Interscalene block is performed under ultrasound guidance. Linear probe is placed on the ipsilateral interscalene groove visualizing the brachial plexus located between anterior and middle scalene muscles. Using in-plane technique, nerve stimulation needle is advanced into the brachial plexus sheath, into which 25 ml of 1.5% mepivacaine is injected.

Supraclavicular block is performed under ultrasound guidance. Linear probe is placed on the ipsilateral supraclavicular fossa visualizing the brachial plexus located lateral to the subclavian artery. Using in-plane technique, nerve stimulation needle is advanced into the brachial plexus sheath, into which 25 ml of 1.5% mepivacaine is injected.

Redirection of the needle is allowed when spread of local anesthetics does not surround the brachial plexus appropriately and involuntary movement of the forearm or hand is not necessary to confirm the correct placement of the needle.

Sensory blockade of the C5 to T1 dermatomes was assessed by rating the absence of cold sensation between 100 (intact sensation) and 0 (no sensation) with an alcohol swab.

Motor blockade was evaluated by elbow and wrist extension (radial nerve), finger abduction (ulnar nerve), wrist flexion (median nerve), and elbow flexion (musculocutaneous nerve). The muscle force was rated on a scale of 0 to 6 as follows (6: normal muscle force; 5: slightly reduced muscle force; 4: greatly reduced muscle force; 3: slightly impaired mobility; 2: greatly impaired mobility; 1: near complete paralysis; 0: complete paralysis).