title: Fiber-optic Monitoring of Spinal Cord Hemodynamics in Experimental Aortic Occlusion.
abstract: BACKGROUND
  Spinal cord ischemia occurs frequently during thoracic aneurysm repair. Current methods based on electrophysiology techniques to detect ischemia are indirect, non-specific, and temporally slow. In this article, the authors report the testing of a spinal cord blood flow and oxygenation monitor, based on diffuse correlation and optical spectroscopies, during aortic occlusion in a sheep model.
  
  
  METHODS
  Testing was carried out in 16 Dorset sheep. Sensitivity in detecting spinal cord blood flow and oxygenation changes during aortic occlusion, pharmacologically induced hypotension and hypertension, and physiologically induced hypoxia/hypercarbia was assessed. Accuracy of the diffuse correlation spectroscopy measurements was determined via comparison with microsphere blood flow measurements. Precision was assessed through repeated measurements in response to pharmacologic interventions.
  
  
  RESULTS
  The fiber-optic probe can be placed percutaneously and is capable of continuously measuring spinal cord blood flow and oxygenation preoperatively, intraoperatively, and postoperatively. The device is sensitive to spinal cord blood flow and oxygenation changes associated with aortic occlusion, immediately detecting a decrease in blood flow (-65 ± 32%; n = 32) and blood oxygenation (-17 ± 13%, n = 11) in 100% of trials. Comparison of spinal cord blood flow measurements by the device with microsphere measurements led to a correlation of R = 0.49, P < 0.01, and the within-sheep coefficient of variation was 9.69%. Finally, diffuse correlation spectroscopy is temporally more sensitive to ischemic interventions than motor-evoked potentials.
  
  
  CONCLUSIONS
  The first-generation spinal fiber-optic monitoring device offers a novel and potentially important step forward in the monitoring of spinal cord ischemia.
authors.affiliation: From the Departments of Anesthesiology (A.S.K., M.C., T.F.F.), Surgery (T.V.B.), and Neurological Surgery (R.M.G.), Stony Brook University Medical Center, Stony Brook, New York; Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York (A.S.K., T.F.F.); Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania (R.C.M., S.S.S., A.G.Y.); and Institute of Physics, University of Campinas, Campinas, São Paulo, Brazil (R.C.M.).
authors.forename: Angela S
authors.initials: AS
authors.lastname: Kogler
authors.forename: Thomas V
authors.initials: TV
authors.lastname: Bilfinger
authors.forename: Robert M
authors.initials: RM
authors.lastname: Galler
authors.forename: Rickson C
authors.initials: RC
authors.lastname: Mesquita
authors.forename: Michael
authors.initials: M
authors.lastname: Cutrone
authors.forename: Steven S
authors.initials: SS
authors.lastname: Schenkel
authors.forename: Arjun G
authors.initials: AG
authors.lastname: Yodh
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Floyd
mesh_terms: D000818:Animals; D001011:Aorta / Q000503:physiopathology*; D004195:Disease Models, Animal; D005336:Fiber Optic Technology; D006439:Hemodynamics; D006973:Hypertension / Q000503:physiopathology; D007022:Hypotension / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D008991:Monitoring, Physiologic / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012756:Sheep; D013116:Spinal Cord / Q000503:physiopathology; D020760:Spinal Cord Ischemia / Q000175:diagnosis* / Q000503:physiopathology; D060205:Therapeutic Occlusion