Ultrasound guidance can reduce the required local anesthetic volume for successful peripheral nerve block.

The aim of the study is to determine the minimum volume of local anesthetic to achieve an ultrasound-guided median nerve block with a dextrose 5% hydrodissection approach.

Inclusion Criteria:

• aged 18 years from 18 to 80 years with an ASA (American Society of Anesthesiologists) physical status I-II
• elective hand ambulatory surgery with a maximum duration of 30 minutes involving the median nerve and performed with elbow nerve blocks

Exclusion Criteria:

• pregnant or lactating women,
• contra-indication to regional anesthesia
• diabetes mellitus,
• effective anticoagulation or antiplatelet therapy, laboratory evidence of abnormal bleeding
• neurological disease ( including carpal tunnel syndrome or neuromuscular disease detected by preoperative neurological examination in the median nerve)
• infection at the puncture site
• contra-indication to the administration of lidocaine, notably allergy
• contra-indication to the administration of lidocaine with epinephrine
• not speaking French

Exclusion from the study:

• patient having an intraneural injection of the median nerve defined by swelling appearance are excluded from analysis