Neurotoxic effects of dexmedetomidine in fetal cynomolgus monkey brains

Intranasal dexmedetomidine for transthoracic echocardiography in infants with shunt-dependent single ventricle heart disease

OBJECTIVES

We investigated the efficacy and complication profile of intranasal dexmedetomidine for transthoracic echocardiography sedation in patients with single ventricle physiology and shunt-dependent pulmonary blood flow during the high-risk interstage period.

METHODS

A single-centre, retrospective review identified interstage infants who received dexmedetomidine for echocardiography sedation. Baseline and procedural vitals were reported. Significant adverse events related to sedation were defined as an escalation in care or need for any additional/increased inotropic support to maintain pre-procedural haemodynamics. Minor adverse events were defined as changes from baseline haemodynamics that resolved without intervention. To assess whether sedation was adequate, echocardiogram reports were reviewed for completeness.

RESULTS

From September to December 2020, five interstage patients (age 29-69 days) were sedated with 3 mcg/kg intranasal dexmedetomidine. The median sedation onset time and duration time was 24 minutes (range 12-43 minutes) and 60 minutes (range 33-60 minutes), respectively. Sedation was deemed adequate in all patients as complete echocardiograms were accomplished without a rescue dose. When compared to baseline, three (60%) patients had a >10% reduction in heart rate, one (20%) patient had a >10% reduction in oxygen saturations, and one (20%) patient had a >30% decrease in blood pressure. Amongst all patients, no significant complications occurred and haemodynamic changes from baseline did not result in need for intervention or interruption of study.

CONCLUSIONS

Intranasal dexmedetomidine may be a reasonable option for echocardiography sedation in infants with shunt-dependent single ventricle heart disease, and further investigation is warranted to ensure efficacy and safety in an outpatient setting.

Comparison of oral triclofos and intranasal midazolam and dexmedetomidine for sedation in children undergoing magnetic resonance imaging (MRI): an open-label, three-arm, randomized trial

The purpose of this study was to compare the efficacy of oral triclofos (TRI), intranasal midazolam (INM), and intranasal dexmedetomidine (IND) in achieving successful sedation in children undergoing MRI. This open-label, three-arm, randomized trial was conducted in a tertiary care teaching hospital over 18-month period. Children scheduled for MRI were enrolled. Rate of successful/adequate sedation was assessed using the Paediatric Sedation State Scale (PSSS). The primary outcome was the efficacy (successful sedation or sedation rate) of the three drugs. One-hundred and ninety-five children were included for the MRI procedure. IND was found to be superior in terms of achieving successful sedation. INM had a shorter onset and duration of sedation compared to IND and TRI, but with an increased failure rate (88.3%). Keeping INM as the reference group, it was found that the odds of sedation increased 4.1 times on changing from INM to IND (p < 0.01), and 2.26 times on changing from INM to TRI (p < 0.01). Adverse events included nasal discomfort (18.3%) in INM group; and self-limited tachycardia (4.6%) and hypotension (10.8%) in the IND group.

CONCLUSION

IND was more efficacious than INM or TRI for procedural sedation in children undergoing MRI without any significant adverse events.

CLINICAL TRIAL REGISTRATION

CTRI/2019/01/017257; date registered: 25/01/2019.

WHAT IS KNOWN

• Oral triclofos (TRI) and intranasal midazolam (INM) have been used for procedural sedation in children undergoing MRI with variable success; but the experience with intranasal dexmedetomidine (IND) is limited.

WHAT IS NEW

• IND provides more effective sedation compared to INM or TRI for procedural sedation in children undergoing MRI, without any significant adverse events.

Safety of general anaesthetics on the developing brain: are we there yet?

Thirty years ago, neurotoxicity induced by general anaesthetics in the developing brain of rodents was observed. In both laboratory-based and clinical studies, many conflicting results have been published over the years, with initial data confirming both histopathological and neurodevelopmental deleterious effects after exposure to general anaesthetics. In more recent years, animal studies using non-human primates and new human cohorts have identified some specific deleterious effects on neurocognition. A clearer pattern of neurotoxicity seems connected to exposure to repeated general anaesthesia. The biochemistry involved in this neurotoxicity has been explored, showing differential effects of anaesthetic drugs between the developing and developed brains. In this narrative review, we start with a comprehensive description of the initial concerning results that led to recommend that any non-essential surgery should be postponed after the age of 3 yr and that research into this subject should be stepped up. We then focus on the neurophysiology of the developing brain under general anaesthesia, explore the biochemistry of the observed neurotoxicity, before summarising the main scientific and clinical reports investigating this issue. We finally discuss the GAS trial, the importance of its results, and some potential limitations that should not undermine their clinical relevance. We finally suggest some key points that could be shared with parents, and a potential research path to investigate the biochemical effects of general anaesthesia, opening up perspectives to understand the neurocognitive effects of repetitive exposures, especially in at-risk children.

Assessing and conveying risks and benefits of imaging in neonates using ionizing radiation and sedation/anesthesia

Neonates represent a unique subset of the pediatric population that requires special attention and careful thought when implementing advanced cross-sectional imaging with CT or MRI. The ionizing radiation associated with CT and the sedation/anesthesia occasionally required for MRI present risks that must be balanced against the perceived benefit of the imaging examination in the unique and particularly susceptible neonatal population. We review the perceived risks of ionizing radiation and the more concrete risks of sedation/anesthesia in term and preterm neonates in the context of an imaging paradigm. When the expected diagnostic yield from CT and MRI is similar, and sedation is required for MRI but not for CT, CT likely has the higher benefit-to-risk ratio in the neonate. However, despite the risks, the most appropriate imaging modality should always be chosen after thoughtful consideration is given to each unique patient and informed discussions including radiology, anesthesia, neonatology and the parents/caregivers are pursued.

Anesthesia and Developing Brains: Unanswered Questions and Proposed Paths Forward

Anesthetic agents disrupt neurodevelopment in animal models, but evidence in humans is mixed. The morphologic and behavioral changes observed across many species predicted that deficits should be seen in humans, but identifying a phenotype of injury in children has been challenging. It is increasingly clear that in children, a brief or single early anesthetic exposure is not associated with deficits in a range of neurodevelopmental outcomes including broad measures of intelligence. Deficits in other domains including behavior, however, are more consistently reported in humans and also reflect findings from nonhuman primates. The possibility that behavioral deficits are a phenotype, as well as the entire concept of anesthetic neurotoxicity in children, remains a source of intense debate. The purpose of this report is to describe consensus and disagreement among experts, summarize preclinical and clinical evidence, suggest pathways for future clinical research, and compare studies of anesthetic agents to other suspected neurotoxins.

Strengths and challenges of longitudinal non-human primate neuroimaging

Longitudinal non-human primate neuroimaging has the potential to greatly enhance our understanding of primate brain structure and function. Here we describe its specific strengths, compared to both cross-sectional non-human primate neuroimaging and longitudinal human neuroimaging, but also its associated challenges. We elaborate on factors guiding the use of different analytical tools, subject-specific versus age-specific templates for analyses, and issues related to statistical power.

Effects of Pregnancy Anesthesia on Fetal Nervous System

The effects of general anesthesia on the developing brain remain a great concern in the medical field and even in the public, and most researches in this area focus on infancy and childhood. In recent years, with the continuous development of medical technology, the number of operations during pregnancy is increasing, however, studies on general anesthesia during pregnancy are relatively lacking. The mid-trimester of pregnancy is a critical period, and is regarded as a safe period for surgery, but it is a fragile period for the development of the central nervous system and is particularly sensitive to the impact of the environment. Our research group found that general anesthesia may have adverse effects on fetal neurodevelopment during the mid-trimester. Therefore, in this review, we summarize the characteristics of anesthesia during pregnancy, and the related research of the anesthesia’s impacts on the development of central nervous system were introduced.

Neuroprotection of the Developing Brain by Dexmedetomidine Is Mediated by Attenuating Single Propofol-induced Hippocampal Apoptosis and Synaptic Plasticity Deficits

Dexmedetomidine (DEX) has neuroprotective effects and its efficacy was determined in propofol-treated pups. Postnatal day (P) 7 rats were exposed to propofol and DEX to investigate the induced apoptosis-related gene expression. Furthermore, synaptic structural changes at the cellular level were observed by electron microscopy. Induction of hippocampal long-term potentiation (LTP) of P30 rats and long-lasting performance of spatial discrimination at P30 and P60 were evaluated. After a single propofol exposure to P7 rats, DEX pretreatment effectively rescued the profound apoptosis seen in hippocampal neurocytes, and strongly reversed the aberrant expression levels of Bcl2-like 1 (BCL2L1), matrix metallopeptidase 9 (MMP-9) and cleaved caspase 3 (CC3), and sharply enhanced synaptic plasticity. However, there were no significant differences in escape latency or crossing times in a probe test. This was accompanied by no obvious reduction in search strategies among the rat groups. No impairment of long-term learning and memory in P30 or P60 rats was detected when using a single dose propofol treatment during the most vulnerable period of brain development. DEX was shown to ameliorate the rodent developmental neurotoxicity caused by a single neonatal propofol challenge, by altering MMP-9, BCL2L1 and CC3 apoptotic signaling.

Research progress and treatment strategies for anesthetic neurotoxicity

Every year, a large number of infants and young children worldwide are administered general anesthesia. Whether general anesthesia adversely affects the intellectual development and cognitive function of children at a later date remains controversial. Many animal experiments have shown that general anesthetics can cause nerve damage during development, affect synaptic plasticity, and induce apoptosis, and finally affect learning and memory function in adulthood. The neurotoxicity of pediatric anesthetics (PAN) has received extensive attention in the field of anesthesia, which has been listed as a potential problem affecting public health by NFDA of the United States. Previous studies on rodents and non-human primates indicate that inhalation of anesthetics early after birth can induce long-term and sustained impairment of learning and memory function, as well as changes in brain function. Many anti-oxidant drugs, dexmedetomidine, as well as a rich living environment and exercise have been proven to reduce the neurotoxicity of anesthetics. In this paper, we summarize the research progress, molecular mechanisms and current intervention measures of anesthetic neurotoxicity.

Intranasal dexmedetomidine for sedation in children; a review

Dexmedetomidine is an α2 adrenoreceptor agonist that may be administered by the intranasal route as a sole sedative agent in children. It is odourless, colourless and tasteless and is formulated in a concentration of 100µg.ml^-1. We performed a review of published randomised controlled trials in order to determine the efficacy of intranasal dexmedetomidine for sedation in children. Fourteen trials were eligible for inclusion in the review and contained a total of 1809 patients ranging in age from one month to 14 years. Intranasal dexmedetomidine was administered in a dose range of 1-4µg.kg^-1 and was compared with various other sedatives. Dexmedetomidine was administered by either drops or a mucosal atomiser device. The procedures ranged from non-painful examinations such as magnetic resonance imaging scans and transthoracic echocardiography to painful procedures such as dentistry and venous cannulation. Administration of 2µg.kg^-1 appears to be the optimal dose.

Intranasal Dexmedetomidine for Procedural Distress in Children: A Systematic Review

CONTEXT

Intranasal dexmedetomidine (IND) is an emerging agent for procedural distress in children.

OBJECTIVE

To explore the effectiveness of IND for procedural distress in children.

DATA SOURCES

We performed electronic searches of Medline (1946-2019), Embase (1980-2019), Google Scholar (2019), Cumulative Index to Nursing and Allied Health Literature (1981-2019), and Cochrane Central Register.

STUDY SELECTION

We included randomized trials of IND for procedures in children.

DATA EXTRACTION

Methodologic quality of evidence was evaluated by using the Cochrane Collaboration's risk of bias tool and the Grading of Recommendations Assessment, Development, and Evaluation system, respectively. The primary outcome was the proportion of participants with adequate sedation.

RESULTS

Among 19 trials (N = 2137), IND was superior to oral chloral hydrate (3 trials), oral midazolam (1 trial), intranasal midazolam (1 trial), and oral dexmedetomidine (1 trial). IND was equivalent to oral chloral hydrate (2 trials), intranasal midazolam (2 trials), and intranasal ketamine (3 trials). IND was inferior to oral ketamine and a combination of IND plus oral ketamine (1 trial). Higher doses of IND were superior to lower doses (4 trials). Adverse effects were reported in 67 of 727 (9.2%) participants in the IND versus 98 of 591 (16.6%) in the comparator group. There were no reports of adverse events requiring resuscitative measures.

LIMITATIONS

The adequacy of sedation was subjective, which possibly led to biased outcome reporting.

CONCLUSIONS

Given the methodologic limitations of included trials, IND is likely more effective at sedating children compared to oral chloral hydrate and oral midazolam. However, this must be weighed against the potential for adverse cardiovascular effects.

Dexmedetomidine improves neurodevelopment and cognitive impairment in infants with congenital heart disease

Aim: Explore if dexmedetomidine (DEX) improves neurodevelopment and cognitive impairment in infants with congenital heart disease. Materials & methods: We retrospectively analyzed 256 pediatric patients aged less than 2 years with heart disease undergoing thoracic surgery. The intelligence quotient and neurodevelopment were tested. Mortality, incidence of postoperation adverse events, duration of mechanical ventilation, and length of stay were recorded and compared. Results: Compared with those not administered DEX, intelligence quotient scores and neurodevelopment evaluation scores increased in patients receiving perioperative DEX. There were no significant differences in mortality, duration of mechanical ventilation or length of stay. Conclusion: The administration of DEX might improve neural development and reduce the adverse effects of general anesthesia in infants with congenital heart disease undergoing surgery and extracorporeal circulation.

Results of a phase 1 multicentre investigation of dexmedetomidine bolus and infusion in corrective infant cardiac surgery

BACKGROUND

Dexmedetomidine (DEX) is increasingly used intraoperatively in infants undergoing cardiac surgery. This phase 1 multicentre study sought to: (i) determine the safety of DEX for cardiac surgery with cardiopulmonary bypass; (ii) determine the pharmacokinetics (PK) of DEX; (iii) create a PK model and dosing for steady-state DEX plasma levels; and (iv) validate the PK model and dosing.

METHODS

We included 122 neonates and infants (0-180 days) with D-transposition of the great arteries, ventricular septal defect, or tetralogy of Fallot. Dose escalation was used to generate NONMEM® PK modelling, and then validation was performed to achieve low (200-300 pg ml-1), medium (400-500 pg ml-1), and high (600-700 pg ml-1) DEX plasma concentrations.

RESULTS

Five of 122 subjects had adverse safety outcomes (4.1%; 95% confidence interval [CI], 1.8-9.2%). Two had junctional rhythm, two had second-/third-degree atrioventricular block, and one had hypotension. Clearance (CL) immediately postoperative and CL on CPB were reduced by approximately 50% and 95%, respectively, compared with pre-CPB CL. DEX clearance after CPB was 1240 ml min-1 70 kg-1. Age at 50% maximum clearance was approximately 2 days, and that at 90% maximum clearance was 18 days. Overall, 96.1% of measured DEX concentrations fell within the 5th-95th percentile prediction intervals in the PK model validation. Dosing strategies are recommended for steady-state DEX plasma levels ranging from 200 to 1000 pg ml-1.

CONCLUSIONS

When used with a careful dosing strategy, DEX results in low incidence and severity of adverse safety events in infants undergoing cardiac surgery with cardiopulmonary bypass. This validated PK model should assist clinicians in selecting appropriate dosing. The results of this phase 1 trial provide preliminary data for a phase 3 trial of DEX neuroprotection.

CLINICAL TRIALS REGISTRATION

NCT01915277.

Practicalities of Total Intravenous Anesthesia and Target-controlled Infusion in Children

Propofol administered in conjunction with an opioid such as remifentanil is used to provide total intravenous anesthesia for children. Drugs can be given as infusion controlled manually by the physician or as automated target-controlled infusion that targets plasma or effect site. Smart pumps programmed with pharmacokinetic parameter estimates administer drugs to a preset plasma concentration. A linking rate constant parameter (keo) allows estimation of effect site concentration. There are two parameter sets, named after the first author describing them, that are commonly used in pediatric target-controlled infusion for propofol (Absalom and Kataria) and one for remifentanil (Minto). Propofol validation studies suggest that these parameter estimates are satisfactory for the majority of children. Recommended target concentrations for both propofol and remifentanil depend on the type of surgery, the degree of surgical stimulation, the use of local anesthetic blocks, and the ventilatory status of the patient. The use of processed electroencephalographic monitoring is helpful in pediatric total intravenous anesthesia and target-controlled infusion anesthesia, particularly in the presence of neuromuscular blockade.

Dexmedetomidine attenuates the neurotoxicity of propofol toward primary hippocampal neurons in vitro via Erk1/2/CREB/BDNF signaling pathways

BACKGROUND

Propofol is a commonly used general anesthetic for the induction and maintenance of anesthesia and critical care sedation in children, which may add risk to poor neurodevelopmental outcome. We aimed to evaluate the effect of propofol toward primary hippocampal neurons in vitro and the possibly neuroprotective effect of dexmedetomidine pretreatment, as well as the underlying mechanism.

MATERIALS AND PROCEDURES

Primary hippocampal neurons were cultured for 8 days in vitro and pretreated with or without dexmedetomidine or phosphorylation inhibitors prior to propofol exposure. Cell viability was measured using cell counting kit-8 assays. Cell apoptosis was evaluated using a transmission electron microscope and flow cytometry analyses. Levels of mRNAs encoding signaling pathway intermediates were assessed using qRT-PCR. The expression of signaling pathway intermediates and apoptosis-related proteins was determined by Western blotting.

RESULTS

Propofol significantly reduced cell viability, induced neuronal apoptosis, and downregulated the expression of the BDNF mRNA and the levels of the phospho-Erk1/2 (p-Erk1/2), phospho-CREB (p-CREB), and BDNF proteins. The dexmedetomidine pretreatment increased neuronal viability and alleviated propofol-induced neuronal apoptosis and rescued the propofol-induced downregulation of both the BDNF mRNA and the levels of the p-Erk1/2, p-CREB, and BDNF proteins. However, this neuroprotective effect was abolished by PD98059, H89, and KG501, further preventing the dexmedetomidine pretreatment from rescuing the propofol-induced downregulation of the BDNF mRNA and p-Erk1/2, p-CREB, and BDNF proteins.

CONCLUSION

Dexmedetomidine alleviates propofol-induced cytotoxicity toward primary hippocampal neurons in vitro, which correlated with the activation of Erk1/2/CREB/BDNF signaling pathways.

A systematic review and narrative synthesis on the histological and neurobehavioral long-term effects of dexmedetomidine

BACKGROUND

Recent experimental studies suggest that currently used anesthetics have neurotoxic effects on young animals. Clinical studies are increasingly publishing about the effects of anesthesia on the long-term outcome, providing contradictory results. The selective alpha-2 adrenergic receptor agonist dexmedetomidine has been suggested as an alternative nontoxic sedative agent.

AIMS

The aim of this systematic review was to assess the potential neuroprotective and neurobehavioral effects of dexmedetomidine in young animals and children.

METHODS

Systematic searches separately for preclinical and clinical studies were performed in Medline Ovid and Embase on February 14, 2018.

RESULTS

The initial search found preclinical (n = 661) and clinical (n = 240) studies. A total of 20 preclinical studies were included. None of the clinical studies met the predefined eligibility criteria. Histologic injury by dexmedetomidine was evaluated in 11 studies, and was confirmed in three of these studies (caspase-3 activation or apoptosis). Decrease of injury caused by another anesthetic was evaluated in 16 studies and confirmed in 13 of these. Neurobehavioral tests were performed in seven out of the 20 studies. Of these seven rodent studies, three studies tested the effects of dexmedetomidine alone on neurobehavioral outcome in animals (younger than P21). All three studies found no negative effect of dexmedetomidine on the outcome. In six studies, outcome was evaluated when dexmedetomidine was administered following another anesthetic. Dexmedetomidine was found to lessen the negative effects of the anesthetic.

CONCLUSION

In animals, dexmedetomidine was found not to induce histologic injury and to show a beneficial effect when administered with another anesthetic. No clinical results on the long-term effects in children have been identified yet.

Alternative technique or mitigating strategy for sevoflurane-induced neurodegeneration: a randomized controlled dose-escalation study of dexmedetomidine in neonatal rats

Background

Brain injury in newborn animals from prolonged anaesthetic exposure has raised concerns for millions of children undergoing anaesthesia every yr. Alternative anaesthetic techniques or mitigating strategies are urgently needed to ameliorate potentially harmful effects. We tested dexmedetomidine, both as a single agent alternative technique and as a mitigating adjuvant for sevoflurane anaesthesia.

Methods

Neonatal rats were randomized to three injections of dexmedetomidine (5, 25, 50, or 100 µg kg -1 every 2 h), or 6 h of 2.5% sevoflurane as a single agent without or with dexmedetomidine (1, 5, 10, or 20 µg kg -1 every 2 h). Heart rate, oxygen saturation, level of consciousness, and response to pain were assessed. Cell death was quantified in several brain regions.

Results

Dexmedetomidine provided lower levels of sedation and pain control than sevoflurane. Exposure to either sevoflurane or dexmedetomidine alone did not cause mortality, but the combination of 2.5% sevoflurane and dexmedetomidine in doses exceeding 1 µg kg -1 did. Sevoflurane increased apoptosis in all brain regions; supplementation with dexmedetomidine exacerbated neuronal injury, potentially as a result of ventilatory or haemodynamic compromise. Dexmedetomidine by itself increased apoptosis only in CA2/3 and the ventral posterior nucleus, but not in prefrontal cortex, retrosplenial cortex, somatosensory cortex, subiculum, lateral dorsal thalamic nucleaus, or hippocampal CA1.

Conclusions

We confirm previous findings of sevoflurane-induced neuronal injury. Dexmedetomidine, even in the highest dose, did not cause similar injury, but provided lesser degrees of anaesthesia and pain control. No mitigation of sevoflurane-induced injury was observed with dexmedetomidine supplementation, suggesting that future studies should focus on anaesthetic-sparing effects of dexmedetomidine, rather than injury-preventing effects.

Phase IV, Open-Label, Safety Study Evaluating the Use of Dexmedetomidine in Pediatric Patients Undergoing Procedure-Type Sedation

Dexmedetomidine (Precedex™) may be used as an alternative sedative in children, maintaining spontaneous breathing, and avoiding tracheal intubation in a non-intubated moderate or deep sedation (NI-MDS) approach. This open-label, single-arm, multicenter study evaluated the safety of dexmedetomidine in a pediatric population receiving NI-MDS in an operating room or a procedure room, with an intensivist or anesthesiologist in attendance, for elective diagnostic or therapeutic procedures expected to take at least 30 min. The primary endpoint was incidence of treatment-emergent adverse events (TEAEs). Patients received one of two doses dependent on age: patients aged ≥28 weeks' gestational age to <1 month postnatal received dose level 1 (0.1 μg/kg load; 0.05-0.2 μg/kg/h infusion); those aged 1 month to <17 years received dose level 2 (1 μg/kg load; 0.2-2.0 μg/kg/h infusion). Sedation efficacy was assessed and defined as adequate sedation for at least 80% of the time and successful completion of the procedure without the need for rescue medication. In all, 91 patients were enrolled (dose level 1, n = 1; dose level 2, n = 90); of these, 90 received treatment and 82 completed the study. Eight patients in dose level 2 discontinued treatment for the following reasons: early completion of diagnostic or therapeutic procedure (n = 3); change in medical condition (need for intubation) requiring deeper level of sedation (n = 2); adverse event (AE; hives and emesis), lack of efficacy, and physician decision (patient not sedated enough to complete procedure; n = 1 each). Sixty-seven patients experienced 147 TEAEs. The two most commonly reported AEs were respiratory depression (bradypnea; reported per protocol-defined criteria, based on absolute respiratory rate values for age or relative decrease of 30% from baseline) and hypotension. Four patients received glycopyrrolate for bradycardia and seven patients received intravenous fluids for hypotension. SpO₂ dropped by 10% in two patients, but resolved without need for manual ventilation. All other reported AEs were consistent with the known safety profile of dexmedetomidine. Two of the 78 patients in the efficacy-evaluable population met all sedation efficacy criteria. Dexmedetomidine was well-tolerated in pediatric patients undergoing procedure-type sedation.

Dexmedetomidine sedation combined with caudal anesthesia for lower abdominal and extremity surgery in ex-preterm and full-term infants

BACKGROUND

Awake caudal anesthesia is a potentially attractive option, because the administration of general anesthesia is associated with a high rate of respiratory complications and hemodynamic disturbances and potential neurotoxic effects. To facilitate the caudal puncture and subsequent surgical intervention, additional sedatives are commonly administered.

AIM

We aimed to establish a new, safe, and effective anesthetic procedure for very young children with comorbidities.

METHODS

We retrospectively analyzed 23 children who underwent lower abdominal or lower extremity surgery with dexmedetomidine sedation and caudal anesthesia from January 2015 to August 2015. Dexmedetomidine was initiated with a total bolus infusion of 0.7-1.1 μg·kg^-1 followed by a continuous infusion of 1 μg·kg^-1 ·h^-1 . Bupivacaine (2.5 mg·kg^-1 ) was supplemented with 5-10 μg·kg^-1 epinephrine to strengthen and prolong motor block. According to maturity at birth, two groups were defined: ex-preterm and full-term infants.

RESULTS

There were 12 ex-preterm and 10 full-term infants available for analysis. The median postmenstrual age was 44 (38-52) weeks in ex-preterm and 46.5 (40-72) weeks in full-term infants. Without any additional intervention, surgery was successfully accomplished in 82% of all cases. While respiratory complications were not a problem, hemodynamic disturbances commonly occurred. Maximum decreases in heart rate (HR) of 30% were accompanied by maximum decreases in mean arterial pressure (MAP) of 38%. No infant had a heart rate below 100 bpm. MAP declined in one ex-preterm infant to a minimum value of 32 mmHg.

CONCLUSION

Caudal anesthesia combined with dexmedetomidine sedation is an effective anesthetic technique for lower abdominal and extremity surgery in ex-preterm and full-term infants with severe comorbidities.

General Anesthesia During the Third Trimester: Any Link to Neurocognitive Outcomes?

Rodent studies on the effect of general anesthesia during the third trimester on neurocognitive outcomes are mixed, but primate studies suggest that a clinically relevant exposure to anesthetic agents during the third trimester can trigger neuronal and glial cell death. Human studies are conflicting and the evidence is weak. This is an up-to-date review of the literature on the neurodevelopmental effects of anesthetic agents administered during the third trimester. Early brain development and critical periods of neurodevelopment as it relates to neurotoxicity are highlighted. Rodent, nonhuman primate, and population studies are discussed and placed in the context of clinical practice.

Dexmedetomidine Use in Critically Ill Children With Acute Respiratory Failure

OBJECTIVE

Care of critically ill children includes sedation but current therapies are suboptimal. To describe dexmedetomidine use in children supported on mechanical ventilation for acute respiratory failure.

DESIGN

Secondary analysis of data from the Randomized Evaluation of Sedation Titration for Respiratory Failure clinical trial.

SETTING

Thirty-one PICUs.

PATIENTS

Data from 2,449 children; 2 weeks to 17 years old.

INTERVENTIONS

Sedation practices were unrestrained in the usual care arm. Patients were categorized as receiving dexmedetomidine as a primary sedative, secondary sedative, periextubation agent, or never prescribed. Dexmedetomidine exposure and sedation and clinical profiles are described.

MEASUREMENTS AND MAIN RESULTS

Of 1,224 usual care patients, 596 (49%) received dexmedetomidine. Dexmedetomidine as a primary sedative patients (n = 138; 11%) were less critically ill (Pediatric Risk of Mortality III-12 score median, 6 [interquartile range, 3-11]) and when compared with all other cohorts, experienced more episodic agitation. In the intervention group, time in sedation target improved from 28% to 50% within 1 day of initiating dexmedetomidine as a primary sedative. Dexmedetomidine as a secondary sedative usual care patients (n = 280; 23%) included more children with severe pediatric acute respiratory distress syndrome or organ failure. Dexmedetomidine as a secondary sedative patients experienced more inadequate pain (22% vs 11%) and sedation (31% vs 16%) events. Dexmedetomidine as a periextubation agent patients (n = 178; 15%) were those known to not tolerate an awake, intubated state and experienced a shorter ventilator weaning process (2.1 vs 2.3 d).

CONCLUSIONS

Our data support the use of dexmedetomidine as a primary agent in low criticality patients offering the benefit of rapid achievement of targeted sedation levels. Dexmedetomidine as a secondary agent does not appear to add benefit. The use of dexmedetomidine to facilitate extubation in children intolerant of an awake, intubated state may abbreviate ventilator weaning. These data support a broader armamentarium of pediatric critical care sedation.

Do anesthetics harm the developing human brain? An integrative analysis of animal and human studies

Anesthetics that permit surgical procedures and stressful interventions have been found to cause structural brain abnormalities and functional impairment in immature animals, generating extensive concerns among clinicians, parents, and government regulators regarding the safe use of these drugs in young children. Critically important questions remain, such as the exact age at which the developing brain is most vulnerable to the effects of anesthetic exposure, whether a particular age exists beyond which anesthetics are devoid of long-term effects on the brain, and whether any specific exposure duration exists that does not lead to deleterious effects. Accordingly, the present analysis attempts to put the growing body of animal studies, which we identified to include >440 laboratory studies to date, into a translational context, by integrating the preclinical data on brain structure and function with clinical results attained from human neurocognitive studies, which currently exceed 30 studies. Our analysis demonstrated no clear exposure duration threshold below which no structural injury or subsequent cognitive abnormalities occurred. Animal data did not clearly identify a specific age beyond which anesthetic exposure did not cause any structural or functional abnormalities. Several potential mitigating strategies were found, however, no general anesthetic was identified that consistently lacked neurodegenerative properties and could be recommended over other anesthetics. It therefore is imperative, to expand efforts to devise safer anesthetic techniques and mitigating strategies, even before long-term alterations in brain development are unequivocally confirmed to occur in millions of young children undergoing anesthesia every year.

A pilot study of dexmedetomidine sedation and caudal anesthesia for inguinal hernia repair in infants

BACKGROUND

Recent concerns regarding possible long-term effects of early anesthesia exposure on neurodevelopment in children have provided an impetus to explore alternative anesthetic techniques using potentially neuroprotective agents. Dexmedetomidine has not been implicated in anesthesia-induced neurotoxicity and has been shown to be neuroprotective in preclinical studies. We describe a case series of 50 neonates and infants who received dexmedetomidine sedation with caudal anesthesia instead of general endotracheal anesthesia for inguinal hernia surgery.

METHODS

We conducted a retrospective chart review on all neonates and infants who underwent inguinal hernia surgery with dexemetomidine sedation and caudal anesthesia in our institution. We started exploring this technique since October 2011 and established a protocol of administering dexmedetomidine 2 mcg·kg(-1) over 10 min, followed by 1 mcg·kg(-1) over the next 10 min. This led to satisfactory conditions for caudal placement in 20 min, with minimal need for airway intervention during surgery.

RESULTS

The median gestational age of the infants was 31.4 (28.7, 36.0) weeks and median postconceptual age was 39.7 weeks (IQR 37.8, 45.7) at time of surgery. Of patients, 86% had surgery successfully completed under this technique alone. Seven patients required sevoflurane or nitrous oxide due to failed caudal block (n = 1) or difficult or prolonged surgery (n = 6). After establishing the sedation protocol and excluding patients with large or complicated hernias, the success rate was 96%. Transient intra-operative apnea or hypoventilation occurred in five patients and postoperative apnea in two patients. All respiratory events were easily reversed and no patient developed significant bradycardia or required intubation.

CONCLUSIONS

Dexmedetomidine sedation with caudal anesthesia is a feasible alternative to spinal or general anesthesia in selected infants undergoing uncomplicated hernia surgery. It avoids the need for endotracheal intubation and may be potentially beneficial in avoiding the unknown effects of general anesthesia on neurodevelopment.

Neonatal exposure to sevoflurane may not cause learning and memory deficits and behavioral abnormality in the childhood of Cynomolgus monkeys

Results of animal studies have raised a significant concern that commonly used general anesthetics may induce neurotoxicity in children. It may be difficult to resolve this concern with human studies because randomizing children only for testing anesthetic toxicity may not be feasible. We randomized 6-day old male Cynomolgus monkeys to receive or not to receive sevoflurane anesthesia at surgical plane for 5 h. Sevoflurane is the most commonly used general anesthetic in children in the U.S.A. Here, we showed that sevoflurane anesthesia did not affect the behavior evaluated by holding cage method when the monkeys were 3 and 7 months old. However, there was an age-dependent decrease in the frequency of stress events and environmental exploration behavior during the test. Sevoflurane also did not affect the learning and memory of the monkeys when they were assessed from the age of 7 months. Finally, sevoflurane did not affect the expression of multiple neuron-specific proteins in the hippocampus and cerebral cortex of 10-month old monkeys after all behavioral and cognitive tests were completed. These results suggest that exposure of neonatal monkey to sevoflurane may not affect cognition, behavior and neuronal structures in childhood, indicating the safety of sevoflurane anesthesia in children.

Neuroprotective effect of dexmedetomidine on hyperoxia-induced toxicity in the neonatal rat brain

Dexmedetomidine is a highly selective agonist of α2-receptors with sedative, anxiolytic, analgesic, and anesthetic properties. Neuroprotective effects of dexmedetomidine have been reported in various brain injury models. In the present study, we investigated the effects of dexmedetomidine on neurodegeneration, oxidative stress markers, and inflammation following the induction of hyperoxia in neonatal rats. Six-day-old Wistar rats received different concentrations of dexmedetomidine (1, 5, or 10 µg/kg bodyweight) and were exposed to 80% oxygen for 24 h. Sex-matched littermates kept in room air and injected with normal saline or dexmedetomidine served as controls. Dexmedetomidine pretreatment significantly reduced hyperoxia-induced neurodegeneration in different brain regions of the neonatal rat. In addition, dexmedetomidine restored the reduced/oxidized glutathione ratio and attenuated the levels of malondialdehyde, a marker of lipid peroxidation, after exposure to high oxygen concentration. Moreover, administration of dexmedetomidine induced downregulation of IL-1β on mRNA and protein level in the developing rat brain. Dexmedetomidine provides protections against toxic oxygen induced neonatal brain injury which is likely associated with oxidative stress signaling and inflammatory cytokines. Our results suggest that dexmedetomidine may have a therapeutic potential since oxygen administration to neonates is sometimes inevitable.