Effects of repetitive exposure to pain and morphine treatment on the neonatal rat brain

Exposure to Sedation and Analgesia Medications: Short-term Cognitive Outcomes in Pediatric Critical Care Survivors With Acquired Brain Injury

Background/Objective: Pediatric intensive care unit (PICU) survivors risk significant cognitive morbidity, particularly those with acquired brain injury (ABI) diagnoses. Studies show sedative and analgesic medication may potentiate neurologic injury, but few studies evaluate impact on survivor outcomes. This study aimed to evaluate whether exposures to analgesic and sedative medications are associated with worse neurocognitive outcome. Methods: A retrospective cohort study was conducted of 91 patients aged 8 to 18 years, undergoing clinical neurocognitive evaluation approximately 1 to 3 months after PICU discharge. Electronic health data was queried for sedative and analgesic medication exposures, including opioids, benzodiazepines, propofol, ketamine, and dexmedetomidine. Doses were converted to class equivalents, evaluated by any exposure and cumulative dose exposure per patient weight. Cognitive outcome was derived from 8 objective cognitive assessments with an emphasis on executive function skills using Principal Components Analysis. Then, linear regression was used to control for baseline cognitive function estimates to calculate a standardized residualized neurocognitive index (rNCI) z-score. Multivariable linear regression evaluated the association between rNCI and medication exposure controlling for covariates. Significance was defined as P < .05. Results: Most (n = 80; 88%) patients received 1 or more study medications. Any exposure and higher cumulative doses of benzodiazepine and ketamine were significantly associated with worse rNCI in bivariate analyses. When controlling for Medicaid, preadmission comorbid conditions, length of stay, delirium, and receipt of other medication classes, receipt of benzodiazepine was associated with significantly worse rNCI (β-coefficient = -0.48, 95% confidence interval = -0.88, -0.08). Conclusions: Exposure to benzodiazepines was independently associated with worse acute phase cognitive outcome using objective assessments focused on executive function skills when controlling for demographic and illness characteristics. Clinician decisions regarding medication regimens in the PICU may serve as a modifiable factor to improve outcomes. Additional inquiry into associations with long-term cognitive outcome and optimal medication regimens is needed.

Effects of different types of neonatal pain on somatosensory and cognitive development in male juvenile rats

BACKGROUND

Premature infants are inevitably exposed to painful events, including repetitive procedures, inflammation, or mixed stimulation that may induce long-term behavioral outcomes. Here, we set up three neonatal painful models to investigate their long-term effect on somatosensation and cognition.

METHODS

Three types of neonatal pain models in rat were set up. Rat pups were randomly assigned to four groups. The needling pain (NP) group received repetitive needle pricks on the paws from the day of birth (PD0) to postnatal day 7 (PD7) to mimic the diagnostic and therapeutic procedures. The inflammatory pain (IP) group received the injection of carrageenan into the left hindpaw at PD3 to induce IP in peripheral tissues. The mixed pain group received a combination of the NP and IP (NIP). The control (CON) group was untreated. We performed behavioral and biochemical testing of juvenile rats (PD21-PD26).

RESULTS

The NIP group showed a longer hypersensitivity than the NP group, when given a secondary inflammatory stimulation. NP led to insensitivity to anxiety-causing stimuli and impairment of fear memory both aggravated by NIP. NP reduced the expression of synapse-related molecules (GluN1/PSD95/GFAP) in the medial prefrontal cortex, and NIP exacerbated this decrease. The corticosterone secretion in the NIP group increased after the behavioral task, compared with those in other three groups.

CONCLUSION

A combination of NP with inflammation occurring in the neonatal period might aggravate the adverse effects of each on somatosensory and cognitive development of rats, the mechanism of which might be associated with the increase of corticosterone secretion and the dysregulation of synaptic molecules.

Orientin Reduces the Effects of Repeated Procedural Neonatal Pain in Adulthood: Network Pharmacology Analysis, Molecular Docking Analysis, and Experimental Validation

Background

Premature infants often undergo painful procedures and consequently experience repeated procedural neonatal pain. This can elicit hyperalgesia and cognitive impairment in adulthood. Treatments for neonatal pain are limited. Orientin is a flavonoid C-glycoside that has repeatedly been shown to have pharmacological effects in the past decades. The aim of this study was to systematically explore the effect of orientin on repeated procedural neonatal pain using network pharmacology, molecular docking analysis, and experimental validation.

Methods

Several compound-protein databases and disease-protein databases were employed to identify proteins that were both predicted targets of orientin and involved in neonatal pain. A protein-protein interaction (PPI) network was constructed, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to explore the potential mechanism of action. Molecular docking analysis was employed to calculate the binding energy and visualize the interactions between orientin and potential target proteins. Finally, a mouse model of repeated procedural neonatal pain was established and orientin was administered for 6 days. The mechanical and thermal pain thresholds were assessed in neonates and adult mice. A Morris water maze was employed to investigate cognitive impairment in adult mice.

Results

A total of 286 proteins that were both predicted targets of orientin and involved in neonatal pain were identified. The hub proteins were SRC, HSP90AA1, MAPK1, RHOA, EGFR, AKT1, PTPN11, ESR1, RXRA, and HRAS. GO analysis indicated that the primary biological process (BP), molecular function (MF), and cellular component (CC) were protein phosphorylation, protein kinase activity, and vesicle lumen, respectively. KEGG analysis revealed that the mitogen-activated protein kinase (MAPK) signaling pathway may be the key to the mechanism of action. Molecular docking analysis showed the high binding affinities of orientin for MAPK1, MAPK8, and MAPK14. In mice, orientin inhibited the hyperalgesia in the pain threshold tests in neonates and adult mice and cognitive impairment in adult mice. Immunofluorescence showed that phosphorylated MAPK1 (p-ERK) protein levels in the hippocampus and spinal dorsal horn were downregulated by orientin.

Conclusion

The findings suggested that orientin alleviates neonatal pain, and the MAPK signaling pathway is involved.

Parasympathetic evaluation for procedural pain assessment in neonatology

INTRODUCTION

The Newborn Infant Parasympathetic Evaluation (NIPE) index is an instrument that enables continuous, fast and objective assessment of neonatal discomfort. The aim of the study was to analyse changes in NIPE values after performance of blood draws and the factors involved in this variation.

MATERIAL AND METHODS

We conducted a prospective observational study. We included infants admitted to the neonatal intensive care unit between June and December 2021 who underwent blood draws. We recorded demographic data, aspects related to the procedure, the NIPE index and the heart rate at baseline and 1, 2, 3, 4, 5, 10 and 15 min after the procedure.

RESULTS

The study included 86 records for 49 patients. In the first 4 min after the procedure, there was a significant decrease in the NIPE index, with a maximum decrease of 22.8% relative to baseline and the nadir at 2.79 min. The decrease in NIPE values was greater in infants born preterm, male, with lower 5-min Apgar scores and following procedures that had been performed previously, after caesarean section or in the morning. There were no differences when the blood draw was obtained during kangaroo care. The correlation between the NIPE index and the heart rate was weak.

CONCLUSIONS

After a painful procedure, such as a blood draw, the NIPE monitor showed a significant decrease in the first 4 min, which was more pronounced in preterm infants, in repeated procedures or after caesarean delivery. The NIPE index could help identify infants experiencing acute procedural pain, complementing clinical rating scales.

Neurodevelopmental outcomes after neonatal surgery

Children who require surgery in the newborn period are at risk for long-term neurodevelopmental impairment (NDI). There is growing evidence that surgery during this critical window of neurodevelopment gives rise to an increased risk of brain injury, predisposing to neurodevelopmental challenges including motor delays, learning disabilities, executive function impairments, and behavioral disorders. These impairments can have a significant impact on the quality of life of these children and their families. This review explores the current literature surrounding the effect of neonatal surgery on neurodevelopment, as well as the spectrum of proposed mechanisms that may impact neurodevelopmental outcomes. The goal is to identify modifiable risk factors and patients who may benefit from close neurodevelopmental follow-up and early referral to therapy.

Early life nociceptive stimulus and fentanyl exposure increase hippocampal neurogenesis and anxiety but do not affect spatial learning and memory

This study aimed to determine whether preemptive fentanyl administration in neonatal rats reduces the impact of a nociceptive stimulus initiated during the first day of life (P1) on hippocampal neurogenesis, behavior, and learning. At P1, Wistar rat pups received either a subcutaneous injection of fentanyl (F) before intraplantar injection of complete Freund’s adjuvant (CFA) (CFA + F group), an isolated injection of CFA (CFA group), or subcutaneous injection of fentanyl without CFA injection (F). Control animals received saline injections using the same route and volume as the treatment groups. Hippocampal neurogenesis was evaluated by 5′ –bromo-2′-deoxyuridine (BrdU) staining on P10 and P39 to assess neuronal proliferation and survival, respectively. Anxiety behavior in adulthood was assessed using an open field test (OF) and an elevated plus maze test (EPM). Spatial memory was assessed on a Morris water maze test (MWM), where the animals were trained for seven days, beginning on P81, and the probe trial was performed to evaluate memory retention. Although the CFA + F group showed an increased number of proliferative cells on P10, this finding did not persist on P39. The CFA + F group spent more time in the closed arms in the EPM, revealing more anxious behavior, although the early noxious experience, both with and without fentanyl, did not alter neurogenesis in adolescence and learning in adulthood. This study highlights that the impact of pain in early life pain combined with fentanyl on hippocampal neurogenesis on P10 did not persist on P39. In addition, this combined intervention during the first week of life was associated with higher anxiety levels.

Neonatal Morphine Results in Long-Lasting Alterations to the Gut Microbiome in Adolescence and Adulthood in a Murine Model

Despite the many advancements in the field of pain management, the use of intravenous opioids, such as morphine, in neonates is still a challenge for clinicians and researchers, as the available evidence concerning the long-term consequences of such an early exposure is limited. In particular, little is known concerning the long-term consequences of neonatal morphine exposure on the gut microbiome, which has been identified as a key modulator of health and diseases. Consequently, the purpose of this study was to investigate those long-term consequences of neonatal morphine on the gut microbiome. Newborn mice were exposed to either morphine (5 mg/kg/day) or saline for a duration of 7 ± 2 days. Fecal samples were collected during adolescence and adulthood to longitudinally assess the gut microbiome. DNA extracted from the stool samples were sent out for 16s rRNA sequencing. During adolescence, neonatal morphine resulted in a significant increase of α-diversity and an overall decrease in the abundance of several commensal genera. During adulthood, β-diversity revealed a significantly different microbial composition of the neonatally morphine-exposed mice than that of the controls. The results demonstrate that morphine exposure during this critical developmental period resulted in long-lasting changes, particularly a reduction in several commensal bacteria. Thus, an adjunct therapeutic intervention with probiotics could potentially be used along with opioids to manage pain while attenuating the long-term co-morbidities of neonatal morphine later in life.

Opioid analgesia and temperature regulation are associated with EEG background activity and MRI outcomes in neonates with mild-to-moderate hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia

BACKGROUND

Therapeutic hypothermia (TH) without sedation may lead to discomfort, which may be associated with adverse consequences in neonates with hypoxic-ischemic encephalopathy (HIE). The aim of this study was to assess the association between level of exposure to opioids and temperature, with electroencephalography (EEG) background activity post-TH and magnetic resonance imaging (MRI) brain injury in neonates with HIE.

METHODS

Thirty-one neonates with mild-to-moderate HIE who underwent TH were identified. MRIs were reviewed for presence of brain injury. Quantitative EEG background features including EEG discontinuity index and spectral power densities were calculated during rewarming and post-rewarming periods. Dose of opioids administered during TH and temperatures were collected from the medical charts. Multivariable linear and logistic regression analyses were conducted to assess the associations between cumulative dose of opioids and temperature with EEG background and MRI while adjusting for markers of HIE severity.

RESULTS

Higher opioid doses (β = -0.21, p = 0.02) and reduced skin temperature (β = 0.14, p < 0.01) were associated with lower EEG discontinuity index recorded post-TH. Higher opioid doses (β = 0.75, p = 0.01) and reduced skin temperature (β = -0.39, p = 0.02) were also associated with higher EEG Delta power post-TH. MRI brain injury was observed in 14 patients (45%). In adjusted regression analyses, higher opioid doses (OR = 0.00; 95%CI: 0-0.19; p = 0.01), reduced skin temperature (OR = 41.19; 95%CI: 2.27-747.86; p = 0.01) and reduced cooling device output temperature (OR = 1.91; 95%CI: 1.05-3.48; p = 0.04) showed an association with lower odds of brain injury.

CONCLUSIONS

Higher level of exposure to opioids and reduced skin temperature during TH in mild-to-moderate HIE were associated with improved EEG background activity post-TH. Moreover, higher exposure to opioids, reduced skin temperature and reduced device output temperature were associated with lower odds of brain injury on MRI.

The consequences of neonatal pain, stress and opiate administration in animal models: An extensive meta-analysis concerning neuronal cell death, motor and behavioral outcomes

This systematic review and meta-analysis aimed to investigate the association of neonatal exposure to pain, stress, opiate administration alone, as well as opiate administration prior to a painful procedure on neuronal cell death, motor, and behavioral outcomes in rodents. In total, 36 studies investigating the effect of pain (n = 18), stress (n = 15), opiate administration (n = 13), as well as opiate administration prior to a painful event (n = 7) in rodents were included in our meta-analysis. The results showed a large effect of pain (g = 1.37, 95% CI 1.00-1.74, p < .001) on neuronal cell death. Moreover, higher number of neonatal pain events were significantly associated with increased neuronal cell death, increased anxiety (b = -1.18, SE = 0.43, p = .006), and depressant-like behavior (b = 1.74, SE = 0.51, p = .027) in rodents. Both opiates and pain had no impact on motor function (g = 0.26, 95% CI 0.18-0.70, p = .248).

Sexual Dimorphism in the Effect of Neonatal Inflammatory Pain on Stress Reactivity of Hormonal Response and Cognitive Functions in Adult Rats

The effect of moderate neonatal stress induced by inflammatory pain in rat pups of both sexes on the hormonal response and cognitive processes in adult animals was studied in the Morris water maze. No significant differences in spatial learning and memory were found in experimental rats exposed to neonatal inflammatory pain vs. control animals. However, experimental rats exhibited sex differences in long-term spatial memory whose efficiency was higher in males vs. females. After long-term memory testing, stress responsiveness of the hypothalamic-pituitary-adrenocortical axis, as assessed by the plasma corticosterone level in the formalin test, was higher in experimental males vs. females. Only experimental females exhibited differences between short-term and long-term memory, with the efficiency being higher in the former. Thus, sexual dimorphism was found in the effect of neonatal nociceptive stress on long-term spatial memory in adult rats: experimental males vs. females demonstrated more effective long-term memory combined with a higher stress reactivity of the hormonal response.

Neuroscience meets nurture: challenges of prematurity and the critical role of family-centred and developmental care as a key part of the neuroprotection care bundle

Advances in neonatal-perinatal medicine have resulted in increased survival at lower gestations. Although the incidence of germinal matrix haemorrhage-intraventricular haemorrhage and cystic periventricular leucomalacia is reducing, a new phenotype of preterm brain injury has emerged consisting of a combination of destructive and dysmaturational effects. Consequently, severe neurological disability is reported at a lower rate than previously, but the overall morbidity associated with premature birth continues to present a large global burden and contributes significantly to increased financial costs to health systems and families. In this review, we examine the developmental milestones of fetal brain development and how preterm birth can disrupt this trajectory. We review common morbidities associated with premature birth today. Although drug-based and cell-based neuroprotective therapies for the preterm brain are under intense study, we outline basic, sustainable and effective non-medical, family-centred and developmental care strategies which have the potential to improve neurodevelopmental outcomes for this population and need to be considered part of the future neuroprotection care bundle.

Understanding early-life pain and its effects on adult human and animal emotionality: Translational lessons from rodent and zebrafish models

Critical for organismal survival, pain evokes strong physiological and behavioral responses in various sentient species. Clinical and preclinical (animal) studies markedly increase our understanding of biological consequences of developmental (early-life) adversity, as well as acute and chronic pain. However, the long-term effects of early-life pain exposure on human and animal emotional responses remain poorly understood. Here, we discuss experimental models of nociception in rodents and zebrafish, and summarize mounting evidence of the role of early-life pain in shaping emotional traits later in life. We also call for further development of animal models to probe the impact of early-life pain exposure on behavioral traits, brain disorders and novel therapeutic treatments.

Pain management for necrotizing enterocolitis: getting the balance right

BACKGROUND

Adequate pain management for preterm born neonates suffering from the extremely painful disease necrotizing enterocolitis (NEC) is essential, since neonatal exposure to pain is related to negative short-term and long-term consequences. The aim of this study was to describe the current pain management and its effectiveness in NEC patients.

METHODS

In this single-center, retrospective study, neonates (gestational age < 32 weeks and/or birth weight < 1500 g) with NEC Bell's stage II or III were included. Information on pain (based on COMFORTneo and NRS scores) and analgesic therapy was collected and analyzed for the acute disease period.

RESULTS

Of 79 patients included, 74 (94%) received intravenous analgesic therapy: most commonly morphine, fentanyl, and acetaminophen. The median COMFORTneo score was 11 (IQR 10-11), however, 49 patients had at least one COMFORTneo score ≥ 14 indicating pain. Nineteen patients had persistent high pain scores ≥ 14 with a median duration of 7.2 h (IQR 2.8-14.0).

CONCLUSIONS

This study showed that despite analgesic therapy, most NEC patients showed signs of pain, and in some, pain persisted for several hours. It suggests that current analgesic therapy frequently failed to prevent pain and existing pain was often insufficiently treated. This supports the urgent need for individualized pain management guidelines for NEC patients.

IMPACT

This study is unique in reporting on pain management in neonates suffering from necrotizing enterocolitis (NEC) during the full acute disease period. Despite analgesic therapy, the majority of NEC patients experience pain, and in some patients, pain persists for several hours. These findings highlight the need for improvement of neonatal pain management in NEC patients, including better pain monitoring and guidelines for individualized analgesic therapy. Improved pain management guidelines may help to prevent short-term and long-term consequences of neonatal exposure to pain, as well as excessive exposure to opioids.

Neonatal Pain, Opioid, and Anesthetic Exposure; What Remains in the Human Brain After the Wheels of Time?

OBJECTIVE

To evaluate possible negative long-term effects of neonatal exposure to pain, opioids and anesthetics in children and adolescents.

STUDY DESIGN

We studied five unique groups of children recruited from well-documented neonatal cohorts with a history of neonatal exposure to pain, opioids or anesthetics at different points along the continuum from no pain to intense pain and from no opioid exposure to very high opioid exposure in the presence or absence of anesthetics. We evaluated children who underwent major surgery (group 1 and 2), extracorporeal membrane oxygenation (group 3), preterm birth (group 4) and prenatal opioid exposure (group 5) in comparison to healthy controls. Neuropsychological functioning, thermal detection and pain thresholds and high-resolution structural and task-based functional magnetic resonance imaging during pain were assessed. In total 94 cases were included and compared to their own control groups.

RESULTS

Children and adolescents in groups 3 and 5 showed worse neuropsychological functioning after high opioid exposure. A thicker cortex was found in group 1 (pain, opioid and anesthetic exposure) in only the left rostral-middle-frontal-cortex compared to controls. We found no differences in other brain volumes, pain thresholds or brain activity during pain in pain related brain regions between the other groups and their controls.

CONCLUSIONS

No major effects of neonatal pain, opioid or anesthetic exposure were observed in humans 8-19 years after exposure in early life, apart from neuropsychological effects in the groups with the highest opioid exposure that warrants further investigation. Studies with larger sample sizes are needed to confirm our findings and test for less pronounced differences between exposed and unexposed children.

Available Instruments to Assess Pain in Infants

Pain assessment in newborns and infants is challenging for clinicians. Although behavioral and behavioral-physiological scales are validated pain assessment instruments, their use in this age group has significant limitations. In this review, we summarize the methods currently available for assessing pain in neonates and infants. It is possible that these pain detection methods are also useful for assessing the quality of anesthesia and analgosedation in these populations. Further research should be aimed at confirming the usefulness of these tools in infants and identifying additional pain assessment options for clinical practice.

The Long-Term Effects of Neonatal Inflammatory Pain on Cognitive Function and Stress Hormones Depend on the Heterogeneity of the Adolescent Period of Development in Male and Female Rats

Exposure to stress at an early age programs the HPA axis which can lead to cognitive deficits in adults. However, it is not known whether these deficits emerge in adulthood or are expressed earlier in life. The aims of the study were to investigate (1) the immediate effects of early injury-induced stress in one-day-old (P1) and repeated stress on at P1 and P2 rat pups on plasma corticosterone levels; and (2) examine the subsequent long-term effects of this early stress on spatial learning and memory, and stress reactivity in early P26-34 and late P45-53 adolescent male and female rats. Intra-plantar injection of formalin induced prolonged and elevated levels of corticosterone in pups and impaired spatial learning and short- and long-term memory in late adolescent males and long-term memory in early adolescent females. There were sex differences in late adolescence in both learning and short-term memory. Performance on the long-term memory task was better than that on the short-term memory task for all early adolescent male and female control and stressed animals. Short-term memory was better in the late age control rats of both sexes and for formalin treated females as compared with the early age rats. These results are consistent with an impaired function of structures involved in memory (the hippocampus, amygdala, prefrontal cortex) after newborn pain. However, activation of the HPA axis by neonatal pain did not directly correlate with spatial learning and memory outcomes and the consequences of neonatal pain remain are likely multi-determined.

Methadone effectively attenuates acute and long-term consequences of neonatal repetitive procedural pain in a rat model

BACKGROUND

Painful procedures in early life cause acute pain and can alter pain processing at a spinal level lasting into adulthood. Current methods of analgesia seem unable to prevent both acute and long-term hypersensitivity associated with neonatal pain. The current study aims to prevent acute and long-term hypersensitivity associated with neonatal procedural pain using methadone analgesia in rat pups.

METHODS

Sprague-Dawley rat pups received either methadone (1 mg/kg) or saline prior to repetitive needle pricks into the left hind paw from the day of birth (postnatal day (P)0) to P7. Control littermates received a tactile stimulus. Mechanical sensitivity was assessed during the neonatal period (P0-P7), from weaning to adulthood (3-7 weeks) and following surgical re-injury of the same dermatome in adulthood.

RESULTS

Methadone administration completely reversed acute hypersensitivity from P0 to P7. In addition, neonatal methadone analgesia prevented prolonged hypersensitivity after re-injury in adulthood, without affecting sensitivity from weaning to adulthood.

CONCLUSIONS

The current study shows that neonatal methadone analgesia can attenuate acute as well as long-term hypersensitivity associated with neonatal procedural pain in a rat model.

IMPACT

Methadone treatment attenuates acute and long-term hypersensitivity associated with neonatal pain in a rat model. Clinical effectiveness studies are urgently warranted to assess acute and long-term analgesic effectivity of methadone.

Maternal and iatrogenic neonatal opioid withdrawal syndrome: Differences and similarities in recognition, management, and consequences

Opioids are potent analgesics used to manage pain in both young and old, but the increased use in the pregnant population has significant individual and societal implications. Infants dependent on opioids, either through maternal or iatrogenic exposure, undergo neonatal opioid withdrawal syndrome (NOWS), where they may experience withdrawal symptoms ranging from mild to severe. We present a detailed and original review of NOWS caused by maternal opioid exposure (mNOWS) and iatrogenic opioid intake (iNOWS). While these two entities have been assessed entirely separately, recognition and treatment of the clinical manifestations of NOWS overlap. Neonatal risk factors such as age, genetic predisposition, drug type, and clinical factors like type of opioid, cumulative dose of opioid exposure, and disease status affect the incidence of both mNOWS and iNOWS, as well as their severity. Recognition of withdrawal is dependent on clinical assessment of symptoms, and the use of clinical assessment tools designed to determine the need for pharmacotherapy. Treatment of NOWS relies on a combination of non-pharmacological therapies and pharmacological options. Long-term consequences of opioids and NOWS continue to generate controversy, with some evidence of anatomic brain changes, but conflicting animal and human clinical evidence of significant cognitive or behavioral impacts on school-age children. We highlight the current knowledge on clinically relevant recognition, treatment, and consequences of NOWS, and identify new advances in clinical management of the neonate. This review brings a unique clinical perspective and critically analyzes gaps between the clinical problem and our preclinical understanding of NOWS.

Antinociceptive effect of vapocoolant medium stream spray on hotplate latency in rat pups

BACKGROUND

Heel sticks account for most blood tests performed in neonates without analgesia because topical local anesthetics are ineffective on heel glabrous skin. We investigated the antinociceptive effect of an alternative topical analgesic, a vapocoolant spray, on hind paw glabrous skin of rat pups. The spray was applied by two methods: method 1 for 4 s at a distance of 8 cm and method 2 for 10 s at a distance of 18 cm.

METHODS

The rat pups were randomized to either method 1 (n = 32) or method 2 (n = 31). Vapocoolant spray was applied to one hind paw randomly, and saline spray was applied to the contralateral paw. The paws were exposed to a hotplate test to measure withdrawal latency time before and 30 s after the spray applications. Additionally, rat pups were tested for tissue toxicity in method 1 (n = 20) and method 2 (n = 20) after application of the vapocoolant spray before heel sticks three times a day for two consecutive days. Analyses of spray and method effects on hotplate withdrawal latency time were determined by nonparametric Wilcoxon tests to assess paired difference between vapocoolant spray and saline spray and to compare difference in medians between the two methods.

RESULTS

Method 1 and method 2 vapocoolant spray applications significantly prolonged the withdrawal latency time compared with saline, a median difference of 0.6 s (IQR 0.1-1.2) for method 1 and 9.5 s (IQR 5.5-10.7) for method 2 (a 15-fold longer latency time with method 2). Method-2 produced significantly longer withdrawal latency time than method 1 with a difference in median time of 8.9 s (CI: 95% 7.3-10.4 s, P < .0001). No histopathological changes were detected.

CONCLUSIONS

Compared with method- 1, the vapocoolant spray in method 2 produced significantly longer withdrawal latency time that is clinically applicable to collecting blood samples after a heel stick.

Can Event-Related Potentials Evoked by Heel Lance Assess Pain Processing in Neonates? A Systematic Review

To clarify the possibility of event-related potential (ERP) evoked by heel lance in neonates as an index of pain assessment, knowledge acquired by and problems of the methods used in studies on ERP evoked by heel lance in neonates were systematically reviewed, including knowledge about Aδ and C fibers responding to noxious stimuli and Aβ fibers responding to non-noxious stimuli. Of the 863 reports searched, 19 were selected for the final analysis. The following points were identified as problems for ERP evoked by heel lance in neonates to serve as a pain assessment index: (1) It is possible that the ERP evoked by heel lance reflected the activation of Aβ fibers responding to non-noxious stimuli and not the activation of Aδ or C fibers responding to noxious stimulation; (2) Sample size calculation was presented in few studies, and the number of stimulation trials to obtain an averaged ERP was small. Accordingly, to establish ERP evoked by heel lance as a pain assessment in neonates, it is necessary to perform a study to clarify ERP evoked by Aδ- and C-fiber stimulations accompanied by heel lance in neonates.

Morphine use in the neonatal period and later neuropsychological development: a systematic review

AIM

To identify and evaluate the evidence documenting the association between neonatal morphine and later childhood neuropsychological development.

METHOD

We conducted a systematic literature search of eight electronic databases from inception until June 2019. We included all randomized controlled trials (RCTs) and cohort studies recruiting neonates who received morphine treatment, and measuring neuropsychological development outcomes with a minimum follow-up of 6 months.

RESULTS

Twelve separate reports from three RCTs and five cohort studies met our inclusion criteria. Owing to the small number of the included trials and the variable study designs, a meta-analysis was not performed. The findings from this review indicated that neonatal morphine use had no adverse effects on behaviour, cognition, motor, and executive function development at 8 to 9 years and earlier; except for the inconsistent conclusions on internalizing behavioural problems at 5 to 7 years and cognitive and motor developments at 18 months.

INTERPRETATION

Why a child needs morphine may have a more profound impact on later neuropsychological development than morphine itself. The small number, high heterogeneity, and limitations of the included studies limit confidence in the result of this systematic review.

Cerebral hemodynamic response to a therapeutic bed for procedural pain management in preterm infants in the NICU: a randomized controlled trial

INTRODUCTION

We developed a novel device, Calmer, that mimics key components of skin-to-skin holding to reduce stress in preterm infants. Our feasibility trial showed that Calmer worked 50% better than no treatment and no differently from our standard of care, facilitated tucking (FT), for reducing pain scores during a heel lance in preterm infants in the neonatal intensive care unit.

OBJECTIVE

We compared the effects of Calmer on regional cerebral hemodynamic activity during a noxious stimulation to FT.

METHODS

During a clinically required heel lance, we measured frontal cortex tissue oxygenation in a subsample of 29 preterm infants (27-33 weeks gestational age) from our larger randomized controlled trial. Infants were randomized to either FT (n = 16) or Calmer treatment (n = 12). The outcome measure, obtained using near-infrared spectroscopy, was a change in the tissue oxygenation index (TSI) across study phases (Baseline, Heel Lance, Recovery; median duration 517 seconds [421-906 seconds]).

RESULTS

No statistically significant differences were found between groups in the median TSI during any of the study phases. In response to the heel lance, 7 infants (27.6%) had a TSI that dipped below the 60% threshold (3 in the Calmer group 25% and 4 in the FT group 25%); none below 50%.

CONCLUSIONS

Infants on Calmer maintained normal regional cerebral oxygen levels (55%-85%) no differently from infants receiving a human touch intervention during blood collection. Parental skin-to-skin holding is one of the most effective strategies to relieve procedural pain in preterm infants. When parents or FT are not available, Calmer shows potential for filling this gap in care.

Cumulative procedural pain and brain development in very preterm infants: A systematic review of clinical and preclinical studies

Very preterm infants may manifest neurodevelopmental impairments, even in the absence of brain lesions. Pathogenesis is complex and multifactorial. Evidence suggests a role of early adversities on neurodevelopmental outcomes, via epigenetic regulation and changes in brain architecture. In this context, we focused on cumulative pain exposure which preterm neonates experience in neonatal intensive care unit (NICU). We systematically searched for: i) evidence linking pain with brain development and exploring the potential pathogenetic role of epigenetics; ii) preclinical research supporting clinical observational studies. Nine clinical neuroimaging studies, during neonatal or school age, mostly from the same research group, revealed volume reduction of white and gray matter structures in association with postnatal pain exposure. Three controlled animal studies mimicking NICU settings found increased cell death or apoptosis; nevertheless, eligible groups were limited in size. Epigenetic modulation (SLC6A4 promoter methylation) was identified in only two clinical trials. We call for additional research and, although knowledge gaps, we also point out the urgent need of minimizing painful procedures in NICUs.

Neonatal pain and reduced maternal care alter adult behavior and hypothalamic-pituitary-adrenal axis reactivity in a sex-specific manner

Preterm infants often spend a significant amount of time in the neonatal intensive care unit (NICU) where they are exposed to many stressors including pain and reduced maternal care. These early-life stressful experiences can have negative consequences on brain maturation during the neonatal period; however, less is known about the long-term cognitive and affective outcomes. Thus, this study was conducted to investigate the impact of neonatal pain and reduced maternal care on adult behavior and HPA axis reactivity in an animal model. Male and female rats underwent a series of repetitive needle pokes and/or reduced maternal care (through a novel tea ball infuser encapsulation method) during the first 4 days of life and were then assessed in a battery of behavioral tests as adults. We found that early-life pain enhanced spatial learning independent of the animal's sex, but altered HPA recovery from an acute stressor in females only. Moreover, reduced maternal care altered long-term spatial memory and reversal learning in males. These findings indicate that neonatal stressors have unique sex-dependent long-term biobehavioral effects in rodents. Continued examination of the behavioral consequences of these stressors may help explain varying vulnerability and resiliency in preterm infants who experienced early stress in the NICU.

Atypical neuromagnetic resting activity associated with thalamic volume and cognitive outcome in very preterm children

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Preterm birth is associated with higher risk of negative neurocognitive outcomes.

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At school age, preterm children have atypical frequency-specific power at rest.

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Thalamic volume reduction is associated with atypical power in preterm birth.

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Thalamic matter intensity is associated with negative neurocognitive outcomes.

Children born very preterm, even in the absence of overt brain injury or major impairment, are at increased risk of cognitive difficulties. This risk is associated with developmental disruptions of the thalamocortical system during critical periods while in the neonatal intensive care unit. The thalamus is an important structure that not only relays sensory information but acts as a hub for integration of cortical activity which regulates cortical power across a range of frequencies. In this study, we investigate the association between atypical power at rest in children born very preterm at school age using magnetoencephalography (MEG), neurocognitive function and structural alterations related to the thalamus using MRI. Our results indicate that children born extremely preterm have higher power at slow frequencies (delta and theta) and lower power at faster frequencies (alpha and beta), compared to controls born full-term. A similar pattern of spectral power was found to be associated with poorer neurocognitive outcomes, as well as with normalized T1 intensity and the volume of the thalamus. Overall, this study provides evidence regarding relations between structural alterations related to very preterm birth, atypical oscillatory power at rest and neurocognitive difficulties at school-age children born very preterm.

Early Neonatal Pain-A Review of Clinical and Experimental Implications on Painful Conditions Later in Life

Modern health care has brought our society innumerable benefits but has also introduced the experience of pain very early in life. For example, it is now routine care for newborns to receive various injections or have blood drawn within 24 h of life. For infants who are sick or premature, the pain experiences inherent in the required medical care are frequent and often severe, with neonates requiring intensive care admission encountering approximately fourteen painful procedures daily in the hospital. Given that much of the world has seen a steady increase in preterm births for the last several decades, an ever-growing number of babies experience multiple painful events before even leaving the hospital. These noxious events occur during a critical period of neurodevelopment when the nervous system is very vulnerable due to immaturity and neuroplasticity. Here, we provide a narrative review of the literature pertaining to the idea that early life pain has significant long-term effects on neurosensory, cognition, behavior, pain processing, and health outcomes that persist into childhood and even adulthood. We refer to clinical and pre-clinical studies investigating how early life pain impacts acute pain later in life, focusing on animal model correlates that have been used to better understand this relationship. Current knowledge around the proposed underlying mechanisms responsible for the long-lasting consequences of neonatal pain, its neurobiological and behavioral effects, and its influence on later pain states are discussed. We conclude by highlighting that another important consequence of early life pain may be the impact it has on later chronic pain states-an area of research that has received little attention.

Exposure to Morphine and Caffeine Induces Apoptosis and Mitochondrial Dysfunction in a Neonatal Rat Brain

Background: Preterm infants experience rapid brain growth during early post-natal life making them vulnerable to drugs acting on central nervous system. Morphine is administered to premature neonates for pain control and caffeine for apnea of prematurity. Simultaneous use of morphine and caffeine is common in the neonatal intensive care unit. Prior studies have shown acute neurotoxicity with this combination, however, little information is available on the mechanisms mediating the neurotoxic effects. The objective of this study was to determine the effects of morphine and caffeine, independently and in combination on mitochondrial dysfunction (Drp1 and Mfn2), neural apoptosis (Bcl-2, Bax, and cell damage) and endothelin (ET) receptors (ET_A and ET_B) in neonatal rat brain. Methods: Male and female rat pups were grouped separately and were divided into four different subgroups on the basis of treatments-saline (Control), morphine (MOR), caffeine (CAFF), and morphine + caffeine (M+C) treatment. Pups in MOR group were injected with 2 mg/kg morphine, CAFF group received 100 mg/kg caffeine, and M+C group received both morphine (2 mg/kg) and caffeine (100 mg/kg), subcutaneously on postnatal days (PND) 3-6. Pups were euthanized at PND 7, 14, or 28. Brains were isolated and analyzed for mitochondrial dysfunction, apoptosis markers, cell damage, and ET receptor expression via immunofluorescence and western blot analyses. Results: M+C showed a significantly higher expression of Bax compared to CAFF or MOR alone at PND 7, 14, 28 in female pups (p < 0.05) and at PND 7, 14 in male pups (p < 0.05). Significantly (p < 0.05) increased expression of Drp1, Bax, and suppressed expression of Mfn2, Bcl-2 at PND 7, 14, 28 in all the treatment groups compared to the control was observed in both genders. No significant difference in the expression of ET_A and ET_B receptors in male or female pups was seen at PND 7, 14, and 28. Conclusion: Concurrent use of morphine and caffeine during the first week of life increases apoptosis and cell damage in the developing brain compared to individual use of caffeine and morphine.

Epidural and Spinal Anesthesia for Newborn Surgery

Neuraxial (spinal and epidural) anesthesia has become commonplace in the care of neonates undergoing surgical procedures. These techniques afford many benefits, and, when properly performed, are extremely safe. This article reviews the benefits, risks, and applications of neuraxial anesthesia in neonates.

Analgesics and Sedatives in Critically Ill Newborns and Infants: The Impact on Long-Term Neurodevelopment

Inadequate pain and/or stress management in preterm- and term-born infants has been associated with increased morbidity and even mortality. However, exposure to analgosedatives during early infancy may also be one of the risk factors for subsequent neurodevelopmental impairment, at least in animal studies. Because infants admitted to neonatal or pediatric intensive care units may receive high amounts of these drugs for prolonged periods of time and the majority of these infants nowadays survive to discharge, this is of major concern. A balanced approach that incorporates the assessment and quantification of both wanted effects as well as unwanted side effects is therefore needed. In this article, the optimal dose determination of commonly used analgosedative drugs as well as their potential long-term effects on the developing human brain and neuropsychological functioning are reviewed.

Developmental neurobiology as a guide for pharmacological management of pain in neonates

Pain in newborn children should be prevented due to negative short- and long-term consequences. A good understanding of the development of the nociceptive system in newborns is necessary to enable optimal pain assessment, and most importantly to treat and prevent pain adequately in neonates. So far, preclinical juvenile animal studies have led to a tremendous amount of information regarding the development of the nociceptive system. In addition, they have made clear that the developmental stage of the nociceptive system may influence the mechanism of action of different classes of analgesics. Age specific analgesic therapy, based on post-menstrual age, should therefore be considered by incorporating information on the developmental stages of the nociceptive system in combination with knowledge from pharmacokinetic and -dynamic studies in neonates.

Early and late anti nociceptive effects of sucrose on neonatal inflammatory pain in rats: Comparison to a non-steroidal anti-inflammatory drug

Management of neonatal pain is not only ethical but is also essential. Barriers to pain management in infants include lack of safe and effective medications and fear of adverse effects of conventional pain medications. Sweet solutions given intraorally have been shown to reduce pain behaviors and associated symptoms. Sucrose and other sweet solutions are being increasingly used at the NICUs and immunization clinics. Sucrose for mild invasive procedures is effective and safe for those procedures that need to be repeated multiple times during the day. Only few studies examine the efficacy of sucrose for the management of inflammatory pain during infancy. In this study, Complete Freund's Adjuvant (CFA) was used to induce inflammation in 5-day-old rat pups; CFA also produces inflammation that lasts for more than a day, thus can also be a model for chronic pain. Sucrose or ibuprofen was given to subset of pups shortly after CFA intraplantar injections. Thermal as well as mechanical pain sensitivity was assessed on subsequent days as well as during adolescence and early adulthood. Sucrose and ibuprofen were both effective in preventing hyperalgesia and allodynia produced by CFA. Interestingly, sucrose was even more effective than ibuprofen, and the analgesic effects continued further to adolescence and adult life of the rats. Thus, and according to the results of this study, sucrose seems to be just as effective for inflammatory pain as Ibuprofen. In addition, sucrose protects against later-in-life hypersensitivity consequences to neonatal pain.

Adverse Behavioral Changes in Adult Mice Following Neonatal Repeated Exposure to Pain and Sucrose

Sucrose is recommended for the treatment of pain during minor procedures in preterm infants in the neonatal intensive care unit (NICU) and is currently used worldwide as the standard of care. We recently reported that adult mice repetitively exposed to sucrose compared to water during the first week of life, irrespective of exposure to an intervention, had significantly smaller brain volumes in large white matter, cortical and subcortical structures (e.g., hippocampus, striatum, fimbria). These structures are important for stress regulation and memory formation. Here, we report the effects of repeated neonatal exposure to pain and sucrose on adult behavior in mice. Neonatal C57BL/6J mice (N = 160, 47% male) were randomly assigned to one of two treatments (sucrose, water) and one of three interventions (needle-prick, tactile, handling). Pups received 10 interventions daily from postnatal day 1 (P1) to P6. A single dose of 24% sucrose or water was given orally 2 min before each intervention. At adulthood (P60-85) mice underwent behavioral testing to assess spatial memory, anxiety, motor function, pain sensitivity, and sugar preference. We found that mice that had received sucrose and handling only, had poorer short-term memory in adulthood compared to water/handling controls (p < 0.05). When exposed to pain, mice treated with repetitive sucrose or water did not differ on memory performance (p = 0.1). A sugar preference test showed that adult mice that received sucrose before an intervention as pups consumed less sugar solution compared to controls or those that received water before pain (p < 0.05). There were no significant group differences in anxiety, motor, or pain sensitivity. In a mouse model that closely mimics NICU care, we show for the first time that memory in adulthood was poorer for mice exposed to pain during the first week of life, irrespective of sucrose treatment, suggesting that sucrose does not protect memory performance when administered for pain. In the absence of pain, early repetitive sucrose exposure induced poorer short-term memory, highlighting the importance of accurate pain assessment.

Paediatric Pain Medicine: Pain Differences, Recognition and Coping Acute Procedural Pain in Paediatric Emergency Room

Paediatric pain and its assessment and management are challenging for medical professionals, especially in an urgent care environment. Patients in a paediatric emergency room (PER) often undergo painful procedures which are an additional source of distress, anxiety, and pain. Paediatric procedural pain is often underestimated and neglected because of various myths, beliefs, and difficulties in its evaluation and treatment. However, it is very different from other origins of pain as it can be preventable. It is known that neonates and children can feel pain and that it has long-term effects that last through childhood into adulthood. There are a variety of pain assessment tools for children and they should be chosen according to the patient’s age, developmental stage, communication skills, and medical condition. Psychological factors such as PER environment, preprocedural preparation, and parental involvement should also be considered. There are proven methods to reduce a patient’s pain and anxiety during different procedures in PER. Distraction techniques such as music, videogames, virtual reality, or simple talk about movies, friends, or hobbies as well as cutaneous stimulation, vibration, cooling sprays, or devices are effective to alleviate procedural pain and anxiety. A choice of distraction technique should be individualized, selecting children who could benefit from nonpharmacological pain treatment methods or tools. Nonpharmacological pain management may reduce dosage of pain medication or exclude pharmacological pain management. Most nonpharmacological treatment methods are cheap, easily accessible, and safe to use on every child, so it should always be a first choice when planning a patient’s care. The aim of this review is to provide a summary of paediatric pain features, along with their physiology, assessment, management, and to highlight the importance and efficacy of nonpharmacological pain management in an urgent paediatric care setting.

Painful procedures can affect post-natal growth and neurodevelopment in preterm infants

AIM

This Italian study evaluated whether painful procedures during the first four weeks of life were related to subsequent weight gain, head circumference (HC) and neurodevelopmental outcomes in preterm infants, METHODS: We evaluated the number of invasive procedures that infants born at less than 32 weeks of gestational age (GA) underwent in the Neonatal Intensive Care Unit of Careggi Hospital, Florence, from January to December 2015. Weight and HC were recorded at birth, 36 weeks of PMA and six and 12 months of CA. Neurological outcomes were assessed at six and 12 months of CA using the Bayley Scales of Infant and Toddler Development - Third Edition.

RESULTS

We studied 83 preterm infants with a GA of 28 ± 2 weeks and birth weight of 1098 ± 340 g. A higher number of invasive painful procedures were related to a lower HC standard deviation score at 36 weeks of PMA and six and 12 months of CA and with lower cognitive scores at six months. At 12 months, the relationship only remained significant for infants born at less than 28 weeks (p < 0.001).

CONCLUSION

Invasive painful procedures affected regular HC growth and short-term cognitive scores in preterm infants in the first year of life.

Repeated exposure to sucrose for procedural pain in mouse pups leads to long-term widespread brain alterations

Oral sucrose is administered routinely to reduce pain of minor procedures in premature infants and is recommended as standard care in international guidelines. No human or animal studies on effects of early repeated sucrose exposure on long-term brain development have been done in the context of pain. We evaluated the effects of repeated neonatal sucrose treatment before an intervention on long-term brain structure in mouse pups. Neonatal C57Bl/6J mice (n = 109) were randomly assigned to one of 2 treatments (vehicle vs sucrose) and one of 3 interventions (handling, touch, or needle-prick). Mice received 10 interventions daily from postnatal day 1 to 6 (P1-6). A dose of vehicle or 24% sucrose was given orally 2 minutes before each intervention. At P85-95, brains were scanned using a multichannel 7.0 T MRI. Volumes of 159 independent brain regions were obtained. Early repetitive sucrose exposure in mice (after correcting for whole brain volume and multiple comparisons) lead to smaller white matter volumes in the corpus callosum, stria terminalis, and fimbria (P < 0.0001). Cortical and subcortical gray matter was also affected by sucrose with smaller volumes of hippocampus and cerebellum (P < 0.0001). These significant changes in adult brain were found irrespective of the type of intervention in the neonatal period. This study provides the first evidence of long-term adverse effects of repetitive sucrose exposure and raises concerns for the use of this standard pain management practice during a period of rapid brain development in very preterm infants.

Adult spinal opioid receptor μ1 expression after incision is altered by early life repetitive tactile and noxious procedures in rats

Clinical and experimental data suggests that noxious stimulation at critical stages of development results in long‐term changes on nociceptive processing in later life. Here, we use an established, well‐documented rat model of repetitive noxious procedures closely mimicking the clinical situation in the NICU. In order to understand molecular changes underlying the long‐term consequences of repetitive stimulation of the developing nociceptive system the present study aims to analyze the presence of the µ‐opioid‐receptor‐1 (OPRM1). Neonatal rats received either four needle pricks per day in the left hind‐paw from postnatal day 0–7 as a model of procedural pain in infancy. Control pups were handled in the same way but were instead tactile stimulated, or were left undisturbed. At the age of 8 weeks, all animals received an ipsilateral hind‐paw incision as a model for post‐operative pain, and mechanical sensitivity was tested at multiple time‐points. Before, and 1 or 5 days post‐incision, spinal cord tissue was collected for immunostaining of opioid receptor OPRM1. Semi‐quantitative immunocytochemical analysis of superficial laminae in lumbar spinal dorsal horn revealed that: (1) early life repetitive tactile or noxious procedures do not alter baseline levels of OPRM1 staining intensity and (2) early life repetitive tactile or noxious procedures lead to a decrease in OPRM1 staining intensity 5 days after incision in adulthood compared to undisturbed controls. We conclude that early life repetitive tactile or noxious procedures affect the intensity of OPRM1‐immunoreactivity in the lumbar superficial spinal cord dorsal horn after adulthood injury, without affecting baseline intensity. © 2018 The Authors. Developmental Neurobiology Published by Wiley Periodicals, Inc. Develop Neurobiol 78: 417–426, 2018

Microglia in health and pain: impact of noxious early life events

NEW FINDINGS

What is the topic of this review? This review discusses the origins and development of microglia, and how stress, pain or inflammation in early life disturbs microglial function during critical developmental periods, leading to altered pain sensitivity and/or increased risk of chronic pain in later life. What advances does it highlight? We highlight recent advances in understanding how disrupted microglial function impacts the developing nervous system and the consequences for pain processing and susceptibility for development of chronic pain in later life. The discovery of microglia is accredited to Pío del Río-Hortega, who recognized this 'third element' of CNS cells as being morphologically distinct from neurons and astrocytes. For decades after this finding, microglia were altogether ignored or relegated as simply being support cells. Emerging from virtual obscurity, microglia have now gained notoriety as immune cells that assume a leading role in the development, maintenance and protection of a healthy CNS. Pioneering studies have recently shed light on the origins of microglia, their role in the developing nervous system and the complex roles they play beyond the immune response. These studies reveal that altered microglial function can have a profoundly negative impact on the developing brain and may be a determinant in a range of neurodevelopmental disorders and neurodegenerative diseases. The realization that aberrant microglial function also critically underlies chronic pain, a debilitating disorder that afflicts over 1.5 billion people worldwide, was a major conceptual leap forward in the pain field. Adding to this advance is emerging evidence that early life noxious experiences can have a long-lasting impact on central pain processing and adult pain sensitivity. With microglia now coming of age, in this review we examine the association between adverse early life events, such as stress, injury or inflammation, and the influence of sex differences, on the role of microglia in pain physiology in adulthood.

Perinatal and neonatal use of sedation and analgesia

Optimal obstetric and neonatal care requires the provision of adequate analgesia for painful procedures. However, anesthetic and analgesic agents have the potential to adversely impact the developing fetal/neonatal brain. In this setting, clinicians must assess the risks and benefits of pharmacologic anesthesia and analgesia for specific indications in this population. General anesthesia is required for non-obstetric surgery and cesarean section in the absence of neuraxial anesthesia for the health of the mother and fetus. Although experimental data raise concerns, human data are reassuring and future research may focus on neuroprotective adjuncts in the setting of repeated or prolonged anesthetic exposures. Opioid analgesia is standard of care for preterm infants undergoing major procedures including invasive surgery and endotracheal intubation. The use of opioids for agitation resulting from mechanical ventilation is controversial, but prevalent. Randomized and retrospective studies detect short-term toxicity with inconclusive long-term impact, suggesting the need to explore alternative therapies.

Acupuncture in the neonatal intensive care unit-using ancient medicine to help today's babies: a review

Acupuncture has been used for thousands of years in Eastern medicine for a variety of conditions and illnesses, including pain. Neonatal intensive care, on the other hand, is a relatively new branch of medicine that has emerged as the pivotal influence in increasing survival of critically ill newborn infants only within the last 50 years. Unfortunately, pain is an inevitable part of treatment in a neonatal intensive care unit (NICU). The control and prevention of pain remains a major issue for clinicians despite recognition and understanding of the myriad of short- and long-term problems that are associated with both pain and its treatment within the NICU environment. In this review, we examine the potential role of acupuncture to decrease and treat pain in babies requiring neonatal intensive care and discuss future therapeutic and research implications for the use of this ancient therapy within the modern environment of the NICU.

Randomized Controlled Trial Comparing Different Single Doses of Intravenous Paracetamol for Placement of Peripherally Inserted Central Catheters in Preterm Infants

BACKGROUND

The availability of a safe and effective pharmacological therapy to reduce procedural pain in preterm infants is limited. The effective analgesic single dose of intravenous paracetamol in preterm infants is unknown. Comparative studies on efficacy of different paracetamol doses in preterm infants are lacking.

OBJECTIVES

To determine the analgesic effects of different single intravenous paracetamol doses on pain from peripherally inserted central catheter (PICC) placement in preterm infants.

METHODS

In a blinded randomized controlled trial, the analgesic effects of 10-, 15-, and 20-mg/kg single-dose intravenous paracetamol before PICC placement were compared in neonates with a gestational age <32 weeks. Secondly, a separate age-matched nonrandomized control group receiving oral sucrose was included. Pain was assessed with the Premature Infant Pain Profile (PIPP) and the COMFORTneo score. Peak plasma concentrations of paracetamol were determined.

RESULTS

A total of 60 patients were included in the paracetamol dose groups (median gestational age = 27.8, IQR: 25.7-29.2 weeks). PIPP scores were comparable: median = 8 (IQR: 6-10.5), 7 (IQR: 6-9), and 8 (IQR: 6-10) for the 10-, 15-, and 20-mg/kg paracetamol groups, respectively (p = 0.94). COMFORTneo scores were not statistically different between the different paracetamol dose groups (p = 0.35). All randomized subjects, except for 3 who received 10 mg/kg of paracetamol, had peak paracetamol concentrations >9 mg/L. PIPP (p = 0.78) and COMFORTneo (p = 0.08) scores were also comparable between paracetamol- and sucrose-treated patients.

CONCLUSIONS

We found no analgesic benefit from intravenous paracetamol studied in different single doses over sucrose for PICC placement in preterm infants. Paracetamol is not a suitable analgesic for this procedure in preterm infants.

Neonatal pain and reduced maternal care: Early-life stressors interacting to impact brain and behavioral development

Advances in neonatal intensive care units (NICUs) have drastically increased the survival chances of preterm infants. However, preterm infants are still exposed to a wide range of stressors during their stay in the NICU, which include painful procedures and reduced maternal contact. The activation of the hypothalamic-pituitary-adrenal (HPA) axis, in response to these stressors during this critical period of brain development, has been associated with many acute and long-term adverse biobehavioral outcomes. Recent research has shown that Kangaroo care, a non-pharmacological analgesic based on increased skin-to-skin contact between the neonate and the mother, negates the adverse outcomes associated with neonatal pain and reduced maternal care, however the biological mechanism remains widely unknown. This review summarizes findings from both human and rodent literature investigating neonatal pain and reduced maternal care independently, primarily focusing on the role of the HPA axis and biobehavioral outcomes. The physiological and positive outcomes of Kangaroo care will also be discussed in terms of how dampening of the HPA axis response to neonatal pain and increased maternal care may account for positive outcomes associated with Kangaroo care.

Smaller Cerebellar Growth and Poorer Neurodevelopmental Outcomes in Very Preterm Infants Exposed to Neonatal Morphine

OBJECTIVE

To examine the relationship between morphine exposure and growth of the cerebellum and cerebrum in very preterm neonates from early in life to term-equivalent age, as well as to examine morphine exposure and brain volumes in relation to neurodevelopmental outcomes at 18 months corrected age (CA).

STUDY DESIGN

A prospective cohort of 136 very preterm neonates (24-32 weeks gestational age) was serially scanned with magnetic resonance imaging near birth and at term-equivalent age for volumetric measurements of the cerebellum and cerebrum. Motor outcomes were assessed with the Peabody Developmental Motor Scales, Second Edition and cognitive outcomes with the Bayley Scales of Infant and Toddler Development, Third Edition at 18 months CA. Generalized least squares models and linear regression models were used to assess relationships between morphine exposure, brain volumes, and neurodevelopmental outcomes.

RESULTS

A 10-fold increase in morphine exposure was associated with a 5.5% decrease in cerebellar volume, after adjustment for multiple clinical confounders and total brain volume (P = .04). When infants exposed to glucocorticoids were excluded, the association of morphine was more pronounced, with an 8.1% decrease in cerebellar volume. Morphine exposure was not associated with cerebral volume (P = .30). Greater morphine exposure also predicted poorer motor (P < .001) and cognitive outcomes (P = .006) at 18 months CA, an association mediated, in part, by slower brain growth.

CONCLUSIONS

Morphine exposure in very preterm neonates is independently associated with impaired cerebellar growth in the neonatal period and poorer neurodevelopmental outcomes in early childhood. Alternatives to better manage pain in preterm neonates that optimize brain development and functional outcomes are urgently needed.

Neonatal paracetamol treatment reduces long-term nociceptive behaviour after neonatal procedural pain in rats

BACKGROUND

Pain from skin penetrating procedures (procedural pain) during infancy in the neonatal intensive care unit (NICU) may result in changes of nociceptive sensitivity in later life. This supports the need for pain management during such vulnerable periods in life. This study, therefore, analyses the short- and long-term consequences of neonatal paracetamol (acetaminophen) treatment on pain behaviour in an experimental rat model of neonatal procedural pain.

METHODS

A repetitive needle-prick model was used, in which neonatal rats received four needle pricks into the left hind paw per day from postnatal day 0 to day 7 (P0-P7). Paracetamol (50 mg/kg/day s.c.) was administered daily (P0-P7), and sensitivity to mechanical stimuli was compared with a needle-prick/saline-treated group and to a tactile control group. At 8 weeks of age, all animals underwent an ipsilateral paw-incision, modelling postoperative pain, and the duration of hypersensitivity was assessed.

RESULTS

Neonatal paracetamol administration had no effect upon short-term mechanical hypersensitivity during the first postnatal week or upon long-term baseline sensitivity from 3 to 8 weeks. However, neonatal paracetamol administration significantly reduced the postoperative mechanical hypersensitivity in young adults, caused by repetitive needle pricking.

CONCLUSION

Paracetamol administration during neonatal procedural pain does not alter short-term or long-term effects on mechanical sensitivity, but does reduce the duration of increased postoperative mechanical hypersensitivity in a clinically relevant neonatal procedural pain model.

WHAT DOES THIS STUDY ADD

Paracetamol can be used safely in neonatal rats. Neonatal paracetamol treatment had no effect upon short-term mechanical hypersensitivity during the first postnatal week, nor upon long-term baseline sensitivity from 3 to 8 weeks. Paracetamol treatment during the first postnatal week significantly reduced the postoperative mechanical hypersensitivity in young adult rats.

An examination of sex differences in the effects of early-life opiate and alcohol exposure

Early-life exposure to drugs and alcohol is one of the most preventable causes of developmental, behavioural and learning disorders in children. Thus a significant amount of basic, animal and human research has focused on understanding the behavioural consequences and the associated neural effects of exposure to drugs and alcohol during early brain development. Despite this, much of the previous research that has been done on this topic has used predominantly male subjects or rodents. While many of the findings from these male-specific studies may ultimately apply to females, the purpose of this review is to highlight the research that has also examined sex as a factor and found striking differences between the sexes in their response to early-life opiate and alcohol exposure. Finally, we will also provide a framework for scientists interested in examining sex as a factor in future experiments that specifically examine the consequences of early-life drug and alcohol exposure.

Exposure to Early Life Pain: Long Term Consequences and Contributing Mechanisms

From an evolutionary perspective, adaptations of an organism to its early environment are essential for survival. The occurrence of early life perturbation, coincident with increased developmental plasticity, provides a unique opportunity for such adaptations to become programmed and persist throughout life. However, adaptations that are beneficial to maintaining homeostasis in one's early environment may result in extreme response strategies that confer vulnerability or dysfunction later in life. This review summarizes recent findings in human and animal studies demonstrating that early life pain results in a hypo-/hyper-sensitive phenotype in response to acute and persistent pain and stress later in life. Changes in cognition and immune function in response to early life pain have also been observed. Recent data on the neural mechanisms underlying these long-term changes are discussed, as well as potential strategies to minimize the impact of early life pain.

Honokiol for the Treatment of Neonatal Pain and Prevention of Consequent Neurobehavioral Disorders

This study examined the short- and long-term neuroprotective and analgesic activity of honokiol (a naturally occurring lignan isolated from Magnolia) on developing brains in neonates exposed to inflammatory pain, known to cause neuronal cell death. Postnatal day 4 (P4) neonatal rat pups were subjected to intraplantar formalin injection to four paws as a model of severe neonatal pain. Intraperitoneal honokiol (10 mg/kg) or corn oil vehicle control was administered 1 h prior to formalin insult, and animals were maintained on honokiol through postnatal day 21 (P21). Behavioral tests for stress and pain were performed after the painful insult, followed by morphological examinations of the brain sections at P7 and P21. Honokiol significantly attenuated acute pain responses 30 min following formalin insult and decreased chronic thermal hyperalgesia later in life. Honokiol-treated rats performed better on tests of exploratory behavior and performed significantly better in tests of memory. Honokiol treatment normalized hippocampal and thalamic c-Fos and hippocampal alveus substance P receptor expression relative to controls at P21. Together, these findings support that (1) neonatal pain experiences predispose rats to the development of chronic behavioral changes and (2) honokiol prevents and reduces both acute and chronic pathological pain-induced deteriorations in neonatal rats.