Fully Automated Anesthesia, Analgesia and Fluid Management

Evaluate the feasibility and quality of automated anesthesia, analgesia and fluid management based on a combination of several physiological variables (bispectral index [BIS], stroke volume [SV], and stroke volume variation [SVV]) using 2 independent physiologic closed-loop systems (PCLS) in patients undergoing high risk vascular surgery.

All patients will receive total intravenous anesthesia in target controlled infusion mode using the population pharmacokinetic sets of Schnider for propofol and Minto for remifentanil to target the effect-site concentration. Infusion Toolbox 95 version 4.11 software (Free University of Brussels, Brussels, Belgium) implemented in a personal computer serving as a platform for: calculating effect-site concentrations of propofol and remifentanil; displaying effect-site concentration estimates in real time; providing a user interface that permits entry of patients' demographic data (sex, age, weight, and height) and modifications to target concentrations; controlling the propofol and remifentanil infusion pumps (Alaris Medical, Hampshire, United Kingdom); and recording calculated effect-site drug concentrations.

All patients will receive a baseline crystalloid infusion (PlasmaLyte, Baxter, Belgium) delivered by a pump at a rate of 3 mL/ kg/h (Fresenius Kabi, Belgium). Additional fluid was given using a goal-directed fluid therapy protocol guided by the cardiac output monitor (EV-1000; Edwards Lifesciences) and consisted of 100 mL boluses (Voluven, Fresenius Kabi, Germany) delivered by our PCLS (Learning Intravenous Resuscitator [LIR]). For fluid output, a Q-Core Sapphire Multi-Therapy Infusion Pump (Q-Core, Israel) was controlled by the LIR using software provided by Q-Core via a serial connection (Commands Server R.01). If hypotension occurred (defined as mean arterial pressure <20% of baseline blood pressure) and no fluid is delivered by the LIR, it will be treated by the anesthesiologist using a vasopressor drug.

In this pilot study, each closed loop also will operate independently, guided only by its own respective inputs (BIS for the propofol; SV and SVV for the fluid boluses).

The investigators will also measure analgesia using the PhysioDoloris monitoring device (MDoloris Medical Systems, Lille, France).

Inclusion criteria

• patients scheduled for high risk vascular surgery
• Patients American Society Anesthesiologist classification: 3 or 4

Exclusion criteria

• age less than 18 years,
• patients with arrhythmias like atrial fibrillation
• allergy to latex, propofol, remifentanil, morphine, muscle relaxant or any of the excipients,
• pregnant woman
• combined general and regional anesthesia,