Pain & Pain Management

What is pain?
1. "An unpleasant sensory and emotional experience, associated with actual or potential tissue damage, or described in terms such as damage."
  1. Pain is a subjective experience rather than just a sensation in humans
    1. Pain protects
Types of Pain
1. Acute Pain
  1. A normal and time limited response to trauma or other noxious experience, including pain related to medical procedures and acute medical conditions (eg. Shingles)
2. Recurrent pain
  1. Stems from benign causes and is characterised by intense episodes of pain interspersed with no pain (eg. Migraine)
3. Sub Acute Phase
  1. Transition from acute to chronic pain
    1. The time from tissue healing (1-2 months) to the 6 month point currently define the presence of chronic pain.
    2. Opportunity to prevent transition
    3. Presumably changes are occurring in the nervous system during this time
4. Chronic (Non-Cancer) Pain
  1. Constant daily pain for a period of 3 months or more
  2. Pain is present all the time, though of varying intensity, stemming from benign causes. Ensures beyond the time of normal healing eg. low back pain.
  3. Chronic progressive pain that increases in intensity as the concomitant medical condition worsens eg. pain associated with rheumatoid arthritis and cancer.
5. Cancer-related Pain
  1. Evidence that cancer pain is under-treated
6. Categorisation Based on Underlying Pathophsyiology
  1. Nociceptive Pain
    1. Pain that arises from actual or threatened damage to non-neural tissue
  2. Nociceptive inflammatory Pain
    1. Part of normal inflammatory response to injury
  3. Neuropathic Pain
    1. May be caused by a lesion or dysfunction in the peripheral and/or central nervous system. Frequently peristent and frequently involves spontaneous pain in absence of an identifiable stimulus.
Experience of Pain
1. Pain is different from other senses as it is typically accompanied by an emotional component
2. The meaning of pain substantially determines how it is perceived
3. Pain is heavily influenced by the context in which it is experienced.
4. Pain has a substantial cultural component.
5. Themes of those who have experienced Chronic Pain
  1. Stigma - considered 'psychologically defective'
  2. Loss of control of one's life; struggling with everyday life
  3. Frustration with health care professionals
  4. Lack of effective treatments
  5. Perceived lack of creditability - not being believed
  6. End of happiness; depression
  7. Erosion of relationships
  8. Disruption of careers; becoming improverished
  9. Frustration with compensation sysetem
  10. Sleep problems
  11. Perceived lack of empathy
Early Understanding of Pain
1. Tissue damage causes the sensation of pain
2. Psychology involved as a consequence of pain without a casual influence
3. Pain sensation has a single cause
4. Pain considered either psychogenic or organic
Bio-Psycho-Social Model of Pain
1. Physical
2. Psychological
3. Environmental (social)
4. Need to assess all components
  1. Interdisciplinary approach
Physiology of Pain - Gate Theory
1. Neural Mechanisms
  1. A-delta fibres are associated with the conduct of fast, sharp, well localised pain or pain experienced quickly. These fibres are small myelinated fibres which facilitate fast transmission of information.
  2. A-delta fibres enter the spinal column at the dorsal horn and then project to particular areas of the thalamus and the sensory areas of the cerebral cortex –hence the provision of localised pain information.
  3. C-fibres are small nerve fibres that are un- myelinated and conduct slow, aching, burning, long lasting and poorly localised pain.
  4. The C-fibres project to different areas of the brain, including thalamic, limbic, and cortical areas. These areas are involved in mood, emotion and motivation and so these aspects of pain are related more to C-fibre activation.
  5. A-beta fibres – large diameter fibres which have been proposed to send “non-pain” messages.
  6. Gate Theory
    1. Central assumption of the Gate Theory is that different parts of the CNS are involved in the pain experience.
    2. They affect the operation of a gate-like mechanism in the dorsal horns of the spinal column that controls the flow of pain stimulation in the brain.
    3. Pain sensations are modified as they are conducted to the brain up the spinal column, and they are also influenced by messages coming down from the brain that interpret the experience.
    4. When A-beta fibres fire they act to keep the gate of the brain closed. WhenA-delta and C-fibres fire above a certain threshold, the gate opens and pain messages are sent to the brain.
      1. Messages coming down from the brain can also open or close the gate.
Recent Understanding of Chronic Pain
1. In inflammatory and neuropathic pain and pain caused by abnormal central processing, amplification of excitability of neurons within the CNS may occur.
  1. Called Central Sensitisation
    1. It's in greater pain experience
Neuro-chemical Basis of Pain
1. Bradykinin and prostaglandins are substances released by tissue damage.
2. Bradykinin is a blood-borne neuropeptide that is cleaved away from a large inert molecule by enzymes a fraction of a second following injury.
3. Bradykinin and prostaglandins stimulate pain associated neurons and are considered to be major producers of pain.
4. Glutamate and Substance P are neurotransmitters that act in the spinal cord to increase neural firings related to pain.
5. Substance P is secreted by pain fibres and crosses the synapse to T cells, triggering their firing.
6. Opiates affect the brain - there must be naturally occurring opiates in the body
  1. Led to discovery of endorphins (enkaphalins and dynorphin) which inhibit pain fibres releasing Substance P.
    1. Endorphin means “the morphine within” and was given this name as it has properties similar to those of heroin and morphine. It is a powerful pain killer and mood elevator.
      1. Naloxone, an opiate antagonist appears to reduce pain relieving ability of body through endogenous opioids.
Psychosocial Aspects of Pain
1. Fordyce identified 4 aspects of Pain
  1. Nociception
    1. potential tissue damaging energy impinging on specialised nerve endings of a-delta and C-fibres. i.e., input to pain receptive nerve endings.
  2. Pain
    1. perceived nociceptive input to the nervous system.
  3. Suffering
    1. negative affective (emotional) response generated in higher nervous centres by pain and other situations, e.g., loss.
  4. Pain Behaviour
    1. All forms of behaviour generated by the individual commonly understood to reflect the presence of nociception.
2. Chronic Pain
  1. deep psychological consequences
    1. Persistent attempts to react and adapt to pain frequently result in emotional problems such as depression, anxiety and fear
      1. Affects cognition – e.g., concentration and memory;
        Affects interpersonal relationships.
Learning Pain Behaviours
1. Pain behaviours may be reinforced, i.e., the likelihood of their occurrence will increase if they are rewarded. E.g., relief from pain when ask for medication (“medication on demand”; worker’s compensation for pain).
  1. Implication for development of inappropriate use of pain relieving mediation, following acute pain experience (e.g., surgery).
    1. Pain behaviours may be influenced by avoidance learning. E.g., if it hurts to walk 500m next time you only walk 400 m to avoid pain. Causes reduction in activities engaged in.
Goals of Pain Managment
1. Improve understanding of persistent pain
2. Improve function despite ongoing pain
3. Modify perceptions of pain and suffering
4. Provide coping skills and strategies
5. Promote self-management
6. Reduce or modify future use of health care services
Improving Coping with Chronic Pain
1. Behaviour therapy
  1. A managed approach to behavioural change using the basic principles of operant conditioning (learning principles).
    1. Increasing rewards for well behaviour and teaching increasing self-rewards;
    2. Decrease rewards for pain behaviour but without lack of sympathy;
    3. Reduce avoidance behaviour – plan for a length of time for an activity and plan achievable but not to modest goals;
    4. Increase general fitness – can be positively reinforcing.
2. Cognitive behavioural therapy
  1. Primary focus on changing cognitive activity to achieve changes in behaviour, thought and emotion.
    1. Patients are encouraged to develop insight into self- defeating patterns they have fallen into;
    2. Develop ways of challenging these;
    3. Increase self-efficacy;
    4. Problem solving in relation to social and relationship changes.
3. Biofeedback and relaxation – learn new skills.
Setting Goals
1. Realistic
2. Achievable
3. Relevant
4. Specific or concrete
5. Important motivation
  1. Long-term/Short-term
Coping with Acute Pain
1. Pain can be accompanied by anxiety, stress, and physical tension, which can exacerbate and/or prolong the acute pain episode
2. A number of psychological strategies can be used to help patients cope with these, as well as thoughts and emotions that may increase physiological arousal and reduce the patients’ sense of control
Pain Information
1. This helps patients understand what is “normal” under their particular circumstances and can reduce anxiety.
  1. Patients should be given as much information as possible about nature of pain they might expect from a procedure or trauma.
Distraction
1. Tell patients that although strong, pain signals are one of many possible sensations that they may notice at any given moment, and that actively distracting from the signal may provide some relief;
  1. Ask patients to gently guide their attention to another stimulus, such as television, music, reading, simple puzzles, or conversations with supportive family/friends;
    1. Encourage patients to imagine a preferred place or situation where they feel calm and relaxed, in as much detail as possible, pulling in all of their senses, including sights, sounds, smells, touch, and taste (Guided imagery).
Cognitive Approaches
1. Discuss the role of thoughts on patients’ sense of coping with pain, and their relationship to physiological arousal
  1. Encourage patients to generate and practice positive self-talk that emphasizes their ability to cope with the pain
    1. Patients should also be reassured that the pain episode is of limited duration, and that they can remind themselves that it will pass.
Appropriate Use of Analgesia
1. For patients that do not experience adequate analgesia, can lead to chronic pain
  1. Important to provide effective pharmacological analgesia as soon as possible during, or even before, an acute pain episode
    1. An emphasis should be placed on taking medications as scheduled, not only when pain emerges, and patients’ concerns regarding side effects, including any addiction potential, should be addressed

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Pain & Pain Management

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