Pain Lecture Flashcards
What is Pain
IASP
Pain is an unpleasant sensory and emotional EXPERIENCE associated with actual or potential tissue damage
What are the different kinds of pain
Acute
Chronic
Describe acute vs chronic pain
Acute pain = Provoked by a specific disease or injury, serves a useful biologic purpose, is associated with skeletal muscle spasm and sympathetic nervous system activation, and is self-limited.
Chronic pain= in contrast may be considered a disease state. It is pain that outlasts the normal time of healing if associated with a disease or injury. Chronic pain may arise from psychological states, serves no biologic purpose, and has no recognisable end-point
What is the impact of pain on the NHS as described by NHS England 2016
About 28 million people in the UK suffer from chronic pain, with lower back pain being the most prevalent equating to between 1/2 and 1/3rd of the population
Why was the CMO report in 2008 important
Chronic pain was a focus of the Chief Medical Officer’s Annual Report 2008. This was a landmark publication in the field of chronic pain, being the first national government report to look at the issue and make recommendations for improving the situation. About 15% with chronic pain say it is so bad they want to die
What is the financial implication of chronic pain in the UK according to GREY et al 2000 (2000 was a GREY year because of the eclipse)
People with chronic pain are 5* more likely to see their GP than people without, spending about 500 million on prescriptions, and the cost can go as high as £12 billion for lower back pain
What are the three main theories of pain
Early pain theories
Gate control theory of pain
Neuromatrix theory of pain
What are the early theories of pain:
Pain as a sensation
Early theories of pain described pain as an automatic response to an external factor. Most early theories were based on the assumptions that pain was related to a form of punishment. The word “pain” itself is derived from the Latin word “poena” meaning fine, penalty, or punishment.
Specificity theory - von Frey 1895 - stimulus= response. There are specific receptors transmitting pain, warmth and touch and each is sensitive to specific stimulation. This was similar to Descartes who described that the link between pain and the brain was automatic
Pattern theory- 1920. Pain related to the amount of stimulation i.e. relative to the amount of stimulus
What are the limitations
No role of personality or psychosocial factors
Assumes that as humans we are rigid who just respond. Rather than contribute
Could not account for neuropathic pain.
Paul Beecher 1956 - WW2 - Civilians needed more meds
Also does not account for phantom limb pain by amputees
All these suggest variations in individuals and this supported a role of psychology
Gate control Theory: Pain as a perception/experience
1965 Melzack and Wall
Pain signals are not free to reach the brain as soon as they are generated at the injured tissues or sites. They need to encounter certain ‘neurological gates’ at the spinal cord level and these gates determine whether the pain signals should reach the brain or not.
In other words, pain is perceived when the gate gives way to the pain signals and it is less intense or not at all perceived when the gate closes for the signals to pass through. If the gates are more open, then more pain
messages pass through to the brain and you are likely to experience a high level of pain. If the gates are more closed, then fewer messages get through and you are likely to experience less pain.
This theory gives the explanation for why someone finds relief by rubbing or massaging an injured or a painful area.
It accounts for individual variability, pain is a perception and an experience rather than a sensation. This brings the role of the individual into the degree of pain felt.
It also suggests that there are many factors which can influence pain perception, like your brain (With your mood emotion and experience so things like stress and tension can make the gate open more, but relaxation keeps it closed), small and large fibres, as well as physiological stimuli
Limitation of GCT
Although it provides a good basis for incorporation of psychological factors, this ‘gate’ is yet to be found
In addition, although it attempts to integrate the mind and the body, it still suggests that these are separate processes and distinct, rather than acting together
Neuromatrix theory
2001
Pain is generated by a neural network structure in the brain which can generate pain in the absence of sensory stimulation. It accounts for phantom limb pain and the role of things like affect and anxiety. In phantom limb pain, there is a difference between what you see and what you feel. BAM. Limitation doesn’t say how these cognitive/emotions are interlinked and CHAPMAN et al argue it is not different from other models
Other factors affecting pain perception
Role of learning - Classical and Operant conditioning
Role of affect/psychological/behavioural processes
Role of cognition
Important to note that these three processes are not distinct entities, but they act together and are interrelated
Pain Personality
In a longitudinal study of about 2300 adolescents at college, Katherine Applegate et al in 2005, evaluated whether personality traits, as assessed by the MMPI, at the time of college entry can predict the number of reported pain conditions at an approximate 30-year follow-up. None of the people studied had chronic pain at the start. Among both men and women, scores on MMPI scales measuring Hypochondriasis and Hysteria were related to the report of a higher number of chronic pain conditions after the follow-up period. As a result, this could affect the pain experience later on in life.
Role of gender and catastrophising (cognition)
Keefe et al 2000
160 adults with a diagnosis of knee OA, with roughly 72 were men and 96 women. Women had significantly higher levels of pain and physical disability and exhibited more pain behaviour during an observation session than men. In addition, once catastrophizing was entered into the analyses, the previously significant effects of gender were no longer found, so patients who are more likely to catastrophize report more pain)
