Application of Bispectral Index® and Narcotrend® Index to the Measurement of the Electroencephalographic Effects of Isoflurane with and without Burst Suppression
Stanford University, Palo Alto, California, United States Anesthesiology
(Impact Factor: 5.88).
11/2004; 101(4):847-54. DOI: 10.1097/00000542-200410000-00008
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.
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.
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.
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.
Available from: Olinto Linares
- "A classical sigmoidal Emax model has been commonly used to describe the dose-response relationship between anesthetic drugs and electroencephalographic data because of the advantage of its high flexibility. However, as anesthetic doses increase, two pronounced pharmacodynamic plateaus appear in the dose-response curves of the processed EEG devices9, 10, 11. These biphasic dose-response curves suggest that the classical sigmoidal Emax model cannot reflect these data, and thus a new pharmacodynamic model needs to be developed. "
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ABSTRACT: The cerebral state index (CSI) was recently introduced as an electroencephalographic monitor for measuring the depth of anesthesia. We compared the performance of CSI to the bispectral index (BIS) as electroencephalographic measures of sevoflurane effect using two combined sigmoidal E(max) models.
Twenty adult patients scheduled for laparotomy were studied. After induction of general anesthesia, sevoflurane concentrations were progressively increased and then decreased over 70 min. An analysis of the BIS and CSI with the sevoflurane effect-site concentration was conducted using two combined sigmoidal E(max) models.
The BIS and CSI decreased over the initial concentration range of sevoflurane and then reached a plateau in most patients. A further increase in sevoflurane concentration produced a secondary plateau in the pharmacodynamic response. The CSI was more strongly correlated with effect-site sevoflurane concentration (R(2)=0.95±0.04) than the BIS was (R(2)=0.87±0.07) (P<0.05). The individual E(max) and C(eff50) (effect-site concentration associated with 50% decrease from baseline to plateau) values for the upper and lower plateaus were significantly greater for BIS (12.7±7.3, 1.6±0.4, and 4.2±0.5, respectively) than for CSI (3.4±2.2, 1.2±0.4, and 3.8±0.5, respectively) (P<0.05). The remaining pharmacodynamic parameters for the BIS and CSI were similar.
The overall performance of the BIS and CSI during sevoflurane anesthesia was similar despite major differences in their algorithms. However, the CSI was more consistent and more sensitive to changes in sevoflurane concentration, whereas the measured BIS seemed to respond faster. The newly developed combined E(max) model adequately described the clinical data, including the pharmacodynamic plateau.
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ABSTRACT: This chapter discusses that current clinical practice in anesthesiology is focused on balanced anesthetic technique, in which a number of drugs with distinct effects are delivered to achieve desired goals. In contrast to the past use of exclusively inhalational anesthesia, it is now a routine to administer neuromuscular blockers for the suppression of movement, opiates for pain control, benzodiazepines for amnesia, and beta-blockers for the attenuation of cardiovascular responses. The chapter reviews that electroencephalography (EEG) based technologies play an increasingly important role in the maintenance of general anesthesia within the therapeutic window. The bispectral index (BIS) monitor has been clinically validated as a measure of hypnosis in the adult and pediatric population, and has demonstrated efficacy in the prevention of intraoperative awareness. It discusses that the suggestion that BIS values <45 may be associated with postoperative mortality at one year indicates the need for further study of the physiologic sequelae of deep anesthesia. Perhaps the refinement of “closed-loop” systems, in which anesthetic delivery is controlled based on the feedback from BIS values will aid in maintaining appropriate depth of anesthesia. The chapter concludes that the neurophysiology of anesthetic depth remains linked to the persistent questions regarding the neural correlates of consciousness and cognition.
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