Selective Trunk Block: A Prospective Non-Randomized Study to Evaluate Block Dynamics, Effects on Ipsilateral Hemidiaphragmatic (Phrenic Nerve) Function and Efficacy for Upper Extremity Surgery

Brachial plexus block (BPB) is frequently used as the sole anesthetic technique for upper extremity surgery. The choice of technique often depends on the site of surgery because the extent of sensory-motor blockade after a BPB varies with the technique used. The investigator is not aware of any single BPB technique described to date that can consistently produce surgical anesthesia of the whole ipsilateral upper extremity (shoulder to fingers). However, occasionally surgery entails that the whole upper extremity is anesthetized, i.e. from the shoulder to the elbow, or even the forearm, wrist or hands. This clinical challenge has been addressed previously using a combination of BPB (hybrid) techniques. The investigator has recently demonstrated that it is feasible to accurately identify majority of the individual components of the brachial plexus above the clavicle, including the three trunks, using ultrasound imaging. Since majority of the innervation of the upper extremity, i.e. shoulder, arm, elbow, forearm, wrist and hand, originates from or pass through the three trunks of the brachial plexus, the investigator hypothesized that selectively blocking the upper, middle, and inferior trunks of the brachial plexus will produce surgical anesthesia of the whole ipsilateral upper extremity, except for the area innervated by the intercostobrachial nerve (T2 - medial aspect of the upper arm). The investigator refers this novel technique as "selective trunk block" (SeTB). Currently there are no published data on block dynamics, safety or efficacy of SeTB. In addition, there may be a potential advantage that phrenic nerve can be spared, so this blockade will not affect the respiratory function as it is common to see phrenic nerve palsy after interscalene BPB (100%) and supraclavicular BPB (50-67%). This study is a continuation of a previously approved study with title "Selective Trunk Brachial Plexus Block: A Prospective Non-Randomized Study of Intervention" [NCT04510259] after the amendment (study title, protocol and increased sample size) was rejected by local IRB and suggested to submit as a new protocol. The aim of this study is to assess a novel brachial plexus block technique, the selective trunk block (SeTB), and provide preliminary clinical evidence of its effectiveness in producing surgical anesthesia of the whole ipsilateral upper extremity.