Application of Bispectral Index((R)) and Narcotrend((R)) index to the measurement of the electroencephalographic effects of isoflurane with and without burst suppression
ABSTRACT 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.
SourceAvailable from: Tadeusz Musialowicz[Show abstract] [Hide abstract]
ABSTRACT: Monitoring the level of consciousness during general anesthesia with processed electroencephalogram (EEG) monitors has become an almost routine practice in the operating room, despite ambiguous research results regarding its potential benefits. For the patient as well as the anesthesiologist, the primary concern with respect to general anesthesia is that there will be a lack of awareness and recall during surgery. Using EEG signals to monitor the depth of anesthesia should reduce the incidence of intraoperative awareness, lead to a reduction in drug consumption, prevent anesthesia-related adverse events, and enable faster recovery. These benefits have been associated with depth-of-anesthesia monitoring in small clinical trials, but larger studies of EEG-based monitoring have failed to confirm the results of the smaller studies. The results of recent studies that investigated the emergence of consciousness after general anesthesia and the mechanism of action of anesthetic drugs on the central nervous system may help us to understand the limitations of EEG-based monitors and why they do not perform better in large clinical trials. In this article, we review the current status of monitoring the hypnotic component of general anesthesia and discuss the results of recent studies and guidelines that pertain to depth-of-anesthesia monitoring.09/2014; 4(3). DOI:10.1007/s40140-014-0061-x
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ABSTRACT: Although the brain is the target organ of general anaesthesia, the utility of intra-operative brain monitoring remains controversial. Ideally, the incorporation of brain monitoring into routine practice would promote the maintenance of an optimal depth of anaesthesia, with an ultimate goal of avoiding the negative outcomes that have been associated with inadequate or excessive anaesthesia. A variety of processed electroencephalogram devices exist, of which the bispectral index is the most widely used, particularly in the research setting. Whether such devices prove to be useful will depend not only on their ability to influence anaesthetic management but also on whether the changes they promote can actually affect clinically important outcomes. This review highlights the evidence for the role of bispectral index monitoring, in particular, in guiding anaesthetic management and influencing clinical outcomes, specifically intra-operative awareness, measures of early recovery, mortality and neurocognitive outcomes.Anaesthesia 06/2014; 69(8). DOI:10.1111/anae.12711 · 3.85 Impact Factor
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ABSTRACT: To easily measure the depth of anaesthesia during routine surgical procedures has always been a goal in anaesthesiology. For decades, scientists have been developing indices to describe and evaluate the depth of anaesthesia. Historically, mean alveolar gas concentration (MAC) values for volatile anaesthetics have been used to target a predefined level of anaesthesia. MAC values were however not established to differentiate between the hypnotic and analgesic components of anaesthesia. Indices were therefore developed that measure the effect of hypnotics predominantly on the brain (in contrast to an effect on the spinal cord) with the vision to be able to measure the transition from consciousness to unconsciousness. Although monitors measuring the depth of anaesthesia are still not capable of measuring the transition from consciousness to unconsciousness, brain monitoring has proved to help clinicians control the depth of anaesthesia. Clinical trials have shown that the use of brain-monitoring devices can lead to a reduction of intraoperative drug consumption, reduced incidence of postoperative nausea and vomiting, facilitate recovery from anaesthesia compared to routine care and can also lead to a reduction of intraoperative awareness. However a study demonstrating both a reduced intraoperative drug consumption and at the same time a reduction of intraoperative awareness due to the use of brain-monitoring devices has not been published yet.06/2013; 27(2):225-33. DOI:10.1016/j.bpa.2013.06.006