During the past decade, attention has focused on the special pain problems of infants, children, and adolescents, so that there have been advances in our understanding of children's pain perception and in our ability to alleviate suffering.1'6 One of the most remarkable advances has been the realization that the system that mediates children's pain is subtle and complex. We now know we cannot completely control pain by gearing interventions solely to tissue damage. Instead, we also must modify situational factors that affect a child's nociceptive processing. Thus, pain management should begin with a careful assessment to identify the pain source (usually tissue damage) and to evaluate factors that exacerbate acute pain or cause recurrent pain.
A comprehensive pain assessment is necessary to establish a correct clinical diagnosis. Subsequent assessments of pain intensity enable us to evaluate which treatments are most effective for reducing different types of pain. Pain assessment should be an intrinsic component of pediatrie practice, but few clinicians regularly use validated measures to evaluate and monitor children's pain. Anecdotal reports suggest physicians lack information about practical, ageappropriate pain measures. In view of the diverse array of pain measures for infants and children, it is understandable that there is some uncertainty about which measures are best for clinical use. Yet, the best pain measures may be deceptively simple. The addi' tion of a few structured questions to the usual pain history and the use of a simple quantitative rating scale can enable clinicians to obtain accurate information about the sensory characteristics of a child's pain (onset, location, quality, intensity, and duration) and about the critical situational factors (cognitive, behavioral, and emotional) that modify pain perception. This information enables selection of the most appropriate pharmacological and nonpharmacological interventions for each child. Accurate pain assessment can be convenient and fundamental. This article describes a practical approach for assessing children's acute, recurrent, and persistent pains, consistent with our understanding of children's pain perceptions.7
Figure 1.A model showing the factors that modify children's pain perception.
THE NATURE OF A CHILD'S PAIN
Accurate pain assessment requires careful consideration of the nature of a child's pain. A child's pain is not merely an immediate and inevitable consequence of tissue damage. Moreover, the strength of the pain is not predetermined by the extent of tissue damage. Like adults, children can experience pain without tissue injury or apparent injury, they can sustain injury without experiencing pain, and they can experience different pains from the same type of tissue damage. Children's nociceptive systems are plastic, in that they have the capacity to respond differently to the same amount of tissue damage. We now know that children's pain perception depends on complex neural interactions, where impulses generated by tissue damage are modified by ascending systems activated by innocuous stimuli (eg, touch) and descending pain-suppressing systems activated by situational factors (eg, a child's expectations).8,9
A model depicting the factors that modify children's pain perception is shown in Figure I. Tissue damage initiates a sequence of neural events that may lead to pain, but many factors can intervene to alter neural transmission and modify pain perception. Some factors are stable for a child, such as gender, age, cognitive level, previous pain experience, family, and cultural background. These shape how children interpret and experience the various sensations caused by tissue damage. In contrast, the cognitive, behavioral, and emotional factors vary dynamically depending on the situation. These situational factors represent a unique interaction between the child experiencing pain and the context in which the pain is experienced. Even, though the pain source may remain constant, the particular combination of these situational factors is unique for each occurrence of pain. These factors exert a profound impact on children's pain. But, unlike the child characteristics listed, health professionals can modify situational factors in their interactions with children so as to dramatically lessen their pain. Situational factors account for why the same tissue damage can evoke different pains and partially explain why proven analgesics vary in effectiveness for different children and for the same child at different times. In addition, situational factors can be the primary cause of certain recurrent and persistent pains for otherwise healthy and pain-free children.
Cognitive factors include children's understanding about the pain source, their ability to control what will happen, their expectations regarding the quality and strength of the pain, their focus of attention (ie, distracted away from the pain or focused on what is happening), the relevance or meaning of the situation, and their knowledge of pain control strategies. In general, pain can be reduced by providing ageappropriate information about the pain (especially during procedures or postsurgically), control through choices (ie, site of injection and active participation), a rationale for what is happening and what can be done to reduce pain, and information about painreducing strategies.
Behavioral factors include children's overt actions (eg, crying or using a pain control strategy), parents' and health staffs responses (eg, displaying frustration or calmly providing encouragement for children to use pain control strategies), the extent to which children are physically restrained, and the broader effects of pain on children's lives such as their ability to attend school, participate in sports and social activities, and assume family and household responsibilities. Like cognitive factor, behavioral factors share a powerfal modulating role in children's pain. Some behaviors reduce pain and promote a healthy recovery, while other behaviors may initiate, exacerbate, or maintain children's pain.
Behavioral PaIn Measures*
Children's emotions affect their ability to understand what is happening, to cope, to understand their behavioral responses, and subsequently, their pain experience. Children's immediate emotional reactions to pain may vary from a relatively calm acceptance to frustration, anxiety, fear, anger, or sadness. In general, the more fearful and anxious a child is, the stronger and more unpleasant die pain. Moreover, children's emotions are influenced by myriad cognitive and behavioral factors. When children lack understanding, control, and simple pain control strategies, their emotional distress increases and their pain intensifies. What children know, do, and feel all affect their pain. Although the causal relationship between an injury and a consequent pain sensation seems direct and obvious, even acute pain from an injection is modified by many situational factors. Thus, it is essential to recognize and evaluate the impact of these factors in order to optimally relieve any type of pain that children experience.
PAIN MEASURES FOR CHILDREN
As a consequence of intensive research throughout the past decade, many measures for assessing children's pain have been developed. Like adult pain measures, children's pain measures may be classified as behavioral, physiological, or self-report, depending on the nature of the response that is measured - a child's overt distress (eg, grimaces, cries, and protective guarding gestures), a child's physical state, (eg, heart rate, sweat index, blood pressure, and cortisol level), or a child's direct self-report (eg, words, numerical ratings, and drawings). The criteria for an accurate pain measure are similar to those required for any measuring instrument - validity, reliability, and minimal bias. A pain measure must be valid, in that it unequivocally measures a specific aspect of a child's pain (eg, intensity, so that changes in a child's pain rating represent a meaningful and proportional change in the child's pain experience. The measure must be reliable, in that it provides trustworthy and consistent pain ratings that do not change over time. The measure must be relatively free from response bias, in that children use it similarly regardless of how they may wish to please adults or how adults administer it. In addition, pain measures should be practical for assessing different types of pain (accute, recurrent, and persistent) with many different children (according to age, cognitive level, and cultural background) and versatile for use in distinct clinical settings (clinic, postoperative recovery room, emergency room, and home).
Behavioral Pain Scales
Behavioral pain scales record how children respond physically when they experience pain. A trained observer watches children and records behaviors that suggest discomfort (eg, crying). Often, behaviors are assigned numbers (usually O to 4) to represent different intensities of distress. Clinicians use the scale by observing children, noting the appropriate distress behaviors, and adding the scores to determine the child's pain rating. Table 1 lists the behavioral pain measures available for infants and children.
Although these scales can provide a reliable, valid, quantitative index of children's overt distress, what children do (particularly during a short observation period) does not indicate reliably how strong their pain feels. Children do not exhibit distress in direct proportion to the intensity of their pain, so that pain scores on behavioral measures do not always correlate with children's own reports of pain strength.10 Some children behave stoically despite pain whereas others may exhibit overt distress because they are afraid or anxious. Moreover, like adults, children's behaviors vary with the type and location of their pain. Thus, different behavioral pain scales are required for the different types of pain that children can experience. Although an assessment of relevant behavioral factors is an important component of a thorough pain assessment, this information can be obtained within the clinical interview. In general, behavioral scales are not adequate or practical measures of a child's pain.
Physiological Pain Scales
Physiological parameters that have been tested as pain measures include heart rate, respiration rate, blood pressure, palmar sweating, cortisone levels, transcutaneous oxygen, vagai tone, and endorphin concentrations.2-1' Changes in these parameters reflect a generalized and complex response to stress inducing stimulation, rather than a specific localized response to pain intensity. Physiological states provide useful information about general distress levels, but they are not optimal measures of children's pain.
Figure 2. Apain diary fora 13-yearold girl with recurrent headaches. At the time of the assessment, she experienced four headaches per month and daily stomachaches. The happy faces indicate painfree days and BS indicates bad stomachaches. She did not experience any headaches during the month.
Self-Report Pain Scales
Behavioral and physiological signs are relied on to assess pain in infants and children unable tis} communicate verbally. They provide indirect estimates of pain because we can only infer the presence of strength of pain from the child's behaviors or physical states. In contrast, self-report measures provide direct information about many aspects of a child's pain (the sensory characteristics, the aversive component, and contributing cognitive, behavioral, and emotional factors). At present, self-report measures represent the gold standard for assessing children's pain.
Children learn specific words to describe the various aspects of all their perceptions (eg, words to denote different sounds, colors, and tastes). Similarly, they learn a vocabulary to describe their pain so that they can communicate meaningful information about their experience. Their understanding and descriptions reflect age, cognitive level, and previous pain experience. Children first begin to verbalize the hurting aspect of pain as toddlers. As they mature, they describe their pain according to both its unpleasant hurting aspect and its sensory attributes - the quality aching, burning, stinging, throbbing, sharp, or dull), intensity (weak to strong), duration a few seconds to years), location (various body regions), and frequency (constant or episodic). Children's descrip-
tions provide the richest source of pain information for clinicians. Children can express what they feel, describe what they do, can use diaries to record prospectively how often pain occurs (Figure 2), and use pain intensity scales to rate its severity.
Children's interviews are ideally suited for obtaining concise information about a child's pain problem, pain history, and the factors that influence their pain. When clinicians are treating many children with similar pain problems (eg, recurrent headaches), they should conduct structured interviews by asking all children a set of standard questions in a similar manner. This format ensures that they will obtain the same information from all children so that they can gradually learn to identify which children (on the basis or" their pain history and answers) will respond best to which treatments. Table 2 lists the essential features of a pain interview and assessment, including some guidelines for interpreting children's answers. Interviewers must be trained to pursue children's hesitant or superficial responses to elicit comprehensive and accurate information.
Three structured pain interviews and questionnaires have been developed for children. The Pediatrie Pain Questionnaire includes eight questions about the pain history, pain language, the colors children associate with pain, the emotions they experience, their worst pain experiences, the ways they cope with pain, the positive aspects of pain, and the location of their current pain.12 The Varni/Thompson Pediatrie Pain Questionnaire includes visual analog scales, color-coded rating scales, and verbal descriptors to provide information about the sensory, affective, and evaluative dimensions of children's chronic pain, as well as information about the child and family's pain history, symptoms, pain relief interventions, and socioenvironmental situations that may influence pain. It is completed separately by the child, parent, and physician.13 The Children's Comprehensive Pain Questionnaire (CCPQ) was developed as a structured interview for children with recurrent or persistent pain. The CCPQ provides information about the sensory dimensions of pain and the contributing cognitive, behavioral, and emotional factors.2 It contains both open-ended and supplied format questions as well as analog rating scales, and can be used to compare pain profiles to evaluate new therapies (Table 3).
Fain Intensity Rating Scales
Many pain intensity rating scales have been validated for children including the poker chip, number, thermometer, visual analog, and colored analog scales. Children choose a level on the scale that best matches rhe intensity of their own pain (ie, number of poker chips, a number, a level on a thermometer varying from O to 100, or a position on a visual or colored analog scale). These scales are easy to administer and require only a few minutes. Ordinarily, children older than 5 years can. use any of these scales, but the poker chip method can be used by younger children.14 Facial scales have also been designed in which children select a face from a series varying in emotional distress. However, facial scales may be better measures of a child's emotional distress, in that they tap the affective or unpleasantness dimension of pain.
Number rating scales typically consist of vertical rulers graduated from O to 10 or O to 100. These scales often are presented as large "pain thermometers" in which children select a height of mercury to match their pain intensity.15 Zero usually is designated as "no pain," whereas the other endpoint is designated as "most pain possible."
Several facial scales, comprised of a series of faces varying in emotional distress, have been developed.7 Children select the face that best matches their own pain and distress. Often, the faces are assigned pain values from O, 1, 2, etc to reflect increasing pain. However, the assigned O, 1, 2 pain values may not accurately reflect the true differences in children's perceptions of pain, ie, children may perceive pain face 2 as more distressing than pain face 1, but not necessarily as twice as distressing. The Oucher Scale consists of six photographs of a young boy's face displaying different expressions of pain.16 Hie faces, ranked from O to 5 to represent increasing pain levels, are placed along a thermometer scale. The facial scale is intended for use by younger children, while the number scale can be used by older children.
Principal Features of a PaIn Assessment
Visual analog scales are a simple and versatile method for assessing pain intensity in children. These are usually 10-cm lines, with endpoints marked as "no pain" and "strongest pain imaginable." Children mark the line so that the length from the left endpoint to their mark matches the strength of their pain. Although deceptively simple, these scales have been validated as excellent tools for measuring different perceptions. These scales ave versatile as measures of acute, recurrent, and persistent pain. In addition, visual analog scales can be used to assess other aspects of pain, such as unpleasantness, sadness, and perceived control. As a consequence, they are an essential component of many structured interviews and pain questionnaires for children with recurrent or chronic pain. Of special note, studies have shown that visual analog pain scales have ratio properties,17 so that the pain values obtained reflect accurate differences in an individuals pain perception, eg, pains rated as 10 are twice as strong as pains rated as 5.
Questions From the CCPQ (for Recurrent Headaches)
Because traditional visual analog scales (black lines drawn on paper) are onerous for routine use, (staff must first measure a child's response with a ruler), a more convenient scale was designed. This pötket-sized tool includes a colored analog scale to assess pain intensity and a facial scale to assess affect. Both scales have numbers on the back so that the person administering it can quickly note the numbers that represent a child's pain. Initial validation studies have shown that the new instrument has equivalent psychometric properties as the visual analog scale, but is easier to use.(McGrath PA, Seifen CE, Speechly KN, et al. Unpublished data.) Based on results of validation studies and our own clinical experience, we are now using the colored analog scale instead of the visual analog scale.
Children can use diaries and logs to record different aspects of their pain, enabling therapists to learn more about the specific temporal pattern and monitor the effectiveness of different analgesic interventions, as illustrated by the pain log for a child with recurrent headaches in Figure 3. Children oîder than 5 years of age complete a separate pain log (with parental assistance as needed) for each headache so the therapist can identify pain triggers, modify behaviors that exacerbate pain, and evaluate specific analgesic interventions.2 Children with persistent pain can use the same type of diary to monitor their pain at different periods throughout the day.
A PRACTICAL APPROACH FOR CLINICAL PAIN ASSESSMENT
Pain management for all children involves strategic planning based on a careful and thorough pain assessment. The clinical objectives in assessing a child's pain are to identify the source of noxious stimulation, assess the sensory aspects (usually to facilitate diagnosis and monitor treatment efficacy), and determine the extent to which other factors for acute, recurrent, and persistent pain guides the selection of the specific pain measures needed to achieve clinical objectives.
The following case histories illustrate how we use structured interviews and pain rating scales (diaries and analog scales) to assess pain and develop a treatment plan.
A 9-year-old girl was referred to the clinic because she was experiencing increasing distress during invasive procedures (ie, blood sampling, intravenous insertions, and intramuscular injections). The assessment consisted of brief individual interviews with the child and her mother. The child was asked about her condition (early puberty), the purpose for necessary treatment, the pain caused by various procedures, and the type of coping strategies she used. The intake information from her mother included information about the child's life and interests, what happened during procedures, how her parents encouraged her to behave, and what they had told her about procedures, diagnosis, and prognosis. At the time of the assessment, the child was unable to sleep prior to clinic visits and »as quite distressed before and during procedures. Although her parents were very supportive, they had begun to respond inconsistently to her distress by alternating between being overly supportive and simply telling her to stop it because she was making it harder for herself. The assessment results indicated several cognitive, behavioral, and emotional factors were responsible for intensifying pain and distress, as listed in Table 4.
Thus, we designed a simple pain management program. The treatment objectives were to:
* discuss the pain model to show how situational factors increased pain,
Figure 3. A pain log for children with recurrent headaches.
* ensure she had an age-appropriate understanding of her diagnosis and the need for blood samplings and invasive procedures (using photo albums and practice sessions to lessen anxiety),
* review pain systems and pain gates, so she could understand simple methods to lessen pain,
* demonstrate (using a biofeedback machine) how increasing tension and nervous feelings can lead to tighter muscles so that any procedure can cause greater pain,
* teach her how to reduce anxiety during procedures, using simple distraction techniques
* increase her control by participating in some aspects of the procedures,
* encourage use of these pain control strategies, by using sticker rewards, and,
* encourage her parents to consistently promote pain control strategies during procedures.
After two sessions, she was able to use these strategies. Her distress and anxiety lessened, and her pain decreased dramatically.
A 13 -year-old boy was referred for assessment of persistent headaches after he experienced a head injury during a hockey game. Medical examinations revealed no abnormalities, but his headaches increased in intensity 6 months prior to his assessment, coincident with an extremely stressful period as he prepared for tryouts in an advanced hockey league. The assessment consisted of structured interviews with him and his mother, completion of the CCPQ, and a pain diary to monitor the frequency and intensity of his headaches for I month. The results showed he had a moderate pain problem consistent with a recurrent pain syndrome.
He participated in our treatment program for adolescents with recurrent pain syndrome, in which the objectives were: to teach him about pain systems, recurrent pain syndrome, and headache triggers; to assist him to identify and resolve stressful situations; to increase his problem-solving skills; to improve his eating and sleeping habits; and to encourage his parents to decrease the attention he received when he complained about pain, while increasing attention when he used strategies to reduce pain and cope with stress. After three sessions (one per month), his headache frequency decreased so that he did not have any headaches in the preceding month, despite several stressful incidents.
A 12 -year-old-girl was referred for assessment of persistent pain in her left shoulder and left arm indicative of reflex sympathetic dystrophy. The purpose of her pain assessment was to evaluate the sensory characteristics of her pain, to identify the primary and secondary factors responsible, and to determine whether her pain pattern was characteristic of neuropatie pain, specifically reflex sympathetic dystrophy. Her assessment procedures were similar to those described for recurrent pain, however, sensory testing is often included to determine atypical sensitivity to tactile and pain stimulation.
She had experienced a sudden sharp pain in her shoulder when she was throwing a heavy object. Her pain became progressively stronger during the next 6 weeks. Although she described her pain as consistently strong, she rated the intensity quite low on the colored analog scale. Since pain onset, she had not attended school and had stopped all physical activities, including her household responsibilities. Prior to the injury, she had been quite active in many sports and had assumed many physical responsibilites at home. She reported that she could not maintain her activities because of her pain and because she must elevate her arm to prevent discoloration (although she did not elevate it throughout the approximately 2-hour pain assessment). She described the aching sensation as similar to pain due to sensitive nerves that she had experienced when she was 10 years old, this pain had required a lengthy period of rehabilitation.
No analgesic medications including opioids had relieved her pain. Ice, rest, and relaxing music made her more comfortable, but did not appreciably lessen her pain. Even though the pain was strong and disabling, she rated the pain affect as very low. In addition to the marked disparity between her pain intensity and affective ratings, throughout the assessment she demonstrated an apparent calm acceptance of this seriousy disabling pain, that no medications effectively relieved. Both she and her mother indicated repeatedly that they understood the injury would require a long rehabilitative period, even though no one had told them this.
The assessment results indicated that she had a severe pain problem, with potential for long-term disability. Her pain pattern was typical of reflex sympathetic dystrophy. Our treatment recommendation was that she participate in a general rehabilitative program, including exercise, intensive physiotherapy* resumption of normal activities, and supportive counseling for her and her mother to improve their understanding of the complex aspects of this painful condition. Also, she might benefit from additional nerve blocks (a previous series had not been successful) and a trial of low-dose tricyclic ant [depressant therapy. The pain therapist reviewed some of the nerve injuries that often precipitate reflex sympathetic dystrophy, explained how pain caused by crushing or compressing a nerve requires a different treatment approach, and discussed that there was great individual variation in physical signs and in recovery period (emphasizing that it was not necessarily prolonged). However, her mother did not accept the assessment results and treatment recommendations, and sought treatment elsewhere.
Acute PaIn Assessment Report
A child's pain is plastic and complex. In order to more effectively alleviate suffering, emphasis must shift from an exclusive focus on the source of tissue damage to a more comprehensive focus that includes factors that modulate pain.
Evaluating a child's pain requires an integrated approach. Clinicians always should ask a child directly about his or her pain experience to determine the sensory characteristics. Clinicians also should assess situational (actors to develop strategies to modify their impact. Then, a child's pain intensity should be measured regularly to monitor the effectiveness of interventions. Interviews, structured questionnaires, and simple rating scales are the primary tools to assess pain for most children older than 5 years of age. For infants, toddlers, and cognitively impaired children, physicians must infer the presence and severity of pain by evaluating changes in children's behavioral and physiological states. Parents and the health professionals who work most closely with children with particular handicaps can provide valuable information about the presence and severity of a child's pain because they often can recognize extremely subtle behavioral cues that indicate distress.
A standardized but flexible approach is necessary to assess a child's pain. Pain assessment, like pain management, is a continuous process. Pain intensity rating scales should be used so children can provide a direct rating of their pain intensity and pain effect.
Patients should receive some guidance about how to use the information from rating scales to develop consistent and objective criteria to know when children require analgesics and then to evaluate the effectiveness of those medications.
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Behavioral PaIn Measures*
Principal Features of a PaIn Assessment
Questions From the CCPQ (for Recurrent Headaches)
Acute PaIn Assessment Report