Chapter 10: Pain and its management.
- Most middle aged people or older people experience chronic pain on a daily basis.
No introduction to pain would be complete without consideration of its prevalence
and cost. Many people who suffer from chronic feel have more than one chronic
health conditions and use over the counter pain killers, tranquilizers and sleeping
pills at rates 2 to 4 times higher than those without chronic pain. Chronic pain also
interferes with peoples normal activity, which cannot carry out in response to pain.
It also leads to anxiety and depression.
-Significance of Pain: Pain hurts so it overwhelms other needs, but its significance
goes beyond this disruption. Pain is significant for managing daily activities. Pain is
critical to provide us feedback so we can do something about and see treatment, if
there was no pain we would know there was something wrong and wont go to seek
treatment for it. Minor pains happen to us all the time which we fix unconsciously
such as rolling over sleep, shifting our posture etc. However, the relationship
between pain and illness is weak, in example of a cancerous lump which causes no
pain until in its last stages. Pain is what patients fear most in a treatment and it is
the reason for requests for euthanasia.
-Why is pain difficult to study? : Pain is a personal, subjective behavior, influenced
by cultural learning, the meaning of situation and the attention paid to the situation
and other psychological variables. Pain is a mysterious part of treatment as the
degree to which its felt and how incapacitating it is depend largely on how it
interpreted. Example during world war 2, comparison between wounded soldiers
and wounded civilians, soldiers asked for less morphine than civilians as for soldiers
pain meant that he was alive and will be sent back home where as for a civilian pain
meant unwellness and interruption of valued activities. Cases reported in sports
games where when athletes are hurt remain oblivious to pain b/c of sympathetic
arousal to diminish pain sensitivity during sports. Pain has a cultural componenet as
well, some people have a different of reacting to pain and expression of pain as
-Measuring Pain: Difficulty in treatment of pain is that people have to describe it as
it cant be seen compared to a lump of cancer or broken bone which can be seen in
X-ray. One solution to measuring pain is the verbal vocabulary that people use to
describe pain, such as throbbing pain, shooting pain or dull ache. Some researchers
developed pain questionnaires like McGill Pain Questionnaire, Pain catastrophizing
scale etc. Pain Behaviours are another measure of pain, four types of pain behaviors
identified 1) facial and audible expression of distress 2) distortions in posture or
gait 3) negative affect 4) avoidance of activity. Pain behaviours can asses how
disrupted ones life is beacuase of the pain.
-Physiology o Pain: Pain is a protective mechanism that brings into ones awareness
of tissue damage. Pain responses lie crying and fear and important in its diagnosis and treatment. 3 types of pain perceptions: 1) nociception results from mechanical
damage to the tissue of the body 2) thermal damage: experience of pain due to
temperature 3) polymodal nociception: pain that triggers chemical reactions from
tissue damage. Nociceptors (peripheral nervers) first sense pain and release
chemical messengers which are conducted down spinal cord to the thalamas,
reticular formation and into celebral cortex which identify site of injury and sed
messages back down to spinal column which help block pain.
-Two peripheral nerve fibres: A-delta fibres are small and myelinated that transmit
sharp pain and determine sensory aspects of pain where as C fibres are non
myelinated and transmit dull aching pain and influence motivational and affective
elements of pain. Peripheral fibres enter the spinal column at the dorsal horn. Both
fibres project into different brain areas.
- Therioes of Pain: Previously it was believed that amount of pain experienced
was directly proportional to amount of tissue damage but GATE CONTORL
THEORY challenged this by proposing that psychological factors play an
important role in experiencing pain. Acc. To gate control theory, there is
neural pain gate which modulates the pain signals to the brain and which can
occur at the spinal column dorsal horn by A-delta fibres which are involved
in closing the gate. Signals descending from the brain can modulate pain thru
a central trigger system, of large diameter conducting fibres that activate
cognitive processes which in turn then alter the pain gate thru descending
fibres. Brain could now be seen as selecting, filtering and modulating signals
rather than simply receiving them and dorsal horns as stations that either
amplify or inhibit pain. Pain sensitivity, intensity and duration all interact to
influence pain and unpleasantness and related emotions through a central
network of pathway in the limbic structures and thalamus directs inputs
cortex and also carries background input with pain which give the strong
emotions associated with pain! The whole point of this theory is that pain is
different under different circumstance and can be modulated by the brain
and that its also a psychological process!
- Gate control theory misses out Phantom limb pain where a person with an
amputated limb experiences pain in the limb, how does that limb send
signals to the brain to experience pain? This is explained by the neuromatrix
- The neuromatrix theory: Acc to this theory, there is a network of neurons that
extend throughout the areas of the brain to create the felt representation of a
unified physical self, called body-self neuromatrix. Neuromatrix is genetically
determined but also by sensory inputs or experience. Each pain a person
experiences, neuromatrix generates nerve impulses which are continuously
and cyclically processed into a characteristic pattern called its
neurosignature! Each pain has its own neurosignature with a number of
sensory, cognitive and emotional factors that are unique to it and thus in a
phantom limb pain, it is this neurosignature and NOT the sensory inputs that
create the pain.- Neurochemical Bases of Pain and Its Inhibition: The brain can control the
amount of pain a person experiences by send messages to block the
transmission of pain. Study when stimulating a part of a rats brain, it
produced so much analgesia that the rat experienced no pain during
- Opioids like heroine and morphine are drugs that help control pain, they can
be manufactured in specific parts of the brain, glands and project on sites
with which have receptors for them.
- 3 types of endogenous opioid peptides:
- 1) beta-endorphins, produce peptides that project on to limbic system and
- 2) Proenkephalin, peptides that have widespread neuronal, endocrine and
- 3) Prodynorphins: found in the gut, the posterior pituitary and brain.
- Each of these have different receptors, potencies and pharmacological
- These endogenous opioid peptides are pain suppressors of the body and can
be effective in response to stress, and reduce pain called stress-induced
- Since they are present in the pituitary gland, hypothalamus further indicates
their role in stress. Also known to have a role in immune function.
- What a