An Indicator of Successful Peripheral Nerve Block

After performed the block, sensory and motor block assessments will be carried out by blinded observer every 5 min after needle removal for 30 min in the regions of the radial, median, ulnar, and musculocutaneous nerves of the forearm. Skin temperature measurements will be performed from both the anesthetized side and the contralateral arm before the procedure and every 5 min for 30 min by a blinded observer. Before the block, the color changing nail polish will be applied to all hand nails of the patient. An independent observer will photograph the reaction of the nail polish (i.e. color change) in both hands immediately after application of nail polish and at two minute intervals for 30 min after performing the block. Two blinded observers were reviewed the digital photographs. They were asked to compare the colors of nail polish in both hands and to score the difference based on a three-point scale (0: absolutely no difference, 1: I am not sure, 2: indisputable difference)

Inclusion criteria

• patients who received infraclavicular brachial plexus block for elective elbow, forearm, wrist, or hand surgery
• American Society of Anesthesiologists class I, II or III

Exclusion criteria

• patients <18 years old
• >65 years old
• body mass index (BMI) <20 or >35 kg/m2
• inability to provide written informed consent
• refusal of regional anesthesia
• pregnancy
• contraindication for regional anesthesia
• peripheral neurological disease,
• Raynaud disease