Update on neonatal anesthetic neurotoxicity: insight into molecular mechanisms and relevance to humans

Deciphering the dual role of N-methyl-D-Aspartate receptor in postoperative cognitive dysfunction: A comprehensive review

Postoperative cognitive dysfunction (POCD) is a common complication following surgery, adversely impacting patients' recovery, increasing the risk of negative outcomes, prolonged hospitalization, and higher mortality rates. The N-methyl-D-aspartate (NMDA) receptor, crucial for learning, memory, and synaptic plasticity, plays a significant role in the development of POCD. Various perioperative factors, including age and anesthetic use, can reduce NMDA receptor function, while surgical stress, inflammation, and pain may lead to its excessive activation. This review consolidates preclinical and clinical research to explore the intricate relationship between perioperative factors affecting NMDA receptor functionality and the onset of POCD. It discusses the influence of aging, anesthetic administration, perioperative injury, pain, and inflammation on the NMDA receptor-related pathophysiology of POCD. The comprehensive analysis presented aims to identify effective treatment targets for POCD, contributing to the improvement of patient outcomes post-surgery.

Neonatal Isoflurane Exposure in Rats Impairs Short-Term Memory, Cell Viability, and Glutamate Uptake in Slices of the Frontal Cerebral Cortex, But Not the Hippocampus, in Adulthood

Neonatal exposure to general anesthetics has been associated with neurotoxicity and morphologic changes in the developing brain. Isoflurane is a volatile anesthetic widely used in pediatric patients to induce general anesthesia, analgesia, and perioperative sedation. In the present study, we investigated the effects of a single neonatal isoflurane (3% in oxygen, 2 h) exposure in rats at postnatal day (PND) 7, in short-term (24 h - PND8) and long-term (adulthood) protocols. In PND8, ex vivo analysis of hippocampal and frontal cortex slices evaluated cell viability and susceptibility to in vitro glutamate challenge. In adult rats, behavioral parameters related to anxiety-like behavior, short-term memory, and locomotor activity (PND60-62) and ex vivo analysis of cell viability, membrane permeability, glutamate uptake, and susceptibility to in vitro glutamate challenge in hippocampal and cortical slices from PND65. A single isoflurane (3%, 2 h) exposure at PND7 did not acutely alter cell viability in cortical and hippocampal slices of infant rats (PND8) per se and did not alter slice susceptibility to in vitro glutamate challenge. In rat's adulthood, behavioral analysis revealed that the neonatal isoflurane exposure did not alter anxiety-like behavior and locomotor activity (open field and rotarod tests). However, isoflurane exposure impaired short-term memory evaluated in the novel object recognition task. Ex vivo analysis of brain slices showed isoflurane neonatal exposure selectively decreased cell viability and glutamate uptake in cortical slices, but it did not alter hippocampal slice viability or glutamate uptake (PND65). Isoflurane exposure did not alter in vitro glutamate-induced neurotoxicity to slices, and isoflurane exposure caused no significant long-term damage to cell membranes in hippocampal or cortical slices. These findings indicate that a single neonatal isoflurane exposure did not promote acute damage; however, it reduced cortical, but not hippocampal, slice viability and glutamate uptake in the adulthood. Additionally, behavioral analysis showed neonatal isoflurane exposure induces short-term recognition memory impairment, consolidating that neonatal exposure to volatile anesthetics may lead to behavioral impairment in the adulthood, although it may damage brain regions differentially.

Sevoflurane diminishes neurogenesis and promotes ferroptosis in embryonic prefrontal cortex via inhibiting nuclear factor-erythroid 2-related factor 2 expression

OBJECTIVE

Prenatal sevoflurane exposure may pose neurotoxicity to embryonic brain development and lead to cognitive dysfunction in offspring, but the underlying mechanism is still unclear. We aimed to investigate whether sevoflurane could cause neurogenesis abnormality and ferroptosis in embryonic prefrontal cortex (PFC) and to identify the role of nuclear factor-erythroid 2-related factor 2 (Nrf2) in the sevoflurane-related neurotoxicity.

METHODS

We used the rodents and primary neural stem cells to examine whether sevoflurane impacted proliferation, differentiation, ferroptosis and apoptosis in the neural stem cells of embryonic PFC. In addition, the expression of Nrf2 and the intensity of reactive oxygen species (ROS) were also assessed to explore the underlying molecular mechanism.

RESULTS

Our results showed that sevoflurane exposure in third trimester could lead to neurogenesis inhibition and ferroptosis in-vivo embryonic PFC, with little influence on apoptosis. Moreover, a significant decrease in the expression of Nrf2 as well as an increase in ROS accumulation were also found in neural stem cells after sevoflurane anesthesia.

CONCLUSION

We conclude that Nrf2-related neurogenesis inhibition and ferroptosis are a central mechanism contributing to sevoflurane-induced neurotoxicity in embryonic brain. The results of the present study are the first to demonstrate that ferroptosis and the expression of Nrf2 are involved in sevoflurane-related neurotoxicity in embryonic brain, which provides new vision for consideration in anesthesia-associated neurological abnormalities.

Anesthesia and neurotoxicity study design, execution, and reporting in the nonhuman primate: A systematic review

BACKGROUND

Concern for a role of anesthesia in neurotoxicity in children originated from neonatal rodent and nonhuman primate (NHP) models, yet prospective clinical studies have largely not supported this concern. The goal of this study was to conduct an objective assessment of published NHP study rigor in design, execution, and reporting.

METHODS

A MEDLINE search from 2005 to December 2021 was performed. Inclusion criteria included full-length original studies published in English under peer-reviewed journals. We documented experimental parameters on anesthetic dosing, monitoring, vitals, and experimental outcomes.

RESULTS

Twenty-three manuscripts were included. Critical issues identified in study design included: lack of blinding in data acquisition (57%) and analysis (100%), supratherapeutic (4-12 fold) maintenance dosing in 22% of studies, lack of sample size justification (91%) resulting in a mean (SD) sample size of 6 (3) animals per group. Critical items identified in the conduct and reporting of studies included: documentation of anesthesia provider (0%), electrocardiogram monitoring (35%), arterial monitoring (4%), spontaneous ventilation employed (35%), failed intubations resulting in comingling ventilated and unventilated animals in data analysis, inaccurate reporting of failed intubation, and only 50% reporting on survival. Inconsistencies were noted in drug-related induction of neuroapoptosis and region of occurrence. Further, 67%-100% of behavior outcomes were not significantly different from controls.

CONCLUSIONS

Important deficits in study design, execution, and reporting were identified in neonatal NHP studies. These results raise concern for the validity and reliability of these studies and may explain in part the divergence from results obtained in human neonates.

Neuron-Glia Crosstalk Plays a Major Role in the Neurotoxic Effects of Ketamine via Extracellular Vesicles

Background: There is a compelling evidence from animal models that early exposure to clinically relevant general anesthetics (GAs) interferes with brain development, resulting in long-lasting cognitive impairments. Human studies have been inconclusive and are challenging due to numerous confounding factors. Here, we employed primary human neural cells to analyze ketamine neurotoxic effects focusing on the role of glial cells and their activation state. We also explored the roles of astrocyte-derived extracellular vesicles (EVs) and different components of the brain-derived neurotrophic factor (BDNF) pathway.

Methods: Ketamine effects on cell death were analyzed using live/dead assay, caspase 3 activity and PARP-1 cleavage. Astrocytic and microglial cell differentiation was determined using RT-PCR, ELISA and phagocytosis assay. The impact of the neuron-glial cell interactions in the neurotoxic effects of ketamine was analyzed using transwell cultures. In addition, the role of isolated and secreted EVs in this cross-talk were studied. The expression and function of different components of the BDNF pathway were analyzed using ELISA, RT-PCR and gene silencing.

Results: Ketamine induced neuronal and oligodendrocytic cell apoptosis and promoted pro-inflammatory astrocyte (A1) and microglia (M1) phenotypes. Astrocytes and microglia enhanced the neurotoxic effects of ketamine on neuronal cells, whereas neurons increased oligodendrocyte cell death. Ketamine modulated different components in the BDNF pathway: decreasing BDNF secretion in neurons and astrocytes while increasing the expression of p75 in neurons and that of BDNF-AS and pro-BDNF secretion in both neurons and astrocytes. We demonstrated an important role of EVs secreted by ketamine-treated astrocytes in neuronal cell death and a role for EV-associated BDNF-AS in this effect.

Conclusions: Ketamine exerted a neurotoxic effect on neural cells by impacting both neuronal and non-neuronal cells. The BDNF pathway and astrocyte-derived EVs represent important mediators of ketamine effects. These results contribute to a better understanding of ketamine neurotoxic effects in humans and to the development of potential approaches to decrease its neurodevelopmental impact.

Comparative Milestones in Rodent and Human Postnatal Central Nervous System Development

Within the substantially different time scales characterizing human and rodent brain development, key developmental processes are remarkably preserved. Shared processes include neurogenesis, myelination, synaptogenesis, and neuronal and synaptic pruning. In general, altricial rodents experience greater central nervous system (CNS) immaturity at birth and accelerated postnatal development compared to humans, in which protracted development of certain processes such as neocortical myelination and synaptic maturation extend into adulthood. Within this generalization, differences in developmental rates of various structures must be understood to accurately model human neurodevelopmental toxicity in rodents. Examples include greater postnatal neurogenesis in rodents, particularly within the dentate gyrus of rats, ongoing generation of neurons in the rodent olfactory bulb, differing time lines of neurotransmitter maturation, and differing time lines of cerebellar development. Comparisons are made to the precocial guinea pig and the long-lived naked mole rat, which, like primates, experiences more advanced CNS development at birth, with more protracted postnatal development. Methods to study various developmental processes are summarized using examples of comparative postnatal injury in humans and rodents.

Prolonged ketamine exposure induces enhanced excitatory GABAergic synaptic activity in the anterior cingulate cortex of neonatal rats

Experimental studies have indicated that prolonged ketamine exposure in neonates at anesthetic doses causes neuronal apoptosis, which contributes to long-term impairments of learning and memory later in life. The neuronal excitotoxicity mediated by compensatory upregulation of N-methyl-d-aspartate receptors (NMDARs) is proposed to be the underlying mechanism. However, this view does not convincingly explain why excitotoxicity-related apoptotic injury develops selectively in immature neurons. We proposed that the GABA_A receptors (GABA_ARs)-mediated excitatory synaptic signaling due to high expression of the Na⁺-K⁺-2Cl^- co-transporter (NKCC1), occurring during the early neuronal development period, plays a distinct role in the susceptibility of immature neurons to ketamine-induced injury. Using whole-cell patch-clamp recordings from the forebrain slices containing the anterior cingulate cortex, we found that in vivo repeated ketamine administration significantly induced neuronal hyperexcitability in neonatal, but not adolescent, rats. Such hyperexcitability was accompanied by the increase both in GABA_AR- and NMDAR-mediated synaptic transmissions. An interference with the NKCC1 by bumetanide treatment completely reversed these enhanced effects of ketamine exposure and blocked GABA_AR-mediated postsynaptic current activity. Thus, these findings were significant as they showed, for the first time, that GABA_AR-mediated excitatory action may contribute distinctly to neuronal excitotoxic effects of ketamine on immature neurons in the developing brain.

Ketamine inhibits neuronal differentiation by regulating brain-derived neurotrophic factor (BDNF) signaling

Ketamine is widely used in pediatric anesthesia, perioperative sedation, and analgesia. Knowledge of anesthesia neurotoxicity in humans is currently limited by the difficulty of obtaining neurons and performing developmental toxicity studies in fetal and pediatric populations. However, mouse embryonic stem cells (mESCs) derived from embryos at the preimplantation stage demonstrate an unlimited ability to self-renew and generate different cell types and are a valuable tool for clinical research. Thus, in this study, a model was employed to investigate the mechanism by which ketamine (200 nM) influences the neuronal differentiation of mESCs. Mouse ESCs were treated with an anesthetic dose of ketamine, and neuronal differentiation was significantly inhibited on day 5. Downregulation of brain-derived neurotrophic factor (BDNF) by shRNA was found to have the same inhibitory effect. Furthermore, a rescue experiment indicated that BDNF overexpression markedly restored the neuronal differentiation inhibited by ketamine in the ketamine/BDNF group on day 5. Taken together, these data suggested that ketamine inhibited the neuronal differentiation of mESCs, possibly by interfering with BDNF. The results of the current study may provide novel ideas for preventing ketamine toxicity in the developing fetus.

Behavior and Regional Cortical BOLD Signal Fluctuations Are Altered in Adult Rabbits After Neonatal Volatile Anesthetic Exposure

Neonatal and infant exposure to volatile anesthetics has been associated with long-term learning, memory, and behavioral deficits. Although early anesthesia exposure has been linked to a number of underlying structural abnormalities, functional changes associated with these impairments remain poorly understood. To investigate the relationship between functional alteration in neuronal circuits and learning deficiency, resting state functional MRI (rsfMRI) connectivity was examined in adolescent rabbits exposed to general anesthesia as neonates (1 MAC isoflurane for 2 h on postnatal days P8, P11, and P14) and unanesthetized controls before and after training with a trace eyeblink classical conditioning (ECC) paradigm. Long-range connectivity was measured between several key regions of interest (ROIs), including primary and secondary somatosensory cortices, thalamus, hippocampus, and cingulate. In addition, metrics of regional BOLD fluctuation amplitudes and coherence, amplitude of low-frequency fluctuation (ALFF), fractional ALFF (fALFF), and regional homogeneity (ReHo) were calculated. Our results showed that the trace ECC learning rate was significantly lower in the anesthesia-exposed group. No anesthesia-related changes in long-range connectivity, fALFF, or ReHo were found between any ROIs. However, ALFF was significantly higher in anesthesia-exposed rabbits in the primary and secondary somatosensory cortices, and ALFF in those areas was a significant predictor of the learning performance for trace ECC. The absence of anesthesia-related changes in long-range thalamocortical connectivity indicates that functional thalamocortical input is not affected. Higher ALFF in the somatosensory cortex may indicate the developmental disruption of cortical neuronal circuits after neonatal anesthesia exposure, including excessive neuronal synchronization that may underlie the observed cognitive deficits.

Ketamine Alleviates Postoperative Depression-Like Symptoms in Susceptible Mice: The Role of BDNF-TrkB Signaling

Patients are more likely to suffer from central nervous system (CNS) complications after anesthesia and surgery. However, postoperative depression (POD) has not yet received sufficient attentions, and its pathogenesis and therapeutic strategies remain poorly understood. We here aimed to investigate whether brain derived neurotrophic factor (BDNF)-tropomyosin-related kinase B (TrkB) signaling plays an important role in POD. BDNF-TrkB signaling was altered in brain and peripheral tissues, including medial prefrontal cortex (mPFC), hippocampus, liver, and muscle, among control, POD susceptible, and resilient groups. Additionally, we demonstrated that 7,8-dihydroxyflavone (7,8-DHF), a TrkB agonist, could exert its pharmacologic property to alleviate POD-like symptoms. More importantly, ketamine, a non-competitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, also has significant antidepressant effects in POD model, associating with the improving effects on levels of BDNF-TrkB signaling in brain and peripheral tissues. Interestingly, the beneficial effects of ketamine on POD-like symptoms are fully attenuated by a TrkB antagonist. These findings suggest that abnormal expressions of BDNF-TrkB signaling in brain and peripheral tissues are implicated in the pathogenesis of POD, and that therapeutic agents targeting BDNF-TrkB, particularly ketamine, could favor the beneficial effects for POD.

Anesthesia Neurotoxicity in the Developing Brain: Basic Studies Relevant for Neonatal or Perinatal Medicine

Diagnostic and invasive procedures in premature infants may require general anesthesia. General anesthetics interfere with the development of the immature animal brain. Accelerated apoptosis, disturbed synaptogenesis, and cytoarchitecture are among the mechanisms suspected to underlie this phenomenon. The implications for humans are unknown. This article presents current suspected mechanisms of anesthesia-induced neurotoxicity and elaborates on the difficulties in translating results from animal research to human. Ethical considerations limit the conduct of such experiments in human neonates, but the use of animal models is still considered feasible. Vulnerable periods in brain development need further identification as do neurotoxic and neuroprotective interventions.

Laparoscopic Surgery in Infants Under Spinal Anesthesia Block: A Case Report of 3 Cases

Spinal anesthesia (SA) is a valuable alternative to general anesthesia in infants, but laparoscopic surgery is considered a contraindication in this age group. We report 3 cases of SA for inguinal hernia repairs. The contralateral inguinal region was explored by laparoscopic port placement and pneumoperitoneum through the surgical site. Ages ranged from 5 to 15 weeks, postconceptual age from 46 to 55 weeks, and weights from 4.0 to 6.6 kg. Spinal anesthetics were supplemented with intravenous dexmedetomidine. One patient experienced hypertension and tachycardia during insufflation with brief supplemental use of sevoflurane. Opioids were spared in 2 patients. Pain scores were low throughout. SA as a primary anesthetic may be used in pediatric laparoscopic procedures.

Surgical interventions and anesthesia in the 1st year of life for lower urinary tract obstruction

BACKGROUND

Patients with a prenatal diagnosis of lower urinary tract obstruction (LUTO) may undergo prenatal interventions, such as vesicoamniotic shunt (VAS) placement, as a temporary solution for relieving urinary tract obstruction. A recent FDA communication has raised awareness of the potential neurocognitive adverse effects of anesthesia in children. We hypothesized as to whether a prenatal LUTO staging system was predictive of the number of anesthesia events for prenatally diagnosed LUTO patients.

METHODS

We retrospectively reviewed the prenatal and postnatal clinical records for patients with prenatally diagnosed LUTO from 2012 to 2015. Patients were stratified by prenatal VAS status and by LUTO disease severity according to Ruano et al. (Ultrasound Obstet Gynecol. 2016).

RESULTS

31 patients were identified with a prenatal LUTO diagnosis, and postnatal records were available for 21 patients (seven patients in each stage). When combining prenatal and postnatal anesthesia, there was a significant difference in the number of anesthesia encounters by stage (1.6, 3.7, and 6.7 for Stage I, II, and III respectively, p = .034). Upon univariate analysis, higher gestational age (GA) at birth was associated with a decreased number of anesthesia events in the first year (p = .031).

CONCLUSIONS

The majority of infants with prenatally diagnosed LUTO will undergo postnatal procedures with general anesthesia exposure in the first year of life. Patients with higher prenatal LUTO severity experienced a higher number of both prenatal and postnatal anesthesia encounters. In addition, higher GA at birth was associated with fewer anesthesia encounters in the first year.

LEVEL OF EVIDENCE

This is a prognostic study with Level IV evidence.

Ferroptosis Contributes to Isoflurane Neurotoxicity

The underlying mechanisms of isoflurane neurotoxicity in the developing brain remain unclear. Ferroptosis is a recently characterized form of programmed cell death distinct from apoptosis or autophagy, characterized by iron-dependent reactive oxygen species (ROS) generation secondary to failure of glutathione-dependent antioxidant defenses. The results of the present study are the first to demonstrate in vitro that ferroptosis is a central mechanism contributing to isoflurane neurotoxicity. We observed in embryonic mouse primary cortical neuronal cultures (day-in-vitro 7) that 6 h of 2% isoflurane exposure was associated with decreased transcription and protein expression of the lipid repair enzyme glutathione peroxidase 4. In parallel, isoflurane exposure resulted in increased ROS generation, disruption in mitochondrial membrane potential, and cell death. These effects were significantly attenuated by pre-treatment with the selective ferroptosis inhibitor ferrostatin-1 (Fer-1). Collectively, these observations provide a novel mechanism for isoflurane-induced injury in the developing brain and suggest that pre-treatment with Fer-1 may be a potential clinical intervention for neuroprotection.

Neuroprotective effects of dexmedetomidine against isoflurane-induced neuronal injury via glutamate regulation in neonatal rats

Background

Considerable evidences support the finding that the anesthesia reagent isoflurane increases neuronal cell death in young rats. Recent studies have shown that dexmedetomidine can reduce isoflurane-induced neuronal injury, but the mechanism remains unclear. We investigated whether isoflurane cause neurotoxicity to the central nervous system by regulating the N-methyl-D-aspartate receptor (NMDAR) and excitatory amino acid transporter1 (EAAT1) in young rats. Furthermore, we examined if dexmedetomidine could decrease isoflurane-induced neurotoxicity.

Methods

Neonatal rats (postnatal day 7, n=144) were randomly divided into four groups of 36 animals each: control (saline injection without isoflurane); isoflurane (2% for 4 h); isoflurane + single dose of dexmedetomidine (75 µg/kg, 20 min before the start of 2% isoflurane for 4 h); and isoflurane + dual doses of dexmedetomidine (25 µg/kg, 20 min before and 2 h after start of isoflurane at 2% for 4 h). Six neonates from each group were euthanatized at 2 h, 12 h, 24 h, 3 days, 7 days and 28 days post-anesthesia. Hippocampi were collected and processed for protein extraction. Expression levels of the NMDAR subunits NR2A and NR2B, EAAT1 and caspase-3 were measured by western blot analysis.

Results

Protein levels of NR2A, EAAT1 and caspase-3 were significantly increased in hippocampus of the isoflurane group from 2 h to 3 days, while NR2B levels were decreased. However, the -induced increase in NR2A, EAAT1 and caspase-3 and the decrease in NR2B in isoflurane-exposed rats were ameliorated in the rats treated with single or dual doses of dexmedetomidine. Isoflurane-induced neuronal damage in neonatal rats is due in part to the increase in NR2A and EAAT1 and the decrease in NR2B in the hippocampus.

Conclusion

Dexmedetomidine protects the brain against the use of isoflurane through the regulation of NR2A, NR2B and EAAT1. However, using the same amount of dexmedetomidine, the trend of protection is basically the same.

Erector spinae plane block for inguinal hernia repair in preterm infants

Neuro-axial anesthesia has been the preferred technique for inguinal hernia repair when attempting to avoid general anesthesia in neonates and preterm infants. We present a case where an erector spinae plane block was used successfully for this surgery. Hemodynamic stability, minimal anesthetic requirements, and excellent pain control were documented. This block promises to be a valuable and safe alternative for inguinal hernia repair, accompanying the path of neuroprotective anesthesia.

Outcomes after endoscopic dilation of laryngotracheal stenosis: an analysis of ACS-NSQIP

IMPORTANCE

Endoscopic management of pediatric subglottic stenosis (SGS) is common, however no multi-institutional studies have assessed its perioperative outcomes. The American College of Surgeon's National Surgical Quality Improvement Program - Pediatric (ACS-NSQIP-P) represents a source of such data.

DESIGN

Current procedural terminology (CPT) codes were queried for endoscopic or open airway reconstruction in the ACS-NSQIP-P Public Use File (PUF). Demographics and 30-day events were abstracted to compare open to endoscopic techniques and to assess for risk factors for varied outcomes after endoscopic dilation.

SETTING

National database.

PARTICIPANTS

Patients with data reported in the 2015 ACS-NSQIP-P PUF.

MEASUREMENTS

Length of stay (LOS), 30-day rates of reintubation, readmission and reoperation.

RESULTS

171 endoscopic and 116 open procedures were identified. Mean age at endoscopic and open procedures was 4.1 (SEM = 0.37) and 5.4 years (SEM = 0.40) respectively. Mean LOS was shorter after endoscopic procedures (5.5 days, SEM = 1.13 vs. 11.3 days SEM = 1.01, p = 0.0003). Open procedures had higher rates of reintubation (OR = 7.41, p = .026) and reoperation (OR = 3.09, p = .009). In patients undergoing endoscopic dilation, children <1 year were more likely to require readmission (OR=4.21, p=0.03) and reoperation (OR=4.39, p=0.03) when compared to older children.

CONCLUSION

Open airway reconstruction is associated with longer LOS and increased reintubations and reoperations, suggesting a possible opportunity to improve value in healthcare in the appropriately selected patient. Reoperations and readmissions following endoscopic dilation are more prevalent in children less than one year.

Propofol Exposure in Early Life Induced Developmental Impairments in the Mouse Cerebellum

Propofol is a widely used anesthetic in the clinic while several studies have demonstrated that propofol exposure may cause neurotoxicity in the developing brain. However, the effects of early propofol exposure on cerebellar development are not well understood. Propofol (30 or 60 mg/kg) was administered to mice on postnatal day (P)7; Purkinje cell dendritogenesis and Bergmann glial cell development were evaluated on P8, and granule neuron migration was analyzed on P10. The results indicated that exposure to propofol on P7 resulted in a significant reduction in calbindin-labeled Purkinje cells and their dendrite length. Furthermore, propofol induced impairments in Bergmann glia development, which might be involved in the delay of granule neuron migration from the external granular layer (EGL) to the internal granular layer (IGL) during P8 to P10 at the 60 mg/kg dosage, but not at the 30 mg/kg dosage. Several reports have suggested that the Notch signaling pathway plays instructive roles in the morphogenesis of Bergmann glia. Here, it was revealed that propofol treatment decreased Jagged1 and Notch1 protein levels in the cerebellum on P8. Taken together, exposure to propofol during the neonatal period impairs Bergmann glia development and may therefore lead to cerebellum development defects. Our results may aid in the understanding of the neurotoxic effects of propofol when administrated to infants.

Dexmedetomidine as a Supplement to Spinal Anesthesia Block: A Case Report of Three Infants

We report a novel use for dexmedetomidine as a supplemental intravenous or intranasal sedative for spinal anesthesia in infants. The children were 1, 2, and 9 months old having either inguinal hernia repair or circumcision. None of them experienced clinically relevant hemodynamic changes or apnea. Pain scores were zero throughout the postoperative period.

The "Surgeon on Service" Model for Timely, Economically Viable Inpatient Care of Tracheostomy Patients in Academic Pediatric Otolaryngology

Importance

The traditional practice model for pediatric otolaryngologists at high-volume academic centers is to simultaneously balance outpatient care responsibilities with those of the inpatient service, emergency department, and ambulatory care clinics. This model leads to challenges with care coordination, timeliness of nonemergency operative care, and consistent participation in care and consultation at the attending surgeon level. The "surgeon on service" (SOS) model-where faculty members rotate to manage the inpatient service in lieu of outpatient responsibilities-has been described as one method to address this conundrum. The operational and economic feasibility of the SOS model has been demonstrated; however, its impact on care coordination, time from consultation to surgical care, and length of stay (LOS) have not been evaluated.

Objective

To determine the impact of the SOS model on the quality principles of timeliness and efficiency of tracheostomy tube placement and to determine if the SOS model is fiscally feasible in an academic pediatric otolaryngology practice.

Design, Setting, and Participants

Medical record review of patients undergoing tracheostomy in a pediatric academic medical center and survey of their treating physician trainees, comparing the 6-month SOS pilot phase (postimplementation, January-June 2016) with the 6-month preimplementation period (January-June 2015).

Intervention

Implementation of the SOS model.

Main Outcomes and Measures

Time to tracheostomy, frequency of successful coordination of tracheostomy with gastrostomy tube placement, total LOS, productivity measured in work relative value units, and responses to trainee surveys.

Results

Of the 41 patients included in the study (24 boys and 17 girls; mean age, 3 years; range, 3 months to 17 years), 15 were treated before SOS implementation, and 26 after. Also included were 21 trainees. Before SOS implementation, median time to tracheostomy was 7 days (range, 2-20 days); after SOS implementation, it was 4 days (range, 1-10 days) (difference between the medians, before to after, -3 days; 95% CI, -5 to 0 days). There was no significant difference in overall LOS or ability to coordinate tracheostomy with gastrostomy tube placement. Preimplementation trainee surveys cited dissatisfaction with the communication channels to the primary team when the consulting surgeon was not immediately available to perform tracheostomy. No challenges were reported after implementation. Productivity was comparable to that in the outpatient setting.

Conclusions and Relevance

In this study, the presence of a rotating inpatient pediatric otolaryngologist was a productive approach to patient care associated with more timely performance of tracheostomy. Other benefits were an improved balance of service with education to trainees and a better perception of communication with consulting services.

Inhibition of p75 neurotrophin receptor does not rescue cognitive impairment in adulthood after isoflurane exposure in neonatal mice

BACKGROUND

Isoflurane is widely used for anaesthesia in humans. Isoflurane exposure of rodents prior to post-natal day 7 (PND7) leads to widespread neurodegeneration in laboratory animals. Previous data from our laboratory suggest an attenuation of apoptosis with the p75 neurotrophin receptor (p75NTR) inhibitor TAT-Pep5. We hypothesized that isoflurane toxicity leads to behavioural and cognitive abnormalities and can be rescued with pre-anaesthesia administration of TAT-Pep5.

METHODS

Neonatal mouse pups were pretreated with either TAT-Pep5 (25 μl, 10 μM i.p.) or a scrambled control peptide (TAT-ctrl; 25 μl, 10 μM i.p.) prior to isoflurane exposure (1.4%; 4 h) or control ( n  = 15-26/group). Three to 5 months after exposure, behavioural testing and endpoint assays [brain volume (stereology) and immunoblotting] were performed.

RESULTS

No significant difference was observed in open field, T-maze, balance beam or wire-hanging testing. The Barnes maze revealed a significant effect of isoflurane ( P  = 0.019) in errors to find the escape tunnel during the day 5 probe trial, a finding indicative of impaired short-term spatial memory. No difference was found for brain volumes or protein expression. TAT-Pep5 treatment did not reverse the effects of isoflurane on neurocognitive behaviour.

CONCLUSION

A single isoflurane exposure to early post-natal mice caused a hippocampal-dependent memory deficit that was not prevented by pre-administration of TAT-Pep5, although TAT-Pep5, an inhibitor of p75NTR, has been shown to reduce isoflurane-induced apoptosis. These findings suggest that neuronal apoptosis is not requisite for the development of cognitive deficits in the adults attendant with neonatal anaesthetic exposure.

Neonatal anesthetic neurotoxicity: Insight into the molecular mechanisms of long-term neurocognitive deficits

Mounting animal studies have demonstrated that almost all the clinically used general anesthetics could induce widespread neuroapoptosis in the immature brain. Alarmingly, some published findings have reported long-term neurocognitive deficits in response to early anesthesia exposure which deeply stresses the potential seriousness of developmental anesthetic neurotoxicity. However, the connection between anesthesia induced neuroapoptosis and subsequent neurocognitive deficits remains controversial. It should be noted that developmental anesthesia related neurotoxicity is not limited to neuroapoptosis. Early anesthesia exposure caused transient suppression of neurogenesis, ultrastructural abnormalities in synapse and alteration in the development of neuronal networks also could contribute to the long-term neurocognitive dysfunction. Understanding the mechanisms of developmental anesthetic neurotoxicity, especially by which anesthesia impairs brain function months after exposure, may lead to development of rational preventive and therapeutic strategies. The focus of present review is on some of those potential mechanisms that have been proposed for anesthesia induced cognitive decline.

Neonatal inhibition of Na+-K+-2Cl--cotransporter prevents ketamine induced spatial learning and memory impairments

Prolonged ketamine exposure in neonates at anesthetic doses is known to cause long-term impairments of learning and memory. A current theoretical mechanism explains this phenomenon as being neuro-excitotoxicity mediated by compensatory upregulation of N-methyl-d-aspartate receptors (NMDARs), which then initiates widespread neuroapoptosis. Additionally, the excitatory behavior of GABAergic synaptic transmission mediated by GABA_A receptors (GABA_ARs), occurring during the early neuronal development period, is proposed as contributing to the susceptibility of neonatal neurons to ketamine-induced injury. This is due to differential developmental expression patterns of Na⁺-K⁺-2Cl^- co-transporter (NKCC1) and K⁺-Cl^- co-transporter. Studies have shown that bumetanide, an NKCC1 inhibitor, allows neurons to become inhibitory rather than excitatory early in development. We thus hypothesized that bumetanide co-administration during ketamine treatment would reduce over excitation and protect the neurons from excitotoxicity. In this initial study, the Morris Water Maze test was used to assess the effects of co-administration of ketamine and bumetanide to neonatal Sprague-Dawley rats on long-term learning and memory changes seen later in life. It was revealed that bumetanide, when co-treated with ketamine neonatally, significantly impeded behavioral deficits typically seen in animals exposed to ketamine alone. Therefore, these findings suggest a new mechanism by which neonatal ketamine induced learning impairments can be prevented.

Post-Exposure Exercise Fails to Ameliorate Memory Impairment Induced by Propofol and Ketamine in Developing Rats

Background

This aim of this study was to determine the effects of ketamine-propofol combination on learning and memory, as well as exercise, on anesthetic neurotoxicity.

Material/Methods

A ketamine-propofol combination was administered once (group SKP, Single Ketamine Propofol) on P7 (postnatal day 7) or in 3 treatments on P6, P8, and P10 (group MKP, Multiple Ketamine Propofol). Rat pups in group C (Control) received equivalent volumes of normal saline in 3 injections on P6, P8, and P10. Rats designated MKPR (Multiple Ketamine Propofol and running) and CR (Control and running) began running exercise on P21 on wheels. Learning and memory was assessed by Morris water maze and fear conditioning tests. Hippocampal neurogenesis of rats was detected by BrdU immunofluorescence.

Results

MKP rats had longer latency to platform than group C during training in the Morris water maze; SKP rats stayed in the target quadrant longer than MKP rats during testing (P<0.05). Rats in running groups had shorter latency than non-running rats, but running had no interaction with anesthesia exposure.

Conclusions

Repeat ketamine-propofol combination doses increase risk of memory impairment in developing rats. Running has no impact on anesthetic neurotoxicity.

Evaluation of Pre-Hematopoietic Cell Transplantation (HCT) Brain MRI and Neurologic Complications of Pediatric Patients Undergoing HCT for Hematologic Malignancies

Adverse neurologic complications (NC) occur commonly in pediatric patients with hematologic malignancies both pre- and post-allogeneic hematopoietic cell transplant (HCT). Given this known risk, we previously obtained pre-HCT brain magnetic resonance imaging (MRI) to document baseline abnormalities but utility of this and findings are not well described. This study aimed to ( a) determine the prevalence and risk factors for abnormal brain MRI and ( b) determine prevalence and risk factors for development of new NC during and 2 years post-HCT. Retrospective chart review included 102 patients with hematologic malignancies who underwent allogeneic HCT between 2000 and 2009 at University of California San Francisco (UCSF) Children's Hospital and included standard HCT data, brain MRI reports, and NC and symptoms pre- and post-HCT. Forty-three percent of patients had abnormal findings on pre-MRI, most commonly nonspecific white matter changes. Neurologic symptoms pre-HCT was the only significant risk factor for abnormal MRI. Eleven patients (11%) developed post-HCT NC. Non-Caucasian race was the only significant risk factor for new NC. Although abnormal pre-HCT brain MRI is common, these findings are not predictive of subsequent NC post-HCT. Therefore routine surveillance may not be informative for that purpose, particularly when general anesthesia is required, which can have detrimental neurocognitive effects. Etiology of NC in pediatric HCT is likely multifactorial and may include genetic and ethnic predispositions.

Baron R, Binder A, Biniek R, Braune S, Buerkle H, Dall P, Demirakca S, Eckardt R, Eggers V, Eichler I, Fietze I, Freys S, Fründ A, Garten L, Gohrbandt B, Harth I, Hartl W, Heppner HJ, Horter J, Huth R, Janssens U, Jungk C, Kaeuper KM, Kessler P, Kleinschmidt S, Kochanek M, Kumpf M, Meiser A, Mueller A, Orth M, Putensen C, Roth B, Schaefer M, Schaefers R, Schellongowski P, Schindler M, Schmitt R, Scholz J, Schroeder S, Schwarzmann G, Spies C, Stingele R, Tonner P, Trieschmann U, Tryba M, Wappler F, Waydhas C, Weiss B, Weisshaar G. Evidence and consensus based guideline for the management of delirium, analgesia, and sedation in intensive care medicine. Revision 2015 (DAS-Guideline 2015) - short version

In 2010, under the guidance of the DGAI (German Society of Anaesthesiology and Intensive Care Medicine) and DIVI (German Interdisciplinary Association for Intensive Care and Emergency Medicine), twelve German medical societies published the “Evidence- and Consensus-based Guidelines on the Management of Analgesia, Sedation and Delirium in Intensive Care”. Since then, several new studies and publications have considerably increased the body of evidence, including the new recommendations from the American College of Critical Care Medicine (ACCM) in conjunction with Society of Critical Care Medicine (SCCM) and American Society of Health-System Pharmacists (ASHP) from 2013. For this update, a major restructuring and extension of the guidelines were needed in order to cover new aspects of treatment, such as sleep and anxiety management. The literature was systematically searched and evaluated using the criteria of the Oxford Center of Evidence Based Medicine. The body of evidence used to formulate these recommendations was reviewed and approved by representatives of 17 national societies. Three grades of recommendation were used as follows: Grade “A” (strong recommendation), Grade “B” (recommendation) and Grade “0” (open recommendation). The result is a comprehensive, interdisciplinary, evidence and consensus-based set of level 3 guidelines. This publication was designed for all ICU professionals, and takes into account all critically ill patient populations. It represents a guide to symptom-oriented prevention, diagnosis, and treatment of delirium, anxiety, stress, and protocol-based analgesia, sedation, and sleep-management in intensive care medicine.

Carbon monoxide pollution and neurodevelopment: A public health concern

Although an association between air pollution and adverse systemic health effects has been known for years, the effect of pollutants on neurodevelopment has been underappreciated. Recent evidence suggests a possible link between air pollution and neurocognitive impairment and behavioral disorders in children, however, the exact nature of this relationship remains poorly understood. Infants and children are uniquely vulnerable due to the potential for exposure in both the fetal and postnatal environments during critical periods in development. Carbon monoxide (CO), a common component of indoor and outdoor air pollution, can cross the placenta to gain access to the fetal circulation and the developing brain. Thus, CO is of particular interest as a known neurotoxin and a potential public health threat. Here we review overt CO toxicity and the policies regulating CO exposure, detail the evidence suggesting a potential link between CO-associated ambient air pollution, tobacco smoke, and learning and behavioral abnormalities in children, describe the effects of subclinical CO exposure on the brain during development, and provide mechanistic insight into a potential connection between CO exposure and neurodevelopmental outcome. CO can disrupt a number of critical processes in the developing brain, providing a better understanding of how this specific neurotoxin may impair neurodevelopment. However, further investigation is needed to better define the effects of perinatal CO exposure on the immature brain. Current policies regarding CO standards were established based on evidence of cardiovascular risk in adults with pre-existing comorbidities. Thus, recent and emerging data highlighted in this review regarding CO exposure in the fetus and developing child may be important to consider when the standards and guidelines are evaluated and revised in the future.

Positron Emission Tomography with [(18)F]FLT Revealed Sevoflurane-Induced Inhibition of Neural Progenitor Cell Expansion in vivo

Neural progenitor cell expansion is critical for normal brain development and an appropriate response to injury. During the brain growth spurt, exposures to general anesthetics, which either block the N-methyl-d-aspartate receptor or enhance the γ-aminobutyric acid receptor type A can disturb neuronal transduction. This effect can be detrimental to brain development. Until now, the effects of anesthetic exposure on neural progenitor cell expansion in vivo had seldom been reported. Here, minimally invasive micro positron emission tomography (microPET) coupled with 3'-deoxy-3' [(18)F] fluoro-l-thymidine ([(18)F]FLT) was utilized to assess the effects of sevoflurane exposure on neural progenitor cell proliferation. FLT, a thymidine analog, is taken up by proliferating cells and phosphorylated in the cytoplasm, leading to its intracellular trapping. Intracellular retention of [(18)F]FLT, thus, represents an observable in vivo marker of cell proliferation. Here, postnatal day 7 rats (n = 11/group) were exposed to 2.5% sevoflurane or room air for 9 h. For up to 2 weeks following the exposure, standard uptake values (SUVs) for [(18)F]-FLT in the hippocampal formation were significantly attenuated in the sevoflurane-exposed rats (p < 0.0001), suggesting decreased uptake and retention of [(18)F]FLT (decreased proliferation) in these regions. Four weeks following exposure, SUVs for [(18)F]FLT were comparable in the sevoflurane-exposed rats and in controls. Co-administration of 7-nitroindazole (30 mg/kg, n = 5), a selective inhibitor of neuronal nitric oxide synthase, significantly attenuated the SUVs for [(18)F]FLT in both the air-exposed (p = 0.00006) and sevoflurane-exposed rats (p = 0.0427) in the first week following the exposure. These findings suggested that microPET in couple with [(18)F]FLT as cell proliferation marker could be used as a non-invasive modality to monitor the sevoflurane-induced inhibition of neural progenitor cell proliferation in vivo.

Isoflurane suppresses early cortical activity

Objective

Isoflurane and other volatile anesthetics are widely used in children to induce deep and reversible coma, but they may also exert neurotoxic actions. The effects of volatile anesthetics on the immature brain activity remain elusive, however.

Methods

The effects of isoflurane on spontaneous and sensory-evoked activity were explored using intracortical extracellular field potential and multiple unit recordings in the rat barrel cortex from birth to adulthood.

Results

During the first postnatal week, isoflurane suppressed cortical activity in a concentration-dependent manner. At surgical anesthesia levels (1.5–2%), isoflurane completely suppressed the electroencephalogram and silenced cortical neurons. Although sensory potentials evoked by the principal whisker deflection persisted, sensory-evoked early gamma and spindle-burst oscillations were completely suppressed by isoflurane. Isoflurane-induced burst-suppression pattern emerged during the second postnatal week and matured through the first postnatal month. Bursts in adolescent and adult rats were characterized by activation of entire cortical columns with a leading firing of infragranular neurons, and were triggered by principal and adjacent whiskers stimulation, and by auditory and visual stimuli, indicating an involvement of horizontal connections in their generation and horizontal spread.

Interpretation

The effects of isoflurane on cortical activity shift from total suppression of activity to burst-suppression pattern at the end of the first postnatal week. Developmental emergence of bursts likely involves a development of the intracortical short-and long-range connections. We hypothesize that complete suppression of cortical activity under isoflurane anesthesia during the first postnatal week may explain neuronal apoptosis stimulated by volatile anesthetics in the neonatal rats.

Modeling anesthetic developmental neurotoxicity using human stem cells

Mounting preclinical evidence in rodents and nonhuman primates has demonstrated that prolonged exposure of developing animals to general anesthetics can induce widespread neuronal cell death followed by long-term memory and learning disabilities. In vitro experimental evidence from cultured neonatal animal neurons confirmed the in vivo findings. However, there is no direct clinical evidence of the detrimental effects of anesthetics in human fetuses, infants, or children. Development of an in vitro neurogenesis system using human stem cells has opened up avenues of research for advancing our understanding of human brain development and the issues relevant to anesthetic-induced developmental toxicity in human neuronal lineages. Recent studies from our group, as well as other groups, showed that isoflurane influences human neural stem cell proliferation and neurogenesis, whereas ketamine induces neuroapoptosis. Application of this high throughput in vitro stem cell neurogenesis approach is a major stride toward ensuring the safety of anesthetic agents in young children. This in vitro human model allows us to (1) screen the toxic effects of various anesthetics under controlled conditions during intense neuronal growth, (2) find the trigger for the anesthetic-induced catastrophic chain of toxic events, and (3) develop prevention strategies to avoid this toxic effect. In this article, we reviewed the current findings in anesthetic-induced neurotoxicity studies, specifically focusing on the in vitro human stem cell model.

Pharmacological treatment of neonatal pain: in search of a new equipoise

Inadequate management of pain in early human life contributes to impaired neurodevelopmental outcome and alters pain thresholds, pain or stress-related behavior and physiological responses. However, there are also emerging animal experimental data on the impact of exposure to analgo-sedatives on the incidence and extent of neuro-apoptosis. Since this association has also been suggested in humans, the pharmacological treatment of neonatal pain is in search of a new equipoise since these 'conflicting' observations are the main drivers to further reconsider our current treatment regimens. This review focuses on new data concerning clinical pharmacology of morphine, followed by data on more recently introduced opioids like remifentanil and tramadol, locoregional anesthesia and minimally invasive techniques in neonates, and finally with data on intravenous paracetamol. Since the available data are still incomplete, priorities for both clinical management and future research will be proposed.

Anesthetics interfere with the polarization of developing cortical neurons

Numerous studies from the clinical and preclinical literature indicate that general anesthetic agents have toxic effects on the developing brain, but the mechanism of this toxicity is still unknown. Previous studies have focused on the effects of anesthetics on cell survival, dendrite elaboration, and synapse formation, but little attention has been paid to possible effects of anesthetics on the developing axon. Using dissociated mouse cortical neurons in culture, we found that isoflurane delays the acquisition of neuronal polarity by interfering with axon specification. The magnitude of this effect is dependent on isoflurane concentration and exposure time over clinically relevant ranges, and it is neither a precursor to nor the result of neuronal cell death. Propofol also seems to interfere with the acquisition of neuronal polarity, but the mechanism does not require activity at GABAA receptors. Rather, the delay in axon specification likely results from a slowing of the extension of prepolarized neurites. The effect is not unique to isoflurane as propofol also seems to interfere with the acquisition of neuronal polarity. These findings demonstrate that anesthetics may interfere with brain development through effects on axon growth and specification, thus introducing a new potential target in the search for mechanisms of pediatric anesthetic neurotoxicity.

General anesthetics inhibit erythropoietin induction under hypoxic conditions in the mouse brain

Background

Erythropoietin (EPO), originally identified as a hematopoietic growth factor produced in the kidney and fetal liver, is also endogenously expressed in the central nervous system (CNS). EPO in the CNS, mainly produced in astrocytes, is induced under hypoxic conditions in a hypoxia-inducible factor (HIF)-dependent manner and plays a dominant role in neuroprotection and neurogenesis. We investigated the effect of general anesthetics on EPO expression in the mouse brain and primary cultured astrocytes.

Methodology/Principal Findings

BALB/c mice were exposed to 10% oxygen with isoflurane at various concentrations (0.10–1.0%). Expression of EPO mRNA in the brain was studied, and the effects of sevoflurane, halothane, nitrous oxide, pentobarbital, ketamine, and propofol were investigated. In addition, expression of HIF-2α protein was studied by immunoblotting. Hypoxia-induced EPO mRNA expression in the brain was significantly suppressed by isoflurane in a concentration-dependent manner. A similar effect was confirmed for all other general anesthetics. Hypoxia-inducible expression of HIF-2α protein was also significantly suppressed with isoflurane. In the experiments using primary cultured astrocytes, isoflurane, pentobarbital, and ketamine suppressed hypoxia-inducible expression of HIF-2α protein and EPO mRNA.

Conclusions/Significance

Taken together, our results indicate that general anesthetics suppress activation of HIF-2 and inhibit hypoxia-induced EPO upregulation in the mouse brain through a direct effect on astrocytes.

Early anesthetic exposure and long-term cognitive impairment

Several lines of evidence from clinical cohort studies and animal studies have shown that early exposure to anesthetics is a significant risk factor for later development of learning disabilities. However, the underlying molecular mechanism is unclear. Recent studies have indicated that hippocampal neurogenesis and synaptogenesis may be involved in the mechanisms by which early anesthetic exposure produces long-term cognitive impairment. It is possible that synaptic scaffolding protein postsynaptic density-95 (PSD-95) PDZ (PSD 95/Discs large/Zona occludens-1) domain-mediated protein-protein interactions are involved in the regulation of neurogenesis and synaptogenesis in the central nervous system. PDZ domain-mediated protein-protein interactions are disrupted by clinically relevant concentrations of inhaled anesthetics. It will help us understand the molecular mechanism underlying anesthetic-induced long-term cognitive dysfunction if we can demonstrate the role of synaptic PDZ interactions in early anesthetic exposure-produced long-term cognitive impairment.

Defining awakening from anesthesia in infants: a narrative review of published descriptions and scales of behavior

OBJECTIVES

A descriptive tool or validated scale of consciousness is desirable in infants to test the value of any depth of anesthesia monitor.

METHODS

We have reviewed published descriptions and scales of observed behavior that may be applicable to the study of infants during the transition from anesthesia to wakefulness.

RESULTS

Potentially useful scales were found that had been developed for the assessment and study of natural sleep, neurological state, arousal, anesthesia, sedation, coma, and pain. Scales or criteria of behavior had been developed for anesthetised children, but there were no agreed definitions or criteria specifically for anesthetised infants or neonates.

CONCLUSION

Criteria for awakening of infants from anesthesia need to be developed and agreed.

Ketamine anesthesia during the first week of life can cause long-lasting cognitive deficits in rhesus monkeys

Previously our laboratory has shown that ketamine exposure (24h of clinically relevant anesthesia) causes significant increases in neuronal cell death in perinatal rhesus monkeys. Sensitivity to this ketamine-induced neurotoxicity was observed on gestational days 120-123 (in utero exposure via maternal anesthesia) and on postnatal days (PNDs) 5-6, but not on PNDs 35-37. In the present study, six monkeys were exposed on PND 5 or 6 to intravenous ketamine anesthesia to maintain a light surgical plane for 24h and six control animals were unexposed. At 7 months of age all animals were weaned and began training to perform a series of cognitive function tasks as part of the National Center for Toxicological Research (NCTR) Operant Test Battery (OTB). The OTB tasks used here included those for assessing aspects of learning, motivation, color discrimination, and short-term memory. Subjects responded for banana-flavored food pellets by pressing response levers and press-plates during daily (M-F) test sessions (50 min) and were assigned training scores based upon their individual performance. As reported earlier (Paule et al., 2009) beginning around 10 months of age, control animals significantly outperformed (had higher training scores than) ketamine-exposed animals for approximately the next 10 months. For animals now over 3 and one-half years of age, the cognitive impairments continue to manifest in the ketamine-exposed group as poorer performance in the OTB learning and color and position discrimination tasks, as deficits in accuracy of task performance, but also in response speed. There are also apparent differences in the motivation of these animals which may be impacting OTB performance. These observations demonstrate that a single 24-h episode of ketamine anesthesia, occurring during a sensitive period of brain development, results in very long-lasting deficits in brain function in primates and provide proof-of-concept that general anesthesia during critical periods of brain development can result in subsequent functional deficits. Supported by NICHD, CDER/FDA and NCTR/FDA.

Dexmedetomidine and ketamine for sedation during spinal anesthesia in children

STUDY OBJECTIVE

To evaluate the combination of dexmedetomidine and ketamine for sedation during lumbar puncture and sedation for spinal anesthesia in children.

DESIGN

Retrospective analysis of quality assurance data sheets and anesthetic records.

SETTING

Developing countries with the humanitarian group, Kids First.

PATIENTS

12 infants and children, ranging in age from two to 9 years.

INTERVENTIONS

A bolus dose of ketamine (two mg/kg) and dexmedetomidine (one μg/kg) was given over three minutes followed by a continuous infusion of dexmedetomidine (two μg/kg/hr for the first 30 min, followed by one μg/kg/hr for the duration of the case). Supplemental analgesia/sedation was provided by ketamine (0.5 mg/kg) as needed.

MEASUREMENTS

The need for supplemental ketamine, the ability to complete the procedure, and heart rate (HR), blood pressure, end-tidal carbon dioxide (ETCO(2)), and oxygen saturation values were recorded.

MAIN RESULTS

Effective sedation for lumbar puncture and performance of spinal anesthesia were achieved in all patients. One patient required a supplemental dose of ketamine (0.5 mg/kg). Following the bolus dose of ketamine and dexmedetomidine, HR increased by 11 ± 4 bpm. The greatest HR increase was 20 bpm. No patient had a HR increase ≥ 20% from baseline. The HR decrease was ≤ 30 bpm in 10 of the 12 patients, and the greatest HR decrease was 58 bpm. Systolic blood pressure (SBP) increased from baseline by 10 ± 3 mmHg after administration of the bolus dose of ketamine and dexmedetomidine. During the subsequent dexmedetomidine infusion, SBP decreased by 11 ± 9 mmHg. No patient's respiratory rate decreased to less than 10 breaths/min or increased above 24 breaths/min during the procedural sedation. The highest ETCO(2) was 45 ± 2 mmHg (P < 0.0001). Oxygen saturation remained ≥ 95% during the procedure in all patients.

CONCLUSION

A combination of ketamine and dexmedetomidine provides effective sedation during spinal anesthesia in infants and children, with limited effects on cardiovascular and ventilatory function.

What's new in obstetric anesthesia?

The current article covers some of the major themes that emerged in 2009 in the fields of obstetric anesthesiology, obstetrics, and perinatology, with a special emphasis on the implications for the obstetric anesthesiologist.

Sevoflurane for central catheter placement in neonatal intensive care: a randomized trial

OBJECTIVE

To compare the efficacy and safety of sevoflurane deep sedation with glucose and nonnutritive sucking (GNNS) in reducing the duration of the procedure and in preventing pain-related effects during peripherally inserted central catheter (PICC) placement.

BACKGROUND

PICC placement in neonatal intensive care is a delicate and stressful procedure that requires pain prevention. GNNS has been recommended in this situation but remain often inefficient.

METHODS

We designed a randomized controlled study in a sixteen-bed pediatric and neonatal unit in a tertiary hospital. Fifty-nine neonates at >28 weeks of gestation with continuous positive airway pressure or invasive mechanical ventilation and requiring PICC placement were included. Patients were randomized to receive inhaled sevoflurane (IS) or glucose and non-nutritive sucking (GNNS). Procedural duration and conditions, hemodynamic and respiratory parameters, occurrence of movements and complications were compared (http://clinicaltrials.gov trial register no. NCT00420693).

RESULTS

The two groups had similar demographics. There were no between-group differences in procedural duration (P = 0.84) despite greater immobility in IS group (P = 0.017). IS was also associated with fewer episodes of hypertension (P = 0.003), tachycardia (P < 0.001), and bradycardia (P = 0.02). Occurrences of hypotension were not different between the groups (P = 0.06). The GNNS group showed more desaturation during the 4 h after the procedure (P = 0.03). Complications during intensive care stay did not differ between groups.

CONCLUSION

Inhaled sevoflurane does not make easier catheters placement but prevent pain-related symptoms. Because sevoflurane is responsible for hypotension, it requires careful monitoring and treatment adaptation.

Validation of a preclinical spinal safety model: effects of intrathecal morphine in the neonatal rat

BACKGROUND

Preclinical studies demonstrate increased neuroapoptosis after general anesthesia in early life. Neuraxial techniques may minimize potential risks, but there has been no systematic evaluation of spinal analgesic safety in developmental models. We aimed to validate a preclinical model for evaluating dose-dependent efficacy, spinal cord toxicity, and long-term function after intrathecal morphine in the neonatal rat.

METHODS

Lumbar intrathecal injections were performed in anesthetized rats aged postnatal day (P) 3, 10, and 21. The relationship between injectate volume and segmental spread was assessed postmortem and by in vivo imaging. To determine the antinociceptive dose, mechanical withdrawal thresholds were measured at baseline and 30 min after intrathecal morphine. To evaluate toxicity, doses up to the maximum tolerated were administered, and spinal cord histopathology, apoptosis, and glial response were evaluated 1 and 7 days after P3 or P21 injection. Sensory thresholds and gait analysis were evaluated at P35.

RESULTS

Intrathecal injection can be reliably performed at all postnatal ages and injectate volume influences segmental spread. Intrathecal morphine produced spinally mediated analgesia at all ages with lower dose requirements in younger pups. High-dose intrathecal morphine did not produce signs of spinal cord toxicity or alter long-term function.

CONCLUSIONS

The therapeutic ratio for intrathecal morphine (toxic dose/antinociceptive dose) was at least 300 at P3 and at least 20 at P21 (latter doses limited by side effects). These data provide relative efficacy and safety for comparison with other analgesic preparations and contribute supporting evidence for the validity of this preclinical neonatal safety model.

Effects of intrathecal ketamine in the neonatal rat: evaluation of apoptosis and long-term functional outcome

BACKGROUND

Systemic ketamine can trigger apoptosis in the brain of rodents and primates during susceptible developmental periods. Clinically, spinally administered ketamine may improve the duration or quality of analgesia in children. Ketamine-induced spinal cord toxicity has been reported in adult animals but has not been systematically studied in early development.

METHODS

In anesthetized rat pups, intrathecal ketamine was administered by lumbar percutaneous injection. Changes in mechanical withdrawal threshold evaluated dose-dependent antinociceptive and carrageenan-induced antihyperalgesic effects in rat pups at postnatal day (P) 3 and 21. After intrathecal injection of ketamine at P3, 7, or 21, spinal cords were examined for apoptosis (Fluoro-Jade C and activated caspase-3), histopathologic change, and glial responses (ionized calcium-binding adapter molecule 1 and glial fibrillary acid protein). After maximal doses of ketamine or saline at P3 or P21, sensory thresholds and gait analysis were evaluated at P35.

RESULTS

Intrathecal injection of 3 mg/kg ketamine at P3 and 15 mg/kg at P21 reverses carrageenan-induced hyperalgesia. Baseline neuronal apoptosis in the spinal cord was greater at P3 than P7, predominantly in the dorsal horn. Intrathecal injection of 3-10 mg/kg ketamine in P3 pups (but not 15 mg/kg at P21) acutely increased apoptosis and microglial activation in the spinal cord and altered spinal function (reduced mechanical withdrawal threshold and altered static gait parameters) at P35.

CONCLUSIONS

Because acute pathology and long-term behavioral change occurred in the same dose range as antihyperalgesic effects, the therapeutic ratio of intrathecal ketamine is less than one in the neonatal rat. This measure facilitates comparison of the relative safety of spinally administered analgesic agents.

[Effects of general anaesthetics on the developing brain]

OBJECTIVE

To expose the current knowledge about the anaesthetic effects on the developing brain.

DATA SOURCES

Publications (original articles and reviews) in English and in French language from 1980 were obtained from the Medline database using alone or in combination following keywords: anaesthetics, developing brain, neurodevelopment, neurogenesis, synaptogenesis, neurotoxicity, apoptosis.

DATA SYNTHESIS

Several lines of evidence resulting from animal experiments conducted in rodents and non-human primates have suggested that exposing the developing brain to anaesthetic drugs may elicit an increase a physiological programmed neuronal death (i.e. apoptosis). This neuronal death is not only seen at the cellular level but also results in alterations in some behavioural abilities in the adult animal. However, the vast majority of experiments reported have been conducted in animals not exposed to any surgical or painful stimulation. Moreover, the literature raises contradictory results, some authors not confirming this neurotoxic effect of anaesthetic drugs. Last, available clinical data are scarce and do not allow to claim that exposure to general anaesthesia definitely alters the cognitive development of children.

CONCLUSION

This review raises the question of the innocuity of anaesthetic agents on the developing brain; further clinical trials are required in order to test this effect on human babies.