Korean J Anesthesiol.  2000 Jun;38(6):959-970. 10.4097/kjae.2000.38.6.959.

Correlations among Bispectral Index, Observer's Assessment of Alertness/sedation (OAA/S) Scale and Blood Concentration during Anesthesia Induction with Etomidate

• Lee SK
• Kil HY

• KMID: 2155245
• DOI: http://doi.org/10.4097/kjae.2000.38.6.959

Abstract

BACKGROUND: Etomidate is a rapid-acting sedative/hypnotic agent with little or no cardiovascular effect and a high therapeutic index. For this reason, etomidate has been used as an anesthetic induction and maintenance agent in patients with poor cardiovascular reserve. Bispectral index (BIS), a parameter derived from electroencephalography (EEG), has been proposed as a measure of anesthetic effect and is shown to correlate with increasing sedation and loss of consciousness. To establish its utility for this purpose, it is important to determine the correlation among BIS, measured drug concentration, and increasing levels of sedation. This study was designed to evaluate this relation for etomidate.
METHODS
Eighteen adult patients scheduled for elective surgery, ASA physical status I or II, were included. Etomidate was administerd until loss of consciousness (loss of verbal contact) using syringe pump with a constant rate (150 ml/h) and patients were observed until regaining consciousness as decided by prompt verbal response on command of "open your eyes". A BIS was monitored, arterial blood samples were obtained for analysis of drug concentration, and the patients were evaluated for level of sedation by the responsiveness portion of the modified observer's assessment of alertness/sedation (OAA/S) scale.
RESULTS
The BIS (r = 0.86) correlated significantly with the OAA/S more than the etomidate plasma concentration (r = 0.57). The BIS values, OAA/S, and blood concentrations were 50, 1.26, and 1337 ng/ml at induction and 75, 4.6, and 236 ng/ml at awakening, respectively.
CONCLUSIONS
We concluded that the BIS accurately predicted level of sedation with etomidate during anesthesia induction, but the correlation between blood concentration and level of sedation was less strong.

Keyword

Anesthetics, intravenous: etomidate; Equipment: monitoring device; Bispectral index

MeSH Terms

Adult
Anesthesia*
Anesthetics
Consciousness
Electroencephalography
Etomidate*
Humans
Plasma
Syringes
Unconsciousness
Anesthetics
Etomidate