Intraoperative awareness: controversies and non-controversies

Depth of anesthesia monitoring: an argument for its use for patient safety

PURPOSE OF REVIEW

There have been significant advancements in depth of anesthesia (DoA) technology. The Anesthesia Patient Safety Foundation recently published recommendations to use a DoA monitor in specific patient populations receiving general anesthesia. However, the universal use of DoA monitoring is not yet accepted. This review explores the current state of DoA monitors and their potential impact on patient safety.

RECENT FINDINGS

We reviewed the current evidence for using a DoA monitor and its potential role in preventing awareness and preserving brain health by decreasing the incidence of postoperative delirium and postoperative cognitive dysfunction or decline (POCD). We also explored the evidence for use of DoA monitors in improving postoperative clinical indicators such as organ dysfunction, mortality and length of stay. We discuss the use of DoA monitoring in the pediatric population, as well as highlight the current limitations of DoA monitoring and the path forward.

SUMMARY

There is evidence that DoA monitoring may decrease the incidence of awareness, postoperative delirium, POCD and improve several postoperative outcomes. In children, DoA monitoring may decrease the incidence of awareness and emergence delirium, but long-term effects are unknown. While there are key limitations to DoA monitoring technology, we argue that DoA monitoring shows great promise in improving patient safety in most, if not all anesthetic populations.

[Talking to Unconscious? - Therapeutic Communication During General Anaesthesia, Resuscitation and Therapy of Coma]

There are numerous reports from patients concerning perceptions during deep unconsciousness, be it general anaesthesia, cardiopulmonary resuscitation or intensive care and coma treatment. These experiences can cause considerable traumatisation. The most stressful experience is apparently not feeling pain, but the lack of communication, i.e. being recognised and being able to express oneself. Although there are already indications of positive effects of positive communication during general anaesthesia, these findings have not yet markedly changed the way we deal with the unconscious.

Multiple algorithms highlight key brain genes driven by multiple anesthetics

Anesthesia serves as a pivotal tool in modern medicine, creating a transient state of sensory deprivation to ensure a pain-free surgical or medical intervention. While proficient in alleviating pain, anesthesia significantly modulates brain dynamics, metabolic processes, and neural signaling, thereby impairing typical cognitive functions. Furthermore, anesthesia can induce notable impacts such as memory impairment, decreased cognitive function, and diminished intelligence, emphasizing the imperative need to explore the concealed repercussions of anesthesia on individuals. In this investigation, we aggregated gene expression profiles (GSE64617, GSE141242, GSE161322, GSE175894, and GSE178995) from public repositories following second-generation sequencing analysis of various anesthetics. Through scrutinizing post-anesthesia brain tissue gene expression utilizing Gene Set Enrichment Analysis (GSEA), Robust Rank Aggregation (RRA), and Weighted Gene Co-expression Network Analysis (WGCNA), this research aims to pinpoint pivotal genes, pathways, and regulatory networks linked to anesthesia. This undertaking not only enhances comprehension of the physiological changes brought about by anesthesia but also lays the groundwork for future investigations, cultivating new insights and innovative perspectives in medical practice.

Touchless short-wave infrared imaging for dynamic rapid pupillometry and gaze estimation in closed eyes

BACKGROUND

Assessments of gaze direction (eye movements), pupil size, and the pupillary light reflex (PLR) are critical for neurological examination and neuroscience research and constitute a powerful tool in diverse clinical settings ranging from critical care through endocrinology and drug addiction to cardiology and psychiatry. However, current bedside pupillometry is typically intermittent, qualitative, manual, and limited to open-eye cases, restricting its use in sleep medicine, anesthesia, and intensive care.

METHODS

We combined short-wave infrared (SWIR, ~0.9-1.7μm) imaging with image processing algorithms to perform rapid (~30 ms) pupillometry and eye tracking behind closed eyelids. Forty-three healthy volunteers participated in two experiments with PLR evoked by visible light stimuli or directing eye movements towards screen targets. Imaging was performed simultaneously on one eye closed, and the other open eye serving as ground truth. Data analysis was performed with a custom approach quantifying changes in brightness around the pupil area or with a deep learning U-NET-based procedure.

RESULTS

Here we show that analysis of SWIR imaging data can successfully measure stimulus-evoked PLR in closed-eye conditions, revealing PLR events in single trials and significant PLRs in nearly all individual subjects, as well as estimating gaze direction. The neural net-based analysis could successfully use closed-eye SWIR data to recreate estimates of open-eye images and assess pupil size.

CONCLUSIONS

Continuous touchless monitoring of rapid dynamics in pupil size and gaze direction through closed eyes paves the way for developing devices with wide-ranging applications, fulfilling long-standing goals in clinical and research fields.

Touching the unconscious in the unconscious - hypnotic communication with unconscious patients

If hypnosis means contact to the unconscious to modulate psychological and physiological functions by means of suggestions, and if this is facilitated by attenuation of the critical mind, then the question arises as to whether suggestions also have an effect when waking consciousness is otherwise eliminated, namely by coma or anesthesia. A prerequisite would be perception, which actually is evidenced by reports of patients after traumatic brain injury, artificial coma, resuscitation or general anesthesia. Moreover, posttraumatic stress disorder (PTSD) frequently observed after these medical situations is hardly explainable without some sort of awareness under such conditions. Even advanced neurophysiological diagnostic cannot yet rule out consciousness or sensory processing. Especially reference to perception during unconsciousness is given by the results of a recent multicenter study on the effects of hypnotic communication with patients under controlled adequate deep general anesthesia. The observed reductions in incidence and severity of postoperative pain, opioid use, nausea and vomiting cannot be explained by the reaction of a few but only by a considerable proportion of patients. This leads to a strong plea for a more careful treatment of unconscious patients in the emergency room, operating theater or intensive care unit, for the abandonment of the restriction of therapeutic communication to awake patients, and for new aspects of communication and hypnosis research. Obviously, loss of consciousness does not protect against psychological injury, and continuation of communication is needed. But how and what to talk to unconscious patients? Generally addressing the unconscious mind with suggestions that generally exert their effects unconsciously, hypnotic communication appears to be the adequate language. Especially addressing meaningful topics, as derived from the basic psychological needs and known stressors, appears essential. With respect to negative effects by negative or missing communication or to the proposed protective and supporting effects of therapeutic communication with patients clinically rated as unconscious, the role of consciousness is secondary. For the effects of perceived signals and suggestions it does not matter whether consciousness is absent, or partial, or unrecognized present.

Anesthesia and the neurobiology of consciousness

In the 19th century, the discovery of general anesthesia revolutionized medical care. In the 21st century, anesthetics have become indispensable tools to study consciousness. Here, I review key aspects of the relationship between anesthesia and the neurobiology of consciousness, including interfaces of sleep and anesthetic mechanisms, anesthesia and primary sensory processing, the effects of anesthetics on large-scale functional brain networks, and mechanisms of arousal from anesthesia. I discuss the implications of the data derived from the anesthetized state for the science of consciousness and then conclude with outstanding questions, reflections, and future directions.

The feasibility of dexmedetomidine-led anesthesia maintenance strategy during major abdominal surgery

Background

Dexmedetomidine is known for its selective action on α2-adrenoceptor sites and is recognized for its neuroprotective capabilities. It can improve postoperative cognitive function. Commonly used anesthetics, such as sevoflurane and propofol, have been reported to affect postoperative cognitive function. Therefore, it could be valuable to explore dexmedetomidine-led anesthesia strategy. This study was designed to assess the performance, safety, and effective infusion rate in anesthesia maintenance, to explore a feasible dexmedetomidine-led anesthesia maintenance protocol, and to provide a foundation for potential combined anesthesia.

Methods

Thirty patients aged 18-60 years, classified as ASA I or II, undergoing abdominal surgery were involved. The anesthesia maintenance was achieved with dexmedetomidine, remifentanil and rocuronium. Dixon up-and-down sequential methodology was utilized to ascertain the ED50 of dexmedetomidine for maintaining Patient State Index (PSI) 25-40 (depth of stage III anesthesia). Intraoperative HR, BP and depth of anesthesia were monitored and controlled. The wake-up time from anesthesia, the incidence of intraoperative awareness and postoperative delirium, and the patients' satisfaction were assessed.

Results

The results indicated that dexmedetomidine-led anesthesia could maintain the depth of stage III anesthesia during abdominal surgery. The ED50 and ED95 of dexmedetomidine infusion rates during anesthesia maintenance were 2.298 μg/kg·h (95%CI: 2.190-2.404 μg/kg·h) and 3.765 μg/kg·h (95%CI: 3.550-4.050 μg/kg·h). Continuous infusion of dexmedetomidine and 0.1-0.3 μg/kg·min remifentanil could maintain PSI 25-40, and provide appropriate anesthesia depth for abdominal surgery. Perioperative bradycardia and hypertension could be rapidly corrected with atropine and nitroglycerin. The median wake-up time after anesthesia was 4.8 min, the perioperative maximum HR had significant correlation with wake-up time and intraoperative dexmedetomidine dose. No intraoperative awareness and postoperative delirium occurred; the patients were satisfied with dexmedetomidine-led anesthesia.

Conclusions

dexmedetomidine-led strategy could maintain stable depth of anesthesia throughout surgery, and the ED50 of dexmedetomidine infusion rates was 2.298 μg/kg·h. Intraoperative HR, BP and depth of anesthesia require monitoring, the bradycardia and hypertension could be rapidly corrected.

Consciousness and General Anesthesia: Challenges for Measuring the Depth of Anesthesia

The optimal consciousness level required for general anesthesia with surgery is unclear, but in existing practice, anesthetic oblivion, may be incomplete. This article discusses the concept of consciousness, how it is altered by anesthetics, the challenges for assessing consciousness, currently used technologies for assessing anesthesia levels, and future research directions. Wakefulness is marked by a subjective experience of existence (consciousness), perception of input from the body or the environment (connectedness), the ability for volitional responsiveness, and a sense of continuity in time. Anesthetic drugs may selectively impair some of these components without complete extinction of the subjective experience of existence. In agreement with Sanders et al. (2012), the authors propose that a state of disconnected consciousness is the optimal level of anesthesia, as it likely avoids both awareness and the possible dangers of oversedation. However, at present, there are no reliably tested indices that can discriminate between connected consciousness, disconnected consciousness, and complete unconsciousness.

Awareness with paralysis and symptoms of post-traumatic stress disorder among mechanically ventilated emergency department survivors (ED-AWARENESS-2 Trial): study protocol for a pragmatic, multicenter, stepped wedge cluster randomized trial

BACKGROUND

Awareness with paralysis (AWP) is memory recall during neuromuscular blockade (NMB) and can cause significant psychological harm. Decades of effort and rigorous trials have been conducted to prevent AWP in the operating room, where prevalence is 0.1-0.2%. By contrast, AWP in mechanically ventilated emergency department (ED) patients is common, with estimated prevalence of 3.3-7.4% among survivors given NMB. Longer-acting NMB use is a critical risk for AWP, and we have shown an association between ED rocuronium use and increased AWP prevalence. As NMB are given to more than 90% of ED patients during tracheal intubation, this trial provides a platform to test an intervention aimed at reducing AWP. The overall objective is to test the hypothesis that limiting ED rocuronium exposure will significantly reduce the proportion of patients experiencing AWP.

METHODS

This is a pragmatic, stepped wedge cluster randomized trial conducted in five academic EDs, and will enroll 3090 patients. Per the design, all sites begin in a control phase, under observational conditions. At 6-month intervals, sites sequentially enter a 2-month transition phase, during which we will implement the multifaceted intervention, which will rely on use of nudges and defaults to change clinician decisions regarding ED NMB use. During the intervention phase, succinylcholine will be the default NMB over rocuronium. The primary outcome is AWP, assessed with the modified Brice questionnaire, adjudicated by three independent, blinded experts. The secondary outcome is the proportion of patients developing clinically significant symptoms of post-traumatic stress disorder at 30 and 180 days after hospital discharge. We will also assess for symptoms of depression and anxiety, and health-related quality of life. A generalized linear model, adjusted for time and cluster interactions, will be used to compare AWP in control versus intervention phases, analyzed by intention-to-treat.

DISCUSSION

The ED-AWARENESS-2 Trial will be the first ED-based trial aimed at preventing AWP, a critical threat to patient safety. Results could shape clinical use of NMB in the ED and prevent more than 10,000 annual cases of AWP related to ED care.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT05534243 . Registered 06, September 2022.

Description of the Content and Quality of Publicly Available Information on the Internet About Inhaled Volatile Anesthesia and Total Intravenous Anesthesia: Descriptive Study

BACKGROUND

More than 300 million patients undergo surgical procedures requiring anesthesia worldwide annually. There are 2 standard-of-care general anesthesia administration options: inhaled volatile anesthesia (INVA) and total intravenous anesthesia (TIVA). There is limited evidence comparing these methods and their impact on patient experiences and outcomes. Patients often seek this information from sources such as the internet. However, the majority of websites on anesthesia-related topics are not comprehensive, updated, and fully accurate. The quality and availability of web-based patient information about INVA and TIVA have not been sufficiently examined.

OBJECTIVE

This study aimed to (1) assess information on the internet about INVA and TIVA for availability, readability, accuracy, and quality and (2) identify high-quality websites that can be recommended to patients to assist in their anesthesia information-seeking and decision-making.

METHODS

Web-based searches were conducted using Google from April 2022 to November 2022. Websites were coded using a coding instrument developed based on the International Patient Decision Aids Standards criteria and adapted to be appropriate for assessing websites describing INVA and TIVA. Readability was calculated with the Flesch-Kincaid (F-K) grade level and the simple measure of Gobbledygook (SMOG) readability formula.

RESULTS

A total of 67 websites containing 201 individual web pages were included for coding and analysis. Most of the websites provided a basic definition of general anesthesia (unconsciousness, n=57, 85%; analgesia, n=47, 70%). Around half of the websites described common side effects of general anesthesia, while fewer described the rare but serious adverse events, such as intraoperative awareness (n=31, 46%), allergic reactions or anaphylaxis (n=29, 43%), and malignant hyperthermia (n=18, 27%). Of the 67 websites, the median F-K grade level was 11.3 (IQR 9.5-12.8) and the median SMOG score was 13.5 (IQR 12.2-14.4), both far above the American Medical Association (AMA) recommended reading level of sixth grade. A total of 51 (76%) websites distinguished INVA versus TIVA as general anesthesia options. A total of 12 of the 51 (24%) websites explicitly stated that there is a decision to be considered about receiving INVA versus TIVA for general anesthesia. Only 10 (20%) websites made any direct comparisons between INVA and TIVA, discussing their positive and negative features. A total of 12 (24%) websites addressed the concept of shared decision-making in planning anesthesia care, but none specifically asked patients to think about which features of INVA and TIVA matter the most to them.

CONCLUSIONS

While the majority of websites described INVA and TIVA, few provided comparisons. There is a need for high-quality patient education and decision support about the choice of INVA versus TIVA to provide accurate and more comprehensive information in a format conducive to patient understanding.

Pro-Con Debate: Electroencephalography-Guided Anesthesia for Reducing Postoperative Delirium

Postoperative delirium (POD) has significant implications on morbidity, mortality, and health care expenditures. Monitoring electroencephalography (EEG) to adjust anesthetic management has gained interest as a strategy to mitigate POD. In this Pro-Con commentary article, the pro side supports the use of EEG to reduce POD, citing an empiric reduction in POD with processed EEG (pEEG)-guided general anesthesia found in several studies and recent meta-analysis. The Electroencephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes (ENGAGES) trial is the exception to this, and issues with methods and achieved depths are discussed. Meanwhile, the Con side advocates that the use of EEG to reduce POD is not yet certain, citing that there is a lack of evidence that associations between anesthetic depth and POD represent causal relationships. The Con side also contends that the ideal EEG signatures to guide anesthetic titration are currently unknown, and the potential benefits of reduced anesthesia levels may be outweighed by the risks of potentially insufficient anesthetic administration. As the public health burden of POD increases, anesthesia clinicians will be tasked to consider interventions to mitigate risk such as EEG. This Pro-Con debate will provide 2 perspectives on the evidence and rationales for using EEG to mitigate POD.

Initial loading of dexmedetomidine and continuous propofol sedation for prevention of delayed recovery: A randomized controlled trial

BACKGROUND

Sedation with continuous dexmedetomidine and bolus midazolam administration provides a lower incidence of unacceptable patient movement during procedures but requires a longer recovery time. The authors aimed to compare recovery time and unacceptable patient movement during sedation with initial loading of dexmedetomidine followed by continuous propofol infusion with those during sedation with continuous dexmedetomidine and bolus midazolam administration.

METHODS

In this prospective randomized controlled trial, 54 patients undergoing dental surgery and requiring intravenous sedation were assigned to either the dexmedetomidine and propofol group (n = 27, dexmedetomidine administered at 6 μg/kg/h for 5 minutes, followed by continuous propofol infusion using a target-controlled infusion) or the dexmedetomidine and midazolam group (n = 27, dexmedetomidine administered at 0.2-0.7 μg/kg/h continuously after the same initial loading dose with bolus midazolam). A bispectral index of 70 through 80 was maintained during the procedure. Patient movement that interfered with the procedure and time from the end of sedation to achieving a negative Romberg sign were assessed.

RESULTS

Times from the end of sedation to achieving a negative Romberg sign in the dexmedetomidine and propofol group (median, 14 minutes [interquartile range, 12-15 minutes]) were significantly shorter (P < .001) than in the dexmedetomidine and midazolam group (median, 22 minutes [interquartile range, 17.5-30.5 minutes]). The incidence of unacceptable patient movement was comparable between groups (n = 3 in the dexmedetomidine and propofol group, n = 4 in the dexmedetomidine and midazolam group; P = .999).

CONCLUSIONS

Sedation with a single loading dose of dexmedetomidine followed by continuous propofol infusion can prevent delayed recovery without increasing unacceptable patient movement.

PRACTICAL IMPLICATIONS

The combination of dexmedetomidine and propofol may provide high-quality sedation for ambulatory dental practice. This clinical trial was registered in the University Hospital Medical Information Network Clinical Trials Registry. The registration number is UMIN000039668.

Impact of female sex on anaesthetic awareness, depth, and emergence: a systematic review and meta-analysis

BACKGROUND

Suggested anaesthetic dose ranges do not differ by sex, likely because of limited studies comparing sexes. Our objective was to systematically synthesise studies with outcomes of unintended anaesthesia awareness under anaesthesia, intraoperative connected consciousness, time to emergence from anaesthesia, and dosing to achieve adequate depth of anaesthesia, and to compare between females and males.

METHODS

Studies were identified from MEDLINE, Embase, and the Cochrane library databases until August 2, 2022. Controlled clinical trials (randomised/non-randomised) and prospective cohort studies that reported outcomes by sex were included. Results were synthesised by random effects meta-analysis where possible, or narrative form.

RESULTS

Of the 19 749 studies identified, 64 (98 243 participants; 53 143 females and 45 100 males) were eligible for inclusion, and 44 citations contributed to meta-analysis. Females had a higher incidence of awareness with postoperative recall (33 studies, odds ratio 1.38, 95% confidence interval [CI] 1.09-1.75) and connected consciousness during anaesthesia (three studies, OR 2.09, 95% CI 1.04-4.23) than males. Time to emergence was faster in females, including time to eye-opening (10 studies, mean difference -2.28 min, 95% CI -3.58 to -0.98), and time to response to command (six studies, mean difference -2.84 min, 95% CI -4.07 to -1.62). Data on depth of anaesthesia were heterogenous, limiting synthesis to a qualitative review which did not identify sex differences.

CONCLUSIONS

Female sex was associated with a greater incidence of awareness under general anaesthesia, and faster emergence from anaesthesia. These data suggest reappraisal of anaesthetic care, including whether similar drug dosing for females and males represents best care.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022336087.

A Real-Time Neurophysiologic Stress Test for the Aging Brain: Novel Perioperative and ICU Applications of EEG in Older Surgical Patients

As of 2022, individuals age 65 and older represent approximately 10% of the global population [1], and older adults make up more than one third of anesthesia and surgical cases in developed countries [2, 3]. With approximately > 234 million major surgical procedures performed annually worldwide [4], this suggests that > 70 million surgeries are performed on older adults across the globe each year. The most common postoperative complications seen in these older surgical patients are perioperative neurocognitive disorders including postoperative delirium, which are associated with an increased risk for mortality [5], greater economic burden [6, 7], and greater risk for developing long-term cognitive decline [8] such as Alzheimer's disease and/or related dementias (ADRD). Thus, anesthesia, surgery, and postoperative hospitalization have been viewed as a biological "stress test" for the aging brain, in which postoperative delirium indicates a failed stress test and consequent risk for later cognitive decline (see Fig. 3). Further, it has been hypothesized that interventions that prevent postoperative delirium might reduce the risk of long-term cognitive decline. Recent advances suggest that rather than waiting for the development of postoperative delirium to indicate whether a patient "passed" or "failed" this stress test, the status of the brain can be monitored in real-time via electroencephalography (EEG) in the perioperative period. Beyond the traditional intraoperative use of EEG monitoring for anesthetic titration, perioperative EEG may be a viable tool for identifying waveforms indicative of reduced brain integrity and potential risk for postoperative delirium and long-term cognitive decline. In principle, research incorporating routine perioperative EEG monitoring may provide insight into neuronal patterns of dysfunction associated with risk of postoperative delirium, long-term cognitive decline, or even specific types of aging-related neurodegenerative disease pathology. This research would accelerate our understanding of which waveforms or neuronal patterns necessitate diagnostic workup and intervention in the perioperative period, which could potentially reduce postoperative delirium and/or dementia risk. Thus, here we present recommendations for the use of perioperative EEG as a "predictor" of delirium and perioperative cognitive decline in older surgical patients.

A Narrative Review Illustrating the Clinical Utility of Electroencephalogram-Guided Anesthesia Care in Children

The major therapeutic end points of general anesthesia include hypnosis, amnesia, and immobility. There is a complex relationship between general anesthesia, responsiveness, hemodynamic stability, and reaction to noxious stimuli. This complexity is compounded in pediatric anesthesia, where clinicians manage children from a wide range of ages, developmental stages, and body sizes, with their concomitant differences in physiology and pharmacology. This renders anesthetic requirements difficult to predict based solely on a child's age, body weight, and vital signs. Electroencephalogram (EEG) monitoring provides a window into children's brain states and may be useful in guiding clinical anesthesia management. However, many clinicians are unfamiliar with EEG monitoring in children. Young children's EEGs differ substantially from those of older children and adults, and there is a lack of evidence-based guidance on how and when to use the EEG for anesthesia care in children. This narrative review begins by summarizing what is known about EEG monitoring in pediatric anesthesia care. A key knowledge gap in the literature relates to a lack of practical information illustrating the utility of the EEG in clinical management. To address this gap, this narrative review illustrates how the EEG spectrogram can be used to visualize, in real time, brain responses to anesthetic drugs in relation to hemodynamic stability, surgical stimulation, and other interventions such as cardiopulmonary bypass. This review discusses anesthetic management principles in a variety of clinical scenarios, including infants, children with altered conscious levels, children with atypical neurodevelopment, children with hemodynamic instability, children undergoing total intravenous anesthesia, and those undergoing cardiopulmonary bypass. Each scenario is accompanied by practical illustrations of how the EEG can be visualized to help titrate anesthetic dosage to avoid undersedation or oversedation when patients experience hypotension or other physiological challenges, when surgical stimulation increases, and when a child's anesthetic requirements are otherwise less predictable. Overall, this review illustrates how well-established clinical management principles in children can be significantly complemented by the addition of EEG monitoring, thus enabling personalized anesthesia care to enhance patient safety and experience.

[Accidental Awareness during General Anaesthesia]

Accidental awareness during general anaesthesia (AAGA) is a rare but severe complication. The reported incidence of AAGA may depend on the assessment of intraoperative awareness with explicit recall and there are substantial variations between subspecialties and groups of patients. The majority of prospective studies using structured interviews reported an incidence of AAGA at 0.1-0.2% during general anaesthesia, however, higher values were observed in paediatric (0.2-1.2%) and obstetric patients (0.47%). Risk factors that predispose to AAGA are patient conditions, ASA status, female gender, patient age, history of AAGA, surgical procedure, anaesthetic drug type, muscle relaxation, dosages of hypnotic or analgesic drugs, monitoring and malfunction of anaesthesia systems. Preventive strategies include careful assessment of risk factors, avoidance of underdosages of hypnotics and analgetics during general anaesthesia and monitoring of depth of anaesthesia in risk patients. The health-related consequences can be serious and psychopharmacological and psychotherapeutic interventions are indicated in patients who have experienced AAGA.

Responsiveness variability during anaesthesia relates to inherent differences in brain structure and function of the frontoparietal networks

Anaesthesia combined with functional neuroimaging provides a powerful approach for understanding the brain mechanisms of consciousness. Although propofol is used ubiquitously in clinical interventions that reversibly suppress consciousness, it shows large inter-individual variability, and the brain bases of this variability remain poorly understood. We asked whether three networks key to conscious cognition-the dorsal attention (DAN), executive control (ECN), and default mode (DMN)-underlie responsiveness variability under anaesthesia. Healthy participants (N = 17) were moderately anaesthetized during narrative understanding and resting-state conditions inside the Magnetic Resonance Imaging scanner. A target detection task measured behavioural responsiveness. An independent behavioural study (N = 25) qualified the attention demands of narrative understanding. Then, 30% of participants were unaffected in their response times, thus thwarting a key aim of anaesthesia-the suppression of behavioural responsiveness. Individuals with stronger functional connectivity within the DAN and ECN, between them, and to the DMN, and with larger grey matter volume in frontal regions were more resilient to anaesthesia. For the first time, we show that responsiveness variability during propofol anaesthesia relates to inherent differences in brain structure and function of the frontoparietal networks, which can be predicted prior to sedation. Results highlight novel markers for improving awareness monitoring during clinical anaesthesia.

Detection of Motor Cerebral Activity After Median Nerve Stimulation During General Anesthesia (STIM-MOTANA): Protocol for a Prospective Interventional Study

BACKGROUND

Accidental awareness during general anesthesia (AAGA) is defined as an unexpected awareness of the patient during general anesthesia. This phenomenon occurs in 1%-2% of high-risk practice patients and can cause physical suffering and psychological after-effects, called posttraumatic stress disorder. In fact, no monitoring techniques are satisfactory enough to effectively prevent AAGA; therefore, new alternatives are needed. Because the first reflex for a patient during an AAGA is to move, but cannot do so because of the neuromuscular blockers, we believe that it is possible to design a brain-computer interface (BCI) based on the detection of movement intention to warn the anesthetist. To do this, we propose to describe and detect the changes in terms of motor cortex oscillations during general anesthesia with propofol, while a median nerve stimulation is performed. We believe that our results could enable the design of a BCI based on median nerve stimulation, which could prevent AAGA.

OBJECTIVE

To our knowledge, no published studies have investigated the detection of electroencephalographic (EEG) patterns in relation to peripheral nerve stimulation over the sensorimotor cortex during general anesthesia. The main objective of this study is to describe the changes in terms of event-related desynchronization and event-related synchronization modulations, in the EEG signal over the motor cortex during general anesthesia with propofol while a median nerve stimulation is performed.

METHODS

STIM-MOTANA is an interventional and prospective study conducted with patients scheduled for surgery under general anesthesia, involving EEG measurements and median nerve stimulation at two different times: (1) when the patient is awake before surgery (2) and under general anesthesia. A total of 30 patients will receive surgery under complete intravenous anesthesia with a target-controlled infusion pump of propofol.

RESULTS

The changes in event-related desynchronization and event-related synchronization during median nerve stimulation according to the various propofol concentrations for 30 patients will be analyzed. In addition, we will apply 4 different offline machine learning algorithms to detect the median nerve stimulation at the cerebral level. Recruitment began in December 2022. Data collection is expected to conclude in June 2024.

CONCLUSIONS

STIM-MOTANA will be the first protocol to investigate median nerve stimulation cerebral motor effect during general anesthesia for the detection of intraoperative awareness. Based on strong practical and theoretical scientific reasoning from our previous studies, our innovative median nerve stimulation-based BCI would provide a way to detect intraoperative awareness during general anesthesia.

TRIAL REGISTRATION

Clinicaltrials.gov NCT05272202; https://clinicaltrials.gov/ct2/show/NCT05272202.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/43870.

Connected consciousness after tracheal intubation in young adults: an international multicentre cohort study

BACKGROUND

Connected consciousness, assessed by response to command, occurs in at least 5% of general anaesthetic procedures and perhaps more often in young people. Our primary objective was to establish the incidence of connected consciousness after tracheal intubation in young people aged 18-40 yr. The secondary objectives were to assess the nature of these responses, identify relevant risk factors, and determine their relationship to postoperative outcomes.

METHODS

This was an international, multicentre prospective cohort study using the isolated forearm technique to assess connected consciousness shortly after tracheal intubation.

RESULTS

Of 344 enrolled subjects, 338 completed the study (mean age, 30 [standard deviation, 6.3] yr; 232 [69%] female). Responses after intubation occurred in 37/338 subjects (11%). Females (13%, 31/232) responded more often than males (6%, 6/106). In logistic regression, the risk of responsiveness was increased with female sex (odds ratio [ORadjusted]=2.7; 95% confidence interval [CI], 1.1-7.6; P=0.022) and was decreased with continuous anaesthesia before laryngoscopy (ORadjusted=0.43; 95% CI, 0.20-0.96; P=0.041). Responses were more likely to occur after a command to respond (and not to nonsense, 13 subjects) than after a nonsense statement (and not to command, four subjects, P=0.049).

CONCLUSIONS

Connected consciousness occured after intubation in 11% of young adults, with females at increased risk. Continuous exposure to anaesthesia between induction of anaesthesia and tracheal intubation should be considered to reduce the incidence of connected consciousness. Further research is required to understand sex-related differences in the risk of connected consciousness.

Perception and practices of depth of anesthesia monitoring and intraoperative awareness event rate among Jordanian anesthesiologists: a cross-sectional study

BACKGROUND

Intraoperative awareness is the second most common complication of surgeries, and it negatively affects patients and healthcare professionals. Based on the limited previous studies, there is a wide variation in the incidence of intraoperative awareness and in the practices and attitudes toward depth of anesthesia (DoA) monitoring among healthcare systems and anesthesiologists. This study aimed to evaluate the Jordanian anesthesiologists' practice and attitudes toward DoA monitoring and estimate the event rate of intraoperative awareness among the participating anesthesiologists.

METHODS

A descriptive cross-sectional survey of Jordanian anesthesiologists working in public, private, and university hospitals was utilized using a questionnaire developed based on previous studies. Practice and attitude in using DoA monitors were evaluated. Anesthesiologists were asked to best estimate the number of anesthesia procedures and frequency of intraoperative awareness events in the year before. Percentages and 95% Confidence Intervals (95%CI) were reported and compared between groups using chi-square tests.

RESULTS

A total of 107 anesthesiologists responded and completed the survey. About one-third of the respondents (34.6%; 95% CI 26.1-44.2) had never used a DoA monitor and only 6.5% (95% CI 3.1-13.2) reported using it as a "daily practice". The use of a DoA monitor was associated with experience and type of health sector. However, 81.3% (95% CI 66.5-83.5) believed that currently available DoA monitors are effective for DoA monitoring and only 4.7% (95%CI 1.9-10.8) reported it as being "invalid". Most respondents reported that the main purpose of using a DoA monitor was to prevent awareness (86.0%; 95%CI 77.9-91.4), guide the delivery of anesthetics (63.6%; 95%CI 53.9-72.2), and reduce recovery time (57%; 95%CI 47.4-66.1). The event rate of intraoperative awareness was estimated at 0.4% among participating anesthesiologists. Most Jordanian hospitals lacked policy intending to prevent intraoperative awareness.

CONCLUSIONS

Most anesthesiologists believed in the role of DoA monitors in preventing intraoperative awareness, however, their attitudes and knowledge are inadequate, and few use DoA monitors in routine practices. In Jordan, large efforts are needed to regulate the use of DoA monitoring and reduce the incidence of intraoperative awareness.

[What's new … Patients are listening-communication under general anesthesia]

There is ample evidence of awareness of at least some unconscious patients. A recent multicenter study found significant reductions after therapeutic communication during general anesthesia in postoperative pain and analgesic consumption, as well as in postoperative nausea and vomiting (PONV) and antiemetic requirements in high-risk patients. Thus, an intraoperatively presentet text represents a simple non-pharmacological method to reduce side effects of surgery and anesthesia. This also offers treatment in other unconscious patients. However, another finding seems worth noting: the results of the study cannot be explained by the known intraoperative awareness and response of individual patients. Therefore, there should be a fundamental change in the way patients are treated in the operating room and intensive care unit, and background noise and careless conversations should be eliminated. 56 years after David Cheek formulated "BE CAREFUL, THE PATIENT IS LISTENING should be engraved over the door of every operating room, every recovery room, every intensive care unit in every hospital." after his first observations of patient perceptions, perhaps it is now time to finally heed this call and to use communication with unconscious patients that goes beyond the most necessary announcement of interventions and is therapeutically effective through positive suggestions. When in doubt, assume that the patient is listening.

Awareness With Paralysis Among Critically Ill Emergency Department Patients: A Prospective Cohort Study

OBJECTIVES

In mechanically ventilated patients, awareness with paralysis (AWP) can have devastating consequences, including post-traumatic stress disorder (PTSD), depression, and thoughts of suicide. Single-center data from the emergency department (ED) demonstrate an event rate for AWP factors higher than that reported from the operating room. However, there remains a lack of data on AWP among critically ill, mechanically ventilated patients. The objective was to assess the proportion of ED patients experiencing AWP and investigate modifiable variables associated with its occurrence.

DESIGN

An a priori planned secondary analysis of a multicenter, prospective, before-and-after clinical trial.

SETTING

The ED of three academic medical centers.

PATIENTS

Mechanically ventilated adult patients that received neuromuscular blockers.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All data related to sedation and analgesia were collected. AWP was the primary outcome, assessed with the modified Brice questionnaire, and was independently adjudicated by three expert reviewers. Perceived threat, in the causal pathway for PTSD, was the secondary outcome. A total of 388 patients were studied. The proportion of patients experiencing AWP was 3.4% ( n = 13), the majority of whom received rocuronium ( n = 12/13; 92.3%). Among patients who received rocuronium, 5.5% ( n = 12/230) experienced AWP, compared with 0.6% ( n = 1/158) among patients who did not receive rocuronium in the ED (odds ratio, 8.64; 95% CI, 1.11-67.15). Patients experiencing AWP had a higher mean ( sd ) threat perception scale score, compared with patients without AWP (15.6 [5.8] vs 7.7 [6.0]; p < 0.01).

CONCLUSIONS

AWP was present in a concerning proportion of mechanically ventilated ED patients, was associated with rocuronium exposure in the ED, and led to increased levels of perceived threat, placing patients at greater risk for PTSD. Studies that aim to further quantify AWP in this vulnerable population and eliminate its occurrence are urgently needed.

The effect of age on electroencephalogram measures of anesthesia hypnosis: A comparison of BIS, Alpha Power, Lempel-Ziv complexity and permutation entropy during propofol induction

Background

Improving anesthesia administration for elderly population is of particular importance because they undergo considerably more surgical procedures and are at the most risk of suffering from anesthesia-related complications. Intraoperative brain monitors electroencephalogram (EEG) have proved useful in the general population, however, in elderly subjects this is contentious. Probably because these monitors do not account for the natural differences in EEG signals between young and older patients. In this study we attempted to systematically characterize the age-dependence of different EEG measures of anesthesia hypnosis.

Methods

We recorded EEG from 30 patients with a wide age range (19-99 years old) and analyzed four different proposed indexes of depth of hypnosis before, during and after loss of behavioral response due to slow propofol infusion during anesthetic induction. We analyzed Bispectral Index (BIS), Alpha Power and two entropy-related EEG measures, Lempel-Ziv complexity (LZc), and permutation entropy (PE) using mixed-effect analysis of variances (ANOVAs). We evaluated their possible age biases and their trajectories during propofol induction.

Results

All measures were dependent on anesthesia stages. BIS, LZc, and PE presented lower values at increasing anesthetic dosage. Inversely, Alpha Power increased with increasing propofol at low doses, however this relation was reversed at greater effect-site propofol concentrations. Significant group differences between elderly patients (>65 years) and young patients were observed for BIS, Alpha Power, and LZc, but not for PE.

Conclusion

BIS, Alpha Power, and LZc show important age-related biases during slow propofol induction. These should be considered when interpreting and designing EEG monitors for clinical settings. Interestingly, PE did not present significant age differences, which makes it a promising candidate as an age-independent measure of hypnotic depth to be used in future monitor development.

End-tidal Anesthetic Concentration: Monitoring, Interpretation, and Clinical Application

Age-adjusted fraction of minimum alveolar concentration derived from end-tidal anesthetic partial pressure measurement remains a useful drug advisory display to help prevent awareness if interpreted with proper understanding of the quantal and probabilistic nature of minimum alveolar concentration, semantics, drug interactions, and hysteresis.

The Impact of Endoscopy Sedation Information Sheets on the Level of Concern Regarding Possible Awareness in Patients Undergoing Endoscopy Sedation

Sedation encompasses a continuum from complete unconsciousness to drowsiness and anxiolysis where some awareness might be expected. Most patients undergoing endoscopy sedation expect to be completely unconscious during the procedure and thus have unmet expectations regarding their state of consciousness. This study aimed to evaluate whether endoscopy sedation information sheets reduce the level of concern regarding possible awareness during endoscopy sedation at a major regional hospital. Our findings were that 28.8% of patients who received the endoscopy sedation information sheet (n = 82) were concerned about awareness during the procedure, compared to 36.5% of patients in the control group (n = 105). However, the difference was not statistically significant. We also found that the incidence of awareness was higher (13.9%) in the intervention group compared to 8.8% in the control group but, again, not statistically different. This study allowed us to elucidate the level of concern regarding possible awareness during sedation and the incidence of awareness during endoscopy sedation. This will enable future work investigating the role of endoscopy sedation information methods involving written and video material in assisting pre-procedure patient counselling.

Perception of auditory stimuli during general anesthesia and its effects on patient outcomes: a systematic review and meta-analysis

PURPOSE

Interest in implicit memory formation and unconscious auditory stimulus perception during general anesthesia has resurfaced as perioperative music has been reported to produce beneficial effects. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating explicit and implicit memory formation during general anesthesia and its effects on postoperative patient outcomes and recovery.

SOURCE

We performed a systematic literature search of Embase, Ovid Medline, and Cochrane Central from inception date until 15 October 2020. Eligible for inclusion were RCTs investigating intraoperative auditory stimulation in adult surgical patients under general anesthesia in which patients, healthcare staff, and outcome assessors were all blinded. We used random effects models for meta-analyses. This study adhered to the PRISMA guidelines and was registered in PROSPERO (CRD42020178087).

PRINCIPAL FINDINGS

Fifty-three (4,200 patients) of 5,859 identified articles were included. There was evidence of implicit memory formation in seven out of 17 studies (41%) when assessed using perceptual priming tasks. Mixed results were observed on postoperative behavioural and motor response after intraoperative suggestions. Intraoperative music significantly reduced postoperative pain (standardized mean difference [SMD], -0.84; 95% confidence interval [CI], -1.1 to -0.57; P < 0.001; I2 = 0; n = 226) and opioid requirements (SMD, -0.29; 95% CI, -0.57 to -0.015; P = 0.039; I2 = 36; n = 336), while positive therapeutic suggestions did not.

CONCLUSION

The results of this systematic review and meta-analysis show that intraoperative auditory stimuli can be perceived and processed during clinically adequate, general anesthesia irrespective of surgical procedure severity, leading to implicit memory formation without explicit awareness. Intraoperative music can exert significant beneficial effects on postoperative pain and opioid requirements. Whether the employed intraoperative anesthesia regimen is of influence is not yet clear.

Dopaminergic brainstem disconnection is common to pharmacological and pathological consciousness perturbation

Understanding the neural bases of consciousness is of basic scientific and clinical importance. Human neuroimaging has established that a network of interconnected brain regions known as the default mode network disintegrates in anesthesia and after brain damage that causes disorders of consciousness. However, the neurochemical underpinnings of this network change remain largely unknown. Motivated by preclinical animal work and clinical observations, we found that across pharmacological (sedation) and pathological (disorders of consciousness) consciousness perturbation, the dopaminergic source nucleus, the ventral tegmental area, disconnects from the main nodes of the default mode network. As the severity of this dopaminergic disconnection was associated with default mode network disintegration, we propose that dopaminergic modulation may be a central mechanism for consciousness maintenance.

Clinical research into consciousness has long focused on cortical macroscopic networks and their disruption in pathological or pharmacological consciousness perturbation. Despite demonstrating diagnostic utility in disorders of consciousness (DoC) and monitoring anesthetic depth, these cortico-centric approaches have been unable to characterize which neurochemical systems may underpin consciousness alterations. Instead, preclinical experiments have long implicated the dopaminergic ventral tegmental area (VTA) in the brainstem. Despite dopaminergic agonist efficacy in DoC patients equally pointing to dopamine, the VTA has not been studied in human perturbed consciousness. To bridge this translational gap between preclinical subcortical and clinical cortico-centric perspectives, we assessed functional connectivity changes of a histologically characterized VTA using functional MRI recordings of pharmacologically (propofol sedation) and pathologically perturbed consciousness (DoC patients). Both cohorts demonstrated VTA disconnection from the precuneus and posterior cingulate (PCu/PCC), a main default mode network node widely implicated in consciousness. Strikingly, the stronger VTA–PCu/PCC connectivity was, the more the PCu/PCC functional connectome resembled its awake configuration, suggesting a possible neuromodulatory relationship. VTA-PCu/PCC connectivity increased toward healthy control levels only in DoC patients who behaviorally improved at follow-up assessment. To test whether VTA–PCu/PCC connectivity can be affected by a dopaminergic agonist, we demonstrated in a separate set of traumatic brain injury patients without DoC that methylphenidate significantly increased this connectivity. Together, our results characterize an in vivo dopaminergic connectivity deficit common to reversible and chronic consciousness perturbation. This noninvasive assessment of the dopaminergic system bridges preclinical and clinical work, associating dopaminergic VTA function with macroscopic network alterations, thereby elucidating a critical aspect of brainstem–cortical interplay for consciousness.

Depth of Anesthesia Monitoring

The electroencephalogram (EEG) can be analyzed in its raw form for characteristic drug-induced patterns of change or summarized using mathematical parameters as a processed electroencephalogram (pEEG). In this article we aim to summarize the contemporary literature pertaining to the commonly available pEEG monitors including the effects of commonly used anesthetic drugs on the EEG and pEEG parameters, pEEG monitor pitfalls, and the clinical implications of pEEG monitoring for anesthesia, pediatrics, and intensive care.

Emergent tracheostomy during the pandemic of COVID-19: Slovenian National Recommendations

PURPOSE

Emergent tracheostomy under local anaesthesia is a reliable method of airway management when orotracheal intubation is not possible. COVID-19 is spread through aerosol making the emergent tracheostomy a high-risk procedure for surgeons. The surgical establishment of the air conduit in emergency scenarios must be adjusted for safety reasons.

METHODS

To establish the Slovenian National Guidelines for airway management in cannot intubate-cannot ventilate situations in COVID-19 positive patients.

RESULTS

Good communication and coordination between surgeon and anaesthesiologist is absolutely necessary. Deep general anaesthesia, full muscle relaxation and adequate preoxygenation without intubation are initial steps. The surgical cricothyrotomy is performed quickly, the thin orotracheal tube is inserted, the cuff is inflated and ventilation begins. Following patient stabilisation, the conversion to the tracheostomy is undertaken with the following features: skin infiltration with vasoconstrictor, a vertical incision, avoidance of electrical devices in favour of classical manners of haemostasis, the advancement of the tube towards the carina, performing the tracheal window in complete apnoea following adequate oxygenation, the insertion of non-fenestrated canulla attached to a heat and moisture exchanger, the fixation of canulla with stitches and tapes, and the cricothyrotomy entrance closure. Appropriate safety equipment is equally important.

CONCLUSION

The goal of the guidelines is to make the procedure safer for medical teams, without harming the patients. Further improvements of the guidelines will surely appear as COVID-19 is a new entity and there is not yet much experience in handling it.

Reversed and increased functional connectivity in non-REM sleep suggests an altered rather than reduced state of consciousness relative to wake

Sleep resting state network (RSN) functional connectivity (FC) is poorly understood, particularly for rapid eye movement (REM), and in non-sleep deprived subjects. REM and non-REM (NREM) sleep involve competing drives; towards hypersynchronous cortical oscillations in NREM; and towards wake-like desynchronized oscillations in REM. This study employed simultaneous electroencephalography-functional magnetic resonance imaging (EEG-fMRI) to explore whether sleep RSN FC reflects these opposing drives. As hypothesized, this was confirmed for the majority of functional connections modulated by sleep. Further, changes were directional: e.g., positive wake correlations trended towards negative correlations in NREM and back towards positive correlations in REM. Moreover, the majority did not merely reduce magnitude, but actually either reversed and strengthened in the opposite direction, or increased in magnitude during NREM. This finding supports the notion that NREM is best expressed as having altered, rather than reduced FC. Further, as many of these functional connections comprised “higher-order” RSNs (which have been previously linked to cognition and consciousness), such as the default mode network, this finding is suggestive of possibly concomitant alterations to cognition and consciousness.

Self-reported awareness during general anesthesia in pediatric patients: A study from Wake Up Safe

BACKGROUND

Awareness under general anesthesia occurs rarely, but can result in emotional trauma. Although well-studied in adults, there is a paucity of data on unintentional awareness in children.

AIMS

This case series examines instances of self-reported awareness registered with Wake Up Safe, a patient safety organization that maintains a database of adverse events in pediatric anesthesia.

METHODS

Cases of self-reported intraoperative awareness submitted to Wake Up Safe from January 1, 2010 to May 31, 2020 were reviewed for circumstances, causative factors, and level of harm.

RESULTS

Fourteen cases of self-reported intraoperative awareness out of 555 360 cases in patients aged 5-20 years were noted during the study period. Overall incidence of awareness was 2.52 (95% CI: 1.38-4.23) cases per 100 000 patients, or approximately 1:40 000. Self-reported intraoperative awareness was more frequently associated with cardiac and gastrointestinal endoscopic procedures. Incidence for cardiac procedures was 20.34 (95% CI: 8.18-41.90) cases per 100 000 patients. Incidence for gastrointestinal endoscopic procedures was 7.74 (95% CI: 1.60-22.62) cases per 100 000 patients. Most patients were assessed to have suffered harm.

CONCLUSIONS

Self-reported intraoperative awareness is a rare complication in pediatric patients that has implications for harm. Compared to awareness cases elicited by a questionnaire method, cases of self-reported awareness during general anesthesia may represent those that have a greater impact. A preoperative discussion of intraoperative awareness should be considered for procedures that carry a higher likelihood of awareness in order to mitigate harm.

Statement in Support of Revising the Uniform Determination of Death Act and in Opposition to a Proposed Revision

Discrepancies between the Uniform Determination of Death Act (UDDA) and the adult and pediatric diagnostic guidelines for brain death (BD) (the "Guidelines") have motivated proposals to revise the UDDA. A revision proposed by Lewis, Bonnie and Pope (the RUDDA), has received particular attention, the three novelties of which would be: (1) to specify the Guidelines as the legally recognized "medical standard," (2) to exclude hypothalamic function from the category of "brain function," and (3) to authorize physicians to conduct an apnea test without consent and even over a proxy's objection. One hundred seven experts in medicine, bioethics, philosophy, and law, spanning a wide variety of perspectives, have come together in agreement that while the UDDA needs revision, the RUDDA is not the way to do it. Specifically, (1) the Guidelines have a non-negligible risk of false-positive error, (2) hypothalamic function is more relevant to the organism as a whole than any brainstem reflex, and (3) the apnea test carries a risk of precipitating BD in a non-BD patient, provides no benefit to the patient, does not reliably accomplish its intended purpose, and is not even absolutely necessary for diagnosing BD according to the internal logic of the Guidelines; it should at the very least require informed consent, as do many procedures that are much more beneficial and less risky. Finally, objections to a neurologic criterion of death are not based only on religious belief or ignorance. People have a right to not have a concept of death that experts vigorously debate imposed upon them against their judgment and conscience; any revision of the UDDA should therefore contain an opt-out clause for those who accept only a circulatory-respiratory criterion.

Anesthesia-related care dissatisfaction: a cohort historical study to reveal related risks

BACKGROUND

Most previous reports have used questionnaires to investigate patient satisfaction regarding anesthesia-related care. We retrospectively investigated the dissatisfaction rate for anesthesia and the contributing factors for it using a questionnaire including anesthesia-related adverse events and a simplified patient satisfaction scale.

METHODS

This is a retrospective review of an institutional registry containing 21,606 anesthesia cases. We conducted multivariate logistic analysis in 9,429 patients using the incidence of dissatisfaction as a dependent variable and other covariates, including items of anesthesia registry and a postoperative questionnaire, as independent variables to investigate factors significantly associated with the risk of dissatisfaction with anesthesia.

RESULTS

In the study population, 549 patients rated the anesthesia service as dissatisfactory. Multivariate analysis identified the preoperative presence of coexisting disease [odds ratio (OR), 1.29; 95% confidence interval (CI), 1.05-1.59], combination of regional anesthesia (OR, 1.44; 95% CI, 1.10-1.88), self-reported awareness (OR, 1.99; 95% CI, 1.29-3.06), postoperative nausea and vomiting (PONV) (OR, 1.54; 95% CI, 1.25-1.90), occurrence of nightmares (OR, 1.96; 95% CI, 1.52-2.53), and the number of days taken to visit a postoperative anesthesia consultation clinic (OR, 1.01; 95% CI, 1.00-1.02) to be independently associated with dissatisfaction with anesthesia service.

CONCLUSIONS

Patients with coexisting disease, undergoing a combination of regional anesthesia, with self-reported awareness, experiencing PONV, suffering from nightmares, and who took longer to visit a postoperative anesthesia consultation clinic tended to rate our anesthesia service as dissatisfactory. Although the exact reasons for the factors contributing to dissatisfaction are unknown, this study suggests that there is room to improve our service.

Optimizing Motor Intention Detection With Deep Learning: Towards Management of Intraoperative Awareness

OBJECTIVE

This article shows the interest in deep learning techniques to detect motor imagery (MI) from raw electroencephalographic (EEG) signals when a functional electrical stimulation is added or not. Impacts of electrode montages and bandwidth are also reported. The perspective of this work is to improve the detection of intraoperative awareness during general anesthesia.

METHODS

Various architectures of EEGNet were investigated to optimize MI detection. They have been compared to the state-of-the-art classifiers in Brain-Computer Interfaces (based on Riemannian geometry, linear discriminant analysis), and other deep learning architectures (deep convolution network, shallow convolutional network). EEG data were measured from 22 participants performing motor imagery with and without median nerve stimulation.

RESULTS

The proposed architecture of EEGNet reaches the best classification accuracy (83.2%) and false-positive rate (FPR 19.0%) for a setup with only six electrodes over the motor cortex and frontal lobe and for an extended 4-38 Hz EEG frequency range while the subject is being stimulated via a median nerve. Configurations with a larger number of electrodes result in higher accuracy (94.5%) and FPR (6.1%) for 128 electrodes (and respectively 88.0% and 12.9% for 13 electrodes).

CONCLUSION

The present work demonstrates that using an extended EEG frequency band and a modified EEGNet deep neural network increases the accuracy of MI detection when used with as few as 6 electrodes which include frontal channels.

SIGNIFICANCE

The proposed method contributes to the development of Brain-Computer Interface systems based on MI detection from EEG.

Propofol and sevoflurane affect intra-operative memory formation of words differently: A prospective cohort study

BACKGROUND

Memory priming seems possible even during apparently adequate anaesthesia. However, the effects of different anaesthetics and type of stimuli, by virtue of their specific neural underpinnings, have not been considered.

OBJECTIVE

To determine if intra-operative implicit memory is affected by the type of anaesthesia (propofol or sevoflurane) or by the type of stimuli (abstract or concrete words).

DESIGN

Two consecutive, randomised controlled experiments.

SETTING

Neurological institute in Milan, Italy.

PATIENTS

Forty-three patients undergoing anaesthesia with propofol (experiment 1) and 32 patients undergoing anaesthesia with sevoflurane (experiment 2). Patients were ASA I or II, age 18 to 65 years, native Italian speakers, right-handed and without any condition affecting memory or hearing.

INTERVENTION

During anaesthesia, the patients heard a list of either concrete or abstract words or no words at all (controls). Explicit memory was tested with an explicit recall task and the Brice Interview; implicit memory was assessed through a word stem completion test.

OUTCOME MEASURES

The number of explicitly recalled words, positivity to the Brice Interview, the proportion of target and nontarget hits, and a derived implicit memory score.

RESULTS

With propofol, the proportion of target hits was significantly greater than the proportion of nontarget hits for the concrete word experimental group (P = 0.018). The implicit memory score of the concrete word experimental group was significantly higher than the score of both the abstract word experimental group (P  = 0.000) and the concrete word control group (P = 0.023). With sevoflurane, the proportion of target hits was significantly higher than the proportion of nontarget hits for the abstract word experimental group only (P = 0.027). No patients had a BIS above 60 and no one could recall intra-operative events or words.

CONCLUSION

Intra-operative memory for words can form during apparently adequate BIS-guided anaesthesia but is modified by propofol or sevoflurane acting on different brain targets. Further studies on larger samples and using neuroimaging techniques are needed.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT03727464.

Awareness With Paralysis in Mechanically Ventilated Patients in the Emergency Department and ICU: A Systematic Review and Meta-Analysis

OBJECTIVE

Awareness with paralysis is a devastating complication for mechanically ventilated patients and can carry long-term psychologic sequelae. Hundreds of thousands of patients require mechanical ventilation in the emergency department and ICU annually, yet awareness has only been rigorously examined in the operating room (incidence ~0.1%). This report collates the global literature regarding the incidence of awareness with paralysis outside of the operating room.

DATA SOURCES

We searched OvidMedline, Embase, Scopus, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, conference proceedings, and reference lists.

STUDY SELECTION

Randomized or nonrandomized studies (except single case studies) reporting on awareness with paralysis in the emergency department or ICU were eligible.

DATA EXTRACTION

Two independent reviewers screened abstracts for eligibility.

DATA SYNTHESIS

The search identified 4,454 potentially eligible studies. Seven studies (n = 941 patients) were included for analysis. A random effects meta-analysis of proportions along with multiple subgroup analyses was performed. Significant between-study heterogeneity in reporting of awareness with paralysis was noted, and the quality of the evidence was low. Analyses stratified by: 1) good-quality studies and 2) use of the modified Brice questionnaire to detect awareness revealed estimates of 3.4% (95% CI, 0-10.2%) and 1.9% (95% CI, 1.0-3.0%), respectively.

CONCLUSIONS

The incidence of awareness with paralysis in mechanically ventilated patients in the emergency department and ICU, as evaluated in a small number of qualifying studies from this comprehensive systematic review, appears much higher than that reported from the operating room. Given the clinical and statistical heterogeneity, caution is warranted in the interpretation of these findings. Further high-quality studies are needed to both define the true incidence and to target the prevention of awareness with paralysis in this vulnerable patient cohort.

Preoptic Area Modulation of Arousal in Natural and Drug Induced Unconscious States

The role of the hypothalamic preoptic area (POA) in arousal state regulation has been studied since Constantin von Economo first recognized its importance in the early twentieth century. Over the intervening decades, the POA has been shown to modulate arousal in both natural (sleep and wake) as well as drug-induced (anesthetic-induced unconsciousness) states. While the POA is well known for its role in sleep promotion, populations of wake-promoting neurons within the region have also been identified. However, the complexity and molecular heterogeneity of the POA has made distinguishing these two populations difficult. Though multiple lines of evidence demonstrate that general anesthetics modulate the activity of the POA, the region's heterogeneity has also made it challenging to determine whether the same neurons involved in sleep/wake regulation also modulate arousal in response to general anesthetics. While a number of studies show that sleep-promoting POA neurons are activated by various anesthetics, recent work suggests this is not universal to all arousal-regulating POA neurons. Technical innovations are making it increasingly possible to classify and distinguish the molecular identities of neurons involved in sleep/wake regulation as well as anesthetic-induced unconsciousness. Here, we review the current understanding of the POA's role in arousal state regulation of both natural and drug-induced forms of unconsciousness, including its molecular organization and connectivity to other known sleep and wake promoting regions. Further insights into the molecular identities and connectivity of arousal-regulating POA neurons will be critical in fully understanding how this complex region regulates arousal states.

The minimal self hypothesis

For millennia self has been conjectured to be necessary for consciousness. But scant empirical evidence has been adduced to support this hypothesis. Inconsistent explications of "self" and failure to design apt experiments have impeded progress. Advocates of phenomenological psychiatry, however, have helped explicate "self," and employed it to explain some psychopathological symptoms. In those studies, "self" is understood in a minimalist sense, sheer "for-me-ness." Unfortunately, explication of the "minimal self" (MS) has relied on conceptual analysis, and applications to psychopathology have been hermeneutic, allowing for many degrees of interpretive latitude. The result is that MS's current scientific status is analogous to that of the "atom," at the time when "atom" was just beginning to undergo transformation from a philosophical to a scientific concept. Fortunately, there is now an opportunity to promote a similar transformation for "MS." Discovery of the brain's Default Mode Network (DMN) opened the door to neuroimaging investigations of self. Taking the DMN and other forms of intrinsic activity as a starting point, an empirical foothold can be established, one that spurs experimental research and that enables extension of research into multiple phenomena. New experimental protocols that posit "MS" can help explain phenomena hitherto not thought to be related to self, thereby hastening development of a mature science of self. In particular, targeting phenomena wherein consciousness is lost and recovered, as in some cases of Unresponsive Wakefulness Syndrome (UWS), allow for design of neuroimaging probes that enable detection of MS during non-conscious states. These probes, as well as other experimental protocols applied to NREM Sleep, General Anesthesia (GA), and the waking state, provide some evidence to suggest that not only can self and consciousness dissociate, MS might be a necessary precondition for conscious experience. Finally, these findings have implications for the science of consciousness: it has been suggested that "levels of consciousness" (LoC) is not a legitimate concept for the science of consciousness. But because we have the conceptual and methodological tools with which to refine investigations of MS, we have the means to identify a possible foundation-a bifurcation point-for consciousness, as well as the means by which to measure degrees of distance from that foundation. These neuroimaging investigations of MS position us to better assess whether LoC has a role to play in a mature science of consciousness.

Deep Learning Techniques to Improve Intraoperative Awareness Detection from Electroencephalographic Signals

Every year, millions of patients regain conscious- ness during surgery and can potentially suffer from post-traumatic disorders. We recently showed that the detection of motor activity during a median nerve stimulation from electroencephalographic (EEG) signals could be used to alert the medical staff that a patient is waking up and trying to move under general anesthesia [1], [2]. In this work, we measure the accuracy and false positive rate in detecting motor imagery of several deep learning models (EEGNet, deep convolutional network and shallow convolutional network) directly trained on filtered EEG data. We compare them with efficient non-deep approaches, namely, a linear discriminant analysis based on common spatial patterns, the minimum distance to Riemannian mean algorithm applied to covariance matrices, a logistic regression based on a tangent space projection of covariance matrices (TS+LR). The EEGNet improves significantly the classification performance comparing to other classifiers (p- value <; 0.01); moreover it outperforms the best non-deep classifier (TS+LR) for 7.2% of accuracy. This approach promises to improve intraoperative awareness detection during general anesthesia.

The Raw and Processed Electroencephalogram as a Monitoring and Diagnostic Tool

In this narrative review, different aspects of electroencephalogram (EEG) monitoring during anesthesia are approached, with a special focus on cardiothoracic and vascular anesthesia, from the basic principles to more sophisticated diagnosis and monitoring utilities. The available processed EEG-derived indexes of the depth of the hypnotic component of anesthesia have well-defined limitations and usefulness. They prevent intraoperative awareness with recall in specific patient populations and under a specific anesthetic regimen. They prevent intraoperative overdose, and they shorten recovery times. They also help to avoid lengthy intraoperative periods of suppression activity, which are known to be deleterious in terms of outcome. Other than those available indexes, the huge amount of information contained in the EEG currently is being used only partially. Several other areas of interest regarding EEG during anesthesia have emerged in terms of anesthesia mechanisms elucidation, nociception monitoring, and diagnosis or prevention of brain insults.

[The relation between preoperative anxiety and awareness during anesthesia: an observational study]

BACKGROUND

Anxiety is a state of worry caused by the anticipation of external or internal danger. Awareness During Anesthesia (ADA) is an unexpected memory recall during anesthesia. In this study, we aimed to determine the factors that affect preoperative anxiety and observe the incidence of ADA, as well as to determine the anxiety levels of these patients with a history of ADA.

METHODS

This study was planned to be prospective, observational, and cross-sectional. Patients in whom septoplasty was planned, who was admitted to the anesthesiology outpatients between March 2018 and September 2018, were ASA I-II, and aged 18-70 years were included in the study. The demographic characteristics of patients were recorded. The State-Trait Anxiety Inventory (STAI) was used to determine anxiety during a preoperative evaluation. The modified Brice awareness score was used simultaneously to determine previous ADA.

RESULTS

The anxiety scores of patients who were conscious during anesthesia were higher than other patients. The mean STAI score was 40.85±14.8 in the 799 patients who met the inclusion criteria of this study. When the anxiety scores were compared, the scores were higher in females than in males (p < 0.05). The mean STAI score was found as 40.3±13.8 in patients who dreamed during anesthesia.

CONCLUSION

It is important to determine the anxiety levels of patients in the preoperative period to prevent the associated complications. Preoperative anxiety, besides preventing ADA, should be dealt with in a multidisciplinary manner. ADA should be carefully questioned while evaluating previous anesthesia experiences.

A combined single-stage procedure to treat brain AVM

Complete resection of brain arteriovenous malformation (AVM) is a surgical challenge, mainly due to risk of intraoperative rupture. The objective of this feasibility study was to analyze complete resection rate at 3 months and clinical outcome at 6 months after treatment of brain AVM by combined single-stage embolization and surgical resection. A retrospective observational study from July 2015 to February 2019 was conducted at the Department of Neurosurgery of Strasbourg University Hospital, France. Decision to treat was taken on the basis of history of AVM rupture, symptomatic AVM, or morphologic risk factors for rupture. Complete resection rate was assessed on postoperative cerebral subtraction angiography at 3 months and clinical outcome at 6 months was evaluated on the modified Rankin Scale (mRS). In the 16 patients treated for symptomatic brain AVM, the rate of complete resection was 75%, resection with residual shunt 18.7%, and incomplete resection with residual nidus 6.3%. Good clinical outcome (mRS=0 or 1) was achieved in 81.3% of patients at 6 months. The transfusion rate was 7.1%. There were procedural complications in 12.5% of patients but no intraoperative ruptures. This combined single-stage procedure allows extensive preoperative embolization of the AVM, facilitating surgical microdissection by identifying the dissection plane and perforating arteries and allowing the operator to work in close contact with the nidus without fear of intraoperative rupture.

Unintended intraoperative awareness: An analysis of Perioperative Anesthetic Adverse Events in Thailand (PAAd Thai)

BACKGROUND

Despite the improvement of anesthetic-related modalities, the incidence of unintended intraoperative awareness remains at around 0.005-0.038%.

OBJECTIVE

We aimed to describe the intraoperative awareness incidents that occurred across Thailand between January to December, 2015.

METHODS

Observational data was collected from 22 hospitals throughout Thailand. The awareness category was selected from incident reports according to the Perioperative Anesthetic Adverse Events in Thailand (PAAd Thai) study database and descriptive statistics were analyzed. The awareness characteristics and the related factors were recorded.

RESULTS

A total of nine intraoperative awareness episodes from 2000 incidents were observed. The intraoperative awareness results were as follows: experience of pain (38.1%), perception of sound (33.3%), perception of intubation (9.5%) and feeling of paralysis (14.3%). The observed factors that affect intraoperative awareness were anesthesia-related (100%), patient-related (55.5%), surgery-related (22.2%) and systematic process-related (22.2%). The contributing factors were situational inexperience (77.8%) and inappropriate patient evaluation (44.4%). An awareness of anesthetic performer (100%) and experience (88.9%) were defined as incident-mitigating factors. The suggested corrective strategies were quality assurance activity (88.9%), improved supervision (44.4%) and equipment utilization (33.3%), respectively.

CONCLUSION

Nine intraoperative awareness incidents were observed, however the causes were preventable. The anesthetic component seems to be the most influential to prevent these events.

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.