title: Comparison of Outside Versus Inside Brachial Plexus Sheath Injection for Ultrasound-Guided Interscalene Nerve Blocks.
abstract: OBJECTIVE
  Ultrasound-guided interscalene brachial plexus blocks are commonly used to provide anesthesia for the shoulder and proximal upper extremity. Some reviews identify a sheath that envelops the brachial plexus as a potential tissue plane target, and current editorials in the literature highlight the need to establish precise and reproducible injection targets under ultrasound guidance. We hypothesize that an injection of a local anesthetic inside the brachial plexus sheath during ultrasound-guided interscalene nerve blocks will result in enhanced procedure success and provide a consistent tissue plane target for this approach with a reproducible and characteristic local anesthetic spread pattern.
  
  
  METHODS
  Sixty patients scheduled for shoulder surgery with a preoperative interscalene block for postoperative pain management were enrolled in this prospective randomized observer-blinded study. Each patient was randomly assigned to receive a single-shot interscalene block either inside or outside the brachial plexus sheath.
  
  
  RESULTS
  The rate of complete motor and sensory blocks of the axillary nerve territory 10 minutes after local anesthetic injection for the inside group was 70% versus 37% for the outside group (P < .05). At all measurement intervals beyond 10 minutes, however, neither group showed a statistically significant difference in complete sensory blockade. The incidence rates of transient paresthesia during needle passage were 6.7% for the outside group and 96.7% for the inside group (P < .05).
  
  
  CONCLUSIONS
  Except for faster onset, this prospective randomized trial did not find any advantages to performing an interscalene block inside the brachial plexus sheath. There was a higher incidence of transient paresthesia when injections were performed inside compared to outside the sheath.
authors.affiliation: Departments of Anesthesiology, Perioperative Medicine, and Pain Management (J.M., A.M., A.V., J.F.G., A.R.J., R.E.G.) and Orthopedics and Rehabilitation (L.K., R.E.G.), University of Miami, Miller School of Medicine, Miami, Florida USA.
authors.forename: Joni
authors.initials: J
authors.lastname: Maga
authors.affiliation: Departments of Anesthesiology, Perioperative Medicine, and Pain Management (J.M., A.M., A.V., J.F.G., A.R.J., R.E.G.) and Orthopedics and Rehabilitation (L.K., R.E.G.), University of Miami, Miller School of Medicine, Miami, Florida USA. amissair@med.miami.edu.
authors.forename: Andres
authors.initials: A
authors.lastname: Missair
authors.affiliation: Departments of Anesthesiology, Perioperative Medicine, and Pain Management (J.M., A.M., A.V., J.F.G., A.R.J., R.E.G.) and Orthopedics and Rehabilitation (L.K., R.E.G.), University of Miami, Miller School of Medicine, Miami, Florida USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Visan
authors.affiliation: Departments of Anesthesiology, Perioperative Medicine, and Pain Management (J.M., A.M., A.V., J.F.G., A.R.J., R.E.G.) and Orthopedics and Rehabilitation (L.K., R.E.G.), University of Miami, Miller School of Medicine, Miami, Florida USA.
authors.forename: Lee
authors.initials: L
authors.lastname: Kaplan
authors.affiliation: Departments of Anesthesiology, Perioperative Medicine, and Pain Management (J.M., A.M., A.V., J.F.G., A.R.J., R.E.G.) and Orthopedics and Rehabilitation (L.K., R.E.G.), University of Miami, Miller School of Medicine, Miami, Florida USA.
authors.forename: Juan F
authors.initials: JF
authors.lastname: Gutierrez
authors.affiliation: Departments of Anesthesiology, Perioperative Medicine, and Pain Management (J.M., A.M., A.V., J.F.G., A.R.J., R.E.G.) and Orthopedics and Rehabilitation (L.K., R.E.G.), University of Miami, Miller School of Medicine, Miami, Florida USA.
authors.forename: Annika R
authors.initials: AR
authors.lastname: Jain
authors.affiliation: Departments of Anesthesiology, Perioperative Medicine, and Pain Management (J.M., A.M., A.V., J.F.G., A.R.J., R.E.G.) and Orthopedics and Rehabilitation (L.K., R.E.G.), University of Miami, Miller School of Medicine, Miami, Florida USA.
authors.forename: Ralf E
authors.initials: RE
authors.lastname: Gebhard
mesh_terms: D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage*; D001917:Brachial Plexus / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007267:Injections; D008297:Male; D009407:Nerve Block / Q000379:methods*; D011446:Prospective Studies; D016037:Single-Blind Method; D018084:Ultrasonography, Interventional
chemical_list: D000779:Anesthetics, Local
keywords: brachial plexus; interscalene block; neurosonology; regional anesthesia