Academic literature on the topic 'Anaesthesia; EEG'
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Journal articles on the topic "Anaesthesia; EEG"
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Pomfrett, C. J. D. "The EEG during anaesthesia." Current Anaesthesia & Critical Care 9, no. 3 (1998): 117–22. http://dx.doi.org/10.1016/s0953-7112(98)80004-5.
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Harris, Charissa, Peter John White, Virginia L. Mohler, and Sabrina Lomax. "Electroencephalography Can Distinguish between Pain and Anaesthetic Intervention in Conscious Lambs Undergoing Castration." Animals 10, no. 3 (2020): 428. http://dx.doi.org/10.3390/ani10030428.
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Australian sheep routinely undergo painful surgical husbandry procedures without anaesthesia or analgesia. Electroencephalography (EEG) has been shown to be a successful measure of pain in livestock under a general anaesthetic. The aim of this study was to compare this EEG model to that of conscious lambs undergoing castration with and without local anaesthesia. Sixteen merino crossbred ram lambs 6 to 8 weeks of age (13.81kg ± 1.97) were used in the study. Lambs were randomly allocated to 1 of 4 treatment groups: (1) Conscious EEG and surgical castration with no anaesthetic intervention (CON; n = 4); (2) Conscious EEG and surgical castration with pre-operative applied intra-testicular lignocaine injection (CON + LIG; n = 4); (3) surgical castration under minimal anaesthesia (MAM; n = 4); (4) and surgical castration with pre-operative lignocaine injection (2 mL lignocaine hydrochloride 20 mg/mL, under minimal anaesthesia (MAM + LIG; n = 4). Distinct differences in the EEG parameters Ptot, F50 and F95 between pre-and post-castration in conscious lambs were demonstrated in this study (p < 0.01). Further, CON and CON + LIG treatments were distinguishable using F50 and F95 measures (p = 0.02, p = 0.04, respectively). Significant changes in the EEG output of MAM animals were identified pre- to post-castration (p < 0.01). The EEG output of MAM and MAM + LIG were similar. EEG was successful in differentiating lambs treated with pain relief in a conscious state after castration by examining F50 and F95, which may suggest the suitability of conscious EEG pain measurement.
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Johnson, B. W., J. W. Sleigh, I. J. Kirk, and M. L. Williams. "High-density EEG Mapping during General Anaesthesia with Xenon and Propofol: A Pilot Study." Anaesthesia and Intensive Care 31, no. 2 (2003): 155–63. http://dx.doi.org/10.1177/0310057x0303100203.
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Anaesthetic-induced spatial inhomogeneities of the electrencephalogram(EEG) using “high density” electrode mapping have not previously been reported. We measured the scalp EEG with a dense electrode (128-channel) montage during the course of light general anaesthesia with xenon and then propofol in normal human subjects. EEG was measured during induction and recovery of general anaesthesia in five normal subjects, and we obtained analysable data from three of these subjects. EEG topographies were plotted on a realistic head surface. Scalp fields were spatially de-blurred using a realistic head model and projected onto an averaged cortical surface Both xenon and propofol elicited large increases in midline frontal theta-band EEG power. Propofol reliably elicited orbitofrontal delta activity. Xenon, but not propofol, caused large increases in delta over the posterior cortex. Increased gamma power was observed for both anaesthetic agents at midline electrodes over the posterior cortex, but not anteriorly. Anaesthesia-induced delta and theta waves were differentially distributed along the anterior-posterior axis of the brain in a manner that corresponds well to the anatomy of putative neuronal generators. The distribution of anaesthetic-induced changes in fast gamma-band power seems to reflect functional differences between the posterior and anterior aspects of the cerebral cortex. These preliminary observations were consistent within our small sample, indicating that larger studies of anaesthetic effects using high-density recordings are warranted.
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Simons, A. J. R., E. H. J. F. Boezeman, and R. A. F. Pronk. "Automatic EEG monitoring of anaesthesia." Baillière's Clinical Anaesthesiology 3, no. 3 (1989): 623–46. http://dx.doi.org/10.1016/s0950-3501(89)80022-4.
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Grasso, Chiara, Vanessa Marchesini, and Nicola Disma. "Applications and Limitations of Neuro-Monitoring in Paediatric Anaesthesia and Intravenous Anaesthesia: A Narrative Review." Journal of Clinical Medicine 10, no. 12 (2021): 2639. http://dx.doi.org/10.3390/jcm10122639.
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Safe management of anaesthesia in children has been one of the top areas of research over the last decade. After the large volume of articles which focused on the putative neurotoxic effect of anaesthetic agents on the developing brain, the attention and research efforts shifted toward prevention and treatment of critical events and the importance of peri-anaesthetic haemodynamic stability to prevent negative neurological outcomes. Safetots.org is an international initiative aiming at raising the attention on the relevance of a high-quality anaesthesia in children undergoing surgical and non-surgical procedures to guarantee a favourable outcome. Children might experience hemodynamic instability for many reasons, and how the range of normality within brain autoregulation is maintained is still unknown. Neuro-monitoring can guide anaesthesia providers in delivering optimal anaesthetic drugs dosages and also correcting underling conditions that can negatively affect the neurological outcome. In particular, it is referred to EEG-based monitoring and monitoring for brain oxygenation.
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Whyte, Simon David, and Peter Driscoll Booker. "Monitoring depth of anaesthesia by EEG." BJA CEPD Reviews 3, no. 4 (2003): 106–10. http://dx.doi.org/10.1093/bjacepd/mkg106.
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Mori, K. "The EEG and awareness during anaesthesia." Anaesthesia 42, no. 11 (1987): 1153–55. http://dx.doi.org/10.1111/j.1365-2044.1987.tb05219.x.
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Gaskell, A., R. D. Sanders, and J. Sleigh. "Using EEG markers to titrate anaesthesia." British Journal of Anaesthesia 121, no. 1 (2018): 327–29. http://dx.doi.org/10.1016/j.bja.2018.04.003.
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Berkel, B., Z. Alanoglu, Y. Ates, O. SelviCan, and F. Tuzuner. "Quantative EEG monitored anaesthesia; cost comparison of three anaesthetic techniques management." European Journal of Anaesthesiology 24, Supplement 39 (2007): 17–18. http://dx.doi.org/10.1097/00003643-200706001-00064.
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Gupta, Nidhi, and Gyaninder Singh. "Electroencephalography-based monitors." Journal of Neuroanaesthesiology and Critical Care 02, no. 03 (2015): 168–78. http://dx.doi.org/10.4103/2348-0548.165030.
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AbstractAn electroencephalogram (EEG), detects changes and abnormalities in the electrical activity of the brain and thus provides a way to dynamically assess brain function. EEG may be used to diagnose and manage a number of clinical conditions such as epilepsy, convulsive and non-convulsive status epilepticus, encephalitis, barbiturate coma, brain death, etc., EEG provides a large amount of information to the anaesthesiologist for routine clinical practice as depth of anaesthesia monitors and detection of sub-clinical seizures; and also for understanding the complex mechanisms of anaesthesia-induced alteration of consciousness. In the initial years, the routine clinical applicability of EEG was hindered by the complexity of the raw EEG signal. However, with technological advancement, several EEG-derived dimensionless indices have been developed that correlate with the depth of the hypnotic component of anaesthesia and are easy to interpret. Similarly, with the development of quantitative EEG tools, the routine use of continuous EEG is ever expanding in the Intensive Care Units. This review, describe various commonly used EEG-based monitors and their clinical applicability in the field of anaesthesia and critical care.
Dissertations / Theses on the topic "Anaesthesia; EEG"
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Cox, Matthew Vernon. "Evaluation of EEG-based depth of anaesthesia monitoring." Thesis, University of Bristol, 2008. http://hdl.handle.net/1983/6040ef3f-9645-4192-afbc-3c8d046c3d21.
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In 2001 a University of Bristol team patented a novel data reduction method of the EEG for characterising categorical changes in consciousness. After pre-whitening the EEG signal with Gaussian white noise a parametric spectral estimation technique was applied. Two frequency domain indices were then proposed: the relative power found between 8Hz to 12Hz and 0.5Hz to 32Hz termed the 'alpha index', and the relative power between 0.5Hz to 4Hz and 0.5Hz to 32Hz termed the 'delta index'. The research and development of a precision EEG monitoring device designed to embody the novel algorithm is described in this thesis. The efficacy of the technique was evaluated using simulated and real EEG data recorded during Propofol anaesthesia. The simulated data showed improvements could be made to the patented method. Real EEG data collected whilst patients were wakeful and data from patients unresponsive to noxious stimuli were cleaned of obvious artefacts and analysed using the proposed algorithm. A Bayesian diagnostic test showed the alpha index had 65% sensitivity and selectivity to patient state. The delta index showed 72% sensitivity and selectivity. Taking a pragmatic approach, the literature is reviewed in this thesis to evaluate the use of EEG in depth of anaesthesia monitoring. Pertinent aspects of the sciences are profiled to identify physiological links to the characteristics of the EEG signal. Methods of data reduction are also reviewed to identify useful features and possible sources of error. In conclusion it is shown that the proposed indices do not provide a robust measure of depth of anaesthesia. An approach for further research is proposed based on the review work.
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Holt, Mark Rowan Gorton. "The use of neural networks in the analysis of the anaesthetic electroencephalogram." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390525.
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Lioi, Giulia. "EEG connectivity measures and their application to assess the depth of anaesthesia and sleep." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/420866/.
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General anaesthesia has been used for more than two centuries to guarantee unconsciousness, analgesia and immobility during surgery, yet our ability to evaluate the level of anaesthesia of the patient remains insufficient. This contributes on one hand to occasional episodes of intraoperative awareness and recall and on the other to ‘controlled’ drug over-dosage that increases hospital costs and patients recovery times. At present parameters used in clinical practice to monitor anaesthesia are indirect measures of the state of the brain, which is the target organ of anaesthetics. The lack of a reliable monitor of anaesthetic depth has led to considerable effort to develop new monitoring methods based on electrophysiological measurements. This progress has produced a series of depth of anaesthesia monitors based on various features of the electroencephalogram (EEG) signal. Even though these indexes are practically useful, their theoretical and physiological validity is poorly evidenced and they suffer from some practical limitations. As a result, their clinical uptake has been quite low. In recent years increasing attention has been given to brain connectivity as a powerful tool to investigate the complex behaviour of the brain. Theoretical and experimental findings have identified the disruption of brain connectivity as a crucial mechanism of anaesthetic-induced loss of consciousness. In this work a novel index of anaesthetic depth based on brain connectivity estimated from non-invasive scalp recordings (EEG) is proposed. Firstly, robust estimators of directed connectivity were identified in the framework of multivariate autoregressive (MVAR) models. With a series of simulation studies the performances of these methods in estimating causal connections were assessed in particular with respect to the deleterious effects of instantaneous connectivity due to volume conduction. Recently published solutions were also tested (and rejected). From a comparison of connectivity measurements in simulations, MVAR based estimators were most robust to the effects of volume conduction than conventional coherence measurements. Next the performances of directed connectivity estimators were tested in two experimental studies on NREM sleep and on anaesthesia. Features that exhibited the most robust changes with the individual level of consciousness were identified and their performances in discriminating wakefulness from anaesthesia tested on ten patients undergoing a slow induction of propofol anaesthesia. The performance of the proposed method were also compared with established depth of anaesthesia indexes such as Bispectral Index (BIS) or Auditory Evoked Potentials (AEP). Results suggest that EEG connectivity features are sensitive to the anaesthetic induced changes and that they have the potential to be integrated in future monitors of intra-operative awareness and anaesthetic adequacy.
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Sonkajärvi, E. (Eila). "The brain's electrical activity in deep anaesthesia:with special reference to EEG burst-suppression." Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526209722.
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Abstract Several anaesthetics are able to induce a burst-suppression (B-S) pattern in the electroencephalogram (EEG) during deep levels of anaesthesia. A burst-suppression pattern consists of alternating high amplitude bursts and periods of suppressed background activity. All monitors measuring the adequacy of anaesthesia recognize the EEG B-S as one criterion. A better understanding of EEG burst-suppression is important in understanding the mechanisms of anaesthesia. The aim of the study was to acquire a more comprehensive understanding of the function of neural pathways during deep anaesthesia. The thesis is comprised of four prospective clinical studies with EEG recordings from 64 patients, and of one experimental study of a porcine model of epilepsy with EEG registrations together with BOLD fMRI during isoflurane anaesthesia (II). In study I, somatosensory cortical evoked responses to median nerve stimulation were studied under sevoflurane anaesthesia at EEG B-S levels. In study III, The EEGs of three Parkinson`s patients were observed to describe the characteristics of B-S during propofol anaesthesia using scalp electrodes and depth electrodes in the subthalamic nucleus. In study IV, EEG topography was observed in 20 healthy children under anaesthesia mask induction with sevoflurane. Twenty male patients were randomized to either controlled hyperventilation or spontaneous breathing groups for anaesthesia mask induction with sevoflurane in study V. EEG alterations in relation to haemodynamic responses were examined in studies IV and V. Somatosensory information reached the cortex even during deep anaesthesia at EEG burst-suppression level. Further processing of these impulses in the cortex was suppressed. The EEG slow wave oscillations were synchronous over the entire cerebral cortex, while spindles and sharp waves were produced by the sensorimotor cortex. The development of focal epileptic activity could be detected as a BOLD signal increase, which preceded the EEG spike activity. The epileptogenic property of sevoflurane used at high concentrations especially during hyperventilation but also during spontaneous breathing together with heart rate increase, was confirmed in healthy children and male. Spike- and polyspike waveforms concentrated in a multifocal manner frontocentrally<br>Tiivistelmä Useat anestesia-aineet pystyvät aiheuttamaan aivosähkökäyrän (EEG) purskevaimentuman syvän anestesian aikana. Purskevaimentuma koostuu EEG:n suuriamplitudisten purskeiden sekä vaimentuneen taustatoiminnan vaihtelusta. Kaikkien anestesian syvyyttä mittaavien valvontalaitteiden toiminta perustuu osaltaan EEG:n purskevaimentuman tunnistamiseen. Tämän ilmiön parempi tunteminen on tärkeää anestesiamekanismien ymmärtämiseksi. Tutkimuksen päämääränä oli saada kattavampi käsitys hermoratojen toiminnasta syvässä anestesiassa. Väitöskirjatyö koostuu neljästä prospektiivisesta yhteensä 64 potilaan EEG-rekisteröinnit sisältävästä tutkimuksesta sekä yhdestä kokeellisen epilepsiatutkimuksen koe-eläintyöstä, jossa porsailla käytettiin isofluraanianestesiassa sekä EEG-rekisteröintejä sekä että magneettikuvantamista (fMRI) samanaikaisesti (II). Ensimmäisessä osatyössä tutkittiin keskihermon stimulaation aiheuttamia somatosensorisia herätepotentiaaleja aivokuorella EEG:n purskevaimentumatasolla sevofluraanianestesian aikana. Kolmannessa osatyössä selvitettiin propofolianestesian aiheuttamaa EEG:n purskevaimentumaa kolmelta Parkinsonin tautia sairastavalta potilaalta käyttäen sekä pintaelektrodien että subtalamisen aivotumakkeen syväelektrodien rekisteröintejä. Neljännessä osatyössä tutkittiin EEG:n topografiaa 20:llä terveeellä lapsella indusoimalla anestesia sevofluraanilla. Kaksikymmentä miespotilasta nukutettiin sevofluraanilla ja heidät satunnaistettiin joko kontrolloidun hyperventilaation tai spontaanin hengityksen ryhmiin osatyössä V. EEG-muutoksia sekä niiden yhteyttä verenkiertovasteisiin selviteltiin molemmissa osatöissä IV ja V. Omasta kehosta tuleviin tuntoärsykkeisiin liittyvä somatosensorinen informaatio saavutti aivokuoren myös syvässä EEG:n purskevaimentumatasoisessa anestesiassa. Impulssien jatkokäsittely aivokuorella oli kuitenkin estynyt. EEG:n hidasaaltotoiminta oli synkronista koko aivokuoren alueella, sen sijaan unisukkulat ja terävät aallot paikantuivat sensorimotoriselle aivokuorelle. Paikallisen epileptisen toiminnan kehittyminen oli mahdollista havaita jo ennen piikikkäiden EEG:n aaltomuotojen ilmaantumista edeltävänä BOLD-ilmiöön liittyvänä aivoverenkierron lisääntymisenä. Sevofluraanin epileptogeenisyys varmistui erityisesti hyperventilaation, mutta myös spontaanin hengityksen yhteydessä ja näihin liittyi sykkeen nousu sekä terveillä lapsilla että miehillä. Piikkejä ja monipiikkejä käsittävien aaltomuotojen keskittymistä esiintyi otsalohkon keskialueilla
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Murrell, Joanna. "Spontaneous EEG changes in the equine surgical patient." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340352.
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Sheffy, Jacob. "Recording of diaphragm activity during anaesthesia." Thesis, Oxford Brookes University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261673.
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Conceição, Elaine Dione Venêga da. "Infusão contínua de propofol associado ao fentanil ou sufentanil em cadelas submetidas a ovariosalpingo-histerectomia /." Jaboticabal : [s.n.], 2006. http://hdl.handle.net/11449/101135.
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Orientador: Newton Nunes<br>Banca: Juliana Noda Bechara Belo<br>Banca: Paulo Sérgio Patto dos Santos<br>Banca: Carlos Augusto Araújo Valadão<br>Banca: José Antonio Marques<br>Resumo: Avaliaram-se os efeitos da infusão contínua de propofol em associação ao fentanil ou sufentanil sobre a hemodinâmica, eletrocardiografia e índice biespectral em cadelas submetidas à ovariosalpingo-histerectomia. Para tal, foram utilizadas 20 cadelas hígidas, induzidas à anestesia geral com 10 mg/kg de propofol. Após a intubação com sonda orotraqueal de Magill, receberam suporte ventilatório com oxigênio a 100% e fluxo de 15 mUkg/min em circuito fechado, ciciado no modo pressão controlada, mantendo-se a ventilação a pressão positiva intermitente. A manutenção anestésica foi realizada com a administração de O,4mglkglmin de propofol e foram distribuídos em dois grupos de 10 animais que receberam 5J,lglkg de fentanil (GPF) ou 1J,lg/kg de sufentanil (GPS) por via intravenosa, seguida de infusão contínua... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: Possible effects of the continuous infusion of propofol associated with fentanyl or sufentanil on haemodynamic, blood gas analysis, electrocardiography and bispectral index in female dogs, submitted to the surgical procedure of ovariosalpingohysterectomy, were evaluated. Twenty healthy female dogs were used and general anesthesia was induced with 10mglkg of propofol. They received ventilatory support with 100% oxygen and a 15 mUkg/min flow in a cIosed circuit, cycled with controlled pressure. Ali animais were submitted to total intravenous anesthesia with propotol (O.4mg/kglmin) and distributed in two groups of ten animais each one. They received 5J.1glkg of fentanyl (GPF) or 1J.1g1kg of sufentanil... (Complete abstract click electronic access below)<br>Doutor
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Hashemi, Meysam. "Modélisation mathématique et simulation numérique de populations neuronales thalamo-corticales dans le contexte de l'anesthésie générale." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0014/document.
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Bien que l’anesthésie générale soit un outil indispensable dans la chirurgie médicale d’aujourd’hui, ses mécanismes sous-jacents précis sont encore inconnus. Au cours de la sédation induite par le propofol les actions anesthésiques à l’échelle microscopique du neurone isolé conduisent à des changements spécifiques à l’échelle macroscopique qui sont observables comme les signaux électroencéphalogrammes (EEG). Pour une concentration faible en propofol, ces changements caractéristiques comprennent une augmentation de l’activité dans les bandes de fréquence delta (0.5-4 Hz) et alpha (8 13 Hz) dans la région frontal, une l’activité augmentée de delta et une l’activité diminuée de alpha dans la région occipitale. Dans cette thèse, nous utilisons des modèles de populations neuronales thalamo-corticales basés sur des données expérimentales. Les effets de propofol sur les synapses et sur les récepteurs extra-synaptiques GABAergiques situés dans le cortex et le thalamus sont modélisés afin de comprendre les mécanismes sous-jacents aux changements observés dans certaines puissances de l’EEG spectrale. Il est démontré que les modèles reproduisent bien les spectrales caractéristiques observées expérimentalement. Une des conclusions principales de ce travail est que l’origine des delta rythmes est fondamentalement différente de celle des alpha rythmes. Nos résultats indiquent qu’en fonction des valeurs moyennes des potentiels de l’état du système au repos, une augmentation ou une diminution des fonctions de gain thalamo-corticale résulte respectivement en une augmentation ou une diminution de alpha puissance. En revanche, l’évolution de la delta puissance est plutôt indépendant de l’état du système au repos; l'amélioration de la puissance spectrale de delta bande résulte de l’inhibition GABAergique synaptique ou extra-synaptique pour les fonctions de gain non linéaire à la fois croissante et décroissante. De plus, nous cherchons à identifier les paramètres d’un modèle de thalamo-corticale en ajustant le spectre de puissance de modèle pour les enregistrements EEG. Pour ce faire, nous considérons la tâche de l’estimation des paramètres dans les modèles qui sont décrits par un ensemble d’équations différentielles ordinaires ou bien stochastiques avec retard. Deux études de cas portant sur des données pseudo-expérimentales bruyantes sont d’abord effectuées pour comparer les performances des différentes méthodes d’optimisation. Les résultats de cette élaboration montrent que la méthode utilisée dans cette étude est capable d’estimer avec précision les paramètres indépendants du modèle et cela nous permet d’éviter les coûts de calcul des intégrations numériques. En considérant l’ensemble, les conclusions de cette thèse apportent de nouveaux éclairages sur les mécanismes responsables des changements spécifiques qui sont observées pendant la sédation propofol-induite dans les modèles de EEG<br>Although general anaesthesia is an indispensable tool in today’s medical surgery, its precise underlying mechanisms are still unknown. During the propofol-induced sedation, the anaesthetic actions on the microscopic single neuron scale lead to specific changes in macroscopic-scale observables such as electroencephalogram (EEG) signals. For low concentration of propofol these characteristic changes comprised increased activity in the delta (0.5-4 Hz) and alpha (8-13 Hz) frequency bands over the frontal head region, but increased delta and decreased alpha power activity over the occipital region. In this thesis, we employ thalamo-cortical neural population models, and based on the experimental data, the propofol effects on the synaptic and extrasynaptic GABAergic receptors located in the cortex and thalamus are modelized to understand the mechanisms underlying the observed certain changes in EEG-spectral power. It is shown that the models reproduce well the characteristic spectral features observed experimentally. A key finding of this work is that the origin of delta rhythm is fundamentally different from the alpha rhythm. Our results indicate that dependent on the mean potential values of the system resting states, an increase or decrease in the thalamo-cortical gain functions results in an increase or decrease in the alpha power, respectively. In contrast, the evolution of the delta power is rather independent of the system resting states; the enhancement of spectral power in the delta band results from the increased synaptic or extra-synaptic GABAergic inhibition for both increasing and decreasing nonlinear gain functions. Furthermore, we aim to identify the parameters of a thalamo-cortical model by fitting the model power spectrum to the EEG recordings. To this end, we address the task of parameter estimation in the models that are described by a set of stochastic ordinary or delay differential equations. Two case studies dealing with noisy pseudo-experimental data are first carried out to compare the performance of different optimization methods. The results of this elaboration show that the method used in this study is able to accurately estimate the independent model parameters while it allows us to avoid the computational costs of the numerical integrations. Taken together, the findings of this thesis provide new insights into the mechanisms responsible for the specific changes in EEG patterns that are observed during propofol-induced sedation
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Gabas, Daniela Tozadore. "Determinação da concentração alveolar mínima(CAM) de sevofluorano em filhotes de cães (neonatos e pediátricos) /." Botucatu : [s.n.], 2008. http://hdl.handle.net/11449/105643.
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Orientador: Valéria Nobre Leal de Souza Oliva<br>Banca: Paulo Sérgio Patto dos Santos<br>Banca: Renata Navarro Cassu<br>Banca: Stélo Pacca Loureiro Luna<br>Banca: Juliana Noda Bechara Belo<br>Resumo: Há controvérsia na literatura sobre a determinação do período exato que corresponde à classificação dos pacientes caninos em neonatos ou pediátricos. Contudo, sabe-se que até 6 semanas de idade estes animais apresentam imaturidade do sistema respiratório, cardiovascular, sistema nervoso central, hepático e renal. Tal imaturidade dos sistemas pode interferir na disponibilidade dos fármacos e na resposta destes à anestesia. Alguns fatores influenciam diretamente a concentração alveolar mínima (CAM) dos anestésicos inalatórios sendo a idade um destes. Há escassa literatura a respeito da influencia da idade na CAM dos anestésicos inalatórios. Desta maneira, este trabalho tem o objetivo de determinar a concentração alveolar mínima (CAM) do sevofluorano em cães jovens nas diferentes faixas etárias pré-determinadas pelos pesquisadores. Foram utilizados oito filhotes de cães, da raça Retriever do Labrador, submetidos à anestesia inalatória com sevofluorano aos 30, 45, 60 e 90 (± 2) dias de idade. A monitoração foi composta de freqüência cardíaca, freqüência respiratória, pressão arterial sistólica não-invasiva, oximetria de pulso, hemogasometria arterial e temperatura retal, concentração de sevofluorano (ETsev) e dióxido de carbono (ETco2) no final da expiração. A ETsev ao final da expiração foi mantida em 3% por no mínimo 15 minutos para a realização do estímulo supramáximo doloroso e determinação da CAM que constitiu-se em pinçamento de cauda durante 60 segundos ou menos, caso a resposta fosse positiva. Quando a resposta ao primeiro estímulo fosse negativa, a concentração de sevofluorano foi diminuída em 0,2% em relação a concentração inicial (3%) e o estímulo foi repetido após 15 minutos, para possibilitar a estabilização do circuito. Se, inicialmente... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: In the literature we researched certain difficulty could be noted in the determination of the exact period for the classification of canine patients in neonates and pediatrics. However, it is anyway known that until 6 weeks of age these animals have very immature respiratory, cardiovascular, central nervous system, hepatic, and renal systems. Such immaturity of their organic systems may interfere in the drug disponibility and reaction, as well as in their reaction to the anaesthesic agent. Some factors interfere directly in the minimum alveolar concentration (MAC) of inhalant anaesthesics, and age is certainly one of them. There is a shortage of studies about age influence over MAC of inhalant anaesthesical agents. So, this work is aimed to determine the minimum alveolar concentration (MAC) of sevoflurane in young dogs, divided in different age groups by researchers. Eight Labrador Retriever baby dogs underwent inhalant anaesthesia with sevoflurane in the ages of 30, 45, 60 and 90 (+/-2) days. The checkup included heart and breath frequencies, non-invasive systolical blood pressure pulse oximetry, arterial blood gas and rectal temperature, sevoflurane (ETsev) and carbon dioxide (ETCO2) concentrations in the end of the expiration. ETsev in the end of expiration was kept at 3% for at least 15 minutes for the accomplishment of the pain stimulus and MAC determination. For that, dogs were stimulated with tail clamping during 60 seconds or less, whether reaction were positive. When the reaction to the first stimulation were negative, sevoflurane concentration was decreased in 80% of its initial concentration (1.5 MAC), as well as the stimulus was repeated after 15 minutes, in order to stabilise the circuit. Whether in the beginning the answer were positive, the anaesthesic concentration was then increased in 20% and after 15 minutes a new stimulation was tried. This scheming was repeated as many times as it was necessary to achieve the negative.<br>Doutor
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Lee, Angela. "Brain State Classification in Epilepsy and Anaesthesia." Thesis, 2010. http://hdl.handle.net/1807/25750.
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Transitions between normal and pathological brain states are manifested differently in the electroencephalogram (EEG). Traditional discrimination of these states is often subject to bias and strict definitions. A fuzzy logic-based analysis can permit the classification and tracking of brain states in a non-subjective and unsupervised manner. In this thesis, the combination of fuzzy c-means (FCM) clustering, wavelet, and information theory has revealed notable frequency features in epilepsy and anaesthetic-induced unconsciousness. It was shown that entropy changes in membership functions correlate to specific epileptiform activity and changes in anaesthetic dosages. Seizure episodes appeared in the 31-39 Hz band, suggesting changes in cortical functional organization. The induction of anaesthetics appeared in the 64-72 Hz band, while the return to consciousness appeared in the 32-40 Hz band. Changes in FCM activity were associated with the concentration of anaesthetics. These results can help with the treatment of epilepsy and the safe administration of anaesthesia.
Books on the topic "Anaesthesia; EEG"
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Luginbühl, Martin, and Arvi Yli-Hankala. Assessment of the components of anaesthesia. Edited by Antony R. Wilkes and Jonathan G. Hardman. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0026.
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In modern anaesthesia practice, hypnotic drugs, opioids, and neuromuscular blocking agents (NMBAs) are combined. The introduction of NMBAs in particular substantially increased the risk of awareness and recall during general anaesthesia. Hypnotic drugs such as propofol and volatile anaesthetics act through GABAA receptors and have typical effects on the electroencephalogram (EEG). During increasing concentrations of these pharmaceuticals, the EEG desynchronization is followed by gradual synchronization, slowing frequency, and increasing amplitude of EEG, thereafter EEG suppressions (burst suppression), and, finally, isoelectric EEG. Hypnotic depth monitors such as the Bispectral Index™, Entropy™, and Narcotrend® are based on quantitative EEG analysis and translate these changes into numbers between 100 and 0. Although they are good predictors of wakefulness and deep anaesthesia, their usefulness in prevention of awareness and recall has been challenged, especially when inhalation anaesthetics are used. External and patient-related artifacts such as epileptiform discharges and frontal electromyography (EMG) affect the signal so their readings need careful interpretation. Their use is recommended in patients at increased risk of awareness and recall and in patients under total intravenous anaesthesia. Monitors of analgesia and nociception are not established in clinical practice but mostly remain experimental although some are commercially available. Some use EEG changes induced by noxious stimulation (EEG arousal) or quantify the frontal EMG in relation to EEG, while others are based on the sympathoadrenergic stress response. Various other devices are also discussed in this chapter.
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Jakobsson, Jan. Anaesthesia for day-stay surgery. Edited by Philip M. Hopkins. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0068.
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Day-stay surgery is becoming increasingly common the world over. There are several benefits of avoiding in-hospital care. Early ambulation reduces the risk for thromboembolic events, facilitates wound healing, and avoiding admission reduces the risk for hospital-related infection. Additionally, the risk of neurocognitive side-effects can be avoided by returning the elderly patient to their home environment. Day-stay anaesthesia calls for adequate and structured preoperative assessment and patient evaluation, and the potential risk associated with surgery and anaesthesia should be assessed on an individual basis. Need for preoperative testing should be based on functional status of the patient and preoperative medical history but even the surgical procedure should be taken into account. Preoperative fasting should be in accordance with modern guidelines, refraining from food for 6 hours and fluids for 2 hours prior to induction in low-risk patients. Preventive analgesia and prophylaxis of postoperative nausea and vomiting (PONV) should be administered preoperatively. Local anaesthesia should be administered prior to incision, constituting part of multimodal analgesia. The multimodal analgesia strategy should also include paracetamol and a non-steroidal anti-inflammatory drug in order to reduce the noxious stimulus from the surgical field. Third-generation inhaled anaesthetics or a propofol-based maintenance are both feasible alternatives. Titrating depth of anaesthesia by using an EEG-based depth of anaesthesia monitor may facilitate the recovery process. The laryngeal mask airway has become commonly used and has several advantages. Ultrasound-guided peripheral blocks may facilitate the early postoperative course by reducing pain and avoiding the use of opiates. Perineural catheters may be an option for prolongation of the block following painful orthopaedic procedures but a strict protocol and follow-up must be secured. Not only pain but even nausea and vomiting should be prevented, and therefore risk stratification, for example by the Apfel score, and PONV prophylaxis in accordance with the risk score is strongly recommended. Early ambulation should be encouraged postoperatively. Safe discharge should include an escort who also remains at home during the first postoperative night. Analgesics should be provided and be readily available for self-care when the patient comes home. Pain medication should include an opioid; however, the benefit versus risk must be assessed on an individual basis. Patients should also be instructed about a rescue return-to-hospital plan. Quality of care should include follow-up and analysis of clinical practice, and institution of methods to improve quality should be enforced for the benefit of the ambulatory surgical patient.
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Walker, Matthew C. Convulsive and non-convulsive status epilepticus. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199688395.003.0030.
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This chapter describes the definition, epidemiology, classification, diagnosis, and treatment of status epilepticus, concentrating on the roles that electroencephalography (EEG) plays. The term status epilepticus now encompasses a range of conditions from continuous convulsive seizures to clinically subtle non-convulsive seizures, which may manifest as changes in behaviour or personality. EEG is critical for the diagnosis of non-convulsive status epilepticus. Furthermore, the progression of convulsive status epilepticus is to an electromechanical dissociation in which continuous electrical seizure activity may have no or minimal clinical manifestations. In the later stages of status epilepticus, EEG is necessary to monitor treatment, but is confounded by the interpretation of periodic EEG patterns, which represent a continuum from interictal through to ictal activity. Post-status epilepticus EEG patterns have prognostic value: periodic epileptiform discharges, burst suppression patterns (off anaesthesia) and repetitive seizure activity are indicative of a poor long-term prognosis.
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Prout, Jeremy, Tanya Jones, and Daniel Martin. Obstetric anaesthesia. Oxford University Press, 2014. http://dx.doi.org/10.1093/med/9780199609956.003.0024.
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This chapter covers the knowledge required for higher training in obstetric anaesthesia. Physiological changes of pregnancy, along with their relevance to anaesthetic management are highlighted. Common maternal comorbidity and the impact on antenatal course, delivery and anaesthesia are summarized. Modern labour analgesia techniques are compared. Anaesthetic management of common obstetric emergencies e.g. fetal distress, preeclampsia, massive haemorrhage, abnormal placentation, amniotic fluid embolus and uterine inversion are described. Finally, the recent Confidential Enquiry into Maternal Death is summarized along with the role of early warning scores to improve future care.
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Phillips, Alistair, and Harry Akerman. Anaesthesia. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198757689.003.0003.
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Pain-free surgery can be imposed on the hand and wrist without resort to general anaesthetic. Options include local anaesthetic infiltration which can, in higher volumes mixed with adrenaline, allow surgery without a tourniquet. This technique (wide awake local anaesthetic without tourniquet or WALANT) permits the patient to move the fingers without the muscle paralysis induced by the regional anaesthetic and tourniquet, adding invaluable information, e.g. in tendon transfers. The efficacy of specific peripheral nerve blockade and brachial plexus block can be enhanced by ultrasound or nerve stimulation. Intravenous blockade (Bier’s) is effective. Tourniquets (finger, forearm, above elbow) are essential in hand surgery to provide a view unimpeded by blood (although WALANT can achieve this at the expense of a more oedematous field for procedures in a small field).
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Craven, Rachael, Hilary Edgcombe, and Ben Gupta, eds. Global Anaesthesia. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198809821.001.0001.
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The Oxford Specialist Handbook of Global Anaesthesia is an authoritative and comprehensive reference tool for anaesthetists practising in low-resource settings. It provides essential information to trained anaesthetists on delivering care without the equipment, drugs, and colleague support they might be used to in high-resource settings. Written by international experts in the field it will be useful to anaesthetists planning to work in remote and rural areas or countries with poor healthcare resources. It will also be useful to those working as part of disaster and emergency response medical teams. The technical and organizational aspects of delivering anaesthesia in austere environments are addressed, as are drugs and equipment that might be unfamiliar to anaesthetists practising in high-resource settings, e.g. ketamine and draw-over anaesthesia. The sub-specialties of obstetrics, paediatrics, burns, pain, trauma, and critical care are all covered in the clinical section. Useful reference tables, including a drug formulary, ensure that this book is the essential ‘survival guide’ for any trained anaesthetic practitioner planning to work or teach in a remote or resource-poor environment.
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Collis, Rachel, Sarah Harries, and Abrie Theron, eds. Obstetric Anaesthesia. 2nd ed. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780199688524.001.0001.
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Starting work on the labour ward is very challenging for all junior anaesthetists. This handbook is an easily navigated practical reference guide for anaesthetists new to this environment, as well as other members of the labour ward multi-disciplinary team; midwives, obstetricians, and Consultant Anaesthetists who visit labour ward less frequently or only when on-call. It covers all aspects of obstetric anaesthesia that the trainee anaesthetist will encounter during their obstetric training module, and is essential reading for FRCA exam preparation. Since the first edition, there is no doubt that the pregnant population has become more complex, with increasing maternal age and BMI, and challenging co-morbidities presenting more frequently. As well as providing updates from recent MBRRACE reports and national guidelines, new techniques, drugs, and technology, such as point of care testing have been included. New chapters covering the application of ultrasound in obstetric anaesthesia, recognition of the sick and septic patient, maternal obesity and neonatal resuscitation have been introduced. Previous chapters, e.g. haemorrhage, have been extensively updated, with the latest management protocols and algorithms based on recent published research in obstetric bleeding. We have retained our practical guides to performing, managing, and trouble-shooting regional techniques that are more problematic on labour ward, and our extensive A–Z of rarer conditions has updated references. More conventional chapters on maternal physiology and pathophysiology provide readers with essential examination material. The importance of anticipating risk in the antenatal period through high risk anaesthetic assessment clinics and postpartum management of tricky neurological complications is also well covered.
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Wilkes, Antony R. Equipment in anaesthesia. Edited by Antony R. Wilkes and Jonathan G. Hardman. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0024.
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The anaesthetist will routinely use many different types of medical devices during normal working practice, and will have access to many other devices for more challenging use in emergency and other difficult scenarios. The anaesthetist will expect and rely on each medical device to work first time and not to compromise the safety of the user, the patient, their relatives, or other healthcare workers in the vicinity. The equipment will also be expected to be effective, that is, that it will perform as expected when used in a defined population of patients (e.g. small children). Manufacturers and users of equipment use risk management procedures to reduce the risk to patients and others of using the equipment. Following use, the equipment will need to be reprocessed to make it safe for use for a subsequent patient, or disposed of safely.
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Bodenham, Andrew R. Vascular access during anaesthesia. Edited by Michel M. R. F. Struys. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0049.
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Vascular access, both arterial and venous, at peripheral and more central sites is relatively new in historical medical terms and has only really developed into mainstream practice in the last 60 years. Other routes of drug and fluid administration via the gut and inhalation preceded it by centuries. It is a core skill for anaesthetists and intensivists, yet is not always well taught or is left out of core training curricula, with the assumption that skills will just be picked up early along the way. Like many procedures, it can be surprisingly easy to learn the basics, but many hazards and difficulties await the less skilled or inexperienced operator. A thorough knowledge of applied anatomy, practical skills, and recognition and management of complications are essential for safe practice. The increasing use of ultrasound, ECG guidance, X-ray screening, and other devices, and improved design of access devices allow much safer and more successful procedures. Many patients will now have long-term devices in situ, which can be used during anaesthesia and critical care. Such devices are increasingly inserted or removed by anaesthetists. Space precludes a detailed description of actual techniques for all routes of access; only general principles will be covered in this chapter.
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Brandt, Sebastian, and Hartmut Gehring. Anaesthesia for medical imaging and bronchoscopic procedures. Edited by Peter F. Mahoney and Michel M. R. F. Struys. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0077.
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Anaesthesia in ‘remote areas’ is required for medical imaging (CT, MRI, PET-CT), angiography, endoscopy, and interventions (stenting, thrombectomy, coiling, laser therapy, biopsies, radiotherapy) in a number of medical disciplines (paediatrics, radiology, cardiology, pulmonology, gastroenterology, surgery, cardiac surgery, emergency medicine). The spectrum of anaesthetic techniques is broad. It reaches from standby (monitored anaesthesia care), through analgesia and sedation (with spontaneous breathing), to general anaesthesia and mechanical ventilation. Regional anaesthesia techniques are also required under certain circumstances. In the last few years there has been a move away from open procedures to interventional techniques. The complexity of these interventions has increased (i.e. interventional cardiac valve replacements) and the patients tend to be older and suffer from a multitude of co-morbidities. Many of these interventions are performed in the ‘hostile environment’ of the intervention suite. Intervention suites are typically not designed to offer anaesthetists an ideal working area. The space may be limited and medical equipment impedes access to the patient. The infrastructure may be suboptimal (e.g. no central medical gases supply). Protection for staff and equipment against radiation and high magnetic fields must be considered. Loud noise from machinery and shielded walls, doors, and windows may hinder communication and hearing acoustic alarms. The distance to the operating theatre may be considerable and thus support from senior anaesthetists and supply of additional equipment may take some time to arrive. Anaesthesia outside the operating theatre is sometimes underestimated as trivial. Performing a ‘quick’ interventional case can evolve within seconds into a challenge even for the experienced anaesthesiologist if a surgical or anaesthesiological complication occurs. Non-operating-theatre anaesthesia has a higher severity of injuries and more substandard care than operating theatre anaesthesia. This is not acceptable and anaesthetists must ensure the same high standard of anaesthesia care and patient safety both inside and outside the operating theatre.
Book chapters on the topic "Anaesthesia; EEG"
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Bovill, J. G. "The EEG and Evoked Potentials." In Cardiac Anaesthesia: Problems and Innovations. Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4265-3_3.
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Schüttler, J., and H. Schwilden. "Feedback Control of Intravenous Anesthetics by Quantitative EEG." In Control and Automation in Anaesthesia. Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79573-2_19.
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Billard, V., and S. L. Shafer. "Does the EEG Measure Therapeutic Opioid Drug Effect?" In Control and Automation in Anaesthesia. Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79573-2_7.
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Petersen, Jörg, Gudrun Stockmanns, and Werner Nahm. "EEG Analysis for Assessment of Depth of Anaesthesia." In Fuzzy Systems in Medicine. Physica-Verlag HD, 2000. http://dx.doi.org/10.1007/978-3-7908-1859-8_12.
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Schwilden, H., and J. Schüttler. "Model-Based Adaptive Control of Volatile Anesthetics by Quantitative EEG." In Control and Automation in Anaesthesia. Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79573-2_16.
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Martínez-Vázquez, Pablo, Pedro L. Gambús, and Erik Weber Jensen. "Processed EEG as a Measure of Brain Activity During Anaesthesia." In Understanding Complex Systems. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-59805-1_24.
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Rating, W. "Frontal EEG/EMG Analysis: A Method of Assessing Depth of Anaesthesia. First Experience with an “Anaesthesia and Brain Activity Monitor”." In Anaesthesia — Innovations in Management. Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-82392-3_34.
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Bowles, S. M., P. S. Sebel, V. Saini, and N. Chamoun. "Effects of anaesthesia on the EEG — bispectral analysis correlates with movement." In Handbook of Spinal Cord Monitoring. Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1416-5_35.
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Olejarczyk, E., A. Sobieszek, R. Rudner, et al. "Characteristic features of the EEG patterns during anaesthesia evoked by fluorinated inhalation anaesthetics." In IFMBE Proceedings. Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-89208-3_301.
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Hutt, A. "A Neural Population Model of the Bi-phasic EEG-Power Spectrum During General Anaesthesia." In Sleep and Anesthesia. Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4614-0173-5_10.
Full textConference papers on the topic "Anaesthesia; EEG"
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Nguyen-Ky, T., Peng Wen, Yan Li, and Robert Gray. "De-noising a raw EEG signal and measuring depth of anaesthesia for general anaesthesia patients." In 2010 IEEE/ICME International Conference on Complex Medical Engineering. CME 2010. IEEE, 2010. http://dx.doi.org/10.1109/iccme.2010.5558834.
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Gurkan, Guray, Atilla Uslu, Bora Cebeci, et al. "Topographic and temporal spectral analysis of EEG signals during anaesthesia." In 2010 15th National Biomedical Engineering Meeting (BIYOMUT 2010). IEEE, 2010. http://dx.doi.org/10.1109/biyomut.2010.5479800.
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Gifani, P., H. R. Rabiee, M. H. Hashemi, S. Momenzadeh, P. Taslimi, and M. Ghanbari. "Power-law correlation in human EEG at various anaesthesia depths." In IET 3rd International Conference MEDSIP 2006. Advances in Medical, Signal and Information Processing. IEE, 2006. http://dx.doi.org/10.1049/cp:20060377.
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Castro, Ana, Nadja Bressan, Luis Antunes, and Catarina S. Nunes. "EEG entropy monitoring of depth of anaesthesia: Pharmacokinetic and dynamic modelling." In European Control Conference 2007 (ECC). IEEE, 2007. http://dx.doi.org/10.23919/ecc.2007.7068363.
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NAHM, W., E. KOCHS, G. STOCKMANNS, P. BISCHOFF, J. ABKE, and E. KONECNY. "DETECTION AND QUANTIFICATION OF PHASECOUPLING IN ANAESTHESIA-EEG BY BICOHERENCE SPECTRAL ANALYSIS." In Proceedings of the Fourth International Symposium. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2000. http://dx.doi.org/10.1142/9781848160231_0004.
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PRICHEP, L. S., E. R. JOHN, L. D. GUGINO, W. KOX, and R. J. CHABOT. "QUANTITATIVE EEG ASSESSMENT OF CHANGES IN THE LEVEL OF SEDATION/HYPNOSIS DURING SURGERY UNDER GENERAL ANAESTHESIA." In Proceedings of the Fourth International Symposium. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2000. http://dx.doi.org/10.1142/9781848160231_0008.
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Griffiths, M. J. "Recent advances in EEG monitoring for general anaesthesia, altered states of consciousness and sports performance science." In 3rd IEE International Seminar on Medical Applications of Signal Processing. IEE, 2005. http://dx.doi.org/10.1049/ic:20050322.
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Krkic, M. "EEG-based assessment of anaesthetic depth using neural networks." In IEE Colloquium on Artificial Intelligence Methods for Biomedical Data Processing. IEE, 1996. http://dx.doi.org/10.1049/ic:19960645.
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Lowe, G. D. O. "EPIDEMIOLOGY AND RISK PREDICTION OF VENOUS THROMBOEMBOLISM." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642965.
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Uses of epidemiology. Venous thromboembolism continues to be an important cause of death and disability in Western Countries. Its epidemiology may provide clues to etiology, e.g. the increased incidence in oral contraceptive users, and the low prevalence at autopsy in Central Africa or Japan compared to the U.S.A. A second use is the monitoring of time-trends: the diagnosis of pulmonary embolism increased during the 1970s, although the case fatality decreased. A third use is the identification and quantification of risk factors: these could be modified in the hope of prevention, or else used to select high risk groups for selective prophylaxis, e.g. during acute illness. Prevention is the only feasible approach to reducing the burden of venous thromboembolism, since most cases are not diagnosed, and since the value of current treatment is debatable.Case definition. Presents problems: clinical diagnosis is unreliable, and should if possible be supported by objective methods. Autopsy studies are performed on selected populations, at a decreasing rate; the frequency of thromboembolism depends on technique; and pathologists cannot be blinded and are open to bias. It can also be difficult to judge whether a patient dying with pulmonary embolism died from pulmonary embolism. 125I-fibrinogen scans indicate minimal disease, and now present ethical problems in screening due to risks of viral transmission. Venography is invasive and is not readily repeatable, which limits its use as a screening method. Plethysmography merits wider evaluation, since it is non-invasive, and sensitive to major thrombosis.Community epidemiology. Data on the community epidemiology are limited. The risk increases with age. When age is taken into account, there is little sex difference. Overweight in women, use of oral contraceptives and blood group A increase the risk: smoking, varicose veins, blood pressure, cholesterol and glucose do not, on current evidence. Long-term follow-up of patients with proven thromboembolism shows an increased risk of malignancy, hence occult cancer may also be a risk factor. Polycythaemia and certain congenital deficiencies (e.g. antithrombin III) are also well-recognised risk factors, although uncommon.Hospital epidemiology. Data on hospital epidemiology are derived largely from autopsy prevalence, and from short-term incidence of minimal thrombosis detected by 125I—fibrinogen scanning. Old, immobile and traumatised patients are most at risk. Previous thromboembolism, polycythaemia, antithrombin III deficiency, hip and leg fractures, elective hip and leg surgery, hemiplegia, paraplegia, and heart failure carry high risks, and merit consideration for routine prophylaxis. The risk in elective surgery precedes the operation, and increases with age, overweight, malignancy, varicose veins, non-smoking, and operative factors (duration, approach, general anaesthesia, intravenous fluids). Diabetics appear to have no extra risk. Combinations of clinical variables can be used to predict high risk groups for selective prophylaxis, but combination indices require further study. Laboratory variables may increase the predictability of deep vein thrombosis, but the results of published studies are conflicting, and the cost-effectiveness of laboratory prediction should be evaluated.