WALANT Versus Axillary Brachial Plexus Block in Carpal Tunnel Release: a Non-inferiority Randomized Controlled Trial

Randomization will be performed using an external Interactive Web Response System. Subjects will be randomly assigned (1:1) in permuted blocks of different sizes, to have either BAX (Control group) or WALANT (Interventional group). A stratification of the randomization will be planned according to the Sex.

In the BAX group (usual technique), axillary brachial plexus block will be performed. In the WALANT group (experimental technique), local anesthesia will be performed. The Peripheral nerve blocks (PNBs) will be performed by a physician not involved in the peri-operative assessment. Care providers and outcomes assessors will be blinded to group allocation.

After obtaining venous access and placement of standard monitors, patients will be administered oxygen 2 L/min via nasal prongs. Thirty minutes before surgery, an experienced anesthesiologist will perform the regional blocks guided by ultrasound (Sonosite Export, Bothell, USA) using an ultrasound needle (Ultraplex 360°, B Braun, Melsungen, Germany) as follow:

• In the BAX group, patients will be placed in a supine position with their arm abducted to 90°. The ultrasound probe will be placed to obtain a transverse image of the axillary artery at the level of the conjoint tendon of the latissimus dorsi and teres major muscles. With an in-plane technique, a 50mm ultrasound needle (Ultraplex 360°, B Braun, Melsungen, Germany) will be advanced to achieve a spread of lidocaine (10mg/ml) around the musculocutaneous, radial, median and ulnar nerves. 30 ml of the solution will be used to achieve the BAX.
• In the WALANT group, patients will be placed in a supine position. Solution for local anesthesia will be prepared using 20 ml of lidocaine (10mg/ml) with epinephrine (0.005 mg/ml), 17 ml of saline solution and 3 ml of 8.4% sodium bicarbonate. The ultrasound probe will be placed to obtain a transverse image of the median nerve at the wrist. With an in-plane technique, a 50mm ultrasound needle (Ultraplex 360°, B Braun, Melsungen, Germany) will be advanced to achieve a spread of 5 ml of the solution posterior and then anterior to the median nerve under the annular carpal ligament. Then the ultrasound probe will be placed to obtain a longitudinal image of the median nerve at the wrist. With an in-plane technique, a 50mm ultrasound needle (Ultraplex 360°, B Braun, Melsungen, Germany) will be advanced to achieve a spread of 15 ml of the solution anterior to the median nerve towards the carpal tunnel. At last, a local infiltration with 5 ml of the solution will be performed around the surgical incision.

Upon completion of the blocks, patients will be transferred to the operating room.