Risk factors and Prevention of severe Pain upon cessation of a peripheral nerve block. A prospective randomized study in ambulatory patients undergoing upper limb bone surgery under single shot axillary plexus block.

Pain in the course of upper limb bone surgery is a major source of discomfort for patients during postoperative time.

Severe post-operative pain is a risk factor for chronic pain. Use of a well-known molecule, regularly used in anesthesiology. Prospective double-blind study on 120 patients. Pain rebound upon awakening of the axillary plexus during upper limb bone surgery is a frequent phenomenon in post-operative follow-up of patients.

The anti-hyperalgesic properties of ketamine could be a benefit against this effect.

No studies have combined intravenous ketamine with localoregional anesthesia to reduce pain upon its release.

This may improve patients' post-operative comfort. The patients will be randomized in 2 groups and allocated to receive (slow intravenous injection) either 0.3 mg/kg intravenous ketamine diluted into 10mL saline or 10 mL 0.9% saline after the realization of PNB, before tourniquet set up and beginning of surgery.

Inclusion Criteria:

• any ambulatory upper limb bone surgery carried out under axillary PNB

Exclusion Criteria:

• Refusal to participate
• Contraindication to the use of ketamine
• Contraindication to regular use of postoperative analgesics like non-steroidal anti-inflammatory drugs and paracetamol
• Pregnant woman
• Diabetic patient
• Vascular patient
• Cognitive disorders
• Inability to answer perioperative questionnaires (language problem)

The local pharmacy department is in charge of unmasking the drug.