Awareness under general anesthesia

Impaired cerebral autoregulation detected in early prevasospasm period is associated with unfavorable outcome after spontaneous subarachnoid hemorrhage: an observational prospective pilot study

BACKGROUND

Subarachnoid hemorrhage (SAH) patients with cerebral autoregulation (CA) impairment at an early post-SAH period are at high risk of unfavorable outcomes due to delayed cerebral ischemia (DCI) or other complications. Limited evidence exists for an association between early-stage CA impairments and SAH patient outcomes. The objective of this prospective study was to explore associations between CA impairments detected in early post-SAH snapshot examinations and patient outcomes.

METHODS

The pilot observational study included 29 SAH patients whose CA status was estimated 2-3 days after spontaneous aneurysm rupture and a control group of 15 healthy volunteers for comparison. Inflatable leg recovery boots (reboots.com, Germany) were used for the safe controlled generation of arterial blood pressure (ABP) changes necessary for reliable CA examination. At least 5 inflation‒deflation cycles of leg recovery boots with a 2-3 min period were used during examinations. CA status was assessed according to the delay time (∆TCBFV) measured between ABP(t) and cerebral blood flow velocity (CBFV(t)) signals during artificially induced ABP changes at boot deflation cycle. CBFV was measured in middle cerebral artery by using transcranial Doppler device.

RESULTS

Statistically significant differences in ∆TCBFV were found between SAH patients with unfavorable outcomes (∆TCBFV = 1.37 ± 1.23 s) and those with favorable outcomes (∆TCBFV = 2.86 ± 0.99 s) (p < 0.001). Early assessment of baroreflex sensitivity (BRS) during the deflation cycle showed statistically significant differences between the DCI and non-DCI patient groups (p = 0.039).

CONCLUSIONS

A relatively small delay of ∆TCBFV <1.6 s between CBFV(t) and ABP(t) waves could be an early warning sign associated with unfavorable outcomes in SAH patients. The BRS during boot deflation can be used as a biomarker for the prediction of DCI.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT06028906. Registered 31 August 2023 - Retrospectively registered, https://www.

CLINICALTRIALS

gov/study/NCT06028906 .

Signal processing and machine learning algorithm to classify anaesthesia depth

BACKGROUND

Poor assessment of anaesthetic depth (AD) has led to overdosing or underdosing of the anaesthetic agent, which requires continuous monitoring to avoid complications. The evaluation of the central nervous system activity and autonomic nervous system could provide additional information on the monitoring of AD during surgical procedures.

METHODS

Observational analytical single-centre study, information on biological signals was collected during a surgical procedure under general anaesthesia for signal preprocessing, processing and postprocessing to feed a pattern classifier and determine AD status of patients. The development of the electroencephalography index was carried out through data processing and algorithm development using MATLAB V.8.1.

RESULTS

A total of 25 men and 35 women were included, with a total time of procedure average of 109.62 min. The results show a high Pearson correlation between the Complexity Brainwave Index and the indices of the entropy module. A greater dispersion is observed in the state entropy and response entropy indices, a partial overlap can also be seen in the boxes associated with deep anaesthesia and general anaesthesia in these indices. A high Pearson correlation might be explained by the coinciding values corresponding to the awake and general anaesthesia states. A high Pearson correlation might be explained by the coinciding values corresponding to the awake and general anaesthesia states.

CONCLUSION

Biological signal filtering and a machine learning algorithm may be used to classify AD during a surgical procedure. Further studies will be needed to confirm these results and improve the decision-making of anaesthesiologists in general anaesthesia.

Dose-related adaptive reconstruction of DMN in isoflurane administration: a study in the rat

BACKGROUND

The anesthetic states are accompanied by functional alterations. However, the dose-related adaptive alterations in the higher-order network under anesthesia, e. g. default mode network (DMN), are poorly revealed.

METHODS

We implanted electrodes in brain regions of the rat DMN to acquire local field potentials to investigate the perturbations produced by anesthesia. Relative power spectral density, static functional connectivity (FC), fuzzy entropy of dynamic FC, and topological features were computed from the data.

RESULTS

The results showed that adaptive reconstruction was induced by isoflurane, exhibiting reduced static and stable long-range FC, and altered topological features. These reconstruction patterns were in a dose-related fashion.

CONCLUSION

These results might impart insights into the neural network mechanisms underlying anesthesia and suggest the potential of monitoring the depth of anesthesia based on the parameters of DMN.

[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.

Accidental Awareness Under General Anesthesia During Cesarean Section: An Observational Study

Background

A Caesarean section (CS) if performed under general anesthesia (GA) is a procedure with an increased risk of accidental awareness. This study aimed to examine the incidence of accidental awareness under GA in hospitals in the Republic of Srpska (Bosnia and Herzegovina) where GA for CS is performed in a significantly higher percentage compared to spinal anesthesia.

Methodology

In the period from 2016 to 2018, a multicenter, prospective, observational study was conducted in five medical centers in the Republic of Srpska (Bosnia and Herzegovina). The study included 1,161 patients who underwent CS. A total of 427 (36.7%) patients had elective and 734 (63.3%) had emergency CSs. The patients were surveyed postoperatively using the modified Brice questionnaire.

Results

Of the 1,161 patients included in the study, 12 (1.03%) reported memory in the period between induction and emergence of anesthesia. Five (0.43%) of them reported definite and seven (0.6%) possible and unlikely awareness. Significant psychological trauma due to pain was reported by two patients. Dreams during anesthesia were reported by 42 patients (3.61%) and five of them stated that the dreams were unpleasant.

Conclusions

Accidental awareness under GA during CS has a significant incidence in medical centers in the Republic of Srpska (Bosnia and Herzegovina). According to our findings, creating new protocols for GA when performing CS is necessary.

Intraoperative Awareness in Patients Undergoing Cardiac Surgery in an Academic Center in the North of Iran

Background

Coronary artery bypass grafting (CABG) has distinctive characteristics that may increase the risk of awareness during general anesthesia (AGA).

Objectives

This study was conducted to assess the incidence of AGA in cardiac surgery in an academic hospital in Guilan, Iran.

Methods

This descriptive cross-sectional study was performed in Dr. Heshmat Hospital in Rasht, Iran. Eligible patients candidates for CABG were enrolled in the survey in 2022. After surgery, when the patient was cooperative enough, a questionnaire including demographic data and specialized questions related to different stages of anesthesia was completed via face-to-face interviews. The data were analyzed using IBM SPSS Statistics 21 with chi-square, Fisher's exact, and t-test.

Results

The data from 322 patients were analyzed, of whom 14 (4.3%) experienced AGA. Among them, the "feeling of fear and anxiety" reported by 9 (39.1%) cases was the most common awareness state. "Dreaming during surgery and anesthesia" and "feeling unable to move during anesthesia,", each reported by 6 (26.1%) cases, were the other common types of awareness state. None of the demographic data had a significant association with the occurrence of AGA.

Conclusions

The incidence of AGA during CABG was almost acceptable according to the credible evidence.

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.

The Impact of Scripted Self-Hypnotic Relaxation on the Periprocedural Experience and Anesthesiologist Sedation Use in the Pediatric Cardiac Catheterization Suite: A Prospective Randomized Controlled Trial

Purpose

To assess the impact on children of self-hypnotic relaxation scripts read by trained staff prior to the induction of anesthesia and/or extubation on the periprocedural experience.

Patients and Methods

A total of 160 children aged 7–18 years undergoing a cardiac catheterization intervention under general anesthesia were randomized into 4 groups: (1) a pre-procedure (PP-script) read prior to entering the procedural room, (2) a script read prior to extubation (PX-Script), (3) both PP- and PX-Scripts read and (4) no script read. Anxiety and pain were rated on self-reported 0–10 scales. The modified Yale Preoperative Anxiety Scale was used for preoperative anxiety. The effect of script reading was associated with outcomes by linear regression for continuous variables, and logistic regression for binary variables in two-sided tests at a significance level of 0.05. Results are given in odds ratios (OR) and 95% confidence intervals (CI).

Results

Data were available for 158 patients. Reading the PP-Script prior to anesthesia was associated with a significant reduction in the use of intraoperative sedatives from 30% to 14% (OR 0.40; CI 0.18–0.88; p = 0.02) by the anesthesiologists, who were blinded to group attribution until extubation. This was despite the children not self-reporting significantly lower levels of anxiety or pain. The PX-Script did not change outcomes. Among groups, there was no significant difference in room time, postoperative recovery time and pain.

Conclusion

Reading a PP-Script for guidance in self-hypnotic relaxation can result in less need for intravenous sedation in the judgment of the anesthesiologist, independent of the children’s self-reported anxiety and pain. This raises interesting questions about subconscious patient–physician interactions affecting pain management.

Clinicaltrials.gov Identifier

NCT02347748.

Influence of epidural anesthesia and general anesthesia on thromboembolism in patients undergoing total knee arthroplasty

OBJECTIVE

This study aimed to explore the application value of epidural and general anesthesia in total knee arthroplasty (TKA).

METHODS

We first retrospectively analyzed 156 patients who underwent total knee arthroplasty in our hospital from January 2019 to January 2020 as subjects. The control group (CG) included 86 subject who were treated with general anesthesia. The remaining 70 subjects with epidural anesthesia were divided to a research group (RG). The recovery and adverse reactions after surgery were compared. The coagulation function before and after surgery was analyzed. The incidence of deep vein thrombosis (DVT) after surgery was observed. The expression of inflammatory factors and the improvement of cognitive function were assessed before surgery, followed by 6 and 12 h after surgery. The pain degree of patients was compared at 6 and 12 h after surgery.

RESULTS

Compared with the CG, the recovery condition after surgery in the RG were dramatically lower, the concentrations of PLT, PT, and APTT in the RG were higher, while FBG was markedly lower. The incidence of postoperative venous thrombosis in the RG was lower. The TNF-α, IL-6 levels, and VAS scores in the RG were remarkably lower at 6 and 12 h after surgery. MMSE score was significantly higher than CG score. The total incidence of adverse reactions in the RG was markedly lower.

CONCLUSION

Epidural anesthesia can improve blood coagulation and cognitive function in patients undergoing TKA and reduce the incidence of DVT and the degree of postoperative pain.

Time-Frequency Analysis of EEG Signals and GLCM Features for Depth of Anesthesia Monitoring

One of the important tasks in the operating room is monitoring the depth of anesthesia (DoA) during surgery, and noninvasive techniques are very popular. Hence, we propose a new scheme for DoA monitoring considering the time-frequency analysis of electroencephalography (EEG) signals and GLCM features extracted from them. To this end, at first, the time-frequency map (TFM) of each channel of each EEG is computed by smoothed pseudo-Wigner–Ville distribution (SPWVD), where the EEG signal used in this paper is recorded in 15 channels. After that, we consider the gray-level co-occurrence matrix (GLCM) to obtain the content of TFM, and after that, four features such as homogeneity, correlation, energy, and contrast are obtained for each GLCM. Finally, after the selection of efficient features using the minimum redundancy maximum relevance (MRMR) method, the K-nearest neighbor (KNN) classifier is utilized to determine the DoA. Here, we consider the three states, namely, deep hypnotic, surgical anesthesia, and sedation and awake states according to bispectral index (BIS), and each EEG epoch is classified to these states. We also employ data augmentation to enhance the training phase and increase accuracy. We obtain the accuracy and confusion matrix of the proposed method. We also analyze the effects of a number of gray levels of GLCM, distance measure in KNN classifier, and parameters of data augmentation on the performance of the proposed method. Results indicate the efficiency of the proposed method to determine the DoA during surgery.

Poincaré Plot Area of Gamma-Band EEG as a Measure of Emergence From Inhalational General Anesthesia

The Poincaré plot obtained from electroencephalography (EEG) has been used to evaluate the depth of anesthesia. A standalone EEG Analyzer application was developed; raw EEG signals obtained from a bispectral index (BIS) monitor were analyzed using an on-line monitoring system. Correlations between Poincaré plot parameters and other measurements associated with anesthesia depth were evaluated during emergence from inhalational general anesthesia. Of the participants, 20 were adults anesthetized with sevoflurane (adult_{_SEV}), 20 were adults anesthetized with desflurane (adult_{_DES}), and 20 were pediatric patients anesthetized with sevoflurane (ped_{_SEV}). EEG signals were preprocessed through six bandpass digital filters (f0: 0.5–47 Hz, f1: 0.5–8 Hz, f2: 8–13 Hz, f3: 13–20 Hz, f4: 20–30 Hz, and f5: 30–47 Hz). The Poincaré plot-area ratio (PP_AR = PP_{A_fx}/PP_{A_f0}, fx = f1∼f5) was analyzed at five frequency ranges. Regardless of the inhalational anesthetic used, there were strong linear correlations between the logarithm of PP_AR at f5 and BIS (R² = 0.67, 0.79, and 0.71, in the adult_{_SEV}, adult_{_DES}, and ped_{_SEV} groups, respectively). As an additional observation, a part of EMG activity at the gamma range of 30–47 Hz probably influenced the calculations of BIS and PP_{AR_f5} with a non-negligible level. The logarithm of PP_AR in the gamma band was most sensitive to state changes during the emergence process and could provide a new non-proprietary parameter that correlates with changes in BIS during measurement of anesthesia depth.

Malewicz N, Ebel M, K. Zahn P, H. Meyer-Frießem C. Pupillometric Monitoring of Nociception in Cardiac Anesthesia

BACKGROUND

High-dose opioids are conventionally used for cardiac anesthesia, but without monitoring of nociception. In non-cardiac surgical procedures the intra - operative dose of opioids can be individualized and reduced with pupillometric monitoring of the pupillary pain index (PPI; scale 1-9). A randomized controlled trial was carried out to explore whether pupillometry can be used for nociception monitoring in cardiac anesthesia and whether it leads to opioid reduction.

METHODS

A sample of 57 cardiac surgery patients receiving continuously administered sufentanil (initial dosage 0.7 μg*kg-¹*h-¹) was divided into a PPI group (sufentanil reduction if PPI<3 up to a minimum of 0.15 μg*kg-¹*h-¹, n=32) and a control group (standard anesthesia; n = 25). The primary outcome was the time from the end of anesthesia to extubation. The secondary outcomes were total intraoperative dose of sufentanil/noradrenaline, postoperative pain intensity (numeric rating scale [NRS] 0-10) and intraoperative awareness. German Clinical Trials Registry no. DRKS 00012329.

RESULTS

The primary outcome, extubation time, did not differ between the two groups (1.14 h, 95% confidence interval [-0.99; 3.27], p = 0.592). Compared with the control patients (68% male, age 70 ± 10.4 years, PPI 1.1 ± 0.2), the mean sufentanil infusion rate in the PPI patients (81% male, age 68 ± 10.3 years, PPI 1.1 ± 0.2) decreased by 81.8% (-0.68 μg*kg-¹*h-¹ [-0,7; -0.67], p<0.001) to the predetermined minimum level, without intraoperative awareness. Moreover, the noradrenaline dose was reduced by 56% (1235.51 μg [321.91; 2149.12], p = 0.005) and the postoperative pain intensity by 45% (2.11 NRS [0.93; 3.3] after 24 h, p = 0.003).

CONCLUSION

Pupillometry is appropriate for nociception monitoring in cardiac anesthesia. Thereby a considerable reduction of intraoperative opioids as well as increased intraoperative hemodynamic stability was achieved and postoperative opioid-induced hyperalgesia was prevented. The consistently low PPI scores, indicating adequate analgesia, suggest that further reduction of opioid doses is feasible.

Impairment in behavioral sedation in rats during periods of elevated global geomagnetic activity

The influence of the geomagnetic environment on the human organism and other biological entities has been a topic of intense scientific investigation. A large and growing body of evidence has linked elevated geomagnetic activity with effects on an array of neurological, immunological, cardiovascular, and psychological outcomes. For example, elevations in the rates of epileptic seizures, suicides, aggressive behavior, sleep disturbances, and sudden unexpected death from cardiac pathologies have been reported to occur more frequently on days associated with increased geomagnetic activity. Additional evidence also suggests that geomagnetic conditions might have an impact on the biological actions of specific drugs classes that have important implications for pain management, sedation, and seizure control. The present study set out to determine if periods of enhanced geomagnetic activity could influence the induction of behavioral sedation by pentobarbital in rodents undergoing a routine surgical procedure. The surgical records of 250 subjects were retrospectively analyzed, and the occurrence of complete behavioral sedation (e.g., loss of righting reflex, lack of nociceptive response to tail pinch, absence of corneal and conjunctive reflexes) was noted. We found a significant correlation between periods of increased geomagnetic activity and the number of non-responsive surgical patients (i.e., patients still demonstrating behavioral responsiveness after treatment with pentobarbital). These findings provide evidence for the first time that the potential efficacy of some surgical anesthetic compounds might be reduced on days associated with increased geomagnetic activity. Potential mechanisms are presented, and the broad implications of these findings to phenomena such as surgical awareness are discussed.

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

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3596-9) contains supplementary material, which is available to authorized users.

Magnitude and Associated Factors of Awareness with Recall under General Anesthesia in Amhara Regional State Referral Hospitals, 2018

Introduction

Awareness with recall of intraoperative events is an infrequent but potentially devastating complication of general anesthesia, with a reported incidence of 0.1-0.2% in low-risk patients. Higher incidence is expected in resource-limited operation room setups and in high-risk patients. Awareness can result in significant distress to patients and long-term psychological consequences, including symptoms associated with posttraumatic stress disorder, anxiety, night mares, night terror, dissatisfaction with surgical service, and sometimes even suicide.

Objective

To assess the magnitude and associated factors of awareness with recall under general anesthesia in Amhara regional state referral hospitals.

Method

An institution-based cross-sectional study was conducted on 1065 patients who underwent surgery under general anesthesia from January 1 to June 30, 2018. The study participants were selected by systematic random sampling from 4 referral hospitals. The modified Brice questionnaire was used to detect awareness under general anesthesia. Interviewer-administered structured questionnaire and chart review were employed. Data with complete information were entered in to SPSS version 20 computer software. Descriptive statics and bivariate and multivariable analysis were computed. A P-value less than 0.2 was used to select candidate variables for multivariable logistic regression. A P-value less than 0.05 was used to declare statistical significance.

Result

1065 patients were included in the study which makes the response rate of 90.7%. The magnitude of awareness with recall under general anesthesia was found to be 8.2% of which 4.9%, 2.6%, and 0.7% of patients reported hearing voice, pain, and sensation of breathing tube, respectively. Lack of premedication was the only significantly associated factor for awareness with recall under general anesthesia (AOR = 3.014, 95% CI (1.201 to 7.565)).

Conclusion and Recommendation

Our study showed higher magnitude of awareness with recall under general anesthesia. Lack of premedication was the only associated factor with awareness with recall under general anesthesia. Anesthetists should give emphasis to prevent the possibility of awareness under general anesthesia by providing premedication. Cohort studies should be done including the consequences of awareness with recall under general anesthesia.

Median Nerve Stimulation Based BCI: A New Approach to Detect Intraoperative Awareness During General Anesthesia

Hundreds of millions of general anesthesia are performed each year on patients all over the world. Among these patients, 0.1–0.2% are victims of Accidental Awareness during General Anesthesia (AAGA), i.e., an unexpected awakening during a surgical procedure under general anesthesia. Although anesthesiologists try to closely monitor patients using various techniques to prevent this terrifying phenomenon, there is currently no efficient solution to accurately detect its occurrence. We propose the conception of an innovative passive brain-computer interface (BCI) based on an intention of movement to prevent AAGA. Indeed, patients typically try to move to alert the medical staff during an AAGA, only to discover that they are unable to. First, we examine the challenges of such a BCI, i.e., the lack of a trigger to facilitate when to look for an intention to move, as well as the necessity for a high classification accuracy. Then, we present a solution that incorporates Median Nerve Stimulation (MNS). We investigate the specific modulations that MNS causes in the motor cortex and confirm that they can be altered by an intention of movement. Finally, we perform experiments on 16 healthy participants to assess whether an MI-based BCI using MNS is able to generate high classification accuracies. Our results show that MNS may provide a foundation for an innovative BCI that would allow the detection of AAGA.

Do Complexity Measures of Frontal EEG Distinguish Loss of Consciousness in Geriatric Patients Under Anesthesia?

While geriatric patients have a high likelihood of requiring anesthesia, they carry an increased risk for adverse cognitive outcomes from its use. Previous work suggests this could be mitigated by better intraoperative monitoring using indexes defined by several processed electroencephalogram (EEG) measures. Unfortunately, inconsistencies between patients and anesthetic agents in current analysis techniques have limited the adoption of EEG as standard of care. In attempts to identify new analyses that discriminate clinically-relevant anesthesia timepoints, we tested 1/f frequency scaling as well as measures of complexity from nonlinear dynamics. Specifically, we tested whether analyses that characterize time-delayed embeddings, correlation dimension (CD), phase-space geometric analysis, and multiscale entropy (MSE) capture loss-of-consciousness changes in EEG activity. We performed these analyses on EEG activity collected from a traditionally hard-to-monitor patient population: geriatric patients on beta-adrenergic blockade who were anesthetized using a combination of fentanyl and propofol. We compared these analyses to traditional frequency-derived measures to test how well they discriminated EEG states before and after loss of response to verbal stimuli. We found spectral changes similar to those reported previously during loss of response. We also found significant changes in 1/f frequency scaling. Additionally, we found that our phase-space geometric characterization of time-delayed embeddings showed significant differences before and after loss of response, as did measures of MSE. Our results suggest that our new spectral and complexity measures are capable of capturing subtle differences in EEG activity with anesthesia administration-differences which future work may reveal to improve geriatric patient monitoring.

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.

Distinguishing Anesthetized from Awake State in Patients: A New Approach Using One Second Segments of Raw EEG

Objective: The objective of this study was to test whether properties of 1-s segments of spontaneous scalp EEG activity can be used to automatically distinguish the awake state from the anesthetized state in patients undergoing general propofol anesthesia.

Methods: Twenty five channel EEG was recorded from 10 patients undergoing general intravenous propofol anesthesia with remifentanil during anterior cervical discectomy and fusion. From this, we extracted properties of the EEG by applying the Directed Transfer Function (DTF) directly to every 1-s segment of the raw EEG signal. The extracted properties were used to develop a data-driven classification algorithm to categorize patients as “anesthetized” or “awake” for every 1-s segment of raw EEG.

Results: The properties of the EEG signal were significantly different in the awake and anesthetized states for at least 8 of the 25 channels (p < 0.05, Bonferroni corrected Wilcoxon rank-sum tests). Using these differences, our algorithms achieved classification accuracies of 95.9%.

Conclusion: Properties of the DTF calculated from 1-s segments of raw EEG can be used to reliably classify whether the patients undergoing general anesthesia with propofol and remifentanil were awake or anesthetized.

Significance: This method may be useful for developing automatic real-time monitors of anesthesia.

Helping Children Cope with Medical Tests and Interventions

Medical procedures and tests become a challenge when anxiety and pain make it difficult for the patient to cooperate or remain still when needed. Fortunately a short intervention with hypnoidal language at the onset of a procedure induces a positive and sustained change in the way pain and anxiety are processed. While anesthesia may appear to be a simple solution to eliminate pain, the adverse effects of pre-anesthesia anxiety on postoperative behavior and recovery are often not fully appreciated. This paper discusses options for self-hypnotic relaxation that are applicable to interactions with children. The high suggestibility of children makes it relatively easy to engage them in make-believe scenarios. Avoidance of negative suggestions is key in avoiding nocebo effects that may be difficult to overcome later. Once a child is immersed in his or her preferred scenario or hobby/activity of choice, environmental and procedural stimuli can be easily integrated in the imagery. Ego-strengthening metaphors that tie in features of strength, confidence, or resilience are particularly empowering. Even when children are fully under general anesthesia they may still have recall of what is said in the room and therefore caution in word choice should be maintained.

[Undesired awareness phenomena during general anesthesia: Evidence-based state of knowledge, current discussions and strategies for prevention and management]

Patient awareness during general anesthesia and the later recall of what happened during surgery can be experienced by patients as horrifying events that leave lasting mental trauma in the form of posttraumatic stress syndrome (PTSS). Awareness is related to a temporary insufficient depth of anesthesia. This phenomenon has been discussed for more than 20 years. According to randomized controlled studies, in the absence of risk factors awareness phenomena occur in 1-2 per 1000 operations involving general anesthesia (0.1-0.2%) and are classified as occasionally occurring critical events. An astonishing twist occurred elicited by the recent data from the 5th National Audit Project from Great Britain (NAP5) published in the British Journal of Anaesthesia and in Anaesthesia. The NAP5 evaluated patient reports of accidental awareness during general anesthesia (AAGA) in a multicenter manner in more than 2.7 million cases and indicated incidences of awareness of only 1:19,600, a frequency 20 times less than previously reported. These results gave rise to some controversy. It seems likely that, due to the absence of structured interviews, the NAP5 data only demonstrated the tip of the iceberg and may have vastly underestimated the real incidence of intraoperative awareness. The present overview summarizes the current knowledge about awareness. Furthermore, it addresses the question whether the awareness problem has been overestimated by evidence-based criteria or underestimated by the results of the NAP5. The responsibility for sufficient anesthesia in the clinical routine requires knowledge of awareness risks and potential sequelae. A formal recommendation from the German Society of Anesthesia and Intensive Care Medicine (DGAI) concerning awareness is not yet available; however, the recognition of evidence-based strategies in the management of anesthesia may minimize the occurrence of awareness and its sequelae.

Comparison of the Effects of Thiopental Sodium and Propofol on Haemodynamics, Awareness and Newborns During Caesarean Section Under General Anaesthesia

OBJECTIVE

To compare the effects of propofol and thiopental on haemodynamics, awareness and newborns in pregnant women undergoing elective caesarean section.

METHODS

Seventy pregnant women were assigned into two equal groups. For anaesthesia induction, 2 mg kg(-1) propofol (Group P) and 5 mg kg(-1) thiopental (Group T) were administered. Maternal haemodynamic parameters and bispectral index (BIS) values were recorded before induction, in 1-minute intervals within the first 10 minutes after induction and in 5-minute intervals thereafter, during skin incision, uterine incision, removal of infant, uterine sutures, skin sutures, eye opening and extubation in all cases. Cord blood gas analysis and 1- and 5-minute APGAR scores were recorded. In all cases, a keyword was spelled to ear during removal of the infant, and at the first postoperative hour, patients were questioned. Important time periods of surgery and anaesthesia and also the first postoperative hour haemodynamic values, pain scores, nausea and vomiting were noted.

RESULTS

The demographic data were similar among cases. In Group T, systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and mean arterial pressure (MAP) at the first 2 minutes after induction and heart rate (HR) at almost all time points were significantly higher. BIS values from induction to the eighth minute and skin incision, uterine incision and removal of the infant were lower in Group P. No patient remembered the keyword spelled, while 4 patients reported dreaming during general anaesthesia. The effects of propofol and thiopental sodium on 1- and 5-minute APGAR scores, cord blood gas values and postoperative visual analogue scale (VAS) scores were similar.

CONCLUSION

Propofol is a more appropriate anaesthetic agent than thiopental in anaesthesia for caesareans, since it provides better anaesthestic depth and more rapid recovery.

Awareness and apgar score in elective Cesarean section under general anesthesia with propofol or Isoflurane: A prospective, randomized, double-blinded clinical trial study

Background:

Awareness is a postoperative recall of events experienced under general anesthesia. In this study, we compared the incidence of awareness between two routine methods used, inhalation (Isoflurane) and intravenous protocol (Propofol), in elective Cesarean section, and also evaluated the effect of these two different methods on the apgar score of newborns.

Materials and Methods:

In this prospective, clinical trial study, 90 pregnant women candidates for elective Cesarean section were randomly enrolled, after taking written consent. Induction of anesthesia in both groups was provided by propofol and succinylcholine in the same manner, and maintenance of anesthesia in Group 1 was provided by propofol 100 μg/kg/minute and in Group 2 with isoflurane 1 MAC, to maintain the bispectral index (BIS) between 45 and 60. Blood pressure, heart rate, electrocardiography (ECG), and also Etco2 and o2sat were recorded throughout the surgery and finally analyzed and compared.

Results:

From 90 patients, four cases of confirmed awareness were found in the propofol group and three cases in the Isoflurane group (8/9% vs. 6/7%), but the apgar scores were comparable between the two groups. Meanwhile there were no significant differences between the two groups in basic information, neonatal apgar scores, hemodynamic changes, and BIS, Electromyography (EMG), and signal quality index (SQI) values.

Conclusion:

According to the patient's state, diagnosis of the anesthesiologist, and other criteria like price and its availability, we could use these drugs in general anesthesia during Cesarean section, although it is recommended that more studies be done to compare the effect of these two drugs in larger groups.

Is anesthesia dangerous?

BACKGROUND

Recent years have seen a rise in overall anesthesia-related mortality.

METHOD

Selective review of the literature.

RESULTS

Anesthesia-related mortality has fallen from 6.4/10 000 in the 1940s to 0.4/100 000 at present, largely because of the introduction of safety standards and improved training. The current figure of 0.4/100 000 applies to patients without major systemic disease; mortality is higher among patients with severe accompanying illnesses, yet in this group, too, perioperative mortality can be reduced by appropriate anesthetic management. Moreover, the use of regional anesthesia can also improve the outcome of major surgery.

CONCLUSION

A recent increase in the percentage of older and multimorbid patients among persons undergoing surgery, along with the advent of newer types of operation that would have been unthinkable in the past, has led to an apparent rise in anesthesia-associated mortality, even though the quality of anesthesiological care is no worse now than in the past. On the contrary, in recent years, better anesthetic management has evidently played an important role in improving surgical outcomes.