Standards for preclinical research and publications in developmental anaesthetic neurotoxicity: expert opinion statement from the SmartTots preclinical working group

Developmental anaesthesia neurotoxicity in humans: finding the sweet spot?

A recent human epidemiological study in this issue of British Journal of Anaesthesia examined the association between anaesthesia exposure in pregnant women undergoing appendicectomy or cholecystectomy and the subsequent diagnosis of behavioural disorders in their offspring. When compared with unexposed children, prenatally exposed children had ∼30% greater likelihood of a diagnosis of disruptive or internalising behavioural disorders. Although these data are new and interesting, they should be interpreted with caution. Indeed, appendicitis and cholecystitis can produce acute and chronic systemic inflammation, and maternal immune activation can affect fetal neurodevelopment through inflammatory and epigenetic mechanisms. It is, therefore, possible that the findings are related to maternal and fetal inflammation than to anaesthesia exposure. As there is no causal evidence for the implication that anaesthesia and surgery induce such pathologies, it is unwise to consider alternative treatments when surgery is indicated in pregnant patients.

Anesthetic Sevoflurane Induces Enlargement of Dendritic Spine Heads in Mouse Neurons via Tau-Dependent Mechanisms

BACKGROUND

Sevoflurane induces neuronal dysfunction and cognitive impairment. However, the underlying mechanism remains largely to be determined. Tau, cyclophilin D, and dendritic spine contribute to cognitive function. But whether changes in dendritic spines are involved in the effects of sevoflurane and the potential association with tau and cyclophilin D is not clear.

METHODS

We harvested hippocampal neurons from wild-type mice, tau knockout mice, and cyclophilin D knockout mice. We treated these neurons with sevoflurane at day in vitro 7 and measured the diameter of dendritic spine head and the number of dendritic spines. Moreover, we determined the effects of sevoflurane on the expression of excitatory amino acid transporter 3 (EAAT3), extracellular glutamate levels, and miniature excitatory postsynaptic currents (mEPSCs). Finally, we used lithium, cyclosporine A, and overexpression of EAAT3 in the interaction studies.

RESULTS

Sevoflurane-induced tau phosphgorylation increased the diameter of dendritic spine head and decreased the number of dendritic spines in neurons harvested from wild-type and cyclophilin D knockout mice, but not tau knockout mice. Sevoflurane decreased the expression of EAAT3, increased extracellular glutamate levels, and decreased the frequency of mEPSCs in the neurons. Overexpression of EAAT3 mitigated the effects of sevoflurane on dendritic spines. Lithium, but not cyclosporine A, attenuated the effects of sevoflurane on dendritic spines. Lithium also inhibited the effects of sevoflurane on EAAT3 expression and mEPSCs.

CONCLUSIONS

These data suggest that sevoflurane induces a tau phosphorylation-dependent demtrimental effect on dendritic spine via decreasing EAAT3 expression and increasing extracellular glutamate levels, leading to neuronal dysfunction.

Effects of cumulative duration of repeated anaesthesia exposure on foetal brain development in the ovine model

OBJECTIVE

Anaesthesia is required in 0.4-1% of pregnant women, and prolonged and repeated exposures to anaesthesia may be required. It is unknown whether these exposures may result in foetal neurotoxicity in humans. As sheep have a gestation comparable to that of humans, the objective of this study was to analyse the neurodevelopmental outcome of ovine foetuses that had been exposed in utero to repeated and prolonged anaesthesia.

DESIGN

Randomized controlled preclinical study.

SETTING

Anaesthesia for non-obstetric surgery during pregnancy.

ANIMALS

Twenty-four healthy pregnant Swifter ewes.

INTERVENTIONS

The ewes were randomized to no anaesthesia exposure (control-group), single exposure (at gestational age 68-70 days), or repeated exposure (at gestational age 68-70 days and 96-98 days) to 2.5 h of sevoflurane anaesthesia and maternal laparotomy. All lambs were delivered at approximately term gestation (gestational age: 140-143 days).

MEASUREMENTS

The primary outcome was neuron density in the frontal cortex 24 h after birth for the control-group versus the repeated-exposure-group. Key secondary outcome was the time needed to achieve the milestone of standing. Secondary outcomes included other neurobehavioural assessments (e.g., motoric milestones) and histological parameters quantified in multiple brain regions (neuron density, total cell density, proliferation, inflammation, synaptogenesis, astrocytes and myelination).

MAIN RESULTS

Neuron density in the frontal cortex did not differ between groups (mean ± standard deviation: control-group: 403 ± 39, single-exposure group: 436 ± 23 and repeated-exposure-group: 403 ± 40 neurons/mm2, control-group versus repeated-exposure-group: p = 0.986, control-group versus single-exposure-group: p = 0.097). No significant difference was observed for the time needed to achieve the milestone of standing. Only very limited differences were observed for other histological outcome parameters and neurobehavioural assessments.

CONCLUSIONS

There is no evidence for foetal neuronal injury or neurobehavioural impairments after a cumulative duration of 5 h repetitive prenatal anaesthesia in sheep.

Repeated neonatal isoflurane exposure facilitated stress-related fear extinction impairment in male mice and was associated with ΔFosB accumulation in the basolateral amygdala and the hippocampal dentate gyrus

Volatile anesthetics elicit neurodevelopmental toxicity in rodents and primates and lead to more exaggerated anxiety-like behavior in response to future stress. Anxiety and fear are closely correlated and maladaptive fear-associated learning is regarded as the core mechanism underlying anxiety-related disorders. However, little is known about the interaction between early-life anesthetic exposure and future stress and the accompanying effect on fear-associated learning. In the present study, we evaluated the alterations in fear-associated learning (fear acquisition and extinction) occurring in mice receiving repeated neonatal isoflurane exposure and chronic variable stress (CVS) successively through a series of fear conditioning, fear reinforcing, and fear extinction paradigms. The corticosterone (CORT) response during CVS and the immunohistochemical levels of ΔFosB and c-Fos expression in the basolateral amygdala (BLA) and the hippocampal dentate gyrus (DG) after the extinction retrieval test were also investigated. The results showed that neonatal isoflurane exposure could increase CORT levels following the first diurnal CVS procedure, but not after completion of the whole CVS paradigm. Neonatal isoflurane exposure exerted a repressive effect on fear acquisition, in contrast to that seen with CVS. Neonatal isoflurane exposure and CVS both exerted suppressive effects on fear extinction and there was a significant synergy between them. Furthermore, neonatal isoflurane exposure facilitated CVS-mediated ΔFosB accumulation in the BLA and the hippocampal DG, which may have been responsible for c-Fos expression deficits and fear extinction impairment. Collectively, these findings contribute to the understanding of the interaction between early-life anesthetic exposure and future stress, as well as the accompanying behavioral alterations.

Consequences of General Anesthesia in Infancy on Behavior and Brain Structure

BACKGROUND

One in 7 children will need general anesthesia (GA) before the age of 3. Brain toxicity of anesthetics is controversial. Our objective was to clarify whether exposure of GA to the developing brain could lead to lasting behavioral and structural brain changes.

METHODS

A first study was performed in mice. The behaviors (fear conditioning, Y-maze, and actimetry) and brain anatomy (high-resolution magnetic resonance imaging) of 6- to 8-week-old Swiss mice exposed or not exposed to GA from 4 to 10 days old were evaluated. A second study was a complementary analysis from the preexisting APprentissages EXécutifs et cerveau chez les enfants d'âge scolaire (APEX) cohort to assess the replicability of our data in humans. The behaviors (behavior rating inventory of executive function, emotional control, and working memory score, Backward Digit Span, and Raven 36) and brain anatomy (high-resolution magnetic resonance imaging) were compared in 102 children 9 to 10 years of age exposed or not exposed to a single GA (surgery) during infancy.

RESULTS

The animal study revealed chronic exacerbated fear behavior in the adult mice (95% confidence interval [CI], 4-80; P = .03) exposed to postnatal GA; this was associated with an 11% (95% CI, 7.5-14.5) reduction of the periaqueductal gray matter (P = .046). The study in humans suggested lower emotional control (95% CI, 0.33-9.10; P = .06) and a 6.1% (95% CI, 4.3-7.8) reduction in the posterior part of the right inferior frontal gyrus (P = .019) in the children who had been exposed to a single GA procedure.

CONCLUSIONS

The preclinical and clinical findings of these independent studies suggest lasting effects of early life exposure to anesthetics on later emotional control behaviors and brain structures.

Safety of general anaesthetics on the developing brain: are we there yet?

Thirty years ago, neurotoxicity induced by general anaesthetics in the developing brain of rodents was observed. In both laboratory-based and clinical studies, many conflicting results have been published over the years, with initial data confirming both histopathological and neurodevelopmental deleterious effects after exposure to general anaesthetics. In more recent years, animal studies using non-human primates and new human cohorts have identified some specific deleterious effects on neurocognition. A clearer pattern of neurotoxicity seems connected to exposure to repeated general anaesthesia. The biochemistry involved in this neurotoxicity has been explored, showing differential effects of anaesthetic drugs between the developing and developed brains. In this narrative review, we start with a comprehensive description of the initial concerning results that led to recommend that any non-essential surgery should be postponed after the age of 3 yr and that research into this subject should be stepped up. We then focus on the neurophysiology of the developing brain under general anaesthesia, explore the biochemistry of the observed neurotoxicity, before summarising the main scientific and clinical reports investigating this issue. We finally discuss the GAS trial, the importance of its results, and some potential limitations that should not undermine their clinical relevance. We finally suggest some key points that could be shared with parents, and a potential research path to investigate the biochemical effects of general anaesthesia, opening up perspectives to understand the neurocognitive effects of repetitive exposures, especially in at-risk children.

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.

Prenatal Isoflurane Exposure Induces Developmental Neurotoxicity in Rats: the Role of Gut Microbiota

Fetal exposure to inhaled anesthetics, such as isoflurane, may lead to neurodevelopmental impairment in offspring. Yet, the mechanisms of prenatal isoflurane-induced developmental neurotoxicity have not been fully elucidated. Gut microbiota is a pivotal modulator of brain development and functions. While the antibiotic effect of isoflurane has been previously investigated, the relationship between prenatal isoflurane exposure and postnatal gut microbiota, brain biology, and behavior remains unknown. In the present study, we treated pregnant rats with 2% isoflurane for 4 h on gestational day 14. Their offspring were tested with novel object recognition task on postnatal day 28 (P28) to assess cognition. Fecal microbiome was assessed using 16S RNA sequencing. We also analyzed hippocampal expression of brain-derived neurotrophic factor (BDNF) in P28 rat brains. To further explore the role of gut microbiota on prenatal isoflurane-induced developmental neurotoxicity, we treated rats with mixed probiotics on P14 for 14 days and evaluated novel object recognition and hippocampal expression of BDNF on P28. Results indicate that prenatal exposure to isoflurane significantly decreased novel object recognition (novel object preference ratio: mean difference (MD) - 0.157; 95% confidence interval (CI) - 0.234 to - 0.080, P < 0.001) paralleled by diminished expression of hippocampal BDNF in juvenile rats. Prenatal exposure to isoflurane also significantly altered the diversity and composition of gut microbiota. Treatment with probiotics mitigated these changes in cognition (novel object preference ratio: isoflurane group vs. control group: MD - 0.177; 95% CI - 0.307 to - 0.047, P = 0.006; probiotic group vs. isoflurane group: MD 0.140; 95% CI 0.004 to 0.275, P = 0.042) and BDNF expression. Taken together, our findings suggest that gut dysbiosis may be involved in the pathogenesis of maternal isoflurane exposure-induced postnatal cognitive impairment. To determine the causal relationship between gut microbiota and cognition in prenatal anesthetic-induced developmental neurotoxicity, further studies are needed.

Neurodevelopmental effects of maternal blood pressure management with noradrenaline during general anaesthesia for nonobstetric surgery in the pregnant rabbit model

BACKGROUND

In pregnant women, anaesthesia-induced hypotension is commonly treated using phenylephrine or noradrenaline, the rationale being to maintain uterine perfusion pressure and thereby uterine blood flow. Evidence for this strategy during general anaesthesia for nonobstetric surgery is absent.

OBJECTIVE

To analyse the effects of treating anaesthesia-induced hypotension with noradrenaline on brain development of rabbit foetuses of mothers subjected to general anaesthesia for nonobstetric surgery. We hypothesised that treatment of maternal hypotension would improve foetal outcomes.

DESIGN

Randomised controlled laboratory study using 21 pregnant rabbits (does) at 28 days of gestation.

INTERVENTION

Two hours of sevoflurane anaesthesia for a laparotomy without treatment of anaesthesia-induced hypotension (hypotension group) or with maintaining maternal mean arterial pressure above 80% of the awake value using noradrenaline (noradrenaline group). In the control group, does remained untouched. At term, all pups were delivered by caesarean section. One day later, the neurobehaviour of the pups was assessed and brains were harvested.

MAIN OUTCOMES

Neuron density in the frontal cortex for the comparison of noradrenaline groups versus hypotension groups was the primary outcome; the neurobehavioural scores and other histological outcomes were secondary outcomes.

RESULTS

In the noradrenaline groups and hypotension groups, neuron density in the frontal cortex was similar (1181 ± 162 versus 1189 ± 200 neurons mm-2, P = 0.870). However, significantly less foetal survival, lower sensory scores in neurobehavioural assessment and less proliferation were observed in the noradrenaline group when compared with the hypotension group. Neuron densities in other regions, total cell densities, biometrics and synaptogenesis were not affected. There were no differences between the control group and hypotension group.

CONCLUSION

During general anaesthesia for nonobstetric surgery in rabbits, treatment of anaesthesia-induced hypotension using noradrenaline did not affect neuron densities but was associated with impaired foetal outcomes according to several secondary outcome parameters. Further studies are needed to investigate any clinical relevance and to determine the target blood pressure in pregnant women during general anaesthesia.

Anesthesia and Developing Brains: Unanswered Questions and Proposed Paths Forward

Anesthetic agents disrupt neurodevelopment in animal models, but evidence in humans is mixed. The morphologic and behavioral changes observed across many species predicted that deficits should be seen in humans, but identifying a phenotype of injury in children has been challenging. It is increasingly clear that in children, a brief or single early anesthetic exposure is not associated with deficits in a range of neurodevelopmental outcomes including broad measures of intelligence. Deficits in other domains including behavior, however, are more consistently reported in humans and also reflect findings from nonhuman primates. The possibility that behavioral deficits are a phenotype, as well as the entire concept of anesthetic neurotoxicity in children, remains a source of intense debate. The purpose of this report is to describe consensus and disagreement among experts, summarize preclinical and clinical evidence, suggest pathways for future clinical research, and compare studies of anesthetic agents to other suspected neurotoxins.

Evaluation of neurotoxicity and long-term function and behavior following intrathecal 1 % 2-chloroprocaine in juvenile rats

Spinally-administered local anesthetics provide effective perioperative anesthesia and/or analgesia for children of all ages. New preparations and drugs require preclinical safety testing in developmental models. We evaluated age-dependent efficacy and safety following 1 % preservative-free 2-chloroprocaine (2-CP) in juvenile Sprague-Dawley rats. Percutaneous lumbar intrathecal 2-CP was administered at postnatal day (P)7, 14 or 21. Mechanical withdrawal threshold pre- and post-injection evaluated the degree and duration of sensory block, compared to intrathecal saline and naive controls. Tissue analyses one- or seven-days following injection included histopathology of spinal cord, cauda equina and brain sections, and quantification of neuronal apoptosis and glial reactivity in lumbar spinal cord. Following intrathecal 2-CP or saline at P7, outcomes assessed between P30 and P72 included: spinal reflex sensitivity (hindlimb thermal latency, mechanical threshold); social approach (novel rat versus object); locomotor activity and anxiety (open field with brightly-lit center); exploratory behavior (rearings, holepoking); sensorimotor gating (acoustic startle, prepulse inhibition); and learning (Morris Water Maze). Maximum tolerated doses of intrathecal 2-CP varied with age (1.0 μL/g at P7, 0.75 μL/g at P14, 0.5 μL/g at P21) and produced motor and sensory block for 10-15 min. Tissue analyses found no significant differences across intrathecal 2-CP, saline or naïve groups. Adult behavioral measures showed expected sex-dependent differences, that did not differ between 2-CP and saline groups. Single maximum tolerated in vivo doses of intrathecal 2-CP produced reversible spinal anesthesia in juvenile rodents without detectable evidence of developmental neurotoxicity. Current results cannot be extrapolated to repeated dosing or prolonged infusion.

Effects of general anaesthesia during pregnancy on neurocognitive development of the fetus: a systematic review and meta-analysis

BACKGROUND

The US Food and Drug Administration warned that exposure of pregnant women to general anaesthetics may impair fetal brain development. This review systematically evaluates the evidence underlying this warning.

METHODS

PubMed, EMBASE, and Web of Science were searched from inception until April 3, 2020. Preclinical and clinical studies were eligible. Exclusion criteria included case reports, in vitro models, chronic exposures, and exposure only during delivery. Meta-analyses were performed on standardised mean differences. The primary outcome was overall effect on learning/memory. Secondary outcomes included markers of neuronal injury (apoptosis, synapse formation, neurone density, and proliferation) and subgroup analyses.

RESULTS

There were 65 preclinical studies included, whereas no clinical studies could be identified. Anaesthesia during pregnancy impaired learning and memory (standardised mean difference -1.16, 95% confidence interval -1.46 to -0.85) and resulted in neuronal injury in all experimental models, irrespective of the anaesthetic drugs and timing in pregnancy. Risk of bias was high in most studies. Rodents were the most frequently used animal species, although their brain development differs significantly from that in humans. In a minority of studies, anaesthesia was combined with surgery. Monitoring and strict control of physiological homeostasis were below preclinical and clinical standards in many studies. The duration and frequency of exposure and anaesthetic doses were often much higher than in clinical routine.

CONCLUSION

Anaesthesia-induced neurotoxicity during pregnancy is a consistent finding in preclinical studies, but translation of these results to the clinical situation is limited by several factors. Clinical observational studies are needed.

PROSPERO REGISTRATION NUMBER

CRD42018115194.

The effect of xenon on fetal neurodevelopment following maternal sevoflurane anesthesia and laparotomy in rabbits

BACKGROUND

There is concern that maternal anesthesia during pregnancy impairs brain development of the human fetus. Xenon is neuroprotective in pre-clinical models of anesthesia-induced neurotoxicity in neonates. It is not known if xenon also protects the developing fetal brain when administered in addition to maternal sevoflurane-anesthesia during pregnancy.

OBJECTIVE

To investigate the effects of sevoflurane and xenon on neurobehaviour and neurodevelopment of the offspring in a pregnant rabbit model.

METHODS

Pregnant rabbits on post-conception day 28 (term = 31d) underwent two hours of general anesthesia with 1 minimum alveolar concentration (MAC) of sevoflurane in 30% oxygen (n = 17) or 1 MAC sevoflurane plus 50-60 % xenon in 30% oxygen (n = 10) during a standardized laparotomy while receiving physiological monitoring. A sham-group (n = 11) underwent monitoring alone for two hours. At term, the rabbits were delivered by caesarean section. On the first postnatal day, neonatal rabbits underwent neurobehavioral assessment using a validated test battery. Following euthanasia, the brains were harvested for neurohistological analysis. A mixed effects-model was used for statistical analysis.

RESULTS

Maternal cardiopulmonary parameters during anesthesia were within the reference range. Fetal survival rates were significantly higher in the sham-group as compared to the sevoflurane-group and the fetal brain/body weight ratio was significantly lower in the sevoflurane-group as compared with the sham- and xenon-group. Pups antenatally exposed to anesthesia had significantly lower motor and sensory neurobehavioral scores when compared to the sham-group (mean ± SD; sevo: 22.70 ± 3.50 vs. sevo+xenon: 22.74 ± 3.15 vs. sham: 24.37 ± 1.59; overall p = 0.003; sevo: 14.98 ± 3.00 vs. sevo+xenon: 14.80 ± 2.83 vs. sham: 16.43 ± 2.63; overall p = 0.006; respectively). Neuron density, neuronal proliferation and synaptic density were reduced in multiple brain regions of the exposed neonates. The co-administration of xenon had no measurable neuroprotective effects in this model.

CONCLUSIONS

In rabbits, sevoflurane anesthesia for a standardized laparotomy during pregnancy resulted in impaired neonatal neurobehavior and a decreased neuron count in several regions of the neonatal rabbit brain. Co-administration of xenon did not prevent this effect.

A decade later, there are still major issues to be addressed in paediatric anaesthesia

PURPOSE OF REVIEW

Despite real advances in paediatric anaesthesia management, such as a growing awareness of the relevance of anaesthesia conduct as well as of the lack of evidence for neurotoxicity of anaesthetic agents, it must be said that there are still important questions in our specialty that remain unanswered. Standardization and harmonization of airway management, analgesia techniques and outcome measures are the important issues we are facing at the beginning of this decade.

RECENT FINDINGS

Major improvements in airway management of neonates and infants resulted from the introduction of videolaryngoscopes and the systematic use of nasal oxygenation during endotracheal intubation. Similarly, the increasing popularity of dexmedetomidine has led to the generalization of its use, which, considering that it may produce undesirable effects, poses a challenge for the future. Moreover, recent systematic reviews have confirmed a lack of evidence for the efficacy of many techniques used in clinical practice.

SUMMARY

The shift in research from the neurotoxicity of anaesthetic agents to factors related to anaesthetic conduct are discussed. Examples for an improvement in anaesthesia management are highlighted with advocacy for including these evidence-based findings in routine clinical practice. Finally, the impact of using clinically relevant age-related and patient-centred perioperative outcomes is essential for comparing and/or interpreting the safety and efficacy of anaesthesia and analgesia management in children.

Repeated Neonatal Isoflurane Exposure is Associated with Higher Susceptibility to Chronic Variable Stress-induced Behavioural and Neuro-inflammatory Alterations

Numerous studies have reported that prolonged or multiple exposures to anaesthetics in early life lead to detrimental effects on brain function, most having focused on neurocognitive function, and relatively few on long term neuropsychiatric performance. The present study investigated the impact of repeated neonatal isoflurane exposure on chronic variable stress (CVS)-induced psychiatric and behavioural outcomes together with CVS-related neuronal activity and neuro-inflammatory reactivity in relevant brain circuits. In the present study, C57BL/6J mice received either three exposures to isoflurane at postnatal days 7, 8, and 9 or a control exposure. From postnatal day 45, mice were exposed to a mild, 3-week, CVS paradigm or none and the CVS-related neuropsychiatric performance was evaluated using a series of behavioural tests. The neuronal activity in relevant brain regions was measured by ΔFosB immunopositivity and CVS-related neuroinflammation was assessed by analysing levels of pro-inflammatory cytokines IL-1α, IL-1β, IL-6, and TNF-α. In mice experiencing serial neonatal isoflurane exposure, we detected a significant enhancement in anxiety levels following CVS procedures, together with enhanced neuronal activity, and exacerbated neuroinflammation in the basolateral amygdaloid nuclei (BLA) and hippocampal dentate gyrus (DG) regions. No such change was found in control mice. These results indicate an association between early multiple isoflurane exposures in infant mice and susceptibility to a CVS-evoked anxious phenotype accompanied by enhanced neuronal activity in BLA and DG regions and high inflammatory reactivity in response to CVS.

Neuroanesthesiology Update

This review summarizes the literature published in 2020 that is relevant to the perioperative care of neurosurgical patients and patients with neurological diseases as well as critically ill patients with neurological diseases. Broad topics include general perioperative neuroscientific considerations, stroke, traumatic brain injury, monitoring, anesthetic neurotoxicity, and perioperative disorders of cognitive function.

Safety and efficacy of smart tracheal occlusion device in diaphragmatic hernia lamb model

OBJECTIVE

To investigate the efficacy and safety of the 'smart' tracheal occlusion (Smart-TO) device in fetal lambs with diaphragmatic hernia (DH).

METHODS

DH was created in fetal lambs on gestational day 70 (term, 145 days). Fetuses were allocated to either pregnancy continuation until term (DH group) or fetoscopic endoluminal tracheal occlusion (TO), performed using the Smart-TO balloon on gestational day 97 (DH + TO group). On gestational day 116, the presence of the balloon was confirmed on ultrasound, then the ewe was walked around a 3.0-Tesla magnetic resonance scanner for balloon deflation, which was confirmed by ultrasound immediately afterwards. At term, euthanasia was performed and the fetus retrieved. Efficacy of occlusion was assessed by the lung-to-body-weight ratio (LBWR) and lung morphometry. Safety parameters included tracheal side effects assessed by morphometry and balloon location after deflation. The unoccluded DH lambs served as a comparator.

RESULTS

Six fetuses were included in the DH group and seven in the DH + TO group. All balloons deflated successfully and were expelled spontaneously from the airways. In the DH + TO group, in comparison to controls, the LBWR at birth was significantly higher (1.90 (interquartile range (IQR), 1.43-2.55) vs 1.07 (IQR, 0.93-1.46); P = 0.005), while on lung morphometry, the alveolar size was significantly increased (mean linear intercept, 47.5 (IQR, 45.6-48.1) vs 41.9 (IQR, 38.8-46.1) μm; P = 0.03); whereas airway complexity was lower (mean terminal bronchiolar density, 1.56 (IQR, 1.0-1.81) vs 2.23 (IQR, 2.14-2.40) br/mm² ; P = 0.005). Tracheal changes on histology were minimal in both groups, but more noticeable in fetal lambs that underwent TO than in unoccluded lambs (tracheal score, 2 (IQR, 1-3) vs 0 (0-1); P = 0.03).

CONCLUSIONS

In fetal lambs with DH, TO using the Smart-TO balloon is effective and safe. Occlusion can be reversed non-invasively and the deflated intact balloon expelled spontaneously from the fetal upper airways. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.