Hypnosis monitoring during general anaesthesia : with focus on awareness
Author: Ekman, Andreas
Date: 2007-11-30
Location: Leksellsalen, Medicinhistoriska muséet, Karolinska Universitetssjukhuset Solna.
Time: 09.00
Department: Institutionen för fysiologi och farmakologi / Department of Physiology and Pharmacology
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thesis.pdf (1023.Kb)
Abstract
An objective measure of the hypnotic component of general anaesthesia
has been sought for decades. The electroencephalogram (EEG) was early recognized as a possible useful
intraoperative monitor when the effects of anaesthetic drugs on human EEG
recordings were noted. The last few years have brought forward a number
of commercialized monitor devices that by an index claim to give the
anaesthetist an objective measure of hypnosis. Two diverse monitoring
methods, differing in principle, have been developed: 1) passively
processed EEG, and 2) stimulated and thereafter processed EEG. The
Bispectral Index Scale (BIS) and the A-line ARX-Index (AAI) are two
such monitors were BIS represents the first principle and AAI the second.
In several studies the use of BIS and AAI has been shown to reduce the amount of anaesthetics given and expedite postoperative recovery as compared to standard practice. However a number of studies have also shown that the sensitivity and specificity for BIS and AAI are not perfect, and fears have been raised that the incidence of awareness even might increase if the anaesthetist aims at an upper threshold value. In this thesis, it is demonstrated that BIS monitoring during general anaesthesia in a noncardiac, surgical population requiring endotracheal intubation and/or a neuromuscular blocking agent (NMBA) was associated with a significantly reduced incidence of awareness as compared to a historical control population.
Our results suggest that BIS better displays drug related alterations in the level of hypnosis than AAI in an already anesthetized patient, and that there is no difference between BIS and AAI in the response time to a noxious stimulus. We have further seen that profound neuromuscular block attenuate BIS and AAI responses to a standardized noxious stimulation during sevoflurane anaesthesia as compared to a partial neuromuscular block or after neostigmine induced reversal, and that the monitor responses were not due to electromyogram (EMG) contamination of the EEG. It is demonstrated that EEG responses to noxious stimulation, in terms of power and coherence in the γ-band, are affected by profound neuromuscular block during light sevoflurane anaesthesia.
In conclusion we demonstrate that hypnosis monitoring can reduce the incidence of awareness, BIS is superior to AAI to display alterations in the level of hypnosis during aneasthesia and NMBAs affect the level of hypnosis during light general anaesthesia in stimulated patients.
In several studies the use of BIS and AAI has been shown to reduce the amount of anaesthetics given and expedite postoperative recovery as compared to standard practice. However a number of studies have also shown that the sensitivity and specificity for BIS and AAI are not perfect, and fears have been raised that the incidence of awareness even might increase if the anaesthetist aims at an upper threshold value. In this thesis, it is demonstrated that BIS monitoring during general anaesthesia in a noncardiac, surgical population requiring endotracheal intubation and/or a neuromuscular blocking agent (NMBA) was associated with a significantly reduced incidence of awareness as compared to a historical control population.
Our results suggest that BIS better displays drug related alterations in the level of hypnosis than AAI in an already anesthetized patient, and that there is no difference between BIS and AAI in the response time to a noxious stimulus. We have further seen that profound neuromuscular block attenuate BIS and AAI responses to a standardized noxious stimulation during sevoflurane anaesthesia as compared to a partial neuromuscular block or after neostigmine induced reversal, and that the monitor responses were not due to electromyogram (EMG) contamination of the EEG. It is demonstrated that EEG responses to noxious stimulation, in terms of power and coherence in the γ-band, are affected by profound neuromuscular block during light sevoflurane anaesthesia.
In conclusion we demonstrate that hypnosis monitoring can reduce the incidence of awareness, BIS is superior to AAI to display alterations in the level of hypnosis during aneasthesia and NMBAs affect the level of hypnosis during light general anaesthesia in stimulated patients.
List of papers:
I. Ekman A, Lindholm ML, Lennmarken C, Sandin R (2004). "Reduction in the incidence of awareness using BIS monitoring." Acta Anaesthesiol Scand 48(1): 20-6
Pubmed
II. Ekman A, Brudin L, Sandin R (2004). "A comparison of bispectral index and rapidly extracted auditory evoked potentials index responses to noxious stimulation during sevoflurane anesthesia." Anesth Analg 99(4): 1141-6
Pubmed
III. Ekman A, Stålberg E, Sundman E, Eriksson LI, Brudin L, Sandin R (2007). "The effect of neuromuscular block and noxious stimulation on hypnosis monitoring during sevoflurane anesthesia." Anesth Analg 105(3): 688-95
Pubmed
IV. Ekman A, Flink R, Sundman E, Eriksson LI, Brudin L, Sandin R (2007). "Neuromuscular block and the electroencephalogram during sevoflurane anaesthesia." Neuroreport 18: 1817-20
I. Ekman A, Lindholm ML, Lennmarken C, Sandin R (2004). "Reduction in the incidence of awareness using BIS monitoring." Acta Anaesthesiol Scand 48(1): 20-6
Pubmed
II. Ekman A, Brudin L, Sandin R (2004). "A comparison of bispectral index and rapidly extracted auditory evoked potentials index responses to noxious stimulation during sevoflurane anesthesia." Anesth Analg 99(4): 1141-6
Pubmed
III. Ekman A, Stålberg E, Sundman E, Eriksson LI, Brudin L, Sandin R (2007). "The effect of neuromuscular block and noxious stimulation on hypnosis monitoring during sevoflurane anesthesia." Anesth Analg 105(3): 688-95
Pubmed
IV. Ekman A, Flink R, Sundman E, Eriksson LI, Brudin L, Sandin R (2007). "Neuromuscular block and the electroencephalogram during sevoflurane anaesthesia." Neuroreport 18: 1817-20
Issue date: 2007-11-09
Rights:
Publication year: 2007
ISBN: 978-91-7357-381-8
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