title: Optical detection of vascular penetration during nerve blocks:  an in vivo human study.
abstract: OBJECTIVE
  Complications resulting from vascular penetration during nerve blocks are rare but potentially devastating events that can occur despite meticulous technique. In this in vivo human pilot study, we investigated the potential for detecting vascular penetration with optical reflectance spectroscopy during blocks of the sympathetic chain and the communicating ramus at lumbar levels.
  
  
  METHODS
  A custom-designed needle stylet with integrated optical fibers was used in combination with a commercial needle shaft. The needle stylet was connected to a console that delivered broadband light to tissue and spectrally resolved light that was scattered near the stylet tip. A total of 18 insertions were performed on 10 patients; testing for vascular penetration at the nerve target region was performed with aspiration and with radio-opaque contrast injections, visualized fluoroscopically. Optical absorption by hemoglobin was quantified with a blood parameter that was calculated from each spectrum. The blood parameter provided a measure of the difference between spectra acquired from the nerve target region and reference spectra acquired from blood extracted from a volunteer.
  
  
  RESULTS
  In 2 insertions, vascular penetration was detected. Pronounced optical absorption by hemoglobin was observed to be associated with both of these events and absent in all other cases. The difference between the blood parameters obtained when vascular penetration was detected, and all other blood parameters were statistically significant (P = 0.006), with a diagnostic odds ratio of 35.4 (confidence interval, 2.21 to ∞).
  
  
  CONCLUSIONS
  The results from this study suggest that optical spectroscopy has the potential to detect intravascular needle placement, which may in turn increase the safety of nerve blocks.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Maastricht University Medical Center, Maastricht, The Netherlands. a.balthasar@gmx.de
authors.forename: Andrea
authors.initials: A
authors.lastname: Balthasar
authors.forename: Adrien E
authors.initials: AE
authors.lastname: Desjardins
authors.forename: Marjolein
authors.initials: M
authors.lastname: van der Voort
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Lucassen
authors.forename: Stefan
authors.initials: S
authors.lastname: Roggeveen
authors.forename: Ke
authors.initials: K
authors.lastname: Wang
authors.forename: Walter
authors.initials: W
authors.lastname: Bierhoff
authors.forename: Alfons G H
authors.initials: AG
authors.lastname: Kessels
authors.forename: Micha
authors.initials: M
authors.lastname: Sommer
authors.forename: Maarten
authors.initials: M
authors.lastname: van Kleef
mesh_terms: D000328:Adult; D000368:Aged; D001340:Autonomic Nerve Block / Q000009:adverse effects*; D015415:Biomarkers / Q000032:analysis; D003287:Contrast Media; D004867:Equipment Design; D005336:Fiber Optic Technology; D005471:Fluoroscopy; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007267:Injections; D008875:Middle Aged; D009339:Needles; D016602:Needlestick Injuries / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D009426:Netherlands; D055100:Optical Fibers; D011237:Predictive Value of Tests; D013057:Spectrum Analysis; D013396:Suction; D057772:Vascular System Injuries / Q000097:blood / Q000175:diagnosis* / Q000209:etiology
chemical_list: D015415:Biomarkers; D003287:Contrast Media; D006454:Hemoglobins