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State entropy and bispectral index: correlation with end tidal sevoflurane concentrations
S Rinaldi1, G Consales, A R De Gaudio
1Anesthesiology and Intensive Care Unit, Department of Critical Care, University of Florence, Florence, Italy. ilsimo7@hotmail.com
Minerva Anestesiologica
|March 16, 2007
Summary
State entropy (SE) and bispectral index (BIS) monitor anesthetic depth. SE demonstrated a stronger correlation with end-tidal sevoflurane concentrations than BIS, particularly at higher concentrations, indicating its potential utility in anesthesia monitoring.
Area of Science:
- Anesthesiology
- Neuroscience
- Medical Devices
Background:
- Monitoring anesthetic depth is crucial for patient safety.
- State entropy (SE) and bispectral index (BIS) are commonly used electroencephalogram-based indices.
- Sevoflurane is a widely used inhalation anesthetic agent.
Purpose of the Study:
- To compare the correlation between state entropy (SE) and bispectral index (BIS) with varying end-tidal sevoflurane concentrations.
- To determine which index, SE or BIS, better reflects sevoflurane levels during anesthesia.
Main Methods:
- 40 ASA I/II patients undergoing abdominal surgery were studied.
- Anesthesia was maintained with sevoflurane, with simultaneous recording of end-tidal sevoflurane, SE, and BIS.
- Pearson correlation and Student's t-test were used to analyze the data at sevoflurane concentrations above and below the mean (1.5%).
Main Results:
- Overall, SE showed a stronger correlation (-0.75) with end-tidal sevoflurane than BIS (-0.70).
- At higher sevoflurane concentrations (>1.5%), SE correlation (-0.41) surpassed BIS (-0.14).
- At lower sevoflurane concentrations (<1.5%), BIS correlation (-0.8) was slightly stronger than SE (-0.65), but the difference between indices was statistically significant.
Conclusions:
- State entropy (SE) exhibits a superior correlation with end-tidal sevoflurane concentrations compared to the bispectral index (BIS) during sevoflurane anesthesia.
- While BIS may show a slightly better correlation at very low sevoflurane levels, SE demonstrates a more robust correlation at higher concentrations, suggesting its potential as a more reliable depth of anesthesia monitor in these ranges.
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