within the first hour after beginning of surgery (T4),within the second hour after beginning of surgery (T5 ) and within 5 min before the end of surgery (T6 ).The average value within each time period was obtained.Blood gas analysis was performed simultaneously and PaO2 and PaCO2 were recorded.The fluid infused,urine volume,blood loss and requirement for norepinephrine,RBC and plasma were recorded during operation.The time when the patients passed the flatus,duration of stay in ICU and postoperative complications were recorded.Results There was no significant difference in TcPO2,TcPCO2,PaO2,PaCO2,the time when the patients passed the flatus,duration of stay in ICU and the incidence of postoperative complications among the three groups ( P ＞ 0.05).TcPO2 and PaO2 were significantly higher at T2-6 in the three groups and TcPCO2 was significantly lower at T3 in group Ⅲ than those at To and T1 ( P＜ 0.05 or 0.01).TcPCO2 was significantly lower at T3 than at T2 in the three groups (P ＜ 0.05).Compared with group Ⅰ,the requirement for norepinephrine was significantly lower ( P ＜ 0.05),and no significant change was found in the fluid infused,urine volume,blood loss and requirement for RBC and plasma in groups Ⅱ and Ⅲ ( P＞0.05).Conclusion When LR,LR+0.6％ HES 130/0.4 (2∶1) or LR + 0.6％ HES 130/0.4 (1∶1) is used for volume therapy,tissue oxygenation is improved,however,LR + 0.6％ HES 130/0.4 (2∶1) or LR + 0.6％ HES 130/0.4 (1∶1 ) is better in maintaining circulatory stability than LR infused alone and is more suitable for elderly patients undergoing radical operation for gastrointestinal tumor.