The International Association for the Study of Pain (IASP) defined pain as "an unpleasant sensory and emotional experience, which we primarily associate with tissue damage or describe in terms of such damage" (IASP, 2017). The definition of pain often emphasized in nursing is the one by Margo McCaffrey from 1968: "Pain is whatever the experiencing person says it is, existing whenever he says it does" (Pasero, 2018, front piece). It is important to remember this definition when assessing and treating pain.
The undertreatment of pain became a serious issue in the late 1990s. The Joint Commission designated "pain" as the "fifth vital sign" in 2001, but by 2004, this designation no longer appeared in the Standards for Accreditation (Baker, 2017; see Joint Commission, 2019, for Joint Commission Pain Standards) due to the opioid crisis.
The overtreatment of pain-resulting in overdoses of prescription pain relievers, heroin, and other opioids such as fentanyl-has been called the opioid crisis. The National Institute on Drug Abuse (2019) reported in 2018 a daily U.S. death rate of 128 persons due to opioid overdoses and a tremendous financial yearly burden from health care costs, lost productivity, treatment of addictions, and criminal justice expenses. This opioid crisis complicates pain assessment and treatment. Health care workers must collaborate to effectively assess and treat pain.
The pathophysiologic phenomena of pain are associated with the central and the peripheral nervous systems. The source of pain stimulates the peripheral nerve endings (nociceptors), which transmit the sensations to the central nervous system. They are sensory receptors that detect signals from damaged tissue and to chemicals released from the damaged tissue. Nociceptors are sensitive to intense mechanical stimulation, temperature, or noxious stimuli (chemical, thermal, or mechanical). Nociceptors are distributed in the body, in the skin, subcutaneous tissue, skeletal muscle, joints, peritoneal surfaces, pleural membranes, dura mater, and blood vessel walls. Note that they are not located in the parenchyma of visceral organs. Physiologic processes involved in pain perception (or nociception) include transduction, transmission, perception, and modulation (see Fig. 7-1). These processes serve as means for the stimuli to be sent to various parts of the spinal cord and to the brain, where they are perceived and can be responded to. The modulation process, which changes or inhibits transmission, is poorly understood but affects the level of pain perceived.
Pain elicits a stress response in the human body, triggering the sympathetic nervous system, resulting in physiologic responses such as the following:
Anxiety, fear, hopelessness, sleeplessness, and thoughts of suicide
Focus on pain, reports of pain, cries and moans, and frowns and facial grimaces
Decrease in cognitive function, mental confusion, altered temperament, high somatization, and dilated pupils
Increased heart rate and peripheral, systemic, and coronary vascular resistance
Increased respiratory rate and sputum retention, resulting in infection and atelectasis
Decreased urinary output, resulting in urinary retention, fluid overload, and depression of all immune responses
Increased antidiuretic hormone, epinephrine, norepinephrine, aldosterone, and glucagon; decreased insulin and testosterone
Hyperglycemia, glucose intolerance, insulin resistance, and protein catabolism
Muscle spasm, resulting in impaired muscle function and immobility and perspiration
Pain has many different classifications. Common categories of pain include the following:
Acute pain: usually associated with an injury with a recent onset and duration of less than 6 months and usually lasts less than a month
Chronic nonmalignant pain: usually associated with a specific cause or injury and is described as a constant pain that persists for more than 6 months
Cancer pain: often due to the compression of peripheral nerves or meninges or from the damage to these structures following surgery, chemotherapy, radiation, or tumor growth and infiltration
Pain is also described as transient pain, tissue injury pain (surgical pain, trauma-related pain, burn pain, or iatrogenic pain as a result of an intervention), and chronic neuropathic pain.
Pain is also viewed in terms of its location, as follows:
Pain location can also be described as to whether or not it is perceived at the site of the pain stimuli, as follows:
Radiating (perceived both at the source and extending to other tissues)
Referred (perceived in body areas away from the pain source; see Fig. 7-2)
Phantom pain (perceived in nerves left by a missing, amputated, or paralyzed body part)
Other descriptions of pain include the following:
Neuropathic pain causes an abnormal processing of pain messages and results from past damage to peripheral or central nerves due to sustained neurochemical levels
Intractable pain is defined by its high resistance to pain relief
There are many aspects that influence the way pain is manifested. The physiologic aspects of pain result from a client’s physical response to a painful stimulus. For example, a client feels a pin pricking the skin of a finger through the nervous system; the sensation is interpreted by the brain, and the person pulls their hand away from the painful stimulus. Although they are physiologic in nature, the level of severity, the quality of the perceived pain, and the location where the pain is perceived to be are described as sensory aspects of the pain. For example, although a pin prick is usually felt at the site of the prick, other pain, such as severe chest pain felt in the back rather than in the chest, can be felt in a location other than the location of the actual pain stimulus; this is called referred pain. The quality of the perceived pain may vary and be felt, for example, as superficial or deep, shooting, sharp, electric, itchy, tingling, achy, cramping, or throbbing. When pain is perceived, the person responds with behaviors, both verbal and nonverbal. For example, for a pin prick, the person might say "ouch" and pull the hand away. Another aspect of pain relates to the cultural and social contexts of the client, which can affect the person’s beliefs about the pain, its cause, and its purpose. For example, in some cultures, childbirth is expected to produce almost unbearable pain, and the woman in labor sobs and thrashes about and seems unable to help the nurse through the labor. Finally, the client’s spiritual beliefs can affect their perceived pain sensations and responses. For example, persons who believe physical suffering to be offered up to God will expect pain and respond with resignation to it, not attempting to relieve it as much as someone would if not sharing a similar belief.