Anaesthetic neurotoxicity and neuroplasticity: an expert group report and statement based on the BJA Salzburg Seminar

Although previously considered entirely reversible, general anaesthesia is now being viewed as a potentially significant risk to cognitive performance at both extremes of age. A large body of preclinical as well as some retrospective clinical evidence suggest that exposure to general anaesthesia could be detrimental to cognitive development in young subjects, and might also contribute to accelerated cognitive decline in the elderly. A group of experts in anaesthetic neuropharmacology and neurotoxicity convened in Salzburg, Austria for the BJA Salzburg Seminar on Anaesthetic Neurotoxicity and Neuroplasticity. This focused workshop was sponsored by the British Journal of Anaesthesia to review and critically assess currently available evidence from animal and human studies, and to consider the direction of future research. It was concluded that mounting evidence from preclinical studies reveals general anaesthetics to be powerful modulators of neuronal development and function, which could contribute to detrimental behavioural outcomes. However, definitive clinical data remain elusive. Since general anaesthesia often cannot be avoided regardless of patient age, it is important to understand the complex mechanisms and effects involved in anaesthesia-induced neurotoxicity, and to develop strategies for avoiding or limiting potential brain injury through evidence-based approaches.

β-Ionone arrests cell cycle of gastric carcinoma cancer cells by a MAPK pathway

β-Ionone is an end ring analog of β-carotenoid which has been shown to possess potent anti-proliferative activity both in vitro and in vivo. To investigate the possible inhibitory effects of β-ionone, we studied cell growth characteristics, DNA synthesis, cell cycle progression, as well as mitogen-activated protein kinases (MAPKs) pathways in the human gastric adenocarcinoma cancer cell line (SGC-7901). Our results show that cell growth and DNA synthesis were inhibited, and the cell cycle was arrested at the G0/G1 phase in a dose-dependent manner in cells treated with β-ionone (25, 50, 100 and 200 μmol/L) for 24 h. We found that the β-ionone significantly decreased the extracellular signal-regulated kinase protein expression and significantly increased the levels of p38 and Jun-amino-terminal kinase protein expression (P < 0.01). β-Ionone also inhibited cell cycle-related proteins of Cdk4, Cyclin B1, D1 and increased p27 protein expression in SGC-7901 cells. These results suggested that the cell cycle arrest observed may be regulated through a MAPK pathway by transcriptional down-regulation of cell cycle proteins. These results demonstrate potent ability of β-ionone to arrest cell cycle of SGC-7901 cells and decrease proliferation.

Perioperative central nervous system injury in neonates

Anaesthetic-induced developmental neurotoxicity (AIDN) has been clearly established in laboratory animal models. The possibility of neurotoxicity during uneventful anaesthetic procedures in human neonates or infants has led to serious questions about the safety of paediatric anaesthesia. However, the applicability of animal data to clinical anaesthesia practice remains uncertain. The spectre of cerebral injury due to cerebral hypoperfusion, metabolic derangements, coexisting disease, and surgery itself further muddles the picture. Given the potential magnitude of the public health importance of this issue, the clinician should be cognisant of the literature and ongoing investigations on AIDN, and raise awareness of the risks of both surgery and anaesthesia.

Morphine-enhanced apoptosis in selective brain regions of neonatal rats

Prolonged neonatal opioid exposure has been associated with: antinociceptive tolerance, long-term neurodevelopmental delay, cognitive, and motor impairment. Morphine has also been shown to induce apoptotic cell death in vitro studies, but its in vivo effect in developing rat brain is unknown. Thus, we hypothesized that prolongued morphine administration in neonatal rats in a model of antinociceptive tolerance and dependence is associated with increased neuroapoptosis. We analyzed neonatal rats from the following groups (1) naïve group (n=6); (2) control group (normal saline (NS), n=5), and (3) morphine group (n=8). Morphine sulfate or equal volume of NS was injected subcutaneously twice daily for 6½ days starting on postnatal day (PD) 1. Development of antinociceptive tolerance was previously confirmed by Hot Plate test on the 7th day. Evidence of neuronal and glial apoptosis was determined by cleaved caspase-3 immunofluorescence combined with specific markers. At PD7, morphine administration after 6½ days significantly increased the density of apoptotic cells in the cortex and amygdala, but not in the hippocampus, hypothalamus, or periaqueductal gray. Apoptotic cells exhibited morphology analogous to neurons. Irrespective of the treatment, only a very few individual microglia but not astrocytes were caspase-3 positive. In summary, repeated morphine administration in neonatal rats (PD1-7) is associated with increased supraspinal apoptosis in distinct anatomical regions known to be important for sensory (cortex) and emotional memory processing (amygdala). Brain regions important for learning (hippocampus), and autonomic and nociceptive processing (hypothalamus and periaqueductal gray) were not affected. Lack of widespread glial apoptosis or robust glial activation following repeated morphine administration suggests that glia might not be affected by chronic morphine at this early age. Future studies should investigate long-term behavioral sequelae of demonstrated enhanced apoptosis associated with prolonged morphine administration in a neonatal rat model.

Sedative drug modulates T-cell and lymphocyte function-associated antigen-1 function

BACKGROUND

Sedative drugs modify immune cell functions via several mechanisms. However, the effects of sedatives on immune function have been primarily investigated in neutrophils and macrophages, and to the lesser extent lymphocytes. Lymphocyte function-associated antigen-1 (LFA-1) is an adhesion molecule that has a central role in regulating immune function of lymphocytes including interleukin-2 (IL-2) production and lymphocyte proliferation. Previous clinical studies reported that propofol and isoflurane reduced IL-2 level in patients, but midazolam did not. We previously demonstrated that isoflurane inhibited LFA-1 binding to its counter ligand, intercellular adhesion molecule-1 (ICAM-1), which might contribute to the reduction of IL-2 levels. In the current study, we examined the effect of propofol, midazolam, and dexmedetomidine on LFA-1/ICAM-1 binding, and the subsequent biological effects.

METHODS

The effect of sedative drugs on T-cell proliferation and IL-2 production was measured by calorimetric assays on human peripheral blood mononuclear cells. Because LFA-1/ICAM-1 binding has an important role in T-cell proliferation and IL-2 production, we measured the effect of sedative drugs on ICAM-1 binding to LFA-1 protein (cell-free assay). This analysis was followed by flow cytometric analysis of LFA-1 expressing T-cell binding to ICAM-1 (cell-based assay). To determine whether the drug/LFA-1 interaction is caused by competitive or allosteric inhibition, we analyzed the sedative drug effect on wild-type and high-affinity LFA-1 and a panel of monoclonal antibodies that bind to different regions of LFA-1.

RESULTS

Propofol at 10 to 100 μM inhibited ICAM-1 binding to LFA-1 in cell-free assays and cell-based assays (P < 0.05). However, dexmedetomidine and midazolam did not affect LFA-1/ICAM-1 binding. Propofol directly inhibits LFA-1 binding to ICAM-1 by binding near the ICAM-1 contact area in a competitive manner. At clinically relevant concentrations, propofol, but not dexmedetomidine or midazolam, inhibited IL-2 production (P < 0.05). Additionally, propofol inhibited lymphocyte proliferation (P < 0.05).

CONCLUSIONS

Our study suggests that propofol competitively inhibits LFA-1 binding to ICAM-1 on T-cells and suppresses T-cell proliferation and IL-2 production, whereas dexmedetomidine and midazolam do not significantly influence these immunological assays.

Endoscopic strip craniectomy in early infancy: the initial five years of anesthesia experience

BACKGROUND

Minimally invasive endoscopic strip craniectomy (ESC) is a relatively new surgical technique for treating craniosynostosis in early infancy. In this study we reviewed our anesthesia experience with ESC. The hypothesis was that infants with low body weight and syndromes would have a higher risk of perioperative blood transfusion and that those with respiratory complications are more likely to be admitted to the intensive care unit (ICU).

METHODS

We retrospectively reviewed patient charts and anesthesia records of the first 100 consecutive infants who underwent ESC between May 2004 and December 2008 and follow-up evaluations until December 2009. Outcomes included (a) perioperative blood transfusion, (b) venous air embolism (VAE), (c) ICU admission, and (d) reoperation with craniofacial reconstruction procedures. Multivariable logistic regression was used to determine significant factors of patient outcomes.

RESULTS

Infants ranging from 4 to 34 weeks of age (weight: 3.2 to 10.1 kg), presented for 87 single and 13 multiple ESC. Four infants had a craniofacial syndrome. The mean surgical time was 48 minutes (range: 26 to 86 minutes). Ninety-two infants had a median estimated blood loss of 23 mL (interquartile ranges [IQR]: 15 to 30 mL). Eight infants who required blood transfusion received a median amount of 17.2 mL/kg (IQR: 10.1 to 21.2 mL/kg). Body weight ≤5 kg (P = 0.04), sagittal ESC (P < 0.01), syndromic craniosynostosis (P < 0.01), and earlier date of surgery in the series (P < 0.01) were factors associated with blood transfusion. VAE was detected in 2 infants with no changes in clinical outcome. Eight infants were admitted to the ICU. Factors associated with ICU admission were blood transfusion (P < 0.001) and respiratory complications (P < 0.001). Eighty-two infants were discharged on postoperative day 1 (range: 1 to 3 days). Six infants underwent subsequent fronto-orbital advancement and 1 cranial vault reconstruction. Multiple-suture craniosynostosis (P < 0.01), associated syndromes (P = 0.03), and ICU admission after ESC (P = 0.04) were predictive of reoperation.

CONCLUSIONS

Twenty percent of infants undergoing ESC had 1 or more of the following: need for blood transfusion, VAE, respiratory complications, and ICU admission. Multivariable analysis confirmed that patients with lower body weight, those with earlier date of surgery in the series, those undergoing sagittal ESC, and those with syndromic craniosynostosis had a higher rate of blood transfusion. ICU admissions often occurred in infants requiring transfusion and those with respiratory complications. Infants with multiple-suture craniosynostosis were more likely to require subsequent craniofacial reconstruction procedures.

Detection of intestinal inflammation by MicroPET imaging using a (64)Cu-labeled anti-beta(7) integrin antibody

BACKGROUND

The primary function of integrin beta(7) is the recruitment and retention of lymphocytes to the inflamed gut. The aim of this study was to investigate the possibility of imaging colitis radioimmunodetection by targeting the beta(7) integrin with a radiolabeled antibody.

METHODS

FIB504.64, a monoclonal antibody that binds to beta(7) integrin, was conjugated with a bifunctional chelator and labeled with (64)Cu. The antibody (50 microg, 7 MBq) was injected into C57BL/6 mice with experimentally induced colitis (n = 6). MicroPET images were collected at 1, 24, and 48 hours postinjection and the biodistribution was measured at 48 hours by tissue assay. Data were also obtained for a (64)Cu-labeled nonspecific isotype-matched antibody in mice with colitis and (64)Cu-labeled FIB504.64 in healthy mice (n = 5-6).

RESULTS

The microPET images showed higher uptake of (64)Cu-labeled FIB504.64 in the gut of mice with colitis than for either of the controls. This observation was confirmed by the 48-hour ex vivo biodistribution data: the percentage of injected dose per gram of tissue (%ID/g +/- SD) (large intestine) colitis mice with (64)Cu-labeled FIB504.64, 6.49 +/- 2.25; control mice with (64)Cu-labeled FIB504.64, 3.64 +/- 1.12; colitis mice, (64)Cu-labeled nonspecific antibody 3.97 +/- 0.48%ID/g (P < 0.05 between groups).

CONCLUSIONS

The selective uptake of (64)Cu-labeled FIB504.64 antibody in the gut of animals with colitis suggests that integrin beta(7) may be a promising target for radioimmunodetection of this disease, which would aid diagnosis, assessment, and therapy guidance of this disease.

Acute intraoperative neurogenic pulmonary edema during endoscopic ventriculoperitoneal shunt revision

We present an incident of fulminant intraoperative neurogenic pulmonary edema in a 21-yr-old man undergoing an endoscopic ventriculoperitoneal shunt revision. His intraoperative course was complicated by intracranial bleeding requiring vigorous saline irrigation, which was accompanied by an acute increase in heart rate and arterial blood pressure. Shortly thereafter, the patient developed pulmonary edema and was promptly treated with resolution of pulmonary symptoms within 24 h. This report addresses the importance of recognition of neurogenic pulmonary edema as a possible intraoperative complication resulting from an increase in intracranial pressure due to hemorrhage and intraventricular irrigation during endoscopic ventriculoperitoneal shunt revision.

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.

Prolonged exposure to ketamine increases brain derived neurotrophic factor levels in developing rat brains

Prolonged exposure to ketamine, a NMDA receptor antagonist, results in accelerated neurodegeneration and attenuated weight gain in neonatal rats. Suppression of the NMDA receptors by non-competitive antagonists has resulted in conflicting reports of both increased and decreased expression of BDNF. To examine the effect of prolonged ketamine exposure on BDNF expression, we administered saline or ketamine (20 mg/kg) at 90-minute intervals over 9 hours to postnatal day 7 (P7) rat pups. The ketamine-treated rat pups had increased neurodegeneration, BDNF and TrkB cDNA products and protein levels. This increased expression of BDNF may be a response to ketamine-induced injury.

Clinical research approaches to studying pediatric anesthetic neurotoxicity

Neuronal cell death after general anesthesia has recently been demonstrated in neonatal animal models. The possibility of anesthesia-induced neurotoxicity during an uneventful anesthetic procedure in human neonates or infants has led to serious questions about the safety of pediatric anesthesia. However, the applicability of animal data to clinical anesthesia practice remains uncertain. This paper examines the evidence for the effects of commonly used anesthetics on neuronal structure and neurocognitive function in laboratory models and evaluates its relevance to clinical care in humans. Published retrospective reviews demonstrate temporary neurological sequelae after prolonged anesthetic exposure in young children and larger studies identify long-term neurodevelopmental impairment after neonatal surgery and anesthesia. However, there are no prospective studies evaluating neurocognitive function in children after neonatal exposure to anesthetics. Given the potential magnitude of the public health importance of this issue, this review also discusses epidemiological approaches and several ongoing prospective studies that are assessing the long-term neurocognitive effects of general anesthesia on the neonate.

The volatile anesthetic isoflurane perturbs conformational activation of integrin LFA-1 by binding to the allosteric regulatory cavity

The molecular and structural basis of anesthetic interactions with conformations and functionalities of cell surface receptors remains to be elucidated. We have demonstrated that the widely used volatile anesthetic isoflurane blocks the activation-dependent conformational conversion of integrin lymphocyte function associated antigen-1 (LFA-1), the major leukocyte cell adhesion molecule, to a high-affinity configuration. Perturbation of LFA-1 activation by isoflurane at clinically relevant concentrations leads to the inhibition of T-cell interactions with target cells as well as ligand-triggered intracellular signaling. Nuclear magnetic resonance spectroscopy reveals that isoflurane binds within a cavity in the LFA-1 ligand-binding domain, which is a previously identified drug-binding site for allosteric small-molecule antagonists that stabilize LFA-1 in a low-affinity conformation. These results provide a potential mechanism for the immunomodulatory properties of isoflurane.

Detection of unanticipated intracranial hemorrhage during intraoperative magnetic resonance image-guided neurosurgery. Report of two cases

The authors report unanticipated intraoperative intracranial hemorrhaging in two pediatric neurosurgical patients. Both children were undergoing elective craniotomies with the aid of intraoperative magnetic resonance (iMR) imaging. In both cases, the ability of iMR imaging to aid in diagnosis allowed prompt and definitive treatment of potentially life-threatening complications. These cases illustrate the ability of iMR imaging to aid in differentiating unexpected and/or unexplained intraoperative events in pediatric neurosurgery.

Pediatric Neuroanesthesia

Recent advances in pediatric neurosurgery have drastically improved the outcome in infants and children afflicted with surgical lesions of the central nervous system (CNS). Because most of these techniques were first applied to adults, the physiologic and developmental differences that are inherent in pediatric patients present challenges to neurosurgeons and anesthesiologists alike. The aim of this paper is to highlight these age-dependent approaches to the pediatric neurosurgical patient.

Lidocaine pretreatment for the prevention of propofol-induced transient motor disturbances in children during anesthesia induction: a randomized controlled trial in children undergoing invasive hematologic procedures

BACKGROUND

We examined the effect of lidocaine pretreatment before propofol administration on the incidence of transient motor disturbances and on propofol requirements for anesthesia induction in infants and children undergoing repeated painful diagnostic and therapeutic hematological procedures.

METHODS

A series of 358 children subgrouped according to the presence of a peripheral-vein or central venous catheter were randomly assigned to receive an intravenous dose of 2% lidocaine (2.0 mg.kg(-1)) or an equivalent volume of saline, 1 min before propofol (1.5-3.5 mg.kg(-1)) injected for anesthesia induction.

RESULTS

The incidence of spontaneous movements was significantly lower in patients pretreated with lidocaine than in those receiving placebo (2.5% vs 29%; P < 0.001, by chi-square test), as was the propofol induction dose (1.6 +/- 0.2 mg.kg(-1) vs 2.2 +/- 0.3 mg.kg(-1); P < 0.001) and pain at the injection site in patients peripheral-vein catheter (12% vs. 54%; P < 0.001). Lidocaine administration also improved children's acceptance as reported by parents on the Observational Scale of Behavioral Distress administered 2 h after the procedure (6.5 +/- 2.5 vs. 9.4 +/- 3.3; P < 0.001). Bouts of coughing developed significantly more frequently after lidocaine pretreatment than after placebo (62.5% vs. 17.5%; P < 0.001).

CONCLUSIONS

Because lidocaine pretreatment before the induction of propofol-based anesthesia decreases propofol-induced motor disturbances, lowers hypnotic requirements and reduces pain at the injection site, without inducing untoward events, thus improving children's and parental acceptance, it should become standard practice in infants and children undergoing repeated painful diagnostic and therapeutic hematological procedures.

Anesthesia for epilepsy surgery in children

BACKGROUND

The perioperative management of infants and children for epilepsy surgery should focus on the specific problems unique to the state of the disease, age of the child, and operative conditions. A basic understanding of age-dependent variables and the interaction of anesthetic and surgical procedures are essential in minimizing perioperative morbidity and mortality. Specific medical conditions that impact the conduct of anesthesia include congenital anomalies, chronic anticonvulsant therapies, and evolving coagulopathies. The neurosurgical procedure and neurophysiological monitoring will determine the type of anesthetic technique to be utilized during surgery.

OBJECTIVE

This review will provide a systematic approach to pediatric patients undergoing epilepsy surgery.

Anesthesia and analgesia during and after surgery in neonates

BACKGROUND

Historically, the use of anesthetics and analgesics in neonates and infants has been based on extrapolations from studies performed in adults and older children. Over the past 20 years, there has been a growing body of research on the clinical pharmacology and clinical outcomes of these agents in neonates and infants.

OBJECTIVE

This article summarizes clinical pharmacology and clinical outcomes studies of opioids, opioid antagonists, sedative-hypnotics, nonsteroidal anti-inflammatory drugs and acetaminophen, and local anesthetics in neonates and infants to highlight gaps in the available knowledge, review some concerns about study design, and identify drugs that should receive high priority for future study.

METHODS

Relevant studies were identified through a search of MEDLINE and a review of textbooks, conference proceedings, and abstracts. The available literature was subjected to expert committee-based review.

CONCLUSIONS

There is a growing body of information on analgesic and anesthetic pharmacokinetics, pharmacodynamics, and clinical outcomes in neonates and infants, permitting safe and effective use in some clinical settings. Major gaps in knowledge persist, however. Future research may involve a combination of clinical trials and preclinical studies in suitable infant animal surrogate models.

Anesthetics and brain toxicity

PURPOSE OF REVIEW

Recent experimental data from rodent studies have demonstrated accelerated neurodegeneration in rat pups exposed to commonly used anesthetic drugs. These provocative findings certainly question and undermine the safe use of anesthetic drugs, particularly in pediatric anesthesia, and have prompted many to investigate the neurotoxic effect of anesthetic drugs on the developing brain. This review will address the scientific evidence for the anesthetic-induced neurotoxicity and its applicability in humans.

RECENT FINDINGS

Several investigators have shown that prolonged administration of anesthetic drugs, including ketamine, isoflurane, nitrous oxide and midazolam, produced increased neurodegeneration in 7-day-old rat pups. The combination of the latter three drugs led to altered learning behavior in adulthood. Despite these unequivocal findings in rodents, similar changes cannot be reproduced in other species. Furthermore, withholding anesthesia during painful procedures in neonatal rats resulted in significant long-term aberrant responses to sensory stimulation and pain thresholds.

SUMMARY

Taken together, these studies question the applicability of these data to the anesthetic management of the neonate. Further investigations in this area are needed before withholding anesthetics in the anesthetic management of pediatric surgical patients.

Summary proceedings from the neonatal pain-control group

Recent advances in neurobiology and clinical medicine have established that the fetus and newborn may experience acute, established, and chronic pain. They respond to such noxious stimuli by a series of complex biochemical, physiologic, and behavioral alterations. Studies have concluded that controlling pain experience is beneficial with respect to short-term and perhaps long-term outcomes. Yet, pain-control measures are adopted infrequently because of unresolved scientific issues and lack of appreciation for the need for control of pain and its long-term sequelae during the critical phases of neurologic maturation in the preterm and term newborn. The neonatal pain-control group, as part of the Newborn Drug Development Initiative (NDDI) Workshop I, addressed these concerns. The specific issues addressed were (1) management of pain associated with invasive procedures, (2) provision of sedation and analgesia during mechanical ventilation, and (3) mitigation of pain and stress responses during and after surgery in the newborn infant. The cross-cutting themes addressed within each category included (1) clinical-trial designs, (2) drug prioritization, (3) ethical constraints, (4) gaps in our knowledge, and (5) future research needs. This article provides a summary of the discussions and deliberations. Full-length articles on procedural pain, sedation and analgesia for ventilated infants, perioperative pain, and study designs for neonatal pain research were published in Clinical Therapeutics (June 2005).

Anesthetic management of pial synangiosis and intracranial hemorrhage with a Fontan circulation

We report the case of a 11-year-old girl with Moyamoya syndrome, who had undergone staged-repair of tricuspid atresia to a Fontan circulation, scheduled to undergo bilateral pial synangiosis. Surgery for the first hemisphere was complicated by intracranial hemorrhage requiring an emergency craniotomy. The case highlights the importance of understanding Fontan physiology and its interrelationship with the cerebral circulation in the setting of cerebrovascular insufficiency and raised intracranial pressure.