Anesthesia for cesarean delivery and learning disabilities in a population-based birth cohort

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Duration of exposure to cranial vault surgery: associations with neurodevelopment among children with single-suture craniosynostosis

OBJECTIVE

To evaluate associations between neurodevelopment and exposure to surgery and anesthetic agents in children with single-suture craniosynostosis (SSC).

BACKGROUND

Young children with SSC have unexplained neurodevelopmental delays. The possible contributions of factors related to cranial vault surgery - including anesthesia - have not been previously examined.

METHODS/MATERIALS

Two anesthesiologists reviewed the surgical records of 89 infants (70 had complete data). Primary exposures were duration of surgery and anesthesia and total duration of inhaled anesthesia (at age 6 months on average). Outcomes were the cognitive and motor scores from the Bayley Scales of Infant Development-II and language scores from the Preschool Language Scale, 3rd edition, given at age 36 months. Linear regression using robust standard error estimates was performed, adjusting for age at surgery and suture site.

RESULTS

Anesthesia duration ranged from 155 to 547 min. For every 30-min increase in anesthesia duration, the estimated average decrease in developmental test scores ranged from 1.1 to 2.9 (P ranged from <0.001 to 0.30). Similar, but weaker findings were observed with surgery duration and total duration of inhaled anesthesia. Inverse relations between exposure amounts and neurodevelopment were stronger in children with nonsagittal synostosis.

CONCLUSIONS

Average neurodevelopmental scores were lower among children experiencing longer surgeries and higher exposures to inhaled anesthesia. These associations may be due to anesthesia exposure, nonspecific effects of surgery, or unmeasured variables that correlate with surgery duration. Further study of potential causal mechanisms is warranted.

Effect of general anesthetics on the developing brain

Studies on rodents and subhuman primates suggest that prolonged exposure to general anesthetics 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. There is mounting and convincing preclinical evidence in rodents and nonhuman primates that anesthetics in common clinical use are neurotoxic to the developing brain in vitro and cause long-term neurobehavioral abnormalities in vivo. Prior to the publication of animal data and after the publication of animal data, there are several human cohort studies that demonstrate the association of poor neurodevelopmental outcome in neonates, who underwent major surgery during their neonatal period. This review summarizes our present understanding of some of the key components responsible for anesthesia-induced neuroapoptosis and offers some of neuroprotective strategies that could be beneficial as adjunct therapy in preventing anesthesia-induced death of developing neurons in the neonates. A randomized literature search was carried out using search words apoptosis, general anesthetics, and developing brain from 1979 to 2011 for effects of general anesthetics on developing brain in PUBMED and relevant published literature reviewed. General anesthetics may produce neurotoxicity and enduring cognitive impairment in young and aged animals, but the issue has not been adequately studied in humans. It is premature to recommend a change clinical practice based on the present data.

Pediatric anesthesia and neurodevelopmental impairments: a Bayesian meta-analysis

Experimental evidence of anesthesia-induced neurotoxicity has caused serious concern about the long-term effect of commonly used volatile anesthetic agents on young children. Several observational studies based on existing data have been conducted to address this concern with inconsistent results. We conducted a meta-analysis to synthesize the epidemiologic evidence on the association of anesthesia/surgery with neurodevelopmental outcomes in children. Using Bayesian meta-analytic approaches, we estimated the synthesized odds ratios (OR) and 95% credible interval (CrI) as well as the predictive distribution of a future study given the synthesized evidence. Data on 7 unadjusted and 6 adjusted measures of association were abstracted from 7 studies. The synthesized OR based on the 7 unadjusted measures for the association of anesthesia/surgery with an adverse behavioral or developmental outcome was 1.9 (95% CrI, 1.2-3.0). The most likely unadjusted OR from a future study was estimated to be 2.2 (95% CrI, 0.6-6.1). The synthesized OR based on the 6 adjusted measures for the association of anesthesia/surgery with an adverse behavioral or developmental outcome was 1.4 (95% CrI, 0.9-2.2). The most likely adjusted OR from a future study was estimated to be 1.5 (95% CrI, 0.5-4.0). We conclude that existent epidemiologic evidence suggests a modestly elevated risk of adverse behavioral or developmental outcomes in children who were exposed to anesthesia/surgery during early childhood. The evidence, however, is considerably uncertain.

Long-term differences in language and cognitive function after childhood exposure to anesthesia

BACKGROUND

Over the past decade, the safety of anesthetic agents in children has been questioned after the discovery that immature animals exposed to anesthesia display apoptotic neurodegeneration and long-term cognitive deficiencies. We examined the association between exposure to anesthesia in children under age 3 and outcomes in language, cognitive function, motor skills, and behavior at age 10.

METHODS

We performed an analysis of the Western Australian Pregnancy Cohort (Raine) Study, which includes 2868 children born from 1989 to 1992. Of 2608 children assessed, 321 were exposed to anesthesia before age 3, and 2287 were unexposed.

RESULTS

On average, exposed children had lower scores than their unexposed peers in receptive and expressive language (Clinical Evaluation of Language Fundamentals: Receptive [CELF-R] and Expressive [CELF-E]) and cognition (Colored Progressive Matrices [CPM]). After adjustment for demographic characteristics, exposure to anesthesia was associated with increased risk of disability in language (CELF-R: adjusted risk ratio [aRR], 1.87; 95% confidence interval [CI], 1.20-2.93, CELF-E: aRR, 1.72; 95% CI, 1.12-2.64), and cognition (CPM: aRR, 1.69; 95% CI, 1.13-2.53). An increased aRR for disability in language and cognition persisted even with a single exposure to anesthesia (CELF-R aRR, 2.41; 95% CI, 1.40-4.17, and CPM aRR, 1.73; 95% CI, 1.04-2.88).

CONCLUSIONS

Our results indicate that the association between anesthesia and neuropsychological outcome may be confined to specific domains. Children in our cohort exposed to anesthesia before age 3 had a higher relative risk of language and abstract reasoning deficits at age 10 than unexposed children.

Mechanistic insights into neurotoxicity induced by anesthetics in the developing brain

Compelling evidence has shown that exposure to anesthetics used in the clinic can cause neurodegeneration in the mammalian developing brain, but the basis of this is not clear. Neurotoxicity induced by exposure to anesthestics in early life involves neuroapoptosis and impairment of neurodevelopmental processes such as neurogenesis, synaptogenesis and immature glial development. These effects may subsequently contribute to behavior abnormalities in later life. In this paper, we reviewed the possible mechanisms of anesthetic-induced neurotoxicity based on new in vitro and in vivo findings. Also, we discussed ways to protect against anesthetic-induced neurotoxicity and their implications for exploring cellular and molecular mechanisms of neuroprotection. These findings help in improving our understanding of developmental neurotoxicology and in avoiding adverse neurological outcomes in anesthesia practice.

Are volatile anesthetics neuroprotective or neurotoxic?

Volatile anesthetics are one class of the most commonly used drugs. However, the mechanisms for these drugs to induce anesthesia are not fully understood and have been under intensive investigation. Two other effects of these anesthetics on the central nervous system, volatile anesthetics-induced neuroprotection and neurotoxicity, currently are hot research fields. Although data from animal studies for these two effects are extensive and convincing, clinical data for volatile anesthetics-induced neuroprotection are relatively weak. There is essentially lack of evidence to suggest volatile anesthetics-induced neurotoxicity in humans. In this regard, the contribution of general anesthesia/anesthetics to postoperative cognitive decline, a clinical entity whose existence has been supported by substantial evidence, also has not been established. This paper will be focused on reviewing the evidence, especially the clinical evidence, for volatile anesthetics-induced neuroprotection and neurotoxicity. Efforts will be devoted to facilitating the understanding of the two seemingly contradictory effects of these important drugs on the brain.

Anesthetic-related neurotoxicity and the developing brain: shall we change practice?

Millions of human infants receive general anesthetics for surgery or diagnostic procedures every year worldwide, and there is a growing inquietude regarding the safety of these drugs for the developing brain. In fact, accumulating experimental evidence together with recent epidemiologic observations suggest that general anesthetics might exert undesirable effects on the immature nervous system. The goal of this review is to highlight basic science issues as well as to critically present experimental data and clinical observations relevant to this possibility. By acting on a plethora of ligand-gated ion channels, general anesthetics are powerful modulators of neural activity. Since even brief interference with physiologic activity patterns during critical periods of development are known to induce permanent alterations in brain circuitry, anesthetic-induced interference with brain development is highly plausible. In line with this hypothesis, compelling experimental evidence, from rodents to primates, suggests increased neuroapoptosis and associated long-term neurocognitive deficits following administration of these drugs at defined stages of development. Recent epidemiologic studies also indicate a potential association between anesthesia/surgery and subsequently impaired neurocognitive function in humans. It is, however, important to note that extrapolation of experimental studies to human practice requires extreme caution, and that currently available human data are hindered by a large number of potentially confounding factors. Thus, despite significant advances in the field, there is still insufficient evidence to determine whether anesthetics are harmful to the developing human brain. Consequently, no change in clinical practice can be recommended.

Overview of anesthetic considerations for Cesarean delivery

INTRODUCTION

Physiologic changes of pregnancy uniquely influence anesthesia for Cesarean delivery. Included is a review of current obstetrical anesthesia considerations for Cesarean delivery and recent changes improving maternal care and outcome.

SOURCES OF DATA

A literature review was conducted using Pubmed and the Cochrane database.

AREAS OF AGREEMENT AND CONTROVERSY

Increased use of neuraxial techniques instead of general anesthesia for Cesarean delivery has improved maternal safety. Recent changes in the prevention of gastric aspiration, hypotension from neuraxial techniques, venous thrombosis and a team approach have improved maternal care. Elective Cesarean deliveries and management of urgent deliveries are areas of discussion.

AREAS TIMELY FOR DEVELOPING RESEARCH

Obstetric anesthesia advances have improved maternal outcomes. Current areas of needed obstetric anesthesia research include improved obese patient care, the impact of anticoagulation on neuraxial techniques in pregnancy, long-term neurocognitive effects of neonatal exposure to anesthesia and postoperative pain management.

[Neurological consequences after long-term sedation in the ICU]

Experiments performed in mammals, including non-human primates, have demonstrated an increase in neuronal death rates normally seen in normal brain development. Such an increase is encountered in diseases but also after exposure of the brain to various class of anaesthetics. In living animals, it can (but not always) result in persistent cognitive impairment. Most of the experiments have been conducted in animals which were never exposed to any pain, which questions their relevancy. On the clinical side, all data comes from retrospective studies. Given the multiple bias, they cannot definitely state that a protocol, if toxic, is more or less when compared to another. Until now, prospective follow-up of children exposed to anaesthetics in utero or during the first months of life do not suggest a major deleterious effect. Yet, a minor one, if existing, would be hard to detect among polluting variables (e.g. pathology requiring anaesthesia, long hospitalization after birth, preterm birth, environmental stress...). For sure, when surgery is mandatory during pregnancy, it is generally for maternal indication and should not be a motif strong enough for foetal extraction, especially in terms where the baby has few chances to survive. Second, it is known for years than anaesthesia before 1 year of age is much riskier than after 1 year, whatever the theorical neurotoxicity is. Third, this enforces the need to develop tools enhancing the precision of anaesthesia as much as possible. Meanwhile, when an infant has undergone numerous general anaesthesias, we strongly recommend a long-time neurological follow-up.

Cognitive and behavioral outcomes after early exposure to anesthesia and surgery

BACKGROUND

Annually, millions of children are exposed to anesthetic agents that cause apoptotic neurodegeneration in immature animals. To explore the possible significance of these findings in children, we investigated the association between exposure to anesthesia and subsequent (1) learning disabilities (LDs), (2) receipt of an individualized education program for an emotional/behavior disorder (IEP-EBD), and (3) scores of group-administered achievement tests.

METHODS

This was a matched cohort study in which children (N = 8548) born between January 1, 1976, and December 31, 1982, in Rochester, Minnesota, were the source of cases and controls. Those exposed to anesthesia (n = 350) before the age of 2 were matched to unexposed controls (n = 700) on the basis of known risk factors for LDs. Multivariable analysis adjusted for the burden of illness, and outcomes including LDs, receipt of an IEP-EBD, and the results of group-administered tests of cognition and achievement were outcomes.

RESULTS

Exposure to multiple, but not single, anesthetic/surgery significantly increased the risk of developing LDs (hazard ratio: 2.12 [95% confidence interval: 1.26-3.54]), even when accounting for health status. A similar pattern was observed for decrements in group-administered tests of achievement and cognition. However, exposure did not affect the rate of children receiving an individualized education program.

CONCLUSIONS

Repeated exposure to anesthesia and surgery before the age of 2 was a significant independent risk factor for the later development of LDs but not the need for educational interventions related to emotion/behavior. We cannot exclude the possibility that multiple exposures to anesthesia/surgery at an early age may adversely affect human neurodevelopment with lasting consequence.

Review article: Neurotoxicity of anesthetic drugs in the developing brain

Anesthesia kills neurons in the brain of infantile animals, including primates, and causes permanent and progressive neurocognitive decline. The anesthesia community and regulatory authorities alike are concerned that is also true in humans. In this review, I summarize what we currently know about the risks of pediatric anesthesia to long-term cognitive function. If anesthesia is discovered to cause cognitive decline in humans, we need to know how to prevent and treat it. Prevention requires knowledge of the mechanisms of anesthesia-induced cognitive decline. This review gives an overview of some of the mechanisms that have been proposed for anesthesia-induced cognitive decline and discusses possible treatment options. If anesthesia induces cognitive decline in humans, we need to know what type and duration of anesthetic is safe, and which, if any, is not safe. This review discusses early results of comparative animal studies of anesthetic neurotoxicity. Until we know if and how pediatric anesthesia affects cognition in humans, a change in anesthetic practice would be premature, not guided by evidence of better alternatives, and therefore potentially dangerous. The SmartTots initiative jointly supported by the International Anesthesia Research Society and the Food and Drug Administration aims to fund research designed to shed light on these issues that are of high priority to the anesthesia community and the public alike and therefore deserves the full support of these interest groups.

Outcome for the extremely premature neonate: how far do we push the edge?

Significant advances in perinatal and neonatal medicine over the last 20 years and the recent emergence of fetal surgery has resulted in anesthesia providers caring for a growing number of infants born at the margin of viability. Anesthetic management in this patient population has to take into consideration the immature function of many vital organ systems as well as the effects of the underlying disease processes, which can frequently lead to severe physiological derangements. Accordingly, premature infants presenting for major surgeries early in life can represent a significant anesthetic challenge. However, even with advanced anesthetic and surgical management and optimal intensive care, extremely premature infants face substantial postoperative morbidity and mortality, as well as prolonged hospital courses. In this article, we will discuss the following questions: How far have we come in improving outcomes of extreme prematurity? And what will the future medical and societal challenges be, as we continue to redefine the limits of viability?

Anesthesia and neurotoxicity to the developing brain: the clinical relevance

Laboratory work has confirmed that general anesthetics cause increased neuronal apoptosis and changes to the morphology of dendritic spines in the developing brains of animals. It is an effect seen with most volatile anesthetics as well as with ketamine and propofol. The effects are dose dependent and seen over particular periods of early development. There is some evidence that rodents exposed to anesthesia during infancy have delayed neurobehavioral development. There are inherent limitations in translating the preclinical data to human practice but the data cannot be ignored. Some human clinical studies have found evidence for an association between major surgery and changes in neurobehavioral outcome, although the evidence is less clear for minor surgery. These associations are certainly at least partly because of factors apart from anesthesia, such as coexisting pathology or the effect of surgery itself. Other clinical studies have found no evidence for an association between surgery and outcome. These studies are also not without limitations. Thus it remains unclear what role anesthesia exposure in infancy actually plays in determining neurobehavioral outcome. To date studies can neither confirm that anesthesia plays a role nor rule it out.

Rats exposed to isoflurane in utero during early gestation are behaviorally abnormal as adults

BACKGROUND

Preclinical evidence suggests that commonly used anesthetic agents induce long-lasting neurobehavioral changes when administered early in life, but there has been virtually no attention to the neurodevelopmental consequences for the fetus of maternal anesthesia. This study tested the hypothesis that fetal rats exposed to isoflurane during maternal anesthesia on gestational day 14, which corresponds to the second trimester in humans, would be behaviorally abnormal as adults.

METHODS

Timed, pregnant rats were randomly assigned on gestational day 14 to receive 1.4% isoflurane in 100% oxygen (n = 3) or 100% oxygen (n = 2) for 4 h. Beginning at 8 weeks of age, male offspring (N = 12-14 in control and anesthesia groups, respectively) were evaluated for spontaneous locomotor activity, hippocampal-dependent learning and memory (i.e., spontaneous alternations, novel object recognition, and radial arm maze), and anxiety (elevated plus maze).

RESULTS

Isoflurane anesthesia was physiologically well tolerated by the dams. Adult rats exposed prenatally to isoflurane were not different than controls on spontaneous locomotor activity, spontaneous alternations, or object recognition memory, but made more open arm entries on the elevated plus maze and took longer and made more errors of omission on the radial arm maze.

CONCLUSIONS

Rats exposed to isoflurane in utero at a time that corresponds to the second trimester in humans have impaired spatial memory acquisition and reduced anxiety, compared with controls. This suggests the fetal brain may be adversely affected by maternal anesthesia, and raises the possibility that vulnerability to deleterious neurodevelopmental effects of isoflurane begins much earlier in life than previously recognized.

Early childhood exposure to anesthesia and risk of developmental and behavioral disorders in a sibling birth cohort

BACKGROUND

In vitro and in vivo studies of anesthetics have demonstrated serious neurotoxic effects on the developing brain. However, the clinical relevance of these findings to children undergoing anesthesia remains unclear. Using data from a sibling birth cohort, we assessed the association between exposure to anesthesia in the setting of surgery in patients younger than 3 years and the risk of developmental and behavioral disorders.

METHODS

We constructed a retrospective cohort of 10,450 siblings who were born between 1999 and 2005 and who were enrolled in the New York State Medicaid program. The exposed group was 304 children without a history of developmental or behavioral disorders who underwent surgery when they were younger than 3 years. The unexposed group was 10,146 children who did not receive any surgical procedures when they were younger than 3 years. Exposed children were entered into analysis at the date of surgery. Unexposed children were entered into analysis at age 10 months (the mean age at which exposed children underwent surgery). Both exposed and unexposed children were followed until diagnosis with a developmental or behavioral disorder, loss to follow-up, or the end of 2005. The association of exposure to anesthesia with subsequent developmental and behavioral disorders was assessed with both proportional hazards modeling, and pair-matched analysis.

RESULTS

The incidence of developmental and behavioral disorders was 128.2 diagnoses per 1000 person-years for the exposed cohort and 56.3 diagnoses per 1000 person-years for the unexposed cohort. With adjustment for sex and history of birth-related medical complications, and clustering by sibling status, the estimated hazard ratio of developmental or behavioral disorders associated with any exposure to anesthesia when they were younger than 3 years was 1.6 (95% confidence interval [CI]: 1.4, 1.8). The risk increased from 1.1 (95% CI: 0.8, 1.4) for 1 operation to 2.9 (94% CI: 2.5, 3.1) for 2 operations and 4.0 (95% CI: 3.5, 4.5) for ≥3 operations. The relative risk in a matched analysis of 138 sibling pairs was 0.9 (95% CI: 0.6, 1.4).

CONCLUSION

The risk of being subsequently diagnosed with developmental and behavioral disorders in children who were enrolled in a state Medicaid program and who had surgery when they were younger than 3 years was 60% greater than that of a similar group of siblings who did not undergo surgery. More tightly matched pairwise analyses indicate that the extent to which the excess risk is causally attributable to anesthesia or mediated by unmeasured factors remains to be determined.

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.

Early childhood general anaesthesia exposure and neurocognitive development

A great deal of concern has recently arisen regarding the safety of anaesthesia in infants and children. There is mounting and convincing preclinical evidence in rodents and non-human primates that anaesthetics in common clinical use are neurotoxic to the developing brain in vitro and cause long-term neurobehavioural abnormalities in vivo. An estimated 6 million children (including 1.5 million infants) undergo surgery and anaesthesia each year in the USA alone, so the clinical relevance of anaesthetic neurotoxicity is an urgent matter of public health. Clinical studies that have been conducted on the long-term neurodevelopmental effects of anaesthetic agents in infants and children are retrospective analyses of existing data. Two large-scale clinical studies are currently underway to further address this issue. The PANDA study is a large-scale, multisite, ambi-directional sibling-matched cohort study in the USA. The aim of this study is to examine the neurodevelopmental effects of exposure to general anaesthesia during inguinal hernia surgery before 36 months of age. Another large-scale study is the GAS study, which will compare the neurodevelopmental outcome between two anaesthetic techniques, general sevoflurane anaesthesia and regional anaesthesia, in infants undergoing inguinal hernia repair. These study results should contribute significant information related to anaesthetic neurotoxicity in children.

Evidence for the need for anaesthesia in the neonate

Neonates are both capable of experiencing pain and memory formation, albeit implicit memory. During surgical procedures, insufficient ablation of the stress response and possible implicit memory formation of intra-operative events might result in adverse early and long-term outcomes. Neonates deserve the same respect as adult patients. It is thus the responsibility of the anaesthetist to provide sufficient anaesthesia for neonates undergoing surgery. A critical approach in weighing the risks and benefits of exposing a neonate to anaesthesia is prudent, and truly elective surgery should be delayed.

The impact of the perioperative period on neurocognitive development, with a focus on pharmacological concerns

Mounting evidence from animal studies has implicated that all commonly used anaesthetics and sedatives may induce widespread neuronal cell death and result in long-term neurological abnormalities. These findings have led to serious questions regarding the safe use of these drugs in young children. In humans, recent findings from retrospective, epidemiological studies do not exclude the possibility of an association between surgery with anaesthesia early in life and subsequent learning abnormalities. These results have sparked discussions regarding the appropriate timing of paediatric surgery and the safe management of paediatric anaesthesia. However, important questions need to be addressed before findings from laboratory studies and retrospective clinical surveys can be used to guide clinical practice. This article summarises the currently available preclinical and clinical information regarding the impact of anaesthetics, sedatives, opioids, pain and stress, inflammation, hypoxia-ischaemia, co-morbidities and genetic predisposition on brain structure and long-term neurological function. Moreover, this article outlines the putative mechanisms of anaesthetic neurotoxicity, and the phenomenon's implications for clinical practice in this rapidly emerging field.

Mechanisms of general anesthetic action: Focus on the cellular network

The discovery of general anesthetics had a tremendous impact on development of surgery and medicine in general, during the last century. Despite the widespread use of general anesthetics, the mechanisms by which they produce their effects in the central nervous system are still poorly understood. Over the past decade, several new findings have contributed significantly to a better understanding of general anesthetic mechanisms. The current review summarizes recent data on different anesthetic neuronal targets that might be involved in the mechanism of action of general anesthetics, giving special attention to the importance of binding pockets for anesthetics within transmembrane receptors and cellular signaling leading to morphological changes of neuronal cells. Several lines of evidence suggest that disruption in brain network connectivity is important for anaesthesia-induced loss of consciousness and this is discussed in relation to morphological changes.

General anesthesia for cesarean delivery at a tertiary care hospital from 2000 to 2005: a retrospective analysis and 10-year update

BACKGROUND

Complications from general anesthesia for cesarean delivery are a leading cause of anesthesia-related mortality. As a consequence, the overall use of general anesthesia in this setting is becoming less common. The impact and implications of this trend are considered in relation to a similar study performed at our institution 10 years ago.

METHODS

The hospital database for all cesarean deliveries performed during six calendar years (January 1, 2000 through December 31, 2005) was reviewed. The medical records of all parturients who received general anesthesia were examined to collect personal details and data pertinent to the indications for cesarean delivery and general anesthesia, mode of airway management and associated anesthetic complications.

RESULTS

Cesarean deliveries accounted for 23.65% to 31.51% of an annual total ranging from 8543 to 10091 deliveries. The percentage of cases performed under general anesthesia ranged from 0.5% to 1%. A perceived lack of time for neuraxial anesthesia accounted for more than half of the general anesthesia cases each year, with maternal factors accounting for 11.1% to 42.9%. Failures of neuraxial techniques accounted for less than 4% of the general anesthesia cases. There was only one case of difficult intubation and no anesthesia-related mortality was recorded.

CONCLUSION

The use of general anesthesia for cesarean delivery is low and declining. These trends may reflect the early and increasing use of neuraxial techniques, particularly in parturients with co-existing morbidities. A significant reduction in exposure of trainees to obstetric general anesthesia has been observed.

Developing brain and general anesthesia - is there a cause for concern?

Skilled management of sick premature babies and very young children has resulted in numerous exposures of their brains to a variety of anesthetic agents designed to achieve the substantial depth of neuronal inhibition required for complete loss of consciousness and insensitivity to pain. Unfortunately, our recent animal findings suggest that commonly used general anesthetics are damaging to developing neurons and cause significant neuronal deletion in vulnerable brain regions. In addition, emerging animal and human data suggest an association between early exposure to general anesthesia and long-term impairment of cognitive development. Consequently, the prudence of frequent anesthesia exposure of this population is now being scrutinized. It is important to note that on the basis of currently available information, there are still considerable differences of opinion regarding the clinical relevance of the animal findings. Since there is insufficient evidence establishing a clear association between animal and human findings, it would be premature to suggest major changes in current clinical practice.

Neuraxial labor analgesia for vaginal delivery and its effects on childhood learning disabilities

BACKGROUND

In prior work, children born to mothers who received neuraxial anesthesia for cesarean delivery had a lower incidence of subsequent learning disabilities compared with vaginal delivery. The authors speculated that neuraxial anesthesia may reduce stress responses to delivery, which could affect subsequent neurodevelopmental outcomes. To further explore this possibility, we examined the association between the use of neuraxial labor analgesia and development of childhood learning disabilities in a population-based birth cohort of children delivered vaginally.

METHODS

The educational and medical records of all children born to mothers residing in the area of 5 townships of Olmsted County, Minnesota from 1976 to 1982 and remaining in the community at age 5 years were reviewed to identify those with learning disabilities. Cox proportional hazards regression was used to compare the incidence of learning disabilities between children delivered vaginally with and without neuraxial labor analgesia, including analyses adjusted for factors of either potential clinical relevance or that differed between the 2 groups in univariate analysis.

RESULTS

Of the study cohort, 4684 mothers delivered children vaginally, with 1495 receiving neuraxial labor analgesia. The presence of childhood learning disabilities in the cohort was not associated with use of labor neuraxial analgesia (adjusted hazard ratio, 1.05; 95%confidence interval, 0.85-1.31; P = 0.63).

CONCLUSION

The use of neuraxial analgesia during labor and vaginal delivery was not independently associated with learning disabilities diagnosed before age 19 years. Future studies are needed to evaluate potential mechanisms of the previous finding indicating that the incidence of learning disabilities is lower in children born to mothers via cesarean delivery under neuraxial anesthesia compared with vaginal delivery.

[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.