title: A comparison of epidural pressures and incidence of true subatmospheric epidural pressure between the mid-thoracic and low-thoracic epidural space.
abstract: BACKGROUND
  Differences in epidural pressure (EP) may influence the spread of blockade in thoracic epidural anesthesia. We evaluated if EP and the incidence of subatmospheric EP differ between the mid- and low-thoracic epidural space.
  
  
  METHODS
  Patients received an epidural catheter at the T3-5 (MID group, n = 20) or T7-10 (LOW group, n = 20) intervertebral space, respectively. The epidural space was identified using a Tuohy needle connected to a pressure transducer, after which EP was measured.
  
  
  RESULTS
  The epidural space could not be identified in three patients who were excluded from the study. EP data are presented as median value (interquartile range). Median EP was 1 mm Hg (-1 to 4.5) in the MID group, and 4 mm Hg (2-7.8) in the LOW group (P = 0.04). The incidence of an EP <or=0 mm Hg was 8 of 17 patients in the MID group and 2 of 20 patients in the LOW group (P = 0.02).
  
  
  CONCLUSIONS
  We conclude that EP is lower, and the incidence of subatmospheric EP is higher in the mid-thoracic epidural space when compared with that in the low-thoracic epidural space. However, median EP was positive in both groups. It remains to be investigated whether this pressure gradient is sufficient to influence the spread of thoracic epidural blockade.
authors.affiliation: Department of Anesthesiology, Intensive Care and Pain Management, Amphia Hospital, PO Box 90157, 4800 RL Breda, The Netherlands. avisser@amphia.nl
authors.forename: W Anton
authors.initials: WA
authors.lastname: Visser
authors.forename: Mathieu J M
authors.initials: MJ
authors.lastname: Gielen
authors.forename: Janneke L P
authors.initials: JL
authors.lastname: Giele
authors.forename: Gert J
authors.initials: GJ
authors.lastname: Scheffer
mesh_terms: D000328:Adult; D000368:Aged; D000767:Anesthesia, Epidural / Q000295:instrumentation / Q000379:methods; D001274:Atmospheric Pressure; D004824:Epidural Space / Q000502:physiology* / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D013903:Thoracic Surgery / Q000295:instrumentation / Q000379:methods; D013909:Thorax / Q000502:physiology*