The study will be proposed to all patients undergoing formarm or hand surgery under brachial plexus block. Patients will be randomized to one of two groups The first group - supraclavicular group - will receive an ultrasound-guided brachial plexus block via the supraclavicular approach, by injection of 30 ml of a mixture of ropivacaine 0.5 % + mepivacaine 1 %. The second group - retroclavicular group - will receive an ultrasound-guided brachial plexus block via the retroclavicular approach, by injection of 30 ml of a mixture of ropivacaine 0.5 % + mepivacaine 1 %. Primary outcome is success rate at 30 minutes after the injection defined as loss of sensation to pinprick in the forearm and hand. Secondary outcomes are: needling time, time to first analgesic request, postoperative opioid consumption, pain scores at 12 and 24 hours postoperatively, block-related complications, and patient satisfaction.
Patients will be randomized to one of two groups:~Supraclavicular group: supraclavicular brachial plexus block performed with the aid of ultrasound;~Retroclavicular group: retroclavicular brachial plexus block performed with the aid of ultrasound.