Pain management/original research
Evaluation of Cerebral Oxygenation During Procedural Sedation in Children Using Near Infrared Spectroscopy

Presented as a poster in the annual Pediatric Academic Societies meeting, May 2008, Honolulu, HI.
https://doi.org/10.1016/j.annemergmed.2009.02.009Get rights and content

Study objective

We evaluate the utility of near infrared spectroscopy monitoring and its correlation to conventional respiratory monitors during changes in cardiorespiratory characteristics during pediatric procedural sedation.

Methods

In this prospective observational study of 100 children, cerebral oxygenation (rSO2), pulse oximetry (SpO2), and end-tidal carbon dioxide (etco2) were monitored continuously. Values were manually recorded at least every 3 minutes from baseline until 30 minutes after sedative administration, resulting in 1,515 triplicate (simultaneous near infrared spectroscopy/etco2/SpO2) measurements. Correlations between conventional monitoring characteristics (SpO2 and etco2) and rSO2 were determined, with focus during adverse cardiorespiratory events.

Results

Cerebral oxygenation remained normal in 1,483 of 1,515 measurements (97.9%). rSO2 decreased significantly during 3 of 13 hypoxic events occurring in 13 patients and during 5 of 17 hypercarbic events occurring in 8 patients, with 15 measurements of greater than 20% decrease from baseline. Cerebral oxygenation increased transiently in 88% of children. During 31 cerebral desaturation recordings, 3 hypoxic recordings (9.3%, always in combination with hypercarbia) and 5 hypercarbic recordings (15.6%) were observed, whereas in 23 (74.2%), cardiorespiratory characteristics were unchanged. There was poor correlation between rSO2 and both SpO2 and etco2, with correlation coefficients of 0.05 (95% confidence interval 0.04 to 0.07) and 0.01 (95% confidence interval –0.01 to 0.02), respectively.

Conclusion

Cerebral oxygenation as measured by near infrared spectroscopy demonstrated few significant negative changes during pediatric procedural sedation. Transient cardiorespiratory events seldom altered rSO2, with hypercarbia having a greater effect than hypoxemia. However, cerebral desaturations frequently occurred without associated cardiorespiratory changes.

Introduction

Procedural sedation is frequently performed to alleviate pain and anxiety associated with diagnostic and therapeutic procedures in children. Procedural sedation can potentially result in depression of the respiratory or cardiovascular function, with respiratory depression being the most common adverse event.1, 2, 3, 4, 5

Near infrared spectroscopy is a noninvasive technology that uses the absorption of infrared light to estimate cerebral tissue oxygenation (rSO2), similar to pulse oximetry.6, 7, 8 However, unlike conventional pulse oximetry, the near infrared spectroscopy monitor uses 2 sensors to measure light penetration to 2 different depths, which, in concert with subtraction of the pulsatile component, allows for isolation and specific measurement of tissue/venous (rather than arterial) oxygen saturations.

Several reports have compared rSO2 measured by near infrared spectroscopy with directly measured cerebral mixed venous oxygen saturations (SvO2) from either the superior vena cava or the jugular venous bulb and have consistently demonstrated good correlation (correlation coefficients 0.63 to 0.77) well within clinical relevance between the 2 measurements, especially over a wide range of oxygen saturations.6, 7 The accuracy of near infrared spectroscopy–measured cerebral saturations has also been studied and validated in children.6, 8, 9, 10, 11 Subsequently, near infrared spectroscopy has become increasingly used during cardiac and neurosurgical procedures,12, 13, 14, 15, 16, 17 and positive effects on neurologic outcome have been described, including decreased incidence of stroke and overall lower incidence of major organ morbidity and mortality.15, 17, 18

The sensitivity limits of near infrared spectroscopy for detecting significant events have also been described. Perioperative death has been reported to be associated with baseline saturations of less than 50%.19 Samra et al12 and others20 have reported that a decrease of greater than 20% in rSO2 was highly predictive of the development of intraoperative neurologic symptoms during carotid endarterectomy and syncope during tilt-table testing.21 Furthermore, Dent et al13 reported that a prolonged decrease (>3 hours) of rSO2 to less than 45% was associated with development of new or worsening cerebral ischemia.

Pulse oximetry has long been a part of standard cardiorespiratory monitoring during pediatric procedural sedation, whereas end-tidal carbon dioxide (etco2) capnography use is less common.22 Although the routine administration of supplemental oxygen may limit hypoxemia, this practice may impair either the speed of detection or even the identification of hypercarbic respiratory depression.23, 24, 25 Similarly, pulse oximetry alone may identify only one-third of adverse respiratory events during procedural sedation compared with combining it with etco2 monitoring.3 However, neither pulse oximetry nor etco2 monitoring provides information about the effects of cardiorespiratory derangements on tissue oxygenation, specifically the brain. By estimating cerebral mixed venous oxygen saturation, near infrared spectroscopy monitoring provides an estimate of both oxygen delivery and cerebral oxygen utilization and may, therefore, provide insight into the clinical significance of adverse cardiorespiratory or other events. The overall status of cerebral oxygenation (rSO2) and the effect of cardiorespiratory derangements on rSO2 during procedural sedation have not been reported to date.

The primary aim of this study was to prospectively evaluate the utility of near infrared spectroscopy monitoring and the effects of pediatric procedural sedation on rSO2. Our secondary aim was to evaluate the correlation between derangements in cardiorespiratory parameters and cerebral oxygen saturations. We hypothesized that adverse changes in SpO2 or etco2 would not always correlate with decreases in rSO2.

Section snippets

Study Design and Setting

This was a prospective convenience-sample-based observational study of near infrared spectroscopy in children undergoing procedural sedation. All eligible children who received procedural sedation at various locations (emergency department [ED], inpatient wards, radiology department, or sedation unit) at Kosair Children's Hospital were offered participation during days of enrollment, which depended on the availability of the principal investigator. The Institutional Review Board at the

Characteristics of Study Subjects

One hundred patients were enrolled between October 2006 and March 2007, and their demographics including diagnosis, location, procedure(s) performed, and American Society of Anesthesiologist status, are outlined in Table 2. At baseline, 74% of children were calm and cooperative, whereas 26% were significantly agitated. Ketamine (with or without midazolam) was the most commonly used agent (63%), followed by fentanyl (13%), pentobarbital (13%), dexmedetomidine (11%), and propofol (7%). One third

Limitations

The current study has several limitations. Many children were medicated with midazolam before sensor placement, which may have contributed to erroneous baseline values. However, baseline rSO2 values between premedicated and nonpremedicated patients were not different, so this is unlikely to have been significant. Because anxiety or combativeness is associated with nasal cannula/sensor placement, some parents requested them to be placed only after sedation has been achieved. Hence, true baseline

Discussion

In this prospective, observational pilot study of 100 children, cerebral oxygen saturation was well maintained in a majority of the sedation encounters, adding strength to assertions that transient cardiorespiratory events do not significantly affect tissue oxygen delivery or oxygenation. Even though most reports to date support the safety of procedural sedation in children.5, 33 To our knowledge this is the first study to evaluate the effects of sedation and sedation-related adverse events on

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    Supervising editor: Steven M. Green, MD

    Author contributions: PP, JWB, and MCP conceived the study and designed the trial. PP collected the data. PP, JWB, DL, and MCP conducted the data analysis and drafted and revised the article. PP takes responsibility for the article as a whole.

    Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. The authors have stated that no such relationships exist. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement.

    Publication date: Available online March 13, 2009.

    Reprints not available from the author.

    Dr. Pierce is currently affiliated with Northwestern University Feinberg School of Medicine, Children's Memorial Hospital, Chicago, IL.

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    Copyright © 2009 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.