Detection method of intraoperative awareness: a randomized comparative study.

BACKGROUND: : The incidence of intraoperative awareness varies in a wide range in the literature. The reasons for these different results include the questioning method used and the questioning time. The goal of this study is to compare the effectiveness of different questioning methods and times used in intraoperative awareness research for detecting the incidence. METHODS: We recruited patients between the ages of 18-70 years, with normal cognitive functions and able to speak after general anesthesia to the study. The patients were randomly divided into two groups. In Group 1 we applied the modified Brice questionnaire in the first 2 h and 24 h after surgery for investigating intraoperative awareness. In Group 2, 24 h after surgery, we asked about anesthesia satisfaction and patients' complaints, if any. RESULTS: There was no statistically significant difference between the groups in terms of age (p = 0.514).The proportion of women was significantly higher (p = 0.002), the duration of anesthesia was shorter, and the rate of narcotic analgesic use was higher in Group 2 (p < 0.001). The assessment in the first 2 h showed the frequency of awareness was statistically higher in Group 1 than in Group 2 (p = 0.016). In the postoperative 24-h assessment, we found no significant difference in the incidence of intraoperative awareness between the groups (p < 0.05). In Group 1, there was no statistically significant difference in terms of incidence of awareness according to evaluation time (p = 250). DISCUSSION: The incidence of intraoperative awareness in Group 1 was significantly higher than in Group 2 in the evaluation conducted in the first 2 h. There was no significant difference in the determination of intraoperative awareness between questioning times in group 1.

Raw and processed electroencephalography in modern anesthesia practice: a brief primer on select clinical applications.

The evidence supporting the intraoperative use of processed electroencephalography (pEEG) monitoring to guide anesthetic delivery is growing rapidly. This article reviews the key features of electroencephalography (EEG) waveforms and their clinical implications in select patient populations and anesthetic techniques. The first patient topic reviewed is the vulnerable brain. This term has emerged as a description of patients who may exhibit increased sensitivity to anesthetics and/or may develop adverse neurocognitive effects following anesthesia. pEEG monitoring of patients who are known to have or are suspected of having vulnerable brains, with focused attention on the suppression ratio, alpha band power, and pEEG indices, may prove useful. Second, pEEG monitoring along with vigilant attention to anesthetic delivery may minimize the risk of intraoperative awareness when administering a total intravenous anesthesia in combination with a neuromuscular blockade. Third, we suggest that processed EEG monitoring may play a role in anesthetic and resuscitative management when adverse changes in blood pressure occur. Fourth, pEEG monitoring can be used to better identify anesthesia requirements and guide anesthetic titration in patients with known or suspected substance use.

Frontal electroencephalogram reveals emergence-like brain activity occurring during transition periods in cardiac surgery.

BACKGROUND: Cardiac surgery has one of the highest incidences of intraoperative awareness. The periods of initiation and discontinuation of cardiopulmonary bypass could be high-risk periods. Certain frontal EEG patterns might plausibly occur with unintended intraoperative awareness. This study sought to quantify the incidence of these pre-specified patterns during cardiac surgery. METHODS: Two-channel bihemispheric frontal EEG was recorded in 1072 patients undergoing cardiac surgery as part of a prospective observational study. Spectrograms were created, and mean theta (4-7 Hz) power and peak alpha (7-17 Hz) frequency were measured in patients under general anaesthesia with isoflurane. Emergence-like EEG activity in the spectrogram during surgery was classified as an alpha peak frequency increase by 2 Hz or more, and a theta power decrease by 5 dB or more in comparison with the median pre-bypass values. RESULTS: Data from 1002 patients were available for analysis. Fifty-five of those patients (5.5%) showed emergence-like EEG activity at least once during surgery with a median duration of 13.2 min. These patients were younger (median age, 59 vs 67 yr; P<0.001) and the median end-tidal isoflurane concentration before cardiopulmonary bypass was higher (0.82 vs 0.75 minimum alveolar concentration [MAC]; P=0.013). There was no significant difference between those with or without emergence-like EEG activity in sex, lowest core temperature, or duration of surgery. Forty-six of these EEG changes (84%) occurred within a 1 h time window centred on separation from cardiopulmonary bypass. CONCLUSION: The findings of this study suggest that approximately one in 20 patients undergoing cardiac surgery with a volatile anaesthetic agent have a sustained EEG pattern while surgery is ongoing that is often seen with emergence from general anaesthesia. Monitoring the frontal EEG during cardiopulmonary bypass may identify these events and potentially reduce the incidence of unintended awareness. CLINICAL TRIAL REGISTRATION: NCT02976584.

Comparison of electroencephalogram between propofol- and thiopental-induced anesthesia for awareness risk in pregnant women.

There have been few comparative studies using electroencephalogram (EEG) spectral characteristics during the induction of general anesthesia for cesarean section. This retrospective study investigated the differences in the depth of anesthesia through EEG analysis between propofol- and thiopental-induced anesthesia. We reviewed data of 42 patients undergoing cesarean section who received either thiopental (5 mg/kg) or propofol (2 mg/kg). EEG data were extracted from the bispectral index (BIS) monitor, and 10-second segments were selected from the following sections: 1) Stage I, BIS below 60 after induction; 2) Stage II, after intubation completion; 3) Stage III, end-tidal sevoflurane above 0 vol%. The risk of awareness was represented by the BIS and entropy measures. In Stage III, the thiopental group (n = 20) showed significantly higher BIS value than the propofol group (n = 22) (67.9 [18.66] vs 44.5 [20.63], respectively, p = 0.002). The thiopental group had decreased slow-delta oscillations and increased beta-oscillations as compared to the propofol group in Stages II and III (p < 0.05). BIS, spectral entropy, and Renyi permutation entropy were also higher in the thiopental group at Stages II and III (p < 0.05). In conclusion, frontal spectral EEG analysis demonstrated that propofol induction maintained a deeper anesthesia than thiopental in pregnant women.

Retrospective analysis of cases of intraoperative awareness in a large multi-hospital health system reported in the early postoperative period.

BACKGROUND: Awareness with recall under general anesthesia remains a rare but important issue that warrants further study. METHODS: We present a series of seven cases of awareness that were identified from provider-reported adverse event data from the electronic anesthesia records of 647,000 general anesthetics. RESULTS: The low number of identified cases suggests an under-reporting bias. Themes that emerge from this small series can serve as important reminders to anesthesia providers to ensure delivery of an adequate anesthetic for each patient. Commonalities between a majority of our identified anesthetic awareness cases include: obesity, use of total intravenous anesthesia, use of neuromuscular blockade, and either a lack of processed electroencephalogram (EEG) monitoring or documented high depth of consciousness index values. An interesting phenomenon was observed in one case, where adequately-dosed anesthesia was delivered without technical issue, processed EEG monitoring was employed, and the index value suggested an adequate depth of consciousness throughout the case. CONCLUSIONS: Provider-reported adverse event data in the immediate post-operative period are likely insensitive for detecting cases of intraoperative awareness. Though causation cannot firmly be established from our data, themes identified in this series of cases of awareness with recall under general anesthesia provide important reminders for anesthesia providers to maintain vigilance in monitoring depth and dose of anesthesia, particularly with total intravenous anesthesia.

Protocol for direct reporting of awareness in maternity patients (DREAMY): a prospective, multicentre cohort study of accidental awareness during general anaesthesia.

BACKGROUND: Accidental awareness during general anaesthesia (AAGA) is a complex and rare outcome to investigate in surgical patient populations, particularly obstetric patients. We report the protocol of the Direct Reporting of Awareness in Maternity patients (DREAMY) study, illustrating how the research was designed to address practical and methodological challenges for investigating AAGA in an obstetric cohort. METHODS: This is the trial protocol of a prospective, multicentre cohort study of patients undergoing obstetric surgery under general anaesthesia. Accidental awareness during general anaesthesia will be detected using three repetitions of standardised direct questioning over 30 days, with responses indicating memories during general anaesthesia verified using structured interviews. Reports will be adjudicated, then classified, in accordance with pre-defined and pre-validated structures, including the Michigan Awareness Classification tool. Quantitative data will be collected on general anaesthesia conduct for all participants. This descriptive study is being conducted in England and aims to recruit a minimum of 2015 patients. RESULTS: The DREAMY study was prospectively registered (ClinicalTrials.gov Identifier: NCT03100396) and ethical approval granted. Participant recruitment began in May 2017 and one year follow up concluded in August 2019. Publication of the results is anticipated in 2020. CONCLUSIONS: The DREAMY study will provide data on incidence, experience and implications of AAGA for obstetric patients, using a robust methodology that will reliably detect and translate subjective AAGA reports into objective outcomes. In addition, the study is expected to improve vigilance for AAGA in participating hospitals and encourage adoption of recommendations for support of patients experiencing AAGA.

Accidental awareness while under general anaesthesia.

Accidental awareness during general anaesthesia may cause many intraoperative discomforts and bring further moderate to severe long-term symptoms including flashbacks, nightmares, hyperarousal or post-traumatic stress disorder. The incidence of awareness varied from 0.017% to 4% among studies. The relatively reliable incidence of intraoperative awareness with postoperative recall is 0.02%. The reason causing awareness was unclear. Insufficient anaesthetic dosing was thought as the principal cause. Even awareness was not comprehensively understood, some endeavors have been raised to prevent or reduce it, including i) Reducing the insufficient anaesthetic dosing induced by negligence; ii) Providing close clinical observation and clinical parameters from the monitor such as bispectral index or electroencephalogram, as well as isolated forearm technique and passive brain-computer interface may bring some effects sometimes. Because current studies still have some flaws, further trials with new detecting approach, superior methodology and underlying aetiology are needed to unfasten the possible factors causing awareness.

MOTANA: study protocol to investigate motor cerebral activity during a propofol sedation.

BACKGROUND: Accidental Accidental awareness during general anesthesia (AAGA) occurs in 1-2% of high-risk practice patients and is a cause of severe psychological trauma, termed post-traumatic stress disorder (PTSD). However, no monitoring techniques can accurately predict or detect AAGA. Since the first reflex for a patient during AAGA is to move, a passive brain-computer interface (BCI) based on the detection of an intention of movement would be conceivable to alert the anesthetist. However, the way in which propofol (i.e., an anesthetic commonly used for the general anesthesia induction) affects motor brain activity within the electroencephalographic (EEG) signal has been poorly investigated and is not clearly understood. For this reason, a detailed study of the motor activity behavior with a step-wise increasing dose of propofol is required and would provide a proof of concept for such an innovative BCI. The main goal of this study is to highlight the occurrence of movement attempt patterns, mainly changes in oscillations called event-related desynchronization (ERD) and event-related synchronization (ERS), in the EEG signal over the motor cortex, in healthy subjects, without and under propofol sedation, during four different motor tasks. METHODS: MOTANA is an interventional, prospective, exploratory, physiological, monocentric, and randomized study conducted in healthy volunteers under light anesthesia, involving EEG measurements before and after target-controlled infusion of propofol at three different effect-site concentrations (0 µg.ml -1, 0.5 µg.ml -1, and 1.0 µg.ml -1). In this exploratory study, 30 healthy volunteers will perform 50 trials for the four motor tasks (real movement, motor imagery, motor imagery with median nerve stimulation, and median nerve stimulation alone) in a randomized sequence. In each conditions and for each trial, we will observe changes in terms of ERD and ERS according to the three propofol concentrations. Pre- and post-injection comparisons of propofol will be performed by paired series tests. DISCUSSION: MOTANA is an exploratory study aimed at designing an innovative BCI based on EEG-motor brain activity that would detect an attempt to move by a patient under anesthesia. This would be of interest in the prevention of AAGA. TRIAL REGISTRATION: Agence Nationale de Sécurité du Médicament (EUDRACT 2017-004198-1), NCT03362775. Registered on 29 August 2018. https://clinicaltrials.gov/ct2/show/NCT03362775?term=03362775&rank=1.

¿Contamos actualmente con un método fiable para detectar el momento de pérdida de consciencia durante la inducción de la anestesia? / Do we have today a reliable method to detect the moment of loss of consciousness during induction of general anaesthesia?

Esta revisión pretende ofrecer una visión general del estado de conocimiento actual sobre la monitorización de la profundidad anestésica y la detección del momento de pérdida de consciencia, desde los primeros signos clínicos implicados en la anestesia hasta las últimas tecnologías utilizadas en esta área. Tales técnicas son extremadamente importantes para el desarrollo de sistemas automáticos de control de la anestesia y para prevenir episodios de percepción intraoperatoria y sobredosis. Realizamos investigaciones en bases de datos (Pubmed, IEEE Xplore) utilizando términos como control anestésico, profundidad de la anestesia, pérdida de consciencia, BIS y cada uno de los índices existentes. A pesar de los diversos métodos capaces de controlar el estado hipnótico de la anestesia, aún no existe una metodología que detecte con precisión el momento de la pérdida de consciencia durante la inducción de la anestesia general

This review aims to give an overview of the current state of monitoring depth of anaesthesia and detecting the moment of loss of consciousness, from the first clinical signs involved in anaesthesia to the latest technologies used in this area. Such techniques are extremely important for the development of automatic systems for anaesthesia control, including preventing intraoperative awareness episodes and overdoses. A search in the databases Pubmed and IEEE Xplore was performed using terms such anaesthetic monitoring, depth of anaesthesia, loss of consciousness, as well as anaesthesia indexes, namely BIS. Despite the several methods capable of monitoring the hypnotic state of anaesthesia, there is still no methodology to accurate detect the moment of loss of consciousness during induction of general anaesthesia

BIS Monitoring on Intraoperative Awareness: A Meta-analysis.

Intraoperative awareness is a very serious complication of general anesthesia. Several studies have evaluated the potential association between bispectral index (BIS) and intraoperative awareness, however, the results obtained were controversial. Therefore, we performed a meta-analysis to further assess the association between the BIS monitoring and the incidence of intraoperative awareness. A comprehensive search was conducted to identify all eligible studies from the online literature databases published prior to Feb. 2017. A total of five studies with 17 432 cases and 16 749 controls were included. An odds ratio (OR) and a 95% confidence interval (CI) were calculated to examine the strength of the association. The results showed that in the overall analysis, the association between the BIS monitoring and the incidence of intraoperative awareness was not significant (OR=0.58, 95% CI= 0.22-1.58, P=0.29). A stratified analysis by comparing different anesthesia methods revealed that BIS monitoring group showed a lower incidence of intraoperative awareness in patients with intravenous anesthesia when compared with non-BIS monitoring group (OR=0.20, 95% CI=0.08-0.49, P=0.0004), whereas there was no statistically significant difference in the incidence of intraoperative awareness between BIS and non-BIS monitoring groups in patients with inhalation anesthesia (OR=1.13, 95% CI=0.56-2.26, P=0.73). In conclusion, our meta-analysis showed that BIS monitoring had no appreciable advantage in the reduction of the intraoperative awareness incidence in inhalation anesthesia, while showed a remarkable superiority in intravenous anesthesia.

Effect of magnesium sulfate on anesthesia depth, awareness incidence, and postoperative pain scores in obstetric patients. A double-blind randomized controlled trial.

OBJECTIVES: To assess the effects of magnesium on the depth of anesthesia and to determine the effects of magnesium on incidence of awareness and postoperative pain after caesarean section.  Methods: The study was designed as a double-blind, controlled, randomized study and conducted in Hacettepe University Hospital, Ankara, Turkey  between January 2015 and March 2016. A total of 100 pregnant healthy women who were between 17 and 41 years old, ASA II, and scheduled for an elective cesarean section with general anesthesia were included in the study. After induction, sevoflurane was used for maintenance in Group S and desflurane in Group D (control groups). At Group S-M and Group D-M (study groups), magnesium infusion was started with sevoflurane and desflurane anesthesia respectively. Minimum alveolar concentration of sevoflurane and desflurane were kept constant. Bispectral index scores (BIS), fentanyl consumption and postoperative visual analogue scale (VAS) values were recorded. All of the patients had been followed-up for awareness until the postoperative first year. Results: Demographic variables of the patients were similar. BIS values were significantly higher in control groups throughout the operation (p less than 0.001). No significant difference was detected for intraoperative fentanyl consumption and awareness incidence. VAS values were significantly lower in study groups (p less than 0.05). Conclusion: Magnesium infusion provided significantly lower intraoperative BIS values and lower postoperative VAS scores. We believe that magnesium can be useful as an adjuvant to general anesthesia.

Isolated forearm technique: a meta-analysis of connected consciousness during different general anaesthesia regimens.

BACKGROUND: General anaesthesia should prevent patients from experiencing surgery, defined as connected consciousness. The isolated forearm technique (IFT) is the current gold standard for connected consciousness monitoring. We evaluated the efficacy of different anaesthesia regimens in preventing IFT responses. METHODS: We conducted a systematic review with meta-analysis of studies evaluating IFT in adults. Proportions of IFT-positive patients were compared for inhalational versus intravenous anaesthesia and anaesthesia brain monitor (ABM)-guided versus non-ABM-guided. RESULTS: Of 1131 patients in 22 studies, 393 (34.8%) had an IFT response during induction or maintenance. IFT-positive patients were less frequent during induction (19.7% [95% CI, 17.5-22.1]) than during maintenance (31.2% [95% CI, 27.8-34.8]). Proportions of IFT-positive patients during induction and maintenance were similar for inhalational (0.51 [95% CI, 0.38-0.65]) and intravenous (0.52 [95% CI, 0.26-0.77]) anaesthesia, but during maintenance were lower with inhalational (0.18 [95% CI, 0.08-0.38]) than with intravenous (0.48 [95% CI, 0.24-0.73]) anaesthesia. Proportions of IFT-positive patients during induction and maintenance were not significantly different for ABM-guided (0.64 [95% CI, 0.39-0.83]) and non-ABM-guided (0.48 [95% CI, 0.34-0.62]) anaesthesia but during maintenance were lower with non-ABM-guided (0.19 [95% CI, 0.09-0.37]) than with ABM-guided (0.57 [95% CI, 0.34-0.77]). Proportions of IFT-positive patients decreased significantly with increasing age and premedication use. Of the 34 anaesthesia regimens, 16 were inadequate. Studies had low methodological quality (only seven randomised controlled trials) and significant heterogeneity. CONCLUSIONS: Standard general anaesthesia regimens might not prevent connected consciousness. More accurate anaesthesia brain monitor methodology to reduce the likelihood of connected consciousness is desirable.

Calculations of consciousness: electroencephalography analyses to determine anesthetic depth.

PURPOSE OF REVIEW: Electroencephalography (EEG) was introduced into anesthesia practice in the 1990s as a tool to titrate anesthetic depth. However, limitations in current analysis techniques have called into question whether these techniques improve standard of care, or instead call for improved, more ubiquitously applicable measures to assess anesthetic transitions and depth. This review highlights emerging analytical approaches and techniques from neuroscience research that have the potential to better capture anesthetic transitions to provide better measurements of anesthetic depth. RECENT FINDINGS: Since the introduction of electroencephalography, neuroscientists, engineers, mathematicians, and clinicians have all been developing new ways of analyzing continuous electrical signals. Collaborations between these fields have proliferated several analytical techniques that demonstrate how anesthetics affect brain dynamics and conscious transitions. Here, we review techniques in the following categories: network science, integration and information, nonlinear dynamics, and artificial intelligence. SUMMARY: Up-and-coming techniques have the potential to better clinically define and characterize altered consciousness time points. Such new techniques used alongside traditional measures have the potential to improve depth of anesthesia measurements and enhance an understanding of how the brain is affected by anesthetic agents. However, new measures will be needed to be tested for robustness in real-world environments and on diverse experimental protocols.

Non-instrumental clinical monitoring does not guarantee an adequate course of general anesthesia. A prospective clinical study.

BACKGROUND: Clinical monitoring is the most common method of adjusting the appropriate level of general anesthesia. However, episodes of intraoperative awareness (AWR) are still reported, suggesting that clinical observations may not be sufficient in some cases. The objective of this study was to compare the efficacy of clinical and instrumental neuromonitoring with auditory evoked potentials (AEP) in an intraoperative analysis of the proper level of general anesthesia. METHODS: Patients scheduled for elective surgery were randomly divided into two groups. Subjects in the first group underwent intravenous, in the second group volatile anesthesia. The adequacy of anesthesia was analyzed using clinical parameters. All the participants were instrumentally monitored with the autoregressive AEP index (AAI). After the anesthesia, patients filled out a questionnaire on possible AWR. RESULTS: Data of 208 patients (87 in the first, and 121 in the second group) were analyzed. Before surgery there were no changes in AAI values between groups (80 vs. 78, P=0.5192). The mean values of clinical parameters changed, but five minutes after the nociceptive stimuli. The mean values of AAI at analyzed time points were specific for general anesthesia. In patients under intravenous anesthesia, we found more episodes of too low (46/608 vs.15/847, P<0.000) anesthesia. One case of AWR was found in the TIVA group. CONCLUSIONS: AAI index is good indicator of patients' level of consciousness during general anesthesia. Standard clinical monitoring provides appropriate level of the procedure. However, it is insufficient during TIVA and does not prevent episodes of AWR.

Total intravenous anesthesia produces outcomes superior to those with combined intravenous-inhalation anesthesia for laparoscopic gynecological surgery at high altitude.

Objective We compared efficacy and adverse outcomes following totally intravenous anesthesia (TIVA) versus combined intravenous-inhalation anesthesia (CIVIA) on hemodynamics and postoperative recovery following laparoscopic gynecological (LG) surgery at high altitudes. Methods We enrolled 80 ASA I or II patients scheduled for LG surgery and randomly assigned them to TIVA with propofol (group P, n = 40) or CIVIA with isoflurane (group I, n = 40). Mean arterial pressure, heart rate, pulse oxygen saturation, and partial pressure of end-tidal carbon dioxide were measured at various time points. Outcome measures were interval to spontaneous ventilation, eye opening, return to consciousness, extubation, operating room duration. Intraoperative awareness and postoperative nausea/vomiting were assessed at follow-up. Results No differences in hemodynamic parameters were detected in either group. Group P had a significantly shorter postoperative anesthetic recovery time and lower incidence of postoperative nausea/vomiting. Conclusion TIVA is superior to CIVIA for GL surgery at high altitudes.