The waveform plethysmographic signal can be used to establish an index for predicting fluid responsiveness (∆POP: respiratory variation of the plethysmographic waveform of pulse oximetry). This index was validated in some studies and because of its non-invasiveness it seems very interesting in anesthesia.

However, in a previous study the investigators evaluated the correlation between the results provided by this index (∆POP) and those of the reference index (∆PP: pulse pressure variation), and the obtained results were significantly lower than what had been previously described. In this study, the index was calculated from a recording of a filtered signal. This unavoidable application of a filter on anesthesia monitors could contribute to the discrepancy between the ∆POP and the ∆PP.

The realization of a new study, comparing ∆PP and ∆POP obtained from an unfiltered plethysmographic signal, should answer the ∆POP ability to be used in place of ∆PP.

Inclusion Criteria:

• Hospital patient in general surgery and digestive department
• Adult
• Digestive sus mesocolic surgery with direct abdominal approach justifying a semi-invasive hemodynamic monitoring by arterial catheterization (liver, pancreatic, gastric and duodenal surgery)
• Surgical approach by laparotomy
• Patient under general anesthesia with mechanical ventilation
• Agreeing to participate in the study after receiving information note

Exclusion Criteria:

• Known left systolic ventricular and/or diastolic failure
• Arrhythmias
• Surgery performed with thoracic approach
• Surgery by laparoscopy
• Emergency surgery
• Hypersensitivity or allergic to any of the product used for usual anesthesia, hypersensitivity to soya or egg lecithin
• Personal or familial history of malignant hyperthermia
• Severe kidney impairment (creatinin clearance <30ml/min)
• Patients who participated in the previous month to another study protocol
• Pregnant women or nursing
• Under-age

Patients who will undergo sus mesocolic surgery under general anesthesia and by direct approach, whose anesthesic management requires continuous monitoring of blood pressure (arterial catheter).