The decision to give fluids or not should not be taken lightly. Indeed, excessive or insufficient fluid administration is associated with increased morbidity and mortality. Prediction of fluid responsiveness relies on the use of a hemodynamic variable to determine how likely a patient is going to respond to a fluid bolus with a significant increase in their cardiac output or stroke volume. Depending on the response to fluids, patients are either responders or non-responders.

Today, we have many techniques to predict fluid responsiveness. However, almost all require the use of an advanced hemodynamic monitoring device.

Predicting fluid responsiveness is important in the operating room in order to avoid unnecessary fluid administration. Over the last 15 years, a number of dynamic tests have been developed which are based on the principle of inducing short-term changes in cardiac preload, using heart-lung interactions, the passive leg raise or by the infusion of small volumes of fluid, and to observe the resulting effect on cardiac output or stroke volume. Pulse pressure and stroke volume variations were first developed, but they are reliable only under strict conditions. The variations in vena caval diameters share many limitations of pulse pressure variations. The passive leg-raising test is now supported by solid evidence and is more frequently used but not practical in the operating room. More recently, the end-expiratory occlusion test has also been described, which is easily performed in ventilated patients. Unlike the traditional fluid challenge, these dynamic tests do not lead to fluid overload. The dynamic tests require the insertion of an arterial catheter linked to an advanced cardiac output monitoring device which is costly and not applicable in lower risk patients without an arterial line.

In the operating room, it is recommended to use alveolar recruitment maneuvers, consisting in the transient administration of higher pressure levels, allowing to re-ventilate certain pulmonary territories by re-expanding alveoli that would have collapsed under mechanical ventilation. In daily practice, it is generally accepted that a patient presenting a significant fall in stroke volume or mean arterial pressure during an alveolar recruitment maneuver is preload dependent, but the scientific evidence in the literature remains insufficient to date. A previous study has also demonstrated the ability to predict fluid responsiveness via analysis of central venous pressure during a recruitment maneuver. By extrapolation, we would like to evaluate the capacity of peripheral venous pressure to predict this fluid responsiveness.

Inclusion Criteria:

• Adult patients
• Patients scheduled for a high-risk abdominal surgery
• Patients equipped with an arterial line connected to an cardiac output hemodynamic monitoring device ( Flotrac, EV1000, Edwards Lifesciences, Irvine, USA)
• Patients in whom a recrutment maneuver is planned as per standard of care

Exclusion Criteria:

• Arythmia ( atrial fibrillation)
• Right ventricular dysfunction

Patients scheduled for a high-risk abdominal surgery ( liver resection and pancreatectomy)