Interet de la surveillance et de l'analyse de l'electroencephalogramme au cours de l'anesthesie.
; Bonhomme, Vincent
in Revue medicale de Liege (2014), 69 Spec No
Electroencephalography (EEG) records brain electrical activity at the scalp level. As a functional and non invasive witness of brain activity, EEG has long raised the interest of researchers and ... [more ▼]
Electroencephalography (EEG) records brain electrical activity at the scalp level. As a functional and non invasive witness of brain activity, EEG has long raised the interest of researchers and practitioners, notably in the domain of anesthesia. Thanks to technical advances, this complex signal can now be dissected, and a huge amount of information can be extracted from it. This information gives the opportunity to quantify theeffects of general anesthesia on the brain, and provides a better understanding of the underlying mechanisms. [less ▲]Detailed reference viewed: 18 (3 ULg)
How electroencephalography serves the anesthesiologist.
Marchant, Nicolas ; ; et al
in Clinical EEG and neuroscience (2014), 45(1), 22-32
Major clinical endpoints of general anesthesia, such as the alteration of consciousness, are achieved through effects of anesthetic agents on the central nervous system, and, more precisely, on the brain ... [more ▼]
Major clinical endpoints of general anesthesia, such as the alteration of consciousness, are achieved through effects of anesthetic agents on the central nervous system, and, more precisely, on the brain. Historically, clinicians and researchers have always been interested in quantifying and characterizing those effects through recordings of surface brain electrical activity, namely electroencephalography (EEG). Over decades of research, the complex signal has been dissected to extract its core substance, with significant advances in the interpretation of the information it may contain. Methodological, engineering, statistical, mathematical, and computer progress now furnishes advanced tools that not only allow quantification of the effects of anesthesia, but also shed light on some aspects of anesthetic mechanisms. In this article, we will review how advanced EEG serves the anesthesiologist in that respect, but will not review other intraoperative utilities that have no direct relationship with consciousness, such as monitoring of brain and spinal cord integrity. We will start with a reminder of anesthestic effects on raw EEG and its time and frequency domain components, as well as a summary of the EEG analysis techniques of use for the anesthesiologist. This will introduce the description of the use of EEG to assess the depth of the hypnotic and anti-nociceptive components of anesthesia, and its clinical utility. The last part will describe the use of EEG for the understanding of mechanisms of anesthesia-induced alteration of consciousness. We will see how, eventually in association with transcranial magnetic stimulation, it allows exploring functional cerebral networks during anesthesia. We will also see how EEG recordings during anesthesia, and their sophisticated analysis, may help corroborate current theories of mental content generation. [less ▲]Detailed reference viewed: 48 (2 ULg)
Changes in Effective Connectivity by Propofol Sedation
Gomez Jaramillo, Francisco Albeiro ; Phillips, Christophe ; Soddu, Andrea et al
in PLoS ONE (2013), 8(8), 71370
Mechanisms of propofol-induced loss of consciousness remain poorly understood. Recent fMRI studies have shown decreases in functional connectivity during unconsciousness induced by this anesthetic agent ... [more ▼]
Mechanisms of propofol-induced loss of consciousness remain poorly understood. Recent fMRI studies have shown decreases in functional connectivity during unconsciousness induced by this anesthetic agent. Functional connectivity does not provide information of directional changes in the dynamics observed during unconsciousness. The aim of the present study was to investigate, in healthy humans during an auditory task, the changes in effective connectivity resulting from propofol induced loss of consciousness. We used Dynamic Causal Modeling for fMRI (fMRI-DCM) to assess how causal connectivity is influenced by the anesthetic agent in the auditory system. Our results suggest that the dynamic observed in the auditory system during unconsciousness induced by propofol, can result in a mixture of two effects: a local inhibitory connectivity increase and a decrease in the effective connectivity in sensory cortices. [less ▲]Detailed reference viewed: 426 (13 ULg)
Thalamus, Brainstem and Salience Network Connectivity Changes During Propofol-Induced Sedation and Unconsciousness
Guldenmund, Justus Pieter ; Demertzi, Athina ; BOVEROUX, Pierre et al
in Brain connectivity (2013), 3
In this functional magnetic resonance imaging study, we examined the effect of mild propofol sedation and propofol-induced unconsciousness on resting state brain connectivity, using graph analysis based ... [more ▼]
In this functional magnetic resonance imaging study, we examined the effect of mild propofol sedation and propofol-induced unconsciousness on resting state brain connectivity, using graph analysis based on independent component analysis and a classical seed-based analysis. Contrary to previous propofol research, which mainly emphasized the importance of connectivity in the default mode network (DMN) and external control network (ECN), we focused on the salience network, thalamus, and brainstem. The importance of these brain regions in brain arousal and organization merits a more detailed examination of their connectivity response to propofol. We found that the salience network disintegrated during propofol-induced unconsciousness. The thalamus decreased connectivity with the DMN, ECN, and salience network, while increasing connectivity with sensorimotor and auditory/insular cortices. Brainstem regions disconnected from the DMN with unconsciousness, while the pontine tegmental area increased connectivity with the insulae during mild sedation. These findings illustrate that loss of consciousness is associated with a wide variety of decreases and increases of both cortical and subcortical connectivity. It furthermore stresses the necessity of also examining resting state connectivity in networks representing arousal, not only those associated with awareness. [less ▲]Detailed reference viewed: 80 (12 ULg)
Observance au traitement par CPAP chez les patients souffrant d’apnées du sommeil
Deflandre, Eric ; ; BONHOMME, Vincent et al
Poster (2012, September 20)Detailed reference viewed: 52 (12 ULg)
Intravenous magnesium re-establishes neuromuscular block after spontaneous recovery from an intubating dose of rocuronium: a randomised controlled trial
HANS, Grégory ; BESONGO, Bosenge ; BONHOMME, Vincent et al
in European Journal of Anaesthesiology (2012), 29(2), 95-99Detailed reference viewed: 58 (6 ULg)
Neural correlates of consciousness during general anesthesia using functional magnetic resonance imaging (fMRI).
BONHOMME, Vincent ; ; Brichant, Jean-François et al
in Archives italiennes de biologie (2012), 150(2-3), 155-63
This paper reviews the current knowledge about the mechanisms of anesthesia-induced alteration of consciousness. It is now evident that hypnotic anesthetic agents have specific brain targets whose ... [more ▼]
This paper reviews the current knowledge about the mechanisms of anesthesia-induced alteration of consciousness. It is now evident that hypnotic anesthetic agents have specific brain targets whose function is hierarchically altered in a dose-dependent manner. Higher order networks, thought to be involved in mental content generation, as well as sub-cortical networks involved in thalamic activity regulation seems to be affected first by increasing concentrations of hypnotic agents that enhance inhibitory neurotransmission. Lower order sensory networks are preserved, including thalamo-cortical connectivity into those networks, even at concentrations that suppress responsiveness, but cross-modal sensory interactions are inhibited. Thalamo-cortical connectivity into the consciousness networks decreases with increasing concentrations of those agents, and is transformed into an anti-correlated activity between the thalamus and the cortex for the deepest levels of sedation, when the subject is non responsive. Future will tell us whether these brain function alterations are also observed with hypnotic agents that mainly inhibit excitatory neurotransmission. The link between the observations made using fMRI and the identified biochemical targets of hypnotic anesthetic agents still remains to be identified. [less ▲]Detailed reference viewed: 25 (2 ULg)
Connectivity changes underlying spectral EEG changes during propofol-induced loss of consciousness.
Boly, Mélanie ; ; et al
in The Journal of neuroscience : the official journal of the Society for Neuroscience (2012), 32(20), 7082-90
The mechanisms underlying anesthesia-induced loss of consciousness remain a matter of debate. Recent electrophysiological reports suggest that while initial propofol infusion provokes an increase in fast ... [more ▼]
The mechanisms underlying anesthesia-induced loss of consciousness remain a matter of debate. Recent electrophysiological reports suggest that while initial propofol infusion provokes an increase in fast rhythms (from beta to gamma range), slow activity (from delta to alpha range) rises selectively during loss of consciousness. Dynamic causal modeling was used to investigate the neural mechanisms mediating these changes in spectral power in humans. We analyzed source-reconstructed data from frontal and parietal cortices during normal wakefulness, propofol-induced mild sedation, and loss of consciousness. Bayesian model selection revealed that the best model for explaining spectral changes across the three states involved changes in corticothalamic interactions. Compared with wakefulness, mild sedation was accounted for by an increase in thalamic excitability, which did not further increase during loss of consciousness. In contrast, loss of consciousness per se was accompanied by a decrease in backward corticocortical connectivity from frontal to parietal cortices, while thalamocortical connectivity remained unchanged. These results emphasize the importance of recurrent corticocortical communication in the maintenance of consciousness and suggest a direct effect of propofol on cortical dynamics. [less ▲]Detailed reference viewed: 36 (4 ULg)
Effect of a fluid challenge on the Surgical Pleth Index during stable propofol-remifentanil anaesthesia.
; VERSCHEURE, Sara ; et al
in Acta Anaesthesiologica Scandinavica (2012), 56(6), 787-96
BACKGROUND: The Surgical Pleth Index (SPI), derived from pulse amplitude and heartbeat interval, is proposed to monitor anti-nociception during anaesthesia. Its response to noxious stimulation can be ... [more ▼]
BACKGROUND: The Surgical Pleth Index (SPI), derived from pulse amplitude and heartbeat interval, is proposed to monitor anti-nociception during anaesthesia. Its response to noxious stimulation can be affected by the intravascular volume status. This study investigated the effect of a fluid challenge (FC) on SPI during steady-state conditions. METHODS: After Institutional Review Board approval, 33 consenting patients undergoing neurosurgery received a 4 ml/kg starch FC over less than 5 min under stable surgical stimulation conditions and stable propofol (Ce(PPF) ) and remifentanil (Ce(REMI) ) effect-site concentrations as estimated by target-controlled infusion systems. Intravascular volume status was assessed using the Delta Down (DD). We looked at the SPI response to FC according to DD, Ce(PPF) , and Ce(REMI) . RESULTS: Following FC, SPI did not change in 16, increased in 12, and decreased in 3 patients. Ce(REMI) poorly affected the SPI response to FC. In normovolaemic patients, the probability of an SPI change after FC was low under common Ce(PPF) (0.9 to 3.9 mug/ml). A decrease in SPI was more probable with worsening hypovolaemia and lowering Ce(PPF) , while an increase in SPI was more probable with increasing Ce(PPF) . SPI changes were only attributable to modifications in pulse wave amplitude and not in heart rate. CONCLUSIONS: During stable anaesthesia and surgery, SPI may change in response to FC. The effect of FC on SPI is influenced by volaemia and Ce(PPF) through pulse wave amplitude modifications. These situations may confound the interpretation of SPI as a surrogate measure of the nociception-anti-nociception balance. [less ▲]Detailed reference viewed: 163 (9 ULg)
Nursing aid specialized in anesthesia and resuscitation (NASAR): why should we promote the involvement of anesthesia helping nurses within the current and future Belgian anesthesia field?
; ; BONHOMME, Vincent
in Acta Anaesthesiologica Belgica (2012), 63(1), 1-2Detailed reference viewed: 52 (6 ULg)
Editorial. Nursing Aid Specialized in Anesthesia and Resuscitation (NASAR): why should we promote the involvement of anesthesia helping nurses within the current and future Belgian anesthesia field?
; ; BONHOMME, Vincent
in Acta Anaesthesiologica Belgica (2012), 63(1), 1-2Detailed reference viewed: 40 (0 ULg)
Linking sleep and general anesthesia mechanisms: this is no walkover
BONHOMME, Vincent ; BOVEROUX, Pierre ; Vanhaudenhuyse, Audrey et al
in Acta Anaesthesiologica Belgica (2011), 62(3), 161-171Detailed reference viewed: 157 (18 ULg)
Comparison of the Surgical Pleth Index (TM) with haemodynamic variables to assess nociception-anti-nociception balance during general anaesthesia
Bonhomme, Vincent ; ; Hans, Grégory et al
in British Journal of Anaesthesia (2011), 106(1), 101-11
BACKGROUND: The Surgical Pleth Index (SPI) is proposed as a means to assess the balance between noxious stimulation and the anti-nociceptive effects of anaesthesia. In this study, we compared SPI, mean ... [more ▼]
BACKGROUND: The Surgical Pleth Index (SPI) is proposed as a means to assess the balance between noxious stimulation and the anti-nociceptive effects of anaesthesia. In this study, we compared SPI, mean arterial pressure (MAP), and heart rate (HR) as a means of assessing this balance. METHODS: We studied a standard stimulus [head-holder insertion (HHI)] and varying remifentanil concentrations (CeREMI) in a group of patients undergoing neurosurgery. Patients receiving target-controlled infusions were randomly assigned to one of the three CeREMI (2, 4, or 6 ng m(1)), whereas propofol target was fixed at 3 microg ml(1). Steady state for both targets was achieved before HHI. Intravascular volume status (IVS) was evaluated using respiratory variations in arterial pressure. Prediction probability (Pk) and ordinal regression were used to assess SPI, MAP, and HR performance at indicating CeREMI, and the influence of IVS and chronic treatment for high arterial pressure, as possible confounding factors. RESULTS: The maximum SPI, MAP, or HR observed after HHI correctly indicated CeREMI in one of the two patients [accurate prediction rate (APR)=0.5]. When IVS and chronic treatment for high arterial pressure were taken into account, the APR was 0.6 for each individual variable and 0.8 when all of them predicted the same CeREMI. That increase in APR paralleled an increase in Pk from 0.63 to 0.89. CONCLUSIONS: SPI, HR, and MAP are of comparable value at gauging noxious stimulation-CeREMI balance. Their interpretation is improved by taking account of IVS, treatment for chronic high arterial pressure, and concordance between their predictions. [less ▲]Detailed reference viewed: 133 (13 ULg)
Maintaining the communication and information tool of the Belgian anesthesiology community
in Acta Anaesthesiologica Belgica (2011), 62(4), 173-174Detailed reference viewed: 18 (0 ULg)
Influence of anesthesia on cerebral blood flow, cerebral metabolic rate, and brain functional connectivity.
BONHOMME, Vincent ; BOVEROUX, Pierre ; HANS, Pol et al
in Current Opinion in Anaesthesiology (2011), 24(5), 474-9
PURPOSE OF REVIEW: To describe recent studies exploring brain function under the influence of hypnotic anesthetic agents, and their implications on the understanding of consciousness physiology and ... [more ▼]
PURPOSE OF REVIEW: To describe recent studies exploring brain function under the influence of hypnotic anesthetic agents, and their implications on the understanding of consciousness physiology and anesthesia-induced alteration of consciousness. RECENT FINDINGS: Cerebral cortex is the primary target of the hypnotic effect of anesthetic agents, and higher-order association areas are more sensitive to this effect than lower-order processing regions. Increasing concentration of anesthetic agents progressively attenuates connectivity in the consciousness networks, while connectivity in lower-order sensory and motor networks is preserved. Alteration of thalamic sub-cortical regulation could compromise the cortical integration of information despite preserved thalamic activation by external stimuli. At concentrations producing unresponsiveness, the activity of consciousness networks becomes anticorrelated with thalamic activity, while connectivity in lower-order sensory networks persists, although with cross-modal interaction alterations. SUMMARY: Accumulating evidence suggests that hypnotic anesthetic agents disrupt large-scale cerebral connectivity. This would result in an inability of the brain to generate and integrate information, while external sensory information is still processed at a lower order of complexity. [less ▲]Detailed reference viewed: 69 (14 ULg)
Unexpected entropy response to saline spraying at the end of posterior fossa surgery: a few cases report.
; BONHOMME, Vincent ; et al
in Acta anaesthesiologica Belgica (2011), 62(2), 87-90
The Spectral Entropy proposed to monitor the depth of anesthesia includes the State Entropy (SE) computed from the EEG (0.8-32 Hz frequency band), and the Response Entropy (RE) computed from EEG and ... [more ▼]
The Spectral Entropy proposed to monitor the depth of anesthesia includes the State Entropy (SE) computed from the EEG (0.8-32 Hz frequency band), and the Response Entropy (RE) computed from EEG and facial muscles activity (0.5-47 Hz frequency band). We report an unexpected Entropy response to saline spraying at the end of posterior fossa surgery. Six patients undergoing scheduled functional surgery of the posterior fossa were included in this report. They were anesthetized with propofol and remifentanil using TCI and received an intubation dose of rocuronium. At the end of surgery, saline spraying, performed for hemostatic purpose and wreckage elimination, resulted in a sustained increase in RE and SE without hemodynamic modification in four patients, while no change was observed in the two other ones. In one of the responding patients, 0.1 mg kg(-1) rocuronium attenuated the Entropy response. In the two non responders, repetition of spraying or rocuronium administration did not change Entropy value. Recovery from anesthesia was comparable in all patients and none of them complained from awareness. We conclude that Entropy can increase during posterior fossa surgery in non-paralyzed patients. This response probably reflects an increase in facial muscle activity rather than a change in depth of anesthesia, as far as it can be attenuated by a small dose of rocuronium. While this hypothesis requires further investigation, these observations suggest that saline spraying may confound interpretation of Entropy during posterior fossa surgery. [less ▲]Detailed reference viewed: 208 (4 ULg)
Intravenous lidocaine infusion reduces bispectral index-guided requirements of propofol only during surgical stimulation.
Hans, Grégory ; Lauwick, Séverine ; Kaba, Abdourahmane et al
in British Journal of Anaesthesia (2010), 105(4), 471-9
BACKGROUND: I.V. lidocaine reduces volatile anaesthetics requirements during surgery. We hypothesized that lidocaine would also reduce propofol requirements during i.v. anaesthesia. METHODS: A randomized ... [more ▼]
BACKGROUND: I.V. lidocaine reduces volatile anaesthetics requirements during surgery. We hypothesized that lidocaine would also reduce propofol requirements during i.v. anaesthesia. METHODS: A randomized controlled study of 40 patients tested the effect of i.v. lidocaine (1.5 mg kg(-1) then 2 mg kg(-1) h(-1)) on propofol requirements. Anaesthesia was maintained with remifentanil and propofol target-controlled infusions (TCI) to keep the bispectral index (BIS) around 50. Effect-site concentrations of propofol and remifentanil and BIS values were recorded before and after skin incision. Data were analysed using anova and mixed effects analysis with NONMEM. Two dose-response studies were then performed with and without surgical stimulation. Propofol TCI titrated to obtain a BIS around 50 was kept constant. Then patients were randomized into four groups: A, saline; B, 0.75 mg kg(-1) bolus then infusion 1 mg kg(-1) h(-1); C, 1.5 mg kg(-1) bolus and infusion 2 mg kg(-1) h(-1); and D, 3 mg kg(-1) bolus and infusion 4 mg kg(-1) h(-1). Lidocaine administration coincided with skin incision. BIS values and haemodynamic variables were recorded. Data were analysed using linear regression and two-way anova. RESULTS: Lidocaine decreased propofol requirements (P<0.05) only during surgery. In the absence of surgical stimulation, lidocaine did not affect BIS nor haemodynamic variables, whereas it reduced BIS increase (P=0.036) and haemodynamic response (P=0.006) secondary to surgery. CONCLUSIONS: The sparing effect of lidocaine on anaesthetic requirements seems to be mediated by an anti-nociceptive action. [less ▲]Detailed reference viewed: 147 (5 ULg)
Sevoflurane facial mask induction in children: using two different techniques end to comparable intubation conditions but different Bispectral Index values
Dabee, Loïc ; Hallet, Claude ; Venneman, Ingrid et al
in Acta Anaesthesiologica Belgica (2010, June 19), 61(2), 94Detailed reference viewed: 46 (0 ULg)
High-order brain networks connectivity reflects the level of consciousness during anesthesia
; ; BONHOMME, Vincent et al
Conference (2010)Detailed reference viewed: 21 (4 ULg)
Facial mask induction in children using sevoflurane: two different techniques end to comparable intubation conditions but different Bispectral Index® value
; HALLET, Claude ; VENNEMAN, Ingrid et al
Conference (2010)Detailed reference viewed: 22 (1 ULg)