The purpose of this study is to find out whether perioperative fluid restriction influence on postoperative immunological function. And discuss the probable mechanism that fluid restriction regime effect on clinical data.

Perioperative fluid administration is a common therapy in clinical practice, and recent regime has a history about 50 years. Recently, clinicians found that traditional regime had some disadvantages, for example, pulmonary edema, increased cardiac load, increased body weight. And thus, perioperative fluid restriction regimen has been suggested and proved could reduce cardiopulmonary complications and mortality rates after major elective gastrointestinal surgery.

Patients were divided into two groups randomly and underwent restricted fluid regimen or traditional fluid regimen. We determined the complications and immunological function in two groups, and analyzed the relationship between complications and immunological changes. Based on this we decide the probable mechanism that perioperative fluid restriction effects on complications.

Inclusion Criteria:

• All patients(age≧65y) who was admitted for gastrointestinal cancer surgery were considered eligible if they had no life-threatening systemic disease (ASA groups 1~3)

Exclusion Criteria:

• lactation
• mental disorders
• language problems
• smoking within two weeks
• diabetes mellitus
• renal insufficiency
• disseminated cancer
• secondary cancers
• inflammatory bowel disease, or diseases hindering epidural analgesia