Harnessing machine learning for EEG signal analysis: Innovations in depth of anaesthesia assessment.

Anaesthesia, crucial to surgical practice, is undergoing renewed scrutiny due to the integration of artificial intelligence in its medical use. The precise control over the temporary loss of consciousness is vital to ensure safe, pain-free procedures. Traditional methods of depth of anaesthesia (DoA) assessment, reliant on physical characteristics, have proven inconsistent due to individual variations. In response, electroencephalography (EEG) techniques have emerged, with indices such as the Bispectral Index offering quantifiable assessments. This literature review explores the current scope and frontier of DoA research, emphasising methods utilising EEG signals for effective clinical monitoring. This review offers a critical synthesis of recent advances, specifically focusing on electroencephalography (EEG) techniques and their role in enhancing clinical monitoring. By examining 117 high-impact papers, the review delves into the nuances of feature extraction, model building, and algorithm design in EEG-based DoA analysis. Comparative assessments of these studies highlight their methodological approaches and performance, including clinical correlations with established indices like the Bispectral Index. The review identifies knowledge gaps, particularly the need for improved collaboration for data access, which is essential for developing superior machine learning models and real-time predictive algorithms for patient management. It also calls for refined model evaluation processes to ensure robustness across diverse patient demographics and anaesthetic agents. The review underscores the potential of technological advancements to enhance precision, safety, and patient outcomes in anaesthesia, paving the way for a new standard in anaesthetic care. The findings of this review contribute to the ongoing discourse on the application of EEG in anaesthesia, providing insights into the potential for technological advancement in this critical area of medical practice.

Real-Time Depth of Anaesthesia Assessment Based on Hybrid Statistical Features of EEG.

This paper proposed a new depth of anaesthesia (DoA) index for the real-time assessment of DoA using electroencephalography (EEG). In the proposed new DoA index, a wavelet transform threshold was applied to denoise raw EEG signals, and five features were extracted to construct classification models. Then, the Gaussian process regression model was employed for real-time assessment of anaesthesia states. The proposed real-time DoA index was implemented using a sliding window technique and validated using clinical EEG data recorded with the most popular commercial DoA product Bispectral Index monitor (BIS). The results are evaluated using the correlation coefficients and Bland-Altman methods. The outcomes show that the highest and the average correlation coefficients are 0.840 and 0.814, respectively, in the testing dataset. Meanwhile, the scatter plot of Bland-Altman shows that the agreement between BIS and the proposed index is 94.91%. In contrast, the proposed index is free from the electromyography (EMG) effect and surpasses the BIS performance when the signal quality indicator (SQI) is lower than 15, as the proposed index can display high correlation and reliable assessment results compared with clinic observations.

Assessment of phase-lag entropy, a new measure of electroencephalographic signals, for propofol-induced sedation.

BACKGROUND: Phase-lag entropy (PLE) was recently described as a measurement of temporal pattern diversity in the phase relationship between two electroencephalographic signals from prefrontal and frontal montages. This study was performed to evaluate the performance of PLE for assessing the depth of sedation. METHODS: Thirty adult patients undergoing upper limb surgery with a brachial plexus block were administered propofol by target-controlled infusion. The depth of sedation was assessed using the Observer's Assessment of Alertness/Sedation (OAA/S) scale. The effect-site concentration (Ce) of propofol was initially started at 0.5 µg/ml and was increased in increments of 0.2 µg/ml until an OAA/S score of 1 was reached. Three minutes after the target Ce was reached, the PLE, bispectral index (BIS), and level of sedation were assessed. Correlations between the OAA/S score and PLE or BIS were determined. The prediction probabilities (Pk) of PLE and BIS were also analyzed. RESULTS: The PLE values were closely correlated with the OAA/S scores (Spearman's Rho = 0.755; P < 0.001) to an extent comparable with the correlation between the BIS and OAA/S score (Spearman's Rho = 0.788; P < 0.001). The Pk values of PLE and BIS were 0.731 and 0.718, respectively. CONCLUSIONS: PLE is a new and reliable consciousness monitoring system for assessing the depth of sedation induced by propofol, which is comparable with the BIS.

Cost-effectiveness of anesthesia maintained with sevoflurane or propofol with and without additional monitoring: a prospective, randomized controlled trial.

BACKGROUND: We compared cost-effectiveness of anesthesia maintained with sevoflurane or propofol with and without additional monitoring, in the clinical setting of ear-nose-throat surgery. METHODS: One hundred twenty adult patients were randomized to four groups. In groups SEVO and SEVO+ anesthesia was maintained with sevoflurane, in group SEVO+ with additional bispectral index (BIS) and train-of-four (TOF) monitoring. In groups PROP and PROP+ anesthesia was maintained with propofol, in group PROP+ with additional BIS and TOF monitoring. RESULTS: Total cost of anesthesia per hour was greater in group SEVO+ compared to SEVO [€ 19.95(8.53) vs. 12.15(5.32), p <  0.001], and in group PROP+ compared to PROP (€ 22.11(8.08) vs. 13.23(4.23), p <  0.001]. Time to extubation was shorter in group SEVO+ compared to SEVO [11.1(4.7) vs. 14.5(3.9) min, p = 0.002], and in PROP+ compared to PROP [12.6(5.4) vs. 15.2(4.7) min, p <  0.001]. Postoperatively, arterial blood pressure returned to its initial values sooner in groups SEVO+ and PROP+. CONCLUSIONS: Our study demonstrated that the use of BIS and TOF monitoring decreased the total cost of anesthesia drugs and hastened postoperative recovery. However, in our circumstances, these were associated with higher disposables costs. Detailed cost analysis and further investigations are needed to identify patient populations who would benefit most from additional monitoring. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02920749 . Retrospectively registered (date of registration September 2016).

BIS monitoring versus clinical assessment for sedation in mechanically ventilated adults in the intensive care unit and its impact on clinical outcomes and resource utilization.

BACKGROUND: Patients admitted to intensive care and on mechanical ventilation, are administered sedative and analgesic drugs to improve both their comfort and interaction with the ventilator. Optimizing sedation practice may reduce mortality, improve patient comfort and reduce cost. Current practice is to use scales or scores to assess depth of sedation based on clinical criteria such as consciousness, understanding and response to commands. However these are perceived as subjective assessment tools. Bispectral index (BIS) monitors, which are based on the processing of electroencephalographic signals, may overcome the restraints of the sedation scales and provide a more reliable and consistent guidance for the titration of sedation depth.The benefits of BIS monitoring of patients under general anaesthesia for surgical procedures have already been confirmed by another Cochrane review. By undertaking a well-conducted systematic review our aim was to find out if BIS monitoring improves outcomes in mechanically ventilated adult intensive care unit (ICU) patients. OBJECTIVES: To assess the effects of BIS monitoring compared with clinical sedation assessment on ICU length of stay (LOS), duration of mechanical ventilation, any cause mortality, risk of ventilator-associated pneumonia (VAP), risk of adverse events (e.g. self-extubation, unplanned disconnection of indwelling catheters), hospital LOS, amount of sedative agents used, cost, longer-term functional outcomes and quality of life as reported by authors for mechanically ventilated adults in the ICU. SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, CINAHL, ProQuest, OpenGrey and SciSearch up to May 2017 and checked references citation searching and contacted study authors to identify additional studies. We searched trial registries, which included clinicaltrials.gov and controlled-trials.com. SELECTION CRITERIA: We included all randomized controlled trials comparing BIS versus clinical assessment (CA) for the management of sedation in mechanically ventilated critically ill adults. DATA COLLECTION AND ANALYSIS: We used Cochrane's standard methodological procedures. We undertook analysis using Revman 5.3 software. MAIN RESULTS: We identified 4245 possible studies from the initial search. Of those studies, four studies (256 participants) met the inclusion criteria. One more study is awaiting classification. Studies were, conducted in single-centre surgical and mixed medical-surgical ICUs. BIS monitor was used to assess the level of sedation in the intervention arm in all the studies. In the control arm, the sedation assessment tools for CA included the Sedation-Agitation Scale (SAS), Ramsay Sedation Scale (RSS) or subjective CA utilizing traditional clinical signs (heart rate, blood pressure, conscious level and pupillary size). Only one study was classified as low risk of bias, the other three studies were classified as high risk.There was no evidence of a difference in one study (N = 50) that measured ICU LOS (Median (Interquartile Range IQR) 8 (4 to 14) in the CA group; 12 (6 to 18) in the BIS group; low-quality evidence).There was little or no effect on the duration of mechanical ventilation (MD -0.02 days (95% CI -0.13 to 0.09; 2 studies; N = 155; I2 = 0%; low-quality evidence)). Adverse events were reported in one study (N = 105) and the effects on restlessness after suction, endotracheal tube resistance, pain tolerance during sedation or delirium after extubation were uncertain due to very low-quality evidence. Clinically relevant adverse events such as self-extubation were not reported in any study. Three studies reported the amount of sedative agents used. We could not measure combined difference in the amount of sedative agents used because of different sedation protocols and sedative agents used in the studies. GRADE quality of evidence was very low. No study reported other secondary outcomes of interest for the review. AUTHORS' CONCLUSIONS: We found insufficient evidence about the effects of BIS monitoring for sedation in critically ill mechanically ventilated adults on clinical outcomes or resource utilization. The findings are uncertain due to the low- and very low-quality evidence derived from a limited number of studies.

Effect-Site Target-Controlled Infusion in the Obese: Model Derivation and Performance Assessment.

BACKGROUND: The aim of this study is to derive a propofol pharmacokinetic (PK) pharmacodynamic (PD) model to perform effect-site target-controlled infusion (TCI) in obese patients, and to analyze its performance along with that of other available PK models. METHODS: In the first step of the study, a 3-compartment PK model linked to a sigmoidal inhibitory Emax PD model by a first-order rate constant (keo) was used to fit propofol concentration-bispectral index (BIS) data. Population modeling analysis was performed by nonlinear mixed effects regression in NONMEM (ICON, Dublin, Ireland). PK data from 3 previous studies in obese adult patients (n = 47), including PD (BIS) data from 1 of these studies (n = 20), were pooled and simultaneously analyzed. A decrease in NONMEM objective function (ΔOBJ) of 3.84 points, for an added parameter, was considered significant at the 0.05 level. In the second step of the study, we analyzed the predictive performance (median predictive errors [MDPE] and median absolute predictive errors [MDAPE]) of the current model and of other available models using an independent data set (n = 14). RESULTS: Step 1: The selected PKPD model produced an adequate fit of the data. Total body weight resulted in the best size scalar for volumes and clearances (ΔOBJ, -18.173). Empirical allometric total body weight relationships did not improve model fit (ΔOBJ, 0.309). A lag time parameter for BIS response improved the fit (ΔOBJ, 89.593). No effect of age or gender was observed. Step 2: Current model MDPE and MDAPE were 11.5% (3.7-25.0) and 26.8% (20.7-32.6) in the PK part and 0.4% (-10.39 to 3.85) and 11.9% (20.7-32.6) in the PD part. The PK model developed by Eleveld et al resulted in the lowest PK predictive errors (MDPE = <10% and MDAPE = <25%). CONCLUSIONS: We derived and validated a propofol PKPD model to perform effect-site TCI in obese patients. This model, derived exclusively from obese patient's data, is not recommended for TCI in lean patients because it carries the risk of underdosing.

The Technology of Processed Electroencephalogram Monitoring Devices for Assessment of Depth of Anesthesia.

Commercial brain function monitors for depth of anesthesia have been available for more than 2 decades; there are currently more than 10 devices on the market. Advances in this field are evidenced by updated versions of existing monitors, development of new monitors, and increasing research unveiling the mechanisms of anesthesia on the brain. Electroencephalography signal processing forms an integral part of the technology supporting the brain function monitors for derivation of a depth-of-anesthesia index. This article aims to provide a better understanding of the technology and functionality behind these monitors. This review will highlight the general design principles of these devices and the crucial stages in electroencephalography signal processing and classification, with a focus on the key mathematical techniques used in algorithm development for final derivation of the index representing anesthetic state. We will briefly discuss the advantages and limitations of this technology in the clinical setting as a tool in our repertoire used for optimizing individualized patient care. Also included is a table describing 10 available commercial depth-of-anesthesia monitors.

Assessment of sedation level prior to neonatal intubation: A systematic review.

BACKGROUND: Adequate premedication before neonatal endotracheal intubation reduces pain, stress, and adverse physiological responses, diminishes duration and number of attempts at intubation, and prevents traumatic airway injury. Therefore, intubation should not be started until an adequate level of sedation is reached. It is not clear how this should be measured in the clinical situation. OBJECTIVES: The aim of this study is to provide a systematic review of the usability and validity of scoring systems or other objective parameters to evaluate the level of sedation before intubation in neonates. Secondary aims were to describe parameters that are used to determine the level of sedation and criteria on which the decision to proceed with intubation is based. METHODS: Literature was searched (January 2017) in the following electronic databases: Embase, Medline, Web of Science, Cochrane Central Registrar of Controlled Trials, Pubmed Publisher, and Google Scholar. RESULTS: From 1653 hits, 20 studies were finally included in the systematic review. In 7 studies, intubation was started after a predefined time period; in 1 study, preoxygenation was the criterion to start with intubation; and in 12 studies, intubation was started in case of adequate sedation and/or relaxation. Only 4 studies described the use of 3 different objective scoring system, all in the neonatal intensive care unit, which are not validated. CONCLUSION: No validated scoring systems to assess the level of sedation prior to intubation in newborns are available in the literature. Three objective sedation assessment tools seem promising but need further validation before they can be implemented in research and clinical settings.

Postoperative surveillance in neurosurgical patients - usefulness of neurological assessment scores and bispectral index / Monitoramento de pacientes neurocirúrgicos no pós-operatório - utilidade dos escores de avaliação neurológica e do índice bispectral

Abstract Background and objectives: We examined the additive effect of the Ramsay scale, Canadian Neurological Scale (CNS), Nursing Delirium Screening Scale (Nu-DESC), and Bispectral Index (BIS) to see whether along with the assessment of pupils and Glasgow Coma Scale (GCS) it improved early detection of postoperative neurological complications. Methods: We designed a prospective observational study of two elective neurosurgery groups of patients: craniotomies (CG) and non-craniotomies (NCG). We analyze the concordance and the odds ratio (OR) of altered neurological scales and BIS in the Post-Anesthesia Care Unit (PACU) for postoperative neurological complications. We compared the isolated assessment of pupils and GCS (pupils-GCS) with all the neurologic assessment scales and BIS (scales-BIS). Results: In the CG (n = 70), 16 patients (22.9%) had neurological complications in PACU. The scales-BIS registered more alterations than the pupils-GCS (31.4% vs. 20%; p < 0.001), were more sensitive (94% vs. 50%) and allowed a more precise estimate for neurological complications in PACU (p = 0.002; OR = 7.15, 95% CI = 2.1-24.7 vs. p = 0.002; OR = 9.5, 95% CI = 2.3-39.4). In the NCG (n = 46), there were no neurological complications in PACU. The scales-BIS showed alterations in 18 cases (39.1%) versus 1 (2.2%) with the pupils-GCS (p < 0.001). Altered CNS on PACU admission increased the risk of neurological complications in the ward (p = 0.048; OR = 7.28, 95% CI = 1.021-52.006). Conclusions: Applied together, the assessment of pupils, GCS, Ramsay scale, CNS, Nu-DESC and BIS improved early detection of postoperative neurological complications in PACU after elective craniotomies.

Resumo Justificativa e objetivos: Avaliamos o efeito aditivo da escala de Ramsay, Escala Neurológica Canadense (CNS), Escala da Enfermagem de Triagem de Delírio (Nu-DESC) e Índice Bispectral (BIS) para observar se, juntamente com a avaliação das pupilas e da Escala de Coma de Glasgow (GCS), melhorava a detecção precoce de complicações neurológicas no pós-operatório. Métodos: Projetamos um estudo observacional, prospectivo, de dois grupos de pacientes submetidos à neurocirurgia eletiva: craniotomia (Grupo C) e não craniotomia (Grupo NC). Analisamos a concordância e a razão de chance (OR) de alterações nas escalas neurológicas e no BIS na sala de recuperação pós-anestesia (SRPA) para complicações neurológicas no pós-operatório. Comparamos a avaliação isolada das pupilas e da GCS (pupilas-GCS) com todas as escalas de avaliação neurológica e o BIS (escalas-BIS). Resultados: No Grupo C (n = 70), 16 pacientes (22,9%) apresentaram complicações neurológicas na SRPA. As escalas-BIS registraram mais alterações do que as pupilas-GCS (31,4% vs. 20%; p < 0,001), foram mais sensíveis (94% vs. 50%) e permitiram uma estimativa mais precisa das complicações neurológicas na SRPA (p = 0,002; OR = 7,15, IC 95% = 2,1-24.7 vs. p = 0,002; OR = 9,5, IC 95% = 2,3-39,4). No grupo NC (n = 46) não houve complicações neurológicas na SRPA. As escalas-BIS mostraram alterações em 18 casos (39,1%) versus um caso (2,2%) com as pupilas-GCS (p < 0,001). Alteração na CNS na admissão à SRPA aumentou o risco de complicações neurológicas na enfermaria (p = 0,048; OR = 7,28, IC 95% = 1,021-52,006). Conclusões: Aplicados em conjunto, avaliação das pupilas, GCS, escala de Ramsay, CNS, Nu-DESC e BIS melhoraram a detecção precoce de complicações neurológicas no pós-operatório na SRPA após craniotomias eletivas.

Postoperative surveillance in neurosurgical patients - usefulness of neurological assessment scores and bispectral index.

BACKGROUND AND OBJECTIVES: We examined the additive effect of the Ramsay scale, Canadian Neurological Scale (CNS), Nursing Delirium Screening Scale (Nu-DESC), and Bispectral Index (BIS) to see whether along with the assessment of pupils and Glasgow Coma Scale (GCS) it improved early detection of postoperative neurological complications. METHODS: We designed a prospective observational study of two elective neurosurgery groups of patients: craniotomies (CG) and non-craniotomies (NCG). We analyze the concordance and the odds ratio (OR) of altered neurological scales and BIS in the Post-Anesthesia Care Unit (PACU) for postoperative neurological complications. We compared the isolated assessment of pupils and GCS (pupils-GCS) with all the neurologic assessment scales and BIS (scales-BIS). RESULTS: In the CG (n=70), 16 patients (22.9%) had neurological complications in PACU. The scales-BIS registered more alterations than the pupils-GCS (31.4% vs. 20%; p<0.001), were more sensitive (94% vs. 50%) and allowed a more precise estimate for neurological complications in PACU (p=0.002; OR=7.15, 95% CI=2.1-24.7 vs. p=0.002; OR=9.5, 95% CI=2.3-39.4). In the NCG (n=46), there were no neurological complications in PACU. The scales-BIS showed alterations in 18 cases (39.1%) versus 1 (2.2%) with the pupils-GCS (p<0.001). Altered CNS on PACU admission increased the risk of neurological complications in the ward (p=0.048; OR=7.28, 95% CI=1.021-52.006). CONCLUSIONS: Applied together, the assessment of pupils, GCS, Ramsay scale, CNS, Nu-DESC and BIS improved early detection of postoperative neurological complications in PACU after elective craniotomies.

[Postoperative surveillance in neurosurgical patients - usefulness of neurological assessment scores and bispectral index]. / Monitoramento de pacientes neurocirúrgicos no pós­operatório ­ utilidade dos escores de avaliação neurológica e do índice bispectral.

BACKGROUND AND OBJECTIVES: We examined the additive effect of the Ramsay scale, Canadian Neurological Scale (CNS), Nursing Delirium Screening Scale (Nu-DESC), and Bispectral Index (BIS) to see whether along with the assessment of pupils and Glasgow Coma Scale (GCS) it improved early detection of postoperative neurological complications. METHODS: We designed a prospective observational study of two elective neurosurgery groups of patients: craniotomies (CG) and non-craniotomies (NCG). We analyze the concordance and the odds ratio (OR) of altered neurological scales and BIS in the Post-Anesthesia Care Unit (PACU) for postoperative neurological complications. We compared the isolated assessment of pupils and GCS (pupils-GCS) with all the neurologic assessment scales and BIS (scales-BIS). RESULTS: In the CG (n=70), 16 patients (22.9%) had neurological complications in PACU. The scales-BIS registered more alterations than the pupils-GCS (31.4% vs. 20%; p<0.001), were more sensitive (94% vs. 50%) and allowed a more precise estimate for neurological complications in PACU (p=0.002; OR=7.15, 95% CI=2.1-24.7 vs. p=0.002; OR=9.5, 95% CI=2.3-39.4). In the NCG (n=46), there were no neurological complications in PACU. The scales-BIS showed alterations in 18 cases (39.1%) versus 1 (2.2%) with the pupils-GCS (p<0.001). Altered CNS on PACU admission increased the risk of neurological complications in the ward (p=0.048; OR=7.28, 95% CI=1.021-52.006). CONCLUSIONS: Applied together, the assessment of pupils, GCS, Ramsay scale, CNS, Nu-DESC and BIS improved early detection of postoperative neurological complications in PACU after elective craniotomies.

Determination of loss of consciousness: a comparison of clinical assessment, bispectral index and electroencephalogram: An observational study.

BACKGROUND: Computer-processed algorithms of encephalographic signals are widely used to assess the depth of anaesthesia. However, data indicate that the bispectral index (BIS), a processed electroencephalography monitoring system, may not be reliable for assessing the depth of anaesthesia. OBJECTIVE: The aim of this study was to evaluate the ability of the BIS monitoring system to assess changes in the level of unconsciousness, specifically during the transition from consciousness to unconsciousness, in patients undergoing total intravenous anaesthesia with propofol. We compared BIS with the electroencephalogram (EEG), and clinical loss of consciousness (LOC) defined as loss of verbal commands and eyelash reflex. DESIGN: This was an observational cohort study. SETTING: University Hospital Linköping, University Hospital Örebro, Finspång Hospital and Kalmar Hospital, Sweden from October 2011 to April 2013. PATIENTS: A total of 35 ASA I patients aged 18 to 49 years were recruited. INTERVENTIONS: The patients underwent total intravenous anaesthesia with propofol and remifentanil for elective day-case surgery. Changes in clinical levels of consciousness were assessed by BIS and compared with assessment of stage 3 neurophysiological activity using the EEG. The plasma concentrations of propofol were measured at clinical LOC and 20 and 30 min after LOC. MAIN OUTCOME MEASURES: The primary outcome was measurement of BIS, EEG and clinical LOC. RESULTS: The median BIS value at clinical LOC was 38 (IQR 30 to 43), and the BIS values varied greatly between patients. There was no correlation between BIS values and EEG stages at clinical LOC (r = -0.1, P = 0.064). Propofol concentration reached a steady state within 20 min. CONCLUSION: There was no statistically significant correlation between BIS and EEG at clinical LOC. BIS monitoring may not be a reliable method for determining LOC. CLINICAL TRIALS REGISTRY: This trial was not registered because registration was not mandatory at the time of the trial.

Depth of anaesthesia assessment based on adult electroencephalograph beta frequency band.

This paper presents a new method to apply timing characteristics of electroencephalograph (EEG) beta frequency bands to assess the depth of anaesthesia (DoA). Firstly, the measured EEG signals are denoised and decomposed into 20 different frequency bands. The Mobility (M), permutation entropy (PE) and Lempel-Ziv complexity (LCZ) of each frequency band are calculated. The M, PE and LCZ values of beta frequency bands (21.5-30 Hz) are selected to derive a new index. The new index is evaluated and compared with measured bispectral (BIS). The results show that there is a very close correlation between the proposed index and the BIS during different anaesthetic states. The new index also shows a 25-264 s earlier time response than BIS during the transient period of anaesthetic states. In addition, the proposed index is able to continuously assess the DoA when the quality of signal is poor and the BIS does not have any valid outputs.

Refining Target-Controlled Infusion: An Assessment of Pharmacodynamic Target-Controlled Infusion of Propofol and Remifentanil Using a Response Surface Model of Their Combined Effects on Bispectral Index.

BACKGROUND: Propofol and remifentanil are commonly combined for total IV anesthesia. The pharmacokinetics (PK), pharmacodynamics (PD), and drug interactions of the combination are well understood, but the use of a combined PK and PD model to control target-controlled infusion pumps has not been investigated. In this study, we prospectively tested the accuracy of a PD target-controlled infusion algorithm for propofol and remifentanil using a response surface model of their combined effects on Bispectral Index (BIS). METHODS: Effect-site, target-controlled infusions of propofol and remifentanil were given using an algorithm based on standard PK models linked to a PD response surface model of their combined effects on BIS. The combination of a targeted BIS value and adjustable ratio of propofol to remifentanil was used to adjust infusion rates. The standard model performance measures of median performance error (bias) and median absolute performance error (inaccuracy), expressed as percentages, were used to assess accuracy of the infusions in a convenience sample of 50 adult patients undergoing surgery with general anesthesia. The influence of age and weight on the performance of the model was also assessed. RESULTS: Patients had a mean (range) age of 48 (19-73) years, weight of 80 (45-169) kg, and body mass index of 28 (19-45) kg/m. The overall model had a bias of 8% (SD 24%) and inaccuracy of 25% (SD 13%). Performance was least accurate during the early induction phase of anesthesia. There was no significant bias in BIS predictions with increasing age (P = 0.44) or weight (P = 0.56). CONCLUSIONS: The algorithm performed adequately in a clinical setting. The algorithm could be further refined, and assessment of its accuracy and utility in comparison to current clinical practice for giving IV anesthesia is warranted.

Preexisting cognitive impairment is associated with postoperative cognitive dysfunction after hip joint replacement surgery.

BACKGROUND: This study investigated the prevalence of cognitive impairment in elderly noncardiac surgery patients and any association between preoperative cognitive impairment and postoperative cognitive dysfunction (POCD). Additionally, the incidence of cognitive decline at 12 months after surgery was identified. METHODS: Three hundred patients for hip joint replacement and 51 nonsurgical controls aged 60 yr or older were studied in a prospective observational clinical trial. All study participants and controls completed a battery of eight neuropsychological tests before surgery and at 7 days, 3 months, and 12 months afterwards. Preoperative cognitive status was assessed using preexisting cognitive impairment (PreCI) defined as a decline of at least 2 SD on two or more of seven neuropsychological tests compared to population norms. POCD and cognitive decline were assessed using the reliable change index utilizing the results of the control group. RESULTS: PreCI was classified in 96 of 300 (32%) patients (95% CI, 23 to 43%). After surgery, 49 of 286 (17%) patients (95% CI, 13 to 22%) and 27 of 284 (10%) patients (95% CI, 6 to 13%) demonstrated POCD at 7 days and 3 months, respectively, while 7 of 271 (3%) patients (95% CI, 1 to 4%) demonstrated cognitive decline at 12 months. Patients with PreCI had a significantly increased incidence of POCD at 7 days and 3 months and cognitive decline at 12 months. CONCLUSIONS: Patients with PreCI have an increased incidence of POCD and cognitive decline. PreCI is a good predictor of subsequent POCD and cognitive decline. The incidence of cognitive decline after 12 months in this group of patients is low.

Sedation assessment in a mobile intensive care unit: a prospective pilot-study on the relation of clinical sedation scales and the bispectral index.

INTRODUCTION: The critically-ill undergoing inter-hospital transfers commonly receive sedatives in continuation of their therapeutic regime or to facilitate a safe transfer shielded from external stressors. While sedation assessment is well established in critical care in general, there is only little data available relating to the special conditions during patient transport and their effect on patient sedation levels. The aim of this prospective study was to investigate the feasibility and relationship of clinical sedation assessment (Richmond Agitation-Sedation Scale (RASS)) and objective physiological monitoring (bispectral index (BIS)) during patient transfers in our Mobile-ICU. METHODS: The levels of sedation of 30 pharmacologically sedated patients were evaluated at 12 to 17 distinct measurement points spread strategically over the course of a transfer by use of the RASS and BIS. To investigate the relation between the RASS and the BIS, Spearman's squared rank correlation coefficient (ρ(2)) and the Kendall's rank correlation coefficient (τ) were calculated. The diagnostic value of the BIS with respect to the RASS was investigated by its sensitivity and positive predictive value for possible patient awakening. Therefore, measurements were dichotomized considering a clinically sensible threshold of 80 for BIS-values and classifying RASS values being nonnegative. RESULTS: Spearman's rank correlation resulted to ρ(2) = 0.431 (confidence interval (CI) = 0.341 to 0.513). The Kendall's correlation coefficient was calculated as τ = 0.522 (CI = 0.459 to 0.576). Awakening of patients (RASS ≥ 0) was detected by a BIS value of 80 and above with a sensitivity of 0.97 (CI = 0.89 to 1.00) and a positive predictive value of 0.59 (CI = 0.45 to 0.71). CONCLUSIONS: Our study demonstrates that the BIS-Monitor can be used for the assessment of sedation levels in the intricate environment of a Mobile-ICU, especially when well-established clinical scores as the RASS are impracticable. The use of BIS is highly sensitive in the detection of unwanted awakening of patients during transfers.

Bispectral Index Monitoring: validity and utility in pediatric dentistry.

Reliable and safe provision of sedation and general anesthesia is dependent on continuous vigilance of patient's sedation depth. Failure to do so may result in unintended oversedation or undersedation. It is a common practice to observe sedation depth by applying subjective sedation scales and in case of general anesthesia, practitioner is dependent on vital sign assessment. The Bispectral Index System (BIS) is a recently introduced objective, quantitative, easy to use, and free from observer bias, and clinically useful tool to assess sedation depth and it precludes the need to stimulate the patient to assess his sedation level. The present article is an attempt to orient the readers towards utility and validity of BIS for sedation and general anesthesia in pediatric dentistry. In this article, we attempt to make the readers understand the principle of BIS, its variation across sedation continuum, its validity across different age groups and for a variety of sedative drugs.

Avaliação do nível de consciência de recém-nascidos com asfixia neonatal. Proposta para unidades de tratamentos intensivos neonatais / Level consciousness?s assessment of newborn with neonatal asphyxia: a proposal for neonatal intensive care units

A asfixia perinatal se constitui em uma das três principais causas de mortalidade neonatal. A encefalopatia hipóxico-isquêmica (EHI) é causada pela associação entre a hipóxia sanguínea e a isquemia tecidual. Esta associação, acompanhada de alterações metabólicas, resulta em manifestações clínicas secundárias ao comprometimento fisiológico ou estrutural, com disfunção múltipla de órgãos e presença de lesão cerebral grave. Acomete cerca de 50% a 60% dos recém-nascidos com asfixia perinatal. O objetivo do trabalho foi realizar uma revisão da literatura sobre asfixia neonatal. Foi realizada busca de artigos científicos através das bases de dados Lilacs, SciELO e Medline, utilizando as palavras-chave do trabalho, além de pesquisa adicional em bancos de dados de dissertações, teses e livros texto, em publicações do período de 1974 a 2013. Uma atuação preventiva, através da identificação e do tratamento precoce da lesão cerebral, constitui-se em estratégia efetiva para minimizar sequelas e promover melhor qualidade de vida em longo prazo...

Clinical effectiveness and cost-effectiveness of depth of anaesthesia monitoring (E-Entropy, Bispectral Index and Narcotrend): a systematic review and economic evaluation.

BACKGROUND: It is important that the level of general anaesthesia (GA) is appropriate for the individual patient undergoing surgery. If anaesthesia is deeper than required to keep a patient unconscious, there might be increased risk of anaesthetic-related morbidity, such as postoperative nausea, vomiting and cognitive dysfunction. This may also prolong recovery times, potentially increasing health-care costs. If anaesthesia is too light, patients may not be fully unconscious and could be at risk of intraoperative awareness. OBJECTIVE: The objective of this report is to assess the clinical effectiveness and cost-effectiveness of Bispectral Index (BIS), E-Entropy and Narcotrend technologies, each compared with standard clinical monitoring, to monitor the depth of anaesthesia in surgical patients undergoing GA. DATA SOURCES: A search strategy was developed and run on a number of bibliographic electronic databases including MEDLINE, EMBASE, The Cochrane Library and the Health Technology Assessment (HTA) database. For the systematic review of patient outcomes, databases were searched from the beginning of 2009 to November 2011 for studies of BIS (and then updated in February 2012), and from 1995 to November 2011 (and then updated in February 2012) for studies of E-Entropy and Narcotrend. For the systematic review of cost-effectiveness, searches were from database inception to November 2011 (an update search was performed in February 2012). REVIEW METHODS: The systematic review of patient outcomes followed standard methodology for evidence synthesis. A decision-analytic model was developed to assess the cost-effectiveness of depth of anaesthesia monitoring compared with standard clinical observation. A simple decision tree was developed, which accounted for patients' risk of experiencing short-term anaesthetic-related complications in addition to risk of experiencing intraoperative awareness. RESULTS: Twenty-two randomised controlled trials comparing BIS, E-Entropy and Narcotrend with standard clinical monitoring were included in the systematic review of patient outcomes, alongside evidence from a recent Cochrane review. Six trials of patients classified with risk factors for intraoperative awareness were combined in a fixed-effect meta-analysis. The overall pooled Peto's odds ratio was 0.45 (95% confidence interval 0.25 to 0.81) in favour of BIS. However, there was statistically significant heterogeneity. The base-case cost per quality-adjusted life-year (QALY) for BIS compared with standard clinical monitoring ranged from £22,339 to £44,198 depending on patient subgroups (type of GA received; level of risk for awareness). For E-Entropy, base-case estimates ranged from £14,421 to £31,430. For Narcotrend, estimates varied from a cost per QALY of £8033 to Narcotrend dominating standard clinical monitoring. LIMITATIONS: The analysis was limited by lack of clinical effectiveness data, particularly for E-Entropy and Narcotrend. CONCLUSIONS: The available evidence on the impact of the technologies on reducing the likelihood of intraoperative awareness is limited. However, there were reductions in general anaesthetic consumption and anaesthetic recovery times. The cost-effectiveness of depth of anaesthesia monitoring appears to be highly dependent on a number of factors, including probability of awareness. STUDY REGISTRATION: PROSPERO registration number CRD42011001834. FUNDING: The National Institute for Health Research Health Technology Assessment programme.