title: Deltoid, triceps, or both responses improve the success rate of the interscalene catheter surgical block compared with the biceps response.
abstract: BACKGROUND
  The influence of the muscular response elicited by neurostimulation on the success rate of interscalene block using a catheter (ISC) is unknown. In this investigation, we compared the success rate of ISC placement as indicated by biceps or deltoid, triceps, or both twitches.
  
  
  METHODS
  Three hundred (ASA I-II) patients presenting for elective arthroscopic rotator cuff repair were prospectively randomized to assessment by biceps (Group B) or deltoid, triceps, or both twitches (Group DT). All ISCs were placed with the aid of neurostimulation. The tip of the stimulating needle was placed after disappearance of either biceps or deltoid, triceps, or both twitches at 0.3 mA. The catheter was advanced 2-3 cm past the tip of the needle and the block was performed using 40 ml ropivacaine 0.5%. Successful block was defined as sensory block of the supraclavicular nerve and sensory and motor block involving the axillary, radial, median, and musculocutaneous nerves within 30 min.
  
  
  RESULTS
  Success rate was 98.6% in Group DT compared with 92.5% in Group B (95% confidence interval 0.01-0.11; P<0.02). Supplemental analgesics during handling of the posterior part of the shoulder capsule were needed in two patients in Group DT and seven patients in Group B. Three patients in Group B had an incomplete radial nerve distribution anaesthesia necessitating general anaesthesia. One patient in Group B had an incomplete posterior block extension of the supraclavicular nerve. No acute or late complications were observed.
  
  
  CONCLUSIONS
  Eliciting deltoid, triceps, or both twitches was associated with a higher success rate compared with eliciting biceps twitches during continuous interscalene block.
authors.affiliation: Department of Anaesthesiology, Balgrist University Hospital, Forchstrasse 340, CH-8008 Zurich, Switzerland. alain.borgeat@balgrist.ch
authors.forename: A
authors.initials: A
authors.lastname: Borgeat
authors.forename: G
authors.initials: G
authors.lastname: Ekatodramis
authors.forename: S
authors.initials: S
authors.lastname: Guzzella
authors.forename: P
authors.initials: P
authors.lastname: Ruland
authors.forename: G
authors.initials: G
authors.lastname: Votta-Velis
authors.forename: J
authors.initials: J
authors.lastname: Aguirre
mesh_terms: D000577:Amides; D000779:Anesthetics, Local; D001132:Arm / Q000294:innervation; D001917:Brachial Plexus / Q000187:drug effects*; D002404:Catheterization; D057645:Deltoid Muscle / Q000187:drug effects; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation*; D009407:Nerve Block / Q000379:methods*; D010149:Postoperative Pain / Q000517:prevention & control; D011446:Prospective Studies; D000077212:Ropivacaine; D017006:Rotator Cuff / Q000601:surgery
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine