The subjects of study are patients undergoing upper extremity operation. All patients will be randomized into 4 groups according to the specific nerve block (SNB) of brachial plexus: group MC (musculocutaneous), group UL (ulnar), group RA (radial) and group ME (median). Patients are randomised to the four groups by random number(generated by computer) in sealed envelopes. Sample randomization will be done in four groups by random-number using sealed envelopes. Each patient will receive allocated SNB of brachial plexus (musculocutaneous, radial, ulnar, or median) followed by Axillary brachial plexus block successively using ultrasound guidance combined neurostimulation. All nerve blocks will be performed by a single dedicated anesthetist. A second investigator, who is blinded to the protocol and patient allocation, will perform the measurements.