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Background: The Bispectral Index (BIS) and the Patient State Index (PSI) are commonly used measures to assess intraoperative sedation depth. However, model differences lead to different results, which in turn interferes with clinicians' judgment on the depth of anesthesia. Remimazolam tosilate (RT) for injection is a new benzodiazepine used in sedation. In its clinical application, there are few effective indicators for sedation depth monitoring. To close this gap, this study aims to compare BIS and PSI in measuring the sensitivity and specificity of intraoperative RT and to explore the safety of RT for intraspinal anesthesia in elderly patients., Methods: This study included 40 patients undergoing elective electro-prostatectomy with intraspinal anesthesia, who were monitored by BIS and PSI simultaneously during operation. Remimazolam tosylate 0.1 mg/kg was intravenously administered after the intraspinal anesthesia when patients were in a completely painless status. Then BIS, PSI, the Modified Observer's Assessment of Alertness and Sedation (MOAA/S) scores and vital signs were observed and recorded per minute for 10 min. Pearson's correlation analysis and linear regression model were used to compare BIS and PSI sedation scores, and to test their associations with the MOAA/S score, respectively. ROC curves were drawn to compare the sensitivity and specificity of BIS and PSI. Changes of vital signs were presented as mean ± standard deviation. Perioperative liver and kidney function indicators were analyzed using a paired t-test to evaluate the safety of RT for intraspinal anesthesia in the elderly patients., Results: According to Pearson's correlation analysis, a significant (P < 0.01) correlation between BIS and PSI was found when used to monitor intraoperative sedation of RT (r = 0.796). Significant associations between BIS and MOAA/S (r = 0.568, P < 0.01), and between PSI and MOAA/S (r = 0.390, P < 0.01) were also found. The areas under the ROC curves of BIS and PSI were 0.801 ± 0.022 and 0.734 ± 0.026, respectively, suggesting that both measures may predict patients' state of consciousness and BIS was more accurate than PSI. Vital signs remained stable throughout the study. No abnormal changes of clinical significance were found based on laboratory test results of liver and kidney function., Conclusion: BIS and PSI are strongly associated for monitoring the sedation of RT intraoperatively. Both methods can accurately reflect sedation depth. According to correlation analyses with MOAA/S scale and ROC curves, BIS is more accurate than PSI during such intraoperative monitoring. In addition, RT can be safely used in elderly patients under intraspinal anesthesia for supportive sedation, with stable vital signs and sound kidney and liver safety profiles., Trial Registration: http://www.chictr.org.cn (ChiCTR2100051912)., (© 2023. The Author(s).)

Objective: To examine the effect of bispectral index (BIS)-guided anesthesia on the incidence of postoperative delirium (POD) in elderly patients undergoing surgery., Design: A systematic review, meta-analysis, and trial sequential analysis (TSA)., Setting: In the operating room, postoperative anesthesia care units (PACU), and ward., Participants: Elderly patients (>60 years old) undergoing surgery., Interventions: The EMBASE, MEDLINE, and CENTRAL databases were searched systematically from their inception until December 2020 for randomized controlled trials comparing BIS and usual care or blinded BIS., Measurements and Main Results: Ten trials (N = 3,891) were included for quantitative meta-analysis. In comparison to the control group, there was no significant difference in the incidence of POD in elderly patients randomized to BIS-guided anesthesia (odds ratio [OR] 0.71, 95% CI 0.47-1.08, I 2  = 76%, p = 0.11, level of evidence = very low, TSA = inconclusive). The authors' review demonstrated that elderly patients with BIS-guided anesthesia were significantly associated with a lower incidence of postoperative cognitive dysfunction (POCD) (OR 0.64, 95% CI 0.46-0.88, p = 0.006), extubation time (mean difference [MD] -3.38 minutes, 95% CI -4.38 to -2.39, p < 0.00001), time to eye opening (MD -2.17 minutes, 95% CI -4.21 to -0.14, p = 0.04), and time to discharge from the PACU (MD -10.77 minutes, 95% CI -11.31 to - 10.23, p < 0.00001)., Conclusion: The authors' meta-analysis demonstrated that BIS-guided anesthesia was not associated with a reduced incidence of POD, but it was associated with a reduced incidence of POCD and improved recovery parameters., Competing Interests: Conflicts of Interest None., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Monitoring depth of anaesthesia (DoA) from electroencephalograph (EEG) signals is an ongoing challenge for anaesthesiologists. In this study, we propose an intelligence model that predicts the DoA from a single channel electroencephalograph (EEG) signal. A segmentation technique based on a sliding window is employed to partition EEG signals. Hierarchical dispersion entropy (HDE) is applied to each EEG segment. A set of features is extracted from each EEG segment. The extracted features are investigated using a community graph detection approach (CGDA), and the most relevant features are selected to trace the DoA. The proposed model, based on HDE coupled with CGDA, is evaluated in term of BIS index using several statistical metrics such Q-Q plot, regression, and correlation coefficients. In addition, the proposed model is evaluated against the BIS index in the case of the poor signal quality. The results demonstrated that the proposed model showed an earlier reaction compared with the BIS index when patient's state transits from deep anaesthesia to moderate anaesthesia in the case of poor signal quality. The highest Pearson correlation coefficient obtained by the proposed is 0.96., (© 2022. The Author(s).)

Objective: To compare the accuracy, correlation and agreement between the bispectral index (BIS) and BISpro during propofol anaesthesia., Methods: The BIS, BISpro, heart rate, target-concentration of propofol and Observer's Assessment of Alertness and Sedation (OAA/S) score were recorded every 30 s in female patients scheduled for hysteroscopic surgery. Propofol anaesthesia was induced by an initial target-controlled concentration (1.0 μg/ml) followed by a stepwise increase (0.5 μg/ml) until the patient was unresponsive. Spearman's correlation coefficient and prediction probability were calculated for the association between sedation levels and the above parameters. The ability of investigated parameters to distinguish between OAA/S scores was analysed. Bland-Altman analysis was used to compare the agreement between BIS and BISpro. The BIS and BISpro cut-off values for lost response were also determined., Results: Out of 30 patients in total, a high correlation was found between BIS and BISpro, and both correlated well with OAA/S score. Only BIS was able to distinguish all investigated OAA/S states accurately, but the ability to predict OAA/S score 5 to loss of response was comparable between BIS and BISpro. The calculated cut-off values were 68 for BIS and 70 for BISpro., Conclusion: BISpro and BIS are reliable monitors of general anaesthesia during sedation. Trial registration number : Chinese Clinical Trial Registry (URL: www.chictr.org.cn): ChiCTR1900024037 (retrospectively registered).

Variability is high in predicted propofol concentrations during clinical anaesthesia titrated by target-controlled infusion (TCI) to maintain a processed EEG parameter (bispectral index [BIS]) within a specified range. We have shown that the potential for improving the pharmacokinetic model is minimal. The drug titration paradox revealed that titration challenges the classical relationship between drug dose and effect in both individuals and the population. We hypothesised that dynamic factors during surgery beyond the static genetic, epigenetic, and other factors such as age, height, and weight affect the necessary dose. We compared the variability of measured end-tidal sevoflurane concentrations with predicted effect-site propofol concentrations when titrated to a BIS range of 40–60, with the hypothesis that the variability in measured sevoflurane concentrations would not be less than the variability in estimated propofol concentrations. Clinical data from 2280 surgical procedures >1 h in duration were included in the analysis. Anaesthesia with sevoflurane or propofol was based on an institutional protocol. The titration performance for both drugs was assessed by comparing BIS values 30 min after skin incision. The variability of the required concentrations at the same time point was calculated and compared. The achieved 30-min post-incision BIS ranges were not significantly different for sevoflurane or propofol TCI (30 [99% CI: 28–33] and 31 [99% CI: 27–36], respectively). The variability of sevoflurane concentrations was not significantly different from measured predicted propofol concentrations during BIS-guided anaesthesia (normalized concentration range of 0.89 [99% CI: 0.78–0.99] and 0.93 [99% CI 0.87–1.02). Improvements in prediction accuracy of pharmacokinetic models beyond that of those already in clinical use are unlikely to reduce variability in target anaesthetic concentrations across patients in clinical practice. [ABSTRACT FROM AUTHOR]

Background: Postoperative delirium (POD) is the most common postoperative complication in elderly patients, especially in older aged patients (aged 75 years or over). The development of electroencephalography analysis could provide indicators for early detection, intervention, and evaluation. If there are pathophysiological changes in the brain, the BIS value will also change accordingly. In this study, we investigated the predictive value of the preoperative bispectral (BIS) index in POD for patients aged over 75 years. Methods: In this prospective study, patients (≥ 75 years) undergoing elective non-neurosurgery and non-cardiac surgery under general anesthesia were included (n = 308). Informed consent was obtained from all involved patients. Before the operation and during the first 5 postoperative days, delirium was assessed with the confusion assessment method by trained researchers twice every day. Thereafter, the preoperative bedside BIS of each patient was dynamically acquired by the BIS VISTA monitoring system and the BIS monitoring of electrodes. A series of evaluation scales were assessed before and after surgery. A preoperative predictive score was generated according to the results of multivariable logistic regression. The receiver operating characteristic curves were drawn and the area under the curves was estimated to evaluate the perioperative diagnostic values of BIS and preoperative predictive score for POD. The specificity, sensitivity, positive predictive value (PPV), and negative predictive (NPV) value were calculated. Results: Delirium occurred in 50 of 308 (16.2%) patients. The median BIS of delirious patients was 86.7 (interquartile range [IQR] 80.0–94.0), lower than that of the non-delirious 91.9 (IQR 89.7–95.4, P < 0.001). According to the ROC curve of the BIS index, the optimal cut-off value was 84, with a sensitivity of 48%, specificity of 87%, PPV 43%, NPV 89% for forecasting POD and the area under curves was 0.67. While integrating BIS, mini-mental state examination, anemia, activities of daily living, and blood urea nitrogen, the model had a sensitivity of 78%, specificity of 74%, PPV of 0.37%, and NPV of 95% for forecasting POD, and the area under curves was 0.83. Conclusions: Preoperative bedside BIS in delirium patients was lower than that in non-delirium patients when undergoing non-neurosurgery and non-cardiac surgery in patients aged over 75. The model of integrating BIS, mini-mental state examination, anemia, activities of daily living, and blood urea nitrogen is a promising tool for predicting postoperative delirium in patients aged over 75. [ABSTRACT FROM AUTHOR]

'Depth of anaesthesia' monitors claim to measure hypnotic depth during general anaesthesia from the EEG, and clinicians could reasonably expect agreement between monitors if presented with the same EEG signal. We took 52 EEG signals showing intraoperative patterns of diminished anaesthesia, similar to those that occur during emergence (after surgery) and subjected them to analysis by five commercially available monitors. We compared five monitors (BIS, Entropy-SE, Narcotrend, qCON, and Sedline) to see if index values remained within, or moved out of, each monitors' recommended index range for general anaesthesia for at least 2 min during a period of supposed lighter anaesthesia, as observed by changes in the EEG spectrogram obtained in a previous study. Of the 52 cases, 27 (52%) had at least one monitor warning of potentially inadequate hypnosis (index above range) and 16 of the 52 cases (31%) had at least one monitor signifying excessive hypnotic depth (index below clinical range). Of the 52 cases, only 16 (31%) showed concordance between all five monitors. Nineteen cases (36%) had one monitor discordant compared with the remaining four, and 17 cases (33%) had two monitors in disagreement with the remaining three. Many clinical providers still rely on index values and manufacturer's recommended ranges for titration decision making. That two-thirds of cases showed discordant recommendations given identical EEG data, and that one-third signified excessive hypnotic depth where the EEG would suggest a lighter hypnotic state, emphasizes the importance of personalised EEG interpretation as an essential clinical skill. [ABSTRACT FROM AUTHOR]

Background: Renewed interest in regional anaesthesia during the recent COVID-19 pandemic has inspired application of neuraxial anaesthesia for previously unconventional indications, such as awake abdominal surgeries. These patients needed little sedation, since studies demonstrate that neuraxial anaesthesia causes sedation as measured by the bispectral index (BIS). In contrast, no published study has investigated the possible sedative effects of non-neuraxial regional anaesthesia. This pilot randomised controlled trial (RCT) was designed as a template for, and to test the feasibility of, performing a definitive RCT to establish if nonneuraxial regional anaesthesia has any sedative effect. Methods: Forty participants presenting for forearm surgery were randomly allocated to two treatment groups (supraclavicular block and control). Their level of sedation was monitored with BIS prior to surgery for 60 minutes. Specific feasibility outcomes were planned and data were collected according to CONSORT 2010 recommendations. Results: Out of 48 patients screened, 41 (85.42%) were invited to participate. Forty patients (97.56%) consented and 100% of these completed the study. In four participants (10%), BIS electrodes needed replacement, while inadequate contact was shown in three participants (7.50%). Data collection and form completion were deemed "easy" and block success rate was 100%. Differences in mean BIS between groups were < 5 and a difference of 10% between groups in incidence of BIS < 80 (85% block group, 75% control group) was shown. Conclusion: We propose that progression to formal RCT is feasible only with specific modifications to the study design. The decrease in BIS value from baseline should be measured per patient and a clinically significant decrease should be estimated; emergency patients should be excluded; the sample size should be 500 patients; and multiple trial sites should be used. Further consideration should be given to whether such a trial would provide clinically useful information, and would justify the risks, patient discomfort and the considerable financial cost. [ABSTRACT FROM AUTHOR]

During anesthesia induction with propofol the level of arousal progressively decreases until reaching loss of consciousness (LOC). In addition, there is a shift of alpha activity from parieto-occipital to frontal zones, defined as anteriorization. Whilst monitoring LOC and anteriorization would be useful to improve propofol dosage and patient safety, the current devices for anesthetic depth monitoring are unable to detect these events. The aim of this study was to observe LOC and anteriorization during anesthesia induction with propofol by applying electrodes placed in the frontal and parietal areas. Bispectral index (BIS) and quantium consciousness index (qCON) monitors were simultaneously employed. BIS™ and qCON sensors were placed in the frontal and parieto-occipital regions of 10 alopecic patients who underwent anesthesia with propofol, alfentanil, and remifentanil. The initial biophase target of propofol was 2.5 mcg/mL which was gradually increased until reaching LOC. Wilcoxon signed-rank test was used to study differences in alpha power and qCON/BIS indices along the study; and Pk value to evaluate predictive capability of anteriorization of BIS, qCON, and alpha waves. Parietal BIS and qCON values became significantly higher than frontal values 15 min after loss of eye reflex. Anteriorization was observed with both monitors. Pk values for BIS and qCON were strongly predictive of frontal alpha absolute power. During anesthesia induction with propofol it is possible to identify anteriorization with BIS and qCON in the frontal and parieto-occipital regions. Both indices showed different patterns which need to be further studied. [ABSTRACT FROM AUTHOR]

Introduction: The problem of intraoperative awareness concerns about 0.1%-0.2% of patients. The perfect method to evaluate the depth of sleep should be objective, so that the response is quick and precise - to increase or decrease the depth of anaesthesia. More scales originated in order to detect cases of intraoperative awareness. Also, new equipment was built so that anaesthesiologists could properly monitor the depth of anaesthesia. Aim: The aim is to describe methods and devices monitoring the depth of anaesthesia. Material and methods: This work was based on the available literature and the experience of the authors. Results and discussion: Recently a few devices were constructed, all of which can be divided into passive and active systems. Passive systems assess the collected data, while active ones first stimulate and then receive and process data. Passive systems use computer analysis of electroencephalographic signal, and some of them additionally evaluate alterations of frontal electromyogram. According to some, monitors currently available on the market show around 80% effectiveness in preventing intraoperative awareness. Other researchers showed that evidence of their effect on intraoperative awareness is limited. Conclus ions: It seems that when it comes to the effect of anaesthetic agents on such a precise organ as the brain, there is still much to discover. As long as we do not fully know what awareness is and what mechanisms influence the state of staying awake and of anaesthetic sleep, and on which levels it happens, we will not be able to prevent intraoperative awareness effectively. [ABSTRACT FROM AUTHOR]

The depth of anesthesia is commonly assessed in clinical practice by the patient's clinical signs. However, during cardiopulmonary bypass and hypothermia, common symptoms of nociception such as tachycardia, hypertension, sweating, or movement have low sensitivity and specificity in the description of the patient nociception and hypnosis, in particular, detecting nociceptive stimuli. Better monitoring of the depth of analgesia during hypothermia under cardiopulmonary bypass will avoid underdosage or overdosage of analgesia, especially opioids. Induced hypothermia has a multifactorial effect on the level of analgesia and hypnosis. Thermoregulatory processes appear essential for the activation of analgesic mechanisms, ranging from a physiological strong negative affiliation between nerve conduction velocity and temperature, until significant repercussions on the pharmacological dynamics of the analgesic drugs, the latter decreasing the clearance rate with a subsequent increase in the effect-site concentrations. Under the hypothesis that deep hypothermia induces massive effects on the analgesia and hypnosis levels of the patient, we studied whether hypothermia effects were mirrored by several neuromonitoring indices: two hypnosis indices, consciousness index and bispectral index, and a novel nociception index designed to evaluate the analgesic depth. In this clinical trial, 39 patients were monitored during general anesthesia with coronary atherosclerosis cardiopathy who were elective for on-pump coronary artery bypass graft surgery under hypothermia. The changes and correlation between the consciousness index, bispectral index, and nociception index with respect to the temperature were compared in different timepoints at basic state, during cardiopulmonary bypass and after cardiopulmonary bypass. While the three neuromonitoring indices showed significant correlations with respect to the temperature, the nociception index and consciousness index showed the strongest sensitivities, indicating that these two indices could be an important means of intraoperative neuromonitoring during induced hypothermia under cardiopulmonary bypass. [ABSTRACT FROM AUTHOR]

Accurate monitoring of the depth of anesthesia (DoA) is essential for intraoperative and postoperative patient's health. Commercially available electroencephalograph (EEG)-based DoA monitors are recommended only for certain anesthetic drugs and specific age-group patients. This paper presents a machine learning classification processor for accurate DoA estimation irrespective of the patient's age and anesthetic drug. The classification is solely based on six features extracted from EEG signal, i.e., spectral edge frequency (SEF), beta ratio, and four bands of spectral energy (FBSE). A machine learning fine decision tree classifier is adopted to achieve a four-class DoA classification (deep, moderate, and light DoA versus awake state). The feature selection and the classification processor are optimized to achieve the highest classification accuracy for the state of moderate anesthesia required for the surgical operations. The proposed 256-point fast Fourier transform accelerator is implemented to realize SEF, beta ratio, and FBSE that enables minimal latency and high accuracy feature extraction. The proposed DoA processor is implemented using a 65 nm CMOS technology and experimentally verified using field programming gate array (FPGA) based on the EEG recordings of 75 patients undergoing elective surgery with different types of anesthetic agents. The processor achieves an average accuracy of 92.2% for all DoA states, with a latency of 1s The 0.09 mm2 DoA processor consumes 140nJ/classification. [ABSTRACT FROM AUTHOR]

Current trends in modern medicine are concerned with the development of the so-called personalized medicine whose aim is tailoring of treatment to patients. The present research is focused on anaesthesiology, specifically on the study of the level of unconciousness (hypnosis) of patients under general anaesthesia. The idea is to improve the prediction of the patient response during anaesthesia, so that the clinician could adjust the drug dosing using this information. The bispectral index (BIS) is a signal provided by electroencephalogram monitors that is accepted as a depth of hypnosis index. This work shows the BIS modelling of patients undergoing general anaesthesia during surgery. For this, a model that allows to know its value from the electromyogram (EMG) and the propofol infusion rate has been created. The proposal has been achieved by using clustering combined with regression techniques and using a real data set obtained from patients undergoing general anaesthesia. Finally, the created model has been tested also with data from real patients, and the results obtained attested the accuracy of the model. [ABSTRACT FROM AUTHOR]

Summary: This paper proposes a new control strategy for Propofol injection during anesthesia in patients undergoing surgery and where the Bispectral Index (BIS) is considered to be the regulated variable. The proposed control shows the nice feature of being completely independent of the knowledge of the pharmacokinetics that govern the diffusion of the drug. This paper also proposes a certification framework that gives a probabilistic guarantee regarding the containment of the BIS inside the desired interval as well as for the time needed for the BIS to be steered to this interval. Moreover, this certification is given for realistic (and hence very high) level of uncertainties on the parameters that define the unknown‐to‐the‐controller dynamics. This last feature is checked using a widely employed model. [ABSTRACT FROM AUTHOR]

Background Different levels of consciousness are required in order to perform different medical procedures. Sedation scales established to objectively define various levels of sedation in humans have not been thoroughly characterized in non-human species. Postural changes in rats or dogs are useful as gross measures of sedation but are inadequate for quantitative assessment since graded levels of sedation are difficult to delineate and obscured by movement abnormalities. New method A new canine sedation scoring (CSS) method was developed based on the modified observer’s assessment of alertness and sedation score (MOAA/S) used in humans. The method employed a combination of physical, auditory and somatosensory stimuli of increasing intensity. Cardiovascular, respiratory, and a neurophysiological measure of sedation (bispectral index: BIS) data were recorded. Validation studies were performed following intravenous loading and constant rate infusion of propofol or a novel synthetic neuroactive steroid (SGE-746). Results Four levels of consciousness were identified: 1) Awake, 2) Moderate Sedation (MS), 3) Deep Sedation (DS) and 4) General Anesthesia (GA). Cardiorespiratory measurements obtained after bolus administration of propofol and SGE-746 and at the end of each CRI remained within normal limits. Canine sedation scores correlated with BIS for SGE-746. SGE-746 exhibited a more gradual exposure-response relationship than propofol. Larger increases in the plasma concentration from awake values were required to achieve different levels of sedation with SGE-746 compared to propofol. Comparison with existing methods No other canine sedation scoring methods are widely accepted. Conclusion A CSS method, based on the human MOAA/S scale defined four levels of consciousness in dogs and provided better resolution of sedation depth than BIS alone. [ABSTRACT FROM AUTHOR]

Study Objective: To determine the efficacy of 2 different doses (150-300mg) of preoperative pregabalin on propofol and remifentanil doses for total intravenous anesthesia in laparoscopic cholecystectomy.Design: Prospective, randomized, placebo-controlled, double-blinded study.Setting: Training and research hospital.Patients: Forty-eight adult, American Society of Anesthesiologists physical status 1 and 2 patients.Interventions: Patients were randomly assigned to 3 groups to receive orally 1hour before surgery, a placebo group (group 1), pregabalin 150mg (group 2), or pregabalin 300mg (group 3).Measurements: In the operating room, heart rate, systolic and diastolic blood pressures, SpO2, bispectral index, and body temperature were recorded just before anesthesia induction; 1 and 5minutes after induction; and at minutes 10, 15, 20, 25, 30, 35, and 40 of the surgery. Required propofol and remifentanil doses to obtain bispectral index value less than 60 were also recorded.Main Results: The remifentanil doses used in the pregabalin groups at minutes 10, 15, 20, 25, and 30 and propofol doses at minutes 15, 20, 25, and 30 were statistically significantly lower in comparison to the placebo group.Conclusion: The observations provide preliminary evidence that preoperative pregabalin may decrease anesthetic agent requirement in total intravenous anesthesia patients. [ABSTRACT FROM AUTHOR]

Backgrounds and objective: Some studies have shown that deeper anesthesia is more effective on postoperative analgesia and reduces the need for sedative drugs. This study sought to investigate the effect of depth of anesthesia on postoperative pain in laparoscopic cholecystectomy. Materials and methods: In this double-blind clinical trial, 60 patients undergoing laparoscopic cholecystectomy were randomly divided into two groups: low bispectral index (L-BIS=35-44) and high bispectral index (H-BIS=45-55). Anesthesia protocol was the same for both groups (propofol and remifentanil). The pain intensity (at rest and during cough) was evaluated based on the visual analog scale scores in recovery and at 8, 16 and 24 hours after surgery. Results: The mean pain score was significantly lower in patients in the L-BIS group at all examined times at rest and during cough than that in the H-BIS group. The number of patients in need of additional sedative drug in the H-BIS group in recovery was significantly more than that in the L-BIS group (27 vs 18 patients, P=0.007). The incidence of nausea in the recovery room 8 hours after the surgery was significantly less in the L-BIS group than that in the H-BIS group, while at 16 and 24 hours, no case of nausea was reported in the two groups. Conclusion: Given the results of this study, it seems that general anesthesia with propofol and remifentanil with L-BIS causes less need for additional analgesic drug and less nausea and vomiting compared to anesthesia with H-BIS. [ABSTRACT FROM AUTHOR]

This paper presents a new fault detection system in hypnotic sensors used for general anesthesia during surgery. Drug infusion during surgery is based on information received from patient monitoring devices; accordingly, faults in sensor devices can put patient safety at risk. Our research offers a solution to cope with these undesirable scenarios. We focus on the anesthesia process using intravenous propofol as the hypnotic drug and employing a Bispectral Index (BISTM) monitor to estimate the patient's unconsciousness level. The method developed identifies BIS episodes affected by disturbances during surgery with null clinical value. Thus, the clinician--or the automatic controller--will not take those measures into account to calculate the drug dose. Our method compares the measured BIS signal with expected behavior predicted by the propofol dose provider and the electromyogram (EMG) signal. For the prediction of the BIS signal, a model based on a hybrid intelligent system architecture has been created. The model uses clustering combined with regression techniques. To validate its accuracy, a dataset taken during surgeries with general anesthesia was used. The proposed fault detection method for BIS sensor measures has also been verified using data from real cases. The obtained results prove the method's effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a control law designed for the automatic administration of propofol and of remifentanil in order to track a desired level for the bispectral index (BIS), used as a measure of the depth of anesthesia, is analyzed under the presence of model parameters uncertainties. It is theoretically proved and illustrated by simulations that under these circumstances the controller has a very good performance as the BIS converges to a value contained in a neighborhood of the desired BIS level. A retuning strategy in order to improve the BIS tracking under the presence of uncertainties was also theoretically deduced. Simulations show that this strategy leads to BIS tracking improvement. The performance of the controller in clinical environment is illustrated by a clinical case. [ABSTRACT FROM AUTHOR]

Background: Induction of anesthesia is the most crucial period of general anesthesia. Inhalational induction is the most commonly used technique in pediatric anesthesia. Tracheal intubation can be done after reaching the deep levels of anesthesia. The depth of anesthesia is often difficult to be judged. Bispectral index is a measure of the effects of anesthesia on brain. This study was designed to evaluate the efficacy of bispectral index (BIS) in clarifying suitable depth of anesthesia for tracheal intubation during inhalational induction of anesthesia. Methods: In a clinical trial, ninety patients, ASA I & II, 1 to 6 years old, scheduled for elective surgery were enrolled into the study. After starting BIS monitoring, patients randomly were divided into three groups. Then, anesthesia was induced by gradual increase of halothane in 50% mixture of oxygen (O2 ) and N2O and continued until target BIS (60 ± 2, 50 ± 2 and 40 ± 2) achieved. After tracheal intubation, the duration of laryngoscopy and the presence of laryngospasm, bronchospasm, laryngoscopy failure, the movement of extremities and the changes in SpO2 and BIS were recorded. The data were analyzed by chi-square and ANOVA at 0.05 level of significance. Results: BIS could not determine the appropriate level of anesthesia for tracheal intubation in this setting. There were no differences in laryngoscopy duration and the occurrence of laryngospasm, bronchospasm, laryngoscopy failure, extremity movement and awakening time among three groups. Conclusions: These results confirmed that there was no significant difference in the incidence of complications related to intubation at different BIS values (from 60 to 40) during inhalation induction, and probably to achieve an adequate or more reliable depth of anesthesia, the lower values of BIS is required.

This paper presents a new fault detection system in hypnotic sensors used for general anesthesia during surgery. Drug infusion during surgery is based on information received from patient monitoring devices; accordingly, faults in sensor devices can put patient safety at risk. Our research offers a solution to cope with these undesirable scenarios. We focus on the anesthesia process using intravenous propofol as the hypnotic drug and employing a Bispectral Index (BISTM) monitor to estimate the patient’s unconsciousness level. The method developed identifies BIS episodes affected by disturbances during surgery with null clinical value. Thus, the clinician—or the automatic controller—will not take those measures into account to calculate the drug dose. Our method compares the measured BIS signal with expected behavior predicted by the propofol dose provider and the electromyogram (EMG) signal. For the prediction of the BIS signal, a model based on a hybrid intelligent system architecture has been created. The model uses clustering combined with regression techniques. To validate its accuracy, a dataset taken during surgeries with general anesthesia was used. The proposed fault detection method for BIS sensor measures has also been verified using data from real cases. The obtained results prove the method’s effectiveness.

Objective: This study was designed to test the hypothesis that clonidine deepens general anaesthesia as measured by the bispectral index (BIS) and allows the dose of desflurane to be reduced. Design: Randomised, double-blind, placebo controlled study. Setting: Department of Anaesthesia and Intensive Care of Regional and District General Hospital. Materials and methods: Fifty patients undergoing general anaesthesia for elective total hip or total knee replacement were randomly allocated into two groups. The treatment group had 2 μg . kg-1 clonidine administered intravenously 10 minutes before general anaesthesia induction and the control group was given an intravenous placebo. Depth of anaesthesia was guided by BIS with a target level between 40 and 60. The consumption of desflurane during anaesthesia was measured. After stopping desflurane administration at the end of surgery, time to return of consciousness (ROC) was recorded. Unpaired t-test was used for statistical analyses. Results: Twenty five patients with clonidine and 25 with placebo were enrolled. The consumption of desflurane was significantly lower in the clonidine group - 33.1 ± 5.0 g, vs. the placebo group -44.5 ± 10.6 g (p < 0.001). No difference was found in the average time to ROC. This was 6.4 ± 3.8 min in the clonidine group vs. 6.2 ± 3.7 min in the placebo group (p = 0.822). Conclusion: Intravenous clonidine decreases the consumption of desflurane during general anaesthesia. This sparing effect is not associated with increased time to ROC. [ABSTRACT FROM AUTHOR]

The bispectral (BIS) monitor uses brain electroencephalographic data to measure the depth of sedation and pharmacological response during anaesthetic procedures. In this case, the BIS monitor was used for another purpose, to demonstrate postoperatively to the nursing staff that a patient with history of locked-in syndrome (LIS), who underwent pressure ulcer debridement, had periods of wakefulness and apparent sensation, even with his eyes closed. Furthermore, as patients with LIS can feel pain, despite being unable to move, local block or general anaesthesia should be provided for sharp surgical debridement and other painful procedures. This use of the BIS has shown that as a general rule, the staff should treat the patient as though he might be awake and sensate even if he does not open his eyes or move his limbs. The goal of this study was to continuously monitor pain level and communicate these findings to the entire wound team, i.e. anaesthesiologists, surgeons and nurses. [ABSTRACT FROM AUTHOR]

Objective To describe bispectral index (BIS) findings and compare them with cardiovascular and respiratory trends during cardiac arrest and successful CPR in a propofol-anesthetized calf. Case Summary A 3-month-old calf was anesthetized as part of a research project. A thromboxane analog drug ( U46619) was administered IV to induce pulmonary hypertension. Within 10 minutes following U46619 administration, cardiac activity deteriorated, leading to asystole. At this point, BIS and suppression rate were 0 and 100, respectively. Anesthetic drug delivery was discontinued and external chest compressions were initiated. During CPR, end-tidal CO2 concentration decreased and BIS increased, but no spontaneous cardiac activity was noted, thus IV epinephrine was administered. Return of spontaneous circulation was achieved and systemic arterial hypertension developed, while BIS briefly decreased and then increased during the following 2 minutes. The calf's cardiopulmonary variables returned to physiological ranges within 10 minutes after the return of spontaneous circulation and remained stable. Unique Information Provided This is the first report in which BIS is documented together with standard monitoring techniques during cardiopulmonary arrest and resuscitation in a calf. BIS varied with cardiovascular performance, and may be indicative of cerebral blood flow in this context. Further research may be warranted to define the role of BIS for monitoring cerebral activity during CPR. [ABSTRACT FROM AUTHOR]

Abstract: This is the first study to use fNIRS to explore anaesthetic depth and awakening during surgery with general anaesthesia. A 16 channel continuous wave (CW) functional near-infrared system (fNIRS) was used to monitor PFC activity. These outcomes were compared to BIS measures. The results indicate that deoxyHb concentration in the PFC varies during the suppression and emergence of consciousness. During suppression, deoxyHb levels increase, signalling the deactivation of the PFC, while during emergence, deoxyHb concentration drops, initiating PFC activation and the recovery of consciousness. Furthermore, BIS and deoxyHb concentrations in the PFC display a high negative correlation throughout the different anaesthetic phases. These findings suggest that deoxyHb could be a reliable marker for monitoring anaesthetic depth, and that the PFC intervenes in the suppression and emergence of consciousness. [Copyright &y& Elsevier]

Objective: The objective of this study was to compare the feasibility of closed-loop anesthesia delivery with manual control of propofol in pediatric patients during cardiac surgery. Methods: Forty ASA II-III children, undergoing elective cardiac surgery under cardiopulmonary bypass (CPB) in a tertiary care hospital, were randomized to receive propofol either through a closed-loop anesthesia delivery system (CL group) or through traditional manual control (manual group) to achieve a target BIS of 50. Patients were induced and subsequently maintained with a propofol infusion. The propofol usage and the efficacy of closed-loop system in controlling BIS within ±10 of the target were compared with that of manual control. Results: The maintenance of BIS within ±10 of target and intraoperative hemodynamic stability were similar between the two groups. However, induction dose of propofol was less in the CL group (2.06 ± 0.79 mg·kg-1) than the manual group (2.95 ± 1.03 mg·kg-1) (P = 0.006) with less overshoot of BIS during induction in the closed-loop group (P = 0.007). Total propofol used in the off-CPB period was less in the CL group (6.29 ± 2.48 mg·kg-1 h-1 vs 7.82 ± 2.1 mg·kg-1 IT1) (P = 0.037). Phenylephrine use in the pre-CPB period was more in the manual group (16.92 ± 10.92 μg·kg-1 vs 5.79 ± 5.98 μg·kg-1) (P = 0.014). Manual group required a median of 18 (range 8-29) dose adjustments per hour, while the CL group required none. Conclusion: This study demonstrated the feasibility of closed-loop controlled propofol anesthesia in children, even in challenging procedures such as cardiac surgery. Closed-loop system needs further and larger evaluation to establish its safety and efficacy. [ABSTRACT FROM AUTHOR]

Background: Familiarity with different methods and medications in anesthesia and producing sufficient depth of anesthesia are very important in anesthesia practice. Due to the central analgesic and sedative effect of lidocaine in the presence of the sufficient blood level, it can be used for general anesthesia. This study was carried out to compare the effect of halothane with lidocaine infusion on BIS during maintenance of anesthesia. Materials and Methods: In this randomized double-blind controlled clinical trial, 66 patients scheduled for elective inguinal herniorrahaphy were randomized into two equal groups. For maintenance, one group received halothane (1%) with O2-N2O and another group received lidocaine infusion (100 &mug/kg/min). BIS was checked every 5 minutes for half an hour. Statistical analysis of data was done by Chi-square and T-test through SPSS software. P-values less than 0.05 were considered meaningful. Results: Mean of BIS was 65.72 in the lidocaine group and 56.7 in the halothane group during the first 30 minutes. There was a significant statistical difference between the two groups (p<0.05). Conclusion: Mean of BIS in lidocaine group was higher than that in the halothane group. If this indicates the presence of a light level of anesthesia, increasing the dose of hypnotics and opioids leads to an increase in the depth of anesthesia. However, since there is not any device for monitoring the effect of opioids on the central nervous system and the level of anesthesia, simultaneous monitoring of BIS and hemodynamic parameters seems to be a more reasonable idea. [ABSTRACT FROM AUTHOR]

Background Although telemedicine is one of the key initiatives of the World Health Organization, no study has explored the feasibility and efficacy of teleanaesthesia. This bi-centre pilot study investigates the feasibility of transcontinental anaesthesia. Methods Twenty patients aged ≥18 yr undergoing elective thyroid surgery for ≥30 min were enrolled in this study. The remote and local set-up was composed of a master-computer (Montreal) and a slave-computer (Pisa). Standard Internet connection, remote desktop control, and video conference software were used. All patients received total i.v. anaesthesia controlled remotely (Montreal). The main outcomes were feasibility, clinical performance, and controller performance of transcontinental anaesthesia. The clinical performance of hypnosis control was the efficacy to maintain bispectral index (BIS) at 45: ‘excellent’, ‘good’, ‘poor’, and ‘inadequate’ control represented BIS values within 10, from 11 to 20, from 21 to 30, or >30% from target. The clinical performance of analgesia was the efficacy to maintain Analgoscore values at 0 (−9 to 9); −3 to +3 representing ‘excellent’ pain control, −3 to −6 and +3 to +6 representing ‘good’ pain control, and −6 to −9 and +6 to +9 representing ‘insufficient’ pain control. The controller performance was evaluated using Varvel parameters. Results Transcontinental anaesthesia was successful in all 20 consecutive patients. The clinical performance of hypnosis showed an ‘excellent and good’ control for 69% of maintenance time, and the controller performance showed an average global performance index of 57. The clinical performance of analgesia was ‘excellent and good’ for 92% of maintenance time, and the controller performance showed a global performance index of 1118. Conclusions Transcontinental anaesthesia is feasible; control of anaesthesia shows good performance indexes. Clinical registration number NCT01331096. [ABSTRACT FROM PUBLISHER]

Introduction: The objective of this study was to determine the effects of isoproterenol infusion on level of consciousness during ablation using total intravenous anesthesia. Methods and results: Seven patients undergoing total intravenous anesthesia for atrial fibrillation ablation were monitored for level of consciousness using bispectral EEG levels (BIS). Isoproterenol infusion was performed after the ablation during anesthesia. BIS levels prior to, during, and post-isoproterenol infusion were recorded and correlated to isoproterenol infusion doses. In all patients, BIS levels significantly increased during isoproterenol infusion (median BIS prior to infusion, 46; during infusion, 64 ( p < 0.02)). With a subsequent increase in anesthetic medication, BIS levels could again be reduced. Conclusion: Isoproterenol infusion alters consciousness level during total intravenous anesthesia for atrial fibrillation ablation. BIS monitoring is a novel way to modulate anesthesia during ablation to potentially optimize patient comfort and ablation success. [ABSTRACT FROM AUTHOR]

Objective: Propofol is an intravenous agent used extensively in total venous anesthesia (TIVA),but its acquisition cost is nearly 1 to 3 folds higher than other intravenous or inhalation agents. Thiopental is an ultra short acting barbiturate which can reduce the cost of induction to one seventh of Propofol induction cost. In this study, by BIS monitoring of the depth of anesthesia, we evaluated maintaining anesthesia with Propofol while Thiopental has been used for induction of anesthesia and the aim of study was to find a cost effective method. Methodology: In a single blind clinical trial, 82 patients with ASA II & I scheduled for cataract surgery were randomized in two groups. In the first group (A), induction of anesthesia was done with Propofol 2 mg/kg and then anesthesia maintained with Propofol 100 micro/kg. In the other group (B), induction was Thiopental 5 mg/kg and anesthesia maintained with Propofol 160 micro/ kg. BIS monitored depth of anesthesia throughout the procedure. We compared the BIS values in each step of the procedure in both groups. Results: After extubation, mean of BIS score were 87.53(±2.52) and 88.79(±2.07) for groups A and B respectively. This difference was not clinically significant. Multiple linear regression analysis, identified decreased maintenance dose of Propofol and duration of surgery as independent predictors for BIS span 40-60.(P<0.000,r2 =0.558). Cost effectiveness (acquisition cost/percent of 40-60 BIS span) for groups A and B were 2.95 &dollar; and 1.03 &dollar; respectively. Conclusion: Minor surgeries like ophthalmic surgery can be conducted with maintenance of Propofol while induction is with Thiopental. Monitoring the depth of anesthesia with BIS showed that if we choose 160 micro/kg Propofol for maintenance then it is not necessary to have a loading dose and induction can be done by Thiopental. Further studies with different type ofsurgery and different maintenance doses of Propofol must be done. [ABSTRACT FROM AUTHOR]

BACKGROUND: Induction of anesthesia is the most crucial period of general anesthesia. Inhalational induction is the most commonly used technique in pediatric anesthesia. Tracheal intubation can be done after reaching the deep levels of anesthesia. The depth of anesthesia is often difficult to be judged. Bispectral index is a measure of the effects of anesthesia on brain. This study was designed to evaluate the efficacy of bispectral index (BIS) in clarifying suitable depth of anesthesia for tracheal intubation during inhalational induction of anesthesia. METHODS: In a clinical trial, ninety patients, ASA I & II, 1 to 6 years old, scheduled for elective surgery were enrolled into the study. After starting BIS monitoring, patients randomly were divided into three groups. Then, anesthesia was induced by gradual increase of halothane in 50% mixture of oxygen (O2) and N2O and continued until target BIS (60 ± 2, 50 ± 2 and 40 ± 2) achieved. After tracheal intubation, the duration of laryngoscopy and the presence of laryngospasm, bronchospasm, laryngoscopy failure, the movement of extremities and the changes in SpO2 and BIS were recorded. The data were analyzed by chi-square and ANOVA at 0.05 level of significance. RESULTS: BIS could not determine the appropriate level of anesthesia for tracheal intubation in this setting. There were no differences in laryngoscopy duration and the occurrence of laryngospasm, bronchospasm, laryngoscopy failure, extremity movement and awakening time among three groups. CONCLUSIONS: These results confirmed that there was no significant difference in the incidence of complications related to intubation at different BIS values (from 60 to 40) during inhalation induction, and probably to achieve an adequate or more reliable depth of anesthesia, the lower values of BIS is required. [ABSTRACT FROM AUTHOR]

Abstract: This article describes the main methods used to monitor the effects of muscle relaxants, and the ways in which they may be employed clinically to assess the effects of neuromuscular blockade and anticholinesterase drugs. It provides an overview of the main patterns of electrical stimulation used to assess residual muscle paralysis, including train-of-four and double burst stimulation. The article describes the techniques used to monitor depth of anaesthesia, and compares the advantages and disadvantages inherent in the methods currently in use. Methods based on processed electroencephalogram (EEG) signals are discussed, and include auditory evoked potentials (AEPs), bispectral index (BIS) and entropy. [Copyright &y& Elsevier]

Aim: In this study, we aimed to compare the effects of desflurane- N2O and desflurane-fentanyl combinations on hemodynamics, recovery times, volatile anesthetic consumption and costs in low-flow desflurane anesthesia by bispectral index (BIS) monitoring of depth of anesthesia. Methods: After approval of ethics committee and obtaining patient consents, 60 patients were divided into two equal groups randomly. Non-invasive blood pressure measurement, ECG, SpO2 and BIS were monitored. All patients received 10 L .min-1 100% oxygen with mask for 5 minute before intubation. 2 mg.kg-1 propofol, 2 μg.kg-1 fentanyl and 0.6 mg.kg-1 rocuronium bromide were administered at induction in both groups. Desfluran 6% was chosen for anesthesia maintenance. Group 1 received 50% O2-N2O mixture in 6 L.min-1 and Group 2 received 50% O2-air mixture in 6 L.min-1 as carrier gas. Low-flow anesthesia (1 L.min-1) was started after a 10-min period of initial high flow (6 L.min-1). In Group 2, infusion of fentanyl was begun in 1 μg.kg.hour-1 rate. Desflurane level was adjusted at a main BIS value of 40-60. Blood pressure, heart rate, FiO2, etO2, FiN22, EtN2O, FiCO2, EtCO2, Fidesfluran and Etdesflurane were recorded. Results: There were no significant differences between the two groups in terms of heart rate, arterial blood pressure, settings of desfluran and recovery time. BIS values (p<0.001) and anesthetic agent costs (p<0.001) were higher in Group 2. Conclusion: Using fentanyl infusion instead of nitrous oxide in low flow-anesthesia with desflurane did not alter the hemodynamic parameters. Fentanyl infusion with medical air-oxygen as carrier gas is an alternative technique, but increases BIS values and anesthetic agent costs. [ABSTRACT FROM AUTHOR]

Objective: The study''s aim was to compare response entropy (RE) and state entropy (SE) with bispectral index (BIS) electroencephalography (EEG) as an alternative cerebral monitoring tool in patients scheduled for coronary artery bypass graft surgery. Design: Prospective, observational single-center study. Setting: University hospital. Participants: Thirty patients undergoing coronary artery bypass graft surgery receiving remifentanil-propofol anesthesia. Interventions: Surgery was performed with cardiopulmonary bypass (CPB) and cardiac arrest in 15 patients, with CPB without cardiac arrest in 9 patients and without CPB in 6 patients. Measurements and Main Results: RE, SE, BIS, burst suppression ratio (BSR), and frontal electromyography (f-EMG) were detected simultaneously. RE and SE compared favorably with BIS and their correlations were strong (r 2 = 0.6, r 2 = 0.55, respectively). The mean bias of RE and BIS was −1.8, but limits of agreement were high (+20.5/−24.1). RE and SE tended to be lower than the BIS values in the CPB subgroups. The detection of BSR was similar with RE and SE and the BIS. A strong correlation existed between BIS and f-EMG (r 2 = 0.62) in contrast to RE (r 2 = 0.45) and SE (r 2 =0.39). BIS monitoring was significantly more disturbed than RE and SE with 9.1% ±10.9% and 0.1% ± 0.2% of the total anesthesia time, respectively. Neither implicit nor explicit memory was shown. Conclusion: RE and SE are comparable with the BIS but showed significantly less interference from f-EMG and superior resistance against artifacts. Thus, spectral entropy is more suitable than the BIS during propofol-remifentanil anesthesia in cardiac surgery patients. [Copyright &y& Elsevier]

Abstract: Background and objective: Perioperative low-dose ketamine has been useful for postoperative analgesia. In this study we wanted to assess the analgesic effect and possible side-effects of perioperative low-dose S (+) ketamine when added to a regime of non-opioid multimodal pain prophylaxis. Methods: Seventy-seven patients scheduled for haemorrhoidectomy were enrolled in this randomized, double-blind, controlled study. They received oral paracetamol 1–2g, total intravenous anaesthesia, intravenous 8mg dexamethasone, 30mg ketorolac and local infiltration with bupivacaine/epinephrine. Patients randomized to S (+) ketamine received an intravenous bolus dose of 0.35mgkg−1 S (+) ketamine before start of surgery followed by continuous infusion of 5μgkg−1 min−1 until 2min after end of surgery. Patients in the placebo group got isotonic saline (bolus and infusion). BIS™ monitoring was used. Pain intensity and side-effects were assessed by blinded nursing staff during PACU stay and by phone 1, 7 and 90 days after surgery. Results: In patients randomized to S (+) ketamine emergence from anaesthesia was significantly longer (13.1min vs. 9.3min; p <0.001). BIS values were significantly higher during anaesthesia (maximal value during surgery: 62 vs. 57; p =0.01) and when opening eyes (81 vs. 70, p <0.001). Pain scores (NRS and VAS) did not differ significantly between groups. Conclusions: The addition of perioperative S (+) ketamine for postoperative analgesia after haemorrhoidectomy on top of multimodal non-opioid pain prophylaxis does not seem to be warranted, due to delayed emergence and recovery, more side-effects, altered BIS readings and absence of additive analgesic effect. [Copyright &y& Elsevier]

The article presents a case study on the anesthesia management of a 35-year-old female patient presented for dilation and curettage (D&C) and left ankle arthroscopy in fibula. She has a medical history of gastric reflux and has underwent a general surgery and did not complain of intraoperative awareness. The patient was given premedication with midazolam, and anesthesia was maintained with sevoflurane and a continuous propofol infusion.

It has been reported some patients have opened eyes with low bispectral index (BIS) values immediately following electroconvulsive therapy (ECT). We investigated the time course of the recovery from amnesia and BIS values. Five patients with depression requiring repeated ECT procedures were enrolled. The patients were asked to recall an object presented prior to anesthesia at four specific points (prior to induction, upon regaining consciousness following ECT, when they returned to their ward, and when their BIS values had returned to pre-anesthetic levels). BIS data were recorded continuously until BIS values returned to the pre-anesthetic levels at their ward. The area under a receiver-operating characteristic (ROC) curve was used to detect associations between the BIS values and disturbance of memory function. A total of 41 ECT stimuli were administered. After returning to their ward, patients generally fell asleep, with BIS values of between 50 and 70, and they woke up 1–2 h later. All the patients could recall the presented object prior to anesthesia and when the BIS values had returned to pre-anesthetic levels. The area under the ROC curve for the detection of memory disturbance was 0.902. The present study demonstrated a high frequency of patients falling asleep and the frequent occurrence of prolonged periods of low BIS values following ECT. The results of memory testing showed that ECT procedures resulted in amnesia. The ROC curve findings suggest a strong association of memory disturbance with BIS values. In conclusion, patients generally fell asleep, with low BIS values, for 1–2 h after ECT, and a prolonged period of impairment of memory formation was associated with low BIS values. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The anhepatic phase of orthotopic liver transplantation (OLT) is associated with significant changes in pharmacokinetics. The aim of this study was to compare the influence of this phase on propofol target concentrations during BIS guided target controlled infusion (TCI). Study design: Prospective study. Patients and methods: Eight patients aged 25 to 65 years, Child-Pugh status A-B scheduled for OLT were prospectively included. Anesthesia was performed using TCI of propofol (Diprifusor®, Marsh pharmacokinetic model), sufentanil and cisatracurium. Propofol target concentration was adjusted to maintain BIS values between 40 and 50. Results: To maintain stable BIS values, propofol target concentrations should be decreased during the anhepatic phase versus the dissection one (2.0μg/ml±0.8 versus 3.0μg/ml±0.9, p <0.0001). Conclusion: BIS could be useful to titrate propofol infusion during the anhepatic phase of OLT. [Copyright &y& Elsevier]

The present study provides results in an early sleep period for non-REM stage correlation with bispectral index (BIS) values. The purpose of the study was to assess the applicability of an objective procedure to monitor sleep. Nine healthy subjects (mean age: 25.0 ± 4.4; 1 female) were recruited for the study without history of any neurological, psychiatric, or sleep-related disorders. Electroencephalography (EEG) signals from 30 electrodes referenced to linked earlobe electrodes, and electrooculography (EOG) and electromyography (EMG) activities were recorded. BIS recording was performed simultaneously with EEG recording. Because that the current study is related to non-REM sleep, corresponding to the first sleep cycle, approximately 90 min of data was processed both for BIS and EEG data pools. The sleep staging was done using traditional Rechtschaffen and Kales scoring (R&K) and BIS scores were acquired online. The BIS values corresponded well to sleep depth, decreasing in accordance with sleep stages. Overall BIS correlation with sleep scores in the non-REM was found to be r = 0.86 (Spearman analysis, n = 9, r2 = 0.75). Accompanying the traditional scoring, BIS and BIS-like tools can be useful for information processing and for psychophysiological applications in neurology, psychiatry, and further studies on consciousness. [ABSTRACT FROM AUTHOR]

Background: In earlier studies, between 1% and 57% of patients have been reported to dream during anaesthesia. Thus, dreaming is much more common than definite memories of real events. We wanted to examine whether dreaming during anaesthesia is related to insufficient hypnotic action, as indicated by BIS levels and, thus, may constitute a risk for awareness. Methods: After IRB approval, 2653 consecutive surgical patients were included. BIS registrations were recorded continuously during the anaesthetic procedure. The patients were interviewed on three occasions after anaesthesia. Standard questions, according to Brice, to evaluate awareness and dreaming during anaesthesia were asked. The dreams were categorized as either pleasant/neutral or unpleasant without any further evaluation of the dream content. Episodes with a mean BIS below 40, above 60 and above 70 were identified and subdivided according to duration (1, 2, 4 and 6 min, respectively). The total time as well as number and duration of episodes for the three BIS-levels were used to analyze any relation to reported dreaming. The mean BIS was also analyzed. Results: Dreaming during anaesthesia was reported by 211 of patients (8.0%) on at least one of the post-operative interviews. BIS data did not show any significant correlation with dreaming, and neither did any of the tested case-specific parameters (gender, age, ASA group, BMI, use of relaxants, induction agent, maintenance agent, length of procedure, omitting N2O and concomitant regional anaesthesia). Conclusion: Dreaming during anaesthesia seems to be a separate phenomenon, not in general related to insufficient anaesthesia as indicated by high BIS levels. [ABSTRACT FROM AUTHOR]

Background: Bispectral index (BIS) has been associated with benefits from less-deep anesthesia as well as preventing awareness, albeit not at the same time. We investigated how increasing experience from BIS in clinical practice affect the hypnotic level, drug consumption, as well as subjective opinions on this monitoring. Methods: Eight certified registered nurse anesthetists (CRNAs) with previous experience from 88 (46–121) BIS monitored cases anesthetized 80 cases with concealed BIS, followed by 80 cases with available BIS. Additional education and training was followed by yet another 160 patients randomized to open or blindly recorded BIS. BIS levels, anesthetic gas consumption, fentanyl use, and subjective opinions on utility and reliability were investigated. Results: After gaining initial experience from BIS monitoring, the fraction of time with BIS levels of 40–60 did not deteriorate in cases with concealed monitoring and no further improvement was found in subsequent cases with available data from the BIS monitoring, not even after additional training and encouragement to adhere to the 40–60 interval. Compared with the first experience from BIS monitoring the subjective opinions on utility had increased from 33 to 78 mm (100 mm visual analog scales) ( P<0.0001). Conclusion: Although BIS became considerably appreciated, growing experience and repeated education had no impact on drug dosing and BIS levels. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Comparison between BIS (Bispectral Index) and state (SE) and response (RE) entropy during laparotomy for inflammatory bowel disease patients (IBD) and evaluation of the variations of RE and SE during nociceptive stimulation. Study design: Prospective, observational study. Patients and methods: Fourteen IBD''s patients undergoing laparotomy were included. Anaesthesia aimed to maintain BIS between 40 and 60 by isoflurane and nitrous oxide. Analgesia was performed by sufentanil bolus administrated according to an increase of 20% of systolic blood pressure (SBP) and heart rate compared with the baseline values. BIS, RE and SE were measured at each nociceptive stimulation. A variance analysis (Anova) was used to assess BIS, RE and SE variations throughout surgery (p <0.05 as significant). Relationship between BIS, RE and SE was assessed by Pearson correlation (p <0.01 as significant). The ability for SE and RE to predict depth of anaesthesia and intraoperative analgesia was performed by calculating aera under the receiver operated curves (AUC). Results: BIS and entropy parameters had strictly the same evolution during anaesthesia. SBP increased significantly during nociceptive stimulation while no variation of RE was observed. A significant correlation was shown between BIS, RE and SE. The evaluation of anaesthesia depth was good for RE (AUC: 0.932±0.26) and SE (AUC: 0.926±0.27). There was however no difference between RE and SE to predict analgesic requirement. Conclusion: Because RE includes muscular frequency analysis, it does not allow analgesic requirement evaluation in paralyzed patients. [Copyright &y& Elsevier]