Background
Oversedation masks neurologic changes and increases mortality/morbidity, whereas undersedation
risks prolonged stress mobilization and patient injury. In situations such as deep
sedation/analgesia, the Bispectral Index (BIS) has potential use as an adjunct to
clinical assessment of sedation to help determine depth of sedation. Determining the
correlation between clinical and BIS measures of sedation will help to determine the
correct role of BIS in intensive care unit (ICU) practice settings.
Objective
To evaluate the correlation between the clinical assessment of sedation using the
Sedation-Agitation Scale (SAS) and the assessment using BIS in ventilated and sedated
ICU patients.
Methods
ICU patients requiring mechanical ventilation and sedation were monitored using the
SAS and BIS. Nurses initiated event markers with BIS at the time of SAS assessment
but were blinded to BIS scores.
Results
Data were collected on 40 subjects generating 209 paired readings. Moderate positive
correlation between BIS and SAS values was shown with a Spearman Rank coefficient
r value of .502 and an r2 of .252 (P < .0001). Wide ranges of BIS scores were observed, especially in very sedated patients.
Strong positive correlation was noted between BIS and electromyography with an r value of .749 (P < .0001). Age and gender significantly influenced BIS/SAS correlations.
Conclusion
In situations in which the clinical assessment is equivocal, BIS monitoring may have
an adjunctive role in sedation assessment. BIS values should be interpreted with caution,
however, because electromyography activity and other factors seem to confound BIS
scores. More research is necessary to determine the role of BIS monitoring in ICU
practice.
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Article info
Publication history
Published online: January 22, 2009
Footnotes
This research was funded by the American Association of Critical Care Nurses/Sigma Theta Tau Critical Care Research Grant.
This research was performed at Christiana Care Health System in Newark, Delaware.
Identification
Copyright
© 2009 Mosby, Inc. Published by Elsevier Inc. All rights reserved.
