Epileptiform electroencephalogram during mask induction of anesthesia with sevoflurane

Clinical Sensitivity of Fractal Neurodynamics

Among the significant advances in the understanding of the organization of the neuronal networks that coordinate the body and brain, their complex nature is increasingly important, resulting from the interaction between the very large number of constituents strongly organized hierarchically and at the same time with "self-emerging." This awareness drives us to identify the measures that best quantify the "complexity" that accompanies the continuous evolutionary dynamics of the brain. In this chapter, after an introductory section (Sect. 15.1), we examine how the Higuchi fractal dimension is able to perceive physiological processes (15.2), neurological (15.3) and psychiatric (15.4) disorders, and neuromodulation effects (15.5), giving a mention of other methods of measuring neuronal electrical activity in addition to electroencephalography, such as magnetoencephalography and functional magnetic resonance. Conscious that further progress will support a deeper understanding of the temporal course of neuronal activity because of continuous interaction with the environment, we conclude confident that the fractal dimension has begun to uncover important features of the physiology of brain activity and its alterations.

Electroencephalogram Signatures of Agitation Induced by Sevoflurane and Its Association With Genetic Polymorphisms

Background: Volatile anesthetic-induced agitation, also called paradoxical excitation, is not uncommon during anesthesia induction. Clinically, patients with agitation may lead to self-injury or disrupt the operative position, increasing the incidence of perioperative adverse events. The study was designed to investigate clinical features of sevoflurane-induced agitation and examined whether any gene polymorphisms can potentially be used to predict agitation.

Methods: One hundred seventy-six patients underwent anesthesia induction with sevoflurane were included in this study. Frontal electroencephalogram (EEG), electromyography (EMG), and hemodynamics were recorded continuously during anesthesia induction. DNA samples were genotyped using the Illumina Infinium Asian Screening Array and the SNaPshot technology. Genetic association was analyzed by genome-wide association study. Logistic regression analysis was used to determine the role of variables in the prediction of agitation.

Results: Twenty-five (14.2%) patients experienced agitation. The depth of anesthesia index (Ai index) (p < 0.001), EMG (p < 0.001), heart rate (HR) (p < 0.001), and mean arterial pressure (MAP) (p < 0.001) rapidly increased during the agitation. EEG exhibited a shift toward high frequencies with spikes during agitation. The fast waves (alpha and beta) were more pronounced and the slow rhythms (delta) were less prominent during the occurrence of agitation. Moreover, three SNPs in the methionine synthase reductase (MTRR) gene were correlated to the susceptibility to agitation (p < 5.0 × 10⁻⁶). Carrying rs1801394 A > G (odds ratio 3.50, 95% CI 1.43–9.45) and/or rs2307116 G > A (3.31, 1.36–8.95) predicted a higher risk of agitation.

Discussion: This study suggests that the agitation/paradoxical excitation induced by sevoflurane is characterized as increases in Ai index, EMG, HR and MAP, and the high frequency with spikes in EEG. Moreover, our results provide preliminary evidence for MTRR genetic polymorphisms, involving folate metabolism function, may be related to the susceptibility to agitation.

Clinical Trial Number and Registry URL: ChiCTR1900026218; http://www.chictr.org.cn/showproj.aspx?proj=40655.

Genetic variation of rs12918566 affects GRIN2A expression and is associated with spontaneous movement response during sevoflurane anesthesia induction

N-methyl-D-aspartate (NMDA) receptors mediate excitatory neurotransmission in the nervous system and are preferentially inhibited by general anesthetics such as sevoflurane. Spontaneous movement is a common complication during sevoflurane anesthesia induction and seriously affects operations. In this study, we investigated the relationship between NMDA polymorphisms and spontaneous movement during sevoflurane induction. This prospective clinical study enrolled 393 patients undergoing sevoflurane anesthesia as part of their surgical routine. In the GRIN1, GRIN2A, and GRIN2B genes, 13 polymorphisms that form a heteromeric complex as part of the NMDA receptor were selected using Haploview and genotyped using matrix-assisted laser desorption ionization-time of flight mass spectrometry MassARRAY. Both RNAfold and Genotype-Tissue Expression portals were used to identify gene expression profiles. Our data showed that 35.8% of subjects exhibited spontaneous movement. The GRIN2A rs12918566 polymorphism was associated with spontaneous movement during sevoflurane induction. A logistic regression analysis of additive, dominant, and recessive models indicated a significant association (odds ratio [OR] (95% confidence limit [CI]): 0.58 (0.42-0.80), p = .00086; OR (95% CI): 0.51 (0.31-0.84), p = .0075, and OR (95% CI): 0.47 (0.27-0.81), p = .0060, respectively). After false discovery rate (FDR) correction, the additive model was still significant with a P_FDR =0.010. Bioinformatics demonstrated that the rs12918566 genomic variation affected GRIN2A expression in brain tissue. We also revealed that GRIN2A rs12918566 was significantly associated with spontaneous movement during sevoflurane induction. We believe the NMDA receptor plays an important role in regulating the anesthetic effects of sevoflurane.

High Incidence of Epileptiform Potentials During Continuous EEG Monitoring in Critically Ill COVID-19 Patients

Objective: To analyze continuous 1- or 2-channel electroencephalograms (EEGs) of mechanically ventilated patients with coronavirus disease 2019 (COVID-19) with regard to occurrence of epileptiform potentials. Design: Single-center retrospective analysis. Setting: Intensive care unit of Hannover Medical School, Hannover, Germany. Patients: Critically ill COVID-19 patients who underwent continuous routine EEG monitoring (EEG monitor: Narcotrend-Compact M) during sedation. Measurements and Main Results: Data from 15 COVID-19 patients (11 men, four women; age: 19-75 years) were evaluated. Epileptiform potentials occurred in 10 of 15 patients (66.7%). Conclusions: The results of the evaluation regarding the occurrence of epileptiform potentials show that there is an unusually high percentage of cerebral involvement in patients with severe COVID-19. EEG monitoring can be used in COVID-19 patients to detect epileptiform potentials.

Variations in Values of State, Response Entropy and Haemodynamic Parameters Associated with Development of Different Epileptiform Patterns during Volatile Induction of General Anaesthesia with Two Different Anaesthetic Regimens Using Sevoflurane in Comparison with Intravenous Induct: A Comparative Study

BACKGROUND AND OBJECTIVES

Raw electroencephalographic (EEG) signals are rarely used to monitor the depth of volatile induction of general anaesthesia (VIGA) with sevoflurane, even though EEG-based indices may show aberrant values. We aimed to identify whether response (RE) and state entropy (SE) variations reliably reflect the actual depth of general anaesthesia in the presence of different types of epileptiform patterns (EPs) in EEGs during induction of general anaesthesia.

MATERIALS AND METHODS

A randomized, prospective clinical study was performed with 60 patients receiving VIGA using sevoflurane with the increasing concentrations (group VIMA) or the vital capacity (group VCRII) technique or an intravenous single dose of propofol (group PROP). Facial electromyography (fEMG), fraction of inspired sevoflurane (FiAA), fraction of expired sevoflurane (FeAA), minimal alveolar concentration (MAC) of sevoflurane, RE and SE, and standard electroencephalographic evaluations were performed in these patients.

RESULTS

In contrast to periodic epileptiform discharges, erroneous SE and RE values in the patients' EEGs were associated with the presence of polyspikes (PS) and rhythmic polyspikes (PSR), which were more likely to indicate toxic depth rather than false emergence from anaesthesia with no changes in the FiAA, FeAA, and MAC of sevoflurane.

CONCLUSION

Calculated RE and SE values may be misleading during VIGA when EPs are present in patients' EEGs. During VIGA with sevoflurane, we recommend monitoring raw EEG data in scientific studies to correlate it with potentially erroneous RE and SE values and the end-tidal concentration of sevoflurane in everyday clinical practice, when monitoring raw EEG is not available, because they can mislead anaesthesiologists to reduce sevoflurane levels in the ventilation gas and result in unintentional true emergence from anaesthesia. Further studies are required to investigate the behaviour of EEG-based indices during rapid changes in sevoflurane concentrations at different stages of VIGA and the influence of polyspikes and rhythmic polyspikes on the transformation of EEG signals into a digital form.

Anesthetic Management of a Patient With a Vagal Nerve Stimulator

Vagal nerve stimulation (VNS) is an established adjunctive treatment for patients with refractory epilepsy. VNS is effective in many cases, but few patients achieve complete elimination of seizures. Furthermore, VNS can cause respiratory complications, such as obstructive sleep apnea. This report describes the successful anesthetic management of a 28-year-old woman with a VNS device who underwent dental treatment under general anesthesia. She was morbidly obese and had undergone placement of a VNS device secondary to drug-resistant epilepsy 2 years prior but continued to experience daily epileptic seizures. Because of concerns about the risk of perioperative epileptic seizures and apneic events, use of the dedicated VNS device magnet was planned if such complications occurred. Total intravenous anesthesia was induced with propofol and remifentanil and a bispectral index sensor was used to help monitor brain wave activity for evidence of seizures along with the depth of anesthesia. Postoperatively, the patient received positional therapy and supplemental oxygen while being closely monitored in recovery. The anesthetic course was completed uneventfully without need of the VNS magnet. A thorough understanding of the mechanics of a VNS device, including proper use of the VNS magnet, is critical for an anesthesiologist during the perioperative period.

The effect of ketamine on emergence agitation in children: A systematic review and meta-analysis

BACKGROUND

Ketamine is believed to reduce the incidence of emergence agitation in children undergoing surgery or procedure. However, recent randomized controlled trials reported conflicting findings.

AIMS

To investigate the effect of ketamine on emergence agitation in children.

METHODS

Databases of MEDLINE, EMBASE, and CENTRAL were systematically searched from their start date until February 2019. Randomized controlled trials comparing intravenous ketamine and placebo in children were sought. The primary outcome was the incidence of emergence agitation. Secondary outcomes included postoperative pain score, duration of discharge time, and the adverse effects associated with the use of ketamine, namely postoperative nausea and vomiting, desaturation, and laryngospasm.

RESULTS

Thirteen studies (1125 patients) were included in the quantitative meta-analysis. The incidence of emergence agitation was 14.7% in the ketamine group and 33.3% in the placebo group. Children receiving ketamine had a lower incidence of emergence agitation, with an odds ratio being 0.23 (95% confidence interval: 0.11 to 0.46), certainty of evidence: low. In comparison with the placebo, ketamine group achieved a lower postoperative pain score (odds ratio: -2.42, 95% confidence interval: -4.23 to -0.62, certainty of evidence: very low) and lower pediatric anesthesia emergence delirium scale at 5 minutes after operation (odds ratio: -3.99, 95% confidence interval: -5.03 to -2.95; certainty of evidence: moderate). However, no evidence was observed in terms of incidence of postoperative nausea and vomiting, desaturation, and laryngospasm.

CONCLUSION

In this meta-analysis of 13 randomized controlled trials, high degree of heterogeneity and low certainty of evidence limit the recommendations of ketamine for the prevention of emergence agitation in children undergoing surgery or imaging procedures. However, the use of ketamine is well-tolerated without any notable adverse effects across all the included trials.

PROSPERO REGISTRATION

CRD42019131865.

Sevoflurane increases locomotion activity in mice

Clinical observations show emergence of agitation and hyperactivity during the anesthesia induction and/or recovery period post-anesthesia. However, an animal model to illustrate this clinical phenomenon has not yet been established. We therefore set out to investigate whether sevoflurane, a commonly used anesthetic, could alter locomotion in mice during the anesthesia induction and recovery period post-anesthesia. The activity of the mice was recorded 5 minutes before, during (for 30 minutes), and 40 minutes after the administration of the anesthetic sevoflurane [1-, 1.5- and 2-fold minimum alveolar concentration] at 37⁰ C. The total walking distance and velocity of movement were measured and quantified as the indexes of locomotion. We found that the anesthetic sevoflurane increased the locomotion of the mice during the induction period of the anesthesia. During the recovery phase after anesthesia, the mice exhibited increased locomotion for a short period of time (about 5 minutes) and then displayed a sharp decrease in mobility for up to 60 minutes following the end of anesthesia administration. The anesthetic sevoflurane did not significantly alter the food intake and body weight of the mice. Furthermore, we found that Alzheimer’s disease transgenic mice exhibited a greater degree of sevoflurane-induced hyperactivity than the wild-type mice did. Our results showed that inhalation of the anesthetic sevoflurane induced an acute hyperactivity in mice, particularly among Alzheimer’s disease transgenic mice. These findings from the pilot studies have established an animal model to promote further studies into postoperative emergence agitation, hyperactivity and the underlying mechanisms into these conditions.

A Framework Proposal to Follow-Up on Preclinical Convulsive Signals of a New Molecular Entity in First-in-Human Studies Using Electroencephalographic Monitoring

Traditionally, in dose-escalating first-in-human (FiH) studies, a dose cap with a 10-fold safety margin to the no observed effect level in animals is implemented if convulsive events are observed in animals. However, the convulsive risk seen in animals does not generally translate to humans. Several lines of evidence are summarized indicating that in a dose-escalating setting, electroencephalographic epileptiform abnormalities occur at lower doses than clinical convulsive events. Therefore, we propose to consider the occurrence of epileptiform abnormalities in toxicology studies as premonitory signals for convulsions in dose-escalating FiH studies. Compared with the traditional dose-cap approach, this may allow the exploration of higher doses in FiH and, subsequently, phase II studies without compromising human safety. Similarly, the presence or absence of electroencephalographic epileptiform abnormalities may also aid the assessment of proconvulsive risk in situations of increased perpetrator burden as potentially present in pharmacokinetic and/or pharmacodynamic drug-drug interactions.

EEG profiles during general anesthesia in children: A comparative study between sevoflurane and propofol

BACKGROUND

In this prospective study, we describe the electroencephalographic (EEG) profiles in children anesthetized with sevoflurane or propofol.

METHODS

Seventy-three subjects (11 years, range 5-18) were included and randomly assigned to two groups according to the anesthetic agent. Anesthesia was performed by target-controlled infusion of propofol (group P) or by sevoflurane inhalation (group S). Steady-state periods were performed at a fixed randomized concentration between 2, 3, 4, 5, and 6 μg.ml^-1 of propofol in group P and between 1, 2, 3, 4, and 5% of sevoflurane in group S. Remifentanil was continuously administered throughout the study. Clinical data, Bispectral Index (BIS), and raw EEG were continuously recorded. The relationship between BIS and anesthetic concentrations was studied using nonlinear regression. For all steady-state periods, EEG traces were reviewed to assess the presence of epileptoid signs, and spectral analysis of raw EEG was performed.

RESULTS

Under propofol, BIS decreased monotonically and EEG slowed down as concentrations increased from 2 to 6 μg.ml^-1 . Under sevoflurane, BIS decreased from 0% to 4% and paradoxically rose from 4% to 5% of expired concentration: this increase in BIS was associated with the occurrence of fast oscillations and epileptoid signs on the EEG trace. Propofol was associated with more delta waves and burst suppression periods compared to sevoflurane.

CONCLUSION

Under deep anesthesia, the BIS and electroencephalographic profiles differ between propofol and sevoflurane. For high concentrations of sevoflurane, an elevated BIS value may be interpreted as a sign of epileptoid patterns or EEG fast oscillations rather than an insufficient depth of hypnosis.

Sevoflurane versus Propofol for Induction of Anaesthesia for Electroconvulsive Therapy: A Randomized Crossover Trial

Propofol is often used to induce anaesthesia for electroconvulsive therapy. Some patients who receive propofol have fits of poor quality or inadequate duration despite increasing electroconvulsive therapy doses. Sevoflurane has been reported to exhibit pro-convulsant properties in some “at-risk” patients during anaesthesia for other procedures. The purpose of this study was to perform a randomized crossover trial in patients undergoing electroconvulsive therapy, comparing the effects on seizure parameters of propofol versus sevoflurane induction. Patients were randomly allocated to receive either sevoflurane or propofol for their first treatment. In the subsequent treatment the alternative agent was used.

Patients in both treatment groups exhibited equally good fits, with those in the sevoflurane group having slightly better morphology, which is the most subjective of the parameters measured. The sevoflurane administrations were associated with slightly higher pulse rates and blood pressures.

Sevoflurane provides a suitable alternative to propofol for anaesthesia in patients undergoing electroconvulsive therapy, although the slightly greater pulse rate rise and blood pressure rise should be considered in patients with ischaemic heart disease.

A study into perioperative anaesthetic adverse events in Thailand (PAAd THAI): An analysis of suspected emergence delirium

The purpose of this study is to demonstrate the characteristics, contributing factors and recommended policy changes associated with emergence delirium. Relevant data were extracted from the PAAd Thai database of 2,006 incident reports which were conducted from 1 January to 31 December 2015. Details pertinent to the patient, surgery, anaesthetic and systematic factors were reviewed independently. Seventeen incidents of emergence delirium were recorded. Emergence delirium was common in the following categories: male (70.6%), over 65 years of age (53%), elective surgery (76%) and orthopedic surgery (35%). Physical restraint was required in 53% (9 of 17) of cases and 14 patients (82%) required medical treatment. One patient developed postoperative delirium and required medical treatment. The study led to the following recommendations: Development of a classification of practice guidelines and a screening tool, and training for restraint use.

Sevoflurane activates hippocampal CA3 kainate receptors (Gluk2) to induce hyperactivity during induction and recovery in a mouse model

BACKGROUND

In addition to general anaesthetic effects, sevoflurane can also induce hyperactive behaviours during induction and recovery, which may contribute to neurotoxicity; however, the mechanism of such effects is unclear. Volatile anaesthetics including isoflurane have been found to activate the kainate (GluK2) receptor. We developed a novel mouse model and further explored the involvement of kainate (GluK2) receptors in sevoflurane-induced hyperactivity.

METHODS

Maximal speed, mean speed, total movement distance and resting percentage of C57BL/6 mice were quantitatively measured using behavioural tracking software before and after sevoflurane anaesthesia. Age dependence of this model was also analysed and sevoflurane-induced hyperactivity was evaluated after intracerebral injection of the GluK2 receptor blocker NS-102. Neurones from the hippocampal CA3 region were used to undertake in vitro electrophysiological measurement of kainate currents and miniature excitatory postsynaptic potential (mEPSP).

RESULTS

Sevoflurane induced significant hyperactivities in mice under sevoflurane 1% anaesthesia and during the recovery period, characterized as increased movement speed and total distance. The hyperactivity was significantly increased in young mice compared with adults (P<0.01) and pre-injection of NS-102 significantly prevented this sevoflurane-induced hyperactivity. In electrophysiological experiments, sevoflurane significantly increased the frequency of mEPSP at low concentrations and evoked kainate currents at high concentrations.

CONCLUSIONS

We developed a behavioural model in mice that enabled characterization of sevoflurane-induced hyperactivity. The kainate (GluK2) receptor antagonist attenuated these sevoflurane-induced hyperactivities in vivo, suggesting that kainate receptors might be the underlying therapeutic targets for sevoflurane-induced hyperactivities in general anaesthesia.

A clinical review of inhalation anesthesia with sevoflurane: from early research to emerging topics

A large number of studies during the past two decades have demonstrated the efficacy and safety of sevoflurane across patient populations. Clinical researchers have also investigated the effects of sevoflurane, its hemodynamic characteristics, its potential protective effects on several organ systems, and the incidence of delirium and cognitive deficiency. This review examines the clinical profiles of sevoflurane and other anesthetic agents, and focuses upon emerging topics such as organ protection, postoperative cognitive deficiency and delirium, and novel ways to improve postanesthesia outcomes.

Use of BIS VISTA bilateral monitor for diagnosis of intraoperative seizures, a case report

Changes in BIS (bispectral index) VISTA bilateral monitoring system associated with intraoperative episodes of generalized and focal seizures, during total intravenous anesthesia for resection of a left frontal parasagittal meningioma, are herein described.

Epileptiform activity during induction of anesthesia with sevoflurane prior to elective carotid endarterectomy

The optimal anesthetic technique for carotid endarterectomy is still controversial. For general anesthesia, various induction agents have been used. We present two patients with asymptomatic high-grade carotid stenosis where induction with sevoflurane resulted in epileptiform discharges seen on perioperative electroencephalogram monitoring without adverse clinical sequelae. The occurrence of epileptogenic electroencephalogram during sevoflurane anesthesia has been widely described despite its popular use in pediatric anesthesia. This phenomenon, however, has not been previously described during electroencephalogram monitoring in carotid surgery. The authors suggest that induction anesthesia with sevoflurane should be avoided in this patient population especially where routine electroencephalogram monitoring is not performed.

Preoperative anxiety management, emergence delirium, and postoperative behavior

Preoperative anxiolysis is important for children scheduled for surgery. The nature of the anxiety depends on several factors, including age, temperament, past hospitalizations, and socioeconomic and ethnic backgrounds. A panoply of interventions effect anxiolysis, including parental presence, distraction, and premedication, although no single strategy is effective for all ages. Emergence delirium (ED) occurs after the use of sevoflurane and desflurane in preschool-aged children in the recovery room. Symptoms usually last approximately 15 minutes and resolve spontaneously. The Pediatric Anesthesia Emergence Delirium scale is used to diagnose ED and evaluate therapeutic interventions for ED such as propofol and opioids.

Development of an implantable flexible probe for simultaneous near-infrared spectroscopy and electrocorticography

A combination of near-infrared spectroscopy (NIRS) and electrocorticography (ECoG) provides beneficial information on cortical activity from different aspects. Integration of such multimodal measurement capability into a single apparatus and the direct measurement of cortical activity during chronic subdural implantation may be a powerful means for clinical diagnosis and neuroscience. However, an optical fiber-based NIRS probe cannot be miniaturized for implantation into the brain, and the light-scattering effect of ECoG electrodes in NIRS measurements is unknown. We describe here the development of a flexible probe, small enough for chronic subdural implantation, for simultaneous NIRS and ECoG. Two light-emitting diodes of different wavelengths and two photodiodes were mounted on a polyimide-based flexible substrate, and ECoG electrodes were formed with a design minimizing artifacts in NIRS recording. The fabricated probe measured ECoGs at sufficient spatial resolution and submicromolar changes in hemoglobin concentrations in in vivo experiments with acute implantation into a rat. Comparison of measured changes in hemoglobin concentrations for different source-detector distances reveals the reliability of the measured values and the practicality of the simulation model. The proposed intracranial multimodality probe may provide beneficial evidence for pre- and intrasurgical assessment of neurosurgery and reveal the interaction of electrophysiology and hemodynamics at high spatial resolution without artifacts due to scalp blood flow.

Influence of the sevoflurane concentration on the occurrence of epileptiform EEG patterns

Objectives and Aim

This study was performed to analyse the effects of different sevoflurane concentrations on the incidence of epileptiform EEG activity during induction of anaesthesia in children in the clinical routine.

Background

It was suggested in the literature to use sevoflurane concentrations lower than 8% to avoid epileptiform activity during induction of anaesthesia in children.

Methods

100 children (age: 4.6±3.0 years, ASA I–III, premedication with midazolam) were anaesthetized with 8% sevoflurane for 3 min or 6% sevoflurane for 5 min in 100% O₂ via face mask followed by 4% sevoflurane until propofol and remifentanil were given for intubation. EEGs were recorded continuously and were analysed visually with regard to epileptiform EEG patterns.

Results

From start of sevoflurane until propofol/remifentanil administration, 38 patients (76%) with 8% sevoflurane had epileptiform EEG patterns compared to 26 patients (52%) with 6% (p = 0.0106). Epileptiform potentials tended to appear later in the course of the induction with 6% than with 8%. Up to an endtidal concentration of 6% sevoflurane, the number of children with epileptiform potentials was similar in both groups (p = 0.3708). The cumulative number of children with epileptiform activity increased with increasing endtidal sevoflurane concentrations. The time from start of sevoflurane until loss of consciousness was similar in patients with 8% and 6% sevoflurane (42.2±17.5 s vs. 44.9 s ±14.0 s; p = 0.4073). An EEG stage of deep anaesthesia with continuous delta waves <2.0 Hz appeared significantly earlier in the 8% than in the 6% group (64.0±22.2 s vs. 77.9±20.0 s, p = 0.0022).

Conclusion

The own analysis and data from the literature show that lower endtidal concentrations of sevoflurane and shorter administration times can be used to reduce epileptiform activity during induction of sevoflurane anaesthesia in children.

Epileptogenic drugs: a systematic review

A wide range of substances, including drugs and illicit compounds, increase the risk of epileptic seizures. In this systematic review, the authors address the issue of the epileptogenic potential of marketed drugs, with the aims of providing criteria for the assessment of the cause-effect relationship between drug exposure and the risk of seizures; and to identify the compounds better fulfilling the requirements of an epileptogenic drug. Finding a correlation between drug exposure and occurrence of seizures does not necessarily establish a causal association. In light of the available evidence, even with these limitations, some conclusive remarks can be made on the epileptogenic potential of some active principles. Drugs with high epileptogenic potential include meperidine, sevoflurane, clozapine, phenothiazines and cyclosporine. Drugs with intermediate epileptogenic potential include propofol, maprotiline, tricyclic antidepressants and chlorambucil. Drugs with low epileptogenic potential include fluorquinolones, carbapenems, bupropion and iodinated contrast media. Drugs with minimal or inconclusive epileptogenic potential include interferon alpha.

[Antiepileptic prophylaxis for elective neurosurgery]

In tumoral surgery, the risk factors for perioperative epilepsy can be roughly grouped into two categories: those related to the preoperative patient's conditions (type and location of the tumors, their impact on the surrounding brain…) and those specifically related to surgery (cerebral edema, parenchymal hematoma, surgical approach, complete or incomplete resection...). The first category is supposed to be responsible for preoperative and late postoperative epilepsy, while the second would be more related to the risk of epilepsy in the first postoperative week (or may be even in the first 48hours). It is well accepted (but not always respected) by the neuro-oncologists that there is no indication for preventive antiepileptic drugs (AED) in a patient with a brain tumor that has never presented seizure. However, every seizure crisis must be treated medically. Neurosurgical procedure (which is also a key factor for controlling epilepsy when it occurs. The AED should then be maintained as appropriate. In the absence of preoperative treatment, it has never been shown that prophylactic AED significantly decreases the incidence of postoperative seizures, early or late. Yet, the opposite has not been shown neither, and many groups use AED despite the risk of side effects and an uncertain risk-benefit ratio. Currently, postoperative epilepsy is much less frequent than it was 20 or 30years ago, and the risk of AED side effects also decreases with the latest generation of molecules (such as levetiracetam). So, AED risks and benefits tend to diminish in parallel, but their relationship is still to be assessed. In practice, a modern attitude would restrict prophylactic AED use to the higher risk patients (preoperative epilepsy, temporal astrocytoma, the extent of edema and mass effect...). A drug of last generation should be used, starting one week before surgery. The duration of the treatment should be limited to one week postoperatively in the absence of seizure.

Incidence of epileptiform EEG activity in children during mask induction of anaesthesia with brief administration of 8% sevoflurane

Background

A high incidence of epileptiform activity in the electroencephalogram (EEG) was reported in children undergoing mask induction of anaesthesia with administration of high doses of sevoflurane for 5 minutes and longer. This study was performed to investigate whether reducing the time of exposure to a high inhaled sevoflurane concentration would affect the incidence of epileptiform EEG activity. It was hypothesized that no epileptiform activity would occur, when the inhaled sevoflurane concentration would be reduced from 8% to 4% immediately after the loss of consciousness.

Methodology/Principal Findings

70 children (age 7–96 months, ASA I–II, premedication with midazolam) were anaesthetized with 8% sevoflurane in 100% oxygen via face mask. Immediately after loss of consciousness, the sevoflurane concentration was reduced to 4%. EEGs were recorded continuously and were later analyzed visually with regard to epileptiform EEG patterns. Sevoflurane at a concentration of 8% was given for 1.2±0.4 min (mean ± SD). In 14 children (20%) epileptiform EEG patterns without motor manifestations were observed (delta with spikes (DSP), rhythmic polyspikes (PSR), epileptiform discharges (PED) in 10, 10, 4 children (14%, 14%, 6%)). 38 children (54%) had slow, rhythmic delta waves with high amplitudes (DS) appearing on average before DSP.

Conclusions/Significance

The hypothesis that no epileptiform potentials would occur during induction of anaesthesia with a reduction of the inspired sevoflurane concentration from 8% to 4% directly after LOC was not proved. Even if 8% sevoflurane is administered only briefly for induction of anaesthesia, epileptiform EEG activity may be observed in children despite premedication with midazolam.

The EEG signal: a window on the cortical brain activity

The accurate assessment of the depth of anesthesia, allowing a more accurate adaptation of the doses of hypnotics, is an important end point for the anesthesiologist. It is a particularly crucial issue in pediatric anesthesia, in the context of the recent controversies about the potential neurological consequences of the main anesthetic drugs on the developing brain. The electroencephalogram signal reflects the electrical activity of the neurons in the cerebral cortex. It is thus the key to assessment of the level of hypnosis. Beyond visual analysis, several monitoring devices allow an automated treatment of the electroencephalographic (EEG) signal, combining time and frequency domain analysis. Each of these monitors focuses on a specific combination of characteristics of the signal and provides the clinician with useful information that remains, however, partial. For a comprehensive approach of the EEG-derived indices, the main features of the normal EEG, in adults and children, will be presented in the awake state and during sleep. Age-related modifications accompanying cerebral maturation during infancy and childhood will be detailed. Then, this review will provide an update on how anesthetic drugs, particularly hypnotics, influence the EEG signal, and how the main available monitors analyze these drug-induced modifications. The relationships between pain, memory, and the EEG will be discussed. Finally, this review will focus on some specific EEG features such as the electrical epileptoid activity observed under sevoflurane anesthesia. The EEG signal is the best window we have on cortical brain activity and provides a fair pharmacodynamic feedback of the effects of hypnotics. However, the cortex is only one of several targets of anesthesia. Hypnotics and opiates, have also subcortical primary targets, and the EEG performances in the evaluation or prediction of nociception are poor. Monitoring subcortical structures in combination with the EEG might in the future allow a better evaluation and a more precise adaptation of balanced anesthesia.

Automatic detection and analysis of the EEG sharp wave-slow wave patterns evoked by fluorinated inhalation anesthetics

OBJECTIVE

The aim of this study was to develop a method for the automatic detection of sharp wave-slow wave (SWSW) patterns evoked in EEG by volatile anesthetics and to identify the patterns' characteristics.

METHODS

The proposed method consisted in the k-NN classification with a reference set obtained using expert knowledge, the morphology of the EEG patterns and the condition for their synchronization. The decision rules were constructed and evaluated using 24h EEG records in ten patients.

RESULTS

The sensitivity, specificity and selectivity of the method were 0.88 ± 0.10, 0.81 ± 0.13 and 0.42 ± 0.16, respectively. SWSW patterns' recruitment was strictly dependent on anesthetic concentration. SWSW patterns evoked by different types of anesthetics expressed different characteristics.

CONCLUSIONS

Synchronization criterion and adequately selected morphological features of "slow wave" were sufficient to achieve the high sensitivity and specificity of the method.

SIGNIFICANCE

The monitoring of SWSW patterns is important in view of possible side effects of volatile anesthetics. The analysis of SWSW patterns' recruitment and morphology could be helpful in the diagnosis of the anesthesia effects on the CNS.

Sevoflurane-emergence agitation: Effect of supplementary low-dose oral ketamine premedication in preschool children undergoing dental surgery

BACKGROUND AND OBJECTIVES

The use of sevoflurane in pediatric anesthesia, which could enable a more rapid emergence and recovery, is complicated by the frequent occurrence of post-anesthesia agitation. This study aims to test the efficacy of adding a low dose of ketamine orally, as a supplement to the midazolam-based oral premedication for reducing sevoflurane-related emergence agitation.

MATERIALS AND METHODS

Ninety-two preschool children, aged between two and six years, with an American Society of Anesthesiologists physical status I or II, scheduled for elective dental filling and extractions under general anesthesia were included. The patients were allocated into two groups: Group M (46 patients) received oral midazolam 0.5 mg/kg, mixed with ibuprofen 10 mg/kg, while group KM (46 patients) received a similar premedication mixture, in addition to ketamine 2 mg/kg. The acceptance of the drug mixture, the onset of action, and the occurrence of vomiting were monitored over the next 30 minutes. Induction of anesthesia was carried out using sevoflurane 8 Vol% in 100% oxygen via face mask. Anesthesia was maintained with sevoflurane 1.5-2 Vol% in an oxygen-nitrous oxide mixture. After extubation, the standard scoring scale was used for assessing the quality of emergence. Agitation parameters were measured using a five-point scale. Agitated children were managed by giving intravenous increments of fentanyl 1 mug/ kg. The time of hospital discharge allowance was recorded.

RESULTS

Drug palatability, vomiting, and onset of action of premedication; showed no significant differences between both groups. Time of eye opening after discontinuation of sevoflurane showed no significant differences between both groups. Postoperative agitation score and rescue fentanyl consumption were higher in group M than in group KM on admission to the PACU (P < 0.01). The time of hospital discharge allowance in group M was longer than in group KM (P < 0.05).

CONCLUSION

Adding a low dose of oral ketamine to midazolam-based oral premedication in preschool children undergoing dental surgery reduced sevoflurane-related emergence agitation without delaying discharge.

Recent advances in pediatric anesthesia

Writing about advances in a field of medicine normally includes some pride about progress which one was witness to or even a participant in. The younger one is, the more enthusiastically every advance is lauded and welcomed. This is human nature and nothing to be complained about. However, when anesthesiologists, having worked and struggled in the field of pediatric anesthesia for about 40 years, look back to past advances, a more realistic, even painful picture comes to mind. There was a price which a considerable number of patients had to pay for progress, ruined health or even death. This experience of decades of practice is rarely presented in the literature but should not be forgotten when we proudly remember advances in pediatric anesthesia.

[Perioperative considerations in vagal nerve stimulator implantation]

Vagal nerve stimulation has become an a important tool in the treatment of refractory epilepsy, which continues to be the main indication for this technique. Other therapeutic indications are emerging, however, and vagal nerve stimulation has now been approved for major depression. Additional possible uses under study include morbid obesity, Alzheimer disease, chronic pain syndromes, and certain neuropsychologic disorders. This review considers perioperative aspects relevant to using this therapeutic procedure with a view to facilitating better and more integrated management of its application.

The electrocortical effects of enflurane: experiment and theory

BACKGROUND

High concentrations of enflurane will induce a characteristic electroencephalogram pattern consisting of periods of suppression alternating with large short paroxysmal epileptiform discharges (PEDs). In this study, we compared a theoretical computer model of this activity with real local field potential (LFP) data obtained from anesthetized rats.

METHODS

After implantation of a high-density 8 x 8 electrode array in the visual cortex, the patterns of LFP and multiunit spike activity were recorded in rats during 0.5, 1.0, 1.5, and 2.0 minimum alveolar anesthetic concentration (MAC) enflurane anesthesia. These recordings were compared with computer simulations from a mean field model of neocortical dynamics. The neuronal effect of increasing enflurane concentration was simulated by prolonging the decay time constant of the inhibitory postsynaptic potential (IPSP). The amplitude of the excitatory postsynaptic potential (EPSP) was modulated, inverse to the neocortical firing rate.

RESULTS

In the anesthetized rats, increasing enflurane concentrations consistently caused the appearance of suppression pattern (>1.5 MAC) in the LFP recordings. The mean rate of multiunit spike activity decreased from 2.54/s (0.5 MAC) to 0.19/s (2.0 MAC). At high MAC, the majority of the multiunit action potential events became synchronous with the PED. In the theoretical model, prolongation of the IPSP decay time and activity-dependent EPSP modulation resulted in output that was similar in morphology to that obtained from the experimental data. The propensity for rhythmic seizure-like activity in the model could be determined by analysis of the eigenvalues of the equations.

CONCLUSION

It is possible to use a mean field theory of neocortical dynamics to replicate the PED pattern observed in LFPs in rats under enflurane anesthesia. This pattern requires a combination of a moderately increased total area under the IPSP, prolonged IPSP decay time, and also activity-dependent modulation of EPSP amplitude.

[Anesthesia for procedures other than neurosurgery in the adult with epilepsy]

Epilepsy is a common disease affecting between 1% and 2% of the general population. The incidence increases with age. Given the complicated etiology and pathogenesis of this disease, epileptic patients of all ages may require anesthesia. The perioperative care of these patients involves a number of special considerations, although the main issues to deal with are pharmacologic. This review gives an overview of the etiopathogenesis and pathophysiology of epilepsy and describes the general characteristics of antiepileptic drug therapy. The anesthetic implications of chronic treatment with antiepileptic agents and the interactions between these drugs and common anesthetics are discussed in more detail.

Topographic electroencephalogram in children during mask induction of anaesthesia with sevoflurane

BACKGROUND

Epileptiform patterns, spikes, polyspikes and periodic epileptiform discharges (PED) have been reported in electroencephalograms (EEGs) during anaesthesia induction with sevoflurane in healthy adults and children. Published recordings have been performed with a limited number of channels, and therefore the topographic distributions of these patterns are not known.

METHODS

Twenty ASA I children aged 4-10 years undergoing routine operations were anaesthetized with 8% sevoflurane in 50%/50% oxygen and nitrous oxide using mask induction with controlled normoventilation. An EEG was recorded with a full 10-20 electrode system including orbitofrontal and ear electrodes, and a recording band of 0.016-70 Hz. Beat-to-beat heart rate (HR) was calculated off-line.

RESULTS

Nineteen out of 20 children developed multifocal spikes and polyspikes with a maximum over the frontal lobes. Four patients developed suppression, which was almost continuous and lasted several minutes, and thereafter a continuous EEG resumed, a few spikes were seen and then a nonepileptiform pattern. In three children a couple of PED waves were seen at the onset of a continuous EEG. HR increased maximally before the onset of spikes. No motor phenomena were seen.

CONCLUSION

These recordings confirm the epileptogenic property of sevoflurane in mask induction. The spikes and polyspikes had frontal multifocal maxima and may be missed in recordings from frontopolar electrodes used by depth-of-anaesthesia monitors. PED and burst suppression were synchronous over the whole cortex. Epileptiform activity was indiscernible from epileptiform waveforms without anaesthesia, such as the patterns seen in status epilepticus.

Effects of pain stimulation on bispectral index, heart rate and blood pressure at different minimal alveolar concentration values of sevoflurane

BACKGROUND

The aim of the present study was to examine the level of unconsciousness measured with bispectral index (BIS) at different minimal alveolar concentration (MAC) levels of sevoflurane, and to study the hemodynamic and BIS reactions during noxious stimulation with transcutaneous electrical nerve stimulation (TENS) and an ice water pain test (IWP).

METHODS

This study was approved by the Ethics Committee and was performed on 10 healthy, young volunteers (six males and four females), ASA physical status I. Anesthesia was induced and maintained with sevoflurane in an oxygen/air mixture. The volunteers were spontaneously breathing, but if necessary, ventilation was mechanically supported. TENS and IWP were performed at 1.0, 1.5 and 2.0 MAC of sevoflurane.

RESULTS

At 1.0 MAC, there was a significant increase in BIS during pain stimulation both with IWP (P<0.03) and with TENS (P<0.005), but at 1.5 MAC there were no changes. A marked variation in BIS was seen at 2.0 MAC, with periods of burst suppression and periods of high BIS values despite clinical signs of deep anesthesia. These marked variations in BIS were seen before, during and after pain stimulation. One volunteer (# 8) had a short episode of convulsions at 2.0 MAC.

CONCLUSION

BIS, heart rate and blood pressure increased during pain stimulation at 1.0 MAC but not at 1.5 MAC of sevoflurane. There was a remarkable variation in BIS at 2.0 MAC of sevoflurane, with BIS values indicating wakefulness despite clinical signs of deep anesthesia. This BIS variation is probably caused by epileptogenic activity due to sevoflurane.

Recurrence of focal seizure activity in an infant during induction of anaesthesia with sevoflurane

A three-month-old male infant, previously diagnosed with seizures with a focal origin induced by hypocalcaemia secondary to hypoparathyroidism, presented for right cataract surgery. The hypocalcaemia and seizure activity had resolved with medical therapy, with normal calcium levels and no seizures for a month. Anaesthesia with halothane and isoflurane for left cataract surgery two days previously had been uneventful. During induction of anaesthesia with sevoflurane for the right cataract surgery, the patient had a focal seizure similar to those previously occurring when the patient was hypocalcaemic. The patient had normal calcium levels at the time of surgery. It appears likely that sevoflurane had triggered seizure activity in the apparently controlled focus. The potential for sevoflurane to induce epileptogenic activity in patients with reduced seizure threshold is discussed.

Repetitive generalized seizure-like activity during emergence from sevoflurane anesthesia

PURPOSE

Sevoflurane-induced seizures are most often described during mask induction of anesthesia when high concentrations of the volatile agent are administered concomitant with alveolar hyperventilation. The occurrence of seizure-like activity during emergence from sevoflurane anesthesia has been rarely reported.

CLINICAL FEATURES

We describe a patient who developed several episodes of generalized tonic-clonic seizure-like activity during and immediately after emergence from sevoflurane anesthesia and discuss the potential factors that contributed to this unusual complication. The patient was treated with intravenous propofol, midazolam, and phenytoin and required intensive care management before his neurologic status stabilized.

CONCLUSION

The report emphasizes that sevoflurane is capable of producing excitatory central nervous system (CNS) phenomena in spite of causing primarily CNS depressant effects.