Efficacy of the Ultrasound-guided Transversus Abdominis Plane Block in Open Aortic Abdominal Aneurysm Repair Surgery

Inclusion Criteria: * ASA (American Society of Anesthesiologists) physical status 1, 2 or 3 * Elective surgery for open repair of an aortic abdominal aneurysm performed in the Vascular Surgery Unit of the University Hospital of Besancon * Informed consent given * Health medical insurance affiliation Exclusion Criteria: * Poor adherence to protocol attended * Incapacity to consent * Pregnancy and/or breast feeding * Endovascular repair of aortic abdominal aneurysm * Emergent surgery of a rupture or a fissuration of aortic abdominal aneurysm * Chronic medical treatment by clopidogrel if clopidogrel not stopped 5 days before surgery at least * Chronic medical treatment by prasugrel if prasugrel not stopped 7 days before surgery at least * Chronic medical treatment by ticlopidine, inhibitors of phosphodiesterase , inhibitors of glycoprotein IIb/IIIa, adenosine triphosphate analogs or thrombin receptor antagonists * Congenital or acquired bleeding disorder * Incapacity to use patient-controlled analgesia device * Chronic opioid abuse or dependence * Chronic renal failure defined as a clearance \< 30 ml/min * Severe hepatic failure * Other contraindications to ropivacaïne (allergy, medical history of porphyria, hypovolemia) * Contraindications to acetaminophen * Contraindications to morphine