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Cerebral oximetry monitoring using near-infrared spectroscopy during adult procedural sedation: a preliminary study
  1. Krista R Carlson1,
  2. Brian E Driver2,
  3. Rajesh Satpathy3,
  4. James R Miner2
  1. 1 Internal Medicine, US Army Brooke Army Medical Center, Fort Sam Houston, Texas, USA
  2. 2 Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota, USA
  3. 3 Department of Biostatistics, The George Washington University Milken Institute of Public Health, Washington, District of Columbia, USA
  1. Correspondence to Dr Krista R Carlson, Internal Medicine, US Army Brooke Army Medical Center, Fort Sam Houston, TX 78234, USA; krista.carlson.kc{at}


Background and objectives We sought to evaluate the effect of adult procedural sedation on cerebral oxygenation measured by near-infrared spectroscopy (rSo2 levels), and to assess whether respiratory depression occurring during procedural sedation was associated with decreases in cerebral oxygenation.

Methods We performed a prospective, observational preliminary study on a convenience sample of adult patients (>18 years) undergoing unscheduled procedural sedation in the ED from August 2017 to September 2018 at Hennepin County Medical Center in Minneapolis, Minnesota. The primary outcome measures were rSo2 values by level of sedation achieved and the incidence of cerebral hypoxaemia during procedural sedation (absolute rSo2 ≤60 or decrease ≥20% from baseline). The secondary outcome is the decrease in rSo2 during episodes of respiratory adverse events (AEs), defined by respiratory depression requiring supportive airway measures.

Results We enrolled 100 patients (53% female). The median (IQR) rSo2 values (%) by each level of sedation achieved on the Observer Assessment of Alertness and Sedation (OAAS) scale 1–5, respectively, were 74 (69–79), 74 (70–79), 74 (69–79), 75 (69–80), 72 (68–76). The incidence of cerebral hypoxaemia at any point within the sedation (absolute rSo2 <60%) was 10/100 (10%); 2 out of 10 had rSo2 reduction more than 20% from baseline value; the median (IQR) observed minimum rSo2 in these patients was 58 (56–59). We observed respiratory depression in 65 patients via standard monitoring; of these, 39 (60%) required at least one supportive airway measure, meeting the definition of a respiratory AE. During these AEs, 15% (6/39) demonstrated cerebral hypoxaemia with a median (IQR) minimum rSo2 of 58 (57–59). Four patients (4%) had cerebral hypoxaemia without a respiratory AE.

Conclusion Cerebral oximetry may represent a useful tool for procedural sedation safety research to detect potential subclinical changes that may be associated with risk, but appears neither sensitive nor specific for routine use in clinical practice.

  • anaesthesia
  • emergency department
  • respiratory

Data availability statement

Data are available upon reasonable request.

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Data availability statement

Data are available upon reasonable request.

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  • Handling editor Ellen J Weber

  • Presented at This was presented at the American College of Emergency Physicians Scientific Assembly, San Diego, California, USA, October, 2018.

  • Contributors KRC, BED and JRM conceived and designed the study. KRC, BED and RS contributed to data collection and monitoring. RS performed the data analysis. KRC drafted the initial manuscript and made final editorial decisions; all authors contributed substantially to its revision. JRM is the author acting as guarantor.

  • Funding This study has been supported in part by a grant from the Emergency Medicine Foundation and the Society for Academic Emergency Medicine Foundation (no award/grant number).

  • Disclaimer The view(s) expressed herein are those of the author(s) and do not reflect the official policy or position of Brooke Army Medical Center, the U.S. Army Medical Department, the U.S. Army Office of the Surgeon General, the Department of the Army, the Department of the Air Force and Department of Defense or the U.S. Government.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.