Pain and its effects in the human neonate and fetus

Pain during burn dressing change in children: relationship to burn area, depth and analgesic regimens

To determine the level of pain that acutely burned children experience, we obtained pain scores before, during and after burn dressing change (BDC). Pain scores were higher during the BDC, consistent with severe pain during this procedure. A positive correlation between pain scores and the body surface area (BSA) burned suggests that pain increases with the size of the burn. Contrary to widely held beliefs, comparison of mean pain scores and the percent of 3rd degree burn revealed that the larger the area of full-thickness injury, the greater the pain. Regardless of wide variations in patient characteristics, fixed doses of oral narcotics were usually prescribed for pain. Patients with BSA greater than 70% experienced severe pain during BDC despite the type, dose or route of opioids. These findings suggest the need for (a) education to correct the myth that 'third-degree burns don't hurt'; (b) revision of analgesic prescribing patterns in the burned child; and (c) research to determine the mechanisms (e.g., tolerance or deafferentation) underlying the opioid-resistant nature of pain after large burns.

Diamorphine infusion in the preterm neonate

The effects of diamorphine were studied in 34 premature neonates who were given a loading dose of 50 micrograms/kg of diamorphine followed by a constant rate intravenous infusion of 15 micrograms/kg/hour. Small but significant falls were noted in blood pressure (at 30 minutes) and heart rate (at 30 minutes, six hours, and 12 hours) after administration of diamorphine, but these did not appear to cause any clinical deterioration and were thought to be related to the sedative effect of the drug. A significant fall in respiration rate at 30 and 60 minutes reflected the desired intention to encourage synchronisation of the infants' breathing with the ventilator. The mean (SD) plasma concentration of morphine measured during the infusion at steady state was 62.5 (22.8) ng/ml (range 20 to 98 ng/ml). The data suggest that this dosage regimen of diamorphine is safe. It results in plasma concentrations of morphine in the premature neonate which are comparable with those that are known to provide effective analgesia in the child and adult.

Pain in neonatal circumcision

Because newborn circumcision is a quick and safe surgical procedure, any method to relieve pain must be almost risk-free in order to be acceptable. General anesthesia and narcotic analgesia are not appropriate. Dorsal penile nerve block (DPNB) with lidocaine hydrochloride is probably the most effective and safest form of anesthesia for newborn circumcision currently available, but it can cause significant local and systemic reactions. Only a limited number of cases of DPNB have been reported and we feel that this procedure should be used cautiously until there is more published evidence of its safety. Alternative methods of pain relief including oral acetaminophen and topical anesthesia should also be studied. Of special interest is recent evidence that a sucrose-flavored pacifier is an effective analgesic during newborn circumcision.

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.

The pain response of the postoperative newborn

The amount of pain experienced by the postoperative newborn remains one of the most challenging problems in neonatology. In this study, ethological methods were used to examine behaviours for 12 hours, commencing 24 hours postoperatively in three male full-term infants following chest surgery. The infants' facial expressions, body postures and movements were coded each minute from videotapes. The infants' heart rates and respiratory rates were also continuously recorded. Behavioural data were analysed using descriptive statistics and factor analysis. The six-factor solution accounted for 61.6% of the variance and identified indices of acute distress, subacute pain, quiet alertness, drowsiness and sleeping. Changes were evident when comparing behavioural or physiological variables before and after the administration of analgesia, treatments, nursing care or environmental noise. The authors conclude that ethological methods are appropriate to examine this problem, and recommend that the study be replicated.

The comforting behaviors of caregivers toward distressed postoperative neonates

The comforting behaviors of nurses caring for four postoperative neonates were examined by analyzing 40 hours of videotaped caregiving. Using the techniques of qualitative ethology, 30 periods of distress were identified. During these periods, 98 episodes of direct tactile and verbal comforting occurred. The types and patterns of comforting touch are delineated. Observations revealed that comforting occurs in response to infant cues, comfort touch had limited effect in settling the infants, infants were often distressed for long periods without being comforted, and the infants were handled as normal infants without regard for their incisions. Suggestions for further research are presented.

Hormonal and metabolic response to operative stress in the neonate

It is evident from this review that newborns, even those born prematurely, are capable of mounting an endocrine and metabolic response to operative stress. Unfortunately, many of the areas for which a relatively well-characterized response exists in adults are poorly documented in neonates. As is the case in adults, the response seems to be primarily catabolic in nature because the combined hormonal changes include an increased release of catabolic hormones such as catecholamines, glucagon, and corticosteroids coupled with a suppression of and peripheral resistance to the effects of the primary anabolic hormone, insulin.

[Acute pain in children and its treatment]

Pain in paediatrics has long been underestimated. The numerous scientific studies carried out during the last decade show that its existence can no longer be doubted: in fact, pain already exists during the neonatal period, and probably throughout the last trimester of gestation as well. Pain pathways mature during the embryonic period and peripheral receptors develop between the 7th and 20th week. A-delta and C fibers, as well as spinal roots and nerves, are completely differentiated before the end of the second month. The development of specific neurotransmitters and thalamic and cortical dendritic branching occurs later on; it is well enough developed to allow perception of painful stimuli (slow or protopathic component) from the beginning of the foetal period onwards. The discriminative rapid component develops in parallel to myelinisation, and the psycho-affective component, which requires a long and complex learning process, will not be fully operative until the end of puberty. Assessing pain, already a difficult task in the adult, is all the more so in children because of lesser verbal communicative capabilities, difficulty in handling abstract concepts, lack of experience of painful stimuli to make comparisons, and ignorance of their body image. In the very young child, diagnosing pain relies on suggestive circumstances, and an altered behaviour, knowing that no one symptom in pathognomonic. As the child grows up, methods for self-assessment of pain become usable, such as coloured scales and simplified verbal scales. However, behavioural tests remain the mainstay until the prepubertal period. The treatment of acute pain requires a reasoned approach which takes into account the state of the child, that of the aetiological investigations, the likely course of the lesions, as well as the patient's analgesic requirements. Therapeutic means do not differ from those for adult patients; however, the differences of distribution of body water, the small possibilities of linking with plasma proteins, and limited conjugation with glucuronate must be taken into account, especially during the first months of life. Local and regional anaesthetic block techniques are of great interest in elective and emergency surgery, as well as in trauma: they can provide complete pain relief, mostly without having any effect on the patient's physiological state (haemodynamics and consciousness). Peripherally acting analgesic agents, which are well supported on the whole, as well as co-analgesics, have a great part to play, although there are less drugs available than for adults. The most useful ones are paracetamol, followed by the salicylates, propionic acid derivatives and non steroid anti-inflammatory drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Epidurography in premature infants

A caudal epidural catheter was inserted in 20 premature, high risk infants for abdominal or thoracic surgery under combined caudal epidural and general anaesthesia. Epidurography was used to confirm the position of the catheter which was found to be misplaced in three patients. The catheter penetrated the dura in one case, in another the tip was located in an epidural vessel and in the third the catheter was seen to be curled up within the epidural space. It was concluded that epidurographic control is essential with this method of anaesthesia in very small infants, in whom it was found to provide considerable advantages despite serious risks.

Effectiveness of 1% lidocaine dorsal penile nerve block in infant circumcision

A prospective, controlled, double-blinded investigation was conducted to evaluate whether infants undergoing circumcisions with 1% lidocaine dorsal penile nerve blocks experienced decreased stress as compared with those receiving saline solution injections or no injections. Stress was measured in terms of pulse rate and oxygen saturation on a pulse oximeter. A subjective grading scale was also developed to measure infant irritability. The total number in the study was 51 with 23 infants in the lidocaine group, 21 in the saline solution group, and 7 in the no injection group. The results of the study revealed an average increase of 28.8% in the pulse rate above baseline for the control infants (p less than 0.001) versus no significant change in the lidocaine group. The average oxygen saturation of the control groups decreased by 5.6% from baseline (p less than 0.001), and that of the lidocaine group decreased by 1.0%, which was not a significant change. The subjective data were gained by using a grading scale of 1 to 6 with 1 being the least irritable infant and 6 being the most irritable infant. The physician evaluation gave an average rating of 4.2 to the control group versus 2.4 for the lidocaine group (p less than 0.001). The nursing evaluation during the procedure gave an average rating of 4.2 to the control group versus 2.3 to the anesthetized group (p less than 0.001). The subjective evaluation of infants before and after the procedure was not significantly different. There were no major complications in any of the groups.

Pharmacokinetics of midazolam in critically ill neonates

Midazolam is a water soluble benzodiazepine, with a short elimination half-life in adults and children. An IV bolus of midazolam 0.2 mg.kg-1 was administered to 10 critically ill neonates receiving intensive care who required sedation. The plasma clearance was 6.85 ml.min-1 and the elimination half-life was 6.52 h. Midazolam was well tolerated during and after administration. Because of its short half-life compared to diazepam, midazolam could be used during the neonatal period to produce brief rapid sedation.

Tonic nociception in neonatal rats

The issues of whether infants detect noxious stimuli and whether their nociceptive responses are suppressed by analgesics has been the focus of considerable controversy. Therefore, to more completely assess the nociceptive responses of neonatal rat pups to tonic pain, we tested 3-day-old rat pups using the formalin test. The responses of the young pups to formalin-produced injury were similar to those observed in adult rats, both behaviorally and in terms of their responsivity to morphine-induced antinociception. These results provide the first clear-cut evidence of integrated tonic pain responses in the neonate.

Alfentanil pharmacokinetics in preterm infants

The pharmacokinetics of alfentanil were studied during the first four days after birth in 22 ventilated preterm infants who were all receiving muscle relaxants. Five minutes after a single dose of 20 micrograms/kg alfentanil median serum concentration was 66 ng/ml (range: 20-606). The median clearance was 0.87 ml/kg/min (range: 0.4-9.62) and median elimination half life 321 mins (64-1251). There were wide differences in the manner in which individual infants handled the drug and transient depression of blood pressure and heart rate was observed. These data were used to calculate an infusion dosage. In four infants 20 micrograms/kg alfentanil given by infusion over 30 minutes followed by 5 micrograms/kg/hour produced steady state median alfentanil concentrations of 54.5 ng/ml (range: 7-73 ng/ml) with no evidence of drug accumulation.

Pain in newborns and prematures: current practice and knowledge

No unambiguous answer can be given as to whether newborns are able to feel pain similar to that experienced by older children and adults. However, there are several lines of evidence--anatomical, physiological and behavioral--which substantiate the possible presence of distressing nociceptive activity in the full-term and preterm neonate. Although the efficacy and safety of anesthesia in newborns and prematures has repeatedly been demonstrated, there are still numerous recommendations and current practices, based on antiquated theories, that withhold adequate medications from neonates during surgery. Even if the emotional and cognitive aspects of nociception in the newborn remain a subject of speculation giving rise to philosophical discussions as to the correct terminology, it is the mandate of newborns' physicians to provide the best possible therapy to their patients and to protect them from distress, unease and presumptive pain.

Three-dimensional distribution of 3H-naloxone binding to opiate receptors in the human fetal and infant brainstem

Despite the putative role of opioids in disorders of the developing human brainstem, little is known about the distribution and ontogeny of opioid-specific perikarya, fibers, terminals, and/or receptors in human fetuses and infants. This study provides baseline information about the quantitative distribution of opiate receptors in the human fetal and infant brainstem. Brainstem sections were analyzed from three fetuses, 19-21 weeks gestation, and seven infants, 45-68 postconceptional weeks, in whom the postmortem interval was less than or equal to 12 hours. Opiate receptors were localized by autoradiographic methods with the radiolabelled antagonist 3H-naloxone. Computer-based methods permitted quantitation of 3H-naloxone binding in specific nuclei, as well as three-dimensional reconstructions of binding patterns. High 3H-naloxone binding corresponds primarily to sensory and limbic nuclei, and to nuclei whose functions are known to be influenced by opioids, e.g., trigeminal nucleus (pain), nucleus tractus solitarii and nucleus parabrachialis medialis (cardio-respiration), and locus coeruleus (arousal). The regional distribution of opiate receptors as determined by 3H-naloxone binding is similar in human infants to that reported in human adults and animals and corresponds most closely to that of mu receptors. We found, however, that opiate receptor binding is high in the fetal and infant inferior olive, in comparison to low binding reported in this site in adult humans, primates, and rodents. In addition, opiate receptors are sparse in the fetal and infant substantia nigra, as in reports of the adult human substantia nigra, compared to moderate densities reported in primates and rodents. By midgestation, the regional distribution of 3H-naloxone binding in human fetuses is similar, but not identical, to that in infants. Highest 3H-naloxone binding occurs in the inferior olive in fetuses at midgestation, compared to the interpeduncular nucleus in infants. Tritiated naloxone binding quantitatively decreases in virtually all nuclei sampled over the last trimester, but not to the same degree. The most substantial binding decrease (two- to fourfold) occurs in the inferior olive and may reflect programmed regressive events, e.g., neuronal loss, during its development. Definitive developmental trends in 3H-naloxone binding are not observed in the postnatal period studied. The heterogeneous distribution of opiate binding in individual brainstem nuclei underscores the need for volumetric sampling in quantitative studies.

Perioperative pain management in children: a review

Pain in children from the neonate to the teenager has recently begun to achieve the attention it deserves in the medical literature. Practitioners have been slow to apply both old and new techniques in this patient population. This review focuses on the perioperative management of pain and its associated symptoms in pediatric patients.

Postoperative analgesia in neonates: an Australia-wide survey

An Australia-wide survey of the use of postoperative analgesia in neonates has been conducted. A high overall use of analgesia has been recorded with 75% of respondents prescribing an opioid. The frequency of use of local or regional analgesia was disappointingly low at 8% overall. The general attitude is that analgesia is desirable but a fear of respiratory depression inhibits its use, particularly in non-ventilated neonates and after more minor surgery. It is suggested that a wider use of regional anaesthesia techniques may reduce this problem.

Cutaneous hypersensitivity following peripheral tissue damage in newborn infants and its reversal with topical anaesthesia

The flexion reflex threshold has been used as a measure of sensation in a group of premature infants born at 27-32 weeks postmenstrual age. The threshold in an area of local tissue damage created by routine heel lances was half the threshold on the intact heel on the other side. This indicated a hypersensitivity to tissue damage analogous to tenderness or hyperalgesia reported in adults. In a double-blind study, treatment of the damaged area with the topical anaesthetic cream, EMLA, was found to reverse this hypersensitivity or in other words increase the flexion reflex threshold. Treatment with placebo had no effect. The results show that the newborn infant central nervous system is capable of mounting a chronic pain response to local injury which can be reduced by local anaesthetic.

Pediatric postoperative pain management

This article reviews methods to relieve postoperative pain in most children. It also discusses the major barriers to treatment and considers the provision of opioids via a painless route as an alternative to the more usual intramuscular (and painful) route.

The undertreatment of pain in children: an overview

At the present time, the management of pain in children is not addressed with the same vigor and enthusiasm as is the management of pain in adults. Limited accessible information and limited research have allowed inaccurate and inadequate information to persist, which serves to justify the status quo. The personal nature of pain and the complexity of assessing it have offered further obstacles. Changes are occurring, however, which will dramatically alter present practice. It will soon be unacceptable socially and medically to ignore the suffering of children.

The assessment of pain in children

This article focuses on the methods of pain measurement and assessment in children. The concepts of reliability and validity and the available types of physiologic, self-report, and behavioral measures are addressed. Methods of pain assessment in infants and toddlers, preschoolers, school-aged children, and adolescents are detailed. Finally, some practical suggestions for pediatric pain assessment are provided.

Management of burn pain in children

In spite of the many possible methods of pain control in the burned child satisfactory pain management may still be a problem, at times formidable. The most fruitful approach would seem to be frequent assessment of pain in the individual patient with a readiness to try alternative or additional measures when relief seems inadequate. In this way the most effective analgesic agent(s), route(s), and frequency of administration, as well as nonpharmacologic methods, can be determined for each child. Among those able to speak, pain estimation is usually easily accomplished. In infants and those intubated for supported ventilation, however, the task is more difficult. Nevertheless, careful observation of physiologic signs such as heart rate and blood pressure, facial expressions, body movement and position, and the quality of an infant's cries may in sum be sufficient to evaluate the intensity of pain. Monitoring of analgesic plasma levels to ascertain that they are within the ranges established for good analgesia and even determination of beta-endorphin blood levels may also aid in judging the adequacy of analgesia. By tailoring pain management methods to the needs of each child it may be possible to keep pain at acceptable levels in victims of burn injury.

Neonatal pain associated with caregiving procedures

This article presents evidence that newborns react to aversive caregiving procedures--heelsticks, circumcision, and surgery--with distinct physiological, behavioral, and metabolic responses. These responses are similar to those associated with pain in adults. Suggestions are made on methods of ameliorating the infant's responses to aversive caregiving procedures.

The management of pain associated with pediatric procedures

This article provides guidelines for the psychological and pharmacologic management of pain and anxiety for children undergoing medical procedures. The goals of intervention are presented, as well as issues warranting consideration in planning intervention to reduce procedure-related distress.

Developmental and psychological factors in children's pain

It is clear that previously we were ill-informed and misinformed about children's pain. Recent investigations have led not only to a burgeoning of understanding of pediatric pain, but also an increase in our ability to appropriately measure and treat children's pain. Both pharmaceutical and nonpharmaceutical treatments have made major strides in the past few years. Even more crucial is the change that has happened in the willingness of health professionals to recognize that children do suffer pain and that aggressive treatment is often indicated. However, careful consideration must be given to physiologic, cognitive, affective, and psychosocial development, both in order to maximize the effectiveness of interventions and to recognize the limits that development may place on any specific approach.

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

Beginning with a brief description of mature anatomic pathways and neurotransmitters in the "pain system," this article details their development in the human fetus, neonate, and child. Special emphasis is given to the basic mechanisms and physiologic effects of opioid analgesia. The clinical implications of these data are described, particularly with regard to the maintenance of cardiovascular stability and hormonal-metabolic homeostasis in newborns and children undergoing surgery or other forms of stress.

Circumcision

There are no absolutes regarding circumcision, and the decision to circumcise a child as a newborn or otherwise must be made after carefully weighing the alternatives to, and risks and benefits of, this common surgical procedure. These alternatives, risks, and benefits must be fully explained to parents considering circumcision, and informed consent must be obtained. In well-trained, experienced hands, circumcision is a safe procedure that effectively eliminates proven problems such as cancer of the penis, and may eliminate the problems of increased risk of urinary tract infection and sexually transmitted diseases.