title: Case report: limitation of local anesthetic spread during ultrasound-guided interscalene block. Description of an anatomic variant with clinical correlation.
abstract: OBJECTIVE
  The use of ultrasound (US) for localization of neural structures allows real-time visualization of anatomy; however, variability in the arrangement of structures has been observed. The impact of these variations on the performance and outcome of regional anesthetic techniques remains unclear. We discuss possible anatomic explanations and correlation with clinical observations.
  
  
  METHODS
  We report limited spread of local anesthetic observed during the performance of a US-guided interscalene block. This was associated with an anomalous vessel arising from the subclavian artery, which effectively divided the brachial plexus into 2 compartments. Spread of local anesthetic was restricted to the upper compartment around the C5 through C7 nerve roots. There was no anesthetic fluid visualized in the lower compartment. This produced a block that provided surgical anesthesia for shoulder arthroscopy as well as excellent postoperative analgesia, although the medial and distal aspects of the arm remained unaffected.
  
  
  CONCLUSIONS
  This case illustrates the ability of US to identify anatomic variations and their relevance to the performance of regional anesthetic techniques.
authors.affiliation: Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, OR 97239-3011, USA. abrahama@ohsu.edu
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Abrahams
authors.forename: Oliver
authors.initials: O
authors.lastname: Panzer
authors.forename: Arthur
authors.initials: A
authors.lastname: Atchabahian
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Horn
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Brown
mesh_terms: D000779:Anesthetics, Local / Q000493:pharmacokinetics*; D001917:Brachial Plexus / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D012782:Shoulder / Q000601:surgery*; D014463:Ultrasonography
chemical_list: D000779:Anesthetics, Local