A study to find minimum effective volume of 0.5% ropivacaine for ultrasound guided costoclavicular block

The primary objective is to find the minimum effective volume of 0.5% ropivacaine  in 90% patients ( MEV90)  for ultrasound guided costoclavicular approach of infraclavicular brachial plexus block for which adults between 18 to 65 yrs undergoing hand wrist and elbow surgery  will be chosen , excluding the above mentioned categories . Then after preanaesthetic check up and explaining pain score to patients selected ultrasound guided block will be given prior to surgery . The volume of the drug will be based on baised coin method and up and down sequece in which volume of the drug for next patient is based on result of the previous . The initial volume will be 20 ml and based on the success of this the next volume will be 2ml lesser , this initial volume is based on the study done supraclavicular for MEV 50 which was 23 ml . After block application success will be assessed based on sensory and motor blockade scoring at the end of 30 min. The maximum volume decided is 25 ml to avoid drug toxicity . If the block fails then next patient will get 25 ml . A fixed minimum no of 20 positive responses will be chosen for our dose finding study. The final sample is estimated by simulations to be 52 plus/minus 2 .