• The primary endpoint of the study is postoperative renal function, as determined by measurement of the glomerular filtration rate. [ Time Frame: 6 month ]
  

• Total fluid requirements (type and volume); Drug requirement (type and volume); Other organ function (myocardial function, liver function, endothelial function, degree of inflammation) [ Time Frame: 6 month ]
  

Inclusion Criteria:

• Patient is scheduled for elective major abdominal surgery and has two or more risk factors according to the Lee classification scheme.
• Patient can sign informed consent before surgery.
• Patient is able to comply with the study procedure.
• Patient must require an indwelling radial or a femoral artery catheter.
• Patient must be 20 years old or older.
• Patient must be 40kg or heavier.
• Patients height and weight can be accurately obtained prior to study start.

Exclusion Criteria:

• Emergency surgery.
• Patients with aortic or mitral valve regurgitation.
• Renal insufficiency requiring hemodialysis.
• Liver dysfunction (alanine/aspartate aminotransferase >40 U/L).
• Patient with contraindications for the placement of radial, femoral or other arterial cannulae.
• Patient being treated with an intraaortic balloon pump.
• Female patients with a known pregnancy.
• Patient is currently participating in an investigational drug or another device study that has not completed the primary endpoint or that clinically interferes with the study endpoints.