title: Noninvasive monitoring of tissue hemoglobin using UV-VIS diffuse reflectance spectroscopy: a pilot study.
abstract: We conducted a pilot study on 10 patients undergoing general surgery to test the feasibility of diffuse reflectance spectroscopy in the visible wavelength range as a noninvasive monitoring tool for blood loss during surgery. Ratios of raw diffuse reflectance at wavelength pairs were tested as a first-pass for estimating hemoglobin concentration. Ratios can be calculated easily and rapidly with limited post-processing, and so this can be considered a near real-time monitoring device. We found the best hemoglobin correlations were when ratios at isosbestic points of oxy- and deoxyhemoglobin were used, specifically 529/500 nm. Baseline subtraction improved correlations, specifically at 520/509 nm. These results demonstrate proof-of-concept for the ability of this noninvasive device to monitor hemoglobin concentration changes due to surgical blood loss. The 529/500 nm ratio also appears to account for variations in probe pressure, as determined from measurements on two volunteers.
authors.affiliation: Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA. janelle.bender@duke.edu
authors.forename: Janelle E
authors.initials: JE
authors.lastname: Bender
authors.forename: Allan B
authors.initials: AB
authors.lastname: Shang
authors.forename: Eugene W
authors.initials: EW
authors.lastname: Moretti
authors.forename: Bing
authors.initials: B
authors.lastname: Yu
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Richards
authors.forename: Nirmala
authors.initials: N
authors.lastname: Ramanujam
mesh_terms: D015415:Biomarkers / Q000097:blood; D001774:Blood Chemical Analysis / Q000379:methods*; D016063:Blood Loss, Surgical; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005240:Feasibility Studies; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D010100:Oxygen / Q000097:blood*; D010865:Pilot Projects; D019106:Postoperative Hemorrhage / Q000097:blood* / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*
chemical_list: D015415:Biomarkers; D006454:Hemoglobins; D010100:Oxygen