Understanding Acute and Chronic Pain

Acute and Chronic Pain

• Pain is ubiquitous
• George Clooney managed pain with interventions after a movie injury
• Pain impacts psychological well-being and quality of life
• Pain is a public health concern due to its high prevalence
• Acute pain: associated with recent tissue damage
• Chronic pain: persists beyond the normal healing period (3-6 months)
• Chronic pain prevalence: estimated as high as 30% in the Western world
• In Canada, about 20% of adults experience chronic pain
• In the U.S., about 116 million Americans suffer from chronic pain
• 10% of adults report pain lasting a year or more
• 40% indicate moderate to severe negative impact
• 22% of primary-care patients report pain lasting over six months, requiring medical attention
• 15-30% of children and adolescents suffer from persistent pain
• Cumulative costs in the U.S. due to chronic pain may exceed $600 billion per year
• In Canada costs exceed $37 billion per year, including $6 billion in direct health-care costs
• Annual cost of care per untreated pain patient at Canadian pain clinics is $17,544 (Privately funded)
• Biomedical pain management includes medications, surgery, and physical therapy
• Public awareness of problems related to the abuse of pain medications is considerable

Understanding the Nature of Pain

• Pain is primarily a psychological experience
• International Association for the Study of Pain (IASP) defines pain as: "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage"
• Pain is not merely a sensation, rather a perception incorporating emotional components
• Sensation: stimulation of a sensory receptor giving rise to neural impulses from an experience outside the body
• Experience becomes pain once interpreted in the brain
• Nociception: processing of stimuli associated with the stimulation of nociceptors; potential to be experienced as pain
• Pain: perceptual process associated with selective abstraction, conscious awareness, ascribed meaning, learning, and appraisal
• Motivational and psychological states are of primary importance to conceptualizing pain
• The experience of pain is closely tied to emotions such as anger, sadness, and disgust
• Pain leads to direct behavioral and psychological consequences
• A significant portion of chronic pain sufferers also present with depression
• 5-85% of people with chronic pain suffer from depression, varying by study
• Chronic pain associates with anxiety and substance abuse
• Patients may use alcohol and non-prescribed drugs to palliate pain
• Chronic pain leads to disrupted social relationships, social isolation, and reduced quality of life
• Psychologists play a key role in researching and conceptualizing pain experiences
• Psychologists help in understanding the expression of pain, verbally and non-verbally
• Chronic pain patients benefit when psychologists improves quality of life

Theories of Pain

• Early pain theories emphasize biophysical aspects
• Descartes' conceptualization likens pain to a string on a bell, tissue damage pulls the string and causes the bell to ring
• Specificity theory implied a direct pain and tissue-damage correspondence
• Specificity theory was influential but failed to help patients with chronic pain
• Attempts to new theories lead to accounts of vague pain mechanisms and deemed the brain as merely a pain receiver
• Melzack and Wall developed the gate control theory in 1965 which is the most dominant theory of pain today
• Subsequent work has moved focus to the complex psychological phenomenon of pain
• Key elements of gate control theory:
  • Nerve impulses from nerves modulate at the dorsal horn of the spinal cord
  • The amount of activity in small pain pathway and large-diameter sensory neural pathways
• Large-diameter fibers "close the gate" by inhibiting transmission
• Small fibers "open the gate" by facilitating transmission
• Rubbing a painful area reduces pain by activating large-diameter fibers that inhibit nociceptive transmission
• Small and large-diameter fibers synapse on projection cells, going to the brain via sensory pathways
• Output of spinal transmission cells activates neural areas that underlie complex experiences
• Cortical descending signals inhibit nociceptive message transmission to the brain; closes the "gate."
• This demonstrates the physiological basis for the role of psychological factors in pain
• Importance of cortical function in modulation explains why hypnosis can assist to endure increased pain
• Melzack complemented the gate control theory with the neuromatrix model
• Neuromatrix: emphasizes the role of the brain in pain perception
• Helps explain phantom limb pain
• Body is perceived as a unit (the self), distinct from its surroundings, through a central neural process
• Anatomical process of the body-self: the neuromatrix, a widespread network of neurons
• Neuronal loops separate for parallel processing within the neuromatrix and allow for interactions between the processing outputs
• Neuromatrix is initially genetically determined, then sculpted by sensory inputs for patterns that impress on the neuromatrix
• Nerve impulses reveal a characteristic pattern (neurosignature) that is produced by the synaptic connection arrangement in the neuromatrix
• The neurosignature is the output from the neuromatrix
• Pain perception is generated as output of the neuromatrix
• Influenced by sensory inputs, affective and cognitive functions
• Pain behaviors can be generated or perpetuated by conditioned cues or expectation of pain and suffering
• Phantom limb pain is believed to be related to the activity of the neuromatrix
• Various treatments can affect output, influence, and change inputs the neuromatrix

Biopsychosocial Models of Pain

• Consistent with the gate control theory
• Elaborates social and psychological influences that affect the pain experience
• Focuses on interplay of biological, psychological, and social parameters
• Contrasts against strict biomedical models
• Biomedical models do not account for social and psychological factors or explain various phenomena
• Phenomena not explained: hypnosis effects, coping styles, success of psychological interventions

Influential Biopsychosocial Models & Concepts

• Developed to describe and clarify different aspects of the pain experience Models include:
  • The operant model
  • Fear avoidance model
  • Communications model
  • Cognitive behavioral conceptualizations of chronic pain
• Models recognize importance of biological factors as well as the interaction of biology with psychological like cognition, affect, behaviour
• Models include social factors such as social support and culture

The Operant Model of Pain

• Stresses importance of reinforcement in developing and maintaining pain behavior
• Excessive pain behavior reinforced by attention persists as the attention is reinforcing the idea
• Behaviors such as inactivity that reduce pain may become maladaptive, especially work-related responsibilities
• Pain reports increase relative to verbal reinforcement
• Therapy based on operant principles is effective at least in the short term
• Operant model components are incorporated within cognitive behavioral therapy approaches in clinical practice
• Operant model criticized: fails to account for the interpretations and appraisals of pain

The Fear Avoidance Model of Pain

• This model is based off the concept that movements/behaviors are coupled with pain exacerbations
• Associations + catastrophic thoughts about possibility of re-injury can lead to excessive avoidance
• Excessive avoidance can lead to stiffness and deconditioning, increasing probability of future pain
• Fear avoidance beliefs are predictors of future disability and chronicity
• Fear of pain leading to avoidance can be one of many variables influencing pain & disability

The Communications Model of Pain

• Chain of pain communication seen as three-step process
• Internal experience of pain determined by biological, social/cultural, and psychological factors which are then encoded into behavior (verbal and non-verbal) that can be potentially decoded by observers
• External influences can affect this process at any stage
• The first step includes variety of processes that take place during the experience of pain (affective, cognitive, brain signaling)
• Verbal & non-verbal behaviors vary with automaticity vs. cognitive executive mediation
• Non-verbal pain behaviors are more automatic and under less voluntary control than self-report
• Self-report is under more voluntary control but easier to decode
• observer and characteristics of person expressing pain affects the decoding process
• observer actions can palliate or worsen the pain experience
• Expression is less likely to occur in the presence of a tolerant individual demonstrating tolerance levels
• Children may report more pain when taught pain-promoting interactions
• Pain expression intensity varies with cultural background
• Social stereotypes affect the decoding of pain

Cognitive Behavioural Conceptualization of Pain

• Focuses on cognitive factors and beliefs of the pain experience
• Recognizes the interconnections among thoughts, feelings, and behaviours
• Fundamental difference underlies appraisels and interpretations of situations
• Appraising the situation is defined by "I can never enjoy anything with this pain problem" vs "I can still enjoy many things in my life, despite the pain" can determine the degree of comfort
• Beliefs affect emotions and behaviour
• Patient beliefs impact presentation to health-care providers
• How others react to patient is based on their presentation of the patient is by encouraging/discouraging complaints
• Pain-related cognitions develop as a result of the patient's history, cultural backgrounds, and social experiences
• Catastrophic thinking about pain is a risk factor for poor prognosis and can lead to chronic pain
• Psychological interventions incorporate techniques and procedures to influence affective, behavioural, cognitive, and sensory aspects of the pain experience

Psychological Assessment of Pain

• Health psychologists assess patients experiencing pain, especially chronic pain
• Assessments evaluate psychological functioning (psychological co-morbidities, coping efforts) with detailed clinical interviews and tests
• Psychological assessment relies on biopsychosocial formulations of pain experience
• Focuses on the person, psychological/problem history, co-morbidities, coping styles, pain experience, functional analysis of pain behaviour and the impact on quality of lift
• Psychological assessment involves personal history and assessment of co-morbidities and coping styles
• Coping strategies can improve outcomes + passive strategies
• Historical information includes past treatments, substance use, and vocational & social history
• Historical info assists in client's goal and expectation related to current treatment

Dimensions of the Pain Experience

• Psychologists measure self-reported pain intensity using varied scales
• Simple tool = 0-10 scale; verbal selects a word describing pain
• Pain has affective, sensory, and evaluative components
• McGill Pain Questionnaire (MPQ) is a tool of words capturing dimensions of the experience
• MPQ consists of descriptors along with a human body markable for spatial distribution of the pain
• Overall rating of intensity is based on a 1-5 scale
• Descriptors of pain include temporal properties
• Pain dimensions: 1) sensory (linked) 2) affective (linked) and 3) evaluative (evaluates unbearable annoyance
• McGill Pain Questionnaire shows accurate classification of pain syndromes:
  • 91% accurate classification of patient diagnosis
  • 77% accurate (8 different types)
• Cognitions are evaluated as well, such as how patients engage is catastrophic thinking
• This involves cognitive appraisal with situations being viewed as beyond an individual's ability to cope
• Psychologists measure behavioral tendencies, such as the tendency to avoid pain.
• Pain catastrophizing and avoidance predict poor rehabilitation outcomes

Pain Behaviour: Antecedents, Consequences, and Determinants

• Psychologists asssess pain behaviour - grimacing/discussion
• Pain behaviour include asking for assistance from significant others
• Standardized observational approaches include communicatively challenged people
• Antecedents include what precedes pain behaviour being examined (stressful situations)
• A person is often given more attention + help = encouragement (operant model)
• Social support can improve experiences among pain patients (amount matters)
• Other influences = work environment.compensation system
• Poor rehab occurs when veracity questioned

Effects of Pain on Quality of Life

• Chronic pain affects many spheres of human functioning
  • mood, psychological functioning
  • social relationships
  • intimate relationships (irritability/discomfort interfering with sexual activity)
  • vocational/workplace productivity and safety
  • economic circumstances,
  • substance abuse
• Evaluation is assessed to make recommendations for addressing concerning areas
• Biopsychosocial formulations are accepted and lead to therapy Cognitive behavioural therapy (CBT) is popular
• CBT perspectives understand the relationships (cognition/schemas/behaviour/interpersonal factors)

Pain in Persons with Limited Ability to Communicate

• Systematic pain assessment can be performed on cases of severe motor and cognitive impairments like cerebral palsy
• Tracy Latimer
• People supported Mr. Latimer's decision, others were concerned about vulnerable persons
• Psych Patrick McGrath made arguments against debate of the right to lie vs die, the main issue was right of people of comm impair

Psychological Treatments for Chronic Pain

• Chronic pain is complementary to medical and physical modalities
• Interdisciplinary approach (includes physicians, therapists etc)
• This includes psychological consequences such as depression and anxiety
• The approach is CBT (cognitive techniques, challenging automatic thoughts) including "I am useless because I have pain"
• Behavioural is pacing, skill development, and relaxation/biofeedback
• Cognitive restructuring challenges negative thoughts + addressing underlying
• Behavioural is relaxation + behavioural activation

CBT in Practice

• learning to adapt to pain through CBT
• Negative catastrophic thoughts about pain causes a self-fulfilling prophecy
• Experimentation can improve and give value to the CBT process
• Gradual activeness + change is vital for proper cognitive improvement
• Relaxation + mental association is key for the patients

Psychological Management of Acute Pain

• Clinical health psychologists help management of acute pain
• Interventions for post surgical pain can improve distress
• These are used for burns/dental pain/ non-surgical medical procedures
• These include relaxation like progressive muscle + imagery
• It also includes hypnosis + distractions and self statements for better positive cognitive procedures
• Psycho-education promotes information about the procedure + how to provide realistic expectations that reduce negative impacts
• Technology promotes immersion within virtual reality
• Used as distraction strategy with good results