Anesthetic neurotoxicity in newborns: should we change clinical practice?

Functional measures on PEDI are associated with BSID-3 scales at 2 years, following neonatal surgery

BACKGROUND

Neonates requiring early surgical intervention for major non-cardiac congenital anomalies are at high risk of adverse neurodevelopmental outcomes. Early recognition of potential neuro-developmental delay is critical to facilitate access to early childhood intervention services and therefore maximise the functional capabilities of these children.

AIMS

This study aims to compare Bayley's Scales of Infant and Toddler Development (BSID-3) and the Paediatric Evaluation of Disability Inventory (PEDI) as early screening tools in predicting neuro-developmental disability across multiple domains. In addition, it looks at determining which pre, peri and post-operative risk factors lend themselves to more adverse outcomes.

STUDY DESIGN

Retrospective cohort study.

SUBJECTS

Neonates requiring surgical intervention at the Royal Children's Hospital from 2012 to 2018 who subsequently underwent neurodevelopmental assessment at 2 years of age.

OUTCOME MEASURES

The main outcome was the relationship between performance on the PEDI compared with the BSID-3, in 2-year-olds following neonatal surgery.

RESULTS

Parent -reported functional measures across all domains on PEDI strongly related to the more formal measures of cognition, language, and motor development assessed on BSID-3 (p < 0.05).

CONCLUSIONS

The questionnaire-based PEDI tool could be considered a reliable replacement to the formal Bayley (BSID-3) scale in low-risk infants and provide a more accessible means of assessment where there are deficiencies in availability of suitably trained clinicians or limited resource centres.

Propofol Sedation Washouts in Critically Ill Infants: A Case Series

Medically complex infants are experiencing longer hospital stays, more invasive procedures, and increasingly involved therapeutic interventions that often require long-term analgesia and sedation. This is most commonly achieved with continuous intravenous infusions of opioids and benzodiazepines. There are times when patients develop a tolerance for these medications or the clinical scenario necessitates a rapid wean of them. A rapid wean of either class of medication can lead to increased signs of pain and agitation or withdrawal symptoms. As a result, when a rapid wean is needed or there has been a failure to control symptoms with conventional measures, alternative therapies are considered. Propofol, a sedative hypnotic typically used for general anesthesia and procedural sedation, is one such medication. It has effectively been used for short-term sedation in adults and children to facilitate weaning benzodiazepines and opioids. There is a paucity of data on the use of propofol in infants for this purpose. Here we describe the use of propofol to rapidly wean high-dose sedation and analgesia medications, a propofol sedation washout, in 3 infants. The washouts proved to be safe and efficacious. Based on institutional experience and a literature review, considerations and recommendations are made for propofol sedation washouts in infants.

Perioperative sedation requirements of infants aged 0 to 3 months subjected to lower-body surgery under caudal blockade: a randomized controlled trial

BACKGROUND

It remains unclear how much sedation is required for subumbilical surgery under caudal blockade, and sedatives may carry a poorly understood risk of late sequelae in infants. We designed a randomized controlled study to evaluate total propofol consumption and perioperative sedation quality with the avoidance of continuous perioperative sedation in infants undergoing surgery under caudal anesthesia.

METHODS

Thirty-two infants (age: 0-3 months) were randomized to one of two groups in which perioperative administration of propofol was provided either "as needed" or by continuous infusion (5 mg kg-1 h-1). After induction of anesthesia via a facemask with sevoflurane, a venous access was established and 1 ml kg-1 of ropivacaine 0.35% was injected for caudal anesthesia. Intraoperative stress was assessed by repeated recording Comfort Behavioral Scale scores and heart rates.

RESULTS

Significantly (p = 0.0001) less propofol was administered in the as-needed group (0.7 ± 1.4 mg/kg) than in the continuous-infusion group (3.0 ± 1.6 mg/kg). This difference was not reflected in different requirements of additional intraoperative sedation (0.5 ± 0.8 mg/kg in 5 versus 0.6 ± 1.0 mg/kg in 4 cases; p = 0.76).

CONCLUSIONS

As needed propofol administration offers no disadvantage in terms of intraoperative sedation, but significant dose reductions can be achieved by avoiding continuous propofol infusion.

Neonatal End-of-Life Symptom Management

Purpose of review: Despite advances in technology and treatment options, over 15,000 neonates die each year in the United States. The majority of the deaths, with some estimates as high as 80%, are the result of a planned redirection of care or comfort measures only approach to care. When curative or life-prolonging interventions are not available or have been exhausted, parents focus on preserving quality of life and eliminating needless suffering. Parents hope their child will have a peaceful death and will not feel pain. A significant component of end-of-life care is high quality symptom evaluation and management. It is important that neonatal providers are knowledgeable in symptom management to address common sources of suffering and distress for babies and their families at the end-of-life (EOL). Recent findings: Medically complex neonates with life-threatening conditions are a unique patient population and there is little research on end-of-life symptom assessment and management. While there are tools available to assess symptoms for adolescents and adults, there is not a recognized set of tools for the neonatal population. Nonetheless, it is widely accepted that neonates experience significant symptoms at end-of-life. Most commonly acknowledged manifestations are pain, dyspnea, agitation, and secretions. In the absence of data and established guidelines, there is variability in their clinical management. This contributes to provider discomfort and inadequate symptom control. Summary: End-of-life symptom assessment and management is an important component of neonatal end-of-life care. While there remains a paucity of studies and data, it is prudent that providers adequately manage symptoms. Likewise, it is important that providers are educated so that they can effectively guide families through the dying process by discussing disease progression, physical changes, and providing empathetic support. In this review, the authors make recommendations for non-pharmacological and pharmacological management of end-of-life symptoms in neonates.

[Pain therapy for premature babies and neonates]

Pain is a central topic on neonatal intensive care units (NICU). Acute as well as prolonged (continuous and chronic) pain frequently occurs. Due to a lack of validated physiological measurement instruments for pain (e. g. saliva cortisol, skin conductance and heart rate variability) pain in neonatology can only be assessed by external observation through the bedside team with pain scores using a regular, standardized procedure. During this very vulnerable period pain and medications (analgesics/sedatives) can negatively influence the brain development of premature babies and neonates. Therefore, limitation of the number of pain stimuli and the medicinal guideline "as much as necessary but as little as possible" are eminently important. When dealing with prolonged (continuous and chronic) pain, further challenges are a reduction of analgesics and sedatives as well as avoidance of withdrawal symptoms.

Pediatric anesthesia and neurotoxicity: what the radiologist needs to know

The use of cross-sectional imaging in the pediatric population continues to rise, particularly the use of MRI. Limiting motion artifact requires cooperative subjects who do not move during imaging, so there has been an increase in the need for pediatric sedation or anesthesia. Over the last decade, concern has increased that exposure to anesthesia might be associated with long-term cognitive deficits. In this review we report current understanding of the effects of anesthesia on the pediatric population, with special focus on long-term developmental and cognitive outcomes, and suggest how radiologists can use new technologies or imaging strategies to mitigate or minimize these potential risks.

From Drug-Induced Developmental Neuroapoptosis to Pediatric Anesthetic Neurotoxicity-Where Are We Now?

The fetal and neonatal periods are critical and sensitive periods for neurodevelopment, and involve rapid brain growth in addition to natural programmed cell death (i.e., apoptosis) and synaptic pruning. Apoptosis is an important process for neurodevelopment, preventing redundant, faulty, or unused neurons from cluttering the developing brain. However, animal studies have shown massive neuronal cell death by apoptosis can also be caused by exposure to several classes of drugs, namely gamma-aminobutyric acid (GABA) agonists and N-methyl-d-aspartate (NMDA) antagonists that are commonly used in pediatric anesthesia. This form of neurotoxic insult could cause a major disruption in brain development with the potential to permanently shape behavior and cognitive ability. Evidence does suggest that psychoactive drugs alter neurodevelopment and synaptic plasticity in the animal brain, which, in the human brain, may translate to permanent neurodevelopmental changes associated with long-term intellectual disability. This paper reviews the seminal animal research on drug-induced developmental apoptosis and the subsequent clinical studies that have been conducted thus far. In humans, there is growing evidence that suggests anesthetics have the potential to harm the developing brain, but the long-term outcome is not definitive and causality has not been determined. The consensus is that there is more work to be done using both animal models and human clinical studies.

Multiple Anesthetic Exposure in Infant Monkeys Alters Emotional Reactivity to an Acute Stressor

BACKGROUND

Retrospective studies in humans have shown a higher prevalence of learning disabilities in children that received multiple exposures to general anesthesia before the age of 4 yr. Animal studies, primarily in rodents, have found that postnatal anesthetic exposure causes neurotoxicity and neurocognitive deficits in adulthood. The authors addressed the question of whether repeated postnatal anesthetic exposure was sufficient to cause long-term behavioral changes in a highly translationally relevant rhesus monkey model, allowing study of these variables against a background of protracted nervous system and behavioral development.

METHODS

Rhesus monkeys of both sexes underwent either three 4-h exposures to sevoflurane anesthesia (anesthesia group n = 10) or brief maternal separations (control group n = 10) on postnatal day 6 to 10 that were repeated 14 and 28 days later. Monkeys remained with their mothers in large social groups at all times except for overnight observation after each anesthetic/control procedure. At 6 months of age, each monkey was tested on the human intruder paradigm, a common test for emotional reactivity in nonhuman primates.

RESULTS

The frequency of anxiety-related behaviors was significantly higher in monkeys that were exposed to anesthesia as neonates as compared with controls: anesthesia 11.04 ± 1.68, controls 4.79 ± 0.77, mean ± SEM across all stimulus conditions.

CONCLUSION

Increased emotional behavior in monkeys after anesthesia exposure in infancy may reflect long-term adverse effects of anesthesia.

In vivo and in vitro ketamine exposure exhibits a dose-dependent induction of activity-dependent neuroprotective protein in rat neurons

Anesthetic doses of ketamine induce apoptosis, as well as gene expression of activity-dependent neuroprotective protein (ADNP), a putative homeodomain transcription factor in rat pups (P7). This study investigated if ketamine induced ADNP protein in a dose-dependent manner in vitro and in vivo using primary cultures of cortical neurons and neonatal pups (P7). In vivo immunohistochemistry demonstrated a sub-anesthetic dose of ketamine increased ADNP in the somatosensory cortex (SCC) which was previously identified to be damaged by repeated exposure to anesthetic doses of ketamine. Administration of low-dose ketamine prior to full sedation prevented caspase-3 activation in the hippocampus and SCC. Primary cultures of cortical neurons treated with ketamine (10 μM-10mM) at 3 days-in vitro (3 DIV) displayed a concentration-dependent decrease in expanded growth cones. Furthermore, neuronal production and localization of ADNP varied as a function of both ketamine concentration and length of exposure. Taken together, these data support the model that ADNP induction may be partially responsible for the efficacy of a low-dose ketamine pre-treatment in preventing ketamine-induced neuronal cell death.

Neonatal exposure to sevoflurane causes apoptosis and reduces nNOS protein expression in rat hippocampus

A growing number of studies have shown that commonly used anesthetic agents may cause neurohistopathological changes and persistent behavioral impairments in the developing brain. The effects of sevoflurane, a widely used substance in pediatric anesthesia, on the developing brain have not been thoroughly analyzed thus far. In this study, Sprague-Dawley rats at postnatal day (P)7 were exposed to 2.3% sevoflurane for 6 h continuously. Six hours after exposure, hematoxylin and eosin (H&E) staining was used to determine the morphological changes in the hippocampus. The expression levels of neuronal nitric oxide synthase (nNOS) and caspase-3 in the hippocampus of the pups were determined by immunofluorescence. A single 6-h sevoflurane exposure at P7 caused morphological changes in the hippocampus. Sevoflurane also significantly increased the expression of cleaved caspase-3 and reduced the expression of the nNOS protein. These results indicate that neonatal exposure to sevoflurane causes neurohistopathological changes, apoptosis and decreases nNOS protein levels in the rat hippocampus.

Anesthetic neurotoxicity

Concerns for toxic effects of anesthesia to the brains of the young and the elderly are mounting. While experimental evidence for such effects in the developing brain is strong, the underlying mechanisms are less well understood and debate continues as to whether young humans are at risk for anesthetic neurotoxicity. The phenomenon of postoperative cognitive deterioration in the elderly remains controversial. Time course, severity, and whether or not it persists long term are under debate. For both patient groups, today's evidence is not sufficient to guide change in clinical practice. Well-designed research is therefore imperative to tackle this critical issue.

Improved outcomes in paediatric anaesthesia: contributing factors

PURPOSE

To discuss developments in paediatric anaesthesia and explore the factors which have contributed to improved anaesthetic-related patient outcomes.

METHODS

Narrative review of findings in the literature retrieved from MEDLINE/Pubmed and manual search.

RESULTS

Adverse perioperative outcomes related to anaesthesia have been extensively debated over the past few decades, with studies implicating factors such as major human error and equipment failure. Case series and event registries have enlightened physicians on sources of error and patient risk factors such as extremes of age, comorbidity and emergent circumstances. Anaesthetic-related deaths in children fell from 6.4 per 10,000 anaesthetics in the early 1950s to as low as 0.1 per 10,000 anaesthetics by the end of the century. Advances in anaesthetic agents, techniques, monitoring technologies and training programmes in paediatric anaesthesia play a vital role in driving this downward trend.

CONCLUSION

Despite substantial progress, there is still much room for improvement in areas such as adverse-event reporting, anaesthetic-related risk and late neurocognitive outcomes. Systematic reviews comparing paediatric patient outcomes after neuroaxial block versus general anaesthesia are currently unavailable. The future of paediatric anaesthesia will most likely be influenced by much-needed large prospective studies, which can provide further insight into patient safety and service delivery.

General anesthesia and altered states of arousal: a systems neuroscience analysis

Placing a patient in a state of general anesthesia is crucial for safely and humanely performing most surgical and many nonsurgical procedures. How anesthetic drugs create the state of general anesthesia is considered a major mystery of modern medicine. Unconsciousness, induced by altered arousal and/or cognition, is perhaps the most fascinating behavioral state of general anesthesia. We perform a systems neuroscience analysis of the altered arousal states induced by five classes of intravenous anesthetics by relating their behavioral and physiological features to the molecular targets and neural circuits at which these drugs are purported to act. The altered states of arousal are sedation-unconsciousness, sedation-analgesia, dissociative anesthesia, pharmacologic non-REM sleep, and neuroleptic anesthesia. Each altered arousal state results from the anesthetic drugs acting at multiple targets in the central nervous system. Our analysis shows that general anesthesia is less mysterious than currently believed.

Remifentanil in neonatal intensive care and anaesthesia practice

Remifentanil is a relatively new ultrashort action synthetic opioid. Studies on the use of remifentanil in neonatology have emerged demonstrating its effectiveness and safety in neonates. The present study describes the use of remifentanil in both full-term and premature newborns, highlighting the theoretical benefits for this population in terms of both neonatal intensive care and anaesthesia. A Medline search was undertaken of all reviews and reports about the use of remifentanil in neonates published between 1996 and 2009 using MeSH search terms 'remifentanil', 'analgesia', 'anaesthesia', 'newborn' and 'neonate'. The review points that remifentanil has been used with advantages in newborns including preterm neonates and even for foetal anaesthesia. It proved to be a good option to attenuate the hemodynamic/endocrine markers of stress related to surgery. Owing to its unique pharmacokinetic profile, shorter extubation times can be achieved what makes the drug also a good option for short duration invasive procedures in NICUs (InSurE). A concern on its use is that the hemodynamic response (hypotension) may become significant when the drug is associated to other drugs like sevoflurane.

CONCLUSION

Remifentanil seems to be an effective and safely used opioid for neonatal intensive care and anaesthesia practice.

The young: neuroapoptosis induced by anesthetics and what to do about it

Millions of human fetuses, infants, and children are exposed to anesthetic drugs every year in the United States and throughout the world. Anesthesia administered during critical stages of neurodevelopment has been considered safe and without adverse long-term consequences. However, recent reports provide mounting evidence that exposure of the immature animal brain to anesthetics during the period of rapid synaptogenesis, also known as the brain growth spurt period, triggers widespread apoptotic neurodegeneration, inhibits neurogenesis, and causes significant long-term neurocognitive impairment. Herein, we summarize currently available evidence for anesthesia-induced pathological changes in the brain and associated long-term neurocognitive deficits and discuss promising strategies for protecting the developing brain from the potentially injurious effects of anesthetic drugs while allowing the beneficial actions of these drugs to be realized.

General anesthetics and the developing brain

PURPOSE OF REVIEW

General anesthetics and sedatives are used in millions of children every year to facilitate surgical procedures, imaging studies, and sedation in operating rooms, radiology suites, emergency departments, and ICUs. Mounting evidence from animal studies suggests that prolonged exposure to these compounds may induce widespread neuronal cell death and neurological sequelae, seriously questioning the safety of pediatric anesthesia. This review presents recent developments in this rapidly emerging field.

RECENT FINDINGS

In animals, all currently available anesthetics and sedatives that have been studied, such as ketamine, midazolam, diazepam, clonazepam, propofol, pentobarbital, chloral hydrate, halothane, isoflurane, sevoflurane, enflurane, nitrous oxide, and xenon, have been demonstrated to trigger widespread neurodegeneration in the immature brain. In humans, recent preliminary findings from epidemiological studies suggest an association between surgery and anesthesia early in life and subsequent learning abnormalities.

SUMMARY

Neurodegeneration following exposure to anesthetics and sedatives has been clearly established in developing animals. However, while some of the biochemical pathways have been revealed, the phenomenon's particular molecular mechanisms remain unclear. As the phenomenon is difficult to study in humans, clinical evidence is still scarce and amounts to associative and not causal relationships. Owing to the lack of alternative anesthetics, further animal studies into the mechanism as well as clinical studies defining human susceptibility are both urgently needed.

Is anesthesia bad for the newborn brain?

Although certain data suggest that common general anesthetics may be neurotoxic to immature animals, there are also data suggesting that these same anesthetics may be neuroprotective against hypoxicischemic injury, and that inadequate analgesia during painful procedures may lead to increased neuronal cell death in animals and long-term behavioral changes in humans. The challenge for the pediatric anesthesia community is to design and implement studies in human infants to ascertain the safety of general anesthesia. In this article, the authors review the relevant preclinical and clinical data that are currently available on this topic.

Identification of a fluorescent general anesthetic, 1-aminoanthracene

We identified a fluorophore, 1-aminoanthracene (1-AMA), that is anesthetic, potentiates GABAergic transmission, and gives an appropriate dissociation constant, K(d) approximately 0.1 mM, for binding to the general anesthetic site in horse spleen apoferritin (HSAF). 1-AMA fluorescence is enhanced when bound to HSAF. Thus, displacement of 1-AMA from HSAF by other anesthetics attenuates the fluorescence signal and allows determination of K(d), as validated by isothermal titration calorimetry. This provides a unique fluorescence assay for compound screening and anesthetic discovery. Additional electrophysiology experiments in isolated cells indicate that 1-AMA potentiates chloride currents elicited by GABA, similar to many general anesthetics. Furthermore, 1-AMA reversibly immobilizes stage 45-50 Xenopus laevis tadpoles (EC(50) = 16 microM) and fluorescence micrographs show 1-AMA localized to brain and olfactory regions. Thus, 1-AMA provides an unprecedented opportunity for studying general anesthetic distribution in vivo at the cellular and subcellular levels.

Depth of sedation using Cerebral State Index in infants undergoing spinal anesthesia

BACKGROUND

Infants are noted to frequently sleep during spinal anesthesia, with a concomitant fall in Bispectral Index. However, there are suggestions that EEG derived anesthesia depth monitors have inferior performance in infants. The aim of this study was to quantify the degree of sedation during spinal anesthesia in infants using another EEG derived measure of anesthesia effect--the Cerebral State Index (CSI).

METHODS

Twelve infants, <52 weeks postconceptual menstrual age, scheduled for bilateral inguinal hernia repair under spinal anesthesia were enrolled. Patients received a standard anesthetic protocol with a subarachnoid dose of 1 mg x kg(-1) of levobupivacaine 0.5%. No premedication, sedatives, opioids or anticholinergics were administrated during the perioperative period and patients were left undisturbed during the surgical time, without tactile stimulation or loud auditory stimuli. CSI score (0-100) and bust suppression (BS) (0-100%) were continuously recorded during the surgical time and then statistically re-evaluated.

RESULTS

In all patients the CSI fell during the procedure and there were significant levels of BS recorded by the CSI monitor. The BS occurred between 12 and 34 min after spinal anesthesia with the peak being at 30 min and mean onset time being 15 (2.6) min after spinal block. A statistical significant difference was found between the lowest mean CSI as well as the highest BS if compared with their baseline values. A negative correlation was found between CSI and BS.

CONCLUSIONS

The degree of burst suppression detected by the CSI in our study supports the hypothesis that infants may have discontinuous patterns of EEG during spinal anesthesia similar to those seen during emergence from general anesthesia. Moreover, the limitations in the application of the adult algorithms to infant EEG may lead to an overestimation of the degree of sedation.

Balancing paediatric anaesthesia: preclinical insights into analgesia, hypnosis, neuroprotection, and neurotoxicity

Logistical and ethical reasons make conducting clinical research in paediatric practice difficult, and therefore safe and efficacious advances are dependent on good preclinical research. For example, notable advances have been made in preclinical studies of pain processing that correlate well with patient data. Other areas of paediatric anaesthetic research remain in their infancy including mechanisms of anaesthesia and anaesthetic neuroprotection and neurotoxicity. Animal data have identified the potential 'double-edged' sword of administering anaesthetic agents in the young; although these agents can be neuroprotective in certain circumstances, they can be neurotoxic in others. The potential for this toxicity must be balanced against the importance of providing adequate anaesthesia for which there can be no compromise. We review the current state of preclinical research in paediatric anaesthesia and identify areas which require further exploration in order to provide the foundations for well-conducted clinical trials.

General anesthetic-induced neurotoxicity: an emerging problem for the young and old?

PURPOSE OF REVIEW

A growing body of evidence from cells, rodents, and sub-human primates suggests that general anesthetics can be neurotoxic to the developing and senescent brain. We review this evidence and put the studies into perspective for the practicing clinician.

RECENT FINDINGS

Studies indicate that a variety of general anesthetics, which act primarily as gamma-amino-butyric acid receptor modulators and N-methyl-D-aspartic acid glutamate receptor antagonists, produce apoptotic neurodegeneration in the developing rodent and nonhuman primate brain. Vulnerability to this neurotoxicity is greatest during the period of synaptogenesis and presumably reflects disruption of the normal balance between excitation and inhibition during a critical period of brain development. Moreover, in the rodent, the neurodegeneration is associated with cognitive impairment into adulthood. Recent data also reveal that general anesthesia produces enduring cognitive impairment in aged but not young rodents and that halothane and isoflurane increase the generation and toxicity of amyloid beta, a protein strongly implicated in the pathogenesis of Alzheimer's disease. The meaning of these experimental results for human surgical patients is unclear, however, because human studies are lacking.

SUMMARY

General anesthetics produce neurotoxicity and enduring cognitive impairment in young and aged animals but it is premature to change clinical practice because the issue has not been adequately studied in humans.

Recent Publications on Medications and Pharmacy

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