Potentially toxic effects of anaesthetics on the developing central nervous system

Making the case for multidisciplinary pediatric aerodigestive programs

Multidisciplinary pediatric aerodigestive centers have been proposed to address the needs of children with complex multi-system problems affecting the respiratory and upper gastrointestinal tracts. The setup of a multidisciplinary service allows for the complex coordination needed between different subspecialties. This allows for rapid communication and family-centered decision making and agreement on further diagnostic and/or therapeutic next steps such as offering triple endoscopy when indicated. Triple endoscopy entails performing rigid upper airway assessment, flexible bronchoscopy and upper gastrointestinal endoscopy and has been linked to reduced time to diagnosis/treatment, reduced costs and anesthesia exposure. This review summarizes the available literature on the structure and benefits of multidisciplinary pediatric aerodigestive services.

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.

Dose-dependent effects of erythropoietin in propofol anesthetized neonatal rats

Exposure to Gamma-aminobutyric-acid (GABA)(A)-receptor agonists and N-Methyl-D-Aspartate (NMDA)-antagonists has been demonstrated to induce neurodegeneration in newborn rats. Exogenous erythropoietin (EPO) protects against NMDA antagonist-mediated neuronal death. In this study we evaluated whether EPO is also effective in limiting neurodegeneration of the GABA(A)-mimetic agent propofol in newborn rats. 6 day old rats were randomized to one of four groups and treated with intraperitoneal applications of 3 x 30 mg/kg propofol at 0, 90 and 180 min, propofol in combination with 5000 IU/kg rEPO, propofol in combination with 20,000 IU/kg rEPO or sham injections of PAD II solution as controls. After 24h, brains of the animals were histopathologically examined and a summation score of degenerated cells was calculated for every brain. Propofol increased neuronal degeneration scores from 16,090+/-4336 to 28,860+/-6569 (p<0.01). This effect was completely abolished by low-dose rEPO (14,270+/-4542, p<0.001 versus propofol only; p>0.05 versus controls). In contrast, high-dose rEPO was not protective (23 930+/-8896, p>0.05 versus propofol only). Propofol may cause neuronal death in newborn rat brains, which is prevented by low-dose rEPO but not high-dose rEPO.

The toxic effect of ketamine on SH-SY5Y neuroblastoma cell line and human neuron

Ketamine used as an injectable anesthetic in human and animal medicine is also a recreational drug used primarily by young adults often at all night dance parties in nightclubs. The percentage of ketamine users has grown very fast in the last 5 years worldwide. However, this leads to the serious question of the long-term adverse effects of ketamine on our nervous system, particularly the brain, because ketamine as an NMDA antagonist could cause neurons to commit apoptosis. Our study therefore aimed to find out the chronic effect of ketamine on neuron using prolonged incubation (48 h) of neuronal cells with ketamine in culture. Our results showed that differentiated neuronal cells were prone to the toxicity of ketamine but probably less susceptible than undifferentiated neuronal cells and fibroblasts. This suggested that the ketamine abuse would be harmful to many other organs as well as the brain. Our results also confirmed that the toxicity of ketamine is related to apoptosis via the Bax/Bcl-2 ratio pathway and caspase-3 in the differentiated neuronal cells. Therefore, long-term ketamine treated cell or animal models should be sought to study this multiorgan effects of ketamine.

Mice are prone to kidney pathology after prolonged ketamine addiction

ICR mice were injected with ketamine for 1, 3 and 6 months and the kidneys and urinary bladders were excised and processed for histology. Starting from 1 month, all addicted mice showed invasion of mononuclear white cells, either surrounding the glomerulus or the other tubules in the kidney. The aggregation of these cells extended all the way to the pelvis and ureter. As well, in the urinary bladder, the epithelium became thin and there was submucosal infiltration of mononuclear inflammatory cells. Silver staining revealed a loss of nerve fibers amongst the muscles of the urinary bladder of the treated. Immunohistochemistry on choline acetyltransferase which is a marker for cholinergic neurons also demonstrated a decrease of those cells. We hypothesized that prolonged ketamine addiction resulted in the animals prone to urinary infection.

High-dose propofol triggers short-term neuroprotection and long-term neurodegeneration in primary neuronal cultures from rat embryos

This study investigated the effects of propofol on primary neuronal cultures from rat embryos. Primary cortical neuronal cultures were prepared from Wistar rat embryos (E18). The viability of cells exposed to 0.01, 0.1 or 1 mg/ml propofol for up to 48 h was assessed using a methyltetrazolium assay. In order to evaluate the role of gamma-aminobutyric acid-A (GABA(A)) receptors, cells were also preincubated with the GABA(A)-receptor antagonists, gabazine and picrotoxin. Propofol at a concentration of 1 mg/ml significantly reduced cell viability after 12 h. In contrast, this concentration led to a significant increase in cell viability at 3 and 6 h. The GABA(A)-receptor antagonists did not influence the neurodegenerative effect of propofol but abolished its neuroprotective effect. DNA fragmentation as a marker of apoptosis was elevated after 24 h propofol treatment. These results confirm that high doses of propofol can cause GABA(A) receptor triggered neuroprotection and a subsequent time-dependent, but GABA(A) independent, neurodegeneration in primary cortical neurons.

Effects of sevoflurane on primary neuronal cultures of embryonic rats

BACKGROUND AND OBJECTIVE

Commonly used anaesthetics can cause neurodegeneration in the developing brain. Sevoflurane, a widely used substance in paediatric anaesthesia, has not been analysed thus far. This study was carried out to investigate the effects of sevoflurane on neuronal cell viability.

METHODS

Primary cortical neuronal cultures were prepared from Wistar rat embryos (E18), kept in 100 microl Gibco-Neurobasal-A medium and exposed to 4 and 8 Vol.% sevoflurane for up to 48 h. Cell viability was assessed using the methyltetrazolium assay and was related to untreated controls. To evaluate the role of gamma-aminobutyric acid type A receptors, untreated cells were preincubated with the receptor antagonists gabazine or picrotoxin and were subsequently exposed to 8 Vol.% sevoflurane and the receptor antagonist. Cell viability was assessed and compared with that of sevoflurane-treated controls.

RESULTS

Up to 6 (8 Vol.%) and 12 h (4 Vol.%) of exposure to sevoflurane, cell viability was equal when compared with untreated controls. Only longer exposure times led to significantly lowered cell viability. After 12 h of exposure, no significant differences in cell viability were found between these two series. Cell viability of cultures treated with sevoflurane and the receptor antagonists showed no significant differences when compared with sevoflurane-exposed controls.

CONCLUSION

These results suggest that sevoflurane does not cause neurodegeneration in primary cortical neurons of the rat following clinically relevant exposure times and concentrations.

GABAA receptors, anesthetics and anticonvulsants in brain development

GABA, acting via GABA(A) receptors, is well-accepted as the main inhibitory neurotransmitter of the mature brain, where it dampens neuronal excitability. The receptor's properties have been studied extensively, yielding important information about its structure, pharmacology, and regulation that are summarized in this review. Several GABAergic drugs have been commonly used as anesthetics, sedatives, and anticonvulsants for decades. However, findings that GABA has critical functions in brain development, in particular during the late embryonic and neonatal period, raise worthwhile questions regarding the side effects of GABAergic drugs that may lead to long-term cognitive deficits. Here, we will review some of these drugs in parallel with the control of CNS development that GABA exerts via activation of GABA(A) receptors. This review aims to provide a basic science and clinical perspective on the function of GABA and related pharmaceuticals acting at GABA(A) receptors.