Korean J Anesthesiol.  2012 Mar;62(3):230-233. 10.4097/kjae.2012.62.3.230.

Effects of etomidate on bispectral index scale and spectral entropy during induction of anesthesia by means of the raw electroencephalographic and electromyographic characteristics

• Kim HM
• Shin SW
• Yoon JY
• Lee HJ
• Kim KH
• Baik SW

• KMID: 2299348
• DOI: http://doi.org/10.4097/kjae.2012.62.3.230

Abstract

BACKGROUND
Etomidate frequently induces myoclonus, so it may affect electromyographics (EMG). And EMG commonly has an effect on the bispectral index scale (BIS) and spectral entropy. This study was performed to compare the effect of etomidate on BIS, response entropy (RE) and state entropy (SE) during induction of anesthesia.
METHODS
Fifty patients (ASA I or II) scheduled for elective surgery were included in this study. Anesthesia was induced with etomidate (0.3 mg/kg) and rocuronium (0.6 mg/kg). Patients also inhaled 4 vol% sevoflurane and 100% oxygen and, then intubated. BIS, RE, SE and Modified Observer's Assessment of Alertness/Sedation Scale (MOAA/S) were measured 4 times (before injection of etomidate [T0], at loss of eyelash reflex [T1], 90 seconds after rocuronium injection [T2], and after intubation [T3]). We also checked whether myoclonus occurred.
RESULTS
Baseline values (T0) were 93.1 +/- 4.7 for BIS, 95.8 +/- 3.7 for RE and, 87.3 +/- 3.5 for SE. In comparison with T0, there were significantly differences in BIS (50.2 +/- 16.3), RE (76.8 +/- 18.5) and SE (66.3 +/- 17.4) at T1 (all P < 0.05). There were no significant differences at T2 and T3. Thirty one patients had myoclonus. At the occurrence of myoclonus, RE and SE values significantly increased but not BIS (P < 0.05).
CONCLUSIONS
In patients with myoclonus, at the loss of consciousness, spectral entropy did not decrease where as BIS did, suggesting that BIS may evaluate hypnotic levels better than spectral entropy during induction of anesthesia with etomidate.

Keyword

Bispectral index scale; Electromyography; Entropy; Etomidate; Myoclonus

MeSH Terms

Androstanols
Anesthesia
Electromyography
Entropy
Etomidate
Humans
Intubation
Methyl Ethers
Myoclonus
Oxygen
Reflex
Unconsciousness
Androstanols
Etomidate
Methyl Ethers
Oxygen