Chapter 7 Helen Monks, Kate Heaton‐Morley and Sarah McDonald This chapter provides an overview of mechanisms of pain and pain management. There is an emphasis on an individual approach to care provision along with the role others, including family, can play in relieving or alleviating pain. Many definitions of pain exist. The following definition is perhaps one of the most well known. Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. Pain is always subjective. Each individual learns the application of the word through experiences related to injury in early life. (International Association for the Study of Pain [IASP], 1979, p. 250) This definition has since been revised but the original still has great relevance today. It is important to note that pain does not always arise from tissue damage. Pain can arise from relatively ‘normal’ activities such as touch, or even from tissue that does not exist (phantom limb pain). Therefore pain is a complex phenomenon. The definition from IASP (1979) is especially important for children’s nurses because: Therefore, whilst it is possible to generalise and offer some explanations about the way in which children experience pain from an anatomical and physiological perspective, it seems from the definition that much about the way in which pain is experienced is individual and dependant on biopsychosocial factors (Table 7.1). Table 7.1 The experience of individual and biopsychosocial factors Source: Holdcroft & Power 2003. In view of these biopsychosocial factors it is easy to see why the pain experience is considered unique to the individual. This experience relates to the perception as well as the response to pain. Some people are thought of as having a high or low pain threshold – it seems likely that, while some humans have largely equitable physiological factors, other factors such as psychological state can vary enormously and therefore significantly affect the pain experience. For children some of these factors have heightened significance. According to the child’s age and stage of development the cognitive experience of pain may be very different, for example, small children may perceive pain as a punishment and older children may relate pain to more sinister reasons like death and dying (Twycross, Dowden & Stinson, 2013). For children, the experiences and responses formed in early life can have a dramatic impact not just in the present but also for the future. Not least, pain can be an important developmental learning tool; children learn to avoid certain actions because they have discovered that pain is a consequence, in other words warning of danger (Franck, Greenberg & Stevens, 2000). Pain also has an important protective function in terms of warning and diagnosis of illness or disease, as many have painful symptoms (Tortora & Derrickson, 2009). For these reasons this type of pain is often referred to as protective pain. Pain perception, assessment and management in children is a complex subjective issue. A significant factor influencing a child’s pain experience is their developmental stage. This is not limited to age‐related expectations – it includes previous experience, context and the child’s perceptions of the pain experience. In order to offer effective and safe care to those in pain, the nurse is required to describe the anatomy and physiology of pain transmission and sensation, and to understand the key features of nociceptive and neuropathic pain. There are several common myths that are related to the physiology of children’s pain; being aware of these can help provide care that is child‐ and family‐centred. The nervous system is divided into two parts: Pain is a complicated phenomenon. Although much is known about how we feel pain, scientists are still discovering information about the anatomy and physiology of pain. Pain can be broadly divided into two groups: nociceptive pain and neuropathic pain. Essentially there are four stages to the process: Stages 1 and 2 are within the PNS. Stages 3 and 4 are within the CNS. See Fig. 7.1. Figure 7.1 Pathway of pain transmission and interpretation. Source: Nair & Peate 2013. Reproduced with permission of Wiley. McCaffery and Pasero (1999) describe the processes involved for nociceptive pain as: A noxious (harmful, from the Latin noxa meaning ‘harm’) stimulus to the nerve cell is detected by nociceptors (detectors of harm) and transformed into an electrical signal. Noxious stimuli are usually divided into three main types (Nair & Peate, 2013): Nociceptors are free nerve endings of nerve fibres found in almost every tissue in the body (Tortora & Derrickson, 2011). During this phase the information is sent via nerve fibres (A and C, see later) to the dorsal horn in the spinal cord and ultimately to the thalamus in the brain. This is known as the ascending pain pathway. Transmission occurs by way of synapses where information is passed on by complex electrical and chemical processes (Marieb, 2015). This is when pain is felt. The thalamus sends the information to various parts of the brain to be analysed and interpreted. The somatosensory cortex enables pain to be described and located, the limbic system enables emotional response and the reticular system enables action to be taken in response to pain (Melzack & Wall,1996). It is thought that the limbic system is important in the memory of pain which serves as a protective measure for the future (avoidance of experiences that have previously been found to be painful) (Godfrey, 2005). This is the body’s response to pain, in that there are various factors that increase or reduce the feeling of pain. It is the descending pain pathways that are responsible for the increase or decrease in the pain signals. Neuropeptides are released, which are also known as endogenous opioids (the body’s own analgesia). There are three major groups: endorphins, encephalins, and dynorphins (Nair & Peate, 2013). Differences in an individual’s production of these properties could explain why, for the same painful procedure, some people feel levels of pain that are different from those felt by others (Briggs, 2010). Activities such as distraction can inhibit the pain signals (Melzack & Wall, 1965). In this way distraction has long been used as a technique to help children cope with painful procedures (Twycross et al., 2013) and children are sometimes observed to self‐distract by playing fervently when in discomfort, which helps them to cope with their pain (McCaffery & Beebe, 1989). This concept is widely regarded to be explained by the gate control theory (Melzack & Wall, 1965), which is described later in this section. The ascending pain pathways (Fig. 7.2) originate from the spinal cord and are primarily responsible for sending information to the brain. This pathway is divided into three tracts. Two are specifically involved in transmission of pain impulses to the brain: the spinothalamic tract and the spinoreticular tract (Twycross, Dowden & Bruce, 2009). Figure 7.2 The ascending pain pathway. Source: Nair & Peate 2013. Reproduced with permission of Wiley. Once the nociceptors are stimulated and a pain message (impulse) is generated, it travels by way of the ascending pain pathway toward the thalamus in the brain, where it is subsequently analysed and interpreted. The pathway consists of first‐, second‐, and third‐order neurones that pass the message on consequentially: Neurotransmitters convey the message between the neurones. A‐delta fibres and C fibres are first‐order sensory fibres (the first wave of communication). The speed at which the message travels depends on the diameter of the fibre and whether the fibre is myelinated or not (Table 7.2). Myelinated nerve fibres have an axon which is encased in a lipid covering that acts as an insulation, helping to increase the speed of travel. This is where the terms white and grey matter originate: in preserved brains myelinated parts (axons) appear white and unmyelinated parts (cell bodies and dendrites) appear grey (Colbert et al., 2012) (Fig. 7.3). A‐delta fibres are larger in diameter and are myelinated whereas C fibres are smaller in diameter and not myelinated. Hence the capability of C fibres to conduct messages is slower than A‐delta fibres (Nair & Peate, 2013). This is thought to provide the basis for the theory that pain is felt in two waves, for example, when you stub your toe – the first being the initial sharp pain and the second being the dull pain that follows (Tortora & Derrickson, 2011). Table 7.2 Size and speed of first‐order sensory fibres Source: Nair & Peate 2013. Figure 7.3 Basic structure of myelinated and unmyelinated nerve fibres. Source: Nair & Peate 2013. Reproduced with permission of Wiley. This is where the messages about noxious stimuli are processed quickly and in a particular way in order to produce a rapid protective motor response, such as lifting a foot up quickly if a sharp object is stepped upon. As the term suggests, a reflex is elicited to force the body away from the harmful stimulus. Two neurones are involved in this process: a sensory (afferent) neurone and a motor (efferent) neurone. The noxious stimulus triggers a sensory impulse which travels to the spinal cord in the usual way but here two synaptic transmissions occur at the same time: one travels as normal to the brain to be analysed and interpreted; the other is transmitted to an interneurone which transmits to a motor neurone, which in turn, produces a motor response (Marieb, 2015). Descending pain pathways originate within the brain and can inhibit ascending nerve signals. Therefore it is within the descending nerve pathway that modulations occur and it is here that Melzack and Wall’s gate control theory (1965) can be illustrated. A number of theories exist to explain how pain is experienced but the one that continues to hold widespread support is the gate control theory (Fig. 7.4) proposed by Melzack and Wall in 1965. Figure 7.4 The gate control theory of pain. Source: Nair & Peate 2013. Reproduced with permission of Wiley. Simply speaking, the theory is that the pain impulse has to pass through a theoretical gate to enable the brain to receive, perceive and interpret the impulse as painful. Broadly the theory works on the basis that stimulation of A‐delta fibres and C fibres pushes the gate open and the stimulation of A‐beta fibres pushes the gate closed, but that also the presence (or absence) of other factors like fear or distraction may open or close the gate (McCaffery & Beebe,1989). As certain constituents of the message push the gate open, the impulse is allowed to travel to the brain, and pain is felt. In the same way, other factors may be present which inhibit the opening of the gate (or close it after it has been opened) leading to a lack of perception of pain or having the effect of relieving the pain. The actual mechanisms involved are very complex and comprise a complicated interplay involving chemical and electrical reactions between all the connections involved (Marieb, 2015). It is clear that the perception of pain is a complex phenomenon. Children’s pain has additional complexities particularly concerning anatomical structures, which in some cases are not fully developed, along with developing emotional and cognitive states. Unfortunately this can give rise to some unfounded and incorrect assumptions about children’s pain, which can lead to significant mismanagement. Some myths relating to the assessment and management of children’s pain will be addressed later in this chapter but two common myths related to the anatomy and physiology of children’s pain are noted here. The pathophysiology of neuropathic pain is not as clearly understood as nociceptive pain and consequently is often more difficult to assess and manage (Twycross et al., 2009). Neuropathic pain is the abnormal processing of sensory input, perhaps due to damage to the peripheral or central nervous system (McCaffery & Pasero, 1999). In this way a stimulus that is normally felt as a non‐painful sensation, for example, the light stroking of a hand, can be felt as extremely painful (McCaffery & Pasero,1999). There are many types of pain documented but acute and chronic are two of the types most commonly referred to. Melzack and Wall (1996) describe the characteristics of acute pain as the combination of pain, tissue damage and anxiety, but there is (at some point) recovery. Modern definitions of acute pain build on this further: Acute pain may be defined as pain that subsides as healing takes place, that is to say, is of a limited duration and has a predictable end. (Royal College of Nursing [RCN], 2009, p. 8) By contrast Melzack and Wall (1996) note that chronic pain persists after healing has occurred, is no longer a symptom of injury or disease, and has no useful function. Although much more is known about chronic pain these days, the definition remains rather more nebulous than that of acute pain, but there is a general view that pain is considered chronic when it has persisted for longer than 3 months (IASP, 2011). There are a number of common approaches to pain assessment. The nurse needs to understand the context of the pain experience for children and young people, and be able to identify appropriate validated pain assessment tools for infants, children and young people. It is widely acknowledged that pain is a biopsychosocial experience that is made more complex by the subjective nature of the experience of pain through the life span. It is therefore difficult to truly relate to what another individual is experiencing – a headache will be interpreted differently by different people. This phenomenon is made more complex when attempting to assess pain in infants, children and young people due to their age, development, communication abilities, previous experience (or lack of), gender, ethnicity, cultural and family influences. Acute pain occurs from noxious stimuli and may be experienced by children in the form of accidents and injury, surgical interventions, and some procedural events, such as dressing changes and phlebotomy. Chronic, persistent or recurrent pain derives from numerous complex stimuli and can be linked to long‐term conditions such as sickle cell disease or juvenile idiopathic arthritis. Common types of recurrent pain in children and young people are headaches, abdominal pain, back pain and musculoskeletal pain (King et al., 2011). Children have exposure to different painful experiences at different stages of their development. They adapt to these experiences and consequently alter their perceptions, responses and coping strategies to the pain experience. An understanding of the phenomenon of pain and its assessment developed first from an adult perspective (Kortesluoma & Nikkonen, 2006). More is being understood about the child’s perception of pain, but it should be acknowledged that each child and family are individual and may not exhibit or report their pain in the same way as another. Exploring this phenomenon through a biopsychosocial perspective is essential and becomes a more valid assessment when this is supplemented by incorporating knowledge of the cognitive development of the child. Neonates and infants respond to pain in a physiological and behavioural manner. This may result in bradycardia and/or apnoea, and the cry may be intense and high pitched with stiffening of the body and a grimacing expression on the face. Repeated painful stimuli may have consequences on growth, development and susceptibility to infection (Boxwell, 2010). It is imperative that the physical dimension of pain is anticipated and treated prophylactically. For the pre‐school child the physical pain and context of events are important – pain during rough play while children are enjoying themselves may be brushed off and attention to it dismissed. However, the same level of pain inflicted while the child is frightened or fatigued may have a different response. The expression of pain here is predominantly behavioural: anger, aggression, crying, and physical withdrawal or over‐activity (Twycross & Smith, 2006). Pre‐school children may be incapable of understanding cause and effect and have little concept of time, and the significance of associated events often takes precedence over physical pain. Indeed, the child may find separation from loved ones more ‘psychologically’ painful than physical pain or illness (Carter & Simons, 2014). Therefore minimising the psychological distress becomes of equal importance to the relief of physical pain. Often the presence of a well‐loved cuddly toy or a sticking plaster with a favourite character on it will be the child’s pain relief of choice as psychological comfort is as important as physical comfort. As children develop and progress through school their cognitive development becomes more reasoned and the development of logical thinking is evident. The school‐age child has increased language and verbal skills although age is not a reliable indicator of cognitive ability. Indeed, the child may suffer psychological stress alongside illness and the pain experience and, as a result, may regress developmentally. In addition, some children are predisposed to immaturity and may fantasise about internal body processes and disease, which can result in increased anxiety levels and enhanced perceptual awareness (Twycross & Smith, 2006). For example, children may exhibit surprise once a plaster is removed from a broken leg to see that their leg is actually still there and the magic plaster made it better. Carter and Simons (2014) warn that a child’s imagination can summon up dramatic and frightening scenarios due to pain and fear being intertwined. Children’s version of logic can inadvertently encourage frightening misconceptions which may be enhanced by their peer group or family members – such as the 6‐year‐old boy who was helpfully told by another boy that his tonsils would be removed by slitting this throat open! As a consequence of misconceptions, post‐operative pain may be challenging to manage. Adolescents are more able to think in abstract terms and understand the nature of the pain experience, and are more able to communicate their feelings. However, great care should again be taken with assumptions based on age, as young people may be emotionally immature and lack the necessary coping skills. Forgeron and Stinson (2014) suggest that anxiety, depression, self‐esteem and emotional states can affect how the young person perceives pain. Although often independent, the adolescent may be in need of great compassion and understanding. Cognitively impaired children present a challenge for parents and carers alike because of their altered processing and communication abilities. It is sometimes difficult to know if they perceive pain and sensation in the same manner as a child without impairment. McDonald and Cooper (2001) suggest that children with physical and learning disabilities may show higher pain thresholds and their autonomic, motor and sensory systems may have an effect on the pain experience meaning. This may indicate that they have reduced sensitivity to pain. Because of the communication difficulties with this group of children, it is imperative that accurate pain assessments are performed regularly in collaboration with carers who know them and their behaviours well. It is generally accepted that alongside cognitive and psychological factors, such as fear, anxiety, emotion and fatigue, the attitudes of the child and family toward pain and illness are of significant consequence (Schechter, Berde & Yaster, 2003). The meaning and behavioural norms in response to pain may be learned from parents, family members and experiences in the social environment. Glasper and Richardson (2006) define this as culture, meaning that it is dynamic, helps to identify life habits and customs, and gives the child and family a group identity and a pattern for living. Culture is important and thoroughly internalised. Almost three decades ago, McGrath (1990) identified that when reporting pain, boys were expected to ‘play it away’ while girls were advised to rest, given medication and afforded sympathy. This may have given credence to the assumption that giving attention may lead to the child developing sophisticated somatic complaints, and that an excessive sustained reliance on others or on medication may result in an inability to use natural capacity to suppress pain. Research by Perquin et al. (2000) established that girls aged 12–14 experienced the most pain and reported it more than boys. The relationship of reporting pain with age and gender must be borne in mind when performing pain assessment. East (1992) considers cultural aspects to be of significance when children and families deal with and report pain. British children tend to be stoical about their pain, but prefer to have company while in pain, whereas Australian children often prefer to be alone. The Irish are said to be stoical also, but may be more concerned about the future consequences of their pain. Edwards et al. (2001) report that African Americans use more distraction and praying/hoping to cope with pain. The Muslim view is that one is purged of one’s sins through pain and illness (Sheikh & Gatrad, 2001). Carter (1994) claims that nurses’ culture affects their perception of a child’s pain and it should also be acknowledged that there may be a difference in the level of educational background between families and the healthcare team. It is clear that assessing pain in infants, children and young people and their families is a complex issue and demands a holistic, non‐judgemental approach. Care should be taken to be mindful of the psychosocial aspects mentioned earlier before moving on to specific assessment techniques outlined in the following sections. Table 7.3 Validated, age‐appropriate pain assessment tool suggestions Source: Adapted from www.rcn.org.uk/childrenspainguideline. A more comprehensive and detailed algorithm appears within the guidelines with evidence for the validated tools cited.
Pain and pain management
Aim
Introduction
Characteristics of host
Biological
genetics, sex, endogenous pain control
Psychological
anxiety, depression, coping, behaviour
Cognitive
Disease
History
Present disease
Environment
Socialisation
Lifestyle
Traumas
Cultural
expectations, upbringing, roles
Anatomy and physiology of pain in children
Nociceptive pain
Transduction
Transmission
Perception
Modulation
Ascending pain pathways
Sensory fibre
Diameter (µm)
Myelinated
Speed of conduction (m/s)
A‐beta (Aβ) fibres
6–12
Yes
35–75
A‐delta (Aδ) fibres
1–5
Yes
5–35
C fibres
0.2–1.5
No
0.5–2 
Reflex arc
Descending pain pathways
Gate control theory
Common myths about anatomy and physiology of children’s pain
Neuropathic pain
Acute and chronic pain
Acute pain
Chronic pain
Common approaches to assessing pain in infants, children and young people
The pain experience for children
Cognitive development and the perception of pain
Neonates and infants
Pre‐school child
School‐age child
Adolescents
Cognitively impaired child
Gender and cultural aspects of pain in children, young people and their families
Methods of pain assessment (see Table 7.3)
Age
Tool
Infants and neonates
Comfort
Crying, Requires O2 for saturation above 95, Increased vital signs, Expression and Sleeplessness (CRIES)
Premature Infant Pain Profile (PIPP)
Neonatal Infant Pain Scale (NIPS)
Toddlers and young children
Faces, Legs, Activity, Cry, Consolability (FLACC)
Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS)
COMFORT
Visual analogue scales (such as faces scale)
Older children and young people
Visual analogue scales (such as faces, numbers)
Poker chip
Colour analogue scale
Word descriptor scale
Children with cognitive impairment
Faces, Legs, Activity, Cry, Consolability (FLACC)
Paediatric pain profile (PPP)
Non‐communicating children’s pain checklist revised (NCCPC‐R)
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
