Pain: The Nature and Experience of Pain

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By Persis Mary Hamilton, RN, CNS, MS, EdD

LEARNING OBJECTIVES

Upon completion of this course, you will be able to:

• Explain the nature of pain and its definitions, characteristics, types, and sources.
• Identify current standards identified for the management of pain.

Pain is a universal human experience and the most common reason people seek medical care. Pain tells us something is wrong in the structure or function of our body and that we need to do something about it. Because pain is such a strong motivator for action, it is considered one of the body’s most important protective mechanisms.

DEFINITIONS OF PAIN

The International Association for the Study of Pain defined pain as “an unpleasant, subjective, sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage” (International Association for the Study of Pain, 1979). Pain, however, is much more than a physical sensation caused by a single entity. It is subjective and highly individual, a complex mechanism with physical, emotional, and cognitive components.

Pain cannot be objectively measured in the same way as, for example, the chemical content of urine or the oxygen content level of blood. Only the person who is suffering knows how the experience feels. For these reasons, McCaffery defined pain as “whatever the experiencing person says it is and whenever he says it does” (1979). The American Pain Society goes further by stating that it is “not the responsibility of clients to prove they are in pain; it is the [caregiver’s] responsibility to accept the client’s report of pain” (2005).

Pain alters the quality of life more than any other health-related problem. It interferes with sleep, mobility, nutrition, thought, sexual activity, emotional well-being, creativity, and self-actualization. Surprisingly, even though pain is such an important obstacle to comfort, it is one of the least understood, most under-treated, and oft-discounted problems of healthcare providers and their clients. For this reason, some caregivers add comfort to Maslow’s hierarchy of basic human needs (1968). The American Pain Society goes further, declaring the relief of pain a “basic human right” (2005).

Traditionally, pain was considered merely a physical symptom of illness or injury, a simple stimulus-response mechanism. Though the historic role of nurses has been to relieve pain and suffering, there has been little understanding of the complexity of pain and only limited ways to manage it. Recent research shows pain to be a distinct disorder, with physical, emotional, and cognitive components. This view of pain has broadened our understanding of pain and given us new ways to understand its characteristics.

Types of Pain

Pain is classified as acute and chronic. Acute pain has an identifiable cause and occurs soon after an injury to tissues in the body, such as bone, skin, or muscle. Acute pain is protective in that it motivates a person to take action. Its onset may be sudden or slow, and its intensity may vary from mild to severe. Acute pain is temporary and subsides as healing takes place. Severe acute pain activates the sympathetic nervous system, causing diaphoresis, increased respiratory and pulse rates, and elevated blood pressure.

Chronic pain lasts beyond an expected healing phase, is non-protective in that it serves no function, and may not have an identifiable cause (Patterson, 2007). When pain goes on more than 6 months, it moves from being a “symptom” to a “condition.” Chronic pain afflicts more than 1 in 5 Americans and is one of the most pervasive and thorny medical conditions in the United States. Such pain is described as nonmalignant (noncancerous), malignant (cancerous), and intractable.

• Nonmalignant, noncancerous chronic pain typically accompanies such conditions as osteoarthritis and peripheral neuropathy. The lack of purpose and uncertainty of duration of such pain may lead to depression, fatigue, insomnia, anorexia, apathy, learned helplessness, and other psychosocial consequences. If it is severe, chronic pain—like prolonged stress—activates the parasympathetic nervous system, resulting in muscle tension, decreased heart rate and blood pressure, and failure of body defenses.
• Malignant, cancerous chronic pain may be due to tumor progression, invasive procedures, infection, toxicities of treatment, and physical limitations. Such pain may be felt at the tumor site or some distance from it. Since clients with cancer may experience both chronic and acute pain, caregivers need to investigate immediately any new pain in these clients.
• Intractable chronic pain is pain from any cause that is resistant to medical, surgical, and nursing measures. Persistent and ongoing, intractable chronic pain may be psychogenic in nature (Mosby’s Dictionary, 2009).

Sources of Pain

The sources of pain are divided into three main categories: nociceptor, non-nociceptor, and psychogenic.

Nociceptor pain results when tissue damage produces a pain-producing stimulus that sends an electrical impulse across a pain receptor (nociceptor) by way of a nerve fiber to the central nervous system. Nociceptor pain is further divided into visceral and somatic pain.

• Visceral pain results from stimulation of nociceptors in the abdominal cavity and thorax.
• Somatic pain is divided into deep somatic and cutaneous pain. Deep somatic pain arises from bones, tendons, nerves, and blood vessels. Cutaneous pain originates in the skin or subcutaneous tissue. Some body tissues, such as the brain and lung, have no nociceptors, and some tissues have many.

Non-nociceptor (neuropathic) pain is caused by direct injury to structures of the nervous system.

Psychogenic pain is pain for which there is little or no physical evidence of organic disease or identified injury to tissues in the body. Lack of evidence, however, does not mean clients are malingering or that they are not suffering.

PHYSIOLOGIC SOURCES OF PAIN

Source: Adapted with permission from Ignatavicius et al., 1999.
Nociceptor: Visceral
Physiologic structures	Organs and linings of body cavities
Mechanism	Activation of nociceptors
Characteristics	Poorly localized, diffuse, deep, cramping or splitting
Sources of acute pain	Chest tubes, abdominal drains, bladder and intestinal distention
Sources of chronic pain syndromes	Pancreatitis, liver metastases, colitis
Nociceptor: Somatic
Physiologic structures	Cutaneous: skin and sub-cutaneous tissues Deep somatic: blood, muscle, blood vessels, connective tissue
Mechanism	Activation of nociceptors
Characteristics	Well-localized, constant and achy
Sources of acute pain	Incisional pain, insertion sites of tubes and drains, wound complications, orthopedic procedures, skeletal muscle spasms
Sources of chronic pain syndromes	Bony metastases, osteoarthritis, rheumatoid arthritis, low-back pain, peripheral vascular disease
Non-nociceptor (neuropathic)
Physiologic structures	Nerve fibers, spinal cord, and central nervous system
Mechanism	Non-nociceptive injury to nervous system structures
Characteristics	Generalized along distribution of damaged nervous structures
Sources of acute pain	Poorly localized: shooting, burning, fiery, shock-like, sharp, painful numbness
Sources of chronic pain syndromes	Nervous tissue injury due to diabetes, HIV, chemotherapy, neuropathies, postherpetic neuralgia, trauma, surgery
Psychogenic
Physiologic structures	No organic structures
Mechanism	Emotional
Characteristics	Variable, often numerous
Sources of acute pain	Nonorganic
Sources of chronic pain syndromes	Nonorganic psychological factors

PHYSIOLOGY OF PAIN

Though a person is not consciously aware of the process, the experience of pain involves a complex sequence of biochemical and electrical events or processes beginning with tissue damage and followed by transduction, transmission, perception, and modulation.

Tissue Damage

When tissue is damaged, there is an immediate release of inflammatory chemicals called excitatory neurotransmitters, such as histamine and bradykinin, a powerful vasodilator. Increased blood in the area causes the injured area to swell, redden, and become tender. The bradykinin stimulates the release of prostaglandins and substance P, a potent neurotransmitter that enhances the movement of impulses across nerve synapses.

Transduction and Transmission

Transduction occurs as the energy of the stimulus is converted to electrical energy. Transmission of the stimulus takes place when this energy crosses into a nociceptor at the end of an afferent nerve fiber. Two types of peripheral nerve fibers conduct painful stimuli: the fast, myelinated A-delta fibers and the very small, slow, unmyelinated C-fibers. A-fibers send sharp, distinct sensations that localize the source of the pain and detect its intensity. C-fibers relay impulses that are poorly localized, burning, and persistent. For example, after burning a finger, a person initially feels a sharp localized pain as a result of A-fiber transmission. Within a few seconds the pain becomes more diffuse and widespread as a result of C-fiber transmission.

Pain stimuli travel quickly to the substantia gelatinosa in the dorsal horn of the spinal cord, where the “gating” mechanism (discussed below) occurs. Pain impulses then cross over to the opposite side of the spinal cord and ascend to the higher centers in the brain via the spinothalamic tracts and on to the thalamus and higher centers of the brain, including the reticular formation, limbic system, and somatosensory cortex.

Neurologic transmission of pain stimuli. (Illustration by Jason McAlexander. © 2005, Wild Iris Medical Education, Inc.)

Perception

When pain stimuli reach the cerebral cortex, the brain interprets the signal; processes information from experiences, knowledge, and cultural associations; and perceives pain. Thus, perception is the awareness of pain. The somatosensory cortex identifies the location and intensity of pain, and the associated cortex determines how an individual interprets its meaning.

Modulation

Once the brain perceives the pain, the body releases neuromodulators, such as endogenous opioids (endorphins and enkephalins), serotonin, norepinephrine, and gamma aminobutyric acid. These chemicals hinder the transmission of pain and help produce an analgesic, pain-relieving effect. This inhibition of the pain impulse is called modulation. The descending paths of the efferent fibers extend from the cortex down to the spinal cord and may influence pain impulses at the level of the spinal cord.

Gate-Control Theory

Melzack and Wall proposed the gate-control theory to explain the relationship between pain and the emotions (1982). According to the theory, a gating mechanism occurs when a pain impulse travels to the substantia gelatinosa in the dorsal horn of the spinal cord. There, trigger (T) cells influence the transmission of pain impulses. When their activity is inhibited, the gate closes and impulses are less likely to be transmitted to the brain. This mechanism is controlled by descending nerve fibers from the thalamus and cerebral cortex, areas of the brain that regulate thought and emotions. The gate-control theory helps explain how thoughts and emotions modify the perception of pain and why interventions, such as imagery and distraction, help relieve it.

FACTORS THAT INFLUENCE PAIN

The perception of pain is influenced by physiologic, psychological, and cultural factors, all of which caregivers need to consider.

Physiological Factors

AGE

Age affects the way people respond to pain. It influences both the development and decline of the nervous system. Aging affects the whole body, causing many painful degenerative disorders (such as osteoarthritis), secondary injuries (such as skin abrasions and fractures), and a host of common surgical procedures (such as cataract and hip replacement). Age also affects the way families and caregivers respond to complaints of pain. The following table gives a brief overview of the perception of pain relative to age.

AGE AND THE PERCEPTION OF PAIN

Age	Pain Perception
Pre-term infants	Have anatomical and functional ability to process pain by mid to late gestation; seem to have greater sensitivity to pain than term infants or children
Newborn infants	Response to pain is inborn and does not require prior learning; respond to pain with behaviors such as crying, grimacing, moving body
Infants, 1 month	Can metabolize analgesics and anesthesia effectively; can recognize caregiver as comforter
Toddlers/Preschoolers	Can describe pain, its location and intensity; respond to pain by crying, anger, sadness; may consider pain a punishment; may hold someone accountable for pain and remember experiences in a certain location, such as a clinic
School-age children	May try to be brave when facing a painful procedure; may regress to an earlier stage of development; seek understanding of reasons for pain
Adolescents	May be slow to acknowledge pain; may consider showing signs of pain a weakness; may regress to earlier stages of development with persistent pain
Adults	Fear of pain may prevent some from seeking care; may believe admission of pain is a weakness and inappropriate for age or sex; may consider pain a punishment for moral failure
Older adults	May have decreased sensations or perceptions of pain; may consider pain an inevitable part of aging; chronic pain may produce anorexia, lethargy, depression; may not report pain due to fear of expense, possible treatment, dependency; often describe pain in nonmedical terms such as “hurt” or “ache”; may fear addiction to analgesics; may not want to bother the caregiver or be a “bad patient”

FATIGUE

Fatigue decreases coping abilities and heightens the perception of pain. When people are exhausted from physical activity, stress, and lack of sleep, their perception of pain may be heightened and their coping skills diminished. Thus, sleep and rest from physical, emotional, and social demands are important measures to manage pain more effectively.

GENETIC MAKEUP

Recent research suggests that sensitivity to and tolerance for pain may a genetically linked trait (Ruda et al., 2000). This finding does not negate the need to manage pain adequately, regardless of inherited traits.

MEMORY

Memory of painful experiences, especially experiences that occurred as a very young child, may increase sensitivity and decrease tolerance to pain. For example, even young children remember the pain of an immunization at the doctor’s office and henceforth may be afraid to visit the doctor again.

STRESS RESPONSE

Research has shown that “severe, unrelieved pain can cause an overwhelming stress response in both pre-term and full-term infants which can lead to serious complications and even death” (Pasero, 2004). In recent years, post-traumatic stress syndrome has been the subject of extensive research, both as to its cause and its treatment (Hamilton, 2008).

HEALING

Recent research suggests that unrelieved acute pain slows postoperative wound healing (McGuire, 2006). This evidence is not surprising, given our increasing knowledge of the effect of stress on the human body.

NEUROLOGIC FUNCTION

Any factor that interrupts or interferes with normal pain transmission affects the awareness and response of clients to pain and places them at risk for injury. Analgesics, sedatives, and alcohol depress the functioning of the central nervous system. Some diseases, such as leprosy, damage peripheral nerves, decrease sensitivity to touch and pain, and render sufferers more vulnerable to injury.

Psychological Factors

FEAR AND ANXIETY

The relationship between pain and fear is convoluted and complex. Fear tends to increase the perception of pain, and pain increases feelings of fear and anxiety. This connection occurs in the brain because painful stimuli activate portions of the limbic system believed to control emotional reactions. People who are seriously injured or critically ill often experience both pain and heightened levels of anxiety due to their feelings of helplessness and lack of control. Caregivers need to address both pain and anxiety and use all appropriate measures to relieve suffering.

COPING

People manage pain and other stressors of life in different ways. Some see themselves as self-sufficient, internally controlled, and independent. As a result, they may deny pain or be slow to admit they are suffering. Others see themselves as insufficient, externally controlled, and dependent on others to treat their pain. Self-sufficient, internally controlled people may do better with patient-controlled analgesia (PCA), whereas dependent, externally controlled individuals may prefer nurse-administered analgesia. No matter what the coping style, it is the responsibility of caregivers to relieve pain.

Cultural Factors

Cultural beliefs and values affect the way people respond to pain. As children they learn what is and what is not acceptable behavior when experiencing pain. In some cultures, any expression of pain is considered cowardly and shameful. In others, noisy demonstrations of pain are expected and acceptable. The meaning of pain itself may be markedly different in different cultures. Some ethnic groups see pain as a punishment for wrongdoing. Others see pain as a test of faith. And still others view pain as a challenge to be overcome. Recent immigrants to America are more likely to view pain from their cultural roots. Regardless of an individual’s language, religion, or situation, caregivers respect every person and strive to alleviate pain and suffering.

STANDARDS AND GUIDELINES FOR PAIN MANAGEMENT

Because pain management is so important to the provision of quality healthcare, many organizations have developed standards by which professional practice is measured. Two such organizations are the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) and American Academy of Pediatrics (AAP).

Joint Commission

The Joint Commission is an independent organization that accredits and certifies more than 17,000 healthcare organizations and programs in the United States. It evaluates how well these healthcare providers meet published standards of care, including their management of pain. The federal government accepts Joint Commission–accredited facilities as qualified to participate in Medicare and Medicaid reimbursement programs.

Regarding pain management, the Joint Commission Resources states:

Each and every patient has a right to the assessment and management of pain. Hospitals must develop policies and procedures which address the organization’s expectations of pain management in support of their mission and philosophy of care. Patients and their families also need education regarding their role in pain management. Developing a comprehensive and coordinated pain management program can be made easier by accessing good practices. From policies and procedures for the different types of pain (acute, chronic, etc.) to training assistants (including pre- and post-tests) to assessment tools, good practices can assist your organization to provide a comprehensive approach to pain management that meets the intent of the standards and, at the same time, achieves positive outcomes for patient (Joint Commission Resources, Inc., 2009).

The JCAHO Standards of Pain Management are listed below.

American Academy of Pediatrics

The American Academy of Pediatrics is a professional organization dedicated to the health, safety, and well-being of infants, children, adolescents, and young adults. As such, its committees develop guidelines, positions, and programs to support the mission of the organization. The AAP guidelines for pain management conclude with the strategies listed below.

CONCLUSION

Pain is a universal human experience, the strongest motivator for an individual to seek medical care, and one of the body’s most important protective mechanisms. Pain alters the quality of life more than any other health-related problem, interfering with sleep, mobility, thought, emotional well-being, sexual activity, and creativity. Yet, pain is one of the least understood, most under-treated, and often discounted problems faced by healthcare providers. For these reasons, it behooves all caregivers to manage pain more consistently and effectively and to support research to improve pain management for everyone.

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