 Three hundred and twenty patients undergoing elective hand surgery under axillary brachial plexus block will be enrolled into this prospective, randomized, observer-blinded non inferiority trial. Using a computer-generated sequence of random numbers and sealed envelope technique, the patients included will randomly be allocated to receive either single or double injection ultrasound-guided axillary block. The block will be performed with the in-plane technique using a 22 gauge, 50 mm needle and a high frequency linear probe. 