Pain in prelingual children and its evaluation by pain-induced vocalization

[Pain in the fetus: neurobiological, psychophysiological and behavioral aspects.]

Until a short time ago, the view prevailed worldwide that children were less sensitive to pain than adults, and such operations as circumcision were performed in babies without adequate anesthesia or analgesia. This view is now considered a misconception, as psychophysiological and behavioral studies show that even neonates have a well-functioning nociceptive system. Nociception generally refers to the neural and sensory aspects of pain, which do not necessarily include conscious experience. There is no discontinuity in the development of the nervous system during birth, and therefore it can be concluded that the fetus is also responsive to noxious stimuli. The question arises as to the stage of ontogeny of the human at which nociceptive behavior begins. Literature on the fetal nervous system reveals that the first signs of somatosensory system function occur at week 7 of gestation and at week 22 the synaptic connection from the nervous periphery to the somatosensory cortex is becoming established. During this period, motor behavior matures, from stereotyped reflexes to spontaneously generated complex motor patterns reminiscent of the repertory of voluntary movement. From week 22 onward the electroencephalogram (EEG) shows increasingly more varied patterns, and sleep-wake states can be discerned after week 30 of gestation. Somatosensory evoked cortial potentials have been recorded from gestational week 28 onward. Substance P, a neuropeptide associated with pain in the adult nervous system, is present in the fetal spinal cord as early as week 12 of gestation, while the antinociceptive opioid peptide enkephalin does not appear until week 24. From week 15 onward, opioid peptides such as beta-endorphin appear in the pituitary; their release becomes sensitive to environmental stimuli from about week 20 onward, which can be considered the onset of pituitary stress responses. In particular, parturition and abortion induced the release of opioid peptides. Studies of conditioned behavior show that the fetus has the ability to learn. It has been hypothesized that the fetus and neonate possess a procedural memory, which is not transferred to the language-based memory of later phases of life. Learning and memory are the most essential elements for the construct of "consciousness." Therefore, a primitive type or level of consciousness might exist in the fetus. Thus, a considerable range of sensorimotor function, including memory, develops during fetal life. Anatomical, physiological and behavioral data suggest that the nociceptive system is included in this development. Although we cannot be sure at present whether the fetus consciously experiences pain, beyond the protective nociceptive behavioral responses, anesthesia should be used for invasive procedures to protect the fetus and its nervous systems.

Male circumcision: pain, trauma and psychosexual sequelae

Infant male circumcision continues despite growing questions about its medical justification. As usually performed without analgesia or anaesthetic, circumcision is observably painful. It is likely that genital cutting has physical, sexual and psychological consequences too. Some studies link involuntary male circumcision with a range of negative emotions and even post-traumatic stress disorder (PTSD). Some circumcised men have described their current feelings in the language of violation, torture, mutilation and sexual assault. In view of the acute as well as long-term risks from circumcision and the legal liabilities that might arise, it is timely for health professionals and scientists to re-examine the evidence on this issue and participate in the debate about the advisability of this surgical procedure on unconsenting minors.

Machine recognition and representation of neonatal facial displays of acute pain

OBJECTIVE

It has been reported in medical literature that health care professionals have difficulty distinguishing a newborn's facial expressions of pain from facial reactions to other stimuli. Although a number of pain instruments have been developed to assist health professionals, studies demonstrate that health professionals are not entirely impartial in their assessment of pain and fail to capitalize on all the information exhibited in a newborn's facial displays. This study tackles these problems by applying three different state-of-the-art face classification techniques to the task of distinguishing a newborn's facial expressions of pain.

METHODS

The facial expressions of 26 neonates between the ages of 18 h and 3 days old were photographed experiencing the pain of a heel lance and a variety of stressors, including transport from one crib to another (a disturbance that can provoke crying that is not in response to pain), an air stimulus on the nose, and friction on the external lateral surface of the heel. Three face classification techniques, principal component analysis (PCA), linear discriminant analysis (LDA), and support vector machine (SVM), were used to classify the faces.

RESULTS

In our experiments, the best recognition rates of pain versus nonpain (88.00%), pain versus rest (94.62%), pain versus cry (80.00%), pain versus air puff (83.33%), and pain versus friction (93.00%) were obtained from an SVM with a polynomial kernel of degree 3. The SVM outperformed two commonly used methods in face classification: PCA and LDA, each using the L1 distance metric.

CONCLUSION

The results of this study indicate that the application of face classification techniques in pain assessment and management is a promising area of investigation.

Our youngest patients' pain--from disbelief to belief?

Though human pain has existed since the dawn of time, formal medical pain relief in the form of anesthesia and analgesia has been available only since the mid-nineteenth century. Even after these measures became available, they were used very selectively for the first 100 years of their existence. The youngest patients, especially, were denied pain relief, probably because they could not complain about their pain as articulately and as effectively as adult patients could. A desperate need existed for health care professionals to recognize and appreciate the fact that their youngest patients could suffer immensely and to adequately address the issue. This article reviews the evolution of knowledge and attitudes regarding young patients' pain and addresses why and how this process occurred. The evolution of knowledge was traced by reviewing the literature found in MEDLINE, CINAHL, and LEXIS-NEXIS searches and through hand searches of articles that were frequently cited. Physiologic, pharmacologic, ethical, and psychologic aspects of young patients' pain are addressed. A unique phenomenon arose from the data reviewed. The process of belief and changes in practice were encouraged not only by advances in science, but also by consumer demand. Advances in the past decade in the management of young patients' pain were profound, but are still not complete. Understanding the evolution surrounding pain recognition in young patients provides a stepping stone that can facilitate further improvements in the management of pain in young patients.

Biologic markers of pain in the vulnerable infant

Detecting and quantifying pain in infants and young children is a complex task because young children cannot communicate this subjective phenomenon. In the 1950s, it was postulated that there might be "wound hormones" produced in injured tissues that activated the pituitary-adrenal axis. Research in adults demonstrated that plasma levels of different hormones, including corticosteroids, cathecholamines, growth hormone, and insulin, changed in response to emotionally and physically stressful stimuli. Stress response is the term given to those hormonal and metabolic changes that follow injury or trauma, but the debate as to whether increased stress response is a sign of pain or whether decreased stress response is a sign of diminished pain has not been resolved yet. Following the study of systemic response to surgery, the ability of anesthetic agents to substantially attenuate intraoperative and postoperative stress response has been reported. In newborns, a strong correlation between preoperative stress and postoperative complication rate was found. The full extent of the vulnerable infant's pain is still poorly understood, but further research of known biologic markers and newly discovered ones could promote our understanding of the pain response and increase our ability to prevent undesirable outcome.

Modern concepts of paediatric analgesia

Laboratory data, economic pressures, and the wish for humane treatment have been some of the driving forces behind improvements in paediatric pain management. Within the space of 10 years, there have been dramatic changes in the quality of treatment received by children undergoing surgical operations. Moreover, those receiving medical treatment, for example, sickle cell disease, have also benefited from increased experience in pain management. Children receiving care in specialised centres can now expect to benefit from up-to-date techniques of pain management, such as patient-controlled analgesia, nurse-controlled analgesia, and epidural infusions. They will be managed by ward nurses experienced and trained in paediatric pain relief, they will be attended by nurses whose special interest and training is the management of children's pain, and they will be provided with the techniques of analgesia by competent, trained anaesthetic staff. Improved care, with close attention to pain relief, is not only humane, but improves the patient turnaround by enhancing rapid discharge. Further education is required to spread these benefits to children being managed outside highly specialised centres. Not only education, but investment, is needed also to ensure that all children receive a standard of care second to none.

Validity of behavioral and physiologic parameters for acute pain assessment of term newborn infants

CONTEXT

The subjectivity of pain causes enormous difficulties in evaluating neonatal pain with a single, practical and easy-to-apply tool. Pain evaluation in the neonatal period should be performed by valid, safe, useful and feasible methods.

OBJECTIVE

To evaluate the validity of the Neonatal Facial Coding System (NFCS), Neonatal Infant Pain Scale (NIPS), heart rate (HR) and O2 saturation (O2 sat) for neonatal pain assessment.

DESIGN

Prospective, double-blind randomized trial.

SETTING

A secondary level maternity hospital.

PARTICIPANTS

70 healthy neonates requiring bilirubin dosage were randomly assigned to receive a venous puncture (P: n = 33, BW 3.2 kg, SD 0.6; GA 39 wk, SD 1; 59 h of life, SD 25) or an alcohol swab friction (F: n = 37; BW 3.1 kg, SD 0.5; GA 39 wk, SD 1; 52 h of life, SD 17).

INTERVENTION

All measurements were taken prior to (PRE), during (TO), and 1 (T1), 3(T3), 5(T5) and 10(T10) minutes after the procedure.

MEASUREMENTS

A neonatologist evaluated NFCS, NIPS, HR and O2 sat by pulse oxymetry.

RESULTS

Median NFCS and NIPS results at T0, T1 and T3 were higher in P group, compared to F. More P neonates presented NFCS > 2 and/or NIPS > 3 at T0, T1 and T3. HR was lower in P group at T1. Average O2 sat was above 90% during the whole study period in both groups.

CONCLUSION

NFCS and NIPS are suitable instruments for neonatal pain evaluation. Heart rate and O2 saturation can be used only as auxiliary methods.

Pain in the very preterm baby: 'suffer little children?'

Increases in medical expertise and technological advances have enabled the survival of very preterm babies who form a new and growing population. Comparisons between the foetus, full-term baby and the very preterm baby indicate that by the time the foetus is of 23 weeks gestation, many of the abilities, for example, sensing touch, hearing, seeing, moving and even learning may be common to all three. Thus, the very preterm infant who has been described as a unique organism, is not passive, but is a sentient being who is unlikely to survive without the medical and technical support of the Neonatal Intensive Care Unit (NICU) where he/she is exposed to frequent and regular medical procedures. Many of these procedures would be, for any normal, fully developed human being at best uncomfortable and at worst painful. Reviews within the past 10 years have shown that the neurochemical, anatomic and functional systems of newborns are developed enough to perceive pain. More importantly, rat pup studies have indicated that not only may the very preterm baby experience pain but it may experience it more intensely than the more mature infant. Moreover, there may be serious consequences of repeated painful medical intervention. Alleviation of pain and/or distress in very preterm infants is, therefore, an important issue.

Measurement of neonatal responses to painful stimuli: a research review

The measurement of neonatal responses to painful stimuli remains a significant clinical problem. Although numerous measures have been evaluated, instruments that are valid, reliable, and clinically feasible are not yet available. The purpose of this paper is to critique the studies that have been done using biochemical, physiological, and behavioral measures to evaluate neonatal responses to painful stimuli. Specific issues regarding measurement in premature and critically ill neonates are emphasized. The intent of this review and critique of the literature is to stimulate additional research into the assessment of neonatal pain.

Through a glass darkly: using behavior to assess pain

Behavior assessment is crucial to the process of evaluation of pain and discomfort in veterinary patients. Behavioral responses to pain and other stressors are a function of the interaction between the individual and its environment, and are influenced by many factors including species, breed, age, sex, source of pain, and coexisting disease. Behavioral changes associated with acute postoperative pain typically peak within 24 hours and wane progressively thereafter. The intensity and duration of postoperative pain correlate with the location and extent of tissue injury, but there is much inter-patient variation of each characteristic. Published methods of systematic evaluation of pain in animals include objective measures of physiologic responses to experimental pain, subjective or semi-objective assessment of postoperative behavior, and quantitative measures of postoperative behavior and physiology. The techniques of quantitative measures of behavior are similar to pain-rating instruments developed for use in young children. Although objective assessment tools are difficult to develop and time consuming to apply, their methodological rigor and objectivity allow evaluation of behavior with minimal observer bias. Until objective assessment tools become widely used clinically, the best approach is to actively seek out evidence of pain in our patients, assuming its presence whenever there is tissue injury or inflammation.

Use of anti-inflammatory and analgesic drugs in dogs and cats

Responses (486) were collared from a survey of 5054 Australian veterinarians on their use of anti-inflammatory and analgesic drugs in dogs and cats. Almost all respondents used glucocorticoids (usually prednisolone) to treat allergic, pruritic dermatoses in dogs, while two-thirds also gave fatty acid supplements and one-half used antihistamines. Almost 60% of respondents initially injected a glucocorticoid (frequently a long-acting preparation) when treating inflammatory skin diseases in dogs. More than 90% of respondents used glucocorticoids to treat immune-mediated haemolytic anaemia or thrombocytopenia, and about one-third also gave cytotoxic drugs. Administration of prednisolone on alternate days was generally favoured for long-term enteral steroid therapy. Phenylbutazone was the most preferred treatment for painful or inflammatory musculoskeletal disorders of dogs, but aspirin and pentosan polysulphate were also used widely. Regarding the use of analgesics drugs generally, both narcotic analgesics and non-steroidal anti-inflammatory drugs (NSAIDs) were used more widely in dogs than in cats, but alpha-2 agonists were used similarly in both species. The most commonly used narcotic analgesics were pethidine and buprenorphine in both species, while the NSAIDs used most often were flunixin and dipyrone in dogs and ketoprofen in cats. More than 80% of respondents generally used analgesic drugs with potentially painful surgical procedures, with doses given usually before anaesthetic recovery. Analgesic use rates varied with the condition, ranging from 94% for patients with acute severe trauma, through 60% for cruciate ligament repair and 29% for perineal herniorrahphy, to about 5% for ovariohysterectomy and dog castration. The three clinical signs most frequently nominated as indicators of pain in dogs and cats were (in descending order) vocalisation, response to handling or palpating the affected area, and mental depression. Other items mentioned frequently were behavioural changes and immobility (in both species), inappetence/anorexia in cats, and altered respiration in dogs.

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.

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.

Rocking and pacifiers: two comforting interventions for heelstick pain

The effects of behavioral interventions in reducing the stress of infant pain are not well documented. Two comfort interventions, rocking and pacifiers, were compared with routine care administered to 60 newborn infants randomly assigned to the three conditions following a neonatal screening heelstick. Heart rate, state of arousal, and crying were recorded continuously. Both pacifiers and rocking reduced crying, but pacifiers predominantly produced sleep states and rocking predominantly produced alert states. Pacifiers reduced heart rate levels significantly more than did rocking. Thus, newborns clearly benefit from both comforting methods. Several mechanisms are proposed to account for these findings.

Self-mutilation following brachial plexus injury sustained at birth

Self-mutilation after deafferentation injuries has been reported only rarely in adult humans. This behavior has been found to be similar to that observed in animals that have been subjected to experimental deafferentation. We present a child with a brachial plexus injury sustained at birth who began to bite her analgesic digits. Self-mutilation behavior in humans is reviewed and its relevance to current deafferentation pain animal models is examined. This behavior in humans further validates the current animal model of deafferentation pain.

Papaveretum infusions in infants under 6 months of age

The effectiveness of a continuous low dose papaveretum infusion for the relief of postoperative pain was assessed in 29 infants aged 1-6 months nursed on the infant surgical ward following major abdominal surgery. Trained nursing staff were able to adjust the dosage within prescribed guidelines and satisfactory analgesia was obtained with a regimen which delivered up to 0.0375 mg/kg/hour, approximately half the dose recommended in children older than 12 months. There was one case of clinically significant respiratory depression.

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.

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.

Evaluating a child's pain

Much recent attention has focused on the development and refinement of pain measures, as well as on the use of more effective pain control methods for infants, children, and adolescents. This article reviews the primary categories of pediatric pain measures, with a specific focus on the selection of the most appropriate behavioral, physiologic, or subjective method for assessing a child's pain. The optimum pain measure depends on the age and cognitive level of a child, the type of pain experienced, and the situation in which the pain occurs. While no single measure is adequate for all children for all types of acute, recurrent, and chronic pain, it is possible to choose practical, valid, and reliable methods for evaluating any child's pain experience.

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.

[Neuro- and psychophysiology of pain in children.]

In the past the view has often been expressed that children are less sensitive to pain than adults as a result of the assumption that their nervous system is not as well developed. According to this theory, newborns were not supposed to feel pain at all, and for this reason minor surgery was often performed with inadequate anesthesia. Evidence in the more recent literature and the regular choice of "pain in children" as a topic for congresses exemplify the more and more widespread belief that children of all ages can feel pain and, relative to their developmental stage, suffer accordingly. However, there are significant differences in the way children experience and react to pain in comparison to adults, e.g., because of the difference in ability to evaluate acute or chronic pain cognitively. At birth, all human sensory organs have developed far enough to be full functional-as a result of the long gestational period, which is far longer than most other mammalian species. The results of animal experiments and observations in newborns have led to the conclusion that in humans and other mammals, the sensory pain system is fully developed at birth. Pain-related reactions can be seen in the motor, vegetative and endocrine pain parameters, and in the infant's crying. As the experience of pain increases, conditioned avoidance reactions can be noted, as can the child's experience of psychosomatic pain reinforcement by the care-givers, e.g., when a crying child in pain receives more attention from the persons around it. In pre-school children, the level of pain can be measured using appropriate instruments, as demonstrated in cases of chronic arthritis. As cognition develops further, the patient's own concept of health and sickness changes, as does the ability to express feelings of pain. In the pathogenesis of pain in children, the dominant types are nociceptor pain (e.g., as a result of trauma or infection) and pain resulting from malfunction (e.g., physical malposition, migraine), whereas nervous pain occurs less frequently. Pediatricians should pay particular attention to the treatment of acute and chronic pain in children.

Management of pediatric pain with opioid analgesics

We have attempted to dispel many of the myths and misconceptions surrounding the use of narcotic analgesics in the treatment of childhood pain. Our hope is that an improved understanding and the application of effective, safe therapy will minimize the suffering of the child with acute or chronic pain.

Paediatric anaesthetists' perceptions of neonatal and infant pain

A questionnaire was sent to all members of the Association of Paediatric Anaesthetists in the U.K. and Eire, enquiring into their attitudes towards the perception of pain, its assessment and the use of opioids and regional anaesthesia in neonates and infants under 1 year of age. Sixty members returned completed forms out of a total of 66. The results showed that although most anaesthetists in the survey believe that even neonates feel pain, they are reluctant to prescribe analgesia. It was found that the objective signs considered to be most indicative of pain were potentially misleading.

An assessment of children's pain: a review of behavioral, physiological and direct scaling techniques

Research on the assessment and management of pain in infants and children has increased dramatically, with the consequence that a wide variety of behavioral, physiological, and psychological methods are now available for measuring pediatric pain. Although the criteria for a pain measure for children are identical to those required for any measuring instrument, special problems exist in pediatric pain measurement because the influence of developmental factors, previous pain experience, and parental attitudes on children's perceptions and expressions of pain is not known. This article reviews the recent advances in the measurement of pain in children, with special emphasis on the methods that satisfy the criteria for reliability and validity, the methods that can be used to assess multiple dimensions of pain, and the methods that may be appropriate for assessing all types of acute, recurrent, and chronic pediatric pain.

Pain expression in neonates: facial action and cry

Pain expression in neonates instigated by heel-lance for blood sampling purposes was systematically described using measures of facial expression and cry and compared across sleep/waking states and sex. From gate-control theory it was hypothesized that pain behavior would vary with the ongoing functional state of the infant, rather than solely reflecting tissue insult. Awake-alert but inactive infants responded with the most facial activity, consistent with current views that infants in this state are most receptive to environmental stimulation. Infants in quiet sleep showed the least facial reaction and the longest latency to cry. Fundamental frequency of cry was not related to sleep/waking state. This suggested that findings from the cry literature on qualities of pain cry as a reflection of nervous system 'stress', in unwell newborns, do not generalize directly to healthy infants as a function of state. Sex differences were apparent in speed of response, with boys showing shorter time to cry and to display facial action following heel-lance. The findings of facial action variation across sleep/waking state were interpreted as indicating that the biological and behavioral context of pain events affects behavioral expression, even at the earliest time developmentally, before the opportunity for learned response patterns occurs. Issues raised by the study include the importance of using measurement techniques which are independent of preconceived categories of affective response.

Impact of the diagnosis of AIDS on hospital care of an infant

Detailed analysis of caretaker response to the first infant newly diagnosed with AIDS at a university hospital was done by review of nursing notes for three periods: before diagnosis of AIDS, after diagnosis, and after psychiatric consultation. Five consultation questions were posed, and the findings on investigation of these questions are discussed. It was found that the percentage of time that PRN medication was given dropped after diagnosis of AIDS but rose above the initial level after the consultation. The number of times per shift the nurse touched the baby (TLCs) was not found to be associated with use of PRN medication; rather it was explained by which nurse was caring for the child. This study focuses on variations in nursing care of one infant to illustrate how variation in caretaker response can amplify the range of perturbations of the infant's behavioral response. It is speculated that caretakers of patients with AIDS may normally have feelings considered unacceptable in medical settings, including fear, blaming the patient, or a wish to avoid the patient. Such feelings are more difficult to tolerate in the care of children or infants and are superimposed upon the familiar stains associated with the care of chronically ill or dying pediatric patients.

Psychological aspects of painful medical conditions in children. I. Developmental aspects and assessment

The assessment and development of pain in children is reviewed in the first part of a two-part series. Assessment of pain in children has relied on self-report measures that have included visual analogue procedures using concrete stimuli for ratings. Behavioral assessment procedures are more sophisticated, but research on behavioral assessment of pediatric pain has begun to emergy only recently. There has been very little research on the developmental aspects of pain tolerance and pain threshold in children. There are preliminary indications that children's thoughts and attitudes about pain may change with age in a manner that contributes to more intense feelings of pain in adolescence than childhood. Children undergoing painful medical procedures show declining emotional outbursts with age and increasing signs of self-control and muscular rigidity. Possibilities for integrating the study of the developmental aspects of pain with social learning theory, cognitive developmental theory, and the psychology of physical symptom perception are discussed.

A developmental cognitive-biobehavioral approach to pediatric pain assessment

Recent years have seen an increase in the study of pain in children. However, a comprehensive framework to help guide pediatric pain assessment has not been available. A developmental approach to facilitate cognitive-biobehavioral assessment of pediatric pain is presented and discussed. An illustrative literature review of pain assessment measures, cognitive development and conceptualizations of health and illness is provided. The developmental cognitive-biobehavioral approach is offered as a guide for future research in pediatric pain assessment.

Acute pain response in infants: a multidimensional description

Fourteen infants who were undergoing routine immunization were studied from a multidimensional perspective. The measures used were heart rate, crying, body movement/posturing, and voice spectrographs. There was wide variability between infants on the measures, especially on the cry spectrographs, although facial expression was consistent across infants. The pattern that did emerge was characterized by an initial response: a drop in heart rate, a long, high pitched cry followed by a period of apnea, rigidity of the torso and limbs, and a facial expression of pain. This was followed by a sharp increase in heart rate, lower pitched, but dysphonated cries, less body rigidity, but still facial expression was of pain. Finally, in the second half of the minute's response, heart rate remained elevated, cries were lower pitched, more rhythmic, with a rising-falling pattern, and were mostly phonated, and body posturing returned to normal. Those faces that could be viewed also were returning to the at rest configuration. It was suggested that facial expression may be the most consistent across-infant indicator of pain at this point in time.

Dysesthesias and self-mutilation in humans and subhumans: a review of clinical and experimental studies

The chronic deafferentation syndrome includes a complex pattern of abnormal self-directed behavior and a stress response. Subhuman self-mutilation is a secondary consequence of the chronic deafferentation syndrome. The evidence indicates that the chronic deafferentation syndrome in subhumans is a valid model for the induced and the spontaneous dysesthesias in humans. Objective criteria for the definition of subhuman dysesthesias have been derived from independent sources of evidence, in neurally intact subjects; those criteria are then found to match the subhuman syndrome of deafferentation. Support for the validity of the inference of subhuman dysesthesias derives from the parallels with the various facts of the human dysesthesias. The credibility of this argument is significantly strengthened by reports of morphological and excitatory physiological abnormalities, in central somatosensory structures, in response to deafferentation. There is no independent subhuman evidence in support of alternate interpretations of the deafferentation syndrome, and those interpretations seem to be inadequate in several aspects. Doubts concerning the validity of this animal model have been allayed by reports of dysesthesias in humans with spinal posterior rhizotomies or ganglionectomies, and also those with congenital analgesia. Moreover, the occurrence of this syndrome in hypoalgesic areas as a consequence of anterolateral cordotomy in monkeys, can best be interpreted as a reflection of dysesthesias. This syndrome is released by neuropathological or neurosurgical lesions in the peripheral or central nervous system; lesions which involve small caliber peripheral afferents or the spinothalamic tract. Variability in the release of this syndrome has been associated with several different factors. So far, the chronic syndrome is intractable. Evidence relates the abnormalities of this syndrome to pathophysiological foci in central relays of the somatosensory system, and suggests that the chronic abnormalities of this syndrome can be sustained at brain levels.

Pain and pain control in children

Focused research on pain and pain control in children has developed primarily in the last 10 years and even now is woefully inadequate in relation to the magnitude of the problem. The available research, inferences from the adult literature, and anecdotal information all indicate the elusive nature of pain. Pain is not solely a fixed neurophysiologic response to a noxious stimulus but a product of the interaction of many variables such as age, cognitive set, personality, ethnic background, and emotional state. These factors exert a tremendous influence on the suffering which surrounds the pain message. Technology exists at present to eliminate or substantially reduce pain in almost all cases. There remains, however, a tendency, which is even more pronounced with respect to children, to underestimate or ignore pain. In an overall approach to pain in children, the following points should be considered: A high index of suspicion is necessary to determine if children are experiencing pain since they may have difficulty verbalizing their discomfort. In infants, physiologic variables should be considered (increased heart rate, palmar sweating, increased respiratory rate), and in preschoolers, time should be taken to ascertain that the child actually understands the word "pain" if it is used in questioning them. Some method of continuous monitoring, such as a visual analogue scan, should be considered as part of the treatment plan. Adequate analgesia should be provided. The appropriate dose should be administered at the appropriate pharmacokinetic time. Too little medication may cause obsessive attention to medication-related issues. Too much medication may cause sedation and lack of mental clarity, which is often anxiety-producing for both the parents and the child. The usefulness of p.r.n. medication has been seriously questioned and a time-contingent as opposed to pain-contingent strategy should be applied. Fears of addiction are generally unwarranted. Adjunctive medication may increase the value of offered narcotics and counteract some of their side effects. Although this monograph has focused more attention on pharmacologic than on nonpharmacologic approaches to pain, this is merely a reflection of available data and not necessarily of relative importance. The importance of distraction from pain by nursing, medical, or child life personnel using play techniques cannot be overestimated. Every attempt should be made to relax the child by using creative strategies. Preparation of the child for procedures is often helpful as some of the fear of the unknown is eliminated.(ABSTRACT TRUNCATED AT 400 WORDS)

Pain in infancy: conceptual and methodological issues

The concept of pain in infancy was explored. It was suggested that our every day usage of the term pain be applied to infants. Essentially this suggestion is that we infer that an infant has a subjective experience that is unpleasant when there is evidence of tissue damage and the infant responds with signs of distress, such as crying, increased heart rate, facial expression consistent with distress or other signs. Conceptualizations of adult clinical pain and infant emotions were compared. It was proposed that our concept of infant pain should be multivariate and should include the ecological context in which pain occurs. In section 2 methodological issues were discussed. Ethical concerns for the protection of infant rights were voiced. Numerous opportunities for studying infant pain produced by necessary medical procedures were pointed out. A number of response systems which offer promise in understanding infant pain were reviewed with respect to their proven applicability to infant emotional and cognitive processes or to adult pain processes. This paper attempted to organize information which will be helpful to the researcher interested in infant pain or developmental processes in pain. From the preceding it should be obvious how remarkably little data we have which bears directly on the issue. The close association between the study of pain and the study of emotion has been shown. The study of emotional development, while ahead of the study of developmental aspects of pain, still lags far behind the study of cognitive development. Recently there has been a call for increased study of the development of emotion. The study of the development of pain might well proceed hand in hand. The present state of the field of infant pain is such that almost any data will add to our knowledge base. The complexity of the concept and the wide range of response systems would suggest that multidisciplinary research teams may develop some of the best research efforts. A multidisciplinary approach has been found to be essential in the treatment of chronic pain, for example. A listing of some of the types of professionals who would contribute would include: physicians, nurses, psychologists, biologists (including those trained in neurophysiology, ethology and endocrinology), sociologists and anthropologists. University medical centers seem an ideal environment for conducting such research, given the close proximity of various specialists and an available subject population.

Recurrent pains in children: an overview and an approach

This article provides a broad overview of current thinking about pain and then outlines an approach to a unique category of pain, recurrent pains of obscure origin.

Pain in infancy: neonatal reaction to a heel lance

A combined single subject and group design was used to investigate changes in heart rate and crying in response to a heel lance, non-invasive tactile stimulation and baseline periods in 10 male and 10 female infants, each in their second full day of life. Heart rate was measured with an electrocardiogram. Percentage of time crying was computed from observations of audiotapes. Results for individual subjects indicated that heart rate and percentage of crying were consistently increased by the heel lance but that there was often wide baseline variability in the two measures. Analysis of variance indicated that responses to heel lance were higher than responses to tactile stimulation which were in turn higher than responses to baseline for both heart rate and percentage of crying (P less than 0.01). No significant sex differences were found. It was suggested that the increases in heart rate and crying in the context of a tissue damaging stimulus indicated that the infants experienced pain and that pain in infants can be reliably measured in clinical settings.

Evaluation of cutaneous sensation in myelodysplastic children, using electrical stimulation

A new method, cutaneous electrical stimulation, was compared with the standard neurological examination for its effectiveness in detecting cutaneous sensation. Both methods provided clear and congruous results for 45 per cent of the patients. However, for the other 55 per cent, cutaneous electrical stimulation frequently detected sensation at sites which were classified as anaesthetic on standard neurological examination. Electrical stimulation also was able to indicate sensation in a group of infants too young to be evaluated by standard neurological evaluation.

Pain-induced vocalization in the rat and its modification by pharmacological agents

Vocalization was induced in rats by electrical stimulation of the tail (pain-induced vocalization), and its components were characterized in terms of latency, duration, frequency spectrum and energy. Noxious stimuli at threshold elicit a single vocalization component (V1). Increases in stimulus intensity produce additional discrete vocalization components (V2-Vn) with successively longer latencies, termed the vocalization afterdischarge (AD). The AD components are acoustically similar to each other but differ significantly from the V1 component. The duration, the specific acoustic measures and the sound energy of both V1 and AD components are positively correlated with intensity of the stimulus. The dependence of the V1 and AD components on the affective state of the rat was evaluated by comparing the acoustic characteristics of both components to those of stress-induced vocalizations, and by studying the effects of the anxiolytic drug diazepam and physical restraint on the threshold of V1 and AD. The AD components were markedly more dependent on the affective state of the rat then was the V1 component. A moderately low dose of morphine (3.0 mg/kg) also preferentially affected the AD component, suggesting that a significant portion of the action of morphine on pain-induced vocalization is mediated through its action on the affective state of the rat.

Developmental changes in infant pain expression during immunization injections

Developmental changes in pain expression provoked by routine immunization injections during the first 2 years of life were examined. An interval-sampling, behavioral observation system was developed to code categories of expressive behavior in infants, their mothers and the nurse responsible for the injection. Qualitative changes were observed in the infants' behavior, with those less than 12 months of age responding in a more spontaneous, diffuse manner, whereas the older infants displayed more anticipatory distress, descriptive language and goal-directed movement. Mothers and the nurse actively interacted with each other and the infant with a range of vocal and nonvocal actions. The findings justified the use of unobtrusive, naturalistic observation as a means of assisting practitioners who suffer from an inadequate knowledge-base on pain in children.