The International Association for the Study of Pain (IASP) (2011) and the American Pain Society (APS) (2008) define pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” This definition describes pain as a complex phenomenon with multiple components that impacts a person’s psychosocial and physical functioning (McCaffery, Herr, & Pasero, 2011). The accepted clinical definition of pain, which was proposed by Margo McCaffery in 1968 and is now accepted worldwide, reinforces that pain is a highly personal and subjective experience: “Pain is whatever the experiencing person says it is, existing whenever he says it does” (McCaffery, 1968).