The developmental character of cardiac autonomic responses to an acute noxious event in 4- and 8-month-old healthy infants

Newborn and Infant Parasympathetic Evaluation (NIPE™) Monitor for Assessing Pain During Surgery and Interventional Procedures: A Systematic Review

BACKGROUND

The heart rate variability-derived Newborn Infant Parasympathetic Evaluation (NIPE) monitor has been designed to be an objective, non-invasive tool for the assessment of pain and discomfort in children under 2 years of age. The aim of this systematic review was to evaluate the ability of NIPE to assess pain in neonates and infants during surgical and/or painful procedures.

METHODS

A systematic review (2010-2023) was conducted using PRISMA guidelines. Studies containing children above 2-years-old were excluded. The ROBINS-I (Risk of Bias in Non-randomised Studies of Interventions) tool was used to assess the quality of included studies.

RESULTS

9 databases were searched identifying 470 articles, 460 did not meet the inclusion criteria and were excluded; therefore, 10 studies with 548 participants were included. NIPE was used to assess intraoperative and postoperative pain for surgery under general anaesthesia (5 studies), as well as acute and prolonged pain from other interventional procedures (5 studies). For surgery under general anaesthesia: NIPE has shown to detect nociceptive events (e.g., skin incision, intubation), insufficient analgesia intraoperatively and to predict early postoperative pain. For painful interventional procedures: NIPE has shown to detect acute pain with a high sensitivity and negative predictive value.

CONCLUSION

NIPE has been used to assess pain in surgery and for various painful procedures. NIPE can detect intraoperative pain and reflect early postoperative pain. NIPE may be useful in evaluating procedural pain, however with heterogenous outcomes, more studies are required to confirm its efficacy.

TYPE OF STUDY

Systematic Review.

LEVEL OF EVIDENCE

Level II.

Evaluation of Nociception during Pediatric Surgery: A Topical Review

The association between intraoperative nociception and increased patient's morbidity is well established. However, hemodynamic parameters, such as heart rate and blood pressure, may result in an inadequate monitor of nociception during surgery. Over the last two decades, different devices have been marketed to "reliably" detect intraoperative nociception. Since the direct measure of nociception is impractical during surgery, these monitors measures nociception surrogates such as sympathetic and parasympathetic nervous systems responses (heart rate variability, pupillometry, skin conductance), electroencephalographic changes, and muscular reflex arc. Each monitor carries its own advantages and disadvantages. The manuscript aims to give an overview of the most up-to-date information available in the literature on current nociceptor monitors available in clinical practice, with particular focus on their applications in pediatrics.

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 newborn infant parasympathetic evaluation index for acute procedural pain assessment in preterm infants

BACKGROUND

Accurate assessments of pain in hospitalized preterm infants present a major challenge in improving the short- and long-term consequences associated with painful experiences. We evaluated the ability of the newborn infant parasympathetic evaluation (NIPE) index to detect acute procedural pain in preterm infants.

METHODS

Different painful and stressful interventions were prospectively observed in preterm infants born at 25 + 0 to 35 + 6 weeks gestation. Pain responses were measured using the composite Premature Infant Pain Profile Revised (PIPP-R) scale, the NIPE index, and skin conductance responses (SCR). Outcome measures were correlations between the NIPE index, the PIPP-R score, and the SCR. Sensitivity/specificity analyses tested the accuracy of the NIPE index and SCR.

RESULTS

Two hundred and fifty-four procedures were recorded in 90 preterm infants. No significant correlation was found between PIPP-R and the NIPE index. PIPP-R and SCR were positively correlated (r = 0.27, P < 0.001), with stronger correlations for painful procedures (r = 0.68, P < 0.001) and especially for skin-breaking procedures (r = 0.82, P < 0.001). The NIPE index and SCR had high sensitivity and high negative predictive values to predict PIPP-R > 10, especially for skin-breaking painful procedures.

CONCLUSIONS

We found no significant correlation between the NIPE index and PIPP-R during routine painful or stressful procedures in preterm infants.

IMPACT

Exposure to repetitive pain can lead to neurodevelopmental sequelae. Behavior-based pain scales have limited clinical utility, especially for preterm infants. New devices for monitoring physiological responses to pain have not been validated sufficiently in preterm infants. This study found that the NIPE index was not significantly correlated to the validated PIPP-R scale during acute procedural pain. Secondary analysis of this study showed that NIPE index and SCRs may help to exclude severe pain in preterm infants. In clinical practice, measurements of physiological parameters should be combined with behavior-based scales for multidimensional pain assessments.

Assessment of Pain in the Newborn: An Update

Preterm and term neonate pain assessment in neonatal intensive care units is vitally important because of the prevalence of procedural and postoperative pain. Of the 40 plus tools available, a few should be chosen for different populations and contexts (2 have been validated in premature infants). Preterm neonates do not display pain behaviors and physiologic indicators as reliably and specifically as full-term infants, and are vulnerable to long-term sequelae of painful experiences. Brain-oriented approaches may become available in the future; meanwhile, neonatal pain assessment tools must be taught, implemented, and their use optimized for consistent, reproducible, safe, and effective treatment.

Impact of skin-to-skin contact on maternal comfort in patients with elective caesarean section: A pilot study

OBJECTIVE

Caesarean section is a well-known cause of difficulties in breastfeeding initiation. Mother-infant skin-to-skin contact allows to improve breastfeeding and maternal comfort but remains few practiced during caesarean section. Our objective was to evaluate maternal comfort before and after immediate skin-to-skin contact in case of elective caesarean section.

METHODS

This was a prospective, observational, monocenter study including patients with elective caesarean section. Mother-infant skin-to-skin contact was begun immediately after birth. The Analgesia Nociception Index (ANI) is a well know heart rate variability (HRV) index, currently used in anesthesia, which decreases during painful stimulation and increases with maternal comfort. The Analgesia Nociception Index was compared before and after skin-to-skin contact.

RESULTS

53 patients were included. Skin-to-skin contact was started on average 4min (2-14, IIQ (3-5)) after birth. The median duration was 21min (4-40, IIQ (12.3-29.5)). It was interrupted in 24 patients: 9 from mother's wish, 11 for maternal reasons (drowsiness, stress, pain, maternal hypothermia, lipothymia, vertigo, nausea, cough) and 4 for the newborn (respiratory distress, low pH). The median Analgesia Nociception Index at the end of skin-to-skin contact and at the end of the intervention was statistically higher than that before skin-to-skin contact (p=0.034 and p<10-3 respectively).

CONCLUSION

Skin-to-skin contact is possible during caesarean section and allows a better maternal comfort. It should be encouraged and proposed to patients during elective caesarean section. It will be interesting to evaluate it in case of caesarean section during labor.

Newborn infant parasympathetic evaluation (NIPE) as a predictor of hemodynamic response in children younger than 2 years under general anesthesia: an observational pilot study

Background

It is still unknown whether newborn infant parasympathetic evaluation (NIPE), based on heart rate variability (HRV) as a reflection of parasympathetic nerve tone, can predict the hemodynamic response to a nociception stimulus in children less than 2 years old.

Methods

Fifty-five children undergoing elective surgery were analyzed in this prospective observational study. Noninvasive mean blood pressure (MBP), heart rate (HR) and NIPE values were recorded just before and 1 min after general anesthesia with endotracheal intubation as well as skin incision. The predictive performance of NIPE was evaluated by receiver-operating characteristic (ROC) curve analysis. A significant hemodynamic response was defined by a > 20% increase in HR and/or MBP.

Results

Endotracheal intubation and skin incision caused HR increases of 22.2% (95% confidence interval [CI] 17.5–26.9%) and 3.8% (2.1–5.5%), MBP increases of 18.2% (12.0–24.4%) and 10.6% (7.7–13.4%), and conversely, NIPE decreases of 9.9% (5.3–14.4%) and 5.6% (2.1–9.1%), respectively (all P < 0.01 vs. pre-event value). Positive hemodynamic responses were observed in 32 patients (62.7%) during tracheal intubation and 13 patients (23.6%) during skin incision. The area under the ROC curve values for the ability of NIPE to predict positive hemodynamic responses at endotracheal intubation and skin incision were 0.65 (0.50–0.78) and 0.58 (0.44–0.71), respectively.

Conclusions

NIPE reflected nociceptive events as well as anesthestic induction in children less than 2 years undergoing general anaesthetia. Nevertheless, NIPE may not serve as a sensitive and specific predictor to changes in hemodynamics.

Trial registration

This study was registered on May 3, 2018 in the Chinese Clinical Trail Registry; the registration number is (ChiCTR1800015973).

Calmer: a robot for managing acute pain effectively in preterm infants in the neonatal intensive care unit

Introduction:

For preterm infants in the neonatal intensive care unit, early exposure to repeated procedural pain is associated with negative effects on the brain. Skin-to-skin contact with parents has pain-mitigating properties, but parents may not always be available during procedures. Calmer, a robotic device that simulates key pain-reducing components of skin-to-skin contact, including heart beat sounds, breathing motion, and touch, was developed to augment clinical pain management.

Objective:

Our objective was to evaluate the initial efficacy of Calmer for mitigating pain in preterm infants. We hypothesized that, compared to babies who received a human touch–based treatment, facilitated tucking, infants on Calmer would have lower behavioural and physiological pain indices during a single blood test required for clinical care.

Methods:

Forty-nine preterm infants, born between 27 and 36 weeks of gestational age, were randomized either to facilitated tucking or Calmer treatment. Differences between groups in changes across 4 procedure phases (baseline 1, baseline 2, poke, and recovery) were evaluated using (1) the Behavioral Indicators of Infant Pain scored by blind coders from bedside videotape and (2) heart rate and heart rate variability continuously recorded from a single-lead surface ECG (lead II) (Biopac, Canada) sampled at 1000 Hz using a specially adapted portable computer system and processed using Mindware.

Results:

No significant differences were found between groups on any outcome measures.

Conclusion:

Calmer provided similar treatment efficacy to a human touch–based treatment. More research is needed to determine effects of Calmer for stress reduction in preterm infants in the neonatal intensive care unit over longer periods.

Evaluation of prolonged pain in preterm infants with pneumothorax using heart rate variability analysis and EDIN (Échelle Douleur Inconfort Nouveau-Né, neonatal pain and discomfort scale) scores

Purpose

The EDIN scale (Échelle Douleur Inconfort Nouveau-Né, neonatal pain and discomfort scale) and heart rate variability has been used for the evaluation of prolonged pain. The aim of our study was to assess the value of the newborn infant parasympathetic evaluation (NIPE) index and EDIN scale for the evaluation of prolonged pain in preterm infants with chest tube placement due to pneumothorax.

Methods

This prospective observational study assessed prolonged pain in preterm infants with a gestational age between 33 and 35 weeks undergoing installation of chest tubes. Prolonged pain was assessed using the EDIN scale and NIPE index.

Results

There was a significant correlation between the EDIN scale and NIPE index (r=-0.590, P=0.003). Prolonged pain is significantly more severe in the first 6 hours following chest tube installation (NIPE index: 60 [50–86] vs. 68 [45–89], P<0.002; EDIN score: 8 [7–11] vs. 6 [4–8], P<0.001).

Conclusion

Prolonged pain can be accurately assessed with the EDIN scale and NIPE index. However, evaluation with the EDIN scale is time-consuming. The NIPE index can provide instantaneous assessment of prolonged and continuous pain.

Impact of skin-to-skin contact on the autonomic nervous system in the preterm infant and his mother

Before, during and after mother-newborn skin-to-skin contact (SSC), parasympathetic activity was evaluated by heart rate variability (HRV) analysis. SSC had a favorable impact on maternal and premature infant parasympathetic activities with a more pronounced response for neonates when the basal HRV values were lower, without modifications of EDIN scores, temperatures or oxygen saturation.

Assessment of pain in the neonate

Accurate pain assessment in preterm and term neonates in the neonatal intensive care unit (NICU) is of vital importance because of the high prevalence of painful experiences in this population, including both daily procedural pain and postoperative pain. Over 40 tools have been developed to assess pain in neonates, and each NICU should choose a limited number of pain assessment tools for different populations and contexts. Only two pain assessment tools have a metric adjustment to account for differences of pain assessment in prematurity. Preterm neonates do not display behavior and physiologic indicators of pain as reliably and specifically as full term infants, and preterm infants are vulnerable to long term sequelae of painful experiences. "Brain-oriented" approaches for more objective measurement of pain in neonates may become available in the future. In the meantime, neonatal pain assessment tools need to be taught, implemented, and their ongoing use optimized to form a consistent, reproducible basis for the safe and effective treatment of neonatal pain.

[Impact of cocooning and maternal voice on the autonomic nervous system activity in the premature newborn infant]

INTRODUCTION

Discomfort, pain, and stress have an adverse impact on the psychomotor development in the premature newborn infant. Recent studies indicate that pain and stress are associated with a reduction of parasympathetic outflow. We hypothesized that cocooning associated with the human voice has a favorable impact on parasympathetic activity in the premature newborn infant.

METHOD

We compared heart rate variability (HRV) before and after standardized cocooning phases associated with the human voice and carried out: 1) by the mother and 2) by a third person. HRV was assessed and expressed as an index reflecting the parasympathetic tone.

RESULTS

Ten children were included (median gestational age, 33 weeks (30(+4)-33(+2))). We observed a higher HRV index after the period of cocooning associated with the human voice compared with the baseline measurement (P<0.05), whether the procedure was carried out by the mother or a third person.

CONCLUSION

This study shows that cocooning associated with the human voice enhances HRV in the preterm newborn infant, indicating an increase in parasympathetic activity after cocooning associated with the human voice. However, the impact is similar whether the cocooning associated with the human voice is performed by the mother or a third person. This result suggests that cocooning associated with the human voice carried out either by the mother or a third person contributes to decreasing stress and discomfort in the premature newborn infant.

Does breastfeeding reduce acute procedural pain in preterm infants in the neonatal intensive care unit? A randomized clinical trial

Managing acute procedural pain effectively in preterm infants in the neonatal intensive care unit remains a significant problem. The objectives of this study were to evaluate the efficacy of breastfeeding for reducing pain and to determine if breastfeeding skills were altered after this treatment. Fifty-seven infants born at 30-36 weeks gestational age were randomized to be breastfed (BF) or to be given a soother during blood collection. Changes in the Behavioral Indicators of Infant Pain (BIIP) and in mean heart rate (HR) across 3 phases of blood collection were measured. In the BF group, the Premature Infant Breastfeeding Behaviors (PIBBS) scale was scored before and 24 hours after blood collection. Longitudinal regression analysis was used to compare changes in Lance/squeeze and Recovery phases of blood collection between groups, with gestational age at birth, baseline BIIP scores, and mean HR included as covariates. Differences in PIBBS scores were assessed using a paired t-test. Relationships between PIBBS scores, BIIP scores, and HR were evaluated with Pearson correlations. No differences between treatment groups were found: BIIP (P=0.44, confidence interval [CI] -1.60-0.69); HR (P=0.73, CI -7.0-10.0). Infants in the BF group showed improved PIBBS scores after the treatment (P<0.01, CI -2.7 to -0.2). Lower BIIP scores during the Lance/squeeze were associated significantly with more mature sucking patterns (r=-0.39, P<0.05). Breastfeeding during blood collection did not reduce pain indices or interfere with the acquisition of breastfeeding skills. Exploratory analyses indicate there may be benefit for infants with mature breastfeeding abilities.

Heart rate variability analysis for newborn infants prolonged pain assessment

Pain management is a general concern for healthcare quality. In the particular context of neonatal care, it's well known that an efficient pain management will decrease mortality and morbidity of newborn infants. Furthermore, the plasticity of developing brain is vulnerable to pain and/or stress, that in turn may cause long term neurodevelopmental changes, including altered pain sensitivity and neuroanatomic and behavioural abnormalities. During neonatal intensive care stay, large number of painful procedures are performed, the majority of which are not accompanied by adequate analgesia. Optimal management requires competent pain assessment which can be especially difficult to perform in this non verbal population. We have developed an instantaneous heart rate variability (HRV) analysis method, non intrusive and user-friendly, based on the ECG signal acquisition. This analysis method enabled us to design parameters related to the influence of pain on the Autonomic Nervous System (ANS) activity. This paper presents the application of this method, previously validated for adults under general anesthesia, to the domain of newborn infants prolonged pain assessment.

Developmental changes in autonomic nervous system resting and reactivity measures in Latino children from 6 to 60 months of age

OBJECTIVE

: This study describes the developmental changes and individual stability in autonomic nervous system (ANS) resting and challenge responses for a cohort of primarily Latino, low-income children during the first 5 years of life.

METHODS

: ANS measures of the parasympathetic nervous system (respiratory sinus arrhythmia [RSA]) and sympathetic nervous system (preejection period [PEP]) were collected on a representative sample of the full cohort at 6, 12, 42, and 60 months of age (N = 378). The children participated in a standardized protocol to elicit ANS responses during resting and challenging states. Reactivity profiles were created to summarize each child's combined RSA and PEP reactivity (i.e., change in response to challenges compared to a resting state).

RESULTS

: Results showed developmental changes in ANS measures from 6 to 60 months: heart rate decreased, RSA increased, PEP increased, and frequency of classic reactivity profiles of reciprocal sympathetic activation and parasympathetic withdrawal increased. Correlations showed moderate stability for resting and challenging conditions but not reactivity.

CONCLUSIONS

: These findings suggest that low-income Latino children, from 6 to 60 months of age, showed ANS developmental changes and moderate individual stability for resting and challenge responses but not for reactivity. There was a significant shift in the frequency of children with the classic reactivity profile from 6 by 60 months of age. This is the first cohort study to show the developmental changes in ANS and young children's increase in their biologic sensitivity to the environment during the first 5 years of life.

Poincaré plot descriptors of heart rate variability as markers of persistent pain expression in freely moving rats

Evaluation of pain is a critical issue in human pathologies but also in animal experimentation. In human studies there is growing evidence that cardiovascular outputs such as heart rate variability (HRV) might be of interest to detect and measure pain expression. Indeed, systems controlling cardiovascular function are closely coupled to the perception of pain. To demonstrate the interest of HRV, we have combined radiotelemetry and remote-controlled nociceptive tests in rats submitted to various situations of acute and persistent inflammatory pain. We found the Poincaré plot descriptor SD1 and pNN18 to represent robust indicators of pain, especially in the case of persistent inflammatory states. Further studies will be performed in order to understand by which mechanisms pain-related increases in HRV are produced and if these descriptors can be used for other persistent pain states.

Arousal from sleep mechanisms in infants

Arousals from sleep allow sleep to continue in the face of stimuli that normally elicit responses during wakefulness and also permit awakening. Such an adaptive mechanism implies that any malfunction may have clinical importance. Inadequate control of arousal in infants and children is associated with a variety of sleep-related problems. An excessive propensity to arouse from sleep favors the development of repeated sleep disruptions and insomnia, with impairment of daytime alertness and performance. A lack of an adequate arousal response to a noxious nocturnal stimulus reduces an infant's chances of autoresuscitation, and thus survival, increasing the risk for Sudden Infant Death Syndrome (SIDS). The study of arousability is complicated by many factors including the definition of an arousal; the scoring methodology; the techniques used (spontaneous arousability versus arousal responses to endogenous or exogenous stimuli); and the confounding factors that complicate the determination of arousal thresholds by changing the sleeper's responses to a given stimulus such as prenatal drug, alcohol, or cigarette use. Infant age and previous sleep deprivation also modify thresholds. Other confounding factors include time of night, sleep stages, the sleeper's body position, and sleeping conditions. In this paper, we will review these different aspects for the study of arousals in infants and also report the importance of these studies for the understanding of the pathophysiology of some clinical conditions, particularly SIDS.

Prenatal alcohol exposure alters biobehavioral reactivity to pain in newborns

OBJECTIVES

To examine biobehavioral responses to an acute pain event in a Cape Town, South Africa, cohort consisting of 28 Cape Colored (mixed ancestry) newborns (n = 14) heavily exposed to alcohol during pregnancy (exposed), and born to abstainers (n = 14) or light (< or = 0.5 oz absolute alcohol/d) drinkers (controls).

METHODS

Mothers were recruited during the third trimester of pregnancy. Newborn data were collected on postpartum day 3 in the maternity obstetrical unit where the infant had been delivered. Heavy prenatal alcohol exposure was defined as maternal consumption of at least 14 drinks/wk or at least 1 incident of binge drinking/mo. Acute stress-related biobehavioral markers [salivary cortisol, heart rate (HR), respiratory sinus arrhythmia (RSA), spectral measures of heart rate variability (HRV), and videotaped facial actions] were collected thrice during a heel lance blood collection (baseline, lance, and recovery). After a feeding and nap, newborns were administered an abbreviated Brazelton Neonatal Behavioral Assessment Scale.

RESULTS

There were no between-group differences in maternal age, marital status, parity, gravidity, depression, anxiety, pregnancy smoking, maternal education, or infant gestational age at birth (all ps > 0.15). In both groups, HR increased with the heel lance and decreased during the postlance period. The alcohol-exposed group had lower mean HR than controls throughout, and showed no change in RSA over time. Cortisol levels showed no change over time in controls but decreased over time in exposed infants. Although facial action analyses revealed no group differences in response to the heel lance, behavioral responses assessed on the Brazelton Neonatal Scale showed less arousal in the exposed group.

CONCLUSIONS

Both cardiac autonomic and hypothalamic-pituitary-adrenal stress reactivity measures suggest a blunted response to an acute noxious event in alcohol-exposed newborns. This is supported by results on the Brazelton Neonatal Scale indicating reduced behavioral arousal in the exposed group. To our knowledge, these data provide the first biobehavioral examination of early pain reactivity in alcohol-exposed newborns and have important implications for understanding neuro-/biobehavioral effects of prenatal alcohol exposure in the newborn period.

Reflexly evoked coactivation of cardiac vagal and sympathetic motor outflows: observations and functional implications

1. The purpose of the present review is to highlight the pattern of activity in the parasympathetic and sympathetic nerves innervating the heart during their reflex activation. 2. We describe the well-known reciprocal control of cardiac vagal and sympathetic activity during the baroreceptor reflex, but point out that this appears to be the exception rather than the rule and that many other reflexes reviewed herein (e.g. peripheral chemoreceptor, nociceptor, diving response and oculocardiac) involve simultaneous coactivation of both autonomic limbs. 3. The heart rate response during simultaneous activation of cardiac autonomic outflows is unpredictable because it does not simply reflect the summation of opposing influences. Indeed, it can result in bradycardia (peripheral chemoreceptor, diving and corneal), tachycardia (nociceptor) and, in some circumstances, can predispose to malignant arrhythmias. 4. We propose that this cardiac autonomic coactivation may allow greater cardiac output during bradycardia (increased ventricular filling time and stronger contraction) than activation of the sympathetic limb alone. This may be important when pumping blood into a constricted vascular tree, such as is the case during the peripheral chemoreceptor reflex and the diving response.

Monitoring analgesia

Analgesia (pain relief) amnesia (loss of memory) and immobilisation are the three major components of anaesthesia. The perception of pain, and therefore, the need for analgesia, is individual, and the monitoring of analgesia is indirect and, in essence, of the moment. Under general anaesthesia, analgesia is continually influenced by external stimuli and the administration of analgesic drugs, and cannot be really separated from anaesthesia: the interaction between analgesia and anaesthesia is inescapable. Autonomic reactions, such as tachycardia, hypertension, sweating and lacrimation, although non-specific, are always regarded as signs of nociception or inadequate analgesia. Autonomic monitoring techniques, such as the analysis of heart rate variability, laser Doppler flowmetry, phlethysmographically derived indices and the pupillary light reflex, may help to quantitate reactions of the autonomic nervous system. For the past few years, automated electroencephalographic analysis has been of great interest in monitoring anaesthesia and could be useful in adapting the peroperative administration of opioids. A range of information collected from the electroencephalogram, haemodynamic readings and pulse plethysmography might be necessary for monitoring the level of nociception during anaesthesia. Information theory, multimodal monitoring, and signal processing and integration are the basis of future monitoring.

The ontogeny of autonomic measures in 6- and 12-month-old infants

The purpose of this study was to develop a standardized protocol to measure preejection period (PEP), a measure of sympathetic nervous system, and respiratory sinus arrhythmia (RSA), a measure of parasympathetic nervous system, during resting and challenging states for 6- and 12-month-old infants and to determine developmental changes and individual stability of these measures. A 7-min reactivity protocol was administered to Latino infants at 6 months (n=194) and 12 months (n=181). Results showed: (1) it is feasible to measure PEP and RSA in infants, (2) the protocol elicited significant autonomic changes, (3) individual resting autonomic measures were moderately stable from 6 to 12 months, but reactivity measures were not stable, and (4) heart rate and RSA resting and challenge group means changed significantly from 6 to 12 months. Findings suggest that although infants' autonomic responses show developmental changes, individuals' rank order is stable from 6 to 12 months of age.

Neurokininergic mechanism within the lateral crescent nucleus of the parabrachial complex participates in the heart-rate response to nociception

We wanted to ascertain whether the lateral parabrachial nucleus was involved in mediating the heart-rate response evoked during stimulation of somatic nociceptors. Reversible inactivation of the lateral parabrachial nucleus, using a GABA(A) agonist, reduced the reflex tachycardia evoked during noxious (mechanical) stimulation of the forelimb by approximately 50%. The same effect was observed after blockade of neurokinin 1 receptors within the lateral parabrachial nucleus, indicating a possible involvement for substance P as a neurotransmitter. Immunocytochemistry revealed a strong expression of substance P-immunoreactive fibers and boutons in all lateral subnuclei, but they were particularly dense in the lateral crescent subnucleus. Histological verification showed that the most effective injection sites for attenuating the noxious-evoked tachycardia were all placed in or near to the lateral crescent nucleus of the lateral parabrachial complex. Many single units recorded from this region were activated by high-intensity brachial nerve stimulation. The brachial nerve evoked firing responses of some of these neurons was reversibly reduced after local delivery of a neurokinin 1 receptor antagonist. However, only a minority of these neurons followed a paired-pulse stimulation protocol applied to the spinal cord, suggesting a predominance of indirect projections from the spinal cord to the parabrachial nucleus. We conclude that the cardiac component of the response to somatic nociception involves indirect spinal pathways that most likely excite neurons located in the lateral crescent nucleus of the parabrachial complex via activation of neurokinin 1 receptors.

The yin and yang of cardiac autonomic control: vago-sympathetic interactions revisited

We review the pattern of activity in the parasympathetic and sympathetic nerves innervating the heart. Unlike the conventional textbook picture of reciprocal control of cardiac vagal and sympathetic nervous activity, as seen during a baroreceptor reflex, many other reflexes involve simultaneous co-activation of both autonomic limbs. Indeed, even at 'rest', the heart receives tonic drives from both sympathetic and parasympathetic cardiac nerves. Autonomic co-activation occurs during peripheral chemoreceptor, diving, oculocardiac, somatic nociceptor reflex responses as well as being evoked from structures within the brain. It is suggested that simultaneous co-activation may lead to a more efficient cardiac function giving greater cardiac output than activation of the sympathetic limb alone; this permits both a longer time for ventricular filling and a stronger contraction of the myocardium. This may be important when pumping blood into a constricted vascular tree such as is the case during the diving response. We discuss that in some instances, high drive to the heart from both autonomic limbs may also be arrhythmogenic.

Excitatory convergence of periaqueductal gray and somatic afferents in the solitary tract nucleus: role for neurokinin 1 receptors

Our previous studies (Boscan P, Kasparov S, and Paton JF. Eur J Neurosci 16: 907–920, 2002) showed that activation of somatic afferents attenuated the baroreceptor reflex via neurokinin type 1 (NK1) and GABAA receptors within the nucleus of the solitary tract (NTS). The periaqueductal gray matter (PAG) can also depress baroreceptor reflex function and project to the NTS. In the present study, we have tested the possibility that the dorsolateral (dl)-PAG projects to the NTS neurons that also respond to somatic afferent input. In an in situ, arterially perfused, unanesthetized decerebrate rat preparation, somatic afferents (brachial plexus), cervical spinal cord, and dl-PAG were stimulated electrically, whereas NTS neurons were recorded extracellularly. From 45 NTS neurons excited by either brachial plexus or dl-PAG stimulation, 41 received convergence excitatory inputs from both afferents. Onset latency and evoked peak discharge frequency from brachial plexus afferents were 39.4 ± 4.7 ms and 10.7 ± 1.1 Hz, whereas this was 43.9 ± 6.4 ms and 7.9 ± 1 Hz, respectively, following dl-PAG stimulation. As revealed by using a paired pulse stimulation protocol, monosynaptic connections were found in 9 of 36 neurons tested from both spinal cord and dl-PAG. We tested NK1-receptor sensitivity in 38 neurons that received convergent inputs from brachial plexus/PAG. Fifteen neurons were sensitive to selective antagonism of NK1 receptors. CP-99994, the NK1 antagonist, failed to alter ongoing firing activity but reduced the evoked peak discharge frequency following stimulation of both brachial plexus (from 12.3 ± 1.8 to 7.2 ± 1.3 Hz; P < 0.01) and PAG (from 7.8 ± 1.5 to 4.5 ± 1 Hz; P < 0.01). We conclude that 1) somatic brachial and PAG afferents can converge onto single NTS neurons; 2) this convergence occurs via either direct or indirect pathways; and 3) NK1 receptors are activated by some of these inputs.

Incomplete arousal processes in infants who were victims of sudden death

Infants who became victims of sudden infant death syndrome (SIDS) aroused less from sleep than control infants. This study was conducted to determine the characteristics of arousal from sleep of infants who eventually died of SIDS. Sixteen infants were monitored some days or weeks before they died of SIDS. Their polygraphic sleep recordings were compared with those of matched control infants. Arousals were scored as subcortical activation (incomplete arousals) or cortical arousal (complete arousals). Cortical arousals were significantly less frequent in the victims who would succumb to SIDS in the future than in the control infants during both REM and non-REM sleep (p = 0.039). The frequency (p = 0.017) and duration (p = 0.005) of subcortical activation were significantly greater in the infants who died of SIDS than in the control infants during REM sleep. Compared with the control infants, the infants who later died of SIDS had more frequent subcortical activation in the first part of the night, between 9:00 P.M. and 12:00 A.M. (p = 0.038), and fewer cortical arousals during the latter part of the night, between 3:00 and 6:00 A.M. (p = 0.011). The present data are suggestive of incomplete arousal processes in infants who eventually died at a time they were presumed to have been asleep.

[To understand blood pressure and heart rate variability]

OBJECTIVES

To review current data on the heart rate and blood pressure variability.

DATA SOURCES

Search through Medline databases of articles in french or english.

DATA SELECTION

Original articles and case reports were selected according to their quality and main advances. The articles were analysed in order to obtain current data about the methods of study and clinical application of blood pressure and heart rate variability.

DATA SYNTHESIS

Various regulatory systems in the cardiovascular system play crucial roles in controlling and assuring adequate perfusion of the peripheral tissues. Among them the baroreceptor reflex is the most important regulatory mechanism in the short-term control of the heart rate and blood pressure, and operates through the autonomic nervous system. The gain of the cardiac baroreflex further referred to, as baroreflex sensitivity is an interesting way to study this system. Unfortunately, with our current knowledge, it is not possible to predict the instantaneous output of the baroreceptor in response to instantaneous changes in input within a frequency range of physiological importance. The fast Fourier transform can describe variables as the sum of elementary oscillatory components and it has been established as practical clinical methods for detecting abnormalities in cardiovascular control. A time-frequency distribution provides an indication of how the spectral energy distribution varies with time and it is an interesting tool in non-stationary data. One of the major motivations behind spectral analysis is the hope that the combination of time-domain and frequency-domain analyses will provide dynamical informations about the relation between blood pressure and heart rate.

Physiologic correlates of comfort in healthy children

Pain assessment is particularly challenging when children are unable or unwilling to provide a self-report. Although clinicians frequently use vital signs as an adjunct to pain assessment, little evidence exists to support this practice. The purpose of this study was to explore the ability of selected physiologic variables (peripheral skin temperature, heart rate, skin conductance activity [SCA], respiratory rate, electromyogram [EMG] of the frontalis and right forearm muscles, and systolic and diastolic blood pressure [BP]) to detect changes in children's autonomic arousal from baseline. A one-group, repeated measures, randomized crossover design guided the study. Chosen from a convenience sample, 100 healthy children (ages 8-17 years) served as their own controls while undergoing two levels of intervention: cold pressor pain and guided imagery. Although most physiologic responses showed changes in the expected direction, EMG, SCA, and heart rate decreased slightly during cold pressor. Few significant intercorrelations were demonstrated among the physiologic variables. SCA, forehead EMG, respiratory rate, systolic and diastolic BP detected significant changes in arousal across measures. Notably, heart rate failed to detect changes for any of the measures. Results emphasize the need for caution in interpreting heart rate as an index of comfort. Further research is needed to examine the effects of clinical pain on physiologic indices and to further examine age and sex influences. To be relevant for assessment of acute established pain, physiologic variables must also be tested for their sensitivity beyond the immediate period of autonomic arousal.

Developmental and contextual influences on autonomic reactivity in young children

Studies of cardiovascular reactivity in young children have generally employed integrated, physiologically complex measures, such as heart rate and blood pressure, which are subject to the multiple influences of factors such as blood volume, hematologic status, thermoregulation, and autonomic nervous system (ANS) tone. Reactivity studies in children have rarely employed more differentiated, proximal measures of autonomic function capable of discerning the independent effects of sympathetic and parasympathetic responses. We describe 1) the development, validity, and reliability of a psychobiology protocol assessing autonomic reactivity to challenge in 3- to 8-year-old children; 2) the influences of age, gender, and study context on autonomic measures; and 3) the distributions of reactivity measures in a normative sample of children and the prevalences of discrete autonomic profiles. Preejection period (PEP) and respiratory sinus arrythmia (RSA) were measured as indices of sympathetic and parasympathetic nervous system reactivity, respectively, and autonomic profiles were created to offer summative indices of PEP and RSA response. Results confirmed the protocol's validity and reliability, and showed differences in autonomic reactivity by age and study context, but not by gender. The studies' findings offer guidelines for future research on autonomic reactivity in middle childhood and support the feasibility of examining sympathetic and parasympathetic responses to challenge in 3- to 8-year-old children.

Early pain in preterm infants. A model of long-term effects

There are multiple lines of evidence suggesting that in vulnerable prematurely born infants, repeated and prolonged pain exposure may affect the subsequent development of pain systems, as well as potentially contribute to alterations in long-term development and behavior. Multiple factors cumulatively contribute to altered developmental trajectories in such infants. These include characteristics of the developing organism (low tactile threshold, sensitization, rapid brain development), characteristics intrinsic to the infant (gestation, illness severity), characteristics of the experience in the neonatal intensive care unit (pain exposure and cumulative stress), and characteristics of the caregivers within their family and social context. This article provides a model for examining long-term effects of pain in the newborn period embedded in a developmental context framework.

Somatic nociception activates NK1 receptors in the nucleus tractus solitarii to attenuate the baroreceptor cardiac reflex

There is limited information regarding the integration of visceral and somatic afferents within the nucleus of the solitary tract (NTS). We studied the interaction of nociceptive and baroreceptive inputs in this nucleus in an in situ arterially perfused, un-anaesthetized decerebrate preparation of rat. At the systemic level, the gain of the cardiac component of the baroreceptor reflex was attenuated significantly by noxious mechanical stimulation of a forepaw. This baroreceptor reflex depression was mimicked by NTS microinjection of substance P and antagonized by microinjection of either bicuculline (a GABAA receptor antagonist) or a neurokinin type 1 (NK1) receptor antagonist (CP-99994). The substance P effect was also blocked by a bilateral microinjection of bicuculline, at a dose that was without effect on basal baroreceptor reflex gain. Baroreceptive NTS neurons were defined by their excitatory response following increases in pressure within the ipsilateral carotid sinus. In 27 of 34 neurons the number of evoked spikes from baroreceptor stimulation was reduced significantly by concomitant electrical stimulation of the brachial nerve (P < 0.01). Furthermore, the attenuation of baroreceptor inputs to NTS neurons by brachial nerve stimulation was prevented by pressure-ejection of bicuculline from a multi-barrelled microelectrode (n = 8). In a separate population of 17 of 45 cells tested, brachial nerve stimulation evoked an excitatory response that was antagonized by blockade of NK1 receptors. We conclude that nociceptive afferents activate NK1 receptors, which in turn excite GABAergic interneurons impinging on cells mediating the cardiac component of the baroreceptor reflex.

Methodological considerations for the use of heart rate variability as a measure of pain reactivity in vulnerable infants

Measures of HR and HRV offer multiple indices of reactivity to painful events. These measures are particularly helpful in preterm and ill infants where distress signals are often nonspecific and ambiguous. HR is easy to acquire, and a variety of widely used techniques are available for processing it. In general, the neuroanatomic and neurophysiologic bases for pain perception are in place even in the most preterm infant and produce patterns of HR and HRV responses that are similar across multiple settings. Developmental and experiential factors related to preterm birth, however, may affect these HR responses. Furthermore, evaluation of ill infants in an NICU setting adds multiple contextual factors that potentially influence HR and HRV and alter their specificity as measures of pain. In some cases, it may appear that pain reactivity is reduced when, in fact, HR reactivity is only an expression of the biologic capacity to produce a response, not the presence of a response itself. The nature of the setting and the infant's health, developmental stage, and behavioral state all contribute to potentially altering HR responses to painful events in this setting. Thus, the methodology used and its application must be flexible. A variety of HRV analysis techniques may be needed to identify a variety of response patterns and mechanisms that influence pain reactivity. Furthermore, careful selection of HR epochs for stationarity, an understanding of the potential discordance between biologic and behavioral measures, the effects of medication, and an accounting for developmental differences that occur during a typical NICU course are all critical factors for investigators to be aware of. Understanding cardiovascular reactivity as a measure of response to painful events in vulnerable infants requires ongoing work.

Does parenchymal brain injury affect biobehavioral pain responses in very low birth weight infants at 32 weeks' postconceptional age?

OBJECTIVE

Children with neurologic impairments have shown diminished pain response compared with control subjects; however, it remains unclear what mechanisms underlie this response or when it develops. If this were also true with premature infants who undergo neonatal intensive care, then infants with parenchymal brain injury (PBI) would be at increased risk of underrecognition and undertreatment of procedural pain. The purpose of this study was to determine whether infants with PBI display altered responses to acute procedural pain at 32 weeks' postconceptional age (PCA), compared with control subjects.

METHODS

We compared responses to blood collection by heel lance at 32 weeks' PCA in 12 very low birth weight infants (mean [range] birth weight: 876 g [630-1240 g]; gestational age: 26.3 weeks (24-28 weeks) who had sustained PBI in the neonatal period, with 12 control subjects matched for gestational age at birth and gender (838 g [625-990 g]; 26.3 weeks [24-28 weeks[) who had normal neonatal brain imaging. PBI was defined as cerebral parenchymal infarction (grade 4 intraventricular hemorrhage) or cystic periventricular leukomalacia on serial cranial ultrasound scans conducted in the neonatal period. Biobehavioral responses to pain were measured using facial activity (Neonatal Facial Coding System) and measures of heart rate (HR) variability (low-frequency [LF] power [0.04-0.15], high-frequency [HF] power [0.15-0.8 Hz], and LF/HF ratio) as a measure of cardiac autonomic modulation. Neurodevelopmental follow-up was undertaken at 18 months.

RESULTS

The infants with PBI had significantly higher illness severity scores at day 1 compared with day 3 (Score of Neonatal Acute Physiology II: 32.1 vs 19.8) but similar previous pain experiences (109 vs 115) and total morphine exposure (0.29 vs 0.30 mg/kg). Both groups of children mounted similar responses to heel lance at 32 weeks' PCA with no difference in facial response or HR variability. Mean HR and facial action scores increased from baseline to the lance, whereas LF, HF, and the LF/HF ratio decreased significantly. No group differences were found. The only statistically significant difference between groups was that infants with PBI had more tongue protrusion at lance. Neurodevelopmental follow-up showed 8 of 11 toddlers with PBI had cerebral palsy compared with 0% of control toddlers. Psychomotor Developmental Index score on the Bayley Scales of Infant Development II was significantly lower in the PBI group. Five of 11 toddlers with PBI had Mental Developmental Index score <2 standard deviations below mean compared with 0% of the control toddlers.

CONCLUSION

Contrary to expectations, we did not find any evidence of an altered pain response pattern in infants with proven brain injury in the neonatal period. Although most infants with PBI developed cerebral palsy, these findings suggest that cerebral injury predominantly to the central white matter leaves brainstem responses intact in the neonatal period. Furthermore, it seems that the injured brain of the preterm infant has not yet expressed the identifiable differences in pain display and the functional impairment observed at later ages.

Nociceptive afferents selectively modulate the cardiac component of the peripheral chemoreceptor reflex via actions within the solitary tract nucleus

Our previous findings showed that the nucleus of the solitary tract (NTS) mediated part of the tachycardia evoked during somatic noxious stimulation. Here, we investigated the interaction between somatic nociceptor- and peripheral chemoreceptor-evoked cardiac changes. We sought to determine whether this interaction occurred within the NTS, the primary site of termination of chemoreceptor afferents. In a working heart-brainstem preparation of rat, mechanical noxious activation of a forelimb evoked a tachycardia of 17.5+/-3 (mean+/-S.E.M.) b.p.m., whereas sodium cyanide (7-30 microg) stimulation of peripheral chemoreceptors produced a sub-maximal bradycardia of -140+/-15 b.p.m. During nociceptor stimulation the sodium cyanide-evoked bradycardia was attenuated to -42.6+/-12 b.p.m. but could be prevented by a multiple bilateral NTS microinjection of bicuculline (i.e. -173+/-18 b.p.m.). Furthermore, the activity of NTS neurones responding to peripheral chemoreceptor stimulation increased from 2.8+/-1.3 to 9.4+/-1.9 Hz during sodium cyanide injection (n=7; P<0.01). The latter response was attenuated reversibly to 2.9+/-0.9 Hz during simultaneous stimulation of the brachial nerve. Pressure ejection of bicuculline abolished this inhibitory action of brachial-nerve stimulation on the chemoreceptor-evoked excitatory synaptic response. We conclude that somatic noxious stimulation attenuates the chemoreceptor reflex-evoked bradycardia via a GABA(A)ergic mechanism in the NTS.

Relations between behavioral and cardiac autonomic reactivity to acute pain in preterm neonates

OBJECTIVE

The purpose of this study was to assess relations and concordance between behavioral and physiologic reactivity to pain in preterm neonates at 32 weeks postconceptional age as a function of gestational age at birth.

SETTING

Level III neonatal intensive care unit.

DESIGN/PATIENTS

The study group comprised 136 preterm neonates (mean [range] birthweight, 1,020 g [445-1,500 g]: gestational age at birth, 28 weeks [23-32 weeks]) separated into three groups according to gestational age at birth as follows: 23 to 26 weeks (n = 48), 27 to 29 weeks (n = 52), and 30 to 32 weeks (n = 36).

OUTCOME MEASURES

Reactivity to routine blood collection at 32 weeks postconceptional age was assessed using bedside-recorded behavioral and autonomic measures. Coders who were blinded to the study design scored behavioral responses (facial activity using the Neonatal Facial Coding System, sleep/waking state, and finger splay). Autonomic reactivity was assessed by change in heart rate and spectral analysis of heart rate variability (change in low-frequency and high-frequency power, and the ratio of low-frequency to high-frequency power during blood collection).

RESULTS

Facial activity and state correlated moderately with change in heart rate across gestational age groups (r = 0.41-0.62). Facial activity and state did not correlate significantly with change in low-frequency and high-frequency power, or the ratio of low-frequency to high-frequency power (r = 0.00-0.31). Finger splay did not correlate with any autonomic recording (r = 0.03-0.41). Concordance between established biobehavioral measures of pain revealed individual differences. Although some neonates showed high behavioral but low physiologic reactivity, other neonates displayed the opposite reaction; however, the majority displayed concordant reactions.

CONCLUSIONS

The study findings confirm the value of measuring domains independently, especially in neonates born at a very young gestational age.

Role of the solitary tract nucleus in mediating nociceptive evoked cardiorespiratory responses

We compared the cardiorespiratory reflex responses evoked by noxious stimulation of the forelimb and cornea. Due to the depressant effects of anaesthesia on visceral reflexes we compared data from an unanaesthetised decerebrate rat model--the working heart-brainstem preparation (WHBP), with the anaesthetised rat. In both experimental models stimulation of the forelimb (mechanical pinch) evoked a tachycardia (WHBP: 19 +/- 2 bpm) and a decrease in respiratory cycle length (WHBP: from 4.1 +/- 0.2 to 2.3 +/- 0.1 s). The magnitude of response in anaesthetised animals depended on anaesthetic depth. Mechanical stimulation of the cornea evoked a bradycardia (-49.2 +/- 4.8 bpm) and an increase in respiratory cycle length from 4 +/- 0.36 to 5.88 +/- 0.2 s which was only present in the WHBP. In the WHBP activation of forelimb and corneal nociceptors both elicited significant pressor effects; in anaesthetised rats there were inconsistent changes in arterial pressure. To determine a role for the nucleus of the solitary tract (NTS) in mediating nociceptive evoked responses in the WHBP, synaptic transmission was blocked reversibly following bilateral microinjections of cobalt chloride. The heart rate responses evoked from either forelimb or corneal nociceptors were attenuated by approximately 50% (P < 0.05). A similar effect was observed using isoguvacine, a GABAA receptor agonist, to hyperpolarise NTS neurones. In conclusion, activation of forelimb and corneal nociceptors evoked contrasting patterns of cardiorespiratory response in the WHBP while in the anaesthetised rat the magnitude of the cardiorespiratory response to forelimb stimulation was quantitatively dependent on anaesthetic dose. In the WHBP, NTS neurones appear important for mediating the cardiac component of the reflex response following stimulation of nociceptive reflex pathways.

Demographic and therapeutic determinants of pain reactivity in very low birth weight neonates at 32 Weeks' postconceptional Age

BACKGROUND

Management of pain in very low birth weight infants is limited by a lack of empiric knowledge about the multiple determinants of biobehavioral reactivity in infants receiving neonatal intensive care.

OBJECTIVE

To examine relationship of early neonatal factors and previous medication exposure to subsequent biobehavioral reactivity to acute pain of blood collection.

DESIGN

Prospective cohort study. Methods. One hundred thirty-six very low birth weight (</=1500 g) infants who underwent heel lance for blood collection at 32 weeks' postconceptional age formed the study sample, after excluding those with significant cerebral lesions (periventricular leukomalacia or cerebral parenchymal infarction [grade 4 intraventricular hemorrhage]) on cranial ultrasound. Pain reactions were assessed using the Neonatal Facial Coding System, infant state, and spectral analysis of change in heart rate variability from baseline to reaction to invasive stimulation. Factor analysis was used to provide an empirical basis for deriving summary pain scores, one factor was primarily behavioral and the other primarily autonomic.

RESULTS

A normal reaction to procedural pain is characterized by facial grimacing and heightened cardiac sympathetic activity. The most significant factors associated with altered behavioral and autonomic pain reactivity at 32 weeks' postconceptional age were a greater number of previous invasive procedures since birth and gestational age (GA) at birth, both of which were related to a dampened response. After controlling for these variables, exogenous steroid exposure made an independent contribution to both the behavioral and autonomic pain scores, also in the direction of dampening the response. Conversely, previous exposure to morphine was associated with "normalized" (ie, increased) rather than diminished responses. In addition, higher mean heart rate at baseline was associated with lower GA at birth and longer time on mechanical ventilation.

CONCLUSION

Early pain exposure at very low GA may alter the autonomic substrate, resulting in infants who are in a perpetual state of stress. The results of this study suggest that the judicious use of analgesia may ameliorate these effects on later pain reactivity. However, although early morphine exposure may "normalize" subsequent pain reaction, this study did not examine its effects on neurodevelopment.

Spectral analysis of heart rate variability in premature infants with feeding bradycardia

An elevated level of baseline parasympathetic activity was noted in a group of premature infants suffering from bradycardia during feeding. At approximately 34 wk post-conceptional age, the heart rates of 12 infants with feeding bradycardia (birth weight = 1539 +/- 279 g; gestational age = 31.0 +/- 1.6 wk) and 10 controls (birth weight = 1710 +/- 304 g; gestational age = 32.0 +/- 1.4 wk) were recorded 1 h before and 1 h after feeding. EKG data were digitized and 3.2-min segments of data were analyzed to determine the spectral power at very low (VLF = 0.003-0.03 Hz), low (LF = 0.03-0.39 Hz), and high (HF = 0.40-1.00 Hz) frequencies. In preterm infants with feeding bradycardia, an elevation in baseline parasympathetic activity was evident before feeding, as indicated by significantly higher HF power and a lower LF/HF ratio. This elevation in baseline parasympathetic activity may contribute to the observed bradycardia during feeding.

Biobehavioral pain responses in former extremely low birth weight infants at four months' corrected age

OBJECTIVE

To compare biobehavioral responses to acute pain at 4 months' corrected age between former extremely low birth weight (ELBW) infants and term-born controls.

METHODOLOGY

Measures of facial behavioral and cardiac autonomic reactivity in 21 former ELBW infants (mean birth weight = 763 g) were compared with term-born infants (n = 24) during baseline, lance, and recovery periods of a finger-lance blood collection. Further, painful procedures experienced during neonatal care were quantified in both groups.

RESULTS

Overall, behavioral and cardiac autonomic responses to the lance were similar between groups. However, the ELBW group seemed to have a less intense parasympathetic withdrawal in the lance period and a more sustained sympathetic response during recovery than the control group. Further, in the recovery period, two behavioral patterns (early recovery and a late recovery) were apparent among the ELBW group.

CONCLUSIONS

Biobehavioral pain responses were similar overall between both groups of infants. Subtle differences were observed in cardiac autonomic responses during the lance period and in behavioral recovery among ELBW infants. Whether these findings represent a long-term effect of early pain experience or a developmental lag in pain response remains unclear. The lack of an overall difference runs counter to previously reported findings of reduced behavioral response in former ELBW infants. biobehavioral pain response, premature infants, repetitive pain, heart rate variability.