Summary
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.
Summary
Sevoflurane has become the volatile agent of choice for inhalation induction of anesthesia. Hemodynamic stability and lack of respiratory irritation have justified its rapid extension to ...pediatric inhalation induction. The epileptogenic potential of sevoflurane has been suspected since the first case reports of abnormal movements in children without a history of epilepsy. The objectives of this short review are to: (i) analyze clinical and electroencephalographic (EEG) features supporting epileptogenic activity of sevoflurane, (ii) identify factors which may modulate that activity, and (iii) suggest guidelines of clinical practice to limit expression of this epileptiform phenomenon, which has thus far unknown morbidity. The use of sevoflurane may be associated with cortical epileptiform EEG signs, usually without clinical manifestation. No lasting neurological or EEG sequelae have been described thus far, and the potential morbidity of this epileptogenic effect is unknown. The use of sevoflurane in children, with its remarkable cardiovascular profile, should include a number of precautions. Among them, the limitation of the depth of anesthesia is essential. The wide use of cerebral function monitoring (the most simple being the EEG), may permit optimization of sevoflurane dose and avoidance of burst suppression and major epileptiform signs in fragile subjects, notably the very young and the very old.
The aim of this study was to identify the best model to describe pharmacokinetics and pharmacodynamics in prepubertal children and therefore to calculate the corresponding pharmacodynamic parameters. ...In addition, and to confirm our method, a group of postpubertal subjects was also studied.
Sixteen children (9.5 yr, range 6-12) and 13 adults (22 yr, range 13-35) were included. Induction was performed by plasma target-controlled infusion of propofol (6 microg/ml) based on the Kataria model in children and on the Schnider model in adults. The relationship of bispectral index to predicted concentrations was studied during induction using the Kataria, pediatric Marsh, Schüttler, and Schnider models in children. Because the best performance was obtained, strangely enough, with the Schnider model, the two groups were pooled to investigate influence of puberty on pharmacodynamic parameters (kE0 plasma effect-site equilibration rate constant and Ce50 effect-site concentration corresponding with 50% of the maximal effect). The time-to-peak effect was calculated, and the kE0 was determined for the Kataria model (nonlinear mixed-effects modeling; pkpdtools).
In children, the predicted concentration/effect relationship was best described using the Schnider model. When the whole population was considered, a significant improvement in this model was obtained using puberty as a covariate for kE0 and Ce50. The time to peak effect, Tpeak (median, 0.71 range, 0.37-1.64 and 1.73 1.4-2.68 min), and the Ce50 (3.71 1.88-4.4 and 3.07 2.95-5.21 microg/ml) were shorter and higher, respectively, in children than in adults. The kE0 linked to the Kataria model was 4.6 1.4-11 min.
In children, the predicted concentration/effect relationships were best described using the Schnider model described for adults compared with classic pediatric models. The study suggests that the Schnider model might be useful for propofol target-control infusion in children.
In this prospective study, we compared the relationship between propofol concentrations and bispectral index (BIS) in children versus young adults anesthetized with target-controlled infusion (TCI) ...of propofol.
Forty-five prepubertal subjects (children) and 45 postpubertal subjects (adults) were studied. All patients were anesthetized with TCI of propofol, based on the Kataria et al.'s model for children and on the Schnider et al.'s model for adults. All data from the BIS and the TCI system were continuously recorded using Rugloop software. Remifentanil was continuously administered throughout the study (0.25 microg x kg(-1) x min(-1)). In all patients, after the end of surgery, a 12-min period with a stable target plasma concentration (Ct) of propofol, randomly assigned at 2, 3, 4, 5, and 6 microg/mL, was performed. In addition, in most of the patients, another 12-min period was performed during which the BIS was targeted at 50 +/- 5. After each 12-min steady-state period, the Ct and BIS were noted and the plasma concentration of propofol was measured (Cm). The Ct and Cm corresponding to half maximal effect (BIS(50)) was determined by the Hill equation, and by targeting BIS at 50.
In children, as in adults, BIS values were highly correlated with the corresponding Ct or Cm of propofol following classical E(max) dose-response curves. The ECt(50) and the ECm(50), derived from the dose-response curves, were higher in children than in adults: ECm(50): 4.0 (3.6-4.5) microg/mL vs 3.3 (3.0-3.7) microg/mL mean (95% CI), P < 0.001; as well were the Ct and Cm clinically obtained when BIS was targeted at 50 (Cm(50): 4.3 +/- 1.1 microg/mL vs 3.4 +/- 1.2 microg/mL, (mean +/- SD) P < 0.05, children versus adults). Cm was generally under-estimated by the Ct, and the bias was higher in children than in adults: 2.6 +/- 2.6 microg/mL vs 1.7 +/- 1.6 microg/mL (P = 0.05).
The good relationship between propofol and BIS demonstrated in children as in adults suggested a slightly lower sensitivity to propofol in children. As the predictability of plasma propofol concentrations with the classical pharmacokinetic/pharmacodynamic models is limited in children, a cerebral pharmacodynamic feedback, such as BIS, may be useful in this population.
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.
The clinical benefits to be expected from intraoperative nociception monitors are currently under investigation. Among these devices, the Analgesia Nociception-Index (ANI) has shown promising results ...under sevoflurane anesthesia. Our study investigated ANI-guided remifentanil administration under propofol anesthesia. We hypothesized that ANI guidance would result in reduced remifentanil consumption compared with standard management. This prospective, randomized, controlled, single-blinded, bi-centric study included women undergoing elective gynecologic surgery under target-controlled infusion of propofol and remifentanil. Patients were randomly assigned to an ANI or Standard group. In the ANI group, remifentanil target concentration was adjusted by 0.5 ng mL
steps every 5 min according to the ANI value. In the Standard group, remifentanil was managed according to standard practice. Our primary objective was to compare remifentanil consumption between the groups. Our secondary objectives were to compare the quality of anesthesia, postoperative analgesia and the incidence of chronic pain. Eighty patients were included. Remifentanil consumption was lower in the ANI group: 4.4 (3.3; 5.7) vs. 5.8 (4.9; 7.1) µg kg
h
(difference = -1.4 (95% CI, -2.6 to -0.2),
= 0.0026). Propofol consumption was not different between the groups. Postoperative pain scores were low in both groups. There was no difference in morphine consumption 24 h after surgery. The proportion of patients reporting pain 3 months after surgery was 18.8% in the ANI group and 30.8% in the Standard group (difference = -12.0 (95% CI, -32.2 to 9.2)). ANI guidance resulted in lower remifentanil consumption compared with standard practice under propofol anesthesia. There was no difference in short- or long-term postoperative analgesia.
Monitoring of intraoperative nociception has made substantial progress in adult anesthesia during the last 10 years. Several monitors have been validated and their use has been associated with ...intraoperative or postoperative benefits in the adult population. In pediatric anesthesia, less data are available. However, several recent publications have assessed the performance of nociception monitors in children, and investigated their potential benefits in this context. This review will describe the main validated intraoperative nociception monitors, summarize adult findings and describe the available pediatric data.
Six intraoperative nociception indices were included in this review. Among them, four have shown promising results in children: Surgical Pleth Index (GE-Healthcare, Helsinki, Finland), Analgesia-Nociception Index (Mdoloris Medical Systems, Loos, France), Newborn-Infant Parasympathetic Evaluation (Mdoloris Medical Systems), and Pupillometry (IDMED, Marseille, France). The relevance of Skin Conductance (MedStorm innovations, AS, Oslo, Norway) under general anesthesia could not be established. Finally, the Nociception Level (Medasense, Ramat Gan, Israel) still requires to be investigated in children.
To date, four monitors may provide a relevant assessment of intraoperative nociception in children. However, the potential clinical benefits associated with their use to guide analgesia remain to be demonstrated.
Les histoires mises bout à bout des personnages qui composent Alma forment à la fois une microhistoire de l’île Maurice et l’histoire de l’héritage de la famille Felsen. Alma, le domaine des Felsen a ...fait l’objet d’un détournement d’héritage et Dodo, le personnage principal, devenu errant, a été spolié. A travers son destin symbolique, c’est l’histoire de l’île Maurice, les méfaits de la colonisation et les dégâts plus récents de la pollution que dénonce l’auteur. Les thèmes chers à Le Clézio de la mise en lumière des marginaux et des dominés se dessinent à travers les multiples regards de personnages tyrannisés de diverses manières. Par cette histoire composite et qui traverse les siècles, Le Clézio cherche à responsabiliser les humains, comme l’ont fait une longue lignée d’écrivains avant lui, Montesquieu, Condorcet, Voltaire, Camus, en insistant sur le devoir mémoriel, notamment de l’esclavage, et en dénonçant les terribles ravages écologiques et la maltraitance des faibles.
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