Pain reactivity in preterm neonates: examining the sex differences

A developmental framework for understanding the influence of sex and gender on health: Pediatric pain as an exemplar

Sex differences are a robust finding in many areas of adult health, including cardiovascular disease, psychiatric disorders, and chronic pain. However, many sex differences are not consistently observed until after the onset of puberty. This has led to the hypothesis that hormones are primary contributors to sex differences in health outcomes, largely ignoring the relative contributions of early developmental influences, emerging psychosocial factors, gender, and the interaction between these variables. In this paper, we argue that a comprehensive understanding of sex and gender contributions to health outcomes should start as early as conception and take an iterative biopsychosocial-developmental perspective that considers intersecting social positions. We present a conceptual framework, informed by a review of the literature in basic, clinical, and social science that captures how critical developmental stages for both sex and gender can affect children's health and longer-term outcomes. The literature on pediatric chronic pain is used as a worked example of how the framework can be applied to understanding different chronic conditions.

Biomarkers for assessing pain and pain relief in the neonatal intensive care unit

Newborns admitted to the neonatal intensive care unit (NICU) regularly undergo painful procedures and may face various painful conditions such as postoperative pain. Optimal management of pain in these vulnerable preterm and term born neonates is crucial to ensure their comfort and prevent negative consequences of neonatal pain. This entails accurate and timely identification of pain, non-pharmacological pain treatment and if needed administration of analgesic therapy, evaluation of treatment effectiveness, and monitoring of adverse effects. Despite the widely recognized importance of pain management, pain assessment in neonates has thus far proven to be a challenge. As self-report, the gold standard for pain assessment, is not possible in neonates, other methods are needed. Several observational pain scales have been developed, but these often rely on snapshot and largely subjective observations and may fail to capture pain in certain conditions. Incorporation of biomarkers alongside observational pain scores holds promise in enhancing pain assessment and, by extension, optimizing pain treatment and neonatal outcomes. This review explores the possibilities of integrating biomarkers in pain assessment in the NICU.

Assessment of four pain scales for evaluating procedural pain in premature infants undergoing heel blood collection

BACKGROUND

Procedural pain is underestimated in hospitalized preterm infants. The aim of this study was to assess the reliability, validity, and clinical utility of the Neonatal Facial Coding System (NFCS), Douleur Aiguë du Nouveau-né (DAN) scale, Neonatal Infant Pain Scale (NIPS), and Premature Infant Pain Profile (PIPP) in premature infants undergoing heel blood collection. We assume that the four scales were similar in reliablility and validity (but different in clinical utility).

METHODS

The pain assessments were performed on 111 premature infants using the four scales. Internal consistency was determined by Cronbach's α, and the reliability was determined by the intraclass correlation coefficients. Concurrent validity was evaluated by Spearman's rank correlations. Bland-Altman plots were used to investigate the convergent validity.

RESULTS

The internal consistency and their reliability of the scales were high (p < 0.001). Scores were significantly higher at the time of blood collection (p < 0.001). Mean scores of clinical utility of PIPP were significantly higher than NFCS and DAN (p < 0.05) but not higher than the NIPS (p > 0.05).

CONCLUSIONS

The four scales were reliable and valid. This study suggests that the PIPP and NIPS has good clinical utility and are better choice for evaluating procedural pain in premature infants.

IMPACT

The aim of this study was to assess the reliability, validity, and clinical utility of NFCS, DAN, NIPS, and PIPP in premature infants undergoing heel blood collection. The results showed that the four scales have high reliability and internal consistency; the PIPP and NIPS have good clinical utility and are better choice for evaluating procedural pain in premature infants. Our study results provided a reference for clinical workers in choosing pain assessment scales and conduction intervention.

Adult brain activation in response to pain is changed by neonatal painful stimulation according to sex: A manganese-enhanced MRI study

Although it is known that nociceptive stimulation in the first postnatal week in rats is useful to model preterm pain, resulting in activation of specific brain areas, as assessed in vivo using manganese-enhanced magnetic resonance imaging (MEMRI), little is known about its long-term effects and sex specificity. Here we aimed to investigate whether inflammatory pain induced in male and female adult rats modify the pattern of brain activation between animals subjected or not to neonatal pain. For this, Complete Freund's adjuvant (CFA) was injected into the left hind paw of rat pups on postnatal day 1 (P1) or P8 to induce inflammatory response. During adulthood, CFA-treated and control animals were injected with CFA 1 hr prior MRI. MEMRI has the ability to enhance the contrast of selective brain structures in response to a specific stimulus, as the pain. MEMRI responses were consistent with activation of nociceptive pathways and these responses were reduced in animals treated with CFA on P1, but increased in animals treated on P8, mainly in the female group. In agreement, P8 female group showed exacerbated responses in the thermal nociceptive test. Using MEMRI, we conclude that the natural ability of adult rats to recognize and react to pain exposition is modified by neonatal painful exposition, mainly among females.

Cortical Pain Response of Newborn Infants to Venepuncture: A Randomized Controlled Trial Comparing Analgesic Effects of Sucrose Versus Breastfeeding

OBJECTIVE

Sucrose administration and breastfeeding decrease behavioral expressions of pain in neonates. However, recent studies indicated that there is a persistent cortical response with sucrose. This study compared the efficacy of sucrose administration versus breastfeeding to decrease cortical responses to pain during venepuncture.

PATIENTS AND METHODS

A randomized, prospective, controlled trial was conducted in a tertiary level maternity ward. Healthy, 3-day-old term neonates, undergoing venepuncture for neonatal screening, were randomly assigned to receive sucrose solution or be breastfed before venepuncture. Variations in the total hemoglobin concentration [HbT] in the contralateral somatosensory cortex were assessed with near infrared spectroscopy. The Neonatal Facial Coding System (NFCS) was used to assess reactions.

RESULTS

There were 114 term neonates included, with 102 included for the primary outcome (breastfed group: 48; sucrose group: 54). Similar maximum increases in [HbT] were observed in both groups (mean±SD: sucrose group: 31.2±58.1 μmol/L; breastfed group: 38.9±61.4 μmol/L; P=0.70). Breastfed neonates presented more behavioral expressions that indicated pain compared with sucrose-administered neonates (46.8% vs. 26.8% of NFCS ≥1, P=0.04). The maximum increase in [HbT] was persistent, although newborn infants who did not express behavioral signs of pain had lower concentrations than neonates who did (mean±SD: 21.2±29.1 vs. 60.0±89.8 μmol/L, P<0.01).

DISCUSSION

There was no difference in the cortical responses to pain during venepuncture in newborn infants who were administered sucrose versus those who were breastfed.

Effectiveness of Sucrose Used Routinely for Pain Relief and Neonatal Clinical Risk in Preterm Infants: A Nonrandomized Study

BACKGROUND

Preterm infants (PI) requiring the neonatal intensive care unit are exposed to early repetitive pain/distress. Little is known about how pain relief strategies interact with infants' clinical health status, such as severity of illness with pain responses. This study aimed to examine main and interactive effects of routine sucrose intervention and neonatal clinical risk (NCR) on biobehavioral pain reactivity-recovery in PI during painful blood collection procedures.

METHODS

Very low birth weight PI (<1500 g; n=104) were assigned to low and high clinical risk groups, according to the Clinical Risk Index for Babies. Sucrose group (n=52) received sucrose solution (25%; 0.5 mL/kg) 2 minutes before the procedures and control group received standard care. Biobehavioral pain reactivity-recovery was assessed according to the Neonatal Facial Coding System, sleep-wake state scale, crying time, and heart rate at 5 phases (baseline, antisepsis, puncture (P), recovery-dressing, and recovery-resting [R]). Repeated measure ANOVA with mixed-design was performed considering pain assessment phases, intervention group, and NCR.

RESULTS

Independent of NCR, sucrose presented main effect in decreasing neonates' facial activity pain responses and crying time, during P and R. Independent of NCR level or routine sucrose intervention, all neonates displayed activated state in P and decreased biobehavioral responses in R phase. Although no sucrose or NCR effects were observed on physiological reactivity, all neonates exhibited physiological recovery 10 minutes after P, reaching the same heart rate patterns as the baseline.

CONCLUSIONS

Independent of NCR level, sucrose intervention for pain relief during acute painful procedures was effective to reduce pain intensity and increase biobehavioral regulation.