Minimum Effective Local Anesthetic Volume for Ultrasound Guided Superior 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% (MELVA90) of cases of the aforementioned local anesthetic (LA), in order to produce the surgical anesthesia of the patients scheduled for shoulder surgeries. Based on the principal investigator's clinical experience, the initial volume of 8ml will be used. Depending on the success or failure of the superior trunk block, 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 2ml. The upper dose limit of the study to minimize the potential for local anesthetic systemic toxicity will be 16ml and the lower dose limit will be 4ml, which will be of no clinical importance."