Pain is a complex phenomenon that has physiological (biological), psychological and social factors that influence the individual patient's experience. It is subjective, so it is important to understand the patient's perspective. It has both physical and affective (emotional) components. Pain is an emotion experienced in the brain; it is not like touch, taste, sight, smell or hearing. It is categorized into acute pain (less than 12 weeks’ duration) and chronic pain (more than 12 weeks’ duration). Pain can be perceived as a warning of potential damage, but it can also be present when no actual harm is being done to the body (British Pain Society [29]).

To reflect this, the International Association for the Study of Pain (IASP [84]) published the following definition of pain: ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’. As pain is subjective, another favoured definition for use in clinical practice, proposed originally by McCaffery ([106], p.95), is: ‘Pain is whatever the experiencing person says it is, existing whenever the experiencing person says it does.’

In each individual, the ‘pain experience’ will be a result of the interaction of biological, psychological, environmental and social factors. Nurses are therefore encouraged to adopt an integrated, multidisciplinary approach to management that also considers patients’ preferences and prior experience (Schug et al. [166]).