title: Utility of prepuncture ultrasound for localization of the thoracic epidural space.
abstract: BACKGROUND
  Ultrasound has been shown to facilitate accurate identification of the intervertebral level and to predict skin-to-epidural depth in the lumbar epidural space with reliable precision. We hypothesized that we could accurately predict the skin-to-epidural depth and the intervertebral level in the thoracic spine with the use of ultrasound.
  
  
  METHODS
  Twenty patients presenting for thoracic surgery were included in a feasibility study. The skin-to-epidural depth was measured using prepuncture ultrasound in the paramedian window, and the predicted depth was compared with the actual needle depth and the depth as measured by computed tomography. In addition, the intervertebral levels were identified by ultrasound using the "counting up" method, and the results were compared with the levels identified by anesthesiologists.
  
  
  RESULTS
  The ultrasound-based depth measurements displayed a bias of 3.21 mm with 95% limits of agreement from -7.47 to 13.9 mm compared with the clinically determined needle depth. The intervertebral levels identified by the anesthesiologists and the sonographer matched in only 40% of cases.
  
  
  CONCLUSIONS
  Ultrasound-based measurements of skin-to-epidural depth show acceptable agreement with the actual depth observed during epidural catheterization; however, the limits of agreement are wide, which restricts the predictive value of ultrasound-based measurements. Further study is required to delineate the role of ultrasound in thoracic epidural catheterizations.
authors.affiliation: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Abtin
authors.initials: A
authors.lastname: Rasoulian
authors.forename: Jens
authors.initials: J
authors.lastname: Lohser
authors.forename: Mohammad
authors.initials: M
authors.lastname: Najafi
authors.forename: Hedyeh
authors.initials: H
authors.lastname: Rafii-Tari
authors.forename: Denis
authors.initials: D
authors.lastname: Tran
authors.forename: Allaudin A
authors.initials: AA
authors.lastname: Kamani
authors.forename: Victoria A
authors.initials: VA
authors.lastname: Lessoway
authors.forename: Purang
authors.initials: P
authors.lastname: Abolmaesumi
authors.forename: Robert N
authors.initials: RN
authors.lastname: Rohling
mesh_terms: D000328:Adult; D000368:Aged; D000767:Anesthesia, Epidural / Q000379:methods*; D004824:Epidural Space / Q000000981:diagnostic imaging*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019616:Thoracic Surgical Procedures / Q000379:methods*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography