Pain Flashcards
(43 cards)
How can pain be beneficial and life destroying?
- normal pain is life saving
- excessive long lasting pain or neuropathic pain is life destroying
Pain as a condition
- if there is no treatable pathology then the pain itself becomes the pathology that needs to be treated
do we have good biomarkers of pain?
no, there is no biomarker to discern real and psychogenic pain
How many classes of analgesic drugs do we have? What are their drawbacks?
ASA type drugs that work for mild pain
- but have ceiling effect so doesn’t work for serious pain
opioid type drugs
- serious side effects such as sedation and risk of addiction
Simple and IASP definitions of pain
simple: pain is a sensory modality that signals actual or potential damage to the body - thought to be a separate somatosensory system separate from others (ex. from crude touch)
IASP: an unpleasant sensory and emotional experience associated with the actual or potential tissue damage or described in terms of such damage
Types of normal pain
fast pain –> short and stabbing –> first pain
- happens when first injured and is more localized
- more recently evolved
slow pain –> slow and burning –> second pain
- generalized aching after first pain
- older system
these have different central paths using different neurons
degrees of pain
- mild - can go to work
- moderate - stays home
- severe - stays in bed
- psychogenic –> verbal report doesn’t match behaviour –> most likely depression presenting as severe pain but not staying at home
duration of pain
acute - one month or less
chronic - more than 3 months
- chronic can be long lasting or neuropathic (not all chronic pain is neuropathic but almost all neuropathic pain is chronic)
normal vs abnormal pain
normal pain
- “nociceptive”
- there is adequate stimulus and body is responding as it should
abnormal pain
- “neuropathic”
- absent or inadequate stimulus for the pain response
- CNS disorder - pain system is reporting pain when there is no cause
function of normal pain
from the bio physiological perspective - it protects the integrity of the body
- removes you from damage (sharp, stabbing pain) to remove you from the dangerous area
- it immobilizes you for repair (slow and burning) so you can heal
- helps you to get help from a doctor
is normal pain always active?
yes - always active at a low level
- it is what makes you shift your body weight when you are awake and sleeping
- unconscious levels of nociceptive pain
congenital pain insensitivity
- individuals who feel no pain
- often burn themselves, bite off tongue, don’t notice broken bones or ruptured appendices, poke out their eyes and pull teeth out as infants, don’t cough
- also have impairments in the low levels of nociceptive pain and develop orthopaedic problems because they don’t move
3 psychological dimensions of pain
- pain is regularly associated with a motivational state that elicits stereotyped avoidance behaviour –> reflex, instructive and goal oriented behaviour
- this is unlike other sensory systems that can make you feel good or bad like vision and audition, pain can only make you feel bad - pain is variably linked to damage
- pain may be present without damage ex. neuropathic pain, trigeminal neuralgia, phantom limb pain
- damage can be present without pain –> pain is suppressed during hypnosis, placebo, fight or flight, and sex
- this suggests that there is a pain override system - excessive or prolonged nociceptive pain can become neuropathic
- can be due to nerve damage but also the learning-like behaviour of pain that can spread to other parts where nerves are not damaged
- the system can be made hyperactive by damage or overuse (this is controversial)
uncontrolled nociceptive pain: onset, cause, duration, gender, prevalence, treatment
onset: often Middle Ages of later
cause - often disease of ageing ex. inflammation of the joints leads to arthititis
duration - indefinite
gender - more in women than men
prevalence - 1/3 of the population in canada
treatment - usually ASA type drugs, usually not opioids
neuropathic pain
- caused by malfunction of the nervous system due to pain damage or nerve damage
- pain without an appropriate stimulus
- it has no function –> CNS disorder
uncontrolled neuropathic pain terms - allodynia and hyperalgesia
allodenya: touch is painful
hyperalgesia: mild pain becomes severe
- neuralgias (ex. trigeminal neuralgia), causalgias, phantom limb pain
uncontrolled neuropathic pain: onset, cause, duration, gender, prevalence, treatment
onset: any time but often middle or later age
causes: nerve damage, excessive or prolonged nociceptive pain
duration: indefinite
gender: seen equally in men than women
prevalence: unknown - 12-18% of chronic pain in Canada which is partly neuropathic pain
treatment: treated with anti seizure drugs because they opposed hyperactivity of the CNS –> thus there is a hyperactivity component to neuropathic pain
why can neuropathic pain be considered a model for CNS disorders
- disorders where a super-normal pain occurs in presence of a normal stimulus
- anxiety disorders: high anxiety when there is no significant cause
- depression: severe sadness with no adequate cause
- mania
how does chronic pain affect quality of life and comorbidities?
- chronic pain can be nociceptive or neuropathic and both are serious
- it is found in 30% of the population
- comorbidities: depression, anxiety, poor sleep, lack of energy, inability to work, substance use
- quality of life is low - suicide rate is 2x normal rate, and about 10% of suicides occur in chronic pain patients
Steps of sensation to the CNS
- sensory/primary afferent neurons encounter a stimulus
- stimulus energy is transducer to a generator potential
- in pain it is by the same cell, in other sensory systems it can be by a separate receptor cell
- the generator potential is a graded potential –> spreads by decremental conduction (like an ESPS) - the generator potential produces an AP in primary afferent neurons
- if it is strong enough it will trigger the opening of VGSC (AP) in primary afferents
- AP spreads non-decrementally towards the CNS
- whole primary neuron acts like an axon - primary afferent synaptically excites a secondary ascending neuron in the CNS
- these trigger local reflexes and send signals to the brain
- in the spinal nerve the synapse is often in the dorsal horn of the spinal grey matter - tertiary and higher order neurons are activated that may provide conscious sensations
strict and general definitions of sensory neurons
strict: primary sensory neuron
general: first few neurons in a sensory system (ex. neurons in the cortex that respond to touch)
what types of primary neurons are there
bipolar
- in the ear, eye, nose
- has one axon and one dendrite
- has cilia that are sensitive to physical stimuli that are on the dendrites
pseudounipolar
- skin
- has one axon that splits, one side travels into PNS and one to CNS
what do skin/cutaneous senses include? what is the stimulus energy?
fine touch, crude touch, hot, cold, vibration, pain
- the stimulus energy for pain are these sense when they are intense - all potentially causing tissue damage
where does pain originate?
deep tissue (muscle and viscera) and the skin (cutaneous)
