Comparative Pharmacodynamic Modeling Using Bispectral and Narcotrend-Index With and Without a Pharmacodynamic Plateau During Sevoflurane Anesthesia

Background The Bispectral Index (BIS) and the Patient State Index (PSI) quantify depth of anesthesia by analyzing the electroencephalogram. The authors examined the response of BIS and PSI to sevoflurane anesthesia. Methods In 22 patients, sevoflurane anesthesia was induced by inhalation with a tight-fitting facemask and was maintained via a laryngeal mask. Sevoflurane concentrations were increased until burst suppression occurred and subsequently decreased until BIS recovered to values above 60. This procedure was repeated twice until patients underwent intubation for subsequent surgery. End-tidal sevoflurane concentrations, BIS, and PSI were recorded simultaneously. The performance of PSI and BIS to predict the estimated sevoflurane effect site concentration, as derived from simultaneous pharmacokinetic and pharmacodynamic modeling, was compared by determination coefficients (rho(2)) and prediction probabilities (P(K)). Results A significant (P < 0.001) correlation between BIS and PSI was found (r(2) = 0.75), and a close sigmoid relation between sevoflurane effect site concentration and both BIS (rho(2) = 0.84 +/- 0.09) and PSI (rho(2) = 0.85 +/- 0.15) was observed. The maximum sevoflurane electroencephalographic effect resulted in PSI values (1.3 +/- 4.3) that were significantly (P = 0.019) lower than BIS values (7.9 +/- 12.1), and the effect site efflux constant k(e0) was significantly smaller (P = 0.001) for PSI (0.13 +/- 0.08 min(-1)) than for BIS (0.24 +/- 0.15 min(-1)). The probability of BIS (P(K) = 0.80 +/- 0.11) to predict sevoflurane effect site concentration did not differ (P = 0.76) from that of PSI (P(K) = 0.79 +/- 0.09). Conclusions The BIS reacted faster to changes in sevoflurane concentrations, whereas the PSI made better use of the predefined index range. However, despite major differences in their algorithms and minor differences in their dose-response relations, both PSI and BIS predicted depth of sevoflurane anesthesia equally well.

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Application of Bispectral Index® and Narcotrend® Index to the Measurement of the Electroencephalographic Effects of Isoflurane with and without Burst Suppression

Anesthesiology ◽

10.1097/00000542-200410000-00008 ◽

2004 ◽

Vol 101 (4) ◽

pp. 847-854 ◽

Cited By ~ 42

Author(s):

Sascha Kreuer ◽

Jörgen Bruhn ◽

Reinhard Larsen ◽

Ulrich Grundmann ◽

Steven L. Shafer ◽

...

Keyword(s):

General Anesthesia ◽

Bispectral Index ◽

Visual Assessment ◽

Burst Suppression ◽

Pharmacodynamic Modeling ◽

Effect Compartment ◽

Medical Systems ◽

Prediction Probability ◽

End Tidal ◽

Narcotrend Index

Background The Narcotrend monitor (MonitorTechnik, Bad Bramstedt, Germany) has recently been introduced as an intraoperative monitor of anesthetic state, based on a classification scheme originally developed for visual assessment of the electroencephalogram. The authors compared the performance of the Narcotrend index (software version 4.0) to the Bispectral Index (BIS, version XP; Aspect Medical Systems, Natick, MA) as electroencephalographic measures of isoflurane drug effect during general anesthesia. Methods The authors observed 15 adult patients scheduled to undergo radical prostatectomy with a combined epidural-isoflurane general anesthesia technique. At least 45 min after induction of general anesthesia, during a phase of constant surgical stimulation, end-tidal isoflurane concentrations were varied between 0.5 and 2.0 multiples of minimum alveolar concentration, and the BIS and the Narcotrend index were recorded. The prediction probability (PK) was calculated for the BIS and the Narcotrend index to predict isoflurane effect compartment concentration for each measure. The correlation analysis of the BIS and the Narcotrend index with the isoflurane effect compartment concentration was obtained by pharmacodynamic modeling based on two sigmoidal curves to account for the discontinuity in both indices with the onset of burst suppression. Results The prediction probabilities were indistinguishable (BIS PK = 0.72 +/- 0.07 (mean +/- SD); range, 0.61-0.84; Narcotrend index PK = 0.72 +/- 0.10; range, 0.51-0.87), as were the correlations between the electroencephalographic measures and isoflurane effect compartment concentrations (BIS R = 0.82 +/- 0.12; Narcotrend index R = 0.85 +/- 0.09). The pharmacodynamic models for the BIS and the Narcotrend index yielded nearly identical results. Conclusions The BIS and the Narcotrend index detected the electroencephalographic effects of isoflurane equally. Combining two fractional sigmoid Emax models adequately described the data before and after the onset of burst suppression.

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