Depth of anaesthesia monitoring: time to reject the index?

Effect of propofol combined with remimazolam besylate on blood pressure during general anesthesia induction in patients undergoing gynecological laparoscopic surgery: single-centre randomized controlled trial

BACKGROUND

Hypotension often occurs during intraoperative anesthesia induction in gynecological laparoscopic surgery. Remimazolam is reportedly associated with lesser intraoperative hypotension than propofol. This trial was conducted to evaluate the effect of propofol combined with remimazolam besylate on post-induction hypotension (PIH) in patients undergoing gynecological laparoscopic surgery.

METHODS

All enrolled patients were randomly assigned to receive propofol (Group P), remimazolam besylate plus propofol (Group PR), or remimazolam besylate (Group R). Patients in group P received 2.0 mg/kg propofol, Sufentanil 0.4 μg/kg, and rocuronium bromide 0.8 mg/kg; Patients in group PR received remimazolam besylate 0.2 mg/kg, propofol 1.0 mg/kg, Sufentanil 0.4 μg/kg, and rocuronium bromide 0.8 mg/kg; Patients in group R received remimazolam besylate 0.4 mg/kg, Sufentanil 0.4 μg/kg, and rocuronium bromide 0.8 mg/kg; the anesthesia was maintained with propofol 4-10 mg/kg/h and remifentanil 0.1-0.3 μg/kg/min. The primary outcome was the incidence of hypotension after anesthesia induction. Hypotension was defined as a mean arterial pressure (MAP) reduced 30% or more from the baseline MAP value or MAP < 65 mmHg. Blood pressure was recorded five times during anesthesia. Time points T0, T1, T2, T3 and T4, were base line, before tracheal intubation, 1 min after tracheal intubation, 5 min after intubation, and immediately after surgical skin incision, respectively. The secondary outcomes were heart rate and bispectral index (BIS). Heart rate and BIS were measured from T0 to T4.

RESULTS

One hundred sixty-nine patients were included in this study. A total of 30 patients in the three groups developed hypotension after anesthesia induction, among which the incidence of PIH induced in group P was 31.6% (18/57), the incidence of PIH induced in group PR was 14.3% (8/56), and the incidence of PIH induced group R 7.1% (4/56), and there was a statistical difference in the incidence of PIH between the three groups (χ2 = 12.24, p = 0.0022). The heart rates in group R (70.53 ± 13.36 bpm, 88.48 ± 13.53 bpm, and 72.68 ± 13.42 bpm) were significantly higher than that in group P (63.68 ± 10.76 bpm, 80.25 ± 12.50 bpm, and 66.35 ± 11.56 bpm) at T1, T2 and T4 (p < 0.05, respectively). The heart rate in group R (88.48 ± 13.53 bpm) was significantly higher than that in group PR (80.00 ± 13.42 bpm) at T2 (p < 0.05). There was no statistically significant difference between group PR and group P (p > 0.05). BIS was significantly higher in group R than that in group P and in group PR at T3 and T4 (p < 0.05, respectively). There was no statistically significant difference between group PR and group P (p > 0.05).

CONCLUSIONS

Both Propofol plus remimazolam besylate and remimazolam besylate alone can reduce PIH, but propofol plus remimazolam besylate smooths the heart rate after general anesthesia undergoing gynecological laparoscopic.

TRIAL REGISTRATION

This trial was retrospectively registered at http://www.chictr.org.cn (06/06/2024, ChiCTR-2400085401).

A new function of offset response in the primate auditory cortex: marker of temporal integration

Offset responses are traditionally viewed as indicators of sound cessation. Here, we investigate offset responses to auditory click trains, examining how they are modulated by inter-click intervals (ICIs) and train duration. Using extracellular recordings and electrocorticography (ECoG) in non-human primates, alongside electroencephalography (EEG) in humans, we show that offset responses are significantly influenced by both ICI and train length, thereby establishing them as markers of temporal integration. We introduce the concept of the 'Neuronal Integrative Window' (NIW), defined as the temporal span during which neurons integrate stimuli to produce or modulate the temporal integration signal. Our data reveal that on the neuronal level, the auditory cortex (AC) exhibits a more expansive NIW than the medial geniculate body (MGB), integrating stimuli over longer durations and showing a preference for larger ICIs. Furthermore, our results indicate that offset responses could serve as potential biomarkers for neurological and psychiatric conditions, highlighted by their sensitivity to pharmacological modulation with ketamine. This study advances our understanding of auditory temporal processing and proposes a novel approach for assessing and monitoring brain health.

Strategic Integration: A Cross-Disciplinary Review of the fNIRS-EEG Dual-Modality Imaging System for Delivering Multimodal Neuroimaging to Applications

Background: Recent years have seen a surge of interest in dual-modality imaging systems that integrate functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) to probe brain function. This review aims to explore the advancements and clinical applications of this technology, emphasizing the synergistic integration of fNIRS and EEG. Methods: The review begins with a detailed examination of the fundamental principles and distinctive features of fNIRS and EEG techniques. It includes critical technical specifications, data-processing methodologies, and analysis techniques, alongside an exhaustive evaluation of 30 seminal studies that highlight the strengths and weaknesses of the fNIRS-EEG bimodal system. Results: The paper presents multiple case studies across various clinical domains-such as attention-deficit hyperactivity disorder, infantile spasms, depth of anesthesia, intelligence quotient estimation, and epilepsy-demonstrating the fNIRS-EEG system's potential in uncovering disease mechanisms, evaluating treatment efficacy, and providing precise diagnostic options. Noteworthy research findings and pivotal breakthroughs further reinforce the developmental trajectory of this interdisciplinary field. Conclusions: The review addresses challenges and anticipates future directions for the fNIRS-EEG dual-modal imaging system, including improvements in hardware and software, enhanced system performance, cost reduction, real-time monitoring capabilities, and broader clinical applications. It offers researchers a comprehensive understanding of the field, highlighting the potential applications of fNIRS-EEG systems in neuroscience and clinical medicine.

Unconscious classification of quantitative electroencephalogram features from propofol versus propofol combined with etomidate anesthesia using one-dimensional convolutional neural network

Objective

Establishing a convolutional neural network model for the recognition of characteristic raw electroencephalogram (EEG) signals is crucial for monitoring consciousness levels and guiding anesthetic drug administration.

Methods

This trial was conducted from December 2023 to March 2024. A total of 40 surgery patients were randomly divided into either a propofol group (1% propofol injection, 10 mL: 100 mg) (P group) or a propofol-etomidate combination group (1% propofol injection, 10 mL: 100 mg, and 0.2% etomidate injection, 10 mL: 20 mg, mixed at a 2:1 volume ratio) (EP group). In the P group, target-controlled infusion (TCI) was employed for sedation induction, with an initial effect site concentration set at 5-6 μg/mL. The EP group received an intravenous push with a dosage of 0.2 mL/kg. Six consciousness-related EEG features were extracted from both groups and analyzed using four prediction models: support vector machine (SVM), Gaussian Naive Bayes (GNB), artificial neural network (ANN), and one-dimensional convolutional neural network (1D CNN). The performance of the models was evaluated based on accuracy, precision, recall, and F1-score.

Results

The power spectral density (94%) and alpha/beta ratio (72%) demonstrated higher accuracy as indicators for assessing consciousness. The classification accuracy of the 1D CNN model for anesthesia-induced unconsciousness (97%) surpassed that of the SVM (83%), GNB (81%), and ANN (83%) models, with a significance level of p < 0.05. Furthermore, the mean and mean difference ± standard error of the primary power values for the EP and P groups during the induced period were as follows: delta (23.85 and 16.79, 7.055 ± 0.817, p < 0.001), theta (10.74 and 8.743, 1.995 ± 0.7045, p < 0.02), and total power (24.31 and 19.72, 4.588 ± 0.7107, p < 0.001).

Conclusion

Large slow-wave oscillations, power spectral density, and the alpha/beta ratio are effective indicators of changes in consciousness during intravenous anesthesia with a propofol-etomidate combination. These indicators can aid anesthesiologists in evaluating the depth of anesthesia and adjusting dosages accordingly. The 1D CNN model, which incorporates consciousness-related EEG features, represents a promising tool for assessing the depth of anesthesia.

Clinical Trial Registration

https://www.chictr.org.cn/index.html.

Assessment of depth of sedation using Bispectral Index™ monitoring in patients with severe traumatic brain injury in UK intensive care units

Introduction

Severe traumatic brain injury affects ∼4500 per year across the UK. Most patients undergo a period of sedation to prevent secondary brain injury, however the optimal sedation target is unclear. This study aimed to assess the relationship between the electroencephalogram (EEG)-based Bispectral Index™ (BIS™) value and the clinical sedation score, along with other clinical outcomes.

Methods

Patients with severe traumatic brain injury in four UK ICUs were recruited to have blinded BIS data collected for a 24-h period while sedated on the ICU. Drug, physiological, and outcome data were recorded from the ICU record. Sedation management was at the discretion of the ICU clinical team.

Results

Twenty-six participants were recruited to the study. The mean BIS was 38 (inter-quartile range 29-44) and there was poor correlation between BIS and sedation score as a group (correlation coefficient 0.17, 95% confidence interval 0.08-0.26), however the spread in BIS values increased with decreasing sedation score. There was no statistically significant relationship between BIS and intracranial pressure, vasopressor use, osmotherapy use, or need for an additional sedative.

Conclusion

This study supports previous work showing that BIS decreases with decreasing sedation score. However, the variation in BIS values increased with deeper levels of clinical sedation. Patients may not be benefiting from the full potential of sedation in traumatic brain injury and further studies of sedation titrated to an EEG-based parameter are needed.

Clinical trial registration

NCT03575169.

Lower alpha frequency of intraoperative frontal EEG is associated with postoperative delirium: A secondary propensity-matched analysis

BACKGROUND

Postoperative delirium (POD) is a serious complication of surgery, especially in the elderly patient population. It has been proposed that decreasing the amount of anesthetics by titrating to an EEG index will lower POD rate, but clear evidence is missing. A strong age-dependent negative correlation has been reported between the peak oscillatory frequency of alpha waves and end-tidal anesthetic concentration, with older patients generating slower alpha frequencies. We hypothesized, that slower alpha oscillations are associated with a higher rate of POD.

METHOD

Retrospective analysis of patients` data from a prospective observational study in cardiac surgical patients approved by the Bernese Ethics committee. Frontal EEG was recorded during Isoflurane effect-site concentrations of 0.7 to 0.8 and peak alpha frequency was measured at highest power between 6 and 17 Hz. Delirium was assessed by chart review. Demographic and clinical characteristics were compared between POD and non-POD groups. Selection bias was addressed using nearest neighbor propensity score matching (PSM) for best balance. This incorporated 18 variables, whereas patients with missing variable information or without an alpha oscillation were excluded.

RESULT

Of the 1072 patients in the original study, 828 were included, 73 with POD, 755 without. PSM allowed 328 patients into the final analysis, 67 with, 261 without POD. Before PSM, 8 variables were significantly different between POD and non-POD groups, none thereafter. Mean peak alpha frequency was significantly lower in the POD in contrast to non-POD group before and after matching (7.9 vs 8.9 Hz, 7.9 vs 8.8 Hz respectively, SD 1.3, p < 0.001).

CONCLUSION

Intraoperative slower frontal peak alpha frequency is independently associated with POD after cardiac surgery and may be a simple intraoperative neurophysiological marker of a vulnerable brain for POD. Further studies are needed to investigate if there is a causal link between alpha frequency and POD.

Intraoperative monitoring of the central and peripheral nervous systems: a narrative review

The central and peripheral nervous systems are the primary target organs during anaesthesia. At the time of the inception of the British Journal of Anaesthesia, monitoring of the central nervous system comprised clinical observation, which provided only limited information. During the 100 yr since then, and particularly in the past few decades, significant progress has been made, providing anaesthetists with tools to obtain real-time assessments of cerebral neurophysiology during surgical procedures. In this narrative review article, we discuss the rationale and uses of electroencephalography, evoked potentials, near-infrared spectroscopy, and transcranial Doppler ultrasonography for intraoperative monitoring of the central and peripheral nervous systems.