title: Epidural catheter penetration of human dural tissue: in vitro investigation.
abstract: BACKGROUND
  Factors contributing to subarachnoid catheter passage after epidural placement are not well understood. This study explored mechanisms that might explain its occurrence.
  
  
  METHODS
  Human cadaveric dura was mounted on a model and pressurized to physiologic levels. In a standardized fashion, a 20-gauge Portex three-port, closed end (nonflexible) tip catheter was passed through an epidural needle mounted on a micromanipulator at a 90 degree angle, attempting to penetrate dura with the catheter. Attempts then followed with a 19-gauge Arrow Flex Tip Plus single-port catheter. Subarachnoid catheter passage was compared in (1) intact dura, (2) clinically occult versus obvious epidural needle punctures, and (3) single 25-gauge Whitacre spinal needle punctures after combined spinal-epidural placement.
  
  
  RESULTS
  Neither catheter penetrated intact dura: Portex, 0 of 300 attempts (0.0000; 95% confidence interval [CI]: 0.0000, 0.0158); Arrow, 0 of 300 attempts (0.0000; 95% CI: 0.0000, 0.0158). In clinically occult epidural needle punctures, the 20-gauge Portex catheter penetrated 1 of 3 specimens in 1 of 14 attempts (0.0714; 95% CI: 0.0021, 0.3583). The 19-gauge Arrow did not pass (0 of 15 attempts, 0.0000; 95% CI: 0.0000, 0.2535). In clinically obvious epidural needle punctures, the Portex passed in 6 of 33 attempts (0.1818; 95% CI: 0.0760, 0.3608) and the Arrow passed in 1 of 35 attempts (0.0286; 95% CI: 0.0012, 0.1662). Neither catheter passed through a single 25-gauge spinal needle puncture after an uncomplicated combined spinal-epidural: Portex, 0 of 90 attempts (0.0000; 95% CI: 0.0000, 0.0510); Arrow, 0 of 90 attempts (0.0000; 95% CI: 0.0000, 0.0510).
  
  
  CONCLUSIONS
  Catheter passage is unlikely in the presence of intact dura or after an uncomplicated combined spinal-epidural. Unintentional subarachnoid passage suggests dural damage with the epidural needle.
authors.affiliation: Department of Anesthesia, Women's College Hospital Campus, Sunnybrook and Women's College Hospital, University of Toronto, Ontario, Canada. pamela.angle@sw.ca
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Angle
authors.forename: Jean E
authors.initials: JE
authors.lastname: Kronberg
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Thompson
authors.forename: James
authors.initials: J
authors.lastname: Duffin
authors.forename: Peter
authors.initials: P
authors.lastname: Faure
authors.forename: Shan
authors.initials: S
authors.lastname: Balasubramaniam
authors.forename: John Paul
authors.initials: JP
authors.lastname: Szalai
authors.forename: Susan
authors.initials: S
authors.lastname: Cromwell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002404:Catheterization / Q000295:instrumentation* / Q000379:methods*; D004824:Epidural Space / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013116:Spinal Cord / Q000473:pathology / Q000601:surgery; D013129:Spinal Puncture / Q000295:instrumentation / Q000379:methods; D013346:Subarachnoid Space / Q000473:pathology / Q000601:surgery