Bispectral index monitoring quantifies depth of sedation during emergency department procedural sedation and analgesia in children

Abstract

Study objective

The bispectral index monitor uses processed electroencephalogram signals to measure sedation depth on a unitless scale from 0 to 100 (0, coma; 40 to 60, general anesthesia; 60 to 90, sedated; 100, awake). It has been validated in the operating room as an objective measure of sedation depth with nondissociative general anesthesia; however, its usefulness in the pediatric emergency department (ED) for procedural sedation and analgesia has not been established. We determine the ability of the bispectral index to monitor depth of nondissociative procedural sedation and analgesia in children.

Methods

This was an observational study conducted in a children's hospital ED. Procedural sedation and analgesia was performed in the standard manner, with the addition of bispectral index monitoring and simultaneous clinical sedation scoring (modified Ramsay Sedation Scale [range 1 to 8; 1=alert, 8=unresponsive]). Paired bispectral index and Ramsay Sedation Scale scores were assigned every 5 minutes during the sedation. Ramsay Sedation Scale scores were assigned by a single study investigator blinded to the bispectral index score. An emergency physician independently administered all medications for procedural sedation and analgesia. The correlation between the paired bispectral index/Ramsay Sedation Scale scores was determined by using a repeated-measures regression analysis. Receiver operator characteristic (ROC) curves were constructed to determine the ability of the bispectral index to discriminate various thresholds of sedation depth.

Results

A convenience sample of 20 patients was enrolled, providing 217 paired bispectral index/Ramsay Sedation Scale measurements. Median age was 4.6 years (range 0.4 to 16.7 years). Fourteen patients received midazolam with fentanyl; the remainder received pentobarbital. Bispectral index scores ranged from 40 to 98 (mean 81.6±16.1). Ramsay Sedation Scale scores ranged from 1 to 8 (median 3; interquartile range 2 to 4). The simple Pearson correlation between paired bispectral index and Ramsay Sedation Scale scores was −0.78 (95% confidence interval [CI] −0.83 to −0.72; P<.001). After adjustment for the nonindependence of intrapatient data with bivariate repeated-measures analysis, the correlation was −0.67 (95% CI −0.90 to −0.43; P<.001). The linear regression coefficient between bispectral index and Ramsay Sedation Scale scores was estimated to be between −5.7 and −12.7. ROC curve analysis demonstrated moderate to high discriminatory power of bispectral index scores in predicting level of sedation throughout the sedation continuum, with areas under the curve at least 0.87 for all Ramsay Sedation Scale score thresholds. Bispectral index scores between 60 and 90 predicted with moderate accuracy traditional clinical levels of sedation typically encountered during procedural sedation and analgesia in the pediatric ED.

Conclusion

Bispectral index monitoring correlated with clinical sedation scores and may serve as a useful, objective adjunct in quantifying depth of nondissociative procedural sedation and analgesia in children.

Introduction

Procedural sedation and analgesia is widely administered in diverse settings by practitioners of multiple specialties.1, 2 In the pediatric emergency department (ED), procedural sedation and analgesia is practiced daily for radiographic imaging and minor surgical procedures, such as laceration repair and fracture reduction. Accurate assessment of sedation depth is widely held to be important in minimizing the risks of procedural sedation and analgesia performed in the ED. Nondissociative sedation exists as a continuum progressing from mild sedation to general anesthesia. Because a pediatric patient may move easily from a level of light sedation to obtundation, practitioners need to effectively monitor depth of sedation. Undersedation fails to relieve the anxiety and pain associated with procedures, especially in young children, whereas oversedation can lead to serious adverse events, including respiratory depression, loss of protective airway reflexes, vomiting, and potential aspiration.2, 3, 4, 5, 6, 7, 8, 9 Furthermore, oversedation can lead to prolonged recovery times and have a significant effect on patient flow in a busy ED. Clinicians have traditionally relied on subjective and imprecise measures of patient responsiveness to verbal and painful stimuli to judge depth of sedation and analgesia.¹⁰ These measures can be especially difficult to assess in children.

An objective measure of sedation depth could increase patient comfort by minimizing undersedation, enhance safety by minimizing oversedation, and decrease the current labor-intensive nature of procedural sedation and analgesia by shortening recovery and discharge times. The bispectral index monitor (Aspect Medical Systems, Newton, MA) uses highly processed electroencephalogram (EEG) signals acquired from a single, self-adhesive forehead probe to measure sedation depth. Sedation depth is scored on a unitless scale from 0 to 100 (0, coma or absence of brain electrical activity; 0 to 40, deep hypnotic state; 40 to 60, general anesthesia; 60 to 90, deep to light sedation; and 90 to 100, awake). Details about the computation, derivation, and development of the bispectral index can be found elsewhere.11, 12, 13

The bispectral index monitor has been validated in the operating room with adults12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 and children23, 24, 25, 26 as a tool to monitor depth of sedation under nondissociative general anesthesia. In the operating room, hypnotic titration to bispectral index scores 40 to 60 is associated with reduced anesthetic dosing and faster recovery times from anesthesia.19, 20, 24 However, its usefulness in children for ED procedural sedation and analgesia has not been established.12, 27

The primary objective of our study was to determine the ability of the bispectral index to monitor depth of nondissociative procedural sedation and analgesia throughout the sedation continuum in children. If bispectral index monitoring can be shown to reliably predict depth of nondissociative sedation for procedural sedation and analgesia, then practitioners could use the bispectral index monitor to more accurately titrate pediatric patients to a safe and efficacious level of sedation. We hypothesized that bispectral index monitoring would reliably correlate with traditional clinical definitions of sedation depth.