This study was stopped because of lack of posterior only major spine surgeries.

This study evaluates whether using information from a special arterial blood pressure monitor to guide how much fluid is given during surgery changes how long a patient stays in the hospital after the surgery. There is scientific evidence from using similar information from different devices that this technique might allow us to do a better job giving fluids during surgery and that this may be associated with a shorter hospital stay after surgery.

Inclusion Criteria:

• Adult patients scheduled for major spine surgery at LLUMC University Hospital will be eligible for participation in this study

Exclusion Criteria:

• age under 18yr,
• coagulopathy, significant renal or hepatic dysfunction (creatinine or liver enzymes > 50% above normal values),
• congestive heart failure,
• cardiac arrhythmias producing irregular rhythms, and patient refusal.