Pain is reported as being one of the most significant issues for the individual with a wound. Not only can it have a significant impact on quality of life, pain’s intimate relationship with stress means that excessive pain can lead to stress and delayed healing. It is therefore essential that the health care professional understand how pain is best conceptualised, assessed and managed: this is the focus of this chapter. Detailing the pain associated with wounds precedes a description of the Gate Control Theory of Pain. This model highlights the importance of psychosocial variables in the experience of pain and how these components can also be used in the effective management of pain. In order to effectively manage pain it is necessary to assess pain appropriately and this chapter outlines several methods which can be used in wound care. Finally, approaches to pain management are presented.

According to the International Association for the Study of Pain (IASP 2012), pain is defined as

an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

Pain is usually transitory, lasting only until the noxious stimulus is removed or the underlying damage or pathology has healed- this is acute pain. For example, acute pain may be exacerbated during regular treatment due to the need for manipulation; wound cleansing, dressing removal and re-application, debridement (White 2008; Upton 2011a, b).

However, some painful conditions may persist for years. This is chronic pain, as opposed to acute pain that may be experienced for a relatively brief period (e.g. during dressing change). The definition of chronic pain is rather arbitrary, however. The most commonly used definition being pain of greater than 3 or 6 months since the onset of pain (Turk and Okifuji 2002) though others have suggested a 12 month mark (Spanswick and Main 2000). Others apply acute to pain that lasts less than 30 days, chronic to pain of more than 6 months duration, and subacute to pain that lasts from 1 to 6 months (Thienhaus and Cole 2002). Alternatively, a compromise definition is that chronic pain is “pain that extends beyond the expected period of healing” (Turk and Okifuji 2002) and one that will be adopted here. Chronic pain may be an important component of care for patients with wounds given the potential chronicity of their wound and the regular requirement for dressing change.

In addition to the distinction between acute and chronic pain, there are many forms of pain, which may be useful to distinguish here. Hence, nociceptive pain is pain that happens because of tissue damage or inflammation and is caused by stimulation of peripheral nerve fibres that respond only to stimuli approaching or exceeding harmful intensity:

Pain that arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors (ISAP 2012)

Nociceptors are the nerves which sense and respond to parts of the body, which suffer from damage. They signal tissue irritation, impending injury, or actual injury. When activated, they transmit pain signals (via the peripheral nerves as well as the spinal cord) to the brain. This form of pain may be classified according to the mode of noxious stimulation (e.g. “thermal”, “mechanical” or “chemical”). Examples include sprains, bone fractures, burns, bumps, bruises, inflammation (from an infection or arthritic disorder), obstructions, and myofascial pain (which may indicate abnormal muscle stresses). The pain is typically well localized, constant, and often with an aching or throbbing quality. Visceral pain is the subtype of nociceptive pain that involves the internal organs. It tends to be episodic and poorly localized.

In contrast, neuropathic pain is the pain associated with the nervous system and is the result of an injury or malfunction in the peripheral or central nervous system (Treede et al. 2008):

Pain caused by a lesion or disease of the somatosensory nervous system (ISAP 2012)

Peripheral neuropathic pain is often described as “burning”, “tingling”, “electrical”, “stabbing”, or “pins and needles” (Paice 2003). Among the many causes of peripheral neuropathy, diabetes is the most common, but can also be caused by chronic alcohol use, exposure to other toxins (including many chemotherapies), vitamin deficiencies, and a large variety of other conditions. Persistent allodynia, pain resulting from a nonpainful stimulus such as a light touch, is also a common characteristic of neuropathic pain. The pain may persist for months or years beyond the apparent healing of any damaged tissues. In this setting, pain signals no longer represent an alarm about ongoing or impending injury, instead the alarm system itself is malfunctioning.

Finally, Phantom pain is pain felt in a part of the body that has been lost or from which the brain no longer receives signals. It is a type of neuropathic pain and is common in those with amputations (Kooijman et al. 2000).

It has been suggested that the pain that patients experience can be an issue for all irrespective of type of wound (see Table 2.1); whether chronic or acute (White 2008; Woo et al. 2008); or whether nocioceptive or neuropathic in origin (Soon and Acton 2006); or temporary or persistent. Krasner (1995) describes acute pain as cyclic (occurring during regular procedures) or non-cyclic (occurring during manipulation of wounds).

Furthermore since different forms of pain are often treated differently it is important for the health care professional to not only acknowledge any pain, but also correctly identify the type of pain in order to implement an accurate intervention. Finally, it should not be overlooked that wound pain is extremely distressing for patients and can result in the presentation of psychological problems, which can be costly both financially and emotionally for all (Upton and Hender 2012).

Patients have highlighted pain as being a significant stressor (Solowiej et al. 2009). This is particularly worrying when considering the body of research that has demonstrated the negative impact of stress in relation to wound healing (Cole-King et al. 2001; Soon and Acton 2006; Walburn et al. 2009). Hence, there is a need for clinicians and health professionals in the field of wound care to consider the assessment of wound pain, and any resultant stress, throughout the treatment process (see Chap.​ 3). Despite this, some health care providers have, traditionally, neglected pain and the need for its assessment and documentation (Woo et al. 2008). Indeed, many health-related organisations and care providers have highlighted the need for pain management to be incorporated into routine wound care practice. For example, the European Wound Management Association (EWMA) developed clinical guidelines and recommendations that highlighted best practice in relation to wound-pain assessment and management (European Wound Management Association 2002). Additionally, the World Union of Wound Healing Societies (WUWHS 2004) have emphasised the need for minimising wound-related pain. Within this consensus document, the WUWHS recommended the assessment of wound-related pain and its perceived intensity before, during and after dressing procedures. This is in the hope that, if needed, clinicians can review their practice if patients perceive their experience of pain to be of a rating of moderate or more (e.g. a pain score higher than 4 on a scale of 1–10). While clinicians have the tendency to consider would healing to be of utmost importance, patients consistently rate pain to be of most important to themselves.

In order to adequately treat pain, and attempt to negate its adverse effects, it is important to record when it occurs, while also identifying primary causes (White 2008). This would then enable the clinician to determine the most appropriate means for managing such pain including the application of supportive measures. There are a number of tools that can be adopted in assessing patient’s pain throughout the treatment regime (some of which will be discussed later in this chapter). The adoption of these pain assessments would enable clinicians to alter regimes in an attempt to meet the needs of individual patients. Subsequently, the accurate assessment and management of wound pain can establish a basis of trust on the part of the patient, reduce the patient’s overall pain and stress, contribute to patient quality of life (QoL) and increase treatment concordance (Hollinworth 2005; Upton and Solowiej 2010).

There are, as one would expect, various models that have been developed in order to take into account the complex phenomena of pain and it is worth exploring some of these now in order to better understand the concept has been described, and subsequently how best to both assess and manage it (Upton 2012). Attempts at understanding pain have a long history, with one of the first explanations being provided by Descartes in 1644 who:

Conceived of the pain system as a straight through channel from the skin to the brain (Melzack and Wall 1996:126).

In other words, when you hit your thumb with a hammer the hurt and damage from this area is sent up to the brain via one channel that tells you that you are experiencing pain.

This earlier view of pain as a simple linear concept was very popular up until the twentieth century when evidence to suggest that pain was not as simple as a mere linear relationship between injury and perceived pain started to mount up (Melzack and Wall 1996). Not only did evidence emerge that the level of pain was influenced by factors other than extent of injury- for example, personality, culture, anxiety and so on- but there was evidence that individuals with no nerve transmission could still experience pain. People who have lost limbs through amputation often have severe pain in the missing limbs. Thus, in those with phantom limb pain where there are no nerve transmissions but there is pain (e.g. Bosmans et al. 2010; Fieldsen and Wood 2011). Phantom limb pain has no physical basis but the pain can feel excruciating and feel as if it is spreading. Not only is the pain not related to actual tissue damage but not all people who have had a limb amputated experience this pain, or the level of pain may vary from individual to individual (Bosmans et al. 2010).

These pieces of evidence – the variation in medication’s success at reducing pain, the variation in individual’s perception of pain relating to the same tissue damage and pain without injury – indicate the pain process to be more complex than the linear-biomedical model, and that pain does not simply equate to injury. In response to this, the Gate Control Theory (GTC) was developed.

The Gate Control Theory (GTC) is probably the most influential theory of pain to date. This theory is said to have had a particularly important contribution to the understanding of pain due to the emphasis it places on the central neural mechanisms (Melzack 1999) and the appreciation that pain can be influenced by both a range of factors and not just those physiological ones related to the wound. Indeed, the gate-control theory was developed in order to account for the importance of both the mind and brain in the perception of pain (Melzack and Wall 1965). This particular theory, although accounting for primarily mental phenomena, considers the physiological basis in order to explain the complex phenomenon of pain. Thus, it established the brain as an active system that filters, selects and modulates inputs (Melzack 1999). Specifically, it investigates the structure of the nervous system suggesting that the experience of pain is dependent on a complex interplay of these two systems; central nervous system and the peripheral nervous system.

Briefly, according to the GTC, when an injury occurs, pain messages originate within the nerves in the affected tissue and travel along the peripheral nerves to the spinal cord and then on up to the brain (see Fig. 2.1). However, before reaching the brain, the pain messages encounter a ‘gate keeper’ (a group of nerve cells known as the substantia gelatinosa situated within the spinal cord), which determines whether the pain signals proceed on to the brain or are blocked. This gate plays an important role in the pain management of the central nervous system. The substantia gelatinosa modulates sensory input through balancing the activity of small-diameter (A–Delta and C) and large-diameter (A–beta) fibres (Melzack 1996). Whilst large fibre activity (non-nociceptive) results in the closure of the spinal gating mechanism and prevention of synaptic transmission to centrally projecting T cells (transport cells), activation of small fibres (nociceptive) open the gate and facilitate T cell activity (See Fig. 2.2). This activity is said to be responsible for the experience of pain (Weisenberg 1977).

Simply put, the GTC suggests that the pain messages on route to the brain are subject to a gate. If the gate is closed then less pain messages get through and, hence, less pain is experienced. In contrast, if the gate is open then potentially more pain is experienced. Both physiological (e.g. rubbing the wounded area) or psychological (e.g. stress or anxiety) can influence whether the gate is open or closed.

Within this theory, the experience of pain is seen as an on-going sequence of activities which is both reflexive and modifiable. The process described above results in overt communication and expressions of pain by the patients and the strategies they may adopt in order to control the painful experience. Furthermore, this theory allows for the management and shaping of painful experiences due to the multi-faceted nature of it (Novy et al. 1995). For example, in addition to the physiological aspects, it accounts for affective, behavioural, cognitive and sensory factors. Building upon the theory, Melzack (1993) argued that there was an interrelation of physiological and psychological facets, with affective, behavioural, cognitive and sensory-physical factors each being part of an integrated chronic pain system.

Although this theory has been subject to specific criticisms, particularly in relation to points of particular anatomical mechanisms, and suitably revised, it has been of enormous value in pushing forward and stimulating research surrounding the science of pain and the development of new clinical treatments (Melzack and Wall 1982). Furthermore, the model has led to the development of various pain management techniques, including that of neurophysiological procedures, behavioural treatments, pharmacological advance, and techniques targeted towards the alteration of attentional and perceptual pain associated processes (Novy et al. 1995).

As discussed, pain is not a physiological symptom, but rather, a biopsychosocial phenomenon (Adams et al. 2006; Upton and Solowiej 2010). Pain, and its experience, is a complex and multi-faceted phenomenon, being subjective and often difficult to describe. In addition to the pathophysiological causes of wound pain, the patient’s psychological state of mind, environment and cultural background can each impact on the way in which the patient perceives it (Briggs et al. 2002; Soon and Acton 2006; see Table 2.2). Indeed, there are whole ranges of factors that can influence whether the gate is open or closed, for example: