NI and BIS are superior to spectral and entropy parameters in describing changes of propofol concentration during induction of propofol-remifentanil anaesthesia.
& Introduction: It was to be examined whether EEG monitoring infl uences the dosing practice of propofol, taking into account age, gender, mode of propofol administration, and opioid choice. Methods: At 32 study sites, 3 542 patients received total intravenous anaesthesia (TIVA) or target-controlled infusion (TCI). 472 anaesthetics were controlled by clinical parameters (blinded EEG recordings), in 3 070 anaesthetics, the EEG was used for the control of anaesthesia (EEG monitor Narcotrend ® , EEG classifi cation into the stages A (awake) to F (very deep anaesthesia)). Results: Without EEG monitoring, 5.9 % of the anaesthetics were maintained in stage B / C (increased risk of awareness), in 18.7 % a burst suppression EEG was found (individual overdosage of general anaesthesia, stage F). 67.2 % were conducted in stages D / E, which correspond to deep sleep. EEG monitoring resulted in changes of the propofol dosage from − 28.4 % to + 86.2 % . In EEG controlled anaesthetics, women received more propofol than men and had shorter recovery times. Furthermore, with increasing age, a larger reduction of the propofol dosages was found than without EEG, and the diff erence between the propofol dosages of both genders became smaller with increasing age. Compared to fentanyl, the use of the short-acting opioid remifentanil led to a signifi cant reduction in propofol requirements and recovery times. EEG monitoring caused a signifi cant reduction in propofol consumption with TCI. Discussion: A considerable number of the anaesthetics which were controlled solely by clinical parameters was too light or too deep. EEG monitoring resulted in signifi cant changes in the dosing strategies at the study sites. Conclusion: EEG monitoring helps to determine the individual requirements for propofol, which depend on gender, age, and opioid choice.
Xenon was approved as an inhaled anaesthetic in Germany in 2005 and in other countries of the European Union in 2007. Owing to its low blood/gas partition coefficient, xenons effects on the central nervous system show a fast onset and offset and, even after long xenon anaesthetics, the wake-up times are very short. The aim of this study was to examine which electroencephalogram (EEG) stages are reached during xenon application and whether these stages can be identified by an automatic EEG classification. Therefore, EEG recordings were performed during xenon anaesthetics (EEG monitor: Narcotrend®). A total of 300 EEG epochs were assessed visually with regard to the EEG stages. These epochs were also classified automatically by the EEG monitor Narcotrend® using multivariate algorithms. There was a high correlation between visual and automatic classification (Spearman's rank correlation coefficient r=0.957, prediction probability Pk=0.949). Furthermore, it was observed that very deep stages of hypnosis were reached which are characterised by EEG activity in the low frequency range (delta waves). The burst suppression pattern was not seen. In deep hypnosis, in contrast to the xenon EEG, the propofol EEG was characterised by a marked superimposed higher frequency activity. To ensure an optimised dosage for the single patient, anaesthetic machines for xenon should be combined with EEG monitoring. To date, only a few anaesthetic machines for xenon are available. Because of the high price of xenon, new and further developments of machines focus on optimizing xenon consumption.
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