Abstract: Objective:To explore the effect of thoracic epidural block on central venous oxygen saturation(ScVO₂) in elderly patients undergoing chest surgery. Methods:Forty ASA Ⅰ-Ⅱ patients undergoing esophagectomy or lobectomy were randomized to receive either general combined thoracic epidural anesthesia(group A,n=20) or pure general anesthesia (group B,n=20). In group A, thoracic 5-6 or 6-7(T_5-6 or T_6-7) vertebral space for puncture and epidural catheter was placed before general anesthesia. A test dose of 4 ml 1.5% lidocaine was given. When correct positioning of the epidural catheter was confirmed,general anesthesia in the two groups was induced with etomidate 0.2-0.3 mg/kg,fentanyl 3-4 μg/kg and syn-atracurium 0.15 mg/kg,anesthesia was maintained with 1%-3% sevoflurane and remifentanil and intermittent intravenous injection bolused of syn-atracurium. One point five percent lidocaine was continuously infused at a rate of 5-6 ml/h during operation in group A. Patients in group B were received only general anesthesia. The hemodynamics,SaO₂ and ScVO₂ in two groups pre-,intra- and after-operation were recorded. Results:Compared with group B,the hemodynamics in group A was stable. ScVO₂ in group A and group B was dropped significantly after operation(P<0.01), but the ScVO₂ in group B was droped furtherly. Conclusions:Thoracic epidural block can significantly raise ScVO₂ and depress the consumption of oxygen in patients who received chest surgery.