Possible role of GABAergic depolarization in neocortical neurons in generating hyperexcitatory behaviors during emergence from sevoflurane anesthesia in the rat

Research trends related to emergence agitation in the post-anaesthesia care unit from 2001 to 2023: A bibliometric analysis

Background

Emergence agitation (EA) is a behavioural disturbance encountered during the recovery phase of patients following general anaesthesia. It is characterised by restlessness, involuntary limb movements, and drainage tube withdrawal and may significantly harm patients and medical staff. The mechanism of EA has not been fully understood and is still a challenging subject for researchers.

Methods

We extracted relevant publications published between 1 January 2001 and 31 December 2023 on the Web of Science Core Collection platform. VOSviewer software was utilised to analyse the retrieved literature and predict the development trends and hotspots in the field.

Results

The results show that the number of publications grew annually, with China contributing the most, followed by the United States and South Korea. The co-occurrence of keywords "children," "propofol," "risk factors" are current research hotspots. Owing to its self-limiting and short-duration characteristics, EA lacks standardised clinical time guidelines and objective assessment tools, which may be the focus of future research in this field.

Conclusions

Understanding the research hotspots and the latest progress in this field, this study will help to continuously improve the clinical understanding and management of EA, and help to timely identify environmental risk factors for EA in clinical practice.

Possible role of high calcium concentrations in rat neocortical neurons in inducing hyper excitatory behavior during emergence from sevoflurane: a proposed pathophysiology

Sevoflurane has been shown to increase the incidence of emergence delirium in children; however, the mechanism remains unclear. Sevoflurane increases cytoplasmic calcium concentration which in turn may play a role in emergence delirium. This study aimed to investigate the level of intracellular calcium in rats experiencing hyperexcitatory behavior after exposure to sevoflurane, as well as the role of magnesium in preventing this phenomenon. After ethical approval, 2-5-week-old Sprague-Dawley rats (n = 34) were insufflated with sevoflurane in a modified anesthesia chamber. One group received magnesium sulphate intraperitoneally. After termination of sevoflurane exposure, the occurrence of hyperexcitation was observed. Brain tissue samples from the rats were studied for intracellular calcium levels under a two-channel laser scanning confocal microscope and were quantitatively calculated using ratiometric calculation. The presence of inflammation or oxidative stress reaction was assessed using nuclear factor κB and malondialdehyde. The incidence of hyperexcitatory behavior post sevoflurane exposure was 9 in 16 rats in the observation group and none in the magnesium group. Tests for inflammation and oxidative stress were within normal limits in both groups. The rats showing hyperexcitation had a higher level of cytosol calcium concentration compared to the other groups. To conclude, the calcium concentration of neocortical neurons in Sprague-Dawley rats with hyperexcitatory behavior is increased after exposure to sevoflurane. Administration of magnesium sulphate can prevent the occurrence of hyperexcitation in experimental animals.

Perioperative complications of middle cerebral artery occlusion in rats alleviated by human umbilical cord mesenchymal stem cells

For acute ischemic stroke treatment, the limitations of treatment methods and the high incidence of perioperative complications seriously affect the survival rate and postoperative recovery of patients. Human umbilical cord mesenchymal stem cells (hucMSCs) have multi-directional differentiation potential and immune regulation function, which is a potential cell therapy. The present investigation involved developing a model of cerebral ischemia-reperfusion injury by thrombectomy after middle cerebral artery occlusion (MCAO) for 90 min in rats and utilizing comprehensive multi-system evaluation methods, including the detection of brain tissue ischemia, postoperative survival rate, neurological score, anesthesia recovery monitoring, pain evaluation, stress response, and postoperative pulmonary complications, to elucidate the curative effect of tail vein injection of hucMSCs on MCAO's perioperative complications. Based on our research, it has been determined that hucMSCs treatment can reduce the volume of brain tissue ischemia, promote the recovery of neurological function, and improve the postoperative survival rate of MCAO in rats. At the same time, hucMSCs treatment can prolong the time of anesthesia recovery, relieve the occurrence of delirium during anesthesia recovery, and also have a good control effect on postoperative weight loss, facial pain expression, and lung injury. It can also reduce postoperative stress response by regulating blood glucose and serum levels of stress-related proteins including TNF-α, IL-6, CRP, NE, cortisol, β-endorphin, and IL-10, and ultimately promote the recovery of MCAO's perioperative complications.

γ-Aminobutyric Acid-Ergic Development Contributes to the Enhancement of Electroencephalogram Slow-Delta Oscillations Under Volatile Anesthesia in Neonatal Rats

BACKGROUND

General anesthetics (eg, propofol and volatile anesthetics) enhance the slow-delta oscillations of the cortical electroencephalogram (EEG), which partly results from the enhancement of (γ-aminobutyric acid [GABA]) γ-aminobutyric acid-ergic (GABAergic) transmission. There is a GABAergic excitatory-inhibitory shift during postnatal development. Whether general anesthetics can enhance slow-delta oscillations in the immature brain has not yet been unequivocally determined.

METHODS

Perforated patch-clamp recording was used to confirm the reversal potential of GABAergic currents throughout GABAergic development in acute brain slices of neonatal rats. The power density of the electrocorticogram and the minimum alveolar concentrations (MAC) of isoflurane and/or sevoflurane were measured in P4-P21 rats. Then, the effects of bumetanide, an inhibitor of the Na + -K + -2Cl - cotransporter (NKCC1) and K + -Cl - cotransporter (KCC2) knockdown on the potency of volatile anesthetics and the power density of the EEG were determined in vivo.

RESULTS

Reversal potential of GABAergic currents were gradually hyperpolarized from P4 to P21 in cortical pyramidal neurons. Bumetanide enhanced the hypnotic effects of volatile anesthetics at P5 (for MAC LORR , isoflurane: 0.63% ± 0.07% vs 0.81% ± 0.05%, 95% confidence interval [CI], -0.257 to -0.103, P < .001; sevoflurane: 1.46% ± 0.12% vs 1.66% ± 0.09%, 95% CI, -0.319 to -0.081, P < .001); while knockdown of KCC2 weakened their hypnotic effects at P21 in rats (for MAC LORR , isoflurane: 0.58% ± 0.05% to 0.77% ± 0.20%, 95% CI, 0.013-0.357, P = .003; sevoflurane: 1.17% ± 0.04% to 1.33% ± 0.04%, 95% CI, 0.078-0.244, P < .001). For cortical EEG, slow-delta oscillations were the predominant components of the EEG spectrum in neonatal rats. Isoflurane and/or sevoflurane suppressed the power density of slow-delta oscillations rather than enhancement of it until GABAergic maturity. Enhancement of slow-delta oscillations under volatile anesthetics was simulated by preinjection of bumetanide at P5 (isoflurane: slow-delta changed ratio from -0.31 ± 0.22 to 1.57 ± 1.15, 95% CI, 0.67-3.08, P = .007; sevoflurane: slow-delta changed ratio from -0.46 ± 0.25 to 0.95 ± 0.97, 95% CI, 0.38-2.45, P = .014); and suppressed by KCC2-siRNA at P21 (isoflurane: slow-delta changed ratio from 16.13 ± 5.69 to 3.98 ± 2.35, 95% CI, -18.50 to -5.80, P = .002; sevoflurane: slow-delta changed ratio from 0.13 ± 2.82 to 3.23 ± 2.49, 95% CI, 3.02-10.79, P = .003).

CONCLUSIONS

Enhancement of cortical EEG slow-delta oscillations by volatile anesthetics may require mature GABAergic inhibitory transmission during neonatal development.

Tau protein plays a role in the mechanism of cognitive disorders induced by anesthetic drugs

Cognitive disorders are mental health disorders that can affect cognitive ability. Surgery and anesthesia have been proposed to increase the incidence of cognitive dysfunction, including declines in memory, learning, attention and executive function. Tau protein is a microtubule-associated protein located in the axons of neurons and is important for microtubule assembly and stability; its biological function is mainly regulated by phosphorylation. Phosphorylated tau protein has been associated with cognitive dysfunction mediated by disrupting the stability of the microtubule structure. There is an increasing consensus that anesthetic drugs can cause cognitive impairment. Herein, we reviewed the latest literature and compared the relationship between tau protein and cognitive impairment caused by different anesthetics. Our results substantiated that tau protein phosphorylation is essential in cognitive dysfunction caused by anesthetic drugs, and the possible mechanism can be summarized as "anesthetic drugs-kinase/phosphatase-p-Tau-cognitive impairment".

Prolonged sevoflurane exposure causes abnormal synapse development and dysregulates beta-neurexin and neuroligins in the hippocampus in neonatal rats

BACKGROUND

The underlying molecular mechanisms of the excitatory/inhibitory (E/I) imbalance induced by sevoflurane exposure to neonates remain poorly understood. This study aimed to investigate the long-term effects of prolonged sevoflurane exposure to neonatal rats during the peak period of synaptogenesis on the changes of trans-synaptic neurexin-neuroligin interactions, synaptic ultrastructure in the hippocampus and cognition.

METHODS

A total of 30 rat pups at postnatal day (P) 7 was randomly divided into two groups: the control group (exposed to 30 % oxygen balanced with nitrogen) and the sevoflurane group (exposed to 2.5 % sevoflurane plus 30 % oxygen balanced with nitrogen) for 6 h. Neurocognitive behaviors were assessed with the Open field test at P23-25 and the Morris water maze test at P26-30. The expression of β-neurexin (β-NRX), N-methyl-d-aspartate receptor 2 subunit (NR2A and NR2B), neuroligin-1 (NLG-1), neuroligin-2 (NLG-2), postsynaptic density protein-95 (PSD-95), α1-subunit of the γ-aminobutyric acid A receptor (GABAAα1) and gephyrin in the hippocampus at P30 were measured by Western blot. The ultrastructure of synapses was examined under electron microscope.

RESULTS

Prolonged sevoflurane exposure at P7 resulted in cognitive deficiency in adolescence, as well as the downregulation of β-NRX, NR2A, NR2B, NLG-1, and PSD-95, and the upregulation of GABAAα1, NLG-2, and gephyrin in the hippocampal CA3 region. Sevoflurane anesthesia also increased the number of symmetric synapses in the hippocampus.

CONCLUSIONS

Prolonged sevoflurane exposure during the brain development leads to cognitive deficiency and disproportion of excitatory/inhibitory synapses which may be caused by dysregulated expression of synaptic adhesion molecules of β-NRX and neuroligins.

Update on the Mechanism and Treatment of Sevoflurane-Induced Postoperative Cognitive Dysfunction

Sevoflurane is one of the most widely used anesthetics for the induction and maintenance of general anesthesia in surgical patients. Sevoflurane treatment may increase the incidence of postoperative cognitive dysfunction (POCD), and patients with POCD exhibit lower cognitive abilities than before the operation. POCD affects the lives of patients and places an additional burden on patients and their families. Understanding the mechanism of sevoflurane-induced POCD may improve prevention and treatment of POCD. In this paper, we review the diagnosis of POCD, introduce animal models of POCD in clinical research, analyze the possible mechanisms of sevoflurane-induced POCD, and summarize advances in treatment for this condition.

The effects of the general anesthetic sevoflurane on neurotransmission: an experimental and computational study

The brain functions can be reversibly modulated by the action of general anesthetics. Despite a wide number of pharmacological studies, an extensive analysis of the cellular determinants of anesthesia at the microcircuits level is still missing. Here, by combining patch-clamp recordings and mathematical modeling, we examined the impact of sevoflurane, a general anesthetic widely employed in the clinical practice, on neuronal communication. The cerebellar microcircuit was used as a benchmark to analyze the action mechanisms of sevoflurane while a biologically realistic mathematical model was employed to explore at fine grain the molecular targets of anesthetic analyzing its impact on neuronal activity. The sevoflurane altered neurotransmission by strongly increasing GABAergic inhibition while decreasing glutamatergic NMDA activity. These changes caused a notable reduction of spike discharge in cerebellar granule cells (GrCs) following repetitive activation by excitatory mossy fibers (mfs). Unexpectedly, sevoflurane altered GrCs intrinsic excitability promoting action potential generation. Computational modelling revealed that this effect was triggered by an acceleration of persistent sodium current kinetics and by an increase in voltage dependent potassium current conductance. The overall effect was a reduced variability of GrCs responses elicited by mfs supporting the idea that sevoflurane shapes neuronal communication without silencing neural circuits.

Role of the GABAA receptors in the long-term cognitive impairments caused by neonatal sevoflurane exposure

Sevoflurane is a widely used inhalational anesthetic in pediatric surgeries, which is considered reasonably safe and reversible upon withdrawal. However, recent preclinical studies suggested that peri-neonatal sevoflurane exposure may cause developmental abnormalities in the brain. The present review aimed to present and discuss the accumulating experimental data regarding the undesirable effects of sevoflurane on brain development as revealed by the laboratory studies. First, we summarized the long-lasting side effects of neonatal sevoflurane exposure on cognitive functions. Subsequently, we presented the structural changes, namely, neuroapoptosis, neurogenesis and synaptogenesis, following sevoflurane exposure in the immature brain. Finally, we also discussed the potential mechanisms underlying subsequent cognitive impairments later in life, which are induced by neonatal sevoflurane exposure and pointed out potential strategies for mitigating sevoflurane-induced long-term cognitive impairments. The type A gamma-amino butyric acid (GABAA) receptor, the main targets of sevoflurane, is excitatory rather than inhibitory in the immature neurons. The excitatory effects of the GABAA receptors have been linked to increased neuroapoptosis, elevated serum corticosterone levels and epigenetic modifications following neonatal sevoflurane exposure in rodents, which might contribute to sevoflurane-induced long-term cognitive abnormalities. We proposed that the excitatory GABAA receptor-mediated HPA axis activity might be a novel mechanism underlying sevoflurane-induced long-term cognitive impairments. More studies are needed to investigate the effectiveness and mechanisms by targeting the excitatory GABAA receptor as a prevention strategy to alleviate cognitive deficits induced by neonatal sevoflurane exposure in future.

Role of T-type Calcium Channels in Generating Hyperexcitatory Behaviors during Emergence from Sevoflurane Anesthesia in Neonatal Rats

In the current study, we sought to investigate whether T-type Ca²⁺ channels (TCCs) in the brain are involved in generating post-anesthetic hyperexcitatory behaviors (PAHBs). We found that younger rat pups (postnatal days 9-11) had a higher incidence of PAHBs and higher PAHB scores than older pups (postnatal days 16-18) during emergence from sevoflurane anesthesia. The power spectrum of the theta oscillations (4 Hz-8 Hz) in the prefrontal cortex was significantly enhanced in younger pups when PAHBs occurred, while there were no significant changes in older pups. Both the power of theta oscillations and the level of PAHBs were significantly reduced by the administration of TCC inhibitors. Moreover, the sensitivity of TCCs in the medial dorsal thalamic nucleus to sevoflurane was found to increase with age by investigating the kinetic properties of TCCs in vitro. TCCs were activated by potentiated GABAergic depolarization with a sub-anesthetic dose of sevoflurane (1%). These data suggest that (1) TCCs in the brain contribute to the generation of PAHBs and the concomitant electroencephalographic changes; (2) the stronger inhibitory effect of sevoflurane contributes to the lack of PAHBs in older rats; and (3) the contribution of TCCs to PAHBs is not mediated by a direct effect of sevoflurane on TCCs.

Oxytocin and Vasopressin, and the GABA Developmental Shift During Labor and Birth: Friends or Foes?

Oxytocin (OT) and vasopressin (AVP) are usually associated with sociability and reduced stress for the former and antidiuretic agent associated with severe stress and pathological conditions for the latter. Both OT and AVP play major roles during labor and birth. Recent contradictory studies suggest that they might exert different roles on the GABA excitatory/inhibitory developmental shift. We reported (Tyzio et al., 2006) that at birth, OT exerts a neuro-protective action mediated by an abrupt reduction of intracellular chloride levels ([Cl-]i) that are high in utero, reinforcing GABAergic inhibition and modulating the generation of the first synchronized patterns of cortical networks. This reduction of [Cl-]i levels is abolished in rodent models of Fragile X Syndrome and Autism Spectrum Disorders, and its restoration attenuates the severity of the pathological sequels, stressing the importance of the shift at birth (Tyzio et al., 2014). In contrast, Kaila and co-workers (Spoljaric et al., 2017) reported excitatory GABA actions before and after birth that are modulated by AVP but not by OT, challenging both the developmental shift and the roles of OT. Here, I analyze the differences between these studies and suggest that the ratio AVP/OT like that of excitatory/inhibitory GABA depend on stress and pathological conditions.

Prediction of emergence agitation using withdrawal reaction following rocuronium injection in preschool-aged patients undergoing inguinal herniorrhaphy: a preliminary exploratory observational trial

Purpose

The development of emergence agitation (EA) is associated with several factors including age, preoperative anxiety, postoperative pain, anesthesia method, and surgery type. No studies have investigated whether the withdrawal reaction following rocuronium injection can predict the occurrence of EA. Therefore, we investigated this relationship in preschool-aged children undergoing inguinal herniorrhaphy, and which grade of withdrawal reaction is appropriate for identifying patients at risk of experiencing EA.

Methods

A total of 40 patients were enrolled in this study. During anesthesia induction, the withdrawal reaction after loss of consciousness following rocuronium injection was assessed using a 4-point scale. After surgery, EA was assessed using the Watcha scale.

Results

There was a correlation between withdrawal reaction and EA on admission to the postanesthesia care unit (PACU). Patients with a severe withdrawal reaction (grade 3) showed a significantly higher incidence of severe EA requiring medication on admission to the PACU.

Conclusion

The findings of this preliminary exploratory observational study suggest that it is possible for withdrawal movement following rocuronium injection during anesthesia induction to reflect pain sensitivity of pediatric patients, which in turn may be useful in identifying those at risk of severe EA on admission to the PACU among preschool children undergoing inguinal herniorrhaphy. Further studies with a larger sample size are required to validate these findings. The exact correlation between pain reaction following rocuronium injection and postoperative pain or pain-related phenomenon should be elucidated.

Low-dose sevoflurane promotes hippocampal neurogenesis and facilitates the development of dentate gyrus-dependent learning in neonatal rats

Huge body of evidences demonstrated that volatile anesthetics affect the hippocampal neurogenesis and neurocognitive functions, and most of them showed impairment at anesthetic dose. Here, we investigated the effect of low dose (1.8%) sevoflurane on hippocampal neurogenesis and dentate gyrus-dependent learning. Neonatal rats at postnatal day 4 to 6 (P4–6) were treated with 1.8% sevoflurane for 6 hours. Neurogenesis was quantified by bromodeoxyuridine labeling and electrophysiology recording. Four and seven weeks after treatment, the Morris water maze and contextual-fear discrimination learning tests were performed to determine the influence on spatial learning and pattern separation. A 6-hour treatment with 1.8% sevoflurane promoted hippocampal neurogenesis and increased the survival of newborn cells and the proportion of immature granular cells in the dentate gyrus of neonatal rats. Sevoflurane-treated rats performed better during the training days of the Morris water maze test and in contextual-fear discrimination learning test. These results suggest that a subanesthetic dose of sevoflurane promotes hippocampal neurogenesis in neonatal rats and facilitates their performance in dentate gyrus-dependent learning tasks.

The effect of desflurane on neuronal communication at a central synapse

Although general anesthetics are thought to modify critical neuronal functions, their impact on neuronal communication has been poorly examined. We have investigated the effect induced by desflurane, a clinically used general anesthetic, on information transfer at the synapse between mossy fibers and granule cells of cerebellum, where this analysis can be carried out extensively. Mutual information values were assessed by measuring the variability of postsynaptic output in relationship to the variability of a given set of presynaptic inputs. Desflurane synchronized granule cell firing and reduced mutual information in response to physiologically relevant mossy fibers patterns. The decrease in spike variability was due to an increased postsynaptic membrane excitability, which made granule cells more prone to elicit action potentials, and to a strengthened synaptic inhibition, which markedly hampered membrane depolarization. These concomitant actions on granule cells firing indicate that desflurane re-shapes the transfer of information between neurons by providing a less informative neurotransmission rather than completely silencing neuronal activity.

Propofol-induced electroencephalographic seizures in neonatal rats: the role of corticosteroids and γ-aminobutyric acid type A receptor-mediated excitation

BACKGROUND

An imbalance between excitation and inhibition in the developing central nervous system may result in a pathophysiological outcome. We investigated the mechanistic roles of endocrine activity and γ-aminobutyric acid type A receptor (GABAAR)-mediated excitation in electroencephalographic seizures caused by the GABAAR-selective anesthetic propofol in neonatal rats.

METHODS

Postnatal day 4-6 Sprague Dawley rats underwent a minor surgical procedure to implant electrodes to measure electroencephalographic activity for 1 hour before and 1 hour after intraperitoneal administration of propofol (40 mg·kg). Various treatments were administered 15 minutes before administration of propofol.

RESULTS

Episodes of electroencephalographic seizures and persistent low-amplitude spikes occurred during propofol anesthesia. Multifold increases in serum levels of corticosterone (t(10) = -5.062; P = 0.0005) and aldosterone (t(10) = -5.069; P = 0.0005) were detected 1 hour after propofol administration in animals that underwent experimental manipulations identical to those used to study electroencephalographic activity. Pretreatment with bumetanide, the Na-K-2Cl cotransporter inhibitor, which diminishes GABAAR-mediated excitation, eliminated both seizure and spike electroencephalographic activities caused by propofol. Mineralocorticoid and glucocorticoid receptor antagonists, RU 28318 and RU486, depressed electroencephalographic seizures but did not affect the spike electroencephalographic effects of propofol. Etomidate, at a dose sufficient to induce loss of righting reflex, was weak at increasing serum corticosteroid levels and eliciting electroencephalographic seizures. Etomidate given to corticosterone-pretreated rat pups further increased the total duration of electroencephalographic seizures caused by administration of exogenous corticosterone (t(21) = -2.512, P = 0.0203).

CONCLUSIONS

Propofol increases systemic corticosteroid levels in neonatal rats, which along with GABAAR-mediated excitation appear to be required for propofol-induced neonatal electroencephalographic seizures. Enhancement of GABAAR activity alone may not be sufficient to elicit neonatal electroencephalographic seizures.