title: Near-infrared tracking system for epidural catheter placement: a feasibility study.
abstract: BACKGROUND
  Epidural catheters are routinely used in regional and obstetric anesthesia. The flexible catheter is advanced without imaging control into the epidural space, and coiling or kinking of the catheter may occur, compromising the effectiveness of epidural anesthesia. Potentially near-infrared (NER) light detection may help, tracking advancement of the catheter in the epidural space.
  
  
  METHODS
  Nonembalmed human cadavers donated to the University of Washington Willed Body program were placed prone. Catheters containing NER-emitting wire were introduced into the lumbar and thoracic epidural space. The progress of the emitting wire was tracked using the LumenVu NER guidance system, and the final location of the catheter was confirmed with fluoroscopy.
  
  
  RESULTS
  Total 12 attempts were made to place the catheter. In 7 cases (4 lumbar and 3 thoracic), good progression of the catheter in the epidural space was achieved with excellent visibility at low NER power levels. Maximum light intensity was registered when the catheter tip was found in the midline dorsal interlaminar position, as confirmed by fluoroscopy. The light intensity decreased while the catheter tip was traversing under the lamina. Poor progression of the catheter with negligible visibility of the tip at the highest NER level occurred in obese specimen (n = 2) or when the tip was in extraforaminal (n = 1), paramedian or paravertebral positions (n = 2).
  
  
  CONCLUSIONS
  Many variables such as obesity, paravertebral and extraforaminal catheter locations, and intervening bony structures can impede the application of NER technology for epidural catheter placements. Further optimization of the technology for clinical use is necessary.
authors.affiliation: Department of Anesthesiology & Pain Medicine and Neurological Surgery, Center for Pain Relief, University of Washington Medical Center, Seattle, WA, USA.
authors.forename: Sheila C
authors.initials: SC
authors.lastname: Chiu
authors.forename: Sandee J
authors.initials: SJ
authors.lastname: Bristow
authors.forename: Michael
authors.initials: M
authors.lastname: Gofeld
mesh_terms: D000767:Anesthesia, Epidural / Q000295:instrumentation* / Q000379:methods; D002102:Cadaver; D002404:Catheterization / Q000295:instrumentation*; D057785:Catheters; D004824:Epidural Space; D004867:Equipment Design; D005240:Feasibility Studies; D005471:Fluoroscopy; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D056888:Patient Positioning; D016684:Prone Position; D019265:Spectroscopy, Near-Infrared; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging; D014861:Washington