Minimum Effective Volume for Selective Trunk Block

"This study adopts a Modified Narayana rule (MNR), a sequential up-and-down pharmacodynamics method (UDM) to estimate the minimum effective local anesthetic volume of 90% (MELAV90) of cases of the aforementioned local anaesthetic (LA) mixture, in order to produce the surgical anaesthesia of the whole upper extremity of the patients scheduled for upper limb surgeries. Based on the principal investigator's clinical experience, the initial volume of 21ml will be used. Depending on the success or failure of the SeTB, which is defined as the readiness for surgery at 30 minutes after the block, the volume for the next patient will be adjusted up or down by 3ml (1ml for each trunk of brachial plexus located above the clavicle). The upper dose limit of the study to minimize the potential for local anaesthetic systemic toxicity will be 30ml and the lower dose limit will be 12ml, which will be of no clinical importance."