Pearls

Introduction

Pain and agitation are common in critically ill patients. As our understanding of these processes in critically ill children has evolved, we now recognize the vital importance of appropriate analgesia and sedation in such patients.⁴⁸ In 1986, the World Health Organization first published its Analgesic Ladder for the management of cancer pain (Fig. 5-1). This paradigm and others like it are now widely accepted as guidelines for analgesia and sedation in all patients. Despite such advances, considerable progress remains to be made. Caregiver education should enhance awareness of the crucial need for appropriate analgesia and sedation in critically ill children. Practice patterns must continue to change to include appropriate analgesia and sedation as essential components of pediatric critical care. Ongoing research must continue to explore the nature of these complex processes and their optimal management.

Fig. 5-1 The World Health Organization Analgesic Ladder. First described in 1986 for management of cancer pain, the World Health Organization Analgesic Ladder has since become a widely accepted paradigm for analgesia and sedation in patients of all ages and in all clinical settings. Interventions are provided concordant to severity of pain and agitation, with openness to adjuvant measures including nonpharmacologic interventions throughout.

(With permission from: Cancer pain relief and palliative care in children. Companion volume to: Cancer pain relief, with a guide to opioid availability. Geneva 1998, World Health Organization. Available from: http://whqlibdoc.who.int/publications/9241545127.pdf. Accessed October 23, 2010.)

In the past, many caregivers mistakenly assumed the immature pediatric nervous system rendered children incapable of experiencing pain or agitation, or caregivers mistakenly believed that children could not safely tolerate analgesics or sedatives. Particularly in pediatric patients, caregivers often interpreted lack of request for analgesia or sedation as indicating lack of pain or agitation, so pediatric patients often received inadequate analgesia. We now know that children of all ages can feel pain and experience pain without expressing the need for analgesia and they can safely receive a wide variety of analgesic interventions. We also know that agitation is common in pediatric patients, and children often receive inadequate sedation.

Assessment of pain and agitation is especially challenging when patients are unable to articulate their experiences and feelings, and analgesia and sedation may be particularly inadequate in these patients. Critically ill children are at risk for significant pain and agitation, and pediatric critical care providers must be vigilant in providing appropriate analgesia and sedation.

Appropriate analgesia and sedation have been shown to attenuate the stress response associated with critical illness, hastening recovery while lessening incidence and severity of complications. Nurses should assess each patient individually, and interventions including pharmacologic agents should be tailored to the patient and the setting. Nurses should regularly assess patient status, including response to interventions, and modify interventions as appropriate.

All pharmacologic agents used to provide analgesia, sedation, and neuromuscular blockade have potential side effects and complications, particularly a risk of respiratory depression and cardiovascular compromise. Risk may be higher in pediatric patients, especially when they are developmentally immature or medically fragile.⁵⁴ Ongoing patient monitoring is essential.

Anatomy, physiology, and embryology of pain

Pain is a complex phenomenon, representing the interaction of many anatomic pathways, physiologic processes, and psychosocial factors. Pain has thus proven remarkably difficult to define, particularly in children. A widely accepted definition of pain is that suggested by the International Association for the Study of Pain: an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. This definition underscores the degree to which pain is a highly personal and subjective experience.

Clinical care of patients in pain is complicated by lack of objective indicators: no vital sign, radiologic study, or laboratory value can reliably quantify or even indicate pain. Except perhaps in the setting of malingering or drug-seeking, rare in pediatric practice, the best clinical approach is usually to accept the patient’s description or indication of pain as truthful and accurate, and to provide analgesia as appropriate.

Nociception

Nociception is the normal process through which pain is experienced (Fig. 5-2). Nerve pathways underlying pain sensation in humans are fully developed at term (see Anatomy, Physiology and Embryology of Pain in the Chapter 5 Supplement on the Evolve Website). Most pain in critically ill children is nociceptive in nature and tends to respond to conventional antinociceptive analgesics.

Fig. 5-2 Simplified diagram of the neuroanatomy of nociception. 1, Transduction of painful stimuli occurs with activation of peripheral nociceptors. 2, Transmission along first-order primarily A-delta (δ) and c-fibers carries nociceptive input to the dorsal horn of the spinal cord, and from there via second- and third-order neurons, chiefly to the contralateral thalamus and cerebral cortex. 3, Perception occurs when pain becomes a conscious subjective experience. 4, Modulation can affect nociception at any point in this process, for example via descending inhibitory pathways.

(From Lewis SM. Medical-surgical nursing: assessment and management of clinical problems, ed. 8, St. Louis, 2011, Mosby.)

Nociception appears to involve four steps: transduction, transmission, perception, and modulation. Transduction refers to the initiation of pain sensation through activation of sensory nerve endings, or nociceptors. Stimulation above the nociceptor activation threshold causes depolarization of the nerve cell membrane, with subsequent propagation of a nerve impulse, or action potential, along the sensory nerve fiber. Nerve cell depolarization, propagation of the action potential, and subsequent repolarization all result from transmembrane flow of ions through channels in the nerve cell membrane.

Transmission refers to the propagation of a nerve impulse, or action potential, along sensory nerve fibers of the peripheral nervous system to the dorsal horn of the spinal cord, and from there to other locations in the central nervous system. Peripheral transmission relies primarily on two types of sensory nerve fibers, A-delta (δ) and c-fibers. A-delta fibers are larger, high-threshold, myelinated fast fibers that transmit fairly localized, acute, sharp pain. The c-fibers are smaller generalized-stimulus unmyelinated slow fibers that transmit less well-localized dull or aching pain. The c-fibers can remain stimulated, even after cessation of painful stimuli, and can play an important role in chronic pain.

Nociceptive sensory nerve fibers terminate in the dorsal horn of the spinal cord, where they synapse with dorsal horn nerve cells. The pain impulse is then carried toward the brain primarily via the spinothalamic tracts. These tracts receive input from sensory nerve fibers in laminae of the dorsal horn of the spinal cord, cross to contralateral spinal cord laminae, and ascend to the thalamus and other higher centers. Further transmission then occurs from the thalamus to the cerebral cortex with extensive cross-connections throughout the central nervous system.

Perception refers to the complex and poorly understood process by which pain becomes a conscious experience. Perception includes the physical sensation of noxious stimuli and the entire conscious experience of such stimuli with attendant emotional and behavioral components.²² Perception is a unique process in each patient and is affected by age, developmental maturity, and underlying medical condition. Perception is also a highly dynamic process, varying among patients and in the same patient at different times.

Modulation refers to modification of pain by other nervous system input. Modulation can ameliorate or exacerbate pain and may explain some of the tremendous variability in subjective pain experience, especially in children. Modulation is a highly complex process and can take place at any point in transduction, transmission, and perception. A particularly important modulatory pathway is the descending pain system, with nerve axons projecting from the brainstem and other supraspinal centers to various laminae of the spinal cord. These descending fibers inhibit transmission of painful sensory stimuli, enhancing analgesia. Anxiety can also modulate pain, causing increased sensitivity to pain and resultant pain-related disability, particularly in chronic pain.⁴⁰

Patient assessment

Recognition and treatment of pain and agitation can be particularly challenging in the absence of reliable objective quantitative assessments on which to base clinical decisions. Patient descriptions can guide analgesic and sedative interventions. However, even verbal children may find it difficult to express this information, particularly in the setting of critical illness. Children may be nonverbal or otherwise incommunicative secondary to age, developmental immaturity, medical illness, surgical procedures, or interventions such as intubation. Caregivers must recognize patient behaviors or behavioral patterns that provide clues to the presence, location, severity, and even cause of pain and agitation, and must monitor changes to guide therapy. No single objective assessment strategy will be sufficient or appropriate for every patient in every setting.³¹

Pain, particularly when acute, may produce evidence of increased sympathetic tone, the so-called fight-or-flight response. This response includes pupil dilation, tachycardia, hypertension, alteration in respiratory pattern, hyperglycemia, and change in emotional state. These indicators, however, are not sensitive in discriminating pain from other sources of distress, and do not reliably quantify or even indicate pain. Limited evidence supports the use of vital signs as indicators of pain, but only in the context of acute onset or acute increase in pain. Significant pain may be present without physiologic evidence of distress.

A common cause of inadequate analgesia and sedation is failure of the caregiver to accept and act on the patient report of pain and agitation. Although the patient report must always be taken in context, it is the most reliable assessment of patient experience and should be considered the standard for patient assessment. Caregivers must respect any patient report of pain and agitation, performing timely assessment and providing appropriate treatment.

In the absence of a patient report, caregivers must perform regular and appropriate objective assessments. Caregiver reliance on subjective impression, gut feeling, or personal belief introduces significant potential for variation and bias among caregivers, often leading to inconsistent or inadequate analgesia and sedation.

Patient or family fears and beliefs can hinder adequate analgesia and sedation. Patients or families may not wish to bother busy nursing staff. Children may deny distress, fearing painful injections or unpalatable oral preparations. Patients or families may hope to facilitate early discharge by minimizing reports of pain or agitation, or by limiting requests for analgesia and sedation. Distress may be regarded as a sign of weakness or failure. Fear of side effects, in particular addiction, leads many patients and families to avoid even appropriate analgesia and sedation. Nurses should address these concerns directly and provide education as necessary.

Caregiver fears and beliefs may also hinder adequate analgesia and sedation. Caregivers may fear providing unnecessary analgesia or sedation, particularly controlled substances. They may misinterpret regulations and legal requirements associated with these medications, or may fear promoting patient addiction. In terminal or palliative care settings, caregivers may fear hastening or even causing death. These issues must be addressed within the healthcare team (see Chapter 3).

Nurses should seek accurate and thorough information from the patient, family, and other caregivers to clarify onset, nature, severity, and time course of pain and agitation, as well as response to interventions. This history is particularly important when patients receive significant pharmacologic analgesia or sedation that can produce tolerance. What has helped? What has been ineffective or made things worse? Do interventions provide complete or only partial relief? How long does relief persist? Incomplete relief can suggest a need for additional interventions or increased medication dose, whereas complete but transient relief may suggest a need for more frequent or longer-acting interventions. The psychosocial component of pain and agitation can be significant, and nurses should assess available social and emotional support systems.

Regulatory guidelines and legal mandates require that patient care regimens be reviewed and reconciled at admission, at transfer of location or level of care, and at discharge. This helps ensure accuracy and efficacy of interventions, and it is particularly important when critically ill children transition to care settings where previous interventions may be unavailable. Continuation of medications at equipotent doses without inadvertent omission or unnecessary addition helps maintain analgesia and sedation while minimizing the risk of inadequate or excessive dosing.

Assessment Tools

Assessment tools typically are scales that can help to quantify pain and agitation in many clinical settings. However, the numeric scores generated must not be taken in isolation; they represent one component of comprehensive patient evaluation, just as vital signs represent one component of physical assessment. Any score must be considered in overall clinical context.

Assessment tools generally rely on subjective patient report, or on objective caregiver evaluation of patients who are unable to provide subjective report. Many assessment tools of both types have been developed for and validated in children. Scores generated using one tool will not necessarily correlate directly with those obtained using another. Caregivers should select an assessment tool appropriate for the patient and use it consistently over time.

Subjective Patient Report

Assessment tools relying on a subjective patient report ask the patient to indicate status on a continuum. Pain scales commonly range from 0 (no pain) to 10 (maximum possible pain); sedation scales vary more widely. Verbal children who are able to count may simply be asked to indicate their pain score on a 0-10 scale. Interactive but nonverbal children, or children unable to count, may be asked to indicate their pain score on a continuum scale using colors, pictures of children, or drawings of faces that represent degrees of distress. Three such pain assessment tools commonly used in pediatric practice are the Oucher! (see Evolve Fig. 5-1 in the Chapter 5 Supplement on the Evolve Website), the McGrath Faces Pain Scale, and the Hicks Faces Pain Scale-Revised (Fig. 5-3). See Patient Assessment in the Chapter 5 Supplement on the Evolve Website.

Fig. 5-3 A recently revised version of a faces scale for use in pediatric patients. Children are asked to point to the face best representing their pain, or for young children, how much they hurt. The six faces can be given scores (from left to right) of 0-2-4-6-8-10 or 0-1-2-3-4-5. Faces represented as more anatomically accurate oval cartoons have improved consistency in scores across diverse ethnic groups when compared to previous versions. The no-pain face is affect-neutral, reducing discrepancies between pain and agitation.

(With permission from Hicks CL, et al: The Faces Pain Scale-Revised: toward a common metric in pediatric pain measurement. Pain 93:173−83, 2001. With permission from the International Association for the Study of Pain (IASP).)

Tools are also available to help children quantify their pain experience through activities such as counting poker chips (the Hester Poker Chip Scale) or coloring an outline drawing of a child (the Eland Color Tool). Use of such activity tools requires patient interaction and caregiver time that may be impractical in the critical care setting.

Objective Caregiver Evaluation

When patients are unable to provide subjective reports, objective caregiver evaluation may be necessary. Although intrinsically less reliable than subjective patient report, objective caregiver evaluation may be the only means available to assess pain and agitation in many critically ill children. Objective caregiver evaluation may also be used judiciously to complement confusing or inconsistent patient reports.

Many assessment tools for objective caregiver evaluation of pain and agitation have been developed for and validated in the pediatric setting. Examples include the FLACC scale (characterizing the patient’s Face, Legs, Activity, Cry, Consolability using specific options) for assessment of pain in nonverbal children (Table 5-2), the COMFORT scale (assessing overall comfort by evaluating specific physical characteristics) for assessment of agitation in critically ill children, and the State Behavioral Scale for assessment of agitation in infants and children during mechanical ventilation.¹⁹ Examples of these tools may be found in Evolve Fig. 5-2 in the Chapter 5 Supplement on the Evolve Website. Additional tools have been reported for use in specific patient populations or particular clinical settings.⁵⁰

Table 5-2 FLACC Scale: Used for Assessment of Pain in Nonverbal Children

Nonpharmacologic interventions

Nonpharmacologic interventions are important adjuncts in pediatric analgesia and sedation. Because pain and agitation include significant cognitive and affective components, the child often responds to cognitive interventions that invoke the child’s imagination, suggestibility, and sense of play. Behavioral interventions help the child focus on relaxation and deep breathing rather than on the pain or painful stimulus. Biophysical modalities may affect nociceptive transmission and have a significant psychological component. Noninvasive and generally inexpensive, nonpharmacologic interventions can provide patients and families a sense of personal involvement in their care.

Family involvement in nonpharmacologic interventions often increases their effectiveness. Although the child may appear more distressed when family members are present, this may indicate that the child is more willing to express pain, fear and agitation in their presence. Children should receive positive reinforcement for engagement in nonpharmacologic interventions, but should never be punished or ridiculed for being frightened or uncooperative. Child Life specialists and other trained professionals, if available, provide valuable support.

Analgesia and sedation are generally optimized when appropriate treatment modalities are combined. For mild to moderate pain and agitation, nonpharmacologic interventions alone may suffice. For moderate to severe pain, nonpharmacologic interventions should complement, but not necessarily replace, pharmacologic therapy. Comprehensive care of critically ill children uses suitable nonpharmacologic techniques in combination with appropriate medications to optimize analgesia and sedation, minimize side effects, and facilitate recovery.

Systemic analgesics

Numerous systemic analgesics are available for use in children (Table 5-3). Systemic analgesics can have a wide range of physiologic effects, particularly in critically ill children. Knowledge of the agents being administered is essential for optimal efficacy and patient safety. Nurses must be aware of expected clinical effect, usual time of onset, likely duration, and potential side effects of each agent administered. Medications ordered on an as-needed basis are effective only when given appropriately with ongoing and recurring patient assessment. Frequent requirement for a drug ordered only on an as needed basis should prompt consideration of scheduled administration and additional interventions. Intramuscular injection is painful and absorption variable; it should be avoided except perhaps in the setting of difficult intravenous access. Although many systemic analgesics can produce sedation, they should not be used primarily for this purpose.

Table 5-3 Systemic Analgesics

Nonopioid Analgesics

Often overlooked, nonopioid analgesics are important pharmacologic options. Nonopioid analgesics alone may be adequate for mild to moderate pain and generally reduce opioid requirement in moderate to severe pain. Nonopioid analgesics generally demonstrate a ceiling effect: exceeding recommended doses does not significantly improve analgesia, but will increase risk of side effects and toxicity. As with nonpharmacologic interventions, nonopioid analgesics are most effective in the context of a comprehensive management plan. Commonly used nonopioid analgesics include acetaminophen and NSAIDs; ketamine is discussed with other systemic sedatives.

Acetaminophen

Acetaminophen is widely used as an analgesic and an antipyretic. It can provide complete analgesia for mild to moderate pain and may reduce opioid requirement in moderate to severe pain, particularly when given on a scheduled basis. Acetaminophen is not an NSAID. Although it is a cyclooxygenase inhibitor, it has virtually no antiinflammatory activity, and therefore has few gastrointestinal, renal, or hematologic side effects. The primary toxicity of acetaminophen is hepatic, seen with both acute and chronic overdose, although renal toxicity has been described.⁴²

Acetaminophen is at least as effective an analgesic as codeine,¹² and it is synergistic with NSAIDs.⁵² Acetaminophen and NSAIDs can be given simultaneously without need to alternate or stagger doses. As with most nonopioid analgesics, acetaminophen demonstrates a ceiling effect: exceeding recommended doses does not significantly improve analgesia and increases risk of side effects and toxicity. Recently, an FDA advisory committee recommended the maximum single adult dose for over-the-counter products be reduced to 650 mg because of risk of hepatic injury.²⁴

Rectal acetaminophen is useful for a patient who is unwilling or unable to tolerate an oral dose. Because rectal absorption is slower and bioavailability is more variable than with oral administration, higher rectal doses are needed for adequate analgesia. Rectal acetaminophen with a loading dose of at least 40 mg/kg has been shown to reduce pain scores and reduce opioid requirement following surgery in children.

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