1. Demographics data;
2. Nutritional evaluation data;
3. All biochemical monitoring data during the study period;
4. All nutritional treatment data will be recorded daily during the study period, including actual calorie intake, protein intake, and the proportion of calorie/protein administered by EN and/or PN route. The nutritional treatment protocol will be decided by the attending physician, the investigator will not intervene.
5. A blood sample (5 ml) will be drawn from every patient immediately after they enroll into the study, and the metabolomics of the samples will be analyzed analysis using a combined 800 MHz 1H-NMR-UPLC-MS system. The data will then be used to establish metabolic profile baseline.
6. We will establish a sub-group that contains 20 patients (chosen from enrolled patients according to APACHE II scores: 10 patients are APACHE II scores in 21-30). We will take one blood sample daily during the whole study period. The plasma sample will be used for metabolomics analysis using an 800 MHz 1H-NMR-UPLC-MS system. And the data will be used for metabolic dynamic modeling.
7. Clinical outcomes data, which include: 1) Complications after the operation (intestinal fistula, pancreatic fistula, biliary fistula and sepsis, bleeding, nosocomial infection); 2) death event; 3) ICU-stay; 4) Length of hospitalization

Inclusion Criteria:

• age: 18-70
• patients are underwent Whipple operation or subtotal gastrectomy and ever admitted to intensive care unit (ICU) after the operation
• receive parenteral or enteral nutrition > 3 days

Exclusion Criteria:

• has metabolic disorders: diabetes, thyroid disease
• Pregnant or breastfeeding
• The presence of drug or alcohol dependence
• The presence of tuberculosis, HIV infection and other acute infectious disease
• Serious liver, kidney, heart and other vital organ failure

hospitalized adult patients