Inclusion Criteria:  Gastric cancer patients age between 18-75 yrs;  ASA physical state I and II  Undergoing open gastrectomy  Exclusion Criteria:  With contraindications to epidural puncture or catheter placement  Chronic or acute (within 48 h) intake of psychotropic drugs, benzodiazepines, anticonvulsants, or opioids; alcoholism  Hepatic, renal, neurological or other organ dysfunctiony  Younger than 18 years or older than 75 years  Allergic to local anesthetic solutions or opioids  Received neo-adjuvant chemotherapy  Refuse to receive epidural puncture