Arterial Pressure Based Cardiac Output for Goal-Directed Therapy in Abdominal Surgery

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.