The study will be proposed to all patients undergoing formarm or hand surgery under axillary brachial plexus block. Patients will be randomized to one of two groups.~The first group - extrafascial injection group - will receive an ultrasound-guided supraclavicular brachial plexus block whereby the local anesthetic will be deposited at the exterior of the fascial sheath that surrounds the nerves.~The second group - intrafascial injection group - will receive an ultrasound-guided supraclavicular brachial plexus block whereby the local anesthetic will be deposited at the interior of the fascial sheath that surrounds the nerves.~All patients will receive the same type and amount of local anesthetic: 30 ml of a mixture of ropivacaine 0.5 % + mepivacaine 1 %.~The primary outcome is the rate of hemidiaphragmatic paresis 30 minutes after the block procedure, assessed with ultrasound. Secondary outcomes are: rate of hemidiaphragmatic paresis 2 hours after surgery, assessed with ultrasound, bedside spirometry before the supraclavicular block, 30 minutes after the block and 2 hours after surgery, rate of successful block 30 minutes after the block , duration of sensory and motor block, pain scores at rest and on movement at 24 h postoperatively, cumulative postoperative opioid consumption at 24 hours postoperatively and patient satisfaction with overall anesthetic management.~These outcomes are further defined in the section below.
Patients will be randomized to one of two groups:~Extrafascial injection group: Ultrasound-guided supraclavicular brachial plexus block with 2 injections of local anaesthetic, deposited at the exterior of the fascial sheath that surrounds the nerves~Intrafascial injection group: Ultrasound-guided supraclavicular brachial plexus block with 2 injections of local anaesthetic, deposited at the interior of the fascial sheath that surrounds the nerves