9
Pain
Jessica I. Goldberg and William E. Rosa
http://evolve.elsevier.com/Lewis/medsurg/
CONCEPTUAL FOCUS
Coping Pain
Functional Ability
LEARNING OUTCOMES
1. Define pain. 6. Describe effective interprofessional pain management
2. Describe the neural mechanisms of pain and pain techniques.
modulation. 7. Describe drug and nondrug methods of pain relief.
3. Distinguish between nociceptive and neuropathic types of 8. Explain your role and responsibility in pain management.
pain. 9. Discuss ethical and legal issues related to pain and pain
4. Explain the physical and psychologic effects of unrelieved management.
pain. 10. Evaluate the influence of one’s own knowledge, beliefs, and
5. Interpret data from a comprehensive pain assessment. attitudes about pain assessment and management.
KEY TERMS
analgesic ceiling nociceptive pain
breakthrough pain (BTP) pain
central sensitization patient-controlled analgesia (PCA)
complex regional pain syndrome (CRPS) patient-controlled epidural analgesia (PCEA)
equianalgesic dose peripheral sensitization
modulation transduction
multimodal analgesia transmission
neuropathic pain trigger point
nociception
Pain is a complex, multidimensional experience that is closely Common chronic pain conditions, such as arthritis, migraine
related to suffering and decreased quality of life. Pain is a major headache, and back pain, affect more than 1 million American
reason that people seek health care. To effectively assess and man- adults. Pain is a common symptom experienced by patients
age patients with pain, you need to understand the physiologic with cancer.1 Despite the high prevalence of acute and chronic
and psychosocial dimensions of pain. Pain is interrelated with pain, many people experience inadequate pain management.
many concepts. Culture and spirituality influence the expression Consequences of unrelieved acute pain are shown in Table 9.1.
of pain. Acute pain adversely affects mobility and sleep, leading
to fatigue. Having pain is a stressor that can lead to depression.
Those with severe or chronic pain are more likely to describe their
DEFINITIONS AND DIMENSIONS OF PAIN
health as poor and may have increased mortality. This chapter The International Association for the Study of Pain (IASP)
presents information to help you assess and safely manage pain in defines pain as “an unpleasant sensory and emotional experi-
collaboration with other interprofessional team members. ence associated with actual or potential tissue damage.” This
definition emphasizes the subjective nature of pain, in which
the patient’s self-report is the most valid means of assessment.
EXTENT OF PAIN PROBLEM Although understanding the patient’s experience and relying
Millions of people suffer from pain. Each year in the US, at least on self-report is essential, this view is problematic for many
25 million people have acute pain from an injury or surgery. patients. For example, patients who are comatose or who have
119
,120 SECTION 2 Problems Related to Comfort and Coping
TABLE 9.1 Negative Consequences of TABLE 9.2 Dimensions of Pain
Unrelieved Acute Pain Dimension Description
Response Possible Consequences Affective • Emotional responses to pain include anger, fear,
Cardiovascular depression, anxiety
↑
Cardiac output Deep vein thrombosis • Negative emotions impair patient’s quality of life
↑
Coagulation Hypertension Behavior • Observable actions (e.g., grimacing, irritability,
↑
Heart rate Myocardial infarction coping skills) are used to express or control pain
↑
Myocardial O2 consumption Unstable angina • People unable to communicate may have behavior
↑
Peripheral vascular resistance changes (e.g., agitation, combativeness)
Cognitive • Beliefs, attitudes, memories, and meaning
Endocrine and Metabolic attributed to pain influence the ways in which a
↑
Adrenocorticotropic hormone ↑ BP person responds to pain
(ACTH) Fluid overload Physiologic • Genetic, anatomic, and physical determinants of
↑
Aldosterone ↑ Heart rate pain influence how we process, recognize, and
↑
Antidiuretic hormone (ADH) Hyperglycemia describe painful stimuli
↑
Cortisol ↑ Respiratory rate Sociocultural • Age and gender influence nociceptive processes
↑
Epinephrine and norepinephrine Shock and responses to opioids
Gluconeogenesis Urinary retention, ↓ urine output • Families and caregivers influence patient’s
Glycogenolysis Weight loss (from ↑ catabolism) response to pain through their beliefs, behaviors,
↓
Insulin and support
Muscle protein catabolism • Culture affects pain expression, medication use,
pain-related beliefs, and coping methods
Gastrointestinal
↓
Gastric and intestinal motility Anorexia
Constipation
pain (Table 9.2). Each person understands and conceptualizes
Obstruction
Paralytic ileus their pain in their own way. For example, a woman in labor
will have pain. She may choose to manage it without analgesics
Immunologic because she associates it with a joyful event. She may feel control
↓
Immune response Infection over her pain because of the training she received in prenatal
classes and the knowledge that the pain is time limited. In con-
Musculoskeletal
trast, a woman with chronic, undefined musculoskeletal pain
Impaired muscle function Immobility
Muscle spasm Weakness and fatigue
may be stressed by thoughts that others think that her pain is
“not real,” is uncontrollable, or is caused by her own actions.
Neurologic Perceptions influence the ways in which a person responds to
Impaired cognitive function Confusion pain. We must consider perceptions in a comprehensive treat-
Impaired ability to think, reason, make ment plan.
decisions Some people cope with pain by distracting themselves.
Others convince themselves that the pain is permanent and
Renal and Urologic
↓
Urine output Electrolyte imbalance untreatable. People who believe their pain is uncontrollable and
Urinary retention Fluid imbalance overwhelming are more likely to have poor outcomes.
Families and caregivers influence the patient’s response to
Respiratory pain through their beliefs and behaviors. For example, families
↓
Cough with sputum retention Atelectasis may discourage the patient from taking opioids because they
Hypoxemia Pneumonia fear that the patient may become addicted. Understanding
↓
Tidal volume these beliefs helps you address them through patient and family
teaching.
dementia, who are mentally disabled or challenged, or have Pain Mechanisms
expressive aphasia have varying abilities to report pain. In these Nociception is the physiologic process by which we commu-
instances, you must include nonverbal information, such as nicate information about tissue damage to the central nervous
observed behaviors, in your pain assessment. system (CNS). It involves 4 processes: (1) transduction, (2)
The emotional distress of pain can cause suffering, especially transmission, (3) perception, and (4) modulation (Fig. 9.1).
when the pain is unrecognized or undertreated.2 Suffering can
result in a sense of insecurity, lack of control, and spiritual dis- Transduction
tress. It is important to assess the ways in which a person’s spir- Transduction involves the conversion of a noxious (tissue-dam-
ituality influences and is influenced by pain. aging) stimulus into an electrical signal called an action poten-
The biopsychosocial model of pain includes the physiologic, tial. Noxious stimuli can be thermal (e.g., sunburn), mechanical
affective, cognitive, behavior, and sociocultural dimensions of (e.g., surgical incision), or chemical (e.g., toxic substances).
, CHAPTER 9 Pain 121
1
Transduction
1. Noxious stimuli cause cell damage with
the release of sensitizing chemicals
• Prostaglandins
• Bradykinin
• Serotonin
• Substance P
• Histamine 3 3
Perception
2. These substances activate nociceptors Conscious experience of pain
and lead to generation of action potential
Mod
ulatio
1 Site of pain
n
2
4
Transmission
2
2 4
Transmission Modulation
Action potential continues from • Neurons originating in the brainstem
• Site of injury to spinal cord descend to the spinal cord and release
• Spinal cord to brainstem and thalamus substances (e.g., endogenous opioids)
• Thalamus to cortex for processing that inhibit nociceptive impulses
Fig. 9.1 Nociceptive pain originates when tissue is injured. (1) Transduction occurs when there is release of
chemical mediators. (2) Transmission involves the conduct of the action potential from the periphery (injury
site) to the spinal cord and then to the brainstem, thalamus, and cerebral cortex. (3) Perception is the con-
scious awareness of pain. (4) Modulation involves signals from the brain going back down the spinal cord to
modify incoming impulses. (Developed by McCaffery M, Pasero C, Paice JA. Modified from McCaffery M,
Pasero C: Pain: clinical manual, ed 2, St Louis, 1999, Mosby.)
They cause the release of chemicals, such as substance P and antiinflammatory drugs (NSAIDs), such as ibuprofen, exert
adenosine triphosphate (ATP), into the damaged tissues. Other their analgesic effects by blocking the action of COX-2 enzymes.
chemicals are released by mast cells (e.g., serotonin, histamine,
prostaglandins) and macrophages (e.g., cytokines). These Transmission
chemicals activate nociceptors (specialized receptors), or free Transmission is the process by which we relay pain signals from
nerve endings, which respond to painful stimuli. Activating the periphery to the spinal cord and then to the brain. Nerves
the nociceptors results in an action potential. It is carried from that carry pain impulses from the periphery to the spinal cord
the nociceptors to the spinal cord by small, rapidly conducting, are called primary afferent fibers. These include A-delta and C
myelinated A-delta fibers and slowly conducting unmyelinated fibers. Each is responsible for a different pain sensation. A-delta
C fibers. fibers conduct pain rapidly. They are responsible for the initial,
Besides stimulating nociceptors, inflammation and the sharp pain that accompanies tissue injury. C fibers transmit
subsequent release of chemical mediators lower nociceptor painful stimuli more slowly. They produce pain that is typically
thresholds. As a result, nociceptors may fire in response to stim- aching or throbbing. Primary afferent fibers end in the dorsal
uli that previously were insufficient to elicit a response. They horn of the spinal cord. Activity in the dorsal horn integrates
may also fire in response to nonnoxious stimuli, such as light and modulates pain inputs from the periphery.
touch. We call this increased susceptibility to nociceptor acti- Fig. 9.1 shows the movement of pain impulses from the site of
vation peripheral sensitization. Leukotrienes, prostaglandins, transduction to the brain. Three segments are involved in noci-
cytokines, and substance P are involved in peripheral sensiti- ceptive signal transmission: (1) transmission along the periph-
zation. Cyclooxygenase (COX), produced in the inflammatory eral nerve fibers to the spinal cord, (2) dorsal horn processing,
response, also plays a key role in peripheral sensitization. A clin- and (3) transmission to the thalamus and cerebral cortex.
ical example of this process is sunburn. Thermal injury causes Drugs that stabilize the neuronal membrane act on periph-
inflammation that results in pain when the affected skin is eral sodium channels to inhibit movement of nerve impulses.
lightly touched. Peripheral sensitization amplifies signal trans- These medications include local anesthetics (e.g., injectable
mission. This contributes to central sensitization (discussed or topical lidocaine, bupivacaine) and antiseizure drugs (e.g.,
under Dorsal Horn Processing). The pain from activation of gabapentin).
peripheral nociceptors is called nociceptive pain. Transmission to spinal cord. The first-order neuron extends
Therapies that change either the local environment or sen- the entire distance from the periphery to the dorsal horn with
sitivity of the peripheral nociceptors can prevent transduction no synapses. For example, an afferent fiber travels from the great
and initiation of an action potential. Decreasing the effects toe through the 5th lumbar nerve root into the spinal cord. It is
of chemicals released at the periphery is the basis of several a single cell. Once generated, an action potential travels all the
drug approaches to pain relief. For example, nonsteroidal way to the spinal cord unless it is blocked by a sodium channel
Pain
Jessica I. Goldberg and William E. Rosa
http://evolve.elsevier.com/Lewis/medsurg/
CONCEPTUAL FOCUS
Coping Pain
Functional Ability
LEARNING OUTCOMES
1. Define pain. 6. Describe effective interprofessional pain management
2. Describe the neural mechanisms of pain and pain techniques.
modulation. 7. Describe drug and nondrug methods of pain relief.
3. Distinguish between nociceptive and neuropathic types of 8. Explain your role and responsibility in pain management.
pain. 9. Discuss ethical and legal issues related to pain and pain
4. Explain the physical and psychologic effects of unrelieved management.
pain. 10. Evaluate the influence of one’s own knowledge, beliefs, and
5. Interpret data from a comprehensive pain assessment. attitudes about pain assessment and management.
KEY TERMS
analgesic ceiling nociceptive pain
breakthrough pain (BTP) pain
central sensitization patient-controlled analgesia (PCA)
complex regional pain syndrome (CRPS) patient-controlled epidural analgesia (PCEA)
equianalgesic dose peripheral sensitization
modulation transduction
multimodal analgesia transmission
neuropathic pain trigger point
nociception
Pain is a complex, multidimensional experience that is closely Common chronic pain conditions, such as arthritis, migraine
related to suffering and decreased quality of life. Pain is a major headache, and back pain, affect more than 1 million American
reason that people seek health care. To effectively assess and man- adults. Pain is a common symptom experienced by patients
age patients with pain, you need to understand the physiologic with cancer.1 Despite the high prevalence of acute and chronic
and psychosocial dimensions of pain. Pain is interrelated with pain, many people experience inadequate pain management.
many concepts. Culture and spirituality influence the expression Consequences of unrelieved acute pain are shown in Table 9.1.
of pain. Acute pain adversely affects mobility and sleep, leading
to fatigue. Having pain is a stressor that can lead to depression.
Those with severe or chronic pain are more likely to describe their
DEFINITIONS AND DIMENSIONS OF PAIN
health as poor and may have increased mortality. This chapter The International Association for the Study of Pain (IASP)
presents information to help you assess and safely manage pain in defines pain as “an unpleasant sensory and emotional experi-
collaboration with other interprofessional team members. ence associated with actual or potential tissue damage.” This
definition emphasizes the subjective nature of pain, in which
the patient’s self-report is the most valid means of assessment.
EXTENT OF PAIN PROBLEM Although understanding the patient’s experience and relying
Millions of people suffer from pain. Each year in the US, at least on self-report is essential, this view is problematic for many
25 million people have acute pain from an injury or surgery. patients. For example, patients who are comatose or who have
119
,120 SECTION 2 Problems Related to Comfort and Coping
TABLE 9.1 Negative Consequences of TABLE 9.2 Dimensions of Pain
Unrelieved Acute Pain Dimension Description
Response Possible Consequences Affective • Emotional responses to pain include anger, fear,
Cardiovascular depression, anxiety
↑
Cardiac output Deep vein thrombosis • Negative emotions impair patient’s quality of life
↑
Coagulation Hypertension Behavior • Observable actions (e.g., grimacing, irritability,
↑
Heart rate Myocardial infarction coping skills) are used to express or control pain
↑
Myocardial O2 consumption Unstable angina • People unable to communicate may have behavior
↑
Peripheral vascular resistance changes (e.g., agitation, combativeness)
Cognitive • Beliefs, attitudes, memories, and meaning
Endocrine and Metabolic attributed to pain influence the ways in which a
↑
Adrenocorticotropic hormone ↑ BP person responds to pain
(ACTH) Fluid overload Physiologic • Genetic, anatomic, and physical determinants of
↑
Aldosterone ↑ Heart rate pain influence how we process, recognize, and
↑
Antidiuretic hormone (ADH) Hyperglycemia describe painful stimuli
↑
Cortisol ↑ Respiratory rate Sociocultural • Age and gender influence nociceptive processes
↑
Epinephrine and norepinephrine Shock and responses to opioids
Gluconeogenesis Urinary retention, ↓ urine output • Families and caregivers influence patient’s
Glycogenolysis Weight loss (from ↑ catabolism) response to pain through their beliefs, behaviors,
↓
Insulin and support
Muscle protein catabolism • Culture affects pain expression, medication use,
pain-related beliefs, and coping methods
Gastrointestinal
↓
Gastric and intestinal motility Anorexia
Constipation
pain (Table 9.2). Each person understands and conceptualizes
Obstruction
Paralytic ileus their pain in their own way. For example, a woman in labor
will have pain. She may choose to manage it without analgesics
Immunologic because she associates it with a joyful event. She may feel control
↓
Immune response Infection over her pain because of the training she received in prenatal
classes and the knowledge that the pain is time limited. In con-
Musculoskeletal
trast, a woman with chronic, undefined musculoskeletal pain
Impaired muscle function Immobility
Muscle spasm Weakness and fatigue
may be stressed by thoughts that others think that her pain is
“not real,” is uncontrollable, or is caused by her own actions.
Neurologic Perceptions influence the ways in which a person responds to
Impaired cognitive function Confusion pain. We must consider perceptions in a comprehensive treat-
Impaired ability to think, reason, make ment plan.
decisions Some people cope with pain by distracting themselves.
Others convince themselves that the pain is permanent and
Renal and Urologic
↓
Urine output Electrolyte imbalance untreatable. People who believe their pain is uncontrollable and
Urinary retention Fluid imbalance overwhelming are more likely to have poor outcomes.
Families and caregivers influence the patient’s response to
Respiratory pain through their beliefs and behaviors. For example, families
↓
Cough with sputum retention Atelectasis may discourage the patient from taking opioids because they
Hypoxemia Pneumonia fear that the patient may become addicted. Understanding
↓
Tidal volume these beliefs helps you address them through patient and family
teaching.
dementia, who are mentally disabled or challenged, or have Pain Mechanisms
expressive aphasia have varying abilities to report pain. In these Nociception is the physiologic process by which we commu-
instances, you must include nonverbal information, such as nicate information about tissue damage to the central nervous
observed behaviors, in your pain assessment. system (CNS). It involves 4 processes: (1) transduction, (2)
The emotional distress of pain can cause suffering, especially transmission, (3) perception, and (4) modulation (Fig. 9.1).
when the pain is unrecognized or undertreated.2 Suffering can
result in a sense of insecurity, lack of control, and spiritual dis- Transduction
tress. It is important to assess the ways in which a person’s spir- Transduction involves the conversion of a noxious (tissue-dam-
ituality influences and is influenced by pain. aging) stimulus into an electrical signal called an action poten-
The biopsychosocial model of pain includes the physiologic, tial. Noxious stimuli can be thermal (e.g., sunburn), mechanical
affective, cognitive, behavior, and sociocultural dimensions of (e.g., surgical incision), or chemical (e.g., toxic substances).
, CHAPTER 9 Pain 121
1
Transduction
1. Noxious stimuli cause cell damage with
the release of sensitizing chemicals
• Prostaglandins
• Bradykinin
• Serotonin
• Substance P
• Histamine 3 3
Perception
2. These substances activate nociceptors Conscious experience of pain
and lead to generation of action potential
Mod
ulatio
1 Site of pain
n
2
4
Transmission
2
2 4
Transmission Modulation
Action potential continues from • Neurons originating in the brainstem
• Site of injury to spinal cord descend to the spinal cord and release
• Spinal cord to brainstem and thalamus substances (e.g., endogenous opioids)
• Thalamus to cortex for processing that inhibit nociceptive impulses
Fig. 9.1 Nociceptive pain originates when tissue is injured. (1) Transduction occurs when there is release of
chemical mediators. (2) Transmission involves the conduct of the action potential from the periphery (injury
site) to the spinal cord and then to the brainstem, thalamus, and cerebral cortex. (3) Perception is the con-
scious awareness of pain. (4) Modulation involves signals from the brain going back down the spinal cord to
modify incoming impulses. (Developed by McCaffery M, Pasero C, Paice JA. Modified from McCaffery M,
Pasero C: Pain: clinical manual, ed 2, St Louis, 1999, Mosby.)
They cause the release of chemicals, such as substance P and antiinflammatory drugs (NSAIDs), such as ibuprofen, exert
adenosine triphosphate (ATP), into the damaged tissues. Other their analgesic effects by blocking the action of COX-2 enzymes.
chemicals are released by mast cells (e.g., serotonin, histamine,
prostaglandins) and macrophages (e.g., cytokines). These Transmission
chemicals activate nociceptors (specialized receptors), or free Transmission is the process by which we relay pain signals from
nerve endings, which respond to painful stimuli. Activating the periphery to the spinal cord and then to the brain. Nerves
the nociceptors results in an action potential. It is carried from that carry pain impulses from the periphery to the spinal cord
the nociceptors to the spinal cord by small, rapidly conducting, are called primary afferent fibers. These include A-delta and C
myelinated A-delta fibers and slowly conducting unmyelinated fibers. Each is responsible for a different pain sensation. A-delta
C fibers. fibers conduct pain rapidly. They are responsible for the initial,
Besides stimulating nociceptors, inflammation and the sharp pain that accompanies tissue injury. C fibers transmit
subsequent release of chemical mediators lower nociceptor painful stimuli more slowly. They produce pain that is typically
thresholds. As a result, nociceptors may fire in response to stim- aching or throbbing. Primary afferent fibers end in the dorsal
uli that previously were insufficient to elicit a response. They horn of the spinal cord. Activity in the dorsal horn integrates
may also fire in response to nonnoxious stimuli, such as light and modulates pain inputs from the periphery.
touch. We call this increased susceptibility to nociceptor acti- Fig. 9.1 shows the movement of pain impulses from the site of
vation peripheral sensitization. Leukotrienes, prostaglandins, transduction to the brain. Three segments are involved in noci-
cytokines, and substance P are involved in peripheral sensiti- ceptive signal transmission: (1) transmission along the periph-
zation. Cyclooxygenase (COX), produced in the inflammatory eral nerve fibers to the spinal cord, (2) dorsal horn processing,
response, also plays a key role in peripheral sensitization. A clin- and (3) transmission to the thalamus and cerebral cortex.
ical example of this process is sunburn. Thermal injury causes Drugs that stabilize the neuronal membrane act on periph-
inflammation that results in pain when the affected skin is eral sodium channels to inhibit movement of nerve impulses.
lightly touched. Peripheral sensitization amplifies signal trans- These medications include local anesthetics (e.g., injectable
mission. This contributes to central sensitization (discussed or topical lidocaine, bupivacaine) and antiseizure drugs (e.g.,
under Dorsal Horn Processing). The pain from activation of gabapentin).
peripheral nociceptors is called nociceptive pain. Transmission to spinal cord. The first-order neuron extends
Therapies that change either the local environment or sen- the entire distance from the periphery to the dorsal horn with
sitivity of the peripheral nociceptors can prevent transduction no synapses. For example, an afferent fiber travels from the great
and initiation of an action potential. Decreasing the effects toe through the 5th lumbar nerve root into the spinal cord. It is
of chemicals released at the periphery is the basis of several a single cell. Once generated, an action potential travels all the
drug approaches to pain relief. For example, nonsteroidal way to the spinal cord unless it is blocked by a sodium channel
