Liver injury is a complication of sepsis and septic liver injury has adverse impact upon the outcome. As a measurement for liver function, Plasma clearance rate of indocyanine green (PDR-ICG) always decreased during the early phase of sepsis. So the investigators hypotheses include: PDR-ICG is lower in sepsis patients than non-septic patients in ICU; PDR-ICG may be lower in abdominal sepsis patients than non-abdominal sepsis patients in ICU; PDR-ICG correlates with abdominal perfusion pressure; change of PDR-ICG in early phase correlates with change of transaminase or bilirubin in late phase of sepsis.

Liver injury is a complication of sepsis and septic liver injury has adverse impact upon the outcome. However, changes of transaminase or bilirubin are always not significant during the early phase of sepsis. As another sort of measurement of liver function, plasma clearance rate of indocyanine green (PDR-ICG) always decreased during the early phase of sepsis. So the investigators hypotheses include: PDR-ICG may be lower in sepsis patients than non-septic patients in ICU; PDR-ICG may be lower in abdominal sepsis patients than non-abdominal sepsis patients in ICU; PDR-ICG correlates with abdominal perfusion pressure; change of PDR-ICG in early phase may correlate with change of transaminase or bilirubin in late phase of sepsis. Through this study we also plan to calculate the range of abdominal perfusion pressure that can maintain normal PDR-ICG and the range of PDR-ICG that can maintain normal transaminase or bilirubin level in sepsis patients.

Inclusion Criteria:

• For control group: the patient does not match the diagnosis criteria of sepsis before the operation; the operation was done in peritoneal cavity; the patient is transferred to SICU directly from surgical room or recovery room; the patient is anticipated to stay in SICU for more than 48 hours.
• For study group: the patient matches the diagnosis criteria of sepsis; the patient is anticipated to stay in SICU for more than 48 hours.

Exclusion Criteria:

• Pregnancy
• Age < 18 years
• The infection is purely caused by virus
• Obstruction of biliary tract, or acute cholangitis, or acute liver abscess, or active hepatitis, or hyperacute/acute liver rejection occurs during study period
• Hemorrhagic shock occurs during study period
• Asthma occurs during study period
• Acute coronary syndrome occurs during study period
• Continuing peripheral circulation dysfunction leads to refractory "low quality" during PDR-ICG measurement
• Comorbidity of the bladder leads to impossibility to measure intra-abdominal pressure

Patients admitted to SICU of our clinical center