Conference Paper

EEG frequency progression during induction of anesthesia: from start of infusion to onset of burst suppression pattern

Department of Electrical and Information Engineering, BOX 4500, FIN-90014 University of Oulu, Finland.
DOI: 10.1109/IEMBS.2007.4352604 Conference: Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
Source: PubMed

ABSTRACT The anesthetic infusion with propofol influences EEG activity rather smoothly by changing the amplitude activity in different frequency bands. This results in a frequency progression pattern (FPP) which can be related to the depth of anesthesia. An iterative algorithm is proposed for the estimation of the shape of this pattern. The presented method is applied to the data recorded from the start of the propofol anesthetic infusion to the onset of the burst suppression pattern (BSP) with nine patients. The results reveal the underlying FPP and how the onset of the BSP is related to it. The proposed method offers potential for the development of automatic assessment systems for the depth of anesthesia.

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    ABSTRACT: Somatosensory evoked potentials (SEPs) are widely used in the clinic as well as research to study the functional integrity of the different parts of sensory pathways. However, most general anesthetics, such as isoflurane, are known to suppress SEPs, which might affect the interpretation of the signals. In animal studies, the usage of anesthetics during SEP measurements is inevitable due to which detailed effect of these drugs on the recordings should be known. In this paper, the effect of isoflurane on SEPs was studied in a rat model. Both time and frequency properties of the cortical recordings generated by stimulating the tibial nerve of rat's hindlimb were investigated at three different isoflurane levels. While the anesthetic agent is shown to generally suppress the amplitude of the SEP, the effect was found to be nonlinear influencing more substantially the latter part of waveform. This finding will potentially help us in future work aiming at separating the effects of anesthetics on SEP from those due to injury in the ascending neural pathways.
    Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference; 08/2014
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    ABSTRACT: /st>MAC (minimum alveolar concentration of an inhaled anaesthetic) and CP50i (minimum plasma concentration of i.v. anaesthetics) are well-established measures to compare potencies of anaesthetics. The underlying clinical endpoint immobility reflects mainly effects of anaesthetics on the spinal cord, which limits the use of this measure for comparison of effects on the main target organ of general anaesthesia-the brain. The present study determines the median concentration of sevoflurane, isoflurane, and propofol that induce the onset of electroencephalogram (EEG) suppression ('silent second'): MACBS and CP50BS. /st>Fifty-five unpremedicated patients (ASA physical status of I or II) undergoing elective surgery were randomly assigned to receive general anaesthesia with sevoflurane, isoflurane, or propofol. A two-channel EEG was continuously recorded to identify 'silent second'. Independent cross-over pairs were analysed using the 'Dixon's up-and-down' method, and MACBS/CP50BS values were calculated by logistic regression. /st>CP50BS was 4.9 µg ml(-1) for propofol. MACBS was 2.9 vol% for sevoflurane and 1.5 vol% for isoflurane. CP50BS of propofol was less than one-third of CP50i, whereas MACBS of sevoflurane was >1.4-fold of MAC; MACBS of isoflurane was 1.3-fold of MAC. /st>Immobility and cerebral effects reflect different entities of anaesthetic action. The median concentration of anaesthetic drug (volatile or i.v. agent) required to induce 'silent second' might be a more useful metric than the median concentration required to prevent movement in response to a surgical stimulus in order to compare relative potencies of anaesthetic agents on the brain. Advantage of the 'silent second' is an easy identification of this endpoint, while such a deep level is not required for clinical anaesthesia.
    BJA British Journal of Anaesthesia 03/2014; 112(6). DOI:10.1093/bja/aeu016 · 4.35 Impact Factor
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    ABSTRACT: Within the last few decades, electroencephalogram (EEG) has become a widely used tool for the automatic assessment of depth of anesthesia. The EEG-based depth of anesthesia measurement has been associated with several advantages, such as a decreased incidence of intraoperative awareness and recall, faster recovery, and reduced consumption of anesthetics. However, the measurement is challenged by simultaneous administration of different types of anesthetics, which is the common practice in the operating rooms today. Especially, the assessment of depth of anesthesia induced by supplementing the primary anesthetic drug, i.e. the hypnotic agent, with an opioid has been raised as one of the major problems in the field. In this thesis, the EEG-based depth of anesthesia measurement during multidrug infusion with propofol (hypnotic agent) and remifentanil (opioid) is addressed. The problem is approached by first giving a quantitative description for the EEG changes occurring during propofol infusion. Two different methods, both utilizing the spectral properties of EEG, for this are presented. Next, the effects of remifentanil on the clinical signs and EEG changes during propofol infusion are investigated by applying the first one of the presented methods. Coadministration of opioid is shown to significantly modify the mutual relations of the EEG changes and the clinical signs of the patient. Furthermore, remifentanil is found to significantly affect the EEG itself, more specifically, the power spectrum and derived quantitative parameters during propofol infusion. This effect is strongly dependent on the level of anesthesia. Finally, by utilizing the results on the effects of remifentanil, a technology is developed for the assessment of depth of propofolremifentanil anesthesia. The technology is based on improving the determination of the anesthetic state of the patient by EEG-based separation of the effects of propofol and remifentanil. The thesis provides a framework for the depth of anesthesia measurement during multidrug administration with propofol and remifentanil. Due to the similar mechanisms of action, the results are likely to be generalizable to other hypnotic-opioid drug combinations. The study thus offers potential for the development of more advanced systems for automatic monitoring of depth of anesthesia.
    09/2011, Degree: D.Sc., Supervisor: Professor Tapio Seppänen


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Jul 30, 2014