title: Diaphragm function after interscalene brachial plexus block: a double-blind, randomized comparison of 0.25% and 0.125% bupivacaine.
abstract: BACKGROUND
  Interscalene brachial plexus block (ISBPB) provides excellent analgesia after rotator cuff surgery but is associated with diaphragm dysfunction. In this study, ISBPB with 20 mL of 0.125% or 0.25% bupivacaine were compared to assess the effect on diaphragm function, oxygen saturation, pain control, opioid requirements, and patient satisfaction.
  
  
  METHODS
  In this prospective, randomized, double-blind study, 30 adults undergoing outpatient arthroscopic rotator cuff repair were enrolled to receive ultrasound-guided interscalene brachial plexus catheter placement with 20 mL of 0.125% (n = 15) or 0.25% bupivacaine (n = 15). Diaphragm function and oxygen saturation were assessed before ISBPB placement and on discharge from the postanesthesia care unit. Postoperative pain scores, opioid requirements, and patient satisfaction were compared.
  
  
  RESULTS
  Diaphragm function and oxygen saturation were superior in the low concentration group. Absent or paradoxic motion of the diaphragm was present in 78% of the 0.25% group compared with 21% of patients in the 0.125% group (P = .008). Oxygen saturation decreased 4.3% in the 0.25% group compared with a decrease of 2.6% in the 0.125% group (P = .04). Pain scores averaged 1 of 10 in the 0.25% group and 0 of 10 in the 0.125% group (P = .02). Opioid requirements and patient satisfaction were not different between the two groups.
  
  
  CONCLUSIONS
  In this randomized, double-blind comparison of ISBPB performed with 20 mL of 0.125% or 0.25% bupivacaine, diaphragm function and oxygen saturation were superior in patients treated with more dilute bupivacaine. Furthermore, there were no clinically significant differences in pain scores, and no statistically significant differences in opioid requirements and patient satisfaction.
authors.affiliation: Department of Anesthesiology, University of Utah School of Medicine, Salt Lake City, UT, USA. elizabeth.thackeray@hsc.utah.edu
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Thackeray
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Swenson
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Gertsch
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Phillips
authors.forename: John W
authors.initials: JW
authors.lastname: Steele
authors.forename: Robert T
authors.initials: RT
authors.lastname: Burks
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Tashjian
authors.forename: Patrick E
authors.initials: PE
authors.lastname: Greis
mesh_terms: D000701:Analgesics, Opioid / Q000627:therapeutic use; D000779:Anesthetics, Local; D001182:Arthroscopy; D002045:Bupivacaine; D003964:Diaphragm / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000294:innervation; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block; D010092:Oximetry; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy*; D017060:Patient Satisfaction; D011446:Prospective Studies; D017006:Rotator Cuff / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D014463:Ultrasonography
chemical_list: D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D002045:Bupivacaine