The Maximum Effective Needle-to-Nerve Distance for Ultrasound-Guided Interscalene Block

One of the most fundamental, 1 yet controversial, tenets of regional anesthesia practice has been the adage “no paresthesia, no anesthesia.” Implicit to this concept is the requirement for direct needle-nerve contact to achieve a successful block. The advent of ultrasound (US) guidance for peripheral nerve blockade (PNB) has enabled providers to position the needle tip purposefully as close as possible to, and even inside, the target nerve....