The formalized expert recommendation of the French Society of Anesthesia and Intensive Care recommends guiding vascular filling by measuring the stroke volume (SV) in surgical patients considered at high risk. Vascular filling should be continued in the event of preload dependence and stopped in the event of the appearance of preload independence. The aim is to avoid vascular overload due to excessive vascular filling. The application of this recommendation has resulted in a reduction in postoperative morbidity, length of hospital stay and time to return to oral feeding. The superiority of this strategy is now being questioned and the predictive indices of response to vascular filling (static and dynamic) have many limitations. In addition, none of the cardiac output monitors are the gold standard for intraoperative use.

Through the study of artefacts, lung ultrasound has been gaining ground over the last twenty years, particularly in cardiology, nephrology and intensive care. By analogy with radiological B-lines, ultrasound B-lines result from the reverberation of ultrasound on the subpleural inter-lobular septa thickened by oedema. The Fluid Administration Limited by Lung Sonography (FALLS) protocol, described by Lichtenstein et al, is defined as the visualisation of new B lines during a vascular filling test. If a B-line appears in an area where it was not present during vascular filling, the most likely diagnosis is hydrostatic overload of the subpleural interstitial septum. This appearance of B-lines occurs at a sub-clinical stage.

The use of lung ultrasound could allow real-time assessment of vascular filling and its tolerance during the intraoperative period. The main objective of the study is to demonstrate a decrease in the incidence of postoperative complications (organ failure) (as defined by international guidelines) when using lung ultrasound-guided haemodynamic optimisation compared to standard optimisation.

Inclusion Criteria:

• Age> 18 years old
• Abdominal, orthopaedic or vascular surgery with general anaesthesia
• Patient of legal age ≥ 18 years.
• ASA score ≥ II
• Estimated duration of surgery > 2 hours
• At least two of the following comorbidities (age > 50 years, hypertension, heart disease, electrocardiogram (ECG) abnormality, acute pulmonary oedema, smoking, stroke, peripheral arterial disease, non-insulin dependent or insulin dependent diabetes, ascites, chronic renal failure)
• Signed consent.
• Affiliation to a social security scheme.

Exclusion Criteria:

• Severe untreated or unbalanced hypertension on treatment.
• Preoperative renal failure on dialysis.
• Acute heart failure.
• Acute coronary insufficiency.
• Vascular surgery with renal plasty.
• Cardiac surgery.
• Preoperative shock.
• Refusal of patient participation.
• Pregnant, parturient or breastfeeding woman.
• Patient under guardianship or private law.
• Acute respiratory distress syndrome according to the Berlin definition
• respiratory distress not fully explained by cardiac failure or increased blood volume,
• PaO2/FiO2 ratio ≤ 300 mm Hg on mechanical ventilation (invasive or non-invasive)
• Chronic respiratory failure with home oxygen therapy.
• Chronic interstitial lung disease
• Presence of an acoustic barrier (pneumothorax, subcutaneous emphysema, pleural calcifications, chest bandage, gunshot shrapnel...)
• Participation in other interventional drug research.
• Surgical fields covering the sites of investigation in lung ultrasound.