Anesthetic-related neurotoxicity in the developing infant: of mice, rats, monkeys and, possibly, humans

Neonatal exposure to a neuroactive steroid alters low-frequency oscillations in the subiculum

Preclinical studies have established that neonatal exposure to contemporary sedative/hypnotic drugs causes neurotoxicity in the developing rodent and primate brains. Our group recently reported that novel neuroactive steroid (3β,5β,17β)-3-hydroxyandrostane-17-carbonitrile (3β-OH) induced effective hypnosis in both neonatal and adult rodents but did not cause significant neurotoxicity in vulnerable brain regions such as subiculum, an output region of hippocampal formation particularly sensitive to commonly used sedatives/hypnotics. Despite significant emphasis on patho-morphological changes, little is known about long-term effects on subicular neurophysiology after neonatal exposure to neuroactive steroids. Hence, we explored the lasting effects of neonatal exposure to 3β-OH on sleep macrostructure as well as subicular neuronal oscillations in vivo and synaptic plasticity ex vivo in adolescent rats. At postnatal day 7, we exposed rat pups to either 10 mg/kg of 3β-OH over a period of 12 h or to volume-matched cyclodextrin vehicle. At weaning age, a cohort of rats was implanted with a cortical electroencephalogram (EEG) and subicular depth electrodes. At postnatal day 30-33, we performed in vivo assessment of sleep macrostructure (divided into wake, non-rapid eye movement, and rapid eye movement sleep) and power spectra in cortex and subiculum. In a second cohort of 3β-OH exposed animals, we conducted ex vivo studies of long-term potentiation (LTP) in adolescent rats. Overall, we found that neonatal exposure to 3β-OH decreased subicular delta and sigma oscillations during non-rapid eye movement sleep without altering sleep macrostructure. Furthermore, we observed no significant changes in subicular synaptic plasticity. Interestingly, our previous study found that neonatal exposure to ketamine increased subicular gamma oscillations during non-rapid eye movement sleep and profoundly suppressed subicular LTP in adolescent rats. Together these results suggest that exposure to different sedative/hypnotic agents during a critical period of brain development may induce distinct functional changes in subiculum circuitry that may persist into adolescent age.

Neonatal Ketamine Alters High-Frequency Oscillations and Synaptic Plasticity in the Subiculum But Does not Affect Sleep Macrostructure in Adolescent Rats

Exposure to sedative/hypnotic and anesthetic drugs, such as ketamine, during the critical period of synaptogenesis, causes profound neurotoxicity in the developing rodent and primate brains and is associated with poor cognitive outcomes later in life. The subiculum is especially vulnerable to acute neurotoxicity after neonatal exposure to sedative/hypnotic and anesthetic drugs. The subiculum acts as a relay center between the hippocampal complex and various cortical and subcortical brain regions and is also an independent generator of gamma oscillations. Gamma oscillations are vital in neuronal synchronization and play a role in learning and memory during wake and sleep. However, there has been little research examining long-term changes in subicular neurophysiology after neonatal exposure to ketamine. Here we explore the lasting effects of neonatal ketamine exposure on sleep macrostructure as well as subicular neuronal oscillations and synaptic plasticity in rats. During the peak of rodent synaptogenesis at postnatal day 7, rat pups were exposed to either 40 mg/kg of ketamine over 12 h or to volume matched saline vehicle. At weaning age, a subset of rats were implanted with a cortical and subicular electroencephalogram electrode, and at postnatal day 31, we performed in vivo experiments that included sleep macrostructure (divided into the wake, non-rapid eye movement, and rapid eye movement sleep) and electroencephalogram power spectra in cortex and subiculum. In a second subset of ketamine exposed animals, we conducted ex vivo studies of long-term potentiation (LTP) experiments in adolescent rats. Overall, we found that neonatal exposure to ketamine increased subicular gamma oscillations during non-rapid eye movement sleep but it did not alter sleep macrostructure. Also, we observed a significant decrease in subicular LTP. Gamma oscillations during non-rapid eye movement sleep are implicated in memory formation and consolidation, while LTP serves as a surrogate for learning and memory. Together these results suggest that lasting functional changes in subiculum circuitry may underlie neurocognitive impairments associated with neonatal exposure to anesthetic agents.

Spinal anesthesia in children: most pediatric urologists are not on board

OBJECTIVE

In 2016, the Food and Drug Administration issued a warning on general anesthetic medications used for lengthy procedures (>3 h) in children younger than 3 years. Spinal anesthesia can be a safe alternative to general anesthesia for many pediatric urology procedures. It can shorten total operating room (OR) time, provide excellent pain control, and allow parents to reunite with their child immediately after surgery. However, use of spinal anesthesia can also directly affect the operating surgeon (awake patient, time constraints of spinal, and prolonged preoperative time). Members of the Societies for Pediatric Urology (SPU) and European Society of Pediatric Urology (ESPU) were surveyed to get their opinions on the use of spinal anesthesia for routine pediatric urology procedures. It was hypothesized that half of pediatric urologists would favor spinal anesthesia and that SPU members would be more likely to favor spinal anesthesia than their European colleagues.

MATERIALS AND METHODS

A short survey with five clinical scenarios was created. Scenarios assessed physicians' recommendations regarding timing and the type of anesthesia (general or spinal) for common pediatric urology procedures: undescended testicle, inguinal hernia, hypospadias, phimosis, and phimosis with penoscrotal webbing. Surveys were emailed to members of the SPU and ESPU. Responses and demographic information were collected and analyzed.

RESULTS

The survey was completed by 113 SPU members (46% response rate for members who opened the invitation) and 109 ESPU members. For all clinical scenarios, < 20% of pediatric urologists from the SPU and <25% from the ESPU favor doing any procedure with spinal anesthesia. The majority of respondents practice in children's hospitals with pediatric anesthesiologists, but roughly half of the responders (54% SPU and 43% ESPU) do not think their anesthesia colleagues would be comfortable performing spinal anesthesia. Furthermore, only 51% of SPU and 36% of ESPU members discuss the possible neurodevelopmental side-effects of anesthesia with parents; similarly, less than half of all respondents think their anesthesia colleagues address these potential side-effects when obtaining consent. The only significant difference between SPU and ESPU responses was that ESPU members tended to delay penile surgery more than SPU respondents.

CONCLUSION

Whether general anesthesia has any effect on the developing brain of children undergoing routine pediatric urology procedures is unclear. Yet, few pediatric urologists, independent of their region of practice, prefer spinal to general anesthesia. Collaboration in the OR is the key to success, and it is important that pediatric urologists and pediatric anesthesiologists work together to balance the benefits and risks of general and spinal anesthesia.

Age-dependent outcomes in asymptomatic umbilical hernia repair

PURPOSE

Umbilical hernias are common in young children. Many resolve spontaneously by age four with very low risk of symptoms or incarceration. Complications associated with surgical repair of asymptomatic umbilical hernias have not been well elucidated. We analyzed data from one hospital to test the hypothesis that repair at younger ages is associated with increased complication rates.

METHODS

A retrospective chart review of all umbilical hernia repairs performed during 2007-2015 was conducted at a tertiary care children's hospital. Patients undergoing repairs as a single procedure for asymptomatic hernia were evaluated for post-operative complications by age, demographics, and co-morbidities.

RESULTS

Of 308 umbilical hernia repairs performed, 204 were isolated and asymptomatic. Postoperative complications were more frequent in children < 4 years (12.3%) compared to > 4 years (3.1%, p = 0.034). All respiratory complications (N = 4) and readmissions (N = 1) were in children < 4 years.

CONCLUSIONS

Age of umbilical hernia repair in children varied widely even within a single institution, demonstrating that timing of repair may be a surgeon-dependent decision. Patients < 4 years were more likely to experience post-operative complications. Umbilical hernias often resolve over time and can safely be monitored with watchful waiting. Formal guidelines are needed to support delayed repair and prevent unnecessary, potentially harmful operations.

Practice Variation in Umbilical Hernia Repair Demonstrates a Need for Best Practice Guidelines

OBJECTIVE

To evaluate and better understand variations in practice patterns, we analyzed ambulatory surgery claims data from 3 demographically diverse states to assess the relationship between age at umbilical hernia repair and patient, hospital, and geographic characteristics.

STUDY DESIGN

We performed a cross-sectional descriptive study of uncomplicated hernia repairs performed as a single procedure in 2012-2014, using the State Ambulatory Surgery and Services Database for Wisconsin, New York, and Florida. Age and demographic characteristics of umbilical hernia repair patients are described.

RESULTS

The State Ambulatory Surgery and Services Database analysis included 6551 patients. Across 3 states, 8.2% of hernia repairs were performed in children <2 years, 18.7% in children age 2-3 years, and 73.0% in children age ≥4 years, but there was significant variability (P < .001) in practice patterns by state. In regression analysis, race, Medicaid insurance and rural residence were predictive of early repair, with African American patients less likely to have a repair before age 2 (OR 0.62, P = .046) and rural children (OR 1.53, P = .009) and Medicaid patients (OR 2.01, P < .001) more likely to do so. State of residence predicted early repair even when holding these variables constant.

CONCLUSIONS

The age of pediatric umbilical hernia repair varies widely. As hernias may resolve over time and can be safely monitored with watchful waiting, formal guidelines are needed to support delayed repair and prevent unnecessary operations.

Fractured pediatric central venous catheters - Repair or replace?

INTRODUCTION

Central venous catheter (CVC) fracture is a common complication. The aim of this study is to examine risk factors resulting in CVC fracture and compare outcomes of children undergoing CVC repair versus replacement.

METHODS

A retrospective chart review was conducted from 2000 to 2016 for children with tunneled CVCs. Children with CVC fractures were compared to those without to identify risk factors resulting in fracture. Children with fractured CVCs were divided into repair or replacement treatment groups and outcomes compared. A logistic regression model determined independent predictors of CVC-associated bloodstream infections (CLABSI) after fracture.

RESULTS

In the 236 children with CVCs, the fracture rate was 29.2%. Fractured CVCs were more common with double lumen CVC (p = 0.040) and children whose indication was total parenteral nutrition (p = 0.003). Given children often underwent multiple repairs or replacements. 98 CVC repairs and 41 replacements were analyzed. CVC replacements had longer durability than repair (181.98 vs. 98.9 days, p = 0.038). There were no differences in CLABSI incidence for repair vs. replacement (OR 0.5 CI 0.05-4.97) after controlling for other factors.

CONCLUSIONS

CVC fracture is a frequent complication in children with tunneled CVCs. CVC repair has no increased incidence of CLABSI but eliminates the intraoperative and anesthetic risks of CVC replacement.

TYPE OF STUDY

Retrospective cohort study.

LEVEL OF EVIDENCE

Level III.

Suberoylanilide hydroxamic acid (SAHA) alleviates the learning and memory impairment in rat offspring caused by maternal sevoflurane exposure during late gestation

Recent studies have shown that sevoflurane can cause long-term neurotoxicity and learning and memory impairment in developing and progressively neurodegenerative brains. Sevoflurane is a widely used volatile anesthetic in clinical practice. Late gestation is a rapidly developing period in the fetal brain, but whether sevoflurane anesthesia during late gestation affects learning and memory of offspring is not fully elucidated. Histone deacetylase 2 (HDAC2) plays an important regulatory role in learning and memory. This study examined the effect of maternal sevoflurane exposure on learning and memory in offspring and the underlying role of HDAC2. The Morris water maze (MWM) test was used to evaluate learning and memory function. Q-PCR and immunofluorescence staining were used to measure the expression levels of genes related to learning and memory. The results showed that sevoflurane anesthesia during late gestation impaired learning and memory in offspring rats (e.g., showing increase of the escape latency and decrease of the platform-crossing times and target quadrant traveling time in behavior tests) and upregulated the expression of HDAC2, while downregulating the expression of the cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) and the N-methyl-D-aspartate receptor 2 subunit B (NR2B) mRNA and protein in the hippocampus of offspring in a time-dependent manner. HDAC2 inhibitor suberoylanilide hydroxamic acid (SAHA) treatment alleviated all of these changes in offspring rats. Therefore, the present study indicates that sevoflurane exposure during late gestation impairs offspring rat's learning and memory via upregulation of the expression of HDAC2 and downregulation of the expression of CREB and NR2B. SAHA can alleviate these impairments.

KIF17 mediates the learning and memory impairment in offspring induced by maternal exposure to propofol during middle pregnancy

Preclinical studies suggest that propofol may cause neuronal injury to the developing brain. A previous study demonstrated that, in a rat model, maternal exposure to propofol during early or late pregnancy caused learning and memory impairment in the offspring. However, whether propofol exposure during middle pregnancy can cause long‑term behavioral deficits in the offspring remains to be elucidated. N‑methyl‑D‑aspartate receptor 2B subunit (NR2B) serves a critical role in memory modulation. To exert its function, NR2B must be transported to the neuronal membrane by kinesin family member 17 (KIF17). The aim of the present study was to investigate the role of KIF17 in learning and memory impairment in rat offspring caused by propofol exposure during middle pregnancy. Pregnant rats were exposed to propofol on gestational day 14 (G14) for 4 and 8 h, with control pregnant rats receiving an equal volume of normal saline. The learning and memory of the offspring was assessed using Morris water maze tests from postnatal day 30 (P30) to P36. The levels of KIF17 protein, total NR2B (T‑NR2B) and membrane NR2B (M‑NR2B) in the hippocampus were detected using western blotting. The results demonstrated that propofol exposure caused learning and memory deficits and decreased KIF17 and M‑NR2B protein levels in the hippocampus; however, no but changes in the expression of T‑NR2B were observed. These results indicate that maternal propofol exposure during middle pregnancy impairs learning and memory in offspring rats by suppressing the expression of KIF17 and inhibiting the translocation of NR2B to the neuronal membrane.

Quantifying Anesthesia Exposure in Growing Rod Treatment for Early Onset Scoliosis

BACKGROUND

Growing rod (GR) treatment for early-onset scoliosis requires repeated anesthesia exposure (AE). At a minimum, GR treatment requires AE for diagnostic imaging, index GR surgery, periodic lengthenings, and final fusion. Adjunct procedures and complication-related procedures also increase AE. To our knowledge, this is the first study to quantify AE in GR treatment and to establish preoperative expectations.

METHODS

A single-center retrospective review of 16 patients who completed GR treatment and underwent final fusion. Duration of all AE related to GR treatment for "standard" care procedures (ie, advanced imaging, index surgery, lengthenings, final fusion) and "associated" care procedures (ie, revisions, adjunctive surgical procedures, wound-related complications) were reviewed. Etiologies were classified per the classification of early-onset scoliosis. Mean total anesthesia time (TAT) was tallied and analyzed for standard care and associated care procedures.

RESULTS

There were 5 syndromic, 8 neuromuscular, and 3 idiopathic patients. The mean age at the first AE event related to GR treatment was 7.4 years (range, 3.8 to 11 y). Mean age at the index GR surgery and final fusion was 8.1 years (range, 3.9 to 14.4 y) and 12.8 years (range, 9.7 to 19 y), respectively. The percentage of TAT for each procedural category was 7% for advanced imaging, 14% for index GR, 14% for lengthenings, 21% for final fusion, 27% for revisions, 9% for adjunct surgery, and 9% for wound complications. Standard care procedures accounted for 55% of TAT, whereas associated care procedures accounted for 45%.

CONCLUSIONS

This study quantified expected duration of AE in GR treatment. Revisions and final fusion contributed most to TAT. Given the recent controversy of repeated AE in young children, efficiency measures should be implemented to reduce AE and avoid duplication without compromising the goals of surgical treatment. Associated care procedures accounted for 45% of the total AE.

LEVEL OF EVIDENCE

Level IV.

Spinal anesthesia for pediatric urological surgery: Reducing the theoretic neurotoxic effects of general anesthesia

BACKGROUND

Spinal anesthesia (SA) is an effective technique that has been used in children for years. With growing concern with regard to the risks of general anesthesia (GA), we developed a SA program to provide an alternative option. We present our initial experience with this program.

OBJECTIVE

To implement a SA program at a large tertiary care pediatric center and assess the safety and efficacy of the technique as an alternative to GA for urologic surgery.

STUDY DESIGN/METHODS

We prospectively collected data on all children undergoing SA at our institution. We recorded demographics, procedure, time required for placement of the SA, length of surgery, success of lumbar puncture, success of attaining adequate surgical anesthesia, need for supplemental systemic sedation, conversion to GA, and perioperative complications.

RESULTS

SA was attempted in 105 consecutive children (104 boys, 1 girl) with a mean age of 7.4 ± 4.3 months (range 19 days-24 months) and mean weight of 8.3 ± 1.7 kg (range 3.5-13.7). Placement of the SA was successful in 93/105 children (89%). Inability to achieve lumbar puncture (cerebrospinal fluid was not obtained) meant that SA was abandoned in seven (7%) patients and GA was administered. In five patients in whom SA was successful and surgery was begun, 5/93 (5%) required conversion to GA: two because of evisceration of intestine through large hernia defects related to coughing and abdominal irritation, two because of lack of motor blockade despite an adequate sensory block, and one because of an inability to place an intravenous catheter in the lower extremities (required per SA protocol). If necessary, an intravenous catheter can be placed in the upper extremity, but this must be weighed against the fact that the block has already been placed and is of limited duration. Overall, SA was successful (SA was placed and surgery was completed without conversion to GA) in 88/105 children (84%). No additional sedation and no systemic anesthetic agents were required in 75/88 children (85%). The average time required to place the SA was 3.8 ± 2.7 min (range 1-12). The average time for the surgical procedure was 38.3 ± 23.1 min (range 10-122). No patient required conversion to GA because of recession of block. There were no surgical complications.

DISCUSSION/CONCLUSIONS

SA is a safe and efficacious technique for routine pediatric urological procedures. SA should be considered for cases such as neonatal torsion or patients with significant cardiac or pulmonary comorbidities when the risks of GA are often weighed against the risks of non-intervention.

Spinal anesthesia after intraoperative cardiac arrest during general anesthesia in an infant

Although generally safe and effective, severe perioperative complications, including cardiac arrest, may occur during general anesthesia in infants. With the emergence of evidence that specific anesthetic agents may affect future neurocognitive outcomes, there has been an increased focus on alternatives to general anesthesia, including spinal anesthesia. We present a case of cardiac arrest during general anesthesia in an infant who required urologic surgery. During the subsequent anesthetic care, spinal anesthesia was offered as an alternative to general anesthesia. The risks of severe perioperative complications during general anesthesia are reviewed, etiologic factors for such events are presented, and the use of spinal anesthesia as an alternative to general anesthesia is discussed.

Evaluation of the effects of ketamine on spinal anesthesia with levobupivacaine or ropivacaine

Spinal anesthesia or regional anesthesia is a potent anesthetic procedure. Additional modalities have been sought to increase the duration of block in spinal anesthesia. Ketamine is an N-methyl-D-aspartate (NMDA) receptor blocker that has an anesthetic effect when injected intrathecally and has a synergic effect with bupivacaine. Ketamine also has potent analgesic properties. The present study investigated the effect of intrathecally administered ketamine on spinal anesthesia with levobupivacaine or ropivacaine. Sprague-Dawley rats at post-natal day 21 were exposed to spinal anesthesia with 0.5% levobupivacaine or 0.5% ropivacaine. Separate groups of rats were treated with intrathecal ketamine at a 5 or 10 mg/kg bodyweight dose along with ropivacaine or levobupivacaine. The thermal and mechanical withdrawal latencies of the animals were determined using hot plate and von Frey filaments, respectively. A rotarod apparatus was employed to assess the capacity of the rats to rotate the spindle at 24 h following anesthesia. The gait of the rat pups was also assessed. Intrathecal administration of ketamine resulted in dense blocks and extended the duration of spinal blocks as evidenced by thermal latencies and responses to von Frey filaments. The latency to fall was shorter in rats exposed to ketamine along with ropivacaine or levobupivacaine spinal anesthesia. The gait parameters were also more disturbed upon ketamine administration. In conclusion, ketamine administration with ropivacaine or levobupivacaine increased the intensity and duration of spinal blockade, thereby increasing the anesthetic effects.

Propofol exposure during late stages of pregnancy impairs learning and memory in rat offspring via the BDNF-TrkB signalling pathway

The brain‐derived neurotrophic factor (BDNF)‐tyrosine kinase B (TrkB) (BDNF‐TrkB) signalling pathway plays a crucial role in regulating learning and memory. Synaptophysin provides the structural basis for synaptic plasticity and depends on BDNF processing and subsequent TrkB signalling. Our previous studies demonstrated that maternal exposure to propofol during late stages of pregnancy impaired learning and memory in rat offspring. The purpose of this study is to investigate whether the BDNF‐TrkB signalling pathway is involved in propofol‐induced learning and memory impairments. Propofol was intravenously infused into pregnant rats for 4 hrs on gestational day 18 (E18). Thirty days after birth, learning and memory of offspring was assessed by the Morris water maze (MWM) test. After the MWM test, BDNF and TrkB transcript and protein levels were measured in rat offspring hippocampus tissues using real‐time PCR (RT‐PCR) and immunohistochemistry (IHC), respectively. The levels of phosphorylated‐TrkB (phospho‐TrkB) and synaptophysin were measured by western blot. It was discovered that maternal exposure to propofol on day E18 impaired spatial learning and memory of rat offspring, decreased mRNA and protein levels of BDNF and TrkB, and decreased the levels of both phospho‐TrkB and synaptophysin in the hippocampus. Furthermore, the TrkB agonist 7,8‐dihydroxyflavone (7,8‐DHF) reversed all of the observed changes. Treatment with 7,8‐DHF had no significant effects on the offspring that were not exposed to propofol. The results herein indicate that maternal exposure to propofol during the late stages of pregnancy impairs spatial learning and memory of offspring by disturbing the BDNF‐TrkB signalling pathway. The TrkB agonist 7,8‐DHF might be a potential therapy for learning and memory impairments induced by maternal propofol exposure.

The role of TNF-α in regulating ketamine-induced hippocampal neurotoxicity

INTRODUCTION

Ketamine is commonly used in pediatric anesthesia but recent studies have shown that it could induce neurotoxicity in the developing brain. The inflammatory cytokine, tumor necrosis factor α (TNF-α) is involved in the pathogenesis of various types of neurodegenerations. In the present study, we examined whether TNF-α may regulate ketamine-induced neurotoxicity in the hippocampus of neonatal mouse.

MATERIAL AND METHODS

The in vitro organotypic culture of hippocampal slices was used to investigate the gain-of-function and loss-of-function effect of TNF-α modulation on ketamine-induced hippocampal neurotoxicity. Also, western blotting analysis was used to examine the relative pathways associated with TNF-α modulation. In the in vivo Morris water maze test, TNF-α was genetically silenced to see if memory function was improved after anesthesia-induced memory impairment.

RESULTS

In in vitro experiments, adding TNF-α enhanced (112.99 ±5.4%, p = 0.015), whereas knocking down TNF-α ameliorated (46.8 ±11.6%, p = 0.003) ketamine-induced apoptosis in hippocampal CA1 neurons in the organotypic culture. Western blotting showed that addition of TNF-α reduced (67.1 ±3.7%, p = 0.022), whereas downregulation of TNF-α increased (126.87 ±8.5%, p = 0.004) the phosphorylation of PKC-ERK pathway in ketamine-treated hippocampus. In in vivo experiments, genetically silencing TNF-α markedly improved the ketamine-induced memory impairment through Morris water maze test.

CONCLUSIONS

Our results clearly demonstrated a protective mechanism of down-regulating TNF in ketamine-induced hippocampal neurotoxicity. This study may present a new target for pharmacological intervention to prevent anesthesia-related neurodegeneration in brain.

Role of miR-34c in ketamine-induced neurotoxicity in neonatal mice hippocampus

Ketamine is a commonly used pediatric anesthetic, but it might affect development, or even induce neurotoxicity in the neonatal brain. We have used an in vivo neonatal mouse model to induce ketamine-related neurotoxicity in the hippocampus, and found that miR-34c, a microRNA associated with pathogenesis of Alzheimer's disease, was significantly upregulated during ketamine-induced hippocampal neurodegeneration. Functional assay of silencing miR-34c demonstrated that downregulation of miR-34c activated PKC-ERK pathway, upregulated anti-apoptotic protein BCL2, and ameliorated ketamine-induced apoptosis in the hippocampus. Cognitive examination with the Morris water maze test showed that ketamine-induced memory impairment was significantly improved by miR-34c downregulation. Thus, miR-34c is important in regulating ketamine-induced neurotoxicity in hippocampus.

The role of miR-124 in modulating hippocampal neurotoxicity induced by ketamine anesthesia

PURPOSE

Ketamine is widely used in pediatric anesthesia. Recent studies have demonstrated that excessive application of ketamine leads to cortical neurodegeneration in neonatal brains. The present study aims to characterize the functional role of neuronal microRNA, miR-124, in regulating ketamine-induced neurotoxicity in mouse hippocampus.

METHODS

Real-time quantitative PCR (RT-PCR) was used to examine the effect of high-dosage ketamine on the expression of miR-124 in murine hippocampus in vitro. Downregulation of hippocampal miR-124 was achieved by lentivirual transfection, and its effects on protecting ketamine-induced hippocampal neurodegeneration were examined both in vitro and in vivo.

RESULTS

Hippocampal miR-124 was upregulated by ketamine treatment. Knocking down miR-124 in vitro reduced ketamine-induced apoptosis in hippocampal CA1 neurons, upregulated AMPA receptors phosphorylation and activated the protein kinase C/extracellular signal-regulated kinases (PKC/ERK) pathway. In the in vivo Morris water maze test, following ketamine-induced hippocampal neurodegeneration, mice subjected to hippocampal miR-124 inhibition showed improved memory performance.

CONCLUSIONS

Our study demonstrated that miR-124 played an important role in regulating ketamine-induced hippocampal neurodegeneration. Inhibiting miR-124 may provide a molecular target to improve memory performance in both human and animals suffering from overanesthetizing-related neurotoxicity.

Feasibility of laparoscopic pyloromyotomy under spinal anesthesia

BACKGROUND

Most agents used for GA are considered to be neurotoxins and affect developing brains in experimental models, leading to a push for spinal anesthesia (SA). There are no reports of laparoscopic pyloromyotomy (LP) performed under SA. We present our experience with LP and SA and discuss feasibility.

METHODS

A retrospective analysis was performed on a consecutive series of patients who underwent an LP. An 'intent to treat' analysis was utilized, and GA was compared to SA. Data regarding patient characteristics, operative intervention, complications, and postoperative course were collected.

RESULTS

Twelve cases had attempted SA for the LP, 9 were successful. During the same time, 12 cases underwent LP under GA. We found no difference for length of procedure, time to the first feed, or the postoperative LOS. The time to leave the OR after conclusion of the procedure was significantly shorter for the SA group (14min vs. 28min, p<0.001). There were no complications from the SA, however three cases had to be converted to GA.

CONCLUSIONS

It is feasible and safe to perform laparoscopic pyloromyotomy under spinal anesthesia. Given the increasing concern over the use of GA in infants, consideration may be given to use of SA for LP.

Neonatal Anesthesia Neurotoxicity: A Review for Cleft and Craniofacial Surgeons

There is growing evidence that the commonly used anesthetic agents cause some degree of damage to the early developing brain. The animal evidence for anesthetic neurotoxicity is compelling. Numerous confounders in human research prevent researchers from drawing definitive conclusions about the degree of risk. For every surgery, it should be assessed whether the benefits of an early surgical procedure justify a potential but unquantifiable risk of neurotoxicity of anesthetic agents. The timing and number of surgeries in our treatment protocols may need to be reevaluated to account for these potential risks.

Combined use of neuraxial and general anesthesia during major abdominal procedures in neonates and infants

With the advent of ultrasound and improvements in equipment, the applications of regional anesthesia in the pediatric population have continued to expand. Although frequently used for postoperative analgesia or as a means of avoiding general anesthesia in patients with comorbid conditions, the adjunctive use of regional anesthesia during general anesthesia may effectively decrease the intraoperative requirements for intravenous and volatile agents, thereby providing a more rapid awakening and earlier tracheal extubation. More recently, the limitation of the requirements for volatile and other anesthetic agents may be desirable, given concerns regarding the potential impact of these agents on neurocognitive outcome in neonates and infants. Several authors have demonstrated the potential utility of combining a neuraxial technique (spinal or epidural anesthesia) with general anesthesia in neonates and infants undergoing intraabdominal procedures. We review the literature regarding the combined use of neuraxial and general anesthesia in neonates and infants during major abdominal surgery, discuss its potential applications in this population, and review the techniques of such practice.

Neurotoxicity of sedative and analgesia drugs in young infants with congenital heart disease: 4-year follow-up

OBJECTIVES/AIM

To determine whether sedation/analgesia drugs used before, during, and after infant cardiac surgery are associated with neurocognitive and functional outcomes.

BACKGROUND

Some animal models suggest neurotoxic effects of anesthetic drugs on the developing brain; however, potential human effects are unknown. Whether these results can be extrapolated to humans is unknown.

METHODS/MATERIALS

Prospective follow-up project of all infants ≤6 weeks old having surgery for congenital heart disease between 04/03 and 12/06. Demographic, perioperative, and sedation/analgesia variables were collected. Outcomes at kindergarten age were Wechsler Preschool and Primary Scale of Intelligence-III, Beery-Buktenica Developmental Test of Visual Motor Integration (VMI-V), and General Adaptive Composite (GAC) of the Adaptive Behavior Assessment System-II. Multivariable linear regression was used to identify predictor variables.

RESULTS

From 135 infants who underwent heart surgery, 19 died, 17 were excluded, 8 were lost to follow-up, leaving 91 children for analysis. Multiple linear regression found days on chloral hydrate [3.5 (3.7) days] was associated with lower performance intelligence quotient (PIQ) (Effect size -1.03; 95% CI -1.96, -0.10; P = 0.03), and cumulative dose [54.2 (60.3) mg·kg(-1) ] of benzodiazepines was associated with lower VMI scores (Effect size -0.07; 95% CI -0.12, -0.01; P = 0.026). No other associations were found between sedation/analgesia variables and full-scale IQ, PIQ, Verbal IQ, VMI, or GAC.

CONCLUSION

Assessment of this cohort at kindergarten age found a small statistically significant association between days on chloral hydrate and PIQ, and benzodiazepine cumulative dose and lower VMI. No other association between sedation/analgesia drugs and outcomes was found.

Evaluation of spinal toxicity and long-term spinal reflex function after intrathecal levobupivaciane in the neonatal rat

BACKGROUND

Neuraxial anesthesia is utilized in children of all ages. Local anesthetics produce dose-dependent toxicity in certain adult models, but the developing spinal cord may also be susceptible to drug-induced apoptosis. In postnatal rodents, we examined the effects of intrathecal levobupivacaine on neuropathology and long-term sensorimotor outcomes.

METHODS

Postnatal day 3 (P3) or P7 rat pups received intrathecal levobupivacaine 2.5 mg/kg (0.5%) or saline. Mechanical withdrawal thresholds and motor block were assessed. Spinal cord tissue analysis included apoptosis counts (activated caspase-3, Fluoro-Jade C) at 24 h, glial reactivity at 7 days, and histopathology in cord and cauda equina at 24 h and 7 days. Long-term spinal function in young adults (P35) was assessed by hind limb withdrawal thresholds, electromyography responses to suprathreshold stimuli, and gait analysis.

RESULTS

Intrathecal levobupivacaine produced spinal anesthesia at P3 and P7. No increase in apoptosis or histopathological change was seen in the cord or cauda equina. In the P3 saline group, activated caspase-3 (mean±SEM per lumbar cord section 6.1±0.3) and Fluoro-Jade C (12.1±1.2) counts were higher than at P7, but were not altered by levobupivacaine (P=0.62 and P=0.11, two-tailed Mann-Whitney test). At P35, mechanical withdrawal thresholds, thermal withdrawal latency, and electromyographic reflex responses did not differ across P3 or P7 levobupivacaine or saline groups (one way ANOVA with Bonferroni comparisons). Intrathecal bupivacaine at P3 did not alter gait.

CONCLUSION

Single dose intrathecal levobupivacaine 0.5% did not increase apoptosis or produce spinal toxicity in neonatal rat pups. This study provides preclinical safety data relevant to neonatal use of neuraxial local anesthesia.

Modeling anesthetic developmental neurotoxicity using human stem cells

Mounting preclinical evidence in rodents and nonhuman primates has demonstrated that prolonged exposure of developing animals to general anesthetics can induce widespread neuronal cell death followed by long-term memory and learning disabilities. In vitro experimental evidence from cultured neonatal animal neurons confirmed the in vivo findings. However, there is no direct clinical evidence of the detrimental effects of anesthetics in human fetuses, infants, or children. Development of an in vitro neurogenesis system using human stem cells has opened up avenues of research for advancing our understanding of human brain development and the issues relevant to anesthetic-induced developmental toxicity in human neuronal lineages. Recent studies from our group, as well as other groups, showed that isoflurane influences human neural stem cell proliferation and neurogenesis, whereas ketamine induces neuroapoptosis. Application of this high throughput in vitro stem cell neurogenesis approach is a major stride toward ensuring the safety of anesthetic agents in young children. This in vitro human model allows us to (1) screen the toxic effects of various anesthetics under controlled conditions during intense neuronal growth, (2) find the trigger for the anesthetic-induced catastrophic chain of toxic events, and (3) develop prevention strategies to avoid this toxic effect. In this article, we reviewed the current findings in anesthetic-induced neurotoxicity studies, specifically focusing on the in vitro human stem cell model.

Conservative treatment for complex neonatal ovarian cysts: a long-term follow-up analysis

OBJECTIVE

We aimed to investigate safety and effectiveness of a conservative approach for complex neonatal ovarian cysts and its long term impact on fertility.

STUDY DESIGN

Neonates with congenital complex ovarian cysts were conservatively managed and followed from the perinatal period to adolescence. Statistical analysis included Student's t-test, Mann-Whitney U-test, the Kaplan-Meier method, and the receiver operating characteristic curve.

RESULTS

The post-natal progressive dimensional reduction of diagnosed ovarian cyst was statistically significant. The Kaplan-Meier survival curves revealed the probability of persistence of the cyst was up to 5% at the age of 25 months. Long term follow-up revealed both ovaries visible at US in 60% of adolescent patients.

CONCLUSION

Conservative management of asymptomatic complex neonatal ovarian cysts can be safely undertaken. As far as the chances of the ovarian tissue to survive conservative treatment are concerned, the results are not encouraging.

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.

Acupuncture therapy for infants: a preliminary report on reasons for consultation, feasibility, and tolerability

OBJECTIVES/AIMS

  The aim of this retrospective review was to determine the feasibility, safety, and potential therapeutic effects of acupuncture in an inpatient infant population and to obtain data that would support the design of a randomized, controlled trial of acupuncture in infants.

BACKGROUND

  Hospitalized infants are often exposed to sedative and analgesic medications to facilitate intensive and invasive medical care. With increasing concern about the potential neurotoxic effects of common analgesic and sedative medications, minimizing an infant's exposure to such agents is desirable. Acupuncture can be therapeutic in adults and children, but data in infants are lacking.

METHODS/MATERIALS

  We performed a retrospective chart review of infants who received acupuncture during hospitalizations between 2008 and 2010. Demographic data, diagnoses, reason for acupuncture consult, ventilator settings, sedative/analgesic medication regimens, details of acupuncture therapy, and adverse effects were among data collected.

RESULTS

  Ten infants were identified in this review, seven of whom had agitation issues, two of whom had feeding difficulties, and one had both symptoms. Six of the eight infants with agitation had a decrease in the use of sedative and analgesic medications over the acupuncture therapy period, and four of five initially requiring mechanical ventilation were successfully weaned. One of the three infants with oral aversion transitioned rapidly to oral intake. Acupuncture therapy was well tolerated, and there were no complications observed.

CONCLUSIONS

  In this small group of hospitalized infants, acupuncture was found to be safe, well tolerated, and therapeutic. More studies are warranted to define the role of acupuncture in this population.

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.

Intrathecal clonidine in the neonatal rat: dose-dependent analgesia and evaluation of spinal apoptosis and toxicity

BACKGROUND

Neuraxial clonidine is used for perioperative analgesia in children of all ages. Preclinical studies in the postnatal rat allow comparison of the relative toxicity and safety of spinal analgesics throughout postnatal development.

METHODS

Rat pups aged 3, 7, or 21 postnatal (P) days were briefly anesthetized for intrathecal injections of saline or clonidine. At each age, the maximum tolerated, antinociceptive (increased hindlimb mechanical withdrawal threshold) and antihyperalgesic (hindpaw carrageenan inflammation) doses were determined. Lumbar spinal cord sections were assessed for apoptosis and cell death (histology, activated caspase-3 immunohistochemistry, Fluoro-Jade C staining), histopathology (hematoxylin and eosin staining), and increased glial reactivity (microglial and astrocytic markers). P3 intrathecal ketamine sections served as positive controls. In additional groups, thermal latency and mechanical withdrawal threshold were measured at P35.

RESULTS

Intrathecal clonidine produces age- and dose-dependent analgesia in rat pups. Maximal doses of clonidine did not alter the degree or distribution of apoptosis or increase glial reactivity in the neonatal spinal cord. No spinal histopathology was seen 1 or 7 days after injection at any age. Intrathecal clonidine did not produce persistent changes in reflex sensitivity to mechanical or thermal stimuli at P35.

CONCLUSIONS

Intrathecal clonidine in the postnatal rat did not produce signs of spinal cord toxicity, even at doses much larger than required for analgesia. The therapeutic ratio (maximum tolerated dose/antihyperalgesic dose) was >300 at P3, >30 at P7, and >10 at P21. These data provide additional information to inform the clinical choice of spinal analgesic drug in early life.

Erythropoietin attenuates isoflurane-induced neurodegeneration and learning deficits in the developing mouse brain

OBJECTIVES

To examine whether recombinant erythropoietin (rEPO) attenuates neurodegeneration and the learning disability induced by isoflurane with the postnatal day 7 (P7) mice.

BACKGROUND

Some of general anesthetic agents induce neurodegeneration in developing brain. Several drugs, but not rEPO, were reported as candidates for the prevention of or treatment for neurodegeneration.

METHOD AND MATERIALS

We divided P7 mice into three groups at random. One group (IE group) was exposed to 6-h isoflurane (1.0%) after 50,000 IU·kg(-1) rEPO administered subcutaneously. The second group (I) was exposed to isoflurane in the same manner as IE group except saline instead of rEPO. The third group (E) was exposed to air after rEPO administered. The mice were assigned to the radial arm maze on four consecutive days from P56 (day 1) to P59 (day 4). We divided the number of errors each day by that of day 1 to establish each-day performance ratio. After the test, neurodegenerative change in the hilus of dentate gyrus was assessed using Nissl staining.

RESULTS

In radial maze test, the performance ratios of day 3 (mean ± sd) were 0.3 ± 0.2 (P < 0.05, vs I group), 0.8 ± 0.5, and 0.6 ± 0.2 in IE, I, and E groups, respectively, while those of day 4 were 0.3 ± 0.1 (P < 0.05), 0.8 ± 0.5, and 0.3 ± 0.2 (P < 0.05), respectively. The histopathological study revealed that in IE group the degenerative neuronal change was attenuated compared with I group.

CONCLUSIONS

These results suggested that rEPO attenuated isoflurane-induced neurodegeneration.

Neurodevelopmental outcome following exposure to sedative and analgesic drugs for complex cardiac surgery in infancy

OBJECTIVES/AIM

To determine whether sedation/analgesia drugs used before, during, and after infant cardiac surgery are associated with neurodevelopmental outcome.

BACKGROUND

Animal models suggest detrimental effects of anesthetic drugs on the developing brain. Whether these results can be extrapolated to human neonates is unclear.

METHODS/MATERIALS

This is a prospective follow-up project conducted in Western Canada. In all infants ≤6 weeks of age having surgery for congenital heart disease between April 2003 and December 2006, demographic and perioperative variables were collected prospectively. Sedation/analgesia variables were collected retrospectively. For each drug class (inhalationals, opioids, benzodiazepines, ketamine, and chloral hydrate), we calculated the cumulative dose received during hospitalization, average dose received per day, and cumulative number of days the patient received the drug. The outcomes at 18-24 months were as follows: General Adaptive Composite and motor scaled scores of the Adaptive Behavior Assessment System, significant mental, motor, and vocabulary delay. Multivariable logistic and linear regression was used to analyze the data.

RESULTS

One hundred and thirty-five neonates underwent open heart surgery; 19 died, 16 had chromosomal abnormality, and five were lost to follow up, leaving 95 survivors for analysis. Multiple linear regression analysis found no evidence of an association between sedation/analgesia variables and ABAS-GAC score or motor scale score. Multiple logistic regression analysis found no evidence of an association between sedation/analgesia variables and significant mental, motor, or vocabulary delay.

CONCLUSION

We found no evidence of an association between dose and duration of sedation/analgesia drugs during the operative and perioperative period and adverse neurodevelopmental outcomes.

Newly postulated neurodevelopmental risks of pediatric anesthesia

Recent animal and human studies have raised concern that exposure to anesthetic agents in children may cause neuronal damage and be associated with adverse neurodevelopmental outcomes. Exposure of young animals to anesthetic agents above threshold doses and durations during a critical neurodevelopmental window in the absence of concomitant painful stimuli causes widespread neuronal apoptosis and subsequent abnormal behaviors. The relevance of such animal data to humans is unknown. Untreated neonatal pain and stress also are associated with enhanced neuronal death and subsequent maladaptive behaviors, which can be prevented by exposure to these same anesthetic agents. Retrospective observational human studies have suggested a dose-dependent association between multiple anesthetic exposures in early childhood and subsequent learning disability, the causality of which is unknown. Ongoing prospective investigations are underway, the results of which may clarify if and what neurodevelopmental risks are associated with pediatric anesthesia. No change in current practice is yet indicated.

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.

Validation of a preclinical spinal safety model: effects of intrathecal morphine in the neonatal rat

BACKGROUND

Preclinical studies demonstrate increased neuroapoptosis after general anesthesia in early life. Neuraxial techniques may minimize potential risks, but there has been no systematic evaluation of spinal analgesic safety in developmental models. We aimed to validate a preclinical model for evaluating dose-dependent efficacy, spinal cord toxicity, and long-term function after intrathecal morphine in the neonatal rat.

METHODS

Lumbar intrathecal injections were performed in anesthetized rats aged postnatal day (P) 3, 10, and 21. The relationship between injectate volume and segmental spread was assessed postmortem and by in vivo imaging. To determine the antinociceptive dose, mechanical withdrawal thresholds were measured at baseline and 30 min after intrathecal morphine. To evaluate toxicity, doses up to the maximum tolerated were administered, and spinal cord histopathology, apoptosis, and glial response were evaluated 1 and 7 days after P3 or P21 injection. Sensory thresholds and gait analysis were evaluated at P35.

RESULTS

Intrathecal injection can be reliably performed at all postnatal ages and injectate volume influences segmental spread. Intrathecal morphine produced spinally mediated analgesia at all ages with lower dose requirements in younger pups. High-dose intrathecal morphine did not produce signs of spinal cord toxicity or alter long-term function.

CONCLUSIONS

The therapeutic ratio for intrathecal morphine (toxic dose/antinociceptive dose) was at least 300 at P3 and at least 20 at P21 (latter doses limited by side effects). These data provide relative efficacy and safety for comparison with other analgesic preparations and contribute supporting evidence for the validity of this preclinical neonatal safety model.

Effects of intrathecal ketamine in the neonatal rat: evaluation of apoptosis and long-term functional outcome

BACKGROUND

Systemic ketamine can trigger apoptosis in the brain of rodents and primates during susceptible developmental periods. Clinically, spinally administered ketamine may improve the duration or quality of analgesia in children. Ketamine-induced spinal cord toxicity has been reported in adult animals but has not been systematically studied in early development.

METHODS

In anesthetized rat pups, intrathecal ketamine was administered by lumbar percutaneous injection. Changes in mechanical withdrawal threshold evaluated dose-dependent antinociceptive and carrageenan-induced antihyperalgesic effects in rat pups at postnatal day (P) 3 and 21. After intrathecal injection of ketamine at P3, 7, or 21, spinal cords were examined for apoptosis (Fluoro-Jade C and activated caspase-3), histopathologic change, and glial responses (ionized calcium-binding adapter molecule 1 and glial fibrillary acid protein). After maximal doses of ketamine or saline at P3 or P21, sensory thresholds and gait analysis were evaluated at P35.

RESULTS

Intrathecal injection of 3 mg/kg ketamine at P3 and 15 mg/kg at P21 reverses carrageenan-induced hyperalgesia. Baseline neuronal apoptosis in the spinal cord was greater at P3 than P7, predominantly in the dorsal horn. Intrathecal injection of 3-10 mg/kg ketamine in P3 pups (but not 15 mg/kg at P21) acutely increased apoptosis and microglial activation in the spinal cord and altered spinal function (reduced mechanical withdrawal threshold and altered static gait parameters) at P35.

CONCLUSIONS

Because acute pathology and long-term behavioral change occurred in the same dose range as antihyperalgesic effects, the therapeutic ratio of intrathecal ketamine is less than one in the neonatal rat. This measure facilitates comparison of the relative safety of spinally administered analgesic agents.

Fundamentals of neuronal apoptosis relevant to pediatric anesthesia

The programmed cell death or apoptosis is a complex biochemical process that has risen to prominence in pediatric anesthesia. Preclinical studies report a dose-dependent neuronal apoptosis during synaptogenesis following exposure to intravenous and volatile anesthetic agents. Although emerging clinical data do not universally indicate an increased neurodegenerative risk of general anesthesia in early human life, a great deal of uncertainty was created within the pediatric anesthesia community. This was at least partially caused by the demand of understanding of basic science concepts and knowledge of apoptosis frequently out of reach to the clinician. It is, however, important for the pediatric anesthesiologist to be familiar with the basic science concepts of neuronal apoptosis to be able to critically evaluate current and future preclinical data in this area and future clinical studies. This current review describes the extrinsic and intrinsic pathways involved in the cell death process and discusses techniques commonly employed to determine apoptosis. In addition, potential mechanisms of anesthesia-induced neuronal apoptosis are illustrated in this review.

Is age-dependent, ketamine-induced apoptosis in the rat somatosensory cortex influenced by temperature?

General anesthetics have long been thought to be relatively safe but recent clinical studies have revealed that exposure of very young children (4 years or less) to agents that act by blocking the N-methyl-D-aspartate receptor (NMDAR) can lead to cognitive deficits as they mature. In rodent and non-human primate studies, blockade of this receptor during the perinatal period leads to a number of molecular, cellular and behavioral pathologies. Despite the overwhelming evidence from such studies, doubt remains as to their clinical relevance. A key issue is whether the primary injury (apoptotic cell death) is specific to receptor blockade or due to non-specific, patho-physiological changes. Principal to this argument is that loss of core body temperature following NMDAR blockade could explain why injury is observed hours later. We therefore examined the neurotoxicity of the general anesthetic ketamine in P7, P14 and P21 rats while monitoring core body temperature. We found that, at P7, ketamine induced the pro-apoptotic enzyme activated caspase-3 in a dose-dependent manner. As expected, injury was greatly diminished by P14 and absent by P21. However, contrary to expectations, we found that core body temperature was not a factor in determining injury. Our data imply that injury is directly related to receptor blockade and is unlikely to be overcome by artificially changing core body temperature.