This study will compare a group of patients managed with a manual GDFT protocol (using the EV1000 monitoring device; Edwards Life sciences, Irvine, USA) to a group of patients managed using a novel real time clinical decision support system for goal directed fluid therapy (GDFT) guidance on microvascular parameters in patients undergoing major abdominal or orthopedic surgery.

Many trials have indicated that GDFT strategies may benefit high-risk surgical patients but these strategies are infrequently implemented on a day to day basis. It has also been shown that without any goal or protocol for fluid resuscitation, large inter- and intra-provider variability exist and have been correlated with marked variations in patient outcomes. Even under ideal study conditions, strict adherence to GDFT protocols is hampered by the workload and concentration required for consistent implementation.Haemodynamic monitors and protocols alone do not enable optimal fluid titration to be provided consistently to all patients - there must also be appropriate and timely interpretation and intervention.

To address this problem of consistency and protocol adherence, a novel real time clinical decision support system, "Assisted Fluid Management" (AFM), has been designed to help ease some of the workload associated with GDFT protocol implementation. The AFM system (released on the European market in March 2017) may help increase GDFT protocol adherence while leaving direction and guidance in the hands of the care providers. This system can suggest fluid bolus administration, analyse the effects of the bolus, and continually re-assess the patient for further fluid requirements.

Mean arterial pressure will be at least maintained in both groups above 65 mmHg with norepinephrine administration. Vasopressors administration is standardised in both groups (objective is a MAP of > 65 mmHg) and the only difference will be the way fluid boluses are given to the patient (following standard of care (manual protocol) of following the assisted fluid management recommandations)

A recent published study demonstrated that the implementation of the AFM for GDFT guidance resulted in a significantly longer period during surgery in a preload independent state (defined as a SVV < 13%) with a reduced total amount of fluid administered without any difference in postoperative complications.

Another recent study demonstrated that during abdominal surgery, microvascular perfusion is impaired during preload dependence (SVV >13%) and recovers after fluid administration (preload independent state)

Therefore the goal of this bicentric randomized controlled trial is to compare a manual GDFT approach (standard of care actually in the department) versus an Assisted fluid management approach (using the AFM mode) on the Microvascular flow index.

We assume that this novel clinical decision support system will allow patients to have less alterations of their microvascular parameters than patients managed under standard of care (GDFT but without the assisted fluid management mode)

Inclusion Criteria:

• All adult patients in the operating room scheduled for a major abdominal & orthopedic surgery requiring a cardiac output monitoring (EV1000).
• Written informed consent received before surgery.

Exclusion Criteria:

• Minor Patients.
• No french speaking.
• Atrial fibrillation or severe arrythmia.

All microvascular parameters will be analyzed at the end of the study by a blinded physicians (not linked to the study and not author of the future manuscript)