The neuroanatomy, neurophysiology, and neurochemistry of pain, stress, and analgesia in newborns and children

Prevention and management of pain and stress in the neonate

This statement is intended for health care professionals caring for neonates (preterm to one month of age). The objectives of this statement are to: increase awareness that neonates experience pain; provide a physiological basis for neonatal pain and stress assessment and management by health care professionals; make recommendations for reduced exposure of the neonate to noxious stimuli and to minimize associated adverse outcomes; and recommend effective and safe interventions that relieve pain and stress.

Pain assessment and management in the newborn infant

Managing the pain of a newborn is both complex and challenging because of the subtlety of pain expression in these patients and their vulnerability. This article provides an overview of the physiology of pain in the newborn, addresses pain assessment and pain-assessment tools, explores both nonpharmacological and pharmacological approaches to pain management, and finally, lays the responsibility for pain management in the newborn squarely in the lap of the professional.

Randomised trial of analgesic effects of sucrose, glucose, and pacifiers in term neonates

OBJECTIVES

To assess and compare the analgesic effects of orally administered glucose and sucrose and pacifiers. To determine the synergistic analgesic effect of sucrose and pacifiers.

DESIGN

Randomised prospective study with validated behavioural acute pain rating scale.

SETTING

Maternity ward.

PARTICIPANTS

150 term newborns undergoing venepuncture randomly assigned to one of six treatment groups: no treatment; placebo (2 ml sterile water); 2 ml 30% glucose; 2 ml 30% sucrose; a pacifier; and 2 ml 30% sucrose followed by a pacifier.

RESULTS

Median (interquartile) pain scores during venepuncture were 7 (5-10) for no treatment; 7 (6-10) for placebo (sterile water); 5 (3-7) for 30% glucose; 5 (2-8) for 30% sucrose; 2 (1-4) for pacifier; and 1 (1-2) for 30% sucrose plus pacifier. Mann-Whitney U test P values for comparisons of 30% glucose, 30% sucrose, pacifier, and 30% sucrose plus pacifier versus placebo (sterile water) were 0.005, 0.01, <0.0001, and <0.0001, respectively. Differences between group median pain scores for these comparisons were 2 (95% confidence interval 1 to 4), 2 (0 to 4), 5 (4 to 7), and 6 (5 to 8), respectively. P values for comparisons of 30% glucose, 30% sucrose, and 30% sucrose plus pacifier versus pacifier were 0.0001, 0.001, and 0.06, respectively. Differences between group medians for these comparisons were 3 (2 to 5), 3 (1 to 5), and 1 (0 to 2), respectively.

CONCLUSION

The analgesic effects of concentrated sucrose and glucose and pacifiers are clinically apparent in newborns, pacifiers being more effective than sweet solutions. The association of sucrose and pacifier showed a trend towards lower scores compared with pacifiers alone. These simple and safe interventions should be widely used for minor procedures in neonates.

Factors explaining lack of response to heel stick in preterm newborns

OBJECTIVE

To determine factors explaining lack of response by preterm newborns to heel stick for blood sampling.

DESIGN

A cross-sectional design based on secondary analysis of the control session of a randomized crossover design.

SETTING

Four Level III neonatal intensive-care units of university teaching hospitals.

PARTICIPANTS

120 preterm newborns with an average age of 28 weeks postconceptional age.

INTERVENTION

24 newborns who showed a "no change" response according the Premature Infant Pain Profile were compared to the remaining 96 newborns who had shown a pain response.

MAIN OUTCOME MEASURES

Age (postconceptional age at birth, postnatal age at study), Apgar score at 5 minutes, severity of illness, sex, race, wake/sleep state, previous study sessions, total number of painful procedures since birth, and time since last painful procedure.

RESULTS

After stepwise logistic regression analysis the variables remaining in the final model that explained the difference between the groups were postnatal age at time of study, postconceptional age at birth, time since last painful procedure, and wake/sleep state.

CONCLUSIONS

Newborns who were younger, asleep, and had undergone a painful event more recently were less likely to demonstrate behavioral and physiologic indicators of pain.

Pain in neonate

Anatomical, functional and neurochemical maturation of pain pathways is well developed in fetus and neonates. Various physiological and behavioural responses to painful stimuli in neonates substantiate their ability to feel pain. Biological effects of pain are systematically studied in human fetus and neonates. Pain expressions in the newborn not only reflect tissue damage but are a function of ongoing behavioural state. The ultimate aim should be to keep neonates free from pain and other stressful stimuli as far as possible, by advocating minimal handling protocol, giving comforts after painful procedures, local anesthesia while carrying out painful procedures like cutdown and insertion of chest tubes, and if a baby is ventilated fentanyl and/or midazalam infusion must be carried out during initial periods of ventilation.

The systemic stress response to thermal injury in children

OBJECTIVE

Thermal injury is extremely stressful, but data characterizing the endocrine stress response to this injury in children are sparse. The objective of this study was to measure the effects of thermal injury on the levels of stress hormones in children and to assess the temporal changes associated with them.

PATIENTS

Twenty-three children, 13 girls and 10 boys aged between 5 months and 12 years 3 months (mean, 2 years 11 months), with burns covering 10-61% of their body surface (mean, 20.5%) were studied during the first 5 days following injury.

MEASUREMENTS

The levels of arginine vasopressin, angiotensin II, cortisol, adrenaline, noradrenaline and dopamine were measured in sequential blood samples obtained from thermally injured children on admission and at specified time intervals during the 5 days of the investigation.

RESULTS

At admission the concentrations of all the hormones were high, and varied widely between individual patients. The geometric mean and 95% confidence intervals of admission hormone levels were as follows: arginine vasopressin 18.3 (8.3-40.7) pmol/l; angiotensin II 122.0 (56.0-266.2) pmol/l; cortisol 650.6 (473.0-895.0) nmol/l; dopamine 1.0 (0.1-8.0) nmol/l; adrenaline 6.4 (3.2-12.5) nmol/l and noradrenaline 2.3 (1.3-4.3) nmol/l. Although the concentrations of arginine vasopressin and cortisol returned to normal 24 to 36 h after admission, the levels of angiotensin II, adrenaline and dopamine fluctuated and remained higher than normal throughout the study (108 h).

CONCLUSIONS

Thermal injury results in the release of abnormally high levels of stress hormones in children. Although there are similarities between some of the data reported here and those reported in adults, higher levels of adrenaline and lower levels of noradrenaline than reported in adults suggest important differences too. These differences may need to be taken into account in the management of burn-injured children.

A comparison of the effects of patients' pain on nurses working in burns and neonatal intensive care units

Nurses are more likely than other health professionals to be exposed to individuals who suffer severe pain for extended periods of time. Such exposure is likely to arouse emotional distress which not only has implications for their occupational health but may interfere with their ability to manage pain effectively. This study compared the emotional reactions to their patients' pain, of nurses who were exposed to patients with severe and obvious pain (nurses working in burns units) and nurses whose patients' pain is uncertain because they are unable to communicate (nurses working in neonatal intensive care units). The results showed that pain generated greater anxiety in nurses caring for patients with severe burns, but that they also demonstrated a greater sense of personal competence and control over the management of their patients' pain. The findings also showed that when dealing with patients' pain the morale of nurses was linked to: (a) perceived challenges to their images of themselves as alleviators of pain; (b) the extent to which their sense of personal vulnerability was aroused by contact with patients experiencing severe pain; (c) their beliefs about their ability to assess patients' pain; and (d) the quality of their professional relationships with the medical staff who controlled the most powerful forms of pain relief.

Analgesia in newborns given oral glucose

There is evidence that newborn babies feel pain even at the lowest gestational ages when they can survive. Because sweet solutions such as sucrose, given orally, may relieve pain in neonates, we decided to compare the effects of two concentrations of glucose (normally used for intravenous infusions) and of breast milk in a randomized controlled trial in 120 babies requiring heel-prick tests. Glucose solutions and breast milk are readily available in the neonatal department. No other treatment was given. Our results strongly suggest that 1 ml of a 30% glucose solution given orally alleviates mild pain significantly and can be used for this purpose in newborns. Breast milk and 10% glucose did not have a similar effect.

Expressão Facial Como Acesso À Consciência do Recém-Nascido

Este artigo propõe uma reflexão a respeito do uso de movimentos expressivos como indicadores de estados subjetivos no bebê recém-nascido, a partir de registros de reações a estímulos nociceptivos e a estímulos olfativos e gustativos. A análise dessas reações (choro e expressões faciais de agrado e desagrado) evidencia sintonia com o ambiente e variabilidade individual - duas condições implicadas no sentido de consciência como "awareness"- e exclui a possibilidade de uma interpretação desses movimentos como reações reflexas. Considerando-se o bebê como ser social e altamente comunicativo, estas evidências permitem admitir uma correspondência estreita entre movimentos expressivos e estados internos, um pressuposto comum às teorias de emoção.

Recurrent abdominal pain in children: a review of psychological factors and treatment

This paper reviews current knowledge regarding recurrent abdominal pain (RAP) and the physiological, dietary, and psychological variables that may have some influence in pain episodes. Emphasis is placed on psychological factors and studies that have investigated psychological treatment modalities. There is some limited evidence of physiological dysfunction in RAP patients, and while some researchers have asserted that RAP may be a dietary disorder, results of several studies do not support this assertion. Studies examining psychological variables in RAP patients show elevated anxiety levels; however, elevated anxiety is also associated with organic abdominal pain. Psychological treatments focusing on cognitive-behavioral methods have demonstrated success in treating RAP. Follow-up studies are needed to determine the long-term success of these treatments, and continued research examining which children benefit from treatment would also be beneficial.

Pain management in newborns: how far have we progressed in research and practice?

Compelling research supports the newborn infant's capacity for pain. Yet, pain is frequently underestimated and undertreated. This is a result of limited understanding of pain pathway development, immediate and long-term consequences, measurement tools and approaches, and safety and efficacy of pain-relieving interventions. This paper reviews recent research in relation to management of pain in the newborn, and presents implications for practice and future research.

[Anatomical route of pain in premature newborn infants]

Recent research about nociceptive pathways in newborn infants have shown that, even very immature, preterm infants have all the anatomical and functional components required for the perception of painful stimuli. However, the perception of pain in preterm infants is thought to be slightly different from that of term infants: because of a lack of myelination of their sensitive fibers and a still immature cortical organization of the somatosensory system, painful stimuli are perceived more widespread and durable. In addition, the threshold of pain seems to be lower in premature infants, probably due to a lack of protection of their spinal and supraspinal inhibitory pathways. Finally, abnormal behavioural imprinting secondary to early painful stimuli is now suggested. Thus in contrast with the former misconception of "insensitivity towards pain", premature infants must be now considered as "hypersensitive" and vulnerable.

Oral sweet solution reduces pain-related behaviour in preterm infants

To evaluate the effectiveness of oral sucrose in the prevention of pain-induced crying in preterm infants, a sample of 28 healthy neonates (15M, 13F; gestational age at procedure less than 37 weeks) who were having routine blood drawn by arm venipuncture was studied. Infants were randomly allocated to receive by mouth, using a syringe, 2 ml of one of three solutions: spring water (group W) and sucrose 12 and 24% w/v (groups S12 and S24, respectively), all in water vehicle. After 2 min, while awake, arm venipuncture was performed and duration of crying was measured. The time spent crying was reduced in the group treated with the sweetest solution (S24, n = 8, mean = 19.1 s). No difference was observed between the S12 group (n = 8, mean = 63.1 s) and W group (n = 12, mean = 72.9 s). Physiological measurements were recorded at different time points to evaluate excessive basal and procedural distress.

Cosmetic tail docking of dogs

The anatomy of the canine tail and its relationship to the physiological functions of the tail are described and the effect of tail docking on these is discussed. Current knowledge on the physiology and anatomy of pain is described with particular reference to cosmetic tail docking in the neonatal puppy. Recent advances in knowledge about pain and the changes in approach to pain management, refute the premise that 'puppies do not feel pain therefore tail docking is not inhumane' and also the premise that 'the pain and the effects of tail docking are insignificant.' Six criteria to test the 'necessity' to dock dogs are presented; this article shows that the reasons advanced for tail docking do not satisfy these criteria and so that docking dogs' tails cannot be justified.

Effects of fentanyl administration on general and cerebral haemodynamics in sick newborn infants

Despite the wide use of fentanyl for analgesia in newborns, concerns have been raised about potential haemodynamic side-effects. Since sick newborns may lose their cerebral blood flow autoregulation, a drug-induced haemodynamic instability could lead to brain injury. We assessed the effects of a 15-min infusion of fentanyl (3 micrograms/kg) on the general and cerebral haemodynamics in 15 newborns (median gestational age 29 weeks, 25th-75th percentile, range 28-31 weeks; birthweight 1170 g, range 955-1790 g). The heart rate and mean arterial blood pressure were continuously recorded. Mean cerebral blood flow velocity and pulsatility index were measured using pulsed Doppler ultrasound before, during and up to 60 min after the onset fentanyl administration. No significant modification of general or cerebral haemodynamics was observed. In conclusion, the infusion of 3 micrograms/kg of fentanyl did not lead to any deleterious effect on the general or cerebral haemodynamics in sick normovolaemic newborns.

Premature Infant Pain Profile: development and initial validation

OBJECTIVE

Inadequate assessment of pain in premature infants is a persistent clinical problem. The objective of this research was to develop and validate a measure for assessing pain in premature infants that could be used by both clinicians and researchers.

DESIGN

The Premature Infant Pain Profile (PIPP) was developed and validated using a prospective and retrospective design. Indicators of pain were identified from clinical experts and the literature. Indicators were retrospectively tested using four existing data sets.

PATIENTS AND SETTINGS

Infants of varying gestational ages undergoing different painful procedures from three different settings were utilized to develop and validate the measure.

METHODS AND RESULTS

The largest data set (n = 124) was used to develop the PIPP. The development process included determining the factor structure of the data, developing indicators and indicator scales and establishing internal consistency. The remaining three data sets were utilized to establish beginning construct validity.

CONCLUSIONS

The PIPP is a newly developed pain assessment measure for premature infants with beginning content and construct validity. The practicality and feasibility for using the PIPP in clinical practice will be determined in prospective research in the clinical setting.

Special needs of preterm infants in the management of pain and discomfort

Most infants born preterm are admitted to hospital neonatal intensive care units, where they undergo repeated multiple diagnostic and therapeutic procedures that result in pain and discomfort. Although there is convincing evidence to support the preterm infant's neurologic capacity for pain, management of pain often is not optimal. Accurate and reliable assessment of the preterm infant's pain is an important prerequisite for effective pain management. Pain assessment is a challenge for health professionals because the preterm infant's responses are less vigorous, more variable, and less consistent than are the responses of term neonates and older infants. Few reliable and valid assessment measures exist for this age group. There also is uncertainty in implementing pain-relieving intervention because of inadequate information on their safety and effectiveness and preconceived attitudes and beliefs of health professionals. The special needs of preterm infants related to the assessment and management of pain are discussed.

Issues of assessment of pain and discomfort in neonates

Pain assessment in neonates often presents problems. The problem of inadequate or inaccurate assessment is complicated by issues related to the nature, consistency, and variability of the infant's physiologic and behavioral responses; the reliability, validity, specificity, sensitivity, and practicality of existing neonatal pain measures or measurement approaches; ethical questions about pain research in infants; and uncertainty about the responsibilities of health care professionals in managing pain in clinical settings. Despite these many issues, neonates need to be comfortable and as free of pain as possible to grow and develop normally. Valid and reliable assessment of pain is the major prerequisite for attaining this goal. Issues embodied in neonatal pain responses, measurement, ethical, and clinical considerations are explored. Suggestions for resolving some of these problems are presented.

[Use of EMLA cream in premature and full-term newborn infants. Study of efficacy and tolerance]

BACKGROUND

Mild methemoglobinemia is a known side-effect of one of the constituents of EMLA cream, this topical local anesthetic is used with great caution in neonates.

POPULATION AND METHODS

One hundred and sixteen neonates admitted from January to July 1994 in an intensive care unit were included in the study. All required skin punctures which were performed 1 h 30-2 hours after EMLA had been applied on the skin. A reaction score (0 to 5) to skin puncture was established 157 times (120 after and 37 without local anesthesia); methemoglobin (Met Hb) concentrations were measured in 47 blood samples, 18-24 hours (40.4% of samples) or 2-3 days (36.2%) after application of EMLA.

RESULTS

Ninety-four neonates were quiet before puncture (score 0-1). Among them, 57% of those who were given EMLA had a low score (2 or less) vs 18% without EMLA. A low reaction was observed in 65% when the dressings had been kept in place for at least 90 minutes vs 15% with a shorter application. A lower reaction was noted in 78.8% of cases after venopuncture (41% after arterial puncture). No Met Hb level was above 5% and 7 (15%), in five neonates, were between 3 and 5%. There was no clear relationship between methemoglobinemia and gestational age or duration of dressing.

CONCLUSION

EMLA cream is effective and safe in neonates including preterms, when it is applied in a small amount once a day.

Effects of morphine, pentobarbital and amphetamine on formalin-induced behaviours in infant rats: sedation versus specific suppression of pain

The behavioural response of infant rats to intraplantar injection of formalin consists of specific directed behaviours (limb flexion, shaking and licking the injected paw) and non-specific behaviours that are also induced by non-nociceptive stimulation (squirming, hind limb kicks and whole body jerks), with specific indicators becoming more frequent as pups mature. The present study examined the effects of systemic morphine, pentobarbital and D-amphetamine on formalin-induced behaviours and behavioural state in rat pups from 1 to 20 days of age. Morphine (1 mg/kg) almost completely suppressed both specific and non-specific indicators of pain, and produced mild sedation relative to handled control pups. Pentobarbital (10 mg/kg) produced a similar degree of sedation and suppression of non-specific measures as morphine, but only had weak effects on specific measures in pups less than 1 week old, and no effects thereafter. Suppression of both specific and non-specific pain measures after amphetamine (2 mg/kg) emerged during the 2nd week of life and was not associated with sedation. Thus, morphine produced behavioural analgesia in infant rats in a model of injury-induced inflammatory pain from the 1st postnatal day, when their neurological maturity is similar to a 25-week human fetus, and 1 week before antinociception is observed in thermal and pressure tests. The effects of morphine were qualitatively different from a sedative dose of pentobarbital. The data support the contention that opioids have specific analgesic effects in premature human neonates and underline the need for pain measures that discriminate between sedation and analgesia.

Facilitated tucking: a nonpharmacologic comfort measure for pain in preterm neonates

OBJECTIVE

To identify the effectiveness of "facilitated tucking," a nonpharmacologic nursing intervention, as a comfort measure in modulating preterm neonates' physiologic and behavioral responses to minor pain.

DESIGN

Prospective, repeated measure, random sequencing, and experimental.

SETTING

Level III neonatal intensive-care unit of a tertiary care university pediatric hospital.

PARTICIPANTS

Thirty preterm neonates, 25-35 weeks gestation.

INTERVENTIONS

Heart rate, oxygen saturation, and sleep state were recorded 12 minutes before, during, and 15 minutes after two heelsticks, one with and one without facilitated tucking.

HYPOTHESIS

Premature neonates will have less variation in heart rate and hemoglobin oxygen saturation, shorter crying and sleep disruption times, and less fluctuation in sleep states in response to the painful stimulus of a heelstick with facilitated tucking than without.

RESULTS

Neonates demonstrated a lower mean heart rate 6-10 minutes post-stick (p < 0.04), shorter mean crying time (p < 0.001), shorter mean sleep disruption time (p < 0.001), and fewer sleep-state changes (p = 0.003) after heelstick with facilitated tucking than without.

CONCLUSION

Facilitated tucking is an effective comfort measure in attenuating premature neonates' psychologic and behavioral responses to minor pain.

Plasma beta-endorphin levels and childhood intussusception

To determine whether childhood intestinal intussusception is associated with elevated plasma beta-endorphin levels, a series of patients was studied prospectively. Fourteen patients (age range between 3 months and 7 years) presented to two university pediatric emergency departments in Chicago with clinical symptoms and signs of intussusception. Venous blood (2cc) was withdrawn for plasma beta-endorphin determination, followed by barium enema. Plasma beta-endorphin levels were measured by radioimmunoassay. The mean beta-endorphin level of the 8 patients with barium enema proven intussusception was 14.1 +/- 12.0 pg/ml. Two of these patients presented with marked lethargy and had beta-endorphin levels of 7.5 and 21.2 pg/ml. The mean plasma beta-endorphin level of the 5 patients with negative barium enema studies was 18.1 +/- 10.0 pg/ml (P = 0.56). A sixth control patient had a plasma beta-endorphin level of 1569 pg/ml. In conclusion, childhood intestinal intussusception is not associated with elevated plasma beta-endorphin levels.

Factors that influence the behavioral pain responses of premature infants

The responses of preterm neonates to acute tissue-damaging stimuli have been described. However, factors which influence these responses have received little attention. In this study, we observed 124 premature infants before, during and after a routine heel lance and determined how two contextual variables (severity of illness and behavioral state) influenced their behavioral responses. Significant changes in facial actions occurred between baseline and the most invasive phase of the heel lance procedure, stick. The fundamental frequency, harmonic structure and peak spectral energy of the infant's cry were also significantly increased during the stick phase. Behavioral state was found to influence the facial action variables and severity of illness modified the acoustic cry variables. Accurate identification of pain in premature infants requires consideration of factors that influence their response.

Plasma beta-endorphin concentrations and analgesia-muscle relaxation in the newborn infant supported by mechanical ventilation

We evaluated the effects of pancuronium and opiates on plasma beta-endorphin concentrations in 25 infants supported by mechanical ventilation. Infants receiving opiate were randomly assigned to receive either fentanyl or morphine. There was no change in beta-endorphin concentrations after administration of pancuronium, whereas both fentanyl and morphine reduced beta-endorphin concentrations by approximately 60%.

Alleviation of the pain of heel prick in preterm infants

The hypothesis that the variability of physiological parameters may indicate pain or stress in the neonate was examined. Four parameters (heart rate, respiratory rate, transcutaneous oxygen tension, and carbon dioxide tension) were examined over a 2 minute epoch in response to a heel prick in an attempt to measure stress/pain in 35 preterm newborn infants (26-34 weeks' gestation) half of whom were receiving intensive care. The change in absolute values of these parameters did not discriminate a dummy procedure without prick from the actual procedure containing the prick (paired t test), but the variability of the parameters during an epoch showed significant discrimination. Three procedures were evaluated to reduce this distress using unpaired t test. The use of local anaesthetic cream was not successful. The components of the mixture cause vasoconstriction that would reduce blood flow to the heel and lead to more squeezing which is likely to be painful in the presence of tissue damage. A nurse comforting the infant with tactile and vocal stimulation was slightly helpful but the use of a spring loaded lance was most successful in reducing the distress. The use of spring loaded lances may be more humane for heel pricks.

Multidimensional pain assessment in premature neonates: a pilot study

OBJECTIVE

To describe the physiologic and behavioral responses of premature neonates to a painful stimulus.

DESIGN

Descriptive.

SETTING

Secondary-level neonatal unit in a large metropolitan university teaching hospital.

PARTICIPANTS

Forty neonates between 32 and 34 weeks' postconceptual age and less than 5 days' postnatal age.

MAIN OUTCOME MEASURES

Physiologic (heart rate, oxygen saturation, and intracranial pressure) and behavioral (facial expression and cry) outcomes observed during a routine heel stick.

RESULTS

Physiologic responses were significant, but were not specific to pain. Behavioral responses were more promising and indicated that premature neonates were capable of responding in a manner similar to full-term neonates.

CONCLUSIONS

Premature neonates are capable of expressing their pain in a manner similar to healthy, full-term neonates. Factors that alter this response were not clearly delineated. Further research is needed to determine more precise patterns of response in this age group.

The pharmacokinetics and physiological effects of buprenorphine infusion in premature neonates

1. The pharmacokinetics and physiological effects of buprenorphine were studied in 12 newborn premature neonates (27 to 32 weeks gestational age) who were given a loading dose of 3.0 micrograms kg-1 of buprenorphine followed by an intravenous infusion of 0.72 micrograms kg-1 h-1 of buprenorphine. Plasma concentrations of buprenorphine were measured during the infusion, at steady-state and for 24 h after the cessation of the buprenorphine infusion. 2. The mean steady-state plasma buprenorphine concentration (+/- s.d.) for an infusion rate of 0.72 micrograms kg-1 h-1 was 4.3 +/- 2.6 ng ml-1. 3. Buprenorphine clearance was 0.23 +/- 0.07 l h-1 kg-1, the elimination half-life was 20 +/- 8 h and the volume of distribution was 6.2 +/- 2.11 l kg-1. 4. Small but significant falls were noted in systolic blood pressure at 6 h and heart rate at 1, 6 and 12 h after the administration of buprenorphine, but these did not appear to cause any clinical deterioration. 5. Four of the 12 subjects studied required an increase in the infusion rate of buprenorphine to achieve adequate sedation. 6. The results suggest that this dosing regimen of buprenorphine is safe but may not be as effective as other opioids in producing sedation and analgesia in premature newborns.

Preterm infants in pain: nurses' and physicians' perceptions

Within the past few years, the assumption that preterm infants experience little or no pain has been challenged in nursing and medical literature. It is not clear to what extent changes have taken place in the practice area. The purpose of this qualitative study was to explore the beliefs of NICU nurses and physicians about the existence and treatment of pain in preterm infants. Respondents to the open-ended interviews were 5 neonatologists and 10 nurses at two regional referral neonatal intensive care units in North Carolina. Interviews took from 20 to 40 minutes and were analyzed using the Ethnograph program. All respondents agreed that preterm infants experience pain. Both groups identified behavioral and physiological cues to pain recognition. There were differences in initial approaches to treatment. However, both groups indicated that the nurse has the pivotal role in recognition and initiation of treatment to reduce or eliminate pain.

Pain in the preterm neonate: behavioural and physiological indices

The impact of invasive procedures on preterm neonates has received little systematic attention. We examined facial activity, body movements, and physiological measures in 56 preterm and full-term newborns in response to heel lancing, along with comparison preparatory and recovery intervals. The measures were recorded in special care and full-term nurseries during routine blood sampling. Data analyses indicated that in all measurement categories reactions of greatest magnitude were to the lancing procedure. Neonates with gestational ages as short as 25-27 weeks displayed physiological responsivity to the heel lance, but only in the heart rate measure did this vary with gestational age. Bodily activity was diminished in preterm neonates in general, relative to full-term newborns. Facial activity increased with the gestational age of the infant. Specificity of the response to the heel lance was greatest on the facial activity measure. Identification of pain requires attention to gestational age in the preterm neonate.

Developmental changes in pain expression in premature, full-term, two- and four-month-old infants

The purpose of this study was to examine the behavioural responses of infants to pain stimuli across different developmental ages. Eighty infants were included in this cross-sectional design. Four subsamples of 20 infants each included: (1) premature infants between 32 and 34 weeks gestational age undergoing heel-stick procedure; (2) full-term infants receiving intramuscular vitamin K injection; (3) 2-month-old infants receiving subcutaneous injection for immunisation against DPT; and (4) 4-month-old infants receiving subcutaneous injection for immunisation against DPT. Audio and video recordings were made for 15 sec from stimulus. Cry analysis was conducted on the first full expiratory cry by FFT with time and frequency measures. Facial action was coded using the Neonatal Facial Action Coding System (NFCS). Results from multivariate analysis showed that premature infants were different from older infants, that full-term newborns were different from others, but that 2- and 4-month-olds were similar. The specific variables contributing to the significance were higher pitched cries and more horizontal mouth stretch in the premature group and more taut tongue in the full-term newborns. The results imply that the premature infant has the basis for communicating pain via facial actions but that these are not well developed. The full-term newborn is better equipped to interact with his caretakers and express his distress through specific facial actions. The cries of the premature infant, however, have more of the characteristics that are arousing to the listener which serve to alert the caregiver of the state of distress from pain.

Neonatal pain: a comprehensive survey of attitudes and practices

We surveyed 352 physicians board certified in neonatal-perinatal medicine on their attitudes and practices in the area of pain and pain management in neonates and infants. In contrast to earlier surveys of this type, almost all respondents indicated that even the youngest and most premature infants are able to perceive pain, and most reported that they always advocated anesthesia during the intraoperative period. The use of analgesic agents in the postoperative period, however, was more variable. Respondents who indicated that neonates perceived less pain than adults reported seeing fewer signs of pain and using less analgesia in the postoperative period. They were also more likely to believe that analgesics are too dangerous to use in neonates and that physiologic factors such as incomplete myelination of the pain pathways and neural/physical immaturity (factors now known not to play a role) contribute to diminished pain sensitivity. Conversely, respondents who indicated that neonates do not perceive less pain than adults, the majority of respondents, reported seeing more signs of pain and using more medication in the postoperative period. These physicians also believed that the physiologic stress associated with pain can be more dangerous than the analgesics. We conclude that attitudes and reported practices have changed in the area of neonatal pain and pain management. Furthermore, our data indicate that these attitudes significantly predict reported postoperative medicating practices.

[Drug treatment for pain in children and elderly persons.]

The subject of treatment of pain in children and elderly patients has been neglected to date. This symposium deals with the problems of pain treatment in these two age groups and shows the importance of adequate therapy to improve their quality of life.

The behavioral response to formalin in preweanling rats

The behavioural response of rat pups, 1-20 days of age, to subcutaneous injection of formalin in a rear paw is described. Formalin-injected pups were compared to handled controls and to pups that received an injection of normal saline. Ongoing behaviour was recorded every 2 min for 60 min after injection. Injection of normal saline produced little disorganization of behaviour, although day-1, -3 and -6 pups did frequently flex the limb on the injected side early in the session. Injection of 10 microliters of 1% formalin depressed active and quiet sleep in pups 10 days old and younger. Much less disruption of sleep was observed in day-15 pups, and in day-20 pups it was necessary to increase the concentration of formalin to 2.5% to produce a consistent behavioural response. The specific responses of pups to formalin injection were flexion of the limb, shaking the limb, and licking the injected paw. Pups of all ages displayed all of these responses, but in pups younger than 10 days, only limb flexion was consistent. Shaking became a consistent response in day-10 pups and licking in day-15 and -20 pups. Non-specific behaviours (squirming, vigorous rear kicks with both hind limbs and convulsive whole body jerks) were markedly increased by formalin in younger pups with a developmental pattern: squirming and kicking in day-1 pups, kicking and jerking in day-3 to -15 pups. Non-specific behaviours decreased and specific behaviours increased with age. In addition, the overall intensity and duration of the response decreased with age. The biphasic time course of the response of adult rats to formalin injection did not appear until 15 days of age.

Pain perception in the neonate: implications for circumcision

Routine neonatal circumcision is still performed in most centers without the benefit of anesthesia. The authors give a review of the anatomy and physiology of the pain response as it relates to newborns, and discuss the growing body of literature regarding the ability of these very young patients to perceive pain. The discussion focuses on the relevance of this information to the controversial issue of the use of anesthesia during circumcision.