title: Trainee anaesthetist diagnosis of intraneural injection-a study comparing B-mode ultrasound with the fusion of B-mode and elastography in the soft embalmed Thiel cadaver model.
abstract: BACKGROUND
  The incidence of intraneural injection during trainee anaesthetist ultrasound guided nerve block varies between 16% in experts and up to 35% in trainees. We hypothesized that elastography, an ultrasound-based technology that presents colour images of tissue strain, had the potential to improve trainee diagnosis of intraneural injection during UGRA, when integrated with B-Mode ultrasound onto a single image.
  
  
  METHODS
  We recorded 40 median nerve blocks randomly allocated to 0.25 ml, 0.5 ml, 1 ml volumes to five sites, on both arms of two soft embalmed cadavers, using a dedicated B-Mode ultrasound and elastography transducer. We wrote software to fuse elastogram and B-Mode videos, then asked 20 trainee anaesthetists whether injection was intraneural or extraneural when seeing B-Mode videos, adjacent B-Mode and elastogram videos, fusion elastography videos or repeated B-Mode ultrasound videos.
  
  
  RESULTS
  Fusion elastography improved the diagnosis of intraneural injection compared with B-Mode ultrasound, Diagnostic Odds Ratio (DOR) (95%CI) 21.7 (14.5 - 33.3) vs DOR 7.4 (5.2 - 10.6), P < 0.001. Compared with extraneural injection, intraneural injection was identified on fusion elastography as a distinct, brighter translucent image, geometric ratio 0.33 (95%CI: 0.16 - 0.49) P < 0.001. Fusion elastography was associated with greater trainee diagnostic confidence, OR (95%CI) 1.89 (1.69 - 2.11), P < 0.001, and an improvement in reliability, Kappa 0.60 (0.55 - 0.66).
  
  
  CONCLUSIONS
  Fusion elastography improved the accuracy, reliability and confidence of trainee anaesthetist diagnosis of intraneural injection.
authors.affiliation: Department of Anaesthesia, Ninewells Hospital & Medical School, Dundee, UK.
authors.forename: S
authors.initials: S
authors.lastname: Munirama
authors.affiliation: Department of Anaesthesia, Ninewells Hospital & Medical School, Dundee, UK.
authors.forename: K
authors.initials: K
authors.lastname: Zealley
authors.affiliation: Institute of Medical Physics, Friedrich Alexander University-Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Schwab
authors.affiliation: Intensive Care Unit, Wythenshawe Hospital, South Manchester University Hospitals, Manchester, UK.
authors.forename: M
authors.initials: M
authors.lastname: Columb
authors.affiliation: Department of Bioengineering, University of Dundee, Dundee, UK.
authors.forename: G A
authors.initials: GA
authors.lastname: Corner
authors.affiliation: Centre for Anatomy and Human Identification, University of Dundee, Dundee, UK.
authors.forename: R
authors.initials: R
authors.lastname: Eisma
authors.affiliation: Institute of Academic Anaesthesia, Ninewells Hospital & Medical School, Dundee, UK g.a.mcleod@dundee.ac.uk.
authors.forename: G A
authors.initials: GA
authors.lastname: McLeod
mesh_terms: D000072077:Anesthetists / Q000193:education* / Q000706:statistics & numerical data*; D002102:Cadaver; D002983:Clinical Competence / Q000706:statistics & numerical data*; D054459:Elasticity Imaging Techniques / Q000379:methods*; D006801:Humans; D008475:Median Nerve / Q000000981:diagnostic imaging* / Q000187:drug effects; D009407:Nerve Block / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018084:Ultrasonography, Interventional / Q000379:methods*
keywords: Elastography; Regional anaesthesia; Ultrasonography 