150 children scheduled for arm and forearm surgery underwent supraclavicle brachial plexus blocks with ropivacaine guided by ultrasound visualisation were randomly assigned to one of the five groups: Group A (perineural ropivacaine), Group B (ropivacaine plus 0.5 mcg/kg dexmedetomidine), Group C (ropivacaine plus 1 mcg/kg dexmedetomidine), Group D (ropivacaine plus 1.5mcg/kg dexmedetomidine) and Group E (ropivacaine plus 2 mcg/kg dexmedetomidine). The primary endpoint was the minimum local anesthetic concentration (MLAC), which was determined using the Dixon up-and-down method. The secondary endpoints were the duration of analgesia and sedation