The aim of this study is to study the analgesic efficacy of a continuous infusion of local anaesthetics for interscalene brachial plexus block after major shoulder surgery in the setting of multimodal analgesia, in order to determine whether the use of a catheter is still necessary in a contemporary practice.

The hypothesis of this study is that in contemporary practice, comprising the administration of multimodal analgesia, the continuous infusion of local anesthetic via a catheter remains superior in terms of analgesia at 24 h compared to a single-shot injection at the level of the interscalene brachial plexus after major shoulder surgery.

This prospective randomized monocentric superiority study will include two parallel groups: a SS (single-shot injection) group and a CI (continuous infusion) group.

All patients will have a preoperative ultrasound-guided interscalene brachial plexus block with 20 ml of lidocaïne 1% and epinephrine 1:100,000, followed by the insertion of a catheter. In the post-operative period, after clinical assessment of motor recovery in the operated limb (flexion of the forearm possible) in order to exclude any neurological damage of surgical origin, ropivacaine 0.5% 20 ml will be injected through the catheter. In the SS group, the catheter will be removed. In the CI group, a continuous infusion of ropivacaine 0.2% at a flow rate of 6 ml.h-1 will be running for 48h after the bolus administration of ropivacaine 0.5%.

In both groups, patients will receive during surgery multimodal analgesia inclusive of iv dexamethasone 8 mg, iv magnesium sulfate 40 mg.kg-1, iv ketorolac 30 mg, and iv acetaminophen 1000 mg, according to the current practice in our institution.

Assignment to one of these two groups will be done according to a computer-generated list of random numbers, and the sealed envelopes method will be used.

In the postoperative period, patients will be prescribed an iv pca of morphine.

Inclusion Criteria:

• patient scheduled for a major shoulder surgery (total shoulder arthroplasty or rotator cuff repair);
• ASA class 1 to 3;
• age more than 18 years old.

Exclusion Criteria:

• patient refusal or inability to understand and/or sign the inform consent
• contraindication for perineural block (allergy to local anesthetics, infection of puncture site, major coagulopathy, sensitive or motor deficiency on the operative side arm);
• chronic alcool abuse;
• chronic pain under chronic opioid treatment
• opioid drug abuse or under substitution treatment
• patients known for allergies to paracetamol, non steroidal anti inflammatory drugs, dexamethasone, sulfate magnesium, ondansetron, droperidol, and omeprazole;
• patients under chronic corticotherapy
• patients known for malignant hyperthermia;
• patients with chronic kidney failure class 3 or more;
• patients with severe pulmonary disease;
• patients with history of neck surgery or radiotherapy on the operative side;
• pregnancy.