Clonidine abolishes the adverse effects on apoptosis and behaviour after neonatal ketamine exposure in mice

The alpha2-adrenoceptor agonist clonidine protects against hypoxic-ischemic brain damage in neonatal mice through the Nrf2/NF-κB signaling pathway

Neonatal hypoxic-ischemic brain damage (HIBD) is a severe condition closely associated with neuroinflammation and oxidative stress. Clonidine, a selective α2-adrenergic receptor agonist, is known for its anti-inflammatory and antioxidant properties. Despite these recognized therapeutic benefits, the exact mechanisms by which clonidine exerts its effects in the context of HIBD are not fully understood. This study was designed to thoroughly investigate the impact of clonidine on HIBD-induced neuronal injury and to clarify its underlying mechanism of action. We employed a neonatal mouse model of HIBD to meticulously assess the effects of clonidine on neuronal injury, apoptosis, inflammation, and oxidative stress markers. In addition, we conducted extensive in vitro studies to evaluate the neuroprotective effects of clonidine on primary hippocampal neuronal cells, utilizing advanced techniques such as the Cell Counting Kit-8 (CCK-8), flow cytometry, enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay, and western blotting. Furthermore, we explored the regulatory effects of clonidine on the nuclear factor erythroid 2-related factor (Nrf2)/nuclear factor-κB (NF-κB) signaling pathway through a combination of in vivo and in vitro experiments. The results showed that clonidine significantly reduced cerebral infarction, neuronal damage, and apoptosis in HIBD mice. It also alleviated neuroinflammation and oxidative stress, improved cell viability, and reduced neuronal injury following oxygen-glucose deprivation/reoxygenation (OGD/R). The neuroprotective effects of clonidine were linked to the activation of the Nrf2/heme oxygenase-1 (HO-1) pathway and the inhibition of the NF-κB pathway. Overall, clonidine exhibited neuroprotective properties in HIBD by reducing neuroinflammation and oxidative stress, likely through the modulation of the Nrf2/NF-κB signaling pathway.

Clonidine as Monotherapy for Neonatal Opioid Withdrawal Syndrome: A Randomized Trial

OBJECTIVE

We sought to determine whether clonidine, a non-opioid α-2-adrenergic agonist, would effectively treat neonatal opioid withdrawal syndrome (NOWS).

METHODS

This was an intention-to-treat randomized clinical trial. Enrollment criteria included prenatal opioid exposure, age ≤7 days, gestational age ≥35 weeks, no other medical condition, and need for pharmacotherapy. Primary outcomes were length of treatment and neurobehavioral performance.

RESULTS

A total of 1107 patients were screened for enrollment (645 ineligible, 91 parents or staff unavailable, 216 declined, 155 consented). Of 155 infants, 120 required treatment and were randomized to receive oral clonidine (n = 60) at 1 µg/kg/dose or morphine (n = 60), 0.06 mg/kg/dose, every 3 hours. Infants with no improvement had their doses increased by 25% of the initial dose every 12 to 24 hours. Those without improvement by the fourth dose increase, received adjunct therapy. Length of treatment did not differ between morphine and clonidine, with median (95% confidence interval [CI]) days, respectively, of 15 (13-17) and 17 (15-19), P = .48. More clonidine-treated infants (45%) needed adjunct therapy versus 10% in the morphine group, adjusted odds ratio (95% CI) = 8.85 (2.87-27.31). After treatment completion, the NICU Network Neurobehavioral Scales summary scores did not differ between clonidine-treated and morphine-treated infants.

CONCLUSIONS

Length of pharmacologic treatment and final neurobehavioral performance were not significantly different between the clonidine- and morphine-treated groups. Clonidine appears to be an effective non-opioid medication to treat NOWS. Future studies are needed to determine the optimal clonidine dosage for a quicker response and obviation of adjunct therapy.

Metformin attenuates sevoflurane-induced neurogenesis damage and cognitive impairment: involvement of the Nrf2/G6PD pathway

Anesthetics such as sevoflurane are commonly administered to infants and children. However, the possible neurotoxicity caused by prolonged or repetitive exposure to it should be a concern. The neuroprotective effects of metformin are observed in many models of neurological disorders. In this study, we investigated whether metformin could reduce the developmental neurotoxicity induced by sevoflurane exposure in neonatal rats and the potential mechanism. Postnatal day 7 (PND 7) Sprague-Dawley rats and neural stem cells (NSCs) were treated with normal saline or metformin before sevoflurane exposure. The Morris water maze (MWM) was used to observe spatial memory and learning at PND 35-42. Immunofluorescence staining was used to detect neurogenesis in the subventricular zone (SVZ) of the lateral ventricle and the subgranular zone (SGZ) of the dentate gyrus at PND 14. MTT assays, immunofluorescence staining, and TUNEL staining were used to assess the viability, proliferation, differentiation, and apoptosis of NSCs. Western blotting and ELISA were used to assess the protein expression of cleaved caspase-3, nuclear factor erythroid 2-related factor 2 (Nrf2), and glucose-6-phosphate dehydrogenase (G6PD) pathway-related molecules. Exposure to sevoflurane resulted in late cognitive defects, impaired neurogenesis in both the SVZ and SGZ, reduced NSC viability and proliferation, increased NSC apoptosis, and decreased protein expression of G6PD in vitro. Metformin pretreatment attenuated sevoflurane-induced cognitive functional decline and neurogenesis inhibition. Metformin pretreatment also increased the protein expression of Nrf2 and G6PD. However, treatment with the Nrf2 inhibitor, ML385 or the G6PD inhibitor, dehydroepiandrosterone (DHEA) reversed the protective effect of metformin on sevoflurane-induced NSC damage in vitro. Our findings suggested that metformin could reduce sevoflurane-induced neurogenesis damage and neurocognitive defects in the developing rat brain by influencing the Nrf2/G6PD signaling pathways.

Effects of recurrent ketamine exposure on brain histopathology in juvenile rats

BACKGROUND

Ketamine (KET) is a commonly used anesthetic agent. However, several previous studies reported that KET leads to neuronal damage in neurodevelopmental stages and has neuroprotective effects. The present experimental study aimed to determine the undesirable histopathological effects of KET in the cerebral cortex, striatum, and hippocampus after recurrent KET administration in juvenile rats.

METHODS

After ethical approval was obtained, 32 juvenile male Wistar Albino rats were randomized into four groups: 1 mg/kg serum saline intraperitoneally (i.p.), 5 mg/kg KET i.p., 20 mg/kg KET i.p., and 50 mg/kg KET i.p. KET was administered for three consecutive days at three-h intervals in three doses. Ten days after the last KET dose, the rats were sacrificed. Cerebral hemispheres were fixed. Hematoxylin and eosin stain was used for morphometric analysis. Hippocampi were evaluated by immunohistochemistry with anticleaved caspase-3 antibodies. Statistical analysis was conducted with SPSS 21 software using the ANOVA test and Bonferroni post hoc analysis method.

RESULTS

The experimental study findings revealed no difference between the groups' cell counts or sizes in cortical morphometry. No degenerative changes were observed in pyramidal and granular cells in the striatum. Mild gliosis was observed in the 20 mg/kg and 50 mg/kg KET administration groups. Immuno-histo-chemical analysis was conducted to determine apoptosis in the CA1 region of the hippocampus and revealed that caspase-3 positivity increased with the KET dose. However, there was no statistical difference between the groups. While it was lower than the control group in the 5 mg/kg KET group, it was similar to the control group in the 20 mg/kg KET group and higher in the 50 mg/kg KET group (p > 0.05).

DISCUSSION

: Repetitive KET exposure did not significantly affect juvenile cerebral morphology and apoptosis in hippocampal cells.

Serotonin Toxicity Versus Withdrawal: Clonidine One Size Fits All?

Serotonin discontinuation syndrome (SDS) can result in a constellation of symptoms exhibited by infants exposed to selective serotonin reuptake inhibitors or other psychotropic drugs during pregnancy. Currently, there is no consensus regarding the pharmacologic management of SDS. We report our experience with clonidine for the management of a term infant with poor neonatal adaption. The infant exhibited biphasic symptoms of acute toxicity at birth and a plateauing of symptoms, followed by subsequent withdrawal symptomatology requiring the use of clonidine in doses up to 4 mcg/kg/dose every 3 hours for control of symptoms. The 38-week gestation Caucasian male infant was born to a mother with major depressive disorder, which was managed with sertraline, trazodone, venlafaxine, and buspirone throughout her pregnancy. The infant exhibited severe hypertonia at delivery and continued to have hypertonia, tremors, hypoglycemia, and feeding issues upon admission to the NICU. The initial Modified Finnegan Neonatal Abstinence scores were extremely elevated, and clonidine was started at 1 mcg/kg/dose every 3 hours and then the dose was titrated up to 4 mcg/kg/dose. This is the first report documenting the use of clonidine to manage serotonin toxicity at birth followed by subsequent neonatal withdrawal associated with maternal antidepressant drug use during pregnancy.

Opioids and alpha-2-agonists for analgesia and sedation in newborn infants: protocol of a systematic review

BACKGROUND

Hospitalized newborn infants may require analgesia and sedation either for the management of procedural pain, during or after surgery, and other painful conditions. The benefits and harms of opioids administered at different doses and routes of administration have been reported in numerous trials and systematic reviews. The use of alpha-2-agonists such as clonidine and dexmedetomidine in newborn infants is more recent, and they might be prescribed to reduce the total amount of opioids which are thought to have more side effects. Moreover, alpha-2-agonists might play an important role in the management of agitation and discomfort.

METHODS

We will conduct a systematic review and meta-analysis on the use of opioids, alpha-2-agonists, or the combination of both drugs. We will include randomized controlled trials to assess benefits and harms and observational studies to assess adverse events and pharmacokinetics; preterm and term infants; studies on any opioids or alpha-2-agonists administered for any indication and by any route except spinal, intraosseous, or administration for nerve blocks and wound infusions. The use of opioids or alpha-2-agonists will be compared to no intervention; placebo with normal saline or other non-sedative, non-analgesic drug; control with oral sugar solution or non-pharmacological intervention; same drug of different dose or route; or a different drug (not limiting to opioids and alpha-2-agonists) or combinations of such drugs. The primary outcomes for this review will be all-cause mortality during initial hospitalization and hypotension requiring medical therapy. We will conduct a search in the following databases: The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE, Embase, and CINAHL. Two review authors will independently screen records for inclusion, undertake data abstraction using a data extraction form and assess the risk of bias of all included trials using the Cochrane "Risk of bias" tool.

DISCUSSION

This systematic review will summarize and update our knowledge about neonatal analgesia and sedation including pharmacokinetics/pharmacodynamics, and provide a platform for developing evidence-based guidelines that we can immediately apply to our clinical practice.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO 2020 CRD42020170852.

Clonidine for pain in non-ventilated infants

BACKGROUND

Critically ill newborn infants undergo a variety of painful procedures or experience a variety of painful conditions during their early life in the neonatal unit. In the critically ill paediatric and neonatal population, clonidine is prescribed as an adjunct to opioids or benzodiazepines aiming to reduce the doses of these drugs that are required for analgesia or sedation, or to facilitate weaning from mechanical ventilation. It has been shown that clonidine premedication might have a positive effect on postoperative pain in children.

OBJECTIVES

To assess the benefit and harms of clonidine for the prevention or treatment of procedural pain; postoperative pain; or pain associated with clinical conditions in non-ventilated neonates.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the CENTRAL, MEDLINE via PubMed, Embase, and CINAHL to December 2018. We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. We ran an updated search from 1 January 2018 to 11 March 2020 in CENTRAL via CRS Web, MEDLINE via Ovid, and CINAHL via EBSCOhost.

SELECTION CRITERIA

Randomised controlled trials, quasi-randomised controlled trials, and cluster trials comparing clonidine to placebo or no treatment, opioids, paracetamol, dexmedetomidine, or non-pharmacological pain-reducing interventions for the management of procedural pain, postoperative pain, and pain associated with clinical conditions in preterm and term newborns.

DATA COLLECTION AND ANALYSIS

Two review authors independently planned to extract data (e.g. number of participants, birth weight, gestational age, modality of administration, and dose of clonidine) and assess the risk of bias (e.g. adequacy of randomisation, blinding, completeness of follow-up). The primary outcome considered was pain: for procedural pain, the mean values of each analgesia scale assessed during the procedure and at one to two hours after the procedure; for postoperative pain and for pain associated with clinical conditions, the mean values of each analgesia scale assessed at 30 minutes, three hours, and 12 hours after the administration of the intervention. We planned to use the GRADE approach to assess the quality of evidence.

MAIN RESULTS

Our search strategy yielded 3383 references. Two review authors independently assessed all references for inclusion. We did not find any completed studies for inclusion. We excluded three trials where clonidine was administered for spinal anaesthesia.

AUTHORS' CONCLUSIONS

We did not find any studies that met our inclusion criteria and hence there is no evidence to recommend or refute the use of clonidine for the prevention or treatment of procedural or postoperative pain, or pain associated with clinical conditions in neonates.

Pharmacology of Common Analgesic and Sedative Drugs Used in the Neonatal Intensive Care Unit

In this review of analgesic and sedation medication in neonates, important classes of old and newer medications commonly used in the neonatal intensive care unit setting are discussed. In addition to drug metabolism, efficacy, and safety for individual drugs, new insights into multimodal analgesic approaches suggest ways in which multiple analgesic drug classes can be combined to maximize efficacy and minimize toxicity. Opiate pharmacogenetics and the potential for a precision therapeutics approach is explored, with a final description of gaps in knowledge and a call for future research of pain and sedation control in the neonatal population.

17β-Estradiol Treatment Attenuates Neurogenesis Damage and Improves Behavior Performance After Ketamine Exposure in Neonatal Rats

Ketamine exposure disturbed normal neurogenesis in the developing brain and resulted in subsequent neurocognitive deficits. 17β-estradiol provides robust neuroprotection in a variety of brain injury models in animals of both sexes and attenuates neurodegeneration induced by anesthesia agents. In the present study, we aimed to investigate whether 17β-estradiol could attenuate neonatal ketamine exposure-disturbed neurogenesis and behavioral performance. We treated 7-day-old (Postnatal day 7, PND 7) Sprague-Dawley rats and neural stem cells (NSCs) with either normal saline, ketamine, or 17β-estradiol before/after ketamine exposure, respectively. At PND 14, the rats were decapitated to detect neurogenesis in the subventricular zone (SVZ) and subgranular zone (SGZ) of the hippocampus by immunofluorescence staining. The proliferation, neuronal differentiation, and apoptosis of NSCs were assessed by immunohistochemistry method and TUNEL assay, respectively. The protein levels of cleaved caspase-3 in vivo in addition to GSK-3β and p-GSK-3β in vitro were examined by western blotting. Spatial learning and memory abilities were assessed by Morris water maze (MWM) test at PND 42–47. Ketamine exposure decreased cell proliferation in the SVZ and SGZ, inhibited NSC proliferation and neuronal differentiation, promoted NSC apoptosis and led to adult cognitive deficits. Furthermore, ketamine increased cleaved caspase-3 in vivo and decreased the expression of p-GSK-3β in vitro. Treatment with 17β-estradiol could attenuate ketamine-induced changes both in vivo and in vitro. For the first time we showed that 17β-estradiol alleviated ketamine-induced neurogenesis inhibition and cognitive dysfunction in the developing rat brain. Moreover, the protection of 17β-estradiol was associated with GSK-3β.

Effects on adult cognitive function after neonatal exposure to clinically relevant doses of ionising radiation and ketamine in mice

BACKGROUND

Radiological methods for screening, diagnostics and therapy are frequently used in healthcare. In infants and children, anaesthesia/sedation is often used in these situations to relieve the patients' perception of stress or pain. Both ionising radiation (IR) and ketamine have been shown to induce developmental neurotoxic effects and this study aimed to identify the combined effects of these in a murine model.

METHODS

Male mice were exposed to a single dose of ketamine (7.5 mg kg^-1 body weight) s.c. on postnatal day 10. One hour after ketamine exposure, mice were whole body irradiated with 50-200 mGy gamma radiation (¹³⁷Cs). Behavioural observations were performed at 2, 4 and 5 months of age. At 6 months of age, cerebral cortex and hippocampus tissue were analysed for neuroprotein levels.

RESULTS

Animals co-exposed to IR and ketamine displayed significant (P≤0.01) lack of habituation in the spontaneous behaviour test, when compared with controls and single agent exposed mice. In the Morris Water Maze test, co-exposed animals showed significant (P≤0.05) impaired learning and memory capacity in both the spatial acquisition task and the relearning test compared with controls and single agent exposed mice. Furthermore, in co-exposed mice a significantly (P≤0.05) elevated level of tau protein in cerebral cortex was observed. Single agent exposure did not cause any significant effects on the investigated endpoints.

CONCLUSION

Co-exposure to IR and ketamine can aggravate developmental neurotoxic effects at doses where the single agent exposure does not impact on the measured variables. These findings show that estimation of risk after paediatric low-dose IR exposure, based upon radiation dose alone, may underestimate the consequences for this vulnerable population.

Ketamine induces hippocampal apoptosis through a mechanism associated with the caspase-1 dependent pyroptosis

Ketamine, a pediatric anesthetic, is widely used in clinical practice. There was growing evidence showing that ketamine can promote neuronal death in developing brains of both humans and animals. In this study, we used in vivo neonatal and juvenile mouse models to induce ketamine-related neurotoxicity in the hippocampus. Active caspase-3 and -9 proteins, which are responsible for the release of cytochrome C, and the mitochondrial translocation of p53, which is associated with mitochondrial apoptosis, were found to be significantly up-regulated in the ketamine-induced hippocampal neurotoxicity. Furthermore, we demonstrated that the levels of pyroptosis-related proteins, including caspase-1 and -11, NOD-like receptor family, pyrin domain containing 3 (NLRP3), and IL-1β and IL-18, significantly increased after multiple doses of ketamine administration. We speculated that ketamine triggered the formation of NLRP3 and caspase-1 complex and its translocation to the mitochondria. In consistent with this, ketamine treatment was found to induce pyroptosis in mouse primary hippocampal neurons, which was characterized by increased pore formation and elevated lactate dehydrogenase release in mitochondria. Silencing caspase-1 with lentivirus-mediated short hairpin RNA (shRNA) significantly decreased the levels of not only pyroptosis-related proteins but also mitochondrial apoptosis-associated proteins in mouse primary hippocampal neurons. We conclude that caspase-1-dependent pyroptosis is an important event which may be an essential pathway involved in the mitochondria-associated apoptosis in ketamine-induced hippocampal neurotoxicity.

Pharmacotherapy for Neonatal Abstinence Syndrome: Choosing the Right Opioid or No Opioid at All

Neonatal abstinence syndrome (NAS) from in utero opioid exposure has reached epidemic levels in the United States. Although nonpharmacologic therapies form the foundation of care, many neonates require pharmacotherapy. Morphine represents the most widely used first-line agent and effectively treats the symptoms of withdrawal. However, methadone or buprenorphine may facilitate earlier discharge. Although phenobarbital is traditionally used when opioids fail, clonidine may be a more appropriate adjunctive agent to minimize negative neurodevelopmental impact. Consideration of the available data allows hospitals to generate effective pharmacologic strategies to manage NAS while further research continues.

Clonidine for sedation and analgesia for neonates receiving mechanical ventilation

BACKGROUND

Although routine administration of pharmacologic sedation or analgesia during mechanical ventilation in preterm neonates is not recommended, its use in clinical practice remains common. Alpha-2 agonists, mainly clonidine and dexmedetomidine, are used as adjunctive (or alternative) sedative agents alongside opioids and benzodiazepines. Clonidine has not been systematically assessed for use in neonatal sedation during ventilation.

OBJECTIVES

To assess whether clonidine administered to term and preterm newborn infants receiving mechanical ventilation reduces morbidity and mortality rates. To compare the intervention versus placebo, no treatment, and dexmedetomidine; and to assess the safety of clonidine infusion for potential harms.To perform subgroup analyses according to gestational age; birth weight; administration method (infusion or bolus therapy); dose, duration, and route of clonidine administration; and pharmacologic sedation as a co-intervention.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 12) in the Cochrane Library, MEDLINE via PubMed (1966 to January 10, 2017), Embase (1980 to January 10, 2017), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to January 10, 2017). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomized controlled trials and quasi-randomized trials.

SELECTION CRITERIA

We searched for randomized controlled trials, quasi-randomized controlled trials, and cluster trials comparing clonidine versus placebo, no treatment, or dexmedetomidine administered to term and preterm newborns receiving mechanical ventilation via an endotracheal tube.

DATA COLLECTION AND ANALYSIS

For the included trial, two review authors independently extracted data (e.g. number of participants, birth weight, gestational age, all-cause death during initial hospitalization, duration of respiratory support, sedation scale, duration of hospital stay) and assessed risk of bias (e.g. adequacy of randomization, blinding, completeness of follow-up). This review considered primary outcomes of all-cause neonatal death, all-cause death during initial hospitalization, and duration of mechanical ventilation in days.

MAIN RESULTS

One trial, which included 112 infants, met the inclusion criteria for this review. Term newborn infants on mechanical ventilation with the need for continuous analgesia and sedation with fentanyl and midazolam were eligible for enrollment during the first 96 hours of ventilation. Study authors administered clonidine 1 μg/kg/h or placebo on day 4 after intubation.We found no differences between the two groups in all-cause death during hospitalization (risk ratio [RR] 0.69, 95% confidence interval [CI] 0.12 to 3.98). The quality of the evidence supporting these findings is low owing to imprecision of the estimates (one study; few events). The median (interquartile range) duration of mechanical ventilation was 7.1 days (5.7 to 9.1 days) in the clonidine group and 5.8 days (4.9 to 7.9 days) in the placebo group, respectively (P = 0.070). Among secondary outcomes, we found no differences in terms of duration of stay in the intensive care unit. Sedation scale values (COMFORT) and analgesia scores (Hartwig) during the first 72 hours of infusion of study medication were lower in the clonidine group than in the placebo group.

AUTHORS' CONCLUSIONS

At present, evidence is insufficient to show the efficacy and safety of clonidine for sedation and analgesia in term and preterm newborn infants receiving mechanical ventilation.

Effects of sevoflurane and clonidine on acid base status and long-term emotional and cognitive outcomes in spontaneously breathing rat pups

Background

Numerous experiments in rodents suggest a causative link between exposure to general anaesthetics during brain growth spurt and poor long-lasting neurological outcomes. Many of these studies have been questioned with regard of their translational value, mainly because of extremely long anaesthesia exposure. Therefore, the aim of the present study was to assess the impact of a short sevoflurane anaesthesia, alone or combined with clonidine treatment, on respiratory function in spontaneously breathing rat pups and overall effects on long-lasting emotional and cognitive functions.

Methods

At postnatal day (PND) 7, male Sprague Dawley rat pups were randomized into four groups and exposed to sevoflurane for one hour, to a single dose of intraperitoneal clonidine or to a combination of both and compared to a control group. Blood gas analysis was performed at the end of sevoflurane anaesthesia and after 60 minutes from clonidine or saline injection. Emotional and cognitive outcomes were evaluated in different group of animals at infancy (PND12), adolescence (PND 30–40) and adulthood (PND 70–90).

Results

Rat pups exposed to either sevoflurane or to a combination of sevoflurane and clonidine developed severe hypercapnic acidosis, but maintained normal arterial oxygenation. Emotional and cognitive outcomes were not found altered in any of the behavioural task used either at infancy, adolescence or adulthood.

Conclusions

Sixty minutes of sevoflurane anaesthesia in newborn rats, either alone or combined with clonidine, caused severe hypercapnic acidosis in spontaneously breathing rat pups, but was devoid of long-term behavioural dysfunctions in the present setting.

Etomidate exposure in early infant mice (P10) does not induce apoptosis or affect behaviour

BACKGROUND

Numerous animal studies have shown that all commonly used intravenous anaesthetic drugs and volatile agents may cause neuronal apoptosis following exposure in early life. Most studies have focussed on detecting increased apoptosis but their methods are not always readily transferrable to humans. The lipid formulation of etomidate represents an alternative to the currently established intravenous anaesthetic agents but there is no animal or human data on apoptosis or long-term behavioural changes. The aim of our study was to investigate the effects of etomidate on cerebral neuronal apoptosis and long-term behavioural effects using an established mouse model that represents the clinically relevant period of anaesthesia during early infancy in humans.

METHODS

Six groups of 10 day old mice (P10) were injected with either etomidate 0.3, 3 or 10 mg/kg, propofol 60 mg/kg, ketamine 50 mg/kg or placebo only. Apoptosis in the cerebral cortex and hippocampus was assessed 24 h after treatment (activated caspase-3). Late behavioural effects were tested at 2 months of age (spontaneous activity in a new environment).

RESULTS

No evidence was found of differences in activated caspase 3-concentrations among the study groups. Significant late behavioural changes were only observed in the ketamine group.

CONCLUSION

A single dose of etomidate in early infant mice at P10 did not produce evidence of cerebral apoptosis or impaired adult motor behaviour.

Prospective multicentre randomised, double-blind, equivalence study comparing clonidine and midazolam as intravenous sedative agents in critically ill children: the SLEEPS (Safety profiLe, Efficacy and Equivalence in Paediatric intensive care Sedation) study

BACKGROUND

Children in paediatric intensive care units (PICUs) require analgesia and sedation but both undersedation and oversedation can be harmful.

OBJECTIVE

Evaluation of intravenous (i.v.) clonidine as an alternative to i.v. midazolam.

DESIGN

Multicentre, double-blind, randomised equivalence trial.

SETTING

Ten UK PICUs.

PARTICIPANTS

Children (30 days to 15 years inclusive) weighing ≤ 50 kg, expected to require ventilation on PICU for > 12 hours.

INTERVENTIONS

Clonidine (3 µg/kg loading then 0-3 µg/kg/hour) versus midazolam (200 µg/kg loading then 0-200 µg/kg/hour). Maintenance infusion rates adjusted according to behavioural assessment (COMFORT score). Both groups also received morphine.

MAIN OUTCOME MEASURES

Primary end point Adequate sedation defined by COMFORT score of 17-26 for ≥ 80% of the time with a ± 0.15 margin of equivalence. Secondary end points Percentage of time spent adequately sedated, increase in sedation/analgesia, recovery after sedation, side effects and safety data.

RESULTS

The study planned to recruit 1000 children. In total, 129 children were randomised, of whom 120 (93%) contributed data for the primary outcome. The proportion of children who were adequately sedated for ≥ 80% of the time was 21 of 61 (34.4%) - clonidine, and 18 of 59 (30.5%) - midazolam. The difference in proportions for clonidine-midazolam was 0.04 [95% confidence interval (CI) -0.13 to 0.21], and, with the 95% CI including values outside the range of equivalence (-0.15 to 0.15), equivalence was not demonstrated; however, the study was underpowered. Non-inferiority of clonidine to midazolam was established, with the only values outside the equivalence range favouring clonidine. Times to reach maximum sedation and analgesia were comparable hazard ratios: 0.99 (95% CI 0.53 to 1.82) and 1.18 (95% CI 0.49 to 2.86), respectively. Percentage time spent adequately sedated was similar [medians clonidine 73.8% vs. midazolam 72.8%: difference in medians 0.66 (95% CI -5.25 to 7.24)]. Treatment failure was 12 of 64 (18.8%) on clonidine and 7 of 61 (11.5%) on midazolam [risk ratio (RR) 1.63, 95% CI 0.69 to 3.88]. Proportions with withdrawal symptoms [28/60 (46.7%) vs. 30/58 (52.6%)] were similar (RR 0.89, 95% CI 0.62 to 1.28), but a greater proportion required clinical intervention in those receiving midazolam [11/60 (18.3%) vs. 16/58 (27.6%) (RR 0.66, 95% CI 0.34 to 1.31)]. Post treatment, one child on clonidine experienced mild rebound hypertension, not requiring intervention. A higher incidence of inotropic support during the first 12 hours was required for those on clonidine [clonidine 5/45 (11.1%) vs. midazolam 3/52 (5.8%)] (RR 1.93 95% CI 0.49 to 7.61).

CONCLUSIONS

Clonidine is an alternative to midazolam. Our trial-based economic evaluation suggests that clonidine is likely to be a cost-effective sedative agent in the PICU in comparison with midazolam (probability of cost-effectiveness exceeds 50%). Rebound hypertension did not appear to be a significant problem with clonidine but, owing to its effects on heart rate, specific cardiovascular attention needs to be taken during the loading and early infusion phase. Neither drug in combination with morphine provided ideal sedation, suggesting that in unparalysed patients a third background agent is necessary. The disappointing recruitment rates reflect a reluctance of parents to provide consent when established on a sedation regimen, and reluctance of clinicians to allow sedation to be studied in unstable critically ill children. Future studies will require less exacting protocols allowing enhanced recruitment.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN02639863.

FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 18, No. 71. See the NIHR Journals Library website for further project information.

Carbendazim exposure induces developmental, biochemical and behavioural disturbance in zebrafish embryos

Carbendazim is a widely used broad spectrum benzimidazole fungicide; however, its effects to non-target aquatic organisms are poorly studied. The aim of this study was to investigate the toxic effects of carbendazim to zebrafish early life stages at several levels of biological organization, including developmental, biochemical and behavioural levels. The embryo assay was done following the OECD guideline 236 and using a concentration range between 1.1 and 1.8mg/L. Lethal and developmental endpoints such as hatching, edemas, malformations, heart beat rate, body growth and delays were assessed in a 96h exposure. A sub-teratogenic range (from 0.16 to 500μg/L) was then used to assess effects at biochemical and behavioural levels. Biochemical markers included cholinesterase (ChE), glutathione-S-transferase (GST), lactate dehydrogenase (LDH) and catalase (CAT) and were assessed at 96h. The locomotor behaviour was assessed using an automated video tracking system at 120h. Carbendazim (96h-LC50 of 1.75mg/L) elicited several developmental anomalies in zebrafish embryos with EC50 values ranging from 0.85 to 1.6mg/L. ChE, GST and LDH activities were increased at concentrations equal or above 4μg/L. The locomotor assay showed to be extremely sensitive, detecting effects in time that larvae spent swimming at concentrations of 0.16μg/L and thus, being several orders of magnitude more sensitive that developmental parameters or lethality. These are ecological relevant concentrations and highlight the potential of behavioural endpoints as early warning signs for environmental stress. Further studies should focus on understanding how the behavioural disturbances measured in these types of studies translate into fitness impairment at the adult stage.

Perils of paediatric anaesthesia and novel molecular approaches: An evidence-based review

Evolution of anaesthesia has been largely helped by progress of evidence-based medicine. In spite of many advancements in anaesthesia techniques and availability of newer and safer drugs, much more needs to be explored scientifically for the development of anaesthesia. Over the last few years, the notion that the actions of the anaesthesiologist have only immediate or short-term consequences has largely been challenged. Evidences accumulated in the recent years have shown that anaesthesia exposure may have long-term consequences particularly in the extremes of ages. However, most of the studies conducted so far are in vitro or animal studies, the results of which have been extrapolated to humans. There have been confounding evidences linking anaesthesia exposure in the developing brain with poor neurocognitive outcome. The results of animal studies and human retrospective studies have raised concern over the potential detrimental effects of general anaesthetics on the developing brain. The purpose of this review is to highlight the long-term perils of anaesthesia in the very young and the potential of improving anaesthesia delivery with the novel molecular approaches.

Review: effects of anesthetics on brain circuit formation

The results of several retrospective clinical studies suggest that exposure to anesthetic agents early in life is correlated with subsequent learning and behavioral disorders. Although ongoing prospective clinical trials may help to clarify this association, they remain confounded by numerous factors. Thus, some of the most compelling data supporting the hypothesis that a relatively short anesthetic exposure can lead to a long-lasting change in brain function are derived from animal models. The mechanism by which such changes could occur remains incompletely understood. Early studies identified anesthetic-induced neuronal apoptosis as a possible mechanism of injury, and more recent work suggests that anesthetics may interfere with several critical processes in brain development. The function of the mature brain requires the presence of circuits, established during development, which perform the computations underlying learning and cognition. In this review, we examine the mechanisms by which anesthetics could disrupt brain circuit formation, including effects on neuronal survival and neurogenesis, neurite growth and guidance, formation of synapses, and function of supporting cells. There is evidence that anesthetics can disrupt aspects of all of these processes, and further research is required to elucidate which are most relevant to pediatric anesthetic neurotoxicity.

Dexmedetomidine provides neuroprotection: impact on ketamine-induced neuroapoptosis in the developing rat brain

BACKGROUND

Ketamine and dexmedetomidine are increasingly used in combination in pediatric patients. This study examined the hypothesis that dexmedetomidine attenuated ketamine-induced neurotoxicity.

METHODS

Neonatal rats were randomly divided into four groups (n=10, male 5, female 5). Group S+S received an equal volume of normal saline intraperitoneally and subcutaneously at an interval of 5 min. Group K+S received an intraperitoneal injection of 75 mg/kg ketamine followed by subcutaneous injection of normal saline 5 min later. Group S+D were given subcutaneously 25 μg/kg dexmedetomidine 5 min after injection of normal saline. Group K+D received a subcutaneous injection of 25 μg/kg dexmedetomidine 5 min after ketamine injection. The above drugs were given once daily for 3 days. Neuronal apoptosis in the CA1 region and the dentate gyrus of rats was examined by transferase dUTP nick end labeling (TUNEL) assays. Learning and memory abilities of 2-month old rats were examined by Morris water maze test. The results were analyzed by analysis of variance.

RESULTS

The percentage of TUNEL-positive cells in group K+S (CA1, 49.0±9.46 and dentate gyrus, 49.4±5.41) was markedly higher than that in group K+D (CA1, 37.2±5.54 and dentate gyrus, 35.2±5.06) (F=5.49, P<0.05 and F=13.51, P<0.001, respectively). Group K+S took significantly longer time and swimming distance to find the hidden platform on the fourth and fifth training days than group K+D (P<0.05). Moreover, group K+D spent considerably more time in the target quadrant than group K+S (P<0.05). Dexmedetomidine alone caused a small but statistically insignificant increase in neuronal apoptosis of the CA1 region and the dentate gyrus of neonatal rats compared with normal saline.

CONCLUSION

In conclusion, ketamine caused neuroapoptosis and impaired brain functions in the developing rat brain which can be effectively attenuated by dexmedetomidine. Dexmedetomidine alone was not neurotoxic to the developing brain.

17β-estradiol attenuates ketamine-induced neuroapoptosis and persistent cognitive deficits in the developing brain

Previous studies have demonstrated that the commonly used anesthetic ketamine can induce widespread neuroapoptosis in the neonatal brain and can cause persistent cognitive impairments as the animal matures. Therefore, searching for adjunctive neuroprotective strategies that inhibit ketamine-induced neuroapoptosis and persistent cognitive impairments is highly warranted. The primary goal of this study was to investigate the protective effect of 17β-estradiol against ketamine-induced neuroapoptosis and persistent cognitive impairments in adult rats. Starting from postnatal day 7, Sprague-Dawley male rat pups were given a daily administration of ketamine (75mg/kg, i.p.) or 17β-estradiol (600μg/kg, s.c.) in combination with ketamine (75mg/kg, i.p.). The animals were treated for three consecutive days. 24h after the last injection, the rats were decapitated, and the prefrontal cortex (PFC) was isolated to detect neuroapoptosis by cleaved caspase-3 immunohistochemistry and by using the TUNEL assay. The neuroactive steroid 17β-estradiol was quantified using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The protein levels of BDNF and pAkt were measured by western blot analysis. At two months of age (60 days), the learning and memory abilities were tested using the Morris water maze. The results showed that ketamine triggered significant neuroapoptosis in the neonatal PFC accompanied by the downregulation of 17β-estradiol, BDNF and pAkt. The co-administration of 17β-estradiol with ketamine attenuated these changes. Moreover, 17β-estradiol significantly reversed the learning and memory deficits observed at 60 days of age. In brief, our present data demonstrate that 17β-estradiol attenuates ketamine-induced neuroapoptosis and reverses long-term cognitive deficits in developing rats and thus may be a potential therapeutic and neuroprotective method for the treatment of neurodevelopmental disorders. This article is part of a Special Issue entitled SI: Brain and Memory.

Effects of COX inhibition and LPS on formalin induced pain in the infant rat

In the adult, immune and neural processes jointly modulate pain. During development, both are in transition and little is known about the role that the immune system plays in pain processing in infants and children. The objective of this study was to determine if inhibition or augmentation of the immune system would alter pain processing in the infant rat, as it does in the adult. In Experiment 1, rat pups aged 3, 10, or 21 (PN3, PN10, and PN21) days of age were pretreated with NS398 (selective cyclooxygenase (COX)-2 inhibitor) or SC560 (selective COX-1 inhibitor) and tested in the intraplantar formalin test to assess effects of COX inhibition on nociception. Neither drug had an effect on the behavioral response at PN3 or PN10 pups but both drugs attenuated nociceptive scores in PN21 pups. cFos expression in the spinal cord likewise was reduced only at PN21. In Experiment 2, pups were injected with lipopolysaccharide (LPS) prior to the formalin test at PN3 or PN21. LPS increased the nociceptive response more robustly at PN21 than at PN3, while increasing cytokine mRNA equally at both ages. The augmentation of pain responding at PN21 was largely during the late stages of the formalin test, as reported in the adult. These data support previous findings demonstrating late maturing immune modulation of nociceptive behaviors.

Existence of glia mitigated ketamine-induced neurotoxicity in neuron-glia mixed cultures of neonatal rat cortex and the glia-mediated protective effect of 2-PMPA

The present study compared ketamine-induced neurotoxicity in the neuron-glia mixed cultures and neuronal cultures and further explored the neuroprotective effect of the NAAG peptidase inhibitor 2-(phosphonomethyl) pentanedioic acid (2-PMPA). Firstly, Rosenfeld's staining and immunofluorescence staining of microtubule-associated protein 2 (MAP2) and glial fibrillary acidic protein (GFAP) were used to address the difference of morphology in the mixed cultures and neuronal cultures. Our results showed that neurons and astrocytes grew in good conditions. The ratio of neurons and astrocytes in the mixed cultures was around 1:1, and the purity of neurons in the neuronal cultures is 91.3%. Furthermore, ketamine was used to test the hypothesis that the presence of a higher proportion of glia in the mixed cultures would be protective against ketamine-induced neurotoxicity in the mixed cultures compared with neuronal cultures. The results showed that ketamine-induced morphological changes, cell viability decrease and lactate dehydrogenase (LDH) levels increase were significantly mitigated in neuron-glia mixed cultures compared with neuronal cultures. Furthermore, 2-PMPA was included to further explore efficient protective drug for ketamine-induced neurotoxicity. Our results showed that 2-PMPA reduced ketamine-induced decrease of cell viability and increase of LDH levels in the mixed cultures but not in the neuronal cultures. Further morphological changes of neurons and astrocytes also indicated that 2-PMPA could improve ketamine damaged neurons in the mixed cultures instead of neuronal cultures. These results indicate that glia protect neurons from ketamine-induced neurotoxicity. These data further suggest that glia mediate the neuroprotective effect of 2-PMPA and 2-PMPA has the potential to treat ketamine-induced neurotoxicity in vivo. Delineating the mechanisms underlying the communication between neurons and glia and the neuroprotective effects of 2-PMPA in the mixed cultures to ketamine-induced neurotoxicity require further investigation.

Anesthesia and the developing brain: relevance to the pediatric cardiac surgery

Anesthetic neurotoxicity has been a hot topic in anesthesia for the past decade. It is of special interest to pediatric anesthesiologists. A subgroup of children potentially at greater risk for anesthetic neurotoxicity, based on a prolonged anesthetic exposure early in development, are those children receiving anesthesia for surgical repair of congenital heart disease. These children have a known risk of neurologic deficit after cardiopulmonary bypass for surgical repair of congenital heart disease. Yet, the type of anesthesia used has not been considered as a potential etiology for their neurologic deficits. These children not only receive prolonged anesthetic exposure during surgical repair, but also receive repeated anesthetic exposures during a critical period of brain development. Their propensity to abnormal brain development, as a result of congenital heart disease, may modify their risk of anesthetic neurotoxicity. This review article provides an overview of anesthetic neurotoxicity from the perspective of a pediatric cardiac anesthesiologist and provides insight into basic science and clinical investigations as it relates to this unique group of children who have been studied over several decades for their risk of neurologic injury.

Effect of intravenous patient controlled ketamine analgesiaon postoperative pain in opium abusers

Background:

Acutepostoperative pain is among the worst experience that patient scan undergo, and many analgesics have been used to suppress it; especially in chronic opium abusers. Ketamine is an N-methyl-D-aspartate antagonist analgesic, having both anesthetic and analgesic properties, which are not affected to the same extent in chronic opium abusers.

Objectives:

In this study, we assessed the analgesic effects of ketamine added to morphine as a patient-controlled analgesia method for acute pain management, compared with a placebo, inchronic maleopium abusers.

Patients and Methods:

After institutional review board approval for ethical considerations, a randomized double-blinded placebo controlled clinical trial was conducted. A total of 140 male patients aged 18-65 years, undergoing orthopedic surgery, were entered into the study after matching inclusion and exclusion criteria. All patients received the same anesthesia method; while the first group received ketamine (1mg/mL) and morphine (0.5 mg/mL) as a patient-controlled analgesia (70 patients), the second group received morphine (0.5 mg/mL) plus normal saline (70 patients). P value less than 0.05 was considered statistically significant.

Results:

The ketamine and morphine group of patients experienced less postoperative pain and required less postoperative rescue analgesia. However, the unwanted postoperative side effects were nearly the same; although increased levels of postoperative nausea and vomiting were observed in the ketamine and morphine group

Conclusions:

This study demonstrated improved analgesic effects after using intravenous patient controlled analgesia with ketamine on postoperative pain in opium abusers.

The role of anesthetic drugs in liver apoptosis

CONTEXT

The modern practice of anesthesia is highly dependent ona group of anesthetic drugs which many of them are metabolized in the liver.

EVIDENCE ACQUISITION

The liver, of course, usually tolerates this burden. However, this is not always an unbroken rule. Anesthetic induced apoptosis has gained great concern during the last years; especially considering the neurologic system.

RESULTS

However, we have evidence that there is some concern regarding their effects on the liver cells. Fortunately not all the anesthetics are blamed and even some could be used safely, based on the available evidence.

CONCLUSIONS

Besides, there are some novel agents, yet under research, which could affect the future of anesthetic agents' fate regarding their hepatic effects.

Impact of anaesthetics and surgery on neurodevelopment: an update

Accumulating preclinical and clinical evidence suggests the possibility of neurotoxicity from neonatal exposure to general anaesthetics. Here, we review the weight of the evidence from both human and animal studies and discuss the putative mechanisms of injury and options for protective strategies. Our review identified 55 rodent studies, seven primate studies, and nine clinical studies of interest. While the preclinical data consistently demonstrate robust apoptosis in the nervous system after anaesthetic exposure, only a few studies have performed cognitive follow-up. Nonetheless, the emerging evidence that the primate brain is vulnerable to anaesthetic-induced apoptosis is of concern. The impact of surgery on anaesthetic-induced brain injury has not been adequately addressed yet. The clinical data, comprising largely retrospective cohort database analyses, are inconclusive, in part due to confounding variables inherent in these observational epidemiological approaches. This places even greater emphasis on prospective approaches to this problem, such as the ongoing GAS trial and PANDA study.

Newly postulated neurodevelopmental risks of pediatric anesthesia: theories that could rock our world

PURPOSE

General anesthetics can induce apoptotic neurodegeneration and subsequent maladaptive behaviors in animals. Retrospective human studies suggest associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes. The relevance of animal data to clinical practice is unclear and to our knowledge the causality underlying observed associations in humans is unknown. We reviewed newly postulated neurodevelopmental risks of pediatric anesthesia and discuss implications for the surgical care of children.

MATERIALS AND METHODS

We queried the MEDLINE®/PubMed® and EMBASE® databases for citations in English on pediatric anesthetic neurotoxicity with the focus on references from the last decade.

RESULTS

Animal studies in rodents and primates demonstrate apoptotic neuropathology and subsequent maladaptive behaviors after exposure to all currently available general anesthetics with the possible exception of α2-adrenergic agonists. Similar adverse pathological and clinical effects occur after untreated pain. Anesthetic neurotoxicity in animals develops only after exposure above threshold doses and durations during a critical neurodevelopmental window of maximal synaptogenesis in the absence of concomitant painful stimuli. Anesthetic exposure outside this window or below threshold doses and durations shows no apparent neurotoxicity, while exposure in the context of concomitant painful stimuli is neuroprotective. Retrospective human studies suggest associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes, particularly after multiple exposures. The causality underlying the associations is unknown. Ongoing investigations may clarify the risks associated with current practice.

CONCLUSIONS

Surgical care of all patients mandates appropriate anesthesia. Neurotoxic doses and the duration of anesthetic exposure in animals may have little relevance to clinical practice, particularly surgical anesthesia for perioperative pain. The causality underlying the observed associations between early anesthetic exposure and subsequent adverse neurodevelopmental outcomes is unknown. Anesthetic exposure may be a marker of increased risk. Especially in young children, procedures requiring general anesthesia should be performed only as necessary and general anesthesia duration should be minimized. Alternatives to general anesthesia and the deferral of elective procedures beyond the first few years of life should be considered, as appropriate. Participation in ongoing efforts should be encouraged to generate further data.