2023 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting: Carbohydrate-containing Clear Liquids with or without Protein, Chewing Gum, and Pediatric Fasting Duration-A Modular Update of the 2017 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting.

These practice guidelines are a modular update of the "Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: Application to healthy patients undergoing elective procedures." The guidance focuses on topics not addressed in the previous guideline: ingestion of carbohydrate-containing clear liquids with or without protein, chewing gum, and pediatric fasting duration.

Sevoflurane anaesthesia induces cognitive impairment in young mice through sequential tau phosphorylation.

BACKGROUND: The volatile anaesthetic sevoflurane induces time (single or multiple exposures)-dependent effects on tau phosphorylation and cognitive function in young mice. The underlying mechanism for this remains largely undetermined. METHODS: Mice received 3% sevoflurane for 0.5 h or 2 h daily for 3 days on postnatal day (P) 6, 9, and 12. Another group of mice received 3% sevoflurane for 0.5 h or 1.5 h (3 × 0.5) on P6. We investigated effects of sevoflurane anaesthesia on tau phosphorylation on P6 or P12 mice, on cognitive function from P31 to P37, and on protein interactions, using in vivo studies, in vitro phosphorylation assays, and nanobeam single-molecule level interactions in vitro. RESULTS: An initial sevoflurane exposure induced CaMKIIα phosphorylation (132 [11]% vs 100 [6]%, P<0.01), leading to tau phosphorylation at serine 262 (164 [7]% vs 100 [26]%, P<0.01) and tau detachment from microtubules. Subsequent exposures to the sevoflurane induced GSK3ß activation, which phosphorylated detached or free tau (tau phosphorylated at serine 262) at serine 202 and threonine 205, resulting in cognitive impairment in young mice. In vitro phosphorylation assays also demonstrated sequential tau phosphorylation. Nanobeam analysis of molecular interactions showed different interactions between tau or free tau and CaMKIIα or GSK3ß, and between tau and tubulin at a single-molecule level. CONCLUSIONS: Multiple exposures to sevoflurane can induce sequential tau phosphorylation, leading to cognitive impairment in young mice, highlighting the need to investigate the underlying mechanisms of anaesthesia-induced tau phosphorylation in developing brain.

Mechanistic consideration of the effect of perioperative volatile anesthetics on phagocytes.

A growing literature has shown that volatile anesthetics are promiscuous molecules targeting multiple molecules, some of which are critical for immunological functions. We focused on studies that delineated target molecules of volatile anesthetics on immune cells and summarized the effects of volatile anesthetics on immune functions. We also presented the perspectives of studying volatile anesthetics-mediated immunomodulation.

Anesthetics isoflurane and sevoflurane attenuate flagellin-mediated inflammation in the lung.

Isoflurane and sevoflurane are volatile anesthetics (VA) widely used in clinical practice to provide general anesthesia. We and others have previously shown that VAs have immunomodulatory effects and may have a significant impact on the progression of disease states. Flagellin is a component of Gram negative bacteria and plays a significant role in the pathophysiology of bacterial pneumonia through its binding to Toll-like Receptor 5 (TLR5). Our results showed that VAs, not an intravenous anesthetic, significantly attenuated the activation of TLR5 and the release of the neutrophil chemoattractant IL-8 from lung epithelial cells. Furthermore, flagellin-induced lung injury was significantly attenuated by VAs by inhibiting neutrophil migration to the bronchoalveolar space. The lungs of cystic fibrosis (CF) patients are highly colonized by Pseudomonas aeruginosa, which causes inflammation. The retrospective study of oxygenation in patients with CF who had received VA versus intravenous anesthesia suggested that VAs might have the protective effect for gas exchange. To understand the interaction between VAs and TLR5, a docking simulation was performed, which indicated that isoflurane and sevoflurane docked into the binding interphase between TLR5 and flagellin.

Testosterone attenuates sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice.

BACKGROUND: Sevoflurane anaesthesia induces phosphorylation of the microtubule-associated protein tau and cognitive impairment in neonatal, but not adult, mice. The underlying mechanisms remain largely to be determined. Sex hormones can be neuroprotective, but little is known about the influence of testosterone on age-dependent anaesthesia effects. METHODS: Six- and 60-day-old male mice received anaesthesia with sevoflurane 3% for 2 h daily for 3 days. Morris water maze, immunoassay, immunoblotting, co-immunoprecipitation, nanobeam technology, and electrophysiology were used to assess cognition; testosterone concentrations; tau phosphorylation; glycogen synthase kinase-3ß (GSK3ß) activation; binding or interaction between tau and GSK3ß; and neuronal activation in mice, cells, and neurones. RESULTS: Compared with 60-day-old male mice, 6-day-old male mice had lower testosterone concentrations (3.03 [0.29] vs 0.44 [0.12] ng ml-1; P<0.01), higher sevoflurane-induced tau phosphorylation in brain (133 [20]% vs 100 [6]% in 6-day-old mice, P<0.01; 103 [8]% vs 100 [13]% in 60-day-old mice, P=0.77), and sevoflurane-induced cognitive impairment. Testosterone treatment increased brain testosterone concentrations (1.76 [0.10] vs 0.39 [0.05] ng ml-1; P<0.01) and attenuated the sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice. Testosterone inhibited the interaction between tau and GSK3ß, and attenuated sevoflurane-induced inhibition of excitatory postsynaptic currents in hippocampal neurones. CONCLUSIONS: Lower brain testosterone concentrations in neonatal compared with adult male mice contributed to age-dependent tau phosphorylation and cognitive impairment after sevoflurane anaesthesia. Testosterone might attenuate the sevoflurane-induced tau phosphorylation and cognitive impairment by inhibiting the interaction between tau and GSK3ß.

Dexmedetomidine and Clonidine Attenuate Sevoflurane-Induced Tau Phosphorylation and Cognitive Impairment in Young Mice via α-2 Adrenergic Receptor.

BACKGROUND: Anesthetic sevoflurane induces tau phosphorylation and cognitive impairment in young mice. The underlying mechanism and the targeted interventions remain largely unexplored. We hypothesized that dexmedetomidine and clonidine attenuated sevoflurane-induced tau phosphorylation and cognitive impairment by acting on α-2 adrenergic receptor. METHODS: Six-day-old mice received anesthesia with 3% sevoflurane 2 hours daily on postnatal days 6, 9, and 12. Alpha-2 adrenergic receptor agonist dexmedetomidine and clonidine were used to treat the mice with and without the α-2 adrenergic receptor antagonist yohimbine. Mouse hippocampi were harvested and subjected to western blot analysis. The New Object Recognition Test and Morris Water Maze were used to measure cognitive function. We analyzed the primary outcomes by using 2- and 1-way analysis of variance (ANOVA) and Mann-Whitney U test to determine the effects of sevoflurane on the amounts of phosphorylated tau, postsynaptic density-95, and cognitive function in young mice after the treatments with dexmedetomidine, clonidine, and yohimbine. RESULTS: Both dexmedetomidine and clonidine attenuated the sevoflurane-induced increase in phosphorylated tau amount (94 ± 16.3% [dexmedetomidine plus sevoflurane] versus 240 ± 67.8% [vehicle plus sevoflurane], P < .001; 125 ± 13.5% [clonidine plus sevoflurane] versus 355 ± 57.6% [vehicle plus sevoflurane], P < .001; mean ± standard deviation), sevoflurane-induced reduction in postsynaptic density-95 (82 ± 6.6% [dexmedetomidine plus sevoflurane] versus 31 ± 12.4% [vehicle plus sevoflurane], P < .001; 95 ± 6.4% [clonidine plus sevoflurane] versus 62 ± 18.4% [vehicle plus sevoflurane], P < .001), and cognitive impairment in the young mice. Interestingly, yohimbine reversed the effects of dexmedetomidine and clonidine on attenuating the sevoflurane-induced changes in phosphorylated tau, postsynaptic density-95, and cognitive function. CONCLUSIONS: Dexmedetomidine and clonidine could inhibit the sevoflurane-induced tau phosphorylation and cognitive impairment via activation of α-2 adrenergic receptor. More studies are needed to confirm the results and to determine the clinical relevance of these findings.

Vaping and E-Cigarette Use in Children and Adolescents: Implications on Perioperative Care From the American Society of Anesthesiologists Committee on Pediatric Anesthesia, Society for Pediatric Anesthesia, and American Academy of Pediatrics Section on Anesthesiology and Pain Medicine.

Electronic cigarettes (e-cigarettes) or vaping use in adolescents has emerged as a public health crisis that impacts the perioperative care of this vulnerable population. E-cigarettes have become the most commonly used tobacco products among youth in the United States. Fruit and mint flavors and additives such as marijuana have enticed children and adolescents. E-cigarette, or vaping, product use-associated lung injury (EVALI) is a newly identified lung disease linked to vaping. Clinical presentation of EVALI can be varied, but most commonly includes the respiratory system, gastrointestinal (GI) tract, and constitutional symptoms. Clinical management of EVALI has consisted of vaping cessation and supportive therapy, including supplemental oxygen, noninvasive ventilation, mechanical ventilation, glucocorticoids, and empiric antibiotics, until infectious causes are eliminated, and in the most severe cases, extracorporeal membrane oxygenation (ECMO). Currently, although there is an insufficient evidence to determine the safety and the efficacy of e-cigarettes for perioperative smoking cessation, EVALI clearly places these patients at an increased risk of perioperative morbidity. Given the relatively recent introduction of e-cigarettes, the long-term impact on adolescent health is unknown. As a result, the paucity of postoperative outcomes in this potentially vulnerable population does not support evidence-based recommendations for the management of these patients. Clinicians should identify "at-risk" individuals during preanesthetic evaluations and adjust the risk stratification accordingly. Our societies encourage continued education of the public and health care providers of the risks associated with vaping and nicotine use and encourage regular preoperative screening and postoperative outcome studies of patients with regard to smoking and vaping use.

Risk factors for pediatric surgical site infection following neurosurgical procedures for hydrocephalus: a retrospective single-center cohort study.

BACKGROUND: Infection is a major complication following cerebral spinal fluid (CSF) diversion procedures for hydrocephalus. However, pediatric risk factors for surgical site infection (SSI) are currently not well defined. Because a SSI prevention bundle is increasingly introduced, the purpose of this study was to evaluate risk factors associated with SSIs following CSF diversion surgeries following a SSI bundle at a single quaternary care pediatric hospital. METHODS: We performed a retrospective cohort study of patients undergoing CSF diversion procedures from 2017 to 2019. SSIs were identified prospectively through continuous surveillance. We performed unadjusted logistic regression analyses and univariate analyses to determine an association between SSIs and patient demographics, comorbidities and perioperative factors to identify independent risk factors for SSI. RESULTS: We identified a total of 558 CSF diversion procedures with an overall SSI rate of 3.4%. The SSI rates for shunt, external ventricular drain (EVD) placement, and endoscopic third ventriculostomy (ETV) were 4.3, 6.9 and 0%, respectively. Among 323 shunt operations, receipt of clindamycin as perioperative prophylaxis and presence of cardiac disease were significantly associated with SSI (O.R. 4.99, 95% C.I. 1.27-19.70, p = 0.02 for the former, and O.R. 7.19, 95% C.I. 1.35-38.35, p = 0.02 for the latter). No risk factors for SSI were identified among 72 EVD procedures. CONCLUSION: We identified receipt of clindamycin as perioperative prophylaxis and the presence of cardiac disease as risk factors for SSI in shunt procedures. Cefazolin is recommended as a standard antibiotic for perioperative prophylaxis. Knowing that unsubstantiated beta-lactam allergy label is a significant medical problem, efforts should be made to clarify beta-lactam allergy status to maximize the number of patients who can receive cefazolin for prophylaxis before shunt placement. Further research is needed to elucidate the mechanism by which cardiac disease may increase SSI risk after shunt procedures.

Neurodevelopmental outcome at 5 years of age after general anaesthesia or awake-regional anaesthesia in infancy (GAS): an international, multicentre, randomised, controlled equivalence trial.

BACKGROUND: In laboratory animals, exposure to most general anaesthetics leads to neurotoxicity manifested by neuronal cell death and abnormal behaviour and cognition. Some large human cohort studies have shown an association between general anaesthesia at a young age and subsequent neurodevelopmental deficits, but these studies are prone to bias. Others have found no evidence for an association. We aimed to establish whether general anaesthesia in early infancy affects neurodevelopmental outcomes. METHODS: In this international, assessor-masked, equivalence, randomised, controlled trial conducted at 28 hospitals in Australia, Italy, the USA, the UK, Canada, the Netherlands, and New Zealand, we recruited infants of less than 60 weeks' postmenstrual age who were born at more than 26 weeks' gestation and were undergoing inguinal herniorrhaphy, without previous exposure to general anaesthesia or risk factors for neurological injury. Patients were randomly assigned (1:1) by use of a web-based randomisation service to receive either awake-regional anaesthetic or sevoflurane-based general anaesthetic. Anaesthetists were aware of group allocation, but individuals administering the neurodevelopmental assessments were not. Parents were informed of their infants group allocation upon request, but were told to mask this information from assessors. The primary outcome measure was full-scale intelligence quotient (FSIQ) on the Wechsler Preschool and Primary Scale of Intelligence, third edition (WPPSI-III), at 5 years of age. The primary analysis was done on a per-protocol basis, adjusted for gestational age at birth and country, with multiple imputation used to account for missing data. An intention-to-treat analysis was also done. A difference in means of 5 points was predefined as the clinical equivalence margin. This completed trial is registered with ANZCTR, number ACTRN12606000441516, and ClinicalTrials.gov, number NCT00756600. FINDINGS: Between Feb 9, 2007, and Jan 31, 2013, 4023 infants were screened and 722 were randomly allocated: 363 (50%) to the awake-regional anaesthesia group and 359 (50%) to the general anaesthesia group. There were 74 protocol violations in the awake-regional anaesthesia group and two in the general anaesthesia group. Primary outcome data for the per-protocol analysis were obtained from 205 children in the awake-regional anaesthesia group and 242 in the general anaesthesia group. The median duration of general anaesthesia was 54 min (IQR 41-70). The mean FSIQ score was 99·08 (SD 18·35) in the awake-regional anaesthesia group and 98·97 (19·66) in the general anaesthesia group, with a difference in means (awake-regional anaesthesia minus general anaesthesia) of 0·23 (95% CI -2·59 to 3·06), providing strong evidence of equivalence. The results of the intention-to-treat analysis were similar to those of the per-protocol analysis. INTERPRETATION: Slightly less than 1 h of general anaesthesia in early infancy does not alter neurodevelopmental outcome at age 5 years compared with awake-regional anaesthesia in a predominantly male study population. FUNDING: US National Institutes of Health, US Food and Drug Administration, Thrasher Research Fund, Australian National Health and Medical Research Council, Health Technologies Assessment-National Institute for Health Research (UK), Australian and New Zealand College of Anaesthetists, Murdoch Children's Research Institute, Canadian Institutes of Health Research, Canadian Anesthesiologists Society, Pfizer Canada, Italian Ministry of Health, Fonds NutsOhra, UK Clinical Research Network, Perth Children's Hospital Foundation, the Stan Perron Charitable Trust, and the Callahan Estate.

The volatile anesthetic sevoflurane reduces neutrophil apoptosis via Fas death domain-Fas-associated death domain interaction.

Sepsis remains a significant health care burden, with high morbidities and mortalities. Patients with sepsis often require general anesthesia for procedures and imaging studies. Knowing that anesthetic drugs can pose immunomodulatory effects, it would be critical to understand the impact of anesthetics on sepsis pathophysiology. The volatile anesthetic sevoflurane is a common general anesthetic derived from ether as a prototype. Using a murine sepsis model induced by cecal ligation and puncture surgery, we examined the impact of sevoflurane on sepsis outcome. Different from volatile anesthetic isoflurane, sevoflurane exposure significantly improved the outcome of septic mice. This was associated with less apoptosis in the spleen. Because splenic apoptosis was largely attributed to the apoptosis of neutrophils, we examined the effect of sevoflurane on FasL-induced neutrophil apoptosis. Sevoflurane exposure significantly attenuated apoptosis. Sevoflurane did not affect the binding of FasL to the extracellular domain of Fas receptor. Instead, in silico analysis suggested that sevoflurane would bind to the interphase between Fas death domain (DD) and Fas-associated DD (FADD). The effect of sevoflurane on Fas DD-FADD interaction was examined using fluorescence resonance energy transfer (FRET). Sevoflurane attenuated FRET efficiency, indicating that sevoflurane hindered the interaction between Fas DD and FADD. The predicted sevoflurane binding site is known to play a significant role in Fas DD-FADD interaction, supporting our in vitro and in vivo apoptosis results.-Koutsogiannaki, S., Hou, L., Babazada, H., Okuno, T., Blazon-Brown, N., Soriano, S. G., Yokomizo, T., Yuki, K. The volatile anesthetic sevoflurane reduces neutrophil apoptosis via Fas death domain-Fas-associated death domain interaction.

Anesthesia and the developing brain: A way forward for laboratory and clinical research.

All commonly used general anesthetics have been shown to cause neurotoxicity in animal models, including nonhuman primates. Opinion, however, remains divided over how cumulative evidence from preclinical and human studies in this field should be interpreted and its translation to current practices in pediatric anesthesia and surgery. A group of international experts in laboratory and clinical sciences recently convened in Genoa, Italy, to evaluate the current state of both laboratory and clinical research and discuss future directions for basic, translational, and clinical studies in this field. This paper describes those discussions and conclusions. A central goal identified was the importance of continuing to pursue laboratory research efforts to better understand the biological pathways underlying anesthesia neurotoxicity. The distinction between basic and translational experimental designs in this field was highlighted, and it was acknowledged that it will be important for future animal research to try to causally link structural changes with long-term cognitive abnormalities. While inherent limitations will continue to affect the ability of even large observational cohorts to determine if anesthesia impacts neurodevelopment or behavioral outcomes, the importance of conducting further large well-designed cohort studies was also emphasized. Adequately powered cohorts could clarify which populations are at increased risk, provide information on environmental and healthcare-related risk modifiers, and guide future interventional trials. If anesthetics cause structural or functional adverse neurological effects in young children, alternative or mitigating strategies need to be considered. While protective or mitigating strategies have been repeatedly studied in animals, there are currently no human data to support alternative anesthetic strategies in clinical practice. Lastly, it was noted that there is still considerable debate over the clinical relevance of anesthesia neurotoxicity, and the need to evaluate the impact of other aspects of perioperative care on neurodevelopment must also be considered.

Sevoflurane Acts on Ubiquitination-Proteasome Pathway to Reduce Postsynaptic Density 95 Protein Levels in Young Mice.

BACKGROUND: Children with multiple exposures to anesthesia and surgery may have an increased risk of developing cognitive impairment. Sevoflurane, a commonly used anesthetic in children, has been reported to decrease levels of postsynaptic density 95 protein. However, the upstream mechanisms and downstream consequences of the sevoflurane-induced reduction in postsynaptic density 95 protein levels remains largely unknown. We therefore set out to assess whether sevoflurane acts on ubiquitination-proteasome pathway to facilitate postsynaptic density 95 protein degradation. METHODS: Six-day-old wild-type mice received anesthesia with 3% sevoflurane 2 h daily for 3 days starting on postnatal day 6. We determined the effects of the sevoflurane anesthesia on mRNA, protein and ubiquitinated levels of postsynaptic density 95 protein in neurons, and synaptosomes and hippocampus of young mice. Cognitive function in the mice was determined at postnatal day 31 by using a Morris water maze. Proteasome inhibitor MG132 and E3 ligase mouse double mutant 2 homolog inhibitor Nutlin-3 were used for the interaction studies. RESULTS: The sevoflurane anesthesia decreased protein, but not mRNA, levels of postsynaptic density 95, and reduced ubiquitinated postsynaptic density 95 protein levels in neurons, synaptosomes, and hippocampus of young mice. Both MG132 and Nutlin-3 blocked these sevoflurane-induced effects. Sevoflurane promoted the interaction of mouse double mutant 2 homolog and postsynaptic density 95 protein in neurons. Finally, MG132 and Nutlin-3 ameliorated the sevoflurane-induced cognitive impairment in the mice. CONCLUSIONS: These data suggest that sevoflurane acts on the ubiquitination-proteasome pathway to facilitate postsynaptic density 95 protein degradation, which then decreases postsynaptic density 95 protein levels, leading to cognitive impairment in young mice. These studies would further promote the mechanistic investigation of anesthesia neurotoxicity in the developing brain.

Dexmedetomidine-Induced Neuroapoptosis Is Dependent on Its Cumulative Dose.

BACKGROUND: Dexmedetomidine (DEX) has inherent neuroprotective properties that have been attributed to the activation of prosurvival kinases. However, the impact of supraclinical doses of DEX on neuroapoptosis and neuronal viability has not been determined. METHODS: Rat pups and primary neuronal cells were treated with DEX or ketamine (KET) alone or in combination. Neuroapoptosis was measured by cleaved-caspase-3 expression and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining in brain sections. Expression of prosurvival kinases was measured by Western blot. We measured the impact of DEX with and without α1-adrenergic receptor blockade on the viability of primary neuronal cell cultures. RESULTS: Increasing the cumulative dose of DEX resulted in elevated levels of neuroapoptosis in vivo. Low doses increased, whereas high dose decreased phosphorylation of the prosurvival kinases. KET alone and in combination with DEX produced a greater degree of apoptosis and reductions in expression of these protein kinases than DEX alone. Increasing concentrations of DEX decreased, while coadministration of an α1-adrenergic receptor blocker preserved neuronal viability in vitro. CONCLUSIONS: Although DEX is neuroprotective at clinical doses, high cumulative doses and concentrations induce neuroapoptosis, in vivo and in vitro, respectively. Because the current dosing schedules used in humans yield plasma levels that are substantially below concentrations that induce neurotoxicity, low-dose DEX should not be neurotoxic and has the potential to be a neuroprotective adjuvant.

Anesthesia for intracranial surgery in infants and children.

PURPOSE OF REVIEW: Age-related differences in the surgical lesions, anatomy and physiological responses to surgery and anesthesia underlie the clinically relevant differences between pediatric patients and their adult counterparts. Anesthesiologists need to be aware of the unique challenges in the anesthetic management of the pediatric neurosurgical patient. RECENT FINDINGS: Neurosurgeons with subspecialty training in pediatrics have driven advances in intracranial surgery in infants and children. Subspecialization in pediatric neurosurgery and critical care has resulted in more favorable outcomes. Innovations in tumor, epilepsy and endoscopic and cerebrovascular neurosurgery are constantly being adapted to the pediatric patient. The highly specialized nature of these and other pediatric neurosurgical procedures prompt calls for similarly trained anesthesiologists for management of these infants and children. SUMMARY: The aim of this review is to highlight the impact of these techniques on the intraoperative management of the pediatric neurosurgical patient. These issues are essential in minimizing perioperative morbidity and mortality.

Ketamine modulates disrupted in schizophrenia-1/glycogen synthase kinase-3ß interaction.

Introduction: Disrupted in schizophrenia-1 (DISC1) is a scaffolding protein whose mutated form has been linked to schizophrenia, bipolar affective disorders, and recurrent major depression. DISC1 regulates multiple signaling pathways involved in neurite outgrowth and cortical development and binds directly to glycogen synthase kinase-3ß (GSK-3ß). Since ketamine activates GSK-3ß, we examined the impact of ketamine on DISC1 and GSK-3ß expression. Methods: Postnatal day 7 rat pups were treated with ketamine with and without the non-specific GSK-3ß antagonist, lithium. Cleaved-caspase-3, GSK-3ß and DISC1 levels were measured by immunoblots and DISC1 co-localization in neurons by immunofluorescence. Binding of DISC1 to GSK-3ß was determined by co-immunoprecipitation. Neurite outgrowth was determined by measuring dendrite and axon length in primary neuronal cell cultures treated with ketamine and lithium. Results: Ketamine decreased DISC1 in a dose and time-dependent manner. This corresponded to decreases in phosphorylated GSK-3ß, which implicates increased GSK-3ß activity. Lithium significantly attenuated ketamine-induced decrease in DISC1 levels. Ketamine decreased co-immunoprecipitation of DISC1 with GSK-3ß and axonal length. Conclusion: These findings confirmed that acute administration of ketamine decreases in DISC1 levels and axonal growth. Lithium reversed this effect. This interaction provides a link between DISC1 and ketamine-induced neurodegeneration.

Dexmedetomidine directly binds to and inhibits Toll-like receptor 4.

BACKGROUND: While a number of anesthetics has been shown potentially associated with neurotoxicity in the developing brain, dexmedetomidine, a drug that was rather recently introduced into the perioperative setting, is considered beneficial from neurological wellbeing. However, the underlying mechanism of how dexmedetomidine affects brain health remains to be determined. Based on our recent study, we hypothesized that dexmedetomidine would directly bind to and inhibit Toll-like receptor 4 (TLR4), a critical receptor largely expressed in microglia and responsible for neurological insult. METHODS: We used TLR4 reporter assays to test if dexmedetomidine attenuates TLR4 activation. Furthermore, a direct binding of dexmedetomidine on TLR4 was tested using photoactivatable medetomidine. Lastly, the effect of dexmedetomidine on ketamine (anesthetic)-induced neurotoxicity was tested in rat pups (P7). RESULTS: We showed that dexmedetomidine attenuated TLR4 activation using reporter assay (IC50 = 5.8 µg/mL). Photoactivatable dexmedetomidine delineated its direct binding sites on TLR4. We also showed that dexmedetomidine attenuated microglia activation both in vitro and in vivo. DISCUSSION: We proposed a novel mechanism of dexmedetomidine-mediated neuroprotection.