title: Minimum effective volume of lidocaine for ultrasound-guided infraclavicular block.
abstract: BACKGROUND
  The aim of this study was to determine the minimum effective volume of lidocaine 1.5% with epinephrine 5 μg/mL in 90% of patients (MEV(90)) for single-injection ultrasound-guided infraclavicular block (ICB).
  
  
  METHODS
  Using an in-plane technique, a single-injection ultrasound-guided ICB was performed: a 17-gauge, 8-cm Tuohy needle was advanced until the tip was located dorsal to the axillary artery. Volume assignment was carried out using a biased coin design up-and-down sequential method, where the volume of local anesthetic administered to each patient depended on the response of the previous one. In case of failure, the next subject received a higher volume (defined as the previous volume with an increment of 2.5 mL). If the previous patient had a successful block, the next subject was randomized to a lower volume (defined as the previous volume with a decrement of 2.5 mL), with a probability of b=0.11, or the same volume, with a probability of 1-b=0.89. Lidocaine 1.5% with epinephrine 5 μg/mL was used in all subjects. Success was defined, at 30 mins, as a minimal score of 14 of 16 points using a composite scale encompassing sensory and motor block. Patients undergoing surgery of the elbow, forearm, wrist, or hand were prospectively enrolled until 45 successful blocks were obtained.
  
  
  RESULTS
  Fifty-five patients were included in the study. Using isotonic regression and bootstrap confidence interval (CI), the MEV(90) for single-injection ultrasound-guided ICB was estimated to be 35 mL (95% CI, 30-37.5 mL). The probability of a successful response at 35 mL was estimated to be 0.91 (95% CI, 0.8-1.0). All patients with a minimal composite score of 14 points at 30 mins achieved surgical anesthesia intraoperatively.
  
  
  CONCLUSIONS
  For single-injection ultrasound-guided ICB, the MEV(90) of lidocaine 1.5% with epinephrine 5 μg/mL is 35 mL. Further dose-finding studies are required for other concentrations of lidocaine, other local anesthetic agents as well as techniques involving multiple injections, a more medial approach to ICB, or precise location of all 3 cords of the brachial plexus.
authors.affiliation: Department of Anesthesia, Montreal General Hospital, Montreal, Quebec, Canada. de_tran@hotmail.com
authors.forename: De Q H
authors.initials: DQ
authors.lastname: Tran
authors.forename: Shubada
authors.initials: S
authors.lastname: Dugani
authors.forename: Alina
authors.initials: A
authors.lastname: Dyachenko
authors.forename: José A
authors.initials: JA
authors.lastname: Correa
authors.forename: Roderick J
authors.initials: RJ
authors.lastname: Finlayson
mesh_terms: D000328:Adult; D001917:Brachial Plexus / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D010149:Postoperative Pain / Q000503:physiopathology / Q000517:prevention & control; D018084:Ultrasonography, Interventional / Q000379:methods*; D055815:Young Adult
chemical_list: D008012:Lidocaine