Postoperative pain after cardiac surgery is a risk factor for postoperative complications. In cardiac surgery, pain is more intense during the first 48 hours and disturbs the patient's capacity of coughing, deep breathing, and early mobilisation. It may be responsible for respiratory complications such as bronchial or pulmonary infection, and may also delay the patient's rehabilitation and therefore prolong the duration of in-hospital stay. A previous pilot study performed in our department showed a sensible improvement of analgesia at movement and of rehabilitation with a continuous bilaterosternal infusion of local anaesthesia [Eljezi et al.. Reg Anesth Pain Med 2012; 37:166]. Such strategy shall be tested in a subpopulation of patients at risk for respiratory complication.

Prospective, controlled, randomised, parallel, single-centre, single-blinded trial, comparing to a control (conventional care with no locoregional anaesthesia) an infusion of ropivacaine through two multihole catheters placed lateral to the sternum. In both groups, postoperative analgesia will be achieved by paracetamol plus titrated then self-administered intravenous morphine.

Inclusion Criteria:

• Scheduled cardiac surgery (aortic or mitral valve replacement, or coronary bypass surgery) with sternotomy.
• Patients will be at risk of noncardiac postoperative complications, i.e. age over 75, BMI over 30, pulmonary disease, or active smoking habit

Exclusion Criteria:

• surgery in emergency
• thoracotomy
• cardiac graft
• redo
• aortic dissection
• age over 85
• pregnancy
• patient's refusal
• minor or adult under legal protection
• psychiatric ongoing disease
• addiction to opiates
• ongoing opiate treatment
• inability to use a PCA device
• respiratory insufficiency (Vital capacity or maximal expired volume per sec. < 50% of the expected value, or mean PAP > 50 mmHg)
• cardiac failure or EF < 40% or intra-aortic balloon use
• pulmonary hypertension over 50 mmHg
• severe renal insufficiency
• history of allergy or intolerance to: morphine, acetaminophen, ropivacaine.