The Effect of Sedation on Cortical Activation: A Randomized Study Comparing the Effects of Sedation With Midazolam, Propofol, and Dexmedetomidine on Auditory Processing

Increased task-relevant fMRI responsiveness in comatose cardiac arrest patients is associated with improved neurologic outcomes

Early prediction of the recovery of consciousness in comatose cardiac arrest patients remains challenging. We prospectively studied task-relevant fMRI responses in 19 comatose cardiac arrest patients and five healthy controls to assess the fMRI's utility for neuroprognostication. Tasks involved instrumental music listening, forward and backward language listening, and motor imagery. Task-specific reference images were created from group-level fMRI responses from the healthy controls. Dice scores measured the overlap of individual subject-level fMRI responses with the reference images. Task-relevant responsiveness index (Rindex) was calculated as the maximum Dice score across the four tasks. Correlation analyses showed that increased Dice scores were significantly associated with arousal recovery (P < 0.05) and emergence from the minimally conscious state (EMCS) by one year (P < 0.001) for all tasks except motor imagery. Greater Rindex was significantly correlated with improved arousal recovery (P = 0.002) and consciousness (P = 0.001). For patients who survived to discharge (n = 6), the Rindex's sensitivity was 75% for predicting EMCS (n = 4). Task-based fMRI holds promise for detecting covert consciousness in comatose cardiac arrest patients, but further studies are needed to confirm these findings. Caution is necessary when interpreting the absence of task-relevant fMRI responses as a surrogate for inevitable poor neurological prognosis.

Alterations in whole-brain dynamic functional stability during memory tasks under dexmedetomidine sedation

Purpose

This study aimed to explore the neurological effects of dexmedetomidine-induced sedation on memory using functional stability, a whole-brain voxel-wise dynamic functional connectivity approach.

Methods

A total of 16 participants (10 men) underwent auditory memory task-related fMRI in the awake state and under dexmedetomidine sedation. Explicit and implicit memory tests were conducted 4 h after ceasing dexmedetomidine administration. One-sample Wilcoxon signed rank test was applied to determine the formation of explicit and implicit memory in the two states. Functional stability was calculated and compared voxel-wise between the awake and sedated states. The association between functional stability and memory performance was also assessed.

Results

In the awake baseline tests, explicit and implicit memory scores were significantly different from zero (p < 0.05). In the tests under sedation, explicit and implicit memory scores were not significantly different from zero. Compared to that at wakeful baseline, functional stability during light sedation was reduced in the medial prefrontal cortex, left angular gyrus, and right hippocampus (all clusters, p < 0.05, GRF-corrected), whereas the left superior temporal gyrus exhibited higher functional stability (cluster p < 0.05, GRF-corrected). No significant associations were observed between functional stability and memory test scores.

Conclusions

The distribution and patterns of alterations in functional stability during sedation illustrate the modulation of functional architecture by dexmedetomidine from a dynamic perspective. Our findings provide novel insight into the dynamic brain functional networks underlying consciousness and memory in humans.

Delirium in Older Adults: What a Surgeon Needs to Know

Delirium remains a challenging clinical problem in hospitalized older adults, especially for postoperative patients. This complication, with a high risk of postoperative mortality and an increased length of stay, frequently occurs in older adult patients. This brief narrative paper aims to review the recent literature regarding delirium and its most recent update. We also offer physicians a brief and essential clinical practice guide to managing this acute and common disease.

How general anesthetics work: from the perspective of reorganized connections within the brain

General anesthesia is critical for various procedures and surgeries. Despite the widespread use of anesthetics, their precise mechanisms remain poorly understood. Anesthetics inevitably act on the brain, primarily through the modulation of target receptors. Even if the action is specific to an individual neuron, however, long-range effects can occur due to the tremendous interconnectedness of neuronal activity. The strength of this connectivity can be understood using mathematical models that allow for the study of neuronal connectivity dynamics. These models also allow researchers to develop hypotheses on the candidate mechanisms of action of different types of anesthesia. This review highlights the theoretical background associated with the study of the mechanisms of action of anesthetics. We propose a candidate framework that describes how anesthetics act on the brain and consciousness in general.

Morphometry and functional connectivity of auditory cortex in school-age children with profound language disabilities: Five comparative case studies

Many neurodevelopmental conditions imply absent or severely reduced language capacities at school age. Evidence from functional magnetic resonance imaging is highly limited. We selected a series of five cases scanned with the same fMRI paradigm and the aim of relating individual language profiles onto underlying patterns of functional connectivity (FC) across auditory language cortex: three with neurogenetic syndromes (Coffin-Siris, Landau-Kleffner, and Fragile-X), one with idiopathic intellectual disability, one with autism spectrum disorder (ASD). Compared to both a group with typical development (TD) and a verbal ASD group (total N = 110), they all showed interhemispheric FC below two standard deviations of the TD mean. Children with higher language scores showed higher intrahemispheric FC between Heschl's gyrus and other auditory language regions, as well as an increase of FC during language stimulation compared to rest. An increase of FC in forward vs. reversed speech in the posterior and middle temporal gyri was seen across all cases. The Coffin-Siris case, the most severe, also had the most anomalous FC patterns and showed reduced myelin content, while the Landau-Kleffner case showed reduced cortical thickness. These results suggest potential for neural markers and mechanisms of severe language processing deficits under highly heterogeneous etiological conditions.

Neuropsychopharmacological effects of midazolam on the human brain

As a commonly used anesthetic agent, midazolam has the properties of water-soluble, rapid onset, and short duration of action. With the rapid development in the field of neuroimaging, numerous studies have investigated how midazolam acts on the human brain to induce the alteration of consciousness. However, the neural bases of midazolam-induced sedation or anesthesia remain beginning to be understood in detail. In this review, we summarize findings from neuroimaging studies that have used midazolam to study altered consciousness at different levels and content. We also compare the results to those of neuroimaging studies using diverse anesthetic agents and describe the common neural correlates of anesthetic-induced alteration of consciousness.

Dexmedetomidine is superior to midazolam for sedation and cerebral protection in postoperative hypertensive intracerebral hemorrhage patients: a retrospective study

OBJECTIVE

Dexmedetomidine has a good sedative effect and does not affect the judgment of the patient's consciousness level. However, its effectiveness for sedation and cerebral protection after craniotomy in hypertensive intracerebral hemorrhage (HICH) patients is unknown.

METHODS

A retrospective study of 164 postoperative HICH patients who underwent sedation with dexmedetomidine or midazolam was conducted. The Ramsay sedation score, mean arterial pressure (MAP), heart rate (HR), pulse oxygen saturation (SpO₂), and respiratory rate were measured at the indicated time points. Human soluble protein-100β (S-100β) and neuron-specific enolase (NSE) levels were also compared between the two groups.

RESULTS

Dexmedetomidine treatment showed a significantly better effect than midazolam on decreasing the frequency of apparent agitation. The MAP and HR, but not the SpO_2, were significantly decreased and lower than those in midazolam group. Detection of plasma S-100β and NSE proteins revealed a significant decrease in the dexmedetomidine group compared with the midazolam group. The 6-month follow-up evaluation indicated a significantly better prognosis of postoperative HICH patients treated with dexmedetomidine than for those treated with midazolam.

CONCLUSIONS

Dexmedetomidine is effective for sedation in postoperative HICH patients and may be beneficial for their outcome.

Pain-related behavior and brain activation in cynomolgus macaques with naturally occurring endometriosis

STUDY QUESTION

Can pain be objectively assessed in macaques with naturally occurring endometriosis?

SUMMARY ANSWER

Behavioral, pharmacological and in vivo brain imaging findings indicate that pain can be quantified in macaques with endometriosis.

WHAT IS KNOWN ALREADY

Endometriosis is characterized by abdominopelvic hypersensitity. The mechanism by which endometriosis evokes pain is largely unknown, as currently available analgesics offer limited pain relief. Thus, there is a need for both greater understanding of the in vivo mechanism of endometriosis-associated pain and better methods of testing novel therapeutics.

STUDY DESIGN, SIZE, DURATION

Pain-related behavior and brain activation were assessed in five cynomolgus macaques with endometriosis. Three healthy female macaques served as controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Abdominopelvic sensitivity to force was assessed with an algometer. Activation of brain areas using block design force stimulation and the effects of a single dose of the analgesic drug morphine and 2-month treatment with the progestin dienogest on brain activation were observed via functional magnetic resonance imaging.

MAIN RESULTS AND THE ROLE OF CHANCE

Pain response thresholds in macaques with endometriosis were significantly less than that of healthy macaques (P = 0.0003). In addition, non-noxious force activated the insula and thalamus, which was reduced with morphine and 2-month dienogest treatment.

LIMITATIONS, REASONS FOR CAUTION

The specific role of cysts, such as peritoneal cysts, in endometriosis pain was not explored. While non-noxious stimulation activated the insula and thalamus, macaques were sedated during fMRI scans. Current findings need further confirmation in a larger cohort.

WIDER IMPLICATIONS OF THE FINDINGS

The current study demonstrated central sensitization and related pain behavior in macaques with naturally occurring endometriosis. Altered functioning of the central nervous system could be the focus of future mechanistic studies and for the development of novel therapeutics.

STUDY FUNDING/COMPETING INTEREST(S)

Supported by a grant from the Shizuoka Industrial Foundation. All authors are employees of Hamamatsu Pharma Research, Inc.

General Anesthesia: A Probe to Explore Consciousness

General anesthesia reversibly alters consciousness, without shutting down the brain globally. Depending on the anesthetic agent and dose, it may produce different consciousness states including a complete absence of subjective experience (unconsciousness), a conscious experience without perception of the environment (disconnected consciousness, like during dreaming), or episodes of oriented consciousness with awareness of the environment (connected consciousness). Each consciousness state may potentially be followed by explicit or implicit memories after the procedure. In this respect, anesthesia can be considered as a proxy to explore consciousness. During the recent years, progress in the exploration of brain function has allowed a better understanding of the neural correlates of consciousness, and of their alterations during anesthesia. Several changes in functional and effective between-region brain connectivity, consciousness network topology, and spatio-temporal dynamics of between-region interactions have been evidenced during anesthesia. Despite a set of effects that are common to many anesthetic agents, it is still uneasy to draw a comprehensive picture of the precise cascades during general anesthesia. Several questions remain unsolved, including the exact identification of the neural substrate of consciousness and its components, the detection of specific consciousness states in unresponsive patients and their associated memory processes, the processing of sensory information during anesthesia, the pharmacodynamic interactions between anesthetic agents, the direction-dependent hysteresis phenomenon during the transitions between consciousness states, the mechanisms of cognitive alterations that follow an anesthetic procedure, the identification of an eventual unitary mechanism of anesthesia-induced alteration of consciousness, the relationship between network effects and the biochemical or sleep-wake cycle targets of anesthetic agents, as well as the vast between-studies variations in dose and administration mode, leading to difficulties in between-studies comparisons. In this narrative review, we draw the picture of the current state of knowledge in anesthesia-induced unconsciousness, from insights gathered on propofol, halogenated vapors, ketamine, dexmedetomidine, benzodiazepines and xenon. We also describe how anesthesia can help understanding consciousness, we develop the above-mentioned unresolved questions, and propose tracks for future research.

[Perioperative music-induced analgesia : Comparison of the effect of music on pain between preoperative, intraoperative and postoperative application]

BACKGROUND

Despite suitable analgesia procedures and interventions only approximately 24% of inpatients with strong to very strong pain receive adequate treatment. Besides opioids, which are associated with numerous side effects and risks, non-pharmacological approaches are increasingly being used. In this context, one of the oldest known methods are music interventions; however, the state of evidence is heterogeneous and there are no explicit manuals and recommendations for the effective implementation of music interventions.

OBJECTIVE

This review aimed to determine the optimal time point at which perioperative music interventions can most effectively relieve pain.

MATERIAL AND METHODS

A PubMed search was conducted and publications investigating the effect of music during the preoperative, intraoperative and postoperative stages of various interventions were identified.

RESULTS

During the preoperative phase, only positive effects of music on pain relief have been reported but availability of data is sparse. During the intraoperative stage of a medical intervention the effect of music seems to be mediated by the type of anesthesia procedure and sedation depth. Only patients who can consciously perceive the music seem to profit from it. Positive alleviating effects on subjective pain perception and analgesia needs were shown in the postoperative stage.

CONCLUSION

Music is a non-pharmacological method to alleviate pain, which is free of side effects. Important considerations for the use of music interventions for relief of acute pain associated with surgery are discussed taking into account numerous mediating factors, which influence the efficacy of the treatment.

Distinguishing analgesic drugs from non-analgesic drugs based on brain activation in macaques with oxaliplatin-induced neuropathic pain

The antineoplastic agent oxaliplatin is a first-line treatment for colorectal cancer. However, neuropathic pain, characterized by hypersensitivity to cold, emerges soon after treatment. In severe instances, dose reduction or curtailing treatment may be necessary. While a number of potential treatments for oxaliplatin-induced neuropathic pain have been proposed based on preclinical findings, few have demonstrated efficacy in randomized, placebo-controlled clinical studies. This failure could be related, in part, to the use of rodents as the primary preclinical species, as there are a number of distinctions in pain-related mechanisms between rodents and humans. Also, an indicator of preclinical pharmacological efficacy less subjective than behavioral endpoints that is translatable to clinical usage is lacking. Three days after oxaliplatin treatment in Macaca fascicularis, a significantly reduced response latency to cold (10 °C) water was observed, indicating cold hypersensitivity. Cold-evoked bilateral activation of the secondary somatosensory (SII) and insular (Ins) cortex was observed with functional magnetic resonance imaging. Duloxetine alleviated cold hypersensitivity and significantly attenuated activation in both SII and Ins. By contrast, neither clinically used analgesics pregabalin nor tramadol affected cold hypersensitivity and cold-evoked activation of SII and Ins. The current findings suggest that suppressing SII and Ins activation leads to antinociception, and, therefore, could be used as a non-behavioral indicator of analgesic efficacy in patients with oxaliplatin-induced neuropathic pain.

Application of remifentanil combined with propofol in the diagnosis of colon cancer with awakening painless digestive endoscopy

Anesthetic effect of remifentanil combined with propofol in awakening painless endoscopy was analyzed. Retrospective analysis of 120 cases of colon cancer were treated in Dongying People's Hospital from June 2015 to December 2017. All of them were treated by awakening painless digestive endoscopy, divided into 60 cases in observation group (combined with remifentanil and propofol anesthesia), and 60 cases in control group (combined intravenous anesthesia of finanib and propofol). The data were respectively recorded at time-points of oxygen inhalation, intubation for 10 min, awakening time, waking time, and the time-points for each represented as the time-points of T1, T2, T3, T4, T5 and recorded the diastolic blood pressure (DBP), respiratory rate (RR) and heart rate (HR), and compared the awakening effect and the occurrence of adverse reaction. There was no significant difference in the DBP index between the two groups at time-point T1 (P>0.05). The time-points of T2, T3, T4 and T5 were significantly different from the observation group (P<0.05). There was no significant difference in RR index between the two groups and between the same groups (P>0.05). Compared with the control group, the awakening time and consciousness recovering of the observation group is lower (P<0.05). The incidence of adverse reactions after awakening operation between the two groups was statistically significant (P<0.05). The local pain rate in the observation group after the awakening operation was lower than the control group. The combined use of trace remifentanil and small dose propofol in the awakening painless digestive endoscopy can make the patients with colon cancer more stable when they are in the awakening state, so as to improve the safety of awakening painless digestive endoscopy. It is worth promoting in clinical practice.

Disrupted neural variability during propofol-induced sedation and unconsciousness

Variability quenching is a widespread neural phenomenon in which trial-to-trial variability (TTV) of neural activity is reduced by repeated presentations of a sensory stimulus. However, its neural mechanism and functional significance remain poorly understood. Recurrent network dynamics are suggested as a candidate mechanism of TTV, and they play a key role in consciousness. We thus asked whether the variability-quenching phenomenon is related to the level of consciousness. We hypothesized that TTV reduction would be compromised during reduced level of consciousness by propofol anesthetics. We recorded functional magnetic resonance imaging signals of resting-state and stimulus-induced activities in three conditions: wakefulness, sedation, and unconsciousness (i.e., deep anesthesia). We measured the average (trial-to-trial mean, TTM) and variability (TTV) of auditory stimulus-induced activity under the three conditions. We also examined another form of neural variability (temporal variability, TV), which quantifies the overall dynamic range of ongoing neural activity across time, during both the resting-state and the task. We found that (a) TTM deceased gradually from wakefulness through sedation to anesthesia, (b) stimulus-induced TTV reduction normally seen during wakefulness was abolished during both sedation and anesthesia, and (c) TV increased in the task state as compared to resting-state during both wakefulness and sedation, but not anesthesia. Together, our results reveal distinct effects of propofol on the two forms of neural variability (TTV and TV). They imply that the anesthetic disrupts recurrent network dynamics, thus prevents the stabilization of cortical activity states. These findings shed new light on the temporal dynamics of neuronal variability and its alteration during anesthetic-induced unconsciousness.

Spoken words are processed during dexmedetomidine-induced unresponsiveness

BACKGROUND

Studying the effects of anaesthetic drugs on the processing of semantic stimuli could yield insights into how brain functions change in the transition from wakefulness to unresponsiveness. Here, we explored the N400 event-related potential during dexmedetomidine- and propofol-induced unresponsiveness.

METHODS

Forty-seven healthy subjects were randomised to receive either dexmedetomidine (n=23) or propofol (n=24) in this open-label parallel-group study. Loss of responsiveness was achieved by stepwise increments of pseudo-steady-state plasma concentrations, and presumed loss of consciousness was induced using 1.5 times the concentration required for loss of responsiveness. Pre-recorded spoken sentences ending either with an expected (congruous) or an unexpected (incongruous) word were presented during unresponsiveness. The resulting electroencephalogram data were analysed for the presence of the N400 component, and for the N400 effect defined as the difference between the N400 components elicited by congruous and incongruous stimuli, in the time window 300-600 ms post-stimulus. Recognition of the presented stimuli was tested after recovery of responsiveness.

RESULTS

The N400 effect was not observed during dexmedetomidine- or propofol-induced unresponsiveness. The N400 component, however, persisted during dexmedetomidine administration. The N400 component elicited by congruous stimuli during unresponsiveness in the dexmedetomidine group resembled the large component evoked by incongruous stimuli at the awake baseline. After recovery, no recognition of the stimuli heard during unresponsiveness occurred.

CONCLUSIONS

Dexmedetomidine and propofol disrupt the discrimination of congruous and incongruous spoken sentences, and recognition memory at loss of responsiveness. However, the processing of words is partially preserved during dexmedetomidine-induced unresponsiveness.

CLINICAL TRIAL REGISTRATION

NCT01889004.

A comparison of the use of propofol alone and propofol with midazolam for pediatric magnetic resonance imaging sedation - a retrospective cohort study

Background

Pediatric MRI sedation performed by a variety of specialists such as sedationists and anesthesiologists commonly uses propofol, which has similar effects to an ideal sedative agent for maintaining deep sedation. However, when propofol is used, adverse airway events are relatively more common than when using other sedative agents. The concomitant administration of midazolam and propofol can reduce the dose of propofol needed for adequate sedation and might also reduce the frequency of airway obstruction without affecting the patient’s recovery profile.

Methods

We reviewed the our hospital records of all pediatric MRI sedation patients aged 3 to 16 years who were sedated with either propofol alone or propofol with midazolam between December 2013 and June 2016.

Results

Eight hundred ninety-seven pediatric MRI sedation patients were included (n = 897). The frequency of airway intervention was 25/356 (7.0%) in Group P and 15/541 (2.8%) in Group PM (difference in proportions: 4.2%; 95% CI: 1.4–7.6%; p = 0.002). The mean (SD) time to awake was longer in Group PM compared to Group P [21.2 (5.6) minutes vs. 23.0 (7.1) minutes; mean difference, 1.8 min; 95% CI, 0.9–2.9; p < 0.001]. The mean (SD) time to discharge was longer in Group PM compared to Group P [34.5 (6.9) minutes vs. 38.6 (9.4) minutes; mean difference, 4.0 min; 95% CI, 3.0–5.1; p < 0.001].

Conclusions

The administration of a small dose of midazolam during pediatric MRI sedation using propofol can reduce the frequency of airway complications without prolonging the clinically significant recovery profile.