Dexmedetomidine Attenuates Neurotoxicity Induced by Prenatal Propofol Exposure

Unraveling the effects of prenatal anesthesia on neurodevelopment: A review of current evidence and future directions

Human brain development is a complex, multi-stage, and sensitive process, especially during the fetal stage. Animal studies over the last two decades have highlighted the potential risks of anesthetics to the developing brain, impacting its structure and function. This has raised concerns regarding the safety of anesthesia during pregnancy and its influence on fetal brain development, garnering significant attention from the anesthesiology community. Although preclinical studies predominantly indicate the neurotoxic effects of prenatal anesthesia, these findings cannot be directly extrapolated to humans due to interspecies variations. Clinical research, constrained by ethical and technical hurdles in accessing human prenatal brain tissues, often yields conflicting results compared to preclinical data. The emergence of brain organoids as a cutting-edge research tool shows promise in modeling human brain development. When integrated with single-cell sequencing, these organoids offer insights into potential neurotoxic mechanisms triggered by prenatal anesthesia. Despite several retrospective and cohort studies exploring the clinical impact of anesthesia on brain development, many findings remain inconclusive. As such, this review synthesizes preclinical and clinical evidence on the effects of prenatal anesthesia on fetal brain development and suggests areas for future research advancement.

Suberoylanilide hydroxamic acid attenuates cognitive impairment in offspring caused by maternal surgery during mid-pregnancy

Some pregnant women have to experience non-obstetric surgery during pregnancy under general anesthesia. Our previous studies showed that maternal exposure to sevoflurane, isoflurane, propofol, and ketamine causes cognitive deficits in offspring. Histone acetylation has been implicated in synaptic plasticity. Propofol is commonly used in non-obstetric procedures on pregnant women. Previous studies in our laboratory showed that maternal propofol exposure in pregnancy impairs learning and memory in offspring by disturbing histone acetylation. The present study aims to investigate whether HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) could attenuate learning and memory deficits in offspring caused by maternal surgery under propofol anesthesia during mid-pregnancy. Maternal rats were exposed to propofol or underwent abdominal surgery under propofol anesthesia during middle pregnancy. The learning and memory abilities of the offspring rats were assessed using the Morris water maze (MWM) test. The protein levels of histone deacetylase 2 (HDAC2), phosphorylated cAMP response-element binding (p-CREB), brain-derived neurotrophic factor (BDNF), and phosphorylated tyrosine kinase B (p-TrkB) in the hippocampus of the offspring rats were evaluated by immunofluorescence staining and western blot. Hippocampal neuroapoptosis was detected by TUNEL staining. Our results showed that maternal propofol exposure during middle pregnancy impaired the water-maze learning and memory of the offspring rats, increased the protein level of HDAC2 and reduced the protein levels of p-CREB, BDNF and p-TrkB in the hippocampus of the offspring, and such effects were exacerbated by surgery. SAHA alleviated the cognitive dysfunction and rescued the changes in the protein levels of p-CREB, BDNF and p-TrkB induced by maternal propofol exposure alone or maternal propofol exposure plus surgery. Therefore, SAHA could be a potential and promising agent for treating the learning and memory deficits in offspring caused by maternal nonobstetric surgery under propofol anesthesia.

A Scoping Review of the Mechanisms Underlying Developmental Anesthetic Neurotoxicity

Although anesthesia makes painful or uncomfortable diagnostic and interventional health care procedures tolerable, it may also disrupt key cellular processes in neurons and glia, harm the developing brain, and thereby impair cognition and behavior in children. Many years of studies using in vitro, animal behavioral, retrospective database studies in humans, and several prospective clinical trials in humans have been invaluable in discerning the potential toxicity of anesthetics. The objective of this scoping review was to synthetize the evidence from preclinical studies for various mechanisms of toxicity across diverse experimental designs and relate their findings to those of recent clinical trials in real-world settings.

Effects of dexmedetomidine at different dosages on perioperative haemodynamics and postoperative recovery quality in elderly patients undergoing hip replacement surgery under general anaesthesia: a randomized controlled trial

BACKGROUND

Dexmedetomidine could provide some advantages to prevent postoperative complications in elderly patients undergoing under general anaesthesia. However, dexmedetomidine inhibits haemodynamics to some extent due to its sympathetic inhibition.

OBJECTIVE

To evaluate the effects of different doses of dexmedetomidine on haemodynamics during surgery and recovery after general anaesthesia in elderly patients undergoing hip replacement.

METHODS

This was a prospective randomized double-blind controlled clinical trial. Eligible patients were randomly allocated into comparative groups (normal saline (NS) and midazolam (MD), n = 30) and dexmedetomidine groups at different doses (D0.25/D0.5/D0.75, n = 30). In the D0.25/D0.5/D0.75 groups, dexmedetomidine was administered at different initial loading doses (0.25/0.5/0.75 μg/kg for 15 min) following 0.5 μg/kg/h continuous infusion until the end of the operation. In the MD group, patients were administered 0.03 mg/kg midazolam at the beginning of anaesthesia induction.

RESULTS

Compared to the MD and NS groups, there were significant decreases in MAP in the D0.5 and D0.75 groups at many time points, such as skin incision, end of operation, and from extubation until 30 min after extubation (P < 0.05); there were also significant decreases in HR in the D0.5 and D0.75 groups at time points including anaesthesia induction, end of operation, and from extubation to 2 h after operation (P < 0.05). In the D0.25 group, there were few differences in the changes in MAP and HR compared to the MD and NS groups during the entire perioperative period (P > 0.05). Moreover, the percentage of patients whose MAP and HR decreased > 20% of baseline was higher in the D0.75 and D0.5 groups than that in all other groups. Compared to the NS group, from the beginning to the end of the operation, the 95% confidence interval (CI) of RR for MAP below > 20% of baseline in the D0.5 and D0.75 groups was greater than 1. In particular, the CI of the RR in the D0.75 group was greater than 1 until the patient awoke from general anaesthesia (P < 0.05). In addition, the CI of the RR for HR below > 20% of baseline in the D0.5 group was greater than 1 compared to the NS group at the time of induction and extubation (P < 0.05). There was no significant difference in the possibility of developing hypotension or bradycardia in the MD or D0.25 groups compared to the NS group (P > 0.05). The recovery quality of patients during the post-anaesthesia period was also observed. No differences were observed among all the groups in the time to awakening or extubation after general anaesthesia (P > 0.05). According to the Riker Sedation-agitated Scale, dexmedetomidine significantly alleviated emergency agitation or delirium compared to NS (P < 0.05). In addition, the scores in the D0.5 and D0.75 groups were lower than those in the D0.25 group (P < 0.05).

CONCLUSION

Dexmedetomidine could alleviate the agitation of elderly patients undergoing hip replacement after intravenous general anaesthesia combined with inhaled sevoflurane without delayed recovery. However, it is necessary to be vigilant about the haemodynamic inhibition of the drug at high dosages throughout the perioperative period. Dexmedetomidine 0.25-0.5 μg/kg as the initial loading dose followed by 0.5 μg/kg/h continuous infusion might provide comfortable recovery after general anaesthesia with slight haemodynamic inhibition.

TRAIL REGISTRATION

ClinicalTrial.gov, No. NCT05567523. Registered 05 October 2022, https://clinicaltrials.gov/ct2/show/NCT05567523?term=NCT05567523&draw=2&rank=1 .

Perioperative Maternal-Fetal Outcomes in the Setting of Minimally Invasive Fetal Therapy for Complex Monochorionic Pregnancies with Monitored Anesthesia Care

INTRODUCTION

Fetoscopic selective laser photocoagulation (FSLPC) and selective cord occlusion with radiofrequency ablation (RFA) can improve fetal outcomes when vascular anastomoses between fetuses cause twin-to-twin transfusion syndrome (TTTS) or selective fetal growth restriction (sFGR) in multiple gestation pregnancies with monochorionic placentation. This study analyzed perioperative maternal-fetal complications and anesthetic management in a high-volume fetal therapy center over a 4-year period.

METHODS

Included patients received MAC for minimally invasive fetal procedures for complex multiple gestation pregnancies between January 1, 2015, and September 20, 2019. Maternal and fetal complications, intraoperative maternal hemodynamics, medication usage, and reasons for conversion to general anesthesia, if applicable, were analyzed.

RESULTS

A total of 203 (59%) patients underwent FSLPC and 141 (41%) had RFA. Four patients (2%; rate 95% CI: 0.00039, 0.03901) undergoing FSLPC had conversion to general anesthesia. No conversions to general anesthesia occurred in the RFA group. The incidence of maternal complications was higher in those who underwent FSLPC. No aspiration or postoperative pneumonia events were observed. Medication usage was similar in FSLPC and RFA groups.

CONCLUSION

A low rate of conversion to general anesthesia and no serious adverse maternal events were observed in patients receiving MAC.

Effect of preconditioning on propofol-induced neurotoxicity during the developmental period

At therapeutic concentrations, propofol (PPF), an anesthetic agent, significantly elevates intracellular calcium concentration ([Ca2 +]i) and induces neural death during the developmental period. Preconditioning enables specialized tissues to tolerate major insults better compared with tissues that have already been exposed to sublethal insults. Here, we investigated whether the neurotoxicity induced by clinical concentrations of PPF could be alleviated by prior exposure to sublethal amounts of PPF. Cortical neurons from embryonic day (E) 17 Wistar rat fetuses were cultured in vitro, and on day in vitro (DIV) 2, the cells were preconditioned by exposure to PPF (PPF-PC) at either 100 nM or 1 μM for 24 h. For morphological observations, cells were exposed to clinical concentrations of PPF (10 μM or 100 μM) for 24 h and the survival ratio (SR) was calculated. Calcium imaging revealed significant PPF-induced [Ca2+]i elevation in cells on DIV 4 regardless of PPF-PC. Additionally, PPF-PC did not alleviate neural cell death induced by PPF under any condition. Our findings indicate that PPF-PC does not alleviate PPF-induced neurotoxicity during the developmental period.

Dexmedetomidine attenuates propofol-induced apoptosis of neonatal hippocampal astrocytes by inhibiting the Bcl2l1 signalling pathway

Apoptosis shapes brain structure and function during early life. However, aberrant apoptosis, including that associated with the general anaesthetic propofol, is undesirable. Dexmedetomidine (DEX) provides potential neuroprotection against apoptosis, but the underlying mechanism remains unknown. We exposed neonatal rodent hippocampal astrocytes to propofol alone and in combination with DEX and yohimbine (an α₂ -adrenergic receptor antagonist), then evaluated cell viability using the MTT assay. The underlying regulatory mechanism associated with apoptosis-related genes was detected using a combinational strategy including double immunofluorescent staining, real-time reverse transcription polymerase chain reaction (RT-PCR), western blot, and flow cytometry. Propofol reduced matrix metallopeptidase 9 (MMP9) in cultured astrocytes, and activated the rno-miR-665/Bcl2-like 1 (Bcl2l1)/cleaved caspase 9 (CC9)/cleaved caspase 3 (CC3) pathway. Combinations incorporating propofol with A-1155463 (a selective Bcl2l1 inhibitor) or MMP9 antagomir reduced Bcl2l1 and promoted apoptosis. Co-culture of propofol with Bcl2l1 or with MMP9 agomir was sufficient to decrease the pro-apoptotic effects of propofol. Interestingly, DEX alone had no significant effect on apoptosis. When combined with propofol, however, the negative effects of propofol on the MMP9 and apoptosis-related genes (Bcl2l1, CC9, and CC3) were reduced. Furthermore, yohimbine pretreatment blocked the neuroprotective effects of DEX. Rno-miR-665 was also found to reduce MMP9 expression in propofol-treated hippocampal astrocytes. Taken together, the results indicate that DEX pretreatment reduces propofol-associated pro-apoptosis in developing astrocytes via downregulation of anti-apoptotic signalling mediated by Bcl2l1.

NPAS4 suppresses propofol-induced neurotoxicity by inhibiting autophagy in hippocampal neuronal cells

Propofol, a general intravenous anesthetic, has been demonstrated to cause a profound neuroapoptosis in the developing brain followed by long-term neurocognitive impairment. Our study aimed to examine the neuroprotective effect of neuronal PAS domain protein 4 (NPAS4), an activity-dependent neuron-specific transcription factor, on propofol-induced neurotoxicity in hippocampal neuronal HT22 cells. The differentially expressed genes in HT22 cells after treatment with propofol were screened from Gene Expression Omnibus dataset GSE106799. NPAS4 expression in HT22 cells treated with different doses of propofol was investigated by qRT-PCR and Western blot analysis. Cell viability, lactate dehydrogenase (LDH) release, caspase-3 activity, and apoptosis were evaluated by MTT, a LDH-Cytotoxicity Assay Kit, a Caspase-3 Colorimetric Assay Kit, and TUNEL assay, respectively. The protein levels of LC3-I, LC3-II, Beclin 1, p62 and NPAS4 were detected using Western blot analysis. Propofol treatment concentration-dependently decreased NPAS4 expression in HT22 cells. Propofol treatment inhibited cell viability, increased LDH release and caspase-3 activity, and induced apoptosis and autophagy in HT22 cells. NPAS4 overexpression suppressed propofol-induced cell injury and autophagy in HT22 cells. Mechanistically, autophagy agonist rapamycin attenuated the neuroprotective effect of NPAS4 in propofol-treated HT22 cells. In conclusion, NAPS4 overexpression protected hippocampal neuronal HT22 cells against propofol-induced neurotoxicity by reducing autophagy.

Role of NR2B/ERK signaling in the neuroprotective effect of dexmedetomidine against sevoflurane induced neurological dysfunction in the developing rat brain

Dexmedetomidine (DEX) is a potent α‑2 adrenergic receptor agonist and has been widely applied in clinic. The present study explored the protective effect of DEX on sevoflurane‑induced learning and cognitive impairment and examined its underlying mechanism. Sprague‑Dawley rat pups were exposed to 0.85% sevoflurane for 6 h and injected with DEX in different doses. The Morris water maze test was performed to evaluate the learning and memory function of rats. Western blot was used for the measurement of protein levels. The water maze results indicated that sevoflurane treatment increased the escape latency but reduced the time spent in the original quadrant of rats. The protein levels of NR2B, phosphorylated ERK were significantly influenced by sevoflurane. Ifenprodil administration alleviated sevoflurane‑induced neurological impairment. DEX treatment reversed the effect of sevoflurane on both escape latency and time in original quadrant in a dose manner, and pretreatment with DEX had the most dramatic effect. DEX regulated the NR2B/ERK signaling in sevoflurane treated rats. NR2B/ERK signaling is involved in sevoflurane induced neurological impairment. DEX may protect against sevoflurane induced neurological dysfunction in the developing rat brain via regulating the NR2B/ERK signaling.

Quantitative behavioural phenotyping to investigate anaesthesia induced neurobehavioural impairment

Anaesthesia exposure to the developing nervous system causes neuroapoptosis and behavioural impairment in vertebrate models. Mechanistic understanding is limited, and target-based approaches are challenging. High-throughput methods may be an important parallel approach to drug-discovery and mechanistic research. The nematode worm Caenorhabditis elegans is an ideal candidate model. A rich subset of its behaviour can be studied, and hundreds of behavioural features can be quantified, then aggregated to yield a 'signature'. Perturbation of this behavioural signature may provide a tool that can be used to quantify the effects of anaesthetic regimes, and act as an outcome marker for drug screening and molecular target research. Larval C. elegans were exposed to: isoflurane, ketamine, morphine, dexmedetomidine, and lithium (and combinations). Behaviour was recorded, and videos analysed with automated algorithms to extract behavioural features. Anaesthetic exposure during early development leads to persisting behavioural variation (in total, 125 features across exposure combinations). Higher concentrations, and combinations of isoflurane with ketamine, lead to persistent change in a greater number of features. Morphine and dexmedetomidine do not appear to lead to behavioural impairment. Lithium rescues the neurotoxic phenotype produced by isoflurane. Findings correlate well with vertebrate research: impairment is dependent on agent, is concentration-specific, is more likely with combination therapies, and can potentially be rescued by lithium. These results suggest that C. elegans may be an appropriate model with which to pursue phenotypic screens for drugs that mitigate the neurobehavioural impairment. Some possibilities are suggested for how high-throughput platforms might be organised in service of this field.

The potential role of dexmedetomidine on neuroprotection and its possible mechanisms: Evidence from in vitro and in vivo studies

Neurological disorders following brain injuries and neurodegeneration are on the rise worldwide and cause disability and suffering in patients. It is crucial to explore novel neuroprotectants. Dexmedetomidine, a selective α2-adrenoceptor agonist, is commonly used for anxiolysis, sedation and analgesia in clinical anaesthesia and critical care. Recent studies have shown that dexmedetomidine exerts protective effects on multiple organs. This review summarized and discussed the current neuroprotective effects of dexmedetomidine, as well as the underlying mechanisms. In preclinical studies, dexmedetomidine reduced neuronal injury and improved functional outcomes in several models, including hypoxia-induced neuronal injury, ischaemic-reperfusion injury, intracerebral haemorrhage, post-traumatic brain injury, anaesthetic-induced neuronal injury, substance-induced neuronal injury, neuroinflammation, epilepsy and neurodegeneration. Several mechanisms are associated with the neuroprotective function of dexmedetomidine, including neurotransmitter regulation, inflammatory response, oxidative stress, apoptotic pathway, autophagy, mitochondrial function and other cell signalling pathways. In summary, dexmedetomidine has the potential to be a novel neuroprotective agent for a wide range of neurological disorders.

Protective effects of dexmedetomidine on cerebral ischemia/reperfusion injury via the microRNA-214/ROCK1/NF-κB axis

BACKGROUND

Cerebral ischemia/reperfusion injury (CIRI) is a complication of surgical procedure associated with high mortality. The protective effect of dexmedetomidine (DEX) on CIRI has been explored in previous works, yet the underlying molecular mechanism remains unclear. Our study explored the protective effect of DEX and its regulatory mechanism on CIRI.

METHODS

A CIRI rat model was established using middle cerebral artery occlusion (MCAO). Neurological deficit scores for rats received MCAO modeling or DEX treatment were measured. Cerebral infarction area of rats was detected by TTC staining, while damage of neurons in hippocampal regions of rats was determined by hematoxylin-eosin (HE) staining. Apoptosis rate of neurons in hippocampal regions was examined by TUNEL staining. The dual-luciferase assay was performed to detect the binding of microRNA-214 (miR-214) to Rho-associated kinase 1 (ROCK1).

RESULTS

DEX treatment significantly reduced infarction area of MCAO rats and elevated miR-214 expression. Injection of miR-214 inhibitor attenuated the effect of DEX in MCAO rats by increasing the area of cerebral infarction in rats and apoptosis rate of hippocampal neurons. ROCK1 was targeted and negatively regulated by miR-214. The overexpression of ROCK1 led to activation of NF-κB to aggravate CIRI.

CONCLUSION

Therapeutic effects of DEX on CIRI was elicited by overexpressing miR-214 and impairing ROCK1 expression and NF-κB activation. Our finding might provide novel insights into the molecular mechanism of DEX in rats with CIRI.

Effects of dexmedetomidine on neurocognitive disturbance after elective non-cardiac surgery in senile patients: a systematic review and meta-analysis

OBJECTIVE

Senile patients often experience neurocognitive disturbance after non-cardiac surgery. Several clinical trials have investigated if the perioperative intravenous use of dexmedetomidine has a positive effect on the prevention of neurocognitive dysfunction, but the results have been inconsistent. We performed a meta-analysis to investigate the effects of dexmedetomidine on neurocognitive disturbance after elective non-cardiac surgery in senile patients.

METHODS

The PubMed, Cochrane Library, EMBASE and China National Knowledge Infrastructure databases were comprehensively searched for all randomized controlled trials published before 1 February 2020 that investigated the efficacy of dexmedetomidine in the prevention of postoperative delirium (POD) or postoperative cognitive dysfunction (POCD).

RESULTS

Sixteen studies involving 4376 patients were included in this meta-analysis. Compared with the control (i.e., saline), the perioperative intravenous use of dexmedetomidine significantly reduced the incidence of POD and POCD. However, patients in the dexmedetomidine group were more likely to develop bradycardia and hypotension during the administration of dexmedetomidine than patients in the control group. There were no differences between the two groups in the incidence of nausea and vomiting or mortality rate.

CONCLUSION

Dexmedetomidine has a positive effect on the prevention of neurocognitive disturbance in senile patients after elective non-cardiac surgery.

Effects of dexmedetomidine on the function of distal organs and oxidative stress after lower limb ischaemia-reperfusion in elderly patients undergoing unilateral knee arthroplasty

Aims

This study aims to evaluate the effects of dexmedetomidine on organ function, inflammation response, and oxidative stress in elderly patients following iatrogenic lower limb ischaemia–reperfusion (IR) during unilateral total knee arthroplasty.

Methods

Following unilateral total knee arthroplasty, 54 elderly patients were randomized to receive either intraoperative intravenous injection of dexmedetomidine (n = 27) or equivalent volume of 0.9% saline (n = 27). Blood samples were harvested at 5 minutes before lower limb tourniquet release (baseline); and 1, 6 and 24 hours after tourniquet release. Surrogate markers of cardiac, pulmonary, hepatic and renal function, oxidative stress, inflammatory response, along with parasympathetic and sympathetic activity were recorded and analysed.

Results

The levels of blood xanthine oxidase, creatine kinase, lactic acid and respiratory index increased in patients following tourniquet‐induced lower limb IR injury. Dexmedetomidine administration decreased the respiratory index (P = .014, P = .01, and P = .043) and the norepinephrine level (P < .001) at 1, 6 and 24 hours; and decreased the xanthine oxidase level (P = .049, P < .001) at 6 and 24 hours after tourniquet release compared with the Control group. Other measurements, including creatine kinase isoenzyme, lactate dehydrogenase, creatinine, urea nitrogen, glutamic–oxalacetic transaminase, glutamic–pyruvic transaminase, malondialdehyde, interleukin‐1, interleukin‐6 and tumour necrosis factor‐α, were not statistically significantly different between the 2 groups.

Conclusions

Intraoperative dexmedetomidine administration in elderly patients dampens the deterioration in respiratory function and suppresses the oxidative stress response in elderly patients following iatrogenic lower limb IR injury.

Neuroprotection of the Developing Brain by Dexmedetomidine Is Mediated by Attenuating Single Propofol-induced Hippocampal Apoptosis and Synaptic Plasticity Deficits

Dexmedetomidine (DEX) has neuroprotective effects and its efficacy was determined in propofol-treated pups. Postnatal day (P) 7 rats were exposed to propofol and DEX to investigate the induced apoptosis-related gene expression. Furthermore, synaptic structural changes at the cellular level were observed by electron microscopy. Induction of hippocampal long-term potentiation (LTP) of P30 rats and long-lasting performance of spatial discrimination at P30 and P60 were evaluated. After a single propofol exposure to P7 rats, DEX pretreatment effectively rescued the profound apoptosis seen in hippocampal neurocytes, and strongly reversed the aberrant expression levels of Bcl2-like 1 (BCL2L1), matrix metallopeptidase 9 (MMP-9) and cleaved caspase 3 (CC3), and sharply enhanced synaptic plasticity. However, there were no significant differences in escape latency or crossing times in a probe test. This was accompanied by no obvious reduction in search strategies among the rat groups. No impairment of long-term learning and memory in P30 or P60 rats was detected when using a single dose propofol treatment during the most vulnerable period of brain development. DEX was shown to ameliorate the rodent developmental neurotoxicity caused by a single neonatal propofol challenge, by altering MMP-9, BCL2L1 and CC3 apoptotic signaling.

Effects of local dexmedetomidine administration on the neurotoxicity of ropivacaine for sciatic nerve block in rats

Dexmedetomidine, used as an adjuvant to local anesthetics (LAs), may prolong the duration of peripheral nerve block. However, the effect of dexmedetomidine on the neurotoxicity of LAs is not completely understood. The present study was designed to investigate the efficacy of two doses of dexmedetomidine as an adjuvant to ropivacaine and its protective effect against the neurotoxicity of LAs. Paw withdrawal thermal latency testing was used to detect the sensory blockade. Extensor postural thrust testing was used to detect the motor blockade. The results demonstrated that the addition of dexmedetomidine to ropivacaine prolonged the duration of sensory and motor blockade in a dose-dependent manner compared with ropivacaine alone. TUNEL staining was performed to examine apoptosis. Western blotting was used to detect the Cleaved caspase-3 expression levels. The results showed that the addition of dexmedetomidine to ropivacaine decreased the rate of apoptosis and caspase-3 expression levels in a dose-dependent manner compared with ropivacaine alone (P<0.05). In addition, the rate of apoptosis and caspase-3 expression levels were significantly lower in the high-dose dexmedetomidine group compared with the low-dose dexmedetomidine group (P<0.05). The results suggested that the addition of dexmedetomidine to ropivacaine for sciatic nerve block in rats not only prolonged the duration of sensory and motor block of the sciatic nerve, but also markedly alleviated ropivacaine-induced neurotoxicity by decreasing caspase-3-dependent sciatic nerve cell apoptosis. Furthermore, the present study indicated that dexmedetomidine was more effective at a dose of 20 µg/kg compared with 6 µg/kg.

Research progress and treatment strategies for anesthetic neurotoxicity

Every year, a large number of infants and young children worldwide are administered general anesthesia. Whether general anesthesia adversely affects the intellectual development and cognitive function of children at a later date remains controversial. Many animal experiments have shown that general anesthetics can cause nerve damage during development, affect synaptic plasticity, and induce apoptosis, and finally affect learning and memory function in adulthood. The neurotoxicity of pediatric anesthetics (PAN) has received extensive attention in the field of anesthesia, which has been listed as a potential problem affecting public health by NFDA of the United States. Previous studies on rodents and non-human primates indicate that inhalation of anesthetics early after birth can induce long-term and sustained impairment of learning and memory function, as well as changes in brain function. Many anti-oxidant drugs, dexmedetomidine, as well as a rich living environment and exercise have been proven to reduce the neurotoxicity of anesthetics. In this paper, we summarize the research progress, molecular mechanisms and current intervention measures of anesthetic neurotoxicity.

Dexmedetomidine attenuates cisplatin-induced cognitive impairment by modulating miR-429-3p expression in rats

Chemotherapy-induced cognitive impairment (CICI) is widely recognized as a frequent adverse side effect following the administration of chemotherapeutic agents. This study aimed to explore the neuroprotective functions and mechanisms of microRNAs (miRNAs) mediated by dexmedetomidine (Dex) on cisplatin-induced CICI. The model rats received 5 mg/kg cisplatin injections once per week for 4 weeks. Dex (30 μg/kg) was administered before cisplatin treatment. The protective effects of Dex were evaluated using Morris water maze, Nissl staining, and transmission electron microscopy. Dex-mediated miRNAs were screened via miRNA sequencing. The effects of Dex and key miRNAs on mitochondrial DNA gene mt-ND1 and caspase-9 expression were tested. Dex exhibited a protective effect against decreased learning memory ability, hippocampal neuronal damage, and mitochondrial damage in CICI rats. Thirty-nine differentially expressed (DE) miRNAs were screened, 13 of which responded positively to Dex treatment. Gene Ontology annotation identified that DE miRNAs were mainly involved in transcription, DNA-templated. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that DE miRNAs were mainly involved in neuronal function and brain development-related pathways, such as axon guidance and calcium signaling pathways. Compared to cisplatin treatment, the expression of miR-429-3p responded more strongly to Dex treatment. In cisplatin-treated cultured hippocampal neurons, Dex treatment and miR-429-3p overexpression significantly increased mitochondrial DNA gene mt-ND1expression and decreased caspase-9 expression. Our study suggests that Dex alleviates CICI by modulating miR-429-3p expression in rats. Thus, Dex may be effective in preventing the side effects of cisplatin.

Dexmedetomidine Attenuates Glutamate-Induced Cytotoxicity by Inhibiting the Mitochondrial-Mediated Apoptotic Pathway

Background

Glutamate (GLU) is the most excitatory amino acid in the central nervous system and plays an important role in maintaining the normal function of the nervous system. During cerebral ischemia, massive release of GLU leads to neuronal necrosis and apoptosis. It has been reported that dexmedetomidine (DEX) possesses anti-oxidant and anti-apoptotic properties. The objective of this study was to investigate the effects of DEX on GLU-induced neurotoxicity in PC12 cells.

Material/Methods

PC12 cells were treated with 20 mM GLU to establish an ischemia-induced injury model. Cell viability was accessed by MTT assay. MDA content and SOD activity were analyzed by assay kits. Apoptosis rate, ROS production, intracellular Ca²⁺ concentration, and MMP were evaluated by flow cytometry. Western blot analysis was performed to analyze expressions of caspase-3, caspase-9, cyt-c, bax, and bcl-2.

Results

PC12 cells treated with GLU exhibited reduced cell viability and increased apoptosis rates, which were ameliorated by pretreatment with DEX. DEX significantly increased SOD activity, reduced content of MDA, and decreased production of ROS in PC12 cells. In addition, DEX clearly reduced the level of intracellular Ca²⁺ and attenuated the decline of MMP. Moreover, DEX notably reduced expressions of caspase-3, caspase-9, cyt-c, and bax and increased expression of bcl-2.

Conclusions

Our findings suggest that DEX can protect PC12 cells against GLU-induced cytotoxicity, which may be attributed to its anti-oxidative property and reduction of intracellular calcium overload, as well as its ability to inhibit the mitochondria-mediated apoptotic pathway.

MicroRNA-665 mediates propofol-induced cell apoptosis in human stem cell-derived neurons

We aimed to evaluate the neurotoxicity and mechanisms of anesthetics propofol in hESC-derived neurons. Cell apoptosis in hESC-derived neurons' exposure to 4, 10 and 20 μg/mL propofol for 6 h was assessed using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate in situ nick end labeling (TUNEL) staining and microRNA-665 (miR-665) expression was assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR). miR-665 was overexpressed and knocked down using a miR-665 mimic and anti-665 transfection, respectively. The results showed that hESCs exposed to propofol showed a dose-dependent cell apoptosis, followed by the upregulation of miR-665 expression. Overexpression of miR-665 increased propofol-induced apoptosis in hESC cells. And targeting miR-665 decreased propofol-induced cell apoptosis in hESC cells. These data suggest that propofol induces cell death in hESC-derived neurons and the propofol-induced cell apoptosis may occur via miR-665-dependent mechanism.

Current Evidence on Cell Death in Preterm Brain Injury in Human and Preclinical Models

Despite tremendous advances in neonatal intensive care over the past 20 years, prematurity carries a high burden of neurological morbidity lasting lifelong. The term encephalopathy of prematurity (EoP) coined by Volpe in 2009 encompasses all aspects of the now known effects of prematurity on the immature brain, including altered and disturbed development as well as specific lesional hallmarks. Understanding the way cells are damaged is crucial to design brain protective strategies, and in this purpose, preclinical models largely contribute to improve the comprehension of the cell death mechanisms. While neuronal cell death has been deeply investigated and characterized in (hypoxic–ischemic) encephalopathy of the newborn at term, little is known about the types of cell death occurring in preterm brain injury. Three main different morphological cell death types are observed in the immature brain, specifically in models of hypoxic–ischemic encephalopathy, namely, necrotic, apoptotic, and autophagic cell death. Features of all three types may be present in the same dying neuron. In preterm brain injury, description of cell death types is sparse, and cell loss primarily concerns immature oligodendrocytes and, infrequently, neurons. In the present review, we first shortly discuss the different main severe preterm brain injury conditions that have been reported to involve cell death, including periventricular leucomalacia (PVL), diffuse white matter injury (dWMI), and intraventricular hemorrhages, as well as potentially harmful iatrogenic conditions linked to premature birth (anesthesia and caffeine therapy). Then, we present an overview of current evidence concerning cell death in both clinical human tissue data and preclinical models by focusing on studies investigating the presence of cell death allowing discriminating between the types of cell death involved. We conclude that, to improve brain protective strategies, not only apoptosis but also other cell death (such as regulated necrotic and autophagic) pathways now need to be investigated together in order to consider all cell death mechanisms involved in the pathogenesis of preterm brain damage.

Effects of embryonic propofol exposure on axonal growth and locomotor activity in zebrafish

Prenatal propofol exposure induced neurotoxicity in the developing brains and led to persistent learning deficits in the offspring. Our goal was to use zebrafish to explore whether the decline in learning and memory was correlated with inhibition of neuronal growth after propofol exposure. Zebrafish embryos at 6 hours postfertilization (hpf) were exposed to control or 1, 2 or 4 μg/mL propofol until 48 hpf. Spontaneous locomotor activity and swimming behavior in response to dark-to-light photoperiod stimulation were studied in zebrafish larvae at 6 days postfertilization (dpf). The adaptability to repeated stimulation was used to indicate learning and memory function of larvae. Transgenic NBT line zebrafish was used to quantitate the effect of propofol on motor neuronal growth of embryos in vivo. Six dpf transgenic zebrafish larvae went through photoperiod stimulation after their neuronal length had been analyzed during the embryonic period. Our data indicate that embryonic exposure to 1, 2 and 4 μg/mL propofol had no adverse effect on spontaneous movement in zebrafish larvae, but 2 and 4 μg/mL propofol significantly impaired the learning and memory function of larvae. Moreover, propofol significantly inhibited axonal growth of motor neurons during the embryonic stage, which was correlated with learning and memory deficiency in larvae. Our findings demonstrate that the neuronal growth was correlated with learning and memory function, indicating the relevance of zebrafish as a new model to explore the mechanisms through which propofol induces long-term learning and memory impairment.

Inhibition of the electron transport chain in propofol induced neurotoxicity in zebrafish embryos

Fetal and neonatal exposure to propofol can lead to neuronal death and long-term neurobehavioral deficiencies in both rodents and nonhuman primates. Zebrafish embryo, which is fertilized ex-utero, has provided us a new model species to study the effects of general anesthetics on developing brain. Inhibited electron transport chain leads to mitochondrial dysfunction and insufficient energy production. The aim of this study was to dissect the role of electron transport chain in propofol-induced neurotoxicity. 6 h post fertilization (hpf) zebrafish embryos were exposed to control or 1, 2 or 4 μg/ml propofol until 48hpf. Acridine orange staining was used to assess cell apoptosis in the brain of zebrafish embryos. The activity of mitochondrial electron transport chain complex was assessed using colorimetric method. Expression of key subunit of cytochrome c oxidase was assessed by western blot and transcription level of cox4i1 was assessed by quantitative real time-PCR. The mitochondrial membrane potential and ATP content were assessed. Exposure to 1, 2 and 4 μg/ml propofol induced significant increases in cell apoptosis in the brain of zebrafish embryos in a dose-dependent manner and led to significant decreases in electron transport chain complex IV activity from (0.161 ± 0.023)μmol/mg/min in blank control-treated group to (0.096 ± 0.015)μmol/mg/min, (0.083 ± 0.013)μmol/mg/min and (0.045 ± 0.014)μmol/mg/min respectively, accompanied by decreased expression of key regulatory subunit of cytochrome c oxidase-subunit IV and decreased transcription level of cox4i1. Propofol exposure also decreased the mitochondrial membrane potential and ATP content. Our findings demonstrate that inhibition of the electron transport chain is involved in the mechanisms by which propofol induces neurotoxicity in the developing brain.

Efficacy of premedication with intranasal dexmedetomidine for removal of inhaled foreign bodies in children by flexible fiberoptic bronchoscopy: a randomized, double-blind, placebo-controlled clinical trial

Background

Tracheobronchial foreign body aspiration in children is a life-threatening, emergent situation. Currently, the use of fiberoptic bronchoscopy for removing foreign bodies is attracting increasing attention. Oxygen desaturation, body movement, laryngospasm, bronchospasm, and breath-holding are common adverse events during foreign body removal. Dexmedetomidine, as a highly selective α₂-adrenergic agonist, produces sedative and analgesic effects, and does not induce respiratory depression. We hypothesized that intranasal dexmedetomidine at 1 μg kg − 1 administered 25 min before anesthesia induction can reduce the incidence of adverse events during fiberoptic bronchoscopy under inhalation general anesthesia with sevoflurane.

Methods

In all, 40 preschool-aged children (6–48 months) with an American Society of Anesthesiologists physical status of I or II were randomly allocated to receive either intranasal dexmedetomidine at 1 μg·kg − 1 or normal saline at 0.01 ml kg^− 1 25 min before anesthesia induction. The primary outcome was the incidence of perioperative adverse events. Heart rate, respiratory rate, parent-child separation score, tolerance of the anesthetic mask, agitation score, consumption of sevoflurane, and recovery time were also recorded.

Results

Following pre-anesthesia treatment with either intranasal dexmedetomidine or saline, the incidences of laryngospasm (15% vs. 50%), breath-holding (10% vs. 40%), and coughing (5% vs. 30%) were significantly lower in patients given dexmedetomidine than those given saline. Patients who received intranasal dexmedetomidine had a lower parent–child separation score (P = 0.017), more satisfactory tolerance of the anesthetic mask (P = 0.027), and less consumption of sevoflurane (38.18 ± 14.95 vs. 48.03 ± 14.45 ml, P = 0.041). The frequency of postoperative agitation was significantly lower in patients given intranasal dexmedetomidine (P = 0.004), and the recovery time was similar in the two groups.

Conclusions

Intranasal dexmedetomidine 1 μg·kg^− 1, with its sedative and analgesic effects, reduced the incidences of laryngospasm, breath-holding, and coughing during fiberoptic bronchoscopy for FB removal. Moreover, it reduced postoperative agitation without a prolonged recovery time.

Trail registration

The study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR1800017273) on July 20, 2018.

Impact of postoperative dexmedetomidine infusion on incidence of delirium in elderly patients undergoing major elective noncardiac surgery: a randomized clinical trial

PURPOSE

Postoperative delirium is a serious and common complication, it occurs in 13-50% of elderly patients after major surgery, and presages adverse outcomes. Emerging literature suggests that dexmedetomidine sedation in critical care units (intensive care unit) is associated with reduced incidence of delirium. However, few studies have investigated whether postoperative continuous infusion of dexmedetomidine could safely decrease the incidence of delirium in elderly patients admitted to general surgical wards after noncardiac surgery.

PATIENTS AND METHODS

This double-blind, randomized, placebo-controlled trial was conducted in patients aged 65 years or older undergoing major elective noncardiac surgery without a planned ICU stay. Eligible patients were randomly assigned to receive either dexmedetomidine (0.1 μg/kg/h) or placebo (0.9% normal saline) immediately after surgery though patient-controlled intravenous analgesia device. The primary outcome was the incidence of delirium during the first 5 postoperative days. Secondary outcomes included postoperative subjective pain scores and subjective sleep quality. The study dates were from January 2018 to January 2019.

RESULTS

A total of 557 patients were randomly assigned to receive either dexmedetomidine (n=281) or placebo (n=276). The incidence of postoperative delirium had no difference between the dexmedetomidine and placebo groups (11.7% [33 of 281] vs 13.8% [38 of 276], P=0.47). Compared with placebo group, patients in dexmedetomidine group reported significant lower numerical rating score pain scores at 3, 12, 24, and 48 hrs after surgery (all P<0.05) and significant improved Richards Campbell Sleep Questionnaire results during the first 3 postoperative days (all P<0.0001). Dexmedetomidine-related adverse events were similar between the two groups.

CONCLUSION

Postoperative continuous infusion of dexmedetomidine did not decrease the incidence of postoperative delirium in elderly patients admitted to general surgical wards after elective noncardiac surgery.

Dexmedetomidine for the prevention of postoperative delirium in elderly patients undergoing noncardiac surgery: A meta-analysis of randomized controlled trials

BACKGROUND

Postoperative delirium (POD) among the elderly population that undergoes noncardiac surgery is significantly associated with adverse clinical outcomes. We conducted this meta-analysis to evaluate the effectiveness and safety of dexmedetomidine for the prophylaxis of POD among the elderly population after noncardiac surgery.

METHODS

We searched Embase, PubMed, and the Cochrane Library from inception date to March 2019 for randomized controlled trials (RCTs) that compared dexmedetomidine and placebo for the prevention of POD and evaluated the major cardiovascular outcomes among elderly people after noncardiac surgery. Two authors independently screened the studies and extracted data from the published articles. The main outcome was the incidence of POD. The secondary outcomes included the occurrence of bradycardia, hypotension, hypertension, tachycardia, myocardial infarction, stroke, hypoxaemia, and all-cause mortality.

RESULTS

A total of 6 RCTs with 2102 participants were included. Compared with placebo, dexmedetomidine significantly reduced the prevalence of POD (RR = 0.61, 95% CI 0.34-0.76, P = 0.001, I2 = 66%), and the risk of tachycardia (RR = 0.48, 95% CI 0.30-0.76, P = 0.002, I2 = 0%), hypertension (RR = 0.59, 95% CI 0.44-0.79, P < 0.001, I2 = 20%), stroke (RR = 0.22, 95% CI 0.06-0.76, P = 0.02, I2 = 0%), and hypoxaemia (RR = 0.50, 95% CI 0.32-0.78, P = 0.002, I2 = 0%) in elderly patients who underwent noncardiac surgery. However, dexmedetomidine accelerated the occurrence of bradycardia (RR = 1.36, 95% CI 1.11-1.67, P = 0.003, I2 = 0%). Furthermore, no significant differences were observed in the incidence of hypotension, myocardial infarction, and all-cause mortality between the dexmedetomidine and placebo groups.

CONCLUSIONS

Among elderly patients after noncardiac surgery, the prophylactic use of dexmedetomidine, compared with the use of placebo, was related to a decline in the incidence of POD.

Both GSK-3β/CRMP2 and CDK5/CRMP2 pathways participate in the protection of dexmedetomidine against propofol-induced learning and memory impairment in neonatal rats

Dexmedetomidine has been reported to ameliorate propofol-induced neurotoxicity in neonatal animals. However, the underlying mechanism is still undetermined. Glycogen synthase kinase-3β (GSK-3β), cycline dependent kinase-5 (CDK5) and Rho-kinase (RhoA) pathways play critical roles in neuronal development. The present study is to investigate whether GSK-3β, CDK5 and RhoA pathways are involved in the neuroprotection of dexmedetomidine. Seven-day-old (P7) Sprague-Dawley rats were anesthetized with propofol for 6 h. Dexmedetomidine at various concentrations were administered before propofol exposure. Neuroapoptosis, the neuronal proliferation and the level of neurotransmitter in the hippocampus were evaluated. The effects of GSK-3β inhibitor SB415286, CDK5 inhibitor roscovitine or RhoA inhibitor Y276321 on propofol-induced neurotoxicity were assessed. Propofol induced apoptosis in the hippocampal neurons and astrocytes, inhibited neuronal proliferation in the DG region, down-regulated the level of γ-aminobutyric acid (GABA) and glutamate in the hippocampus, and impaired long-term cognitive function. These harmful effects were reduced by pretreatment with 50 μg·kg-1 dexmedetomidine. Moreover, propofol activated GSK-3β and CDK5 pathways, but not RhoA pathway, by reducing the phosphorylation of GSK-3β (ser 9), increasing the expression of CDK5 activator P25 and increasing the phosphorylation of their target sites on CRMP2 shortly after exposure. These effects were reversed by pretreatment with 50 μg·kg-1 dexmedetomidine. Furthermore, SB415286 and roscovitine, not Y276321, attenuated the propofol-induced neuroapoptosis, brain cell proliferation inhibition, GABA and glutamate downregulation, and learning and memory dysfunction. Our results indicate that dexmedetomidine reduces propofol-induced neurotoxicity and neurocognitive impairment via inhibiting activation of GSK-3β/CRMP2 and CDK5/CRMP2 pathways in the hippocampus of neonatal rats.

Randomised controlled trial of dexmedetomidine sedation vs general anaesthesia for inguinal hernia surgery on perioperative outcomes in infants

BACKGROUND

Neonates and infants undergoing general anaesthesia for hernia surgery are at risk of perioperative cardiorespiratory adverse events. The use of regional anaesthesia with dexmedetomidine preserves airway tone and may potentially avoid these complications. This study compares the perioperative conditions and adverse events between dexmedetomidine sedation with caudal block and general anaesthesia with caudal block for inguinal hernia surgery in infants.

METHODS

A randomised controlled trial was conducted in a tertiary hospital in Singapore involving 104 infants younger than 3 months, who were randomised to receive either dexmedetomidine sedation (DEX) with caudal block or general sevoflurane anaesthesia with tracheal intubation and caudal block (GA) for inguinal hernia surgery. Perioperative conditions, haemodynamics and adverse events were compared between groups.

RESULTS

Fifty-one infants received DEX and 48 infants received GA. In the DEX group, 46 infants (90.2%) had their operations completed solely under this technique, two (3.9%) were converted to general anaesthesia with intubation, and three (5.9%) required brief administration of nitrous oxide or low-dose sevoflurane. Overall, 96.1% of infants in the DEX group did not require intubation. Perioperative conditions were similar in both groups. The DEX group had significantly lower heart rates and higher mean arterial pressures intraoperatively. Two infants in the DEX group (3.9%) required postoperative intensive care admission compared with six infants (12.5%) in the GA group.

CONCLUSIONS

Dexmedetomidine sedation with caudal block provides a feasible alternative to general anaesthesia in infants undergoing hernia surgery. This technique avoids the need for tracheal intubation, which may be beneficial in neonates.

CLINICAL TRIAL REGISTRATION

NCT02559102.

Dexmedetomidine attenuates the neurotoxicity of propofol toward primary hippocampal neurons in vitro via Erk1/2/CREB/BDNF signaling pathways

BACKGROUND

Propofol is a commonly used general anesthetic for the induction and maintenance of anesthesia and critical care sedation in children, which may add risk to poor neurodevelopmental outcome. We aimed to evaluate the effect of propofol toward primary hippocampal neurons in vitro and the possibly neuroprotective effect of dexmedetomidine pretreatment, as well as the underlying mechanism.

MATERIALS AND PROCEDURES

Primary hippocampal neurons were cultured for 8 days in vitro and pretreated with or without dexmedetomidine or phosphorylation inhibitors prior to propofol exposure. Cell viability was measured using cell counting kit-8 assays. Cell apoptosis was evaluated using a transmission electron microscope and flow cytometry analyses. Levels of mRNAs encoding signaling pathway intermediates were assessed using qRT-PCR. The expression of signaling pathway intermediates and apoptosis-related proteins was determined by Western blotting.

RESULTS

Propofol significantly reduced cell viability, induced neuronal apoptosis, and downregulated the expression of the BDNF mRNA and the levels of the phospho-Erk1/2 (p-Erk1/2), phospho-CREB (p-CREB), and BDNF proteins. The dexmedetomidine pretreatment increased neuronal viability and alleviated propofol-induced neuronal apoptosis and rescued the propofol-induced downregulation of both the BDNF mRNA and the levels of the p-Erk1/2, p-CREB, and BDNF proteins. However, this neuroprotective effect was abolished by PD98059, H89, and KG501, further preventing the dexmedetomidine pretreatment from rescuing the propofol-induced downregulation of the BDNF mRNA and p-Erk1/2, p-CREB, and BDNF proteins.

CONCLUSION

Dexmedetomidine alleviates propofol-induced cytotoxicity toward primary hippocampal neurons in vitro, which correlated with the activation of Erk1/2/CREB/BDNF signaling pathways.

A systematic review and narrative synthesis on the histological and neurobehavioral long-term effects of dexmedetomidine

BACKGROUND

Recent experimental studies suggest that currently used anesthetics have neurotoxic effects on young animals. Clinical studies are increasingly publishing about the effects of anesthesia on the long-term outcome, providing contradictory results. The selective alpha-2 adrenergic receptor agonist dexmedetomidine has been suggested as an alternative nontoxic sedative agent.

AIMS

The aim of this systematic review was to assess the potential neuroprotective and neurobehavioral effects of dexmedetomidine in young animals and children.

METHODS

Systematic searches separately for preclinical and clinical studies were performed in Medline Ovid and Embase on February 14, 2018.

RESULTS

The initial search found preclinical (n = 661) and clinical (n = 240) studies. A total of 20 preclinical studies were included. None of the clinical studies met the predefined eligibility criteria. Histologic injury by dexmedetomidine was evaluated in 11 studies, and was confirmed in three of these studies (caspase-3 activation or apoptosis). Decrease of injury caused by another anesthetic was evaluated in 16 studies and confirmed in 13 of these. Neurobehavioral tests were performed in seven out of the 20 studies. Of these seven rodent studies, three studies tested the effects of dexmedetomidine alone on neurobehavioral outcome in animals (younger than P21). All three studies found no negative effect of dexmedetomidine on the outcome. In six studies, outcome was evaluated when dexmedetomidine was administered following another anesthetic. Dexmedetomidine was found to lessen the negative effects of the anesthetic.

CONCLUSION

In animals, dexmedetomidine was found not to induce histologic injury and to show a beneficial effect when administered with another anesthetic. No clinical results on the long-term effects in children have been identified yet.

Dexmedetomidine protects the developing rat brain against the neurotoxicity wrought by sevoflurane: role of autophagy and Drp1-Bax signaling

BACKGROUND

The effect of sevoflurane on the nervous system is controversial. As an adjuvant anesthetic, dexmedetomidine has a protective role in various nerve-injury diseases. We investigated the effect of dexmedetomidine on injury to the developing brain induced by sevoflurane anesthesia, and if autophagy and mitochondrial damage are involved in the neuroprotective effects of dexmedetomidine.

METHODS

Pregnant rats on gestational day 20 were exposed to 3% sevoflurane for 4 hours. Saline and dexmedetomidine were injected intraperitoneally 15 minutes before exposure to sevoflurane or control gas. Bilateral hippocampi were harvested on postnatal day 1. Hippocampal morphology was observed by Nissl staining and expression of the microtubule-related protein LC3I/II, p62, Drp1, Bax, and Bcl2 were evaluated by Western blotting and immunohistochemistry.

RESULTS

Nissl staining showed that sevoflurane anesthesia during the third trimester caused neuronal damage to the hippocampi of rat pups. Western blotting and immunohistochemistry showed that pregnant rats exposed to sevoflurane during the third trimester led to pups having increased expression of LC3 and p62, suggesting that sevoflurane blocked autophagic flow in the hippocampus. Expression of Drp1 and Bax was increased after sevoflurane exposure, whereas Bcl2 expression was downregulated. All these effects were alleviated by pretreatment with dexmedetomidine.

CONCLUSION

Sevoflurane exposure during the third trimester caused neurological injury to rat pups. Autophagy and abnormalities in mitochondrial dynamics were involved in this neurotoxic process and were antagonized by dexmedetomidine.

Intravenous anesthetic-induced calcium dysregulation and neurotoxic shift with age during development in primary cultured neurons

Anesthetic-induced neurotoxicity in the developing brain is a concern. This neurotoxicity is closely related to anesthetic exposure time, dose, and developmental stages. Using calcium imaging and morphological examinations in vitro, we sought to determine whether intravenous anesthetic-induced direct neurotoxicity varies according to different stages of the days in vitro (DIV) of neurons in primary culture. Cortical neurons from E17 Wistar rats were prepared. On DIV 3, 7, and 13, cells were exposed to the intravenous anesthetics thiopental sodium (TPS), midazolam (MDZ), or propofol (PPF), to investigate direct neurotoxicity using morphological experiments. Furthermore, using calcium imaging, the anesthetic-induced intracellular calcium concentration ([Ca²⁺]i) elevation was monitored in cells on DIV 4, 8, and 13. All anesthetics elicited significant [Ca²⁺]i increases on DIV 4. While TPS (100 μM) and MDZ (10 μM) did not alter neuronal death, PPF (10 μM and 100 μM) decreased the survival ratio (SR) significantly. On DIV 8, TPS and MDZ did not elicit [Ca²⁺]i elevation or SR decrease, while PPF still induced [Ca²⁺]i elevation (both at 10 μM and 100 μM) and significant SR decrease at 100 μM (0.76 ± 0.03; P < 0.05), but not at 10 μM (0.91 ± 0.03). Such anesthetic-induced [Ca²⁺]i elevation and SR decrease were not observed on DIV 13-14 for any of the anesthetic drugs. Our study indicates that more caution may be exercised when using PPF compared to TPS or MDZ during development.

Impact of dexmedetomidine infusion during general anaesthesia on incidence of postoperative delirium in elderly patients after major non-cardiac surgery: study protocol of a randomised, double-blinded and placebo-controlled trial

INTRODUCTION

Delirium is a common complication in the elderly after surgery and is associated with worse outcomes. Multiple risk factors are related with postoperative delirium, such as exposure to general anaesthetics, pain and postoperative inflammatory response. Preclinical and clinical studies have shown that dexmedetomidine attenuated neurotoxicity induced by general anaesthetics, improved postoperative analgesia and inhibited inflammatory response after surgery. Several studies found that intraoperative use of dexmedetomidine can prevent postoperative delirium, but data were inconsistent. This study was designed to investigate the impact of dexmedetomidine administered during general anaesthesia in preventing delirium in the elderly after major non-cardiac surgery.

METHODS AND ANALYSIS

This is a randomised, double-blinded and placebo-controlled trial. 620 elderly patients (age ≥60 years) who are scheduled to undertake elective major non-cardiac surgery (with an expected duration ≥2 hours) are randomly divided into two groups. For patients in the dexmedetomidine group, a loading dose dexmedetomidine (0.6 µg/kg) will be administered 10 min before anaesthesia induction, followed by a continuous infusion at a rate of 0.5 µg/kg/hour until 1 hour before the end of surgery. For patients in the control group, normal saline will be administered with an identical rate as in the dexmedetomidine group. The primary endpoint is the incidence of delirium during the first five postoperative days. The secondary endpoints include pain intensity, cumulative opioid consumption and subjective sleep quality during the first three postoperative days, as well as the incidence of non-delirium complications and all-cause mortality within 30 days after surgery.

ETHICS AND DISSEMINATION

The study protocol was approved by the Clinical Research Ethics Committee of Peking University First Hospital (2015-987) and registered at Chinese Clinical Trial Registry (http://www.chictr.org.cn) with identifier ChiCTR-IPR-15007654. The results of the study will be presented at academic conferences and submitted to peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ChiCRR-IPR-15007654; Pre-results.

Neurotoxicity of anesthetic drugs: an update

PURPOSE OF REVIEW

This article reviews the most recently published evidence that investigated anesthesia-induced neurotoxicity in both animals and humans, especially as it pertains to the perinatal period.

RECENT FINDINGS

Several recent studies have focused on better understanding the complex mechanisms that underlie intravenous and volatile anesthesia-induced neurotoxicity in animals. Adjuvant agents that target these pathways have been investigated for their effectiveness in attenuating the neuroapoptosis and neurocognitive deficits that result from anesthesia exposure, including dexmedetomidine, rutin, vitamin C, tumor necrosis factor α, lithium, apocynin, carreic acid phenethyl ester. Five clinical studies, including one randomized control trial, provided inconsistent evidence on anesthesia-induced neurotoxicity in humans.

SUMMARY

Despite a growing body of preclinical studies that have demonstrated anesthesia-induced neurotoxic effects in the developing and aging brain, their effects on the human brain remains to be determined. The performance of large-scale human studies is limited by several important factors, and noninvasive biomarkers and neuroimaging modalities should be employed to define the injury phenotypes that reflect anesthesia-induced neurotoxicity. Ultimately, the use of these modalities may provide new insights into whether the concerns of anesthetics are justified in humans.

A different perspective: anesthesia for extreme premature infants: is there an age limitation or how low should we go?

PURPOSE OF REVIEW

To put in perspective, the various challenges that faces pediatric anesthesiologists because of the recently lowered limits with regards to the viability of a fetus. Both medical and ethical considerations will be highlighted.

RECENT FINDINGS

Issues related to: who should anesthetize these tiny babies; can we provide adequate and legal monitoring during the anesthetic; does these immature babies need hypnosis and amnesia and the moral/ethical implications associated with being involved with care of doubtful long-term outcome are reviewed.

SUMMARY

There does currently not exist sufficient research data to provide any evidence-based guidelines for the anesthetic handling of extreme premature infants. Current practice relies on extrapolations from other patient groups and from attempting to preserve normal physiology. Thus, focused research initiatives within this specific field of anesthesia should be a priority. Furthermore, in-depth multiprofessional ethical discussions regarding long-term outcome of aggressive care of extremely premature babies are urgently needed, including the new concepts of disability-free survival and number-need-to-suffer.

Propofol exposure during early gestation impairs learning and memory in rat offspring by inhibiting the acetylation of histone

Propofol is widely used in clinical practice, including non-obstetric surgery in pregnant women. Previously, we found that propofol anaesthesia in maternal rats during the third trimester (E18) caused learning and memory impairment to the offspring rats, but how about the exposure during early pregnancy and the underlying mechanisms? Histone acetylation plays an important role in synaptic plasticity. In this study, propofol was administered to the pregnant rats in the early pregnancy (E7). The learning and memory function of the offspring were tested by Morris water maze (MWM) test on post-natal day 30. Two hours before each MWM trial, histone deacetylase 2 (HDAC2) inhibitor, suberoylanilide hydroxamic acid (SAHA), Senegenin (SEN, traditional Chinese medicine), hippyragranin (HGN) antisense oligonucleotide (HGNA) or vehicle were given to the offspring. The protein levels of HDAC2, acetylated histone 3 (H3) and 4 (H4), cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), N-methyl-D-aspartate receptor (NMDAR) 2 subunit B (NR2B), HGN and synaptophysin in offspring's hippocampus were determined by Western blot or immunofluorescence test. It was discovered that infusion with propofol in maternal rats on E7 leads to impairment of learning and memory in offspring, increased the protein levels of HDAC2 and HGN, decreased the levels of acetylated H3 and H4 and phosphorylated CREB, NR2B and synaptophysin. HDAC2 inhibitor SAHA, Senegenin or HGN antisense oligonucleotide reversed all the changes. Thus, present results indicate exposure to propofol during the early gestation impairs offspring's learning and memory via inhibiting histone acetylation. SAHA, Senegenin and HGN antisense oligonucleotide might have therapeutic value for the adverse effect of propofol.

Neuroprotection of dexmedetomidine against propofol-induced neuroapoptosis partly mediated by PI3K/Akt pathway in hippocampal neurons of fetal rat*

The aim was to investigate how the PI3K/Akt pathway is involved in the protection of dexmedetomidine against propofol. The hippocampal neurons from fetal rats were separated and cultured in a neurobasal medium. Cell viability was assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Then neurons were pretreated with different concentrations of dexmedetomidine before 100 μmol/L propofol was added. Akt, phospho-Akt (p-Akt), Bad, phospho-Bad (p-Bad), and Bcl-xL were detected by Western blot. Also, neurons were pretreated with dexmedetomidine alone or given the inhibitor LY294002 before dexmedetomidine pretreatment, and then propofol was added for 3 h. The results demonstrated that propofol decreased the cell viability and the expression of p-Akt and p-Bad proteins, increased the level of Bad, and reduced the ratio of Bcl-xL/Bad. Dexmedetomidine pretreatment could reverse these effects. The enhancement of p-Akt and p-Bad induced by dexmedetomidine was prevented by LY294002. These results showed that dexmedetomidine potently protected the developing neuron and this protection may be partly mediated by the PI3K/Akt pathway.

Propofol's Effects on the Fetal Brain for Non-Obstetric Surgery

While the use of Propofol has been increasing in usage for general surgical procedures since its release to market, there has been little work done on its potential link to neurotoxicity in humans. Only recently, following the release of a warning label from the United States Food and Drug Administration (USFDA) regarding a potential link to "neurotoxicity" in the neonate, did the surgical and anesthesiology communities become more aware of its potential for harm. Given the widespread use of this drug in clinical practice, the warning label naturally raised controversy regarding intrapartum Propofol usage. While intended to generate further studies, the lack of a viable anesthetic alternative raises issues regarding its current usage for surgical procedures in pregnant women. To answer the question whether current evidence is supportive of Propofol usage at its current levels in pregnant women, this review summarizes available evidence of fetal Propofol exposure in animal studies.

Phase IV, Open-Label, Safety Study Evaluating the Use of Dexmedetomidine in Pediatric Patients Undergoing Procedure-Type Sedation

Dexmedetomidine (Precedex™) may be used as an alternative sedative in children, maintaining spontaneous breathing, and avoiding tracheal intubation in a non-intubated moderate or deep sedation (NI-MDS) approach. This open-label, single-arm, multicenter study evaluated the safety of dexmedetomidine in a pediatric population receiving NI-MDS in an operating room or a procedure room, with an intensivist or anesthesiologist in attendance, for elective diagnostic or therapeutic procedures expected to take at least 30 min. The primary endpoint was incidence of treatment-emergent adverse events (TEAEs). Patients received one of two doses dependent on age: patients aged ≥28 weeks' gestational age to <1 month postnatal received dose level 1 (0.1 μg/kg load; 0.05-0.2 μg/kg/h infusion); those aged 1 month to <17 years received dose level 2 (1 μg/kg load; 0.2-2.0 μg/kg/h infusion). Sedation efficacy was assessed and defined as adequate sedation for at least 80% of the time and successful completion of the procedure without the need for rescue medication. In all, 91 patients were enrolled (dose level 1, n = 1; dose level 2, n = 90); of these, 90 received treatment and 82 completed the study. Eight patients in dose level 2 discontinued treatment for the following reasons: early completion of diagnostic or therapeutic procedure (n = 3); change in medical condition (need for intubation) requiring deeper level of sedation (n = 2); adverse event (AE; hives and emesis), lack of efficacy, and physician decision (patient not sedated enough to complete procedure; n = 1 each). Sixty-seven patients experienced 147 TEAEs. The two most commonly reported AEs were respiratory depression (bradypnea; reported per protocol-defined criteria, based on absolute respiratory rate values for age or relative decrease of 30% from baseline) and hypotension. Four patients received glycopyrrolate for bradycardia and seven patients received intravenous fluids for hypotension. SpO₂ dropped by 10% in two patients, but resolved without need for manual ventilation. All other reported AEs were consistent with the known safety profile of dexmedetomidine. Two of the 78 patients in the efficacy-evaluable population met all sedation efficacy criteria. Dexmedetomidine was well-tolerated in pediatric patients undergoing procedure-type sedation.

Recent Insights Into Molecular Mechanisms of Propofol-Induced Developmental Neurotoxicity: Implications for the Protective Strategies

Mounting evidence has demonstrated that general anesthetics could induce developmental neurotoxicity, including acute widespread neuronal cell death, followed by long-term memory and learning abnormalities. Propofol is a commonly used intravenous anesthetic agent for the induction and maintenance of anesthesia and procedural and critical care sedation in children. Compared with other anesthetic drugs, little information is available on its potential contributions to neurotoxicity. Growing evidence from multiple experimental models showed a similar neurotoxic effect of propofol as observed in other anesthetic drugs, raising serious concerns regarding pediatric propofol anesthesia. The aim of this review is to summarize the current findings of propofol-induced developmental neurotoxicity. We first present the evidence of neurotoxicity from animal models, animal cell culture, and human stem cell-derived neuron culture studies. We then discuss the mechanism of propofol-induced developmental neurotoxicity, such as increased cell death in neurons and oligodendrocytes, dysregulation of neurogenesis, abnormal dendritic development, and decreases in neurotrophic factor expression. Recent findings of complex mechanisms of propofol action, including alterations in microRNAs and mitochondrial fission, are discussed as well. An understanding of the toxic effect of propofol and the underlying mechanisms may help to develop effective novel protective or therapeutic strategies for avoiding the neurotoxicity in the developing human brain.

Cucurbitacin E induces apoptosis of human prostate cancer cells via cofilin-1 and mTORC1

Cucurbitacin E is an important member of the cucurbitacin family and exhibits inhibitory effects in various types of cancer. Cucurbitacin is a potential antineoplastic drug; however, its anticancer effect in human prostate cancer (PC) remains unknown. The aim of the present study was to determine whether the effect of cucurbitacin E on the cell viability and apoptosis of the human PC cell line, LNCaP, was mediated by cofilin-1- and mammalian target of rapamycin (mTOR). The results of the present study demonstrated that cucurbitacin E significantly exhibited cytotoxicity, suppressed cell viability (P<0.0001) and induced apoptosis (P=0.0082) in LNCaP cells. In addition, it was demonstrated that treatment with cucurbitacin E significantly induced cofilin-1 (P=0.0031), p-mTOR (P=0.0022), AMP-activated protein kinase (AMPK; P=0.0048), cellular tumor antigen p53 (p53; P=0.0018) and caspase-9 (P=0.0026) protein expression in LNCaP cells, suggesting that cucurbitacin E exerts its effects on LNCaP cells through cofilin-1, mTOR, AMPK, p53 and caspase-9 signaling. These results suggested that cucurbitacin E maybe used as a therapeutic agent in the treatment of human PC.

Dexmedetomidine mitigates isoflurane-induced neurodegeneration in fetal rats during the second trimester of pregnancy

Dexmedetomidine has significant neuroprotective effects. However, whether its protective effects can reduce neurotoxicity caused by isoflurane in fetal brain during the second trimester of pregnancy remains unclear. In this study, timed-pregnancy rats at gestational day 14 spontaneously inhaled 1.5% isoflurane for 4 hours, and were intraperitoneally injected with dexmedetomidine at dosages of 5, 10, 20, and 20 μg/kg 15 minutes before inhalation and after inhalation for 2 hours. Our results demonstrate that 4 hours after inhaling isoflurane, 20 μg/kg dexmedetomidine visibly mitigated isoflurane-induced neuronal apoptosis, reversed downregulation of brain-derived neurotrophic factor expression, and lessened decreased spatial learning and memory ability in adulthood in the fetal rats. Altogether, these findings indicate that dexmedetomidine can reduce neurodegeneration induced by isoflurane in fetal rats during the second trimester of pregnancy. Further, brain-derived neurotrophic factor participates in this process.