The cortical response to a noxious procedure changes over time in preterm infants

Task-based functional neuroimaging in infants: a systematic review

Background

Infancy is characterized by rapid neurological transformations leading to consolidation of lifelong function capabilities. Studying the infant brain is crucial for understanding how these mechanisms develop during this sensitive period. We review the neuroimaging modalities used with infants in stimulus-induced activity paradigms specifically, for the unique opportunity the latter provide for assessment of brain function.

Methods

Conducted a systematic review of literature published between 1977-2021, via a comprehensive search of four major databases. Standardized appraisal tools and inclusion/exclusion criteria were set according to the PRISMA guidelines.

Results

Two-hundred and thirteen papers met the criteria of the review process. The results show clear evidence of overall cumulative growth in the number of infant functional neuroimaging studies, with electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) to be the most utilized and fastest growing modalities with behaving infants. However, there is a high level of exclusion rates associated with technical limitations, leading to limited motor control studies (about 6 % ) in this population.

Conclusion

Although the use of functional neuroimaging modalities with infants increases, there are impediments to effective adoption of existing technologies with this population. Developing new imaging modalities and experimental designs to monitor brain activity in awake and behaving infants is vital.

Cortical activation and oxygen perfusion in preterm newborns during kangaroo mother care: A pilot study

AIM

This study aimed to assess the functional activation of preterm newborns' cerebral cortex during kangaroo mother care. Possible effects of gestational age and previous kangaroo mother care experience were also considered.

METHODS

Fifteen preterm newborns were recruited (gestational age: 24-32 weeks). Cortical activation was assessed in frontal, motor and primary somatosensory cortices after 15 and 30 min of kangaroo mother care by multichannel near-infrared spectroscopy (gestational age at assessment: 30-36 weeks). Both oxy- and deoxy-haemoglobin variations were analysed by t-test. Possible effects of gestational age and previous kangaroo mother care experience on cortical activation were studied by regression analysis.

RESULTS

After 15 min, bilateral activations (oxy-haemoglobin increase) were observed in frontal, somatosensory and motor cortices. After 30 min, the right motor and primary somatosensory cortices were found activated. Deoxy-haemoglobin increased after 15 min, returning to baseline at 30 min. After 15 min, there was a positive effect of gestational age at the assessment on both haemoglobin concentrations and a negative effect of previous kangaroo mother care on deoxy-haemoglobin increase.

CONCLUSION

Motor and somatosensory cortices, particularly on the right side, showed significant activation during kangaroo mother care. Kangaroo mother care seems to benefit activated cortical areas by improving oxygen supply.

Empathy at birth: Mother's cortex synchronizes with that of her newborn in pain

Early neonatal relation with the caregiver is vital for newborn survival and for the promotion of an appropriate neural development. The aim of this study was to assess if the empathic cortical response of a mother to her baby's pain is synchronized with the neonatal cortical response to the painful stimulation. We used hyperscanning, a functional neuroimaging approach that allows studying functional synchronization between two brains. Sixteen mother-newborn dyads were recruited. Maternal and neonatal cortical activities were simultaneously monitored, by near-infrared spectroscopy, during a heel prick performed on the baby and observed by the mother. Multiple paired t test was used to identify cortical activation, and wavelet transform coherence method was used to explore possible synchronization between the maternal and neonatal cortical areas. Activations were observed in mother's parietal cortex, bilaterally, and in newborn's superior motor/somatosensory cortex. The main functional synchronization analysis showed that mother's left parietal cortex activity cross-correlated with that of her newborn's superior motor/somatosensory cortex. Such synchronization dynamically changed throughout assessment, becoming positively cross-correlated only after the leading role in synchronizing cortical activities was taken up by the newborn. Thus, maternal empathic cortical response to baby pain was guided by and synchronized to the newborn's cortical response to pain. We conclude that, in case of potential danger for the infant, brain areas involved in mother-newborn relationship appear to be already co-regulated at birth.

Measures of Stress Exposure for Hospitalized Preterm Infants

BACKGROUND

Extended hospitalization in neonatal intensive care units subjects preterm infants to multiple stress exposures that affect long-term cognitive functioning, motor development, and stress reactivity. Measurement of stress exposure is challenging with multiple measures of stress exposure in use, including counts of skin-breaking or invasive procedures or counts of noxious sensory exposures.

OBJECTIVES

The purpose of this analysis was to compare measures of stress exposure commonly used by researchers and to determine the predictive validity of these measures for early neurobehavior. We accomplished this objective through the following specific aims: (a) describe the stress exposures of preterm infants in the first 2 weeks of life, (b) determine the correlations among measures of stress exposure, and (c) compare the predictive validity of measures of stress exposure for early neurobehavior.

METHODS

Very preterm infants born between 28 and 31 weeks postmenstrual age were enrolled from four neonatal intensive care units in a large Midwest city. We measured stress exposure over the first 14 days of life for each infant as a count of skin-breaking procedures, a count of invasive procedures, and cumulative scores derived from the Neonatal Infant Stressor Scale. Neurobehavior was assessed at 35 weeks postmenstrual age using the motor development and vigor and alertness/orientation subscales from the Neurobehavioral Assessment of the Preterm Infant. We used Spearman's rho to determine correlations among the measures of stress exposure and multiple linear regression to determine the predictive validity of each stress exposure measure for neurobehavioral outcomes.

RESULTS

Seventy-one preterm infants were included in the analysis. We found marked variance across individuals in all measures of stress exposure. There were moderate-high correlations among the measures of stress exposure. No measure of stress exposure was associated with early neurobehavior.

DISCUSSION

The stress experiences of hospitalized preterm infants vary. This variance is reflected in all measures of stress exposure. Because measures of stress exposure are highly correlated, the most objective measure requiring the least interpretation should be used. However, the currently available measures of stress exposure used in this analysis may not reflect the infant's physiological stress responses and fail to associate with early neurobehavior.

Venipuncture activates the cerebral cortex in children with intellectual disability

OBJECTIVE

To evaluate the pattern of cortical activation during a painful procedure, such as a venipuncture, in children with intellectual disability and compare it with that of cognitively healthy children.

STUDY DESIGN AND SETTING

A cohort study was conducted and cortical activation was assessed by multichannel cerebral near-infrared spectroscopy to monitor variations in oxyhaemoglobin and deoxyhaemoglobin (Hbb) in children with and without intellectual disability during a venipuncture for blood sampling with topical anaesthesia. Pain and distress were assessed as well using different validated pain scales (visual analogue scale and Non-Communicating Children's Pain Checklist-Postoperative Version for children with intellectual disability), and compared between groups.

PARTICIPANTS

16 children with severe to profound intellectual disability and 20 cognitively healthy peers (age range: 4-17 years).

RESULTS

When Hbb was analysed, children with intellectual disability exhibited a bilateral activation of the somatosensory (p<0.006) and right motor cortex (p=0.0045), whereas cognitively healthy peers never showed a cortical activation. Children with intellectual disability also showed more pain than controls (p=0.001).

CONCLUSIONS

When subjected to a painful procedure, only children with intellectual disability show an activation of the cerebral cortex, even if topical anaesthesia is applied, and express more pain than cognitively healthy peers. The role of other issues in painful procedures, such as anxiety, fear or physical restraint, deserves further investigation.

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.

Protocol to Measure Hair Cortisol in Low Mass Samples From Very Preterm Infants

BACKGROUND

Hair cortisol is a measure of chronic or repeated hypothalamic-pituitary-adrenal axis activation in response to physical or psychological stressors. Hair cortisol has been successfully used as a measure of chronic stress in adults and children; however, its use as a valid measure in preterm infants has been limited by challenges in measuring cortisol in the low mass samples collectable from these infants.

OBJECTIVES

The purpose of this report is to present a novel protocol for the measurement of hair cortisol in very low mass hair samples.

METHODS

Small changes were made to previously published protocols. After washing and pulverizing the hair samples, a double methanol cortisol extraction was performed. Samples were spiked with a known quantity of cortisol and analyzed in duplicate using an enzyme-linked immunosorbent assay.

RESULTS

Hair cortisol was detectable in samples weighing between 0.4 and 10.9 mg. The mean cortisol level was 23.74 pg/mg hair (SD = 26.38).

DISCUSSION

With small changes to previously published laboratory protocols, cortisol is quantifiable in low mass hair samples from preterm infants. This technical advance is an important step toward quantifying the stress experiences of hospitalized preterm infants.

Conscious Processing and the Global Neuronal Workspace Hypothesis

We review the central tenets and neuroanatomical basis of the global neuronal workspace (GNW) hypothesis, which attempts to account for the main scientific observations regarding the elementary mechanisms of conscious processing in the human brain. The GNW hypothesis proposes that, in the conscious state, a non-linear network ignition associated with recurrent processing amplifies and sustains a neural representation, allowing the corresponding information to be globally accessed by local processors. We examine this hypothesis in light of recent data that contrast brain activity evoked by either conscious or non-conscious contents, as well as during conscious or non-conscious states, particularly general anesthesia. We also discuss the relationship between the intertwined concepts of conscious processing, attention, and working memory.

Effects of Neonatal Pain and Temperament on Attention Problems in Toddlers Born Preterm

Objective

To examine the effects of individual characteristics of neonates and neonatal pain-related stress on attention problems and externalizing behavior problems of toddlers born preterm, analyzing the moderating effects of the dispositional traits of temperament.

Methods

The sample included 62 toddlers aged 18-36 months and their mothers. The mothers were interviewed using the Child Behavior Checklist 1.5-5 for toddlers' attention and externalizing behavior problems assessment, the Early Childhood Behavior Questionnaire for toddlers' temperament assessment, and the Adult Temperament Questionnaire for their temperament assessment. The Neonatal Infant Stressor Scale analyzed the number of pain-related stress events during neonatal intensive care unit (NICU) hospitalization recorded in the medical charts. Statistical descriptive, correlation, and multiple linear regression analyses were performed.

Results

High neonatal pain-related stress total index, associated with toddler's temperament with less Effortful Control, and mother's temperament with high Surgency explained 23% variability of the attention problems. Otherwise, the externalizing behavior problems were explained by temperament, but not by neonatal pain-related stress.

Conclusions

The findings support the impact of neonatal pain experiences, and current toddlers' and mothers' temperament characterized by poorer self-regulation on attention problems in toddlers born preterm. Developmental care in the NICU and follow-up programs after discharge are recommended to promote regulated temperament of the mother-child dyads, aiming to prevent attentional problems in toddlers born preterm.

Infant Analgesia With a Combination of Breast Milk, Glucose, or Maternal Holding

OBJECTIVES

We studied neonatal cortical brain response to 4 types of nonpharmacological analgesia (oral glucose, expressed breast milk, maternal holding plus oral glucose, breastfeeding). We aimed to assess the differential effect of oral solutions (glucose, breast milk) given alone or combined with the maternal-infant relationship (holding, breastfeeding).

METHODS

Eighty healthy term newborns undergoing a heel stick were randomly assigned to 4 parallel groups of 20 infants each: group 1, infants received a glucose solution on a changing table; group 2, infants received expressed breast milk on a changing table; group 3, infants received a glucose solution in their mothers' arms; and group 4, infants were breastfed by their mothers. Cortical activation in parietal, temporal, and frontal cortices was assessed by multichannel near-infrared spectroscopy. Pain expression was also evaluated.

RESULTS

Oral glucose alone or combined with maternal holding was associated with no cortical activation during heel stick. Expressed breast milk was associated with localized bilateral activation of somatosensory and motor cortices (P < .01). Breastfeeding was associated with extensive bilateral activation of somatomotor, somatosensory, and right parietal cortices (P < .01). Pain expression was lower with the maternal-infant relationship (P = .007).

CONCLUSIONS

Oral glucose, either alone or combined with maternal holding, appears to block or weaken cortical pain processing. Breast milk alone is associated with localized cortical activation. Breastfeeding is associated with extensive activation and may act by extending cortical processing. Maternal relationship, both combined with oral glucose and in breastfeeding, shows the greatest analgesic effect, although the neural patterns involved are distributed differently.

Improving the treatment of infant pain

Purpose of review

Pain management presents a major challenge in neonatal care. Newborn infants who require medical treatment can undergo frequent invasive procedures during a critical period of neurodevelopment. However, adequate analgesic provision is infrequently and inconsistently provided for acute noxious procedures because of limited and conflicting evidence regarding analgesic efficacy and safety of most commonly used pharmacological agents. Here, we review recent advances in the measurement of infant pain and discuss clinical trials that assess the efficacy of pharmacological analgesia in infants.

Recent findings

Recently developed measures of noxious-evoked brain activity are sensitive to analgesic modulation, providing an objective quantitative outcome measure that can be used in clinical trials of analgesics.

Summary

Noxious stimulation evokes changes in activity across all levels of the infant nervous system, including reflex activity, altered brain activity and behaviour, and long-lasting changes in infant physiological stability. A multimodal approach is needed if we are to identify efficacious and well tolerated analgesic treatments. Well designed clinical trials are urgently required to improve analgesic provision in the infant population.

Long-term continuous monitoring of the preterm brain with diffuse optical tomography and electroencephalography: a technical note on cap manufacturing

Diffuse optical tomography (DOT) has recently proved useful for detecting whole-brain oxygenation changes in preterm and term newborns' brains. The data recording phase in prior explorations was limited up to a maximum of a couple of hours, a time dictated by the need to minimize skin damage caused by the protracted contact with optode holders and interference with concomitant clinical/nursing procedures. In an attempt to extend the data recording phase, we developed a new custom-made cap for multimodal DOT and electroencephalography acquisitions for the neonatal population. The cap was tested on a preterm neonate (28 weeks gestation) for a 7-day continuous monitoring period. The cap was well tolerated by the neonate, who did not suffer any evident discomfort and/or skin damage. Montage and data acquisition using our cap was operated by an attending nurse with no difficulty. DOT data quality was remarkable, with an average of 92% of reliable channels, characterized by the clear presence of the heartbeat in most of them.