Narcotrend does not adequately detect the transition between awareness and unconsciousness in surgical patients.
ABSTRACT The Narcotrend index (MonitorTechnik, Bad Bramstedt, Germany) is a dimensionless number between 0 and 100 that is calculated from the electroencephalogram and inversely correlates with depth of hypnosis. The current study evaluates the capability of the Narcotrend to separate awareness from unconsciousness at the transition between these levels.
Electroencephalographic recordings of 40 unpremedicated patients undergoing elective surgery were analyzed. Patients were randomly assigned to receive (1) sevoflurane-remifentanil (</= 0.1 microg . kg . min), (2) sevoflurane-remifentanil (>/= 0.2 microg . kg . min), (3) propofol-remifentanil (</= 0.1 microg . kg . min), or (4) propofol-remifentanil (>/= 0.2 microg . kg . min). Remifentanil and sevoflurane or propofol were given until loss of consciousness. After tracheal intubation, propofol or sevoflurane was stopped until return of consciousness and then restarted to induce loss of consciousness. After surgery, drugs were discontinued. Narcotrend values at loss and return of consciousness were compared with each other, and anesthetic groups were compared. Prediction probability was calculated from values at the last command before and at loss and return of consciousness.
At 105 of 316 analyzed time points, the Narcotrend did not calculate an index, and the closest calculated value was analyzed. No significant differences between loss and return of consciousness were found. In group 1, Narcotrend values were significantly higher than in group 3. Prediction probability was 0.501.
In these challenging data, the Narcotrend did not differentiate between awareness and unconsciousness. In addition, Narcotrend values were not independent from the anesthetic regimen.
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ABSTRACT: Entropy as an estimate of complexity of the electroencephalogram is an effective parameter for monitoring the depth of anesthesia (DOA) during surgery. Multiscale entropy (MSE) is useful to evaluate the complexity of signals over different time scales. However, the limitation of the length of processed signal is a problem due to observing the variation of sample entropy (S E ) on different scales. In this study, the adaptive resampling procedure is employed to replace the process of coarse-graining in MSE. According to the analysis of various signals and practical EEG signals, it is feasible to calculate the S E from the adaptive resampled signals, and it has the highly similar results with the original MSE at small scales. The distribution of the MSE of EEG during the whole surgery based on adaptive resampling process is able to show the detailed variation of S E in small scales and complexity of EEG, which could help anesthesiologists evaluate the status of patients.Entropy 12/2012; 6(6). · 1.56 Impact Factor
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ABSTRACT: The research group medical control at the Universities of Rostock (Germany) and Wismar has developed an assistant system for anesthesia to support anesthetists in controlling and maintaining the state of the patient in the operating theatre. The main objectives during general anesthesia are adequate level of hypnosis, analgesia, relaxation, and stable vital functions. During the last 20 years many controllers for the automatic drug delivery in anesthesia were developed. Starting with controllers for keeping a constant level of neuromuscular blockade, controllers for the hypnosis and analgesia were performed. Our research group developed a control system with an adaptive Generalized Controller for the neuromuscular blockade, a fuzzy controller for the control of the level of hypnosis and a fuzzy-system for analgesia control. The current contribution summarizes two studies, the MIMO control of the neuromuscular blockade and the depth of anesthesia which was done with 22 patients and the MIMO control of the depth of anesthesia and the level of analgesia. A model-based predictor for the level of neuromuscular blockade (NMB), to predict the level of NMB after stopping the drug infusion was integrated as a new feature for improving the clinical benefit.Control & Automation (MED), 2013 21st Mediterranean Conference on; 01/2013
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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; · 3.85 Impact Factor