title: Does circumferential spread of local anaesthetic improve the success of peripheral nerve block?
abstract: BACKGROUND
  The relation between the pattern of local anaesthetic (LA) spread and the quality of peripheral nerve block is unclear.
  
  
  METHODS
  Twenty-one volunteers were randomized to receive a median nerve block with intended circumferential or intended non-circumferential spread of LA. Different predetermined volumes and needle placement techniques were used to produce the different patterns of LA spread. Volumetric, multiplanar 3D ultrasound imaging was performed to evaluate the pattern and extent of LA spread. Sensory block was assessed at predetermined intervals.
  
  
  RESULTS
  Complete circumferential spread of LA was achieved in only 67% of cases in the intended circumferential study group and in 33% of cases in the intended non-circumferential group. Block success was similar (90%) and independent of whether circumferential or non-circumferential spread of the LA was achieved. All block failures (n=4) occurred in the intended non-circumferential group with low volumes of LA. The onset of sensory block (independent of group allocation) was faster with circumferential spread of LA [median (IQR) onset time, 15 (8; 20) min] compared with non-circumferential spread of LA [median (IQR) onset time, 20 (15; 30) min]. More LA was used for circumferential blocks [median (IQR) volume of LA 2.8 (1.3; 3.6) vs 1.3 (1.1; 2.4) ml].
  
  
  CONCLUSIONS
  Even under optimal conditions, it was not possible to achieve circumferential spread of LA in all intended cases. The success of median nerve block seems to be independent of the pattern of LA spread.
  
  
  BACKGROUND
  DRKS 00003826.
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine and.
authors.forename: D
authors.initials: D
authors.lastname: Marhofer
authors.affiliation: Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China.
authors.forename: M K
authors.initials: MK
authors.lastname: Karmakar
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine and peter.marhofer@meduniwien.ac.at.
authors.forename: P
authors.initials: P
authors.lastname: Marhofer
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine and.
authors.forename: S C
authors.initials: SC
authors.lastname: Kettner
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Weber
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Zeitlinger
mesh_terms: D000293:Adolescent; D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008475:Median Nerve / Q000000981:diagnostic imaging / Q000378:metabolism*; D008619:Mepivacaine / Q000008:administration & dosage / Q000493:pharmacokinetics; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D018084:Ultrasonography, Interventional / Q000379:methods; D055815:Young Adult
chemical_list: D000779:Anesthetics, Local; D008619:Mepivacaine
keywords: anaesthetic techniques, regional; equipment, ultrasound machines; regional anaesthesia